White clover is a weed in apple orchards that competes with the crop; also, flowers of this weed are unwanted attractants of honey bees at times when insecticides, which are harmful to these pollinators, are being applied. In 1997 and 1998, white clover flower head and plant control by clopyralid alone and with 2,4-D and apple tolerance to these herbicides were determined. Treatments consisted of clopyralid at 0.10 and 0.21 kg ae/ha, 2,4-D at 1.1 kg ae/ha, and 2,4-D at 1.1 kg ae/ha plus 0.03 or 0.05 kg ae/ha clopyralid, which were applied 2 wk before full apple bloom and 2 wk after full apple bloom, and a nontreated check. No crop injury occurred with any treatment. All herbicide treatments provided some white clover control and flower head suppression. No differences in white clover bloom reduction were observed through May among treatments containing clopyralid. As summer progressed, the effect of clopyralid rate became more apparent. Clopyralid at 0.21, regardless of application time, provided 99% vegetative control and 100% flower head reduction through July. Clopyralid plus 2,4-D controlled white clover better than 2,4-D alone. However, vegetative control and flower head reduction with clopyralid at reduced rates (0.03 or 0.05 kg ae/ha) plus 2,4-D were not acceptable (76% or less and 78% or less, respectively). Thus, clopyralid at 0.10 and 0.21 kg ae/ha will be necessary for acceptable white clover vegetation control and flower head reduction.

Nomenclature: 2,4-D; clopyralid; white clover, Trifolium repens L. #³ TRFRE; apple, Malus domestica Borkh.; honey bees, Apis mellifera L.

Additional index words: Orchard floor management, TRFRE, weed control.

Abbreviations: 2WAFB, 2 wk after full apple bloom; 2WBFB, 2 wk before full apple bloom.

The limited window of opportunity for glyphosate postemergence (POST) over-the-top applications in glyphosate-resistant cotton poses a problem for growers where a midseason salvage weed control remedy is necessary. The objectives of these experiments were to compare glyphosate and MSMA for midseason weed control and their subsequent effect on cotton fruiting characteristics and yield. Glyphosate at 0.85 kg ai/ha was more effective than MSMA at 1.7 kg ai/ha for POST control of sicklepod, redweed, and pitted morningglory. Single glyphosate treatments applied at the 8-, 10-, or 12-leaf cotton stage resulted in less-effective weed control than when applied at the four-leaf cotton stage. Glyphosate applied at the four-leaf cotton stage followed by a sequential POST-directed application at 6-, 8-, 10-, or 12-leaf cotton stage increased season-long weed control and yield compared with a single application at the four-leaf stage. Both glyphosate and MSMA controlled Florida beggarweed, regardless of POST application timing. Generally, cotton was more tolerant to glyphosate than MSMA when applied over-the-top. Glyphosate applied POST over-the-top to weed-free 12-leaf cotton resulted in a 19 and 14% yield loss compared with the weed-free nontreated cotton in 1997 and 1999. MSMA reduced yield by 58 and 36% in 1997 and 1999, respectively. Glyphosate did not affect weed-free cotton fruit development or yield when applied over-the-top to four-leaf cotton or when a POST-directed application was followed at the 12-leaf stage.

Nomenclature: Glyphosate; MSMA; Florida beggarweed, Desmodium tortuosum (Sw.) DC. #^3, DEDTO; pitted morningglory, Ipomoea lacunosa L. # IPOLA; redweed, Melochia corchorifolia L. # MEOCO; sicklepod, Senna obtusifolia L. #³ SENOB; cotton, Gossypium hirsutum L.

Additional index words: Application timing, cotton boll retention, salvage weed control.

Abbreviations: POST, postemergence; POST-directed, postemergence-directed; PPI, preplant incorporated; PRE, preemergence.

Studies were conducted from 2001 through 2003 to determine the extent of resistance to acetolactate synthase (ALS) inhibitors and glyphosate in Ohio horseweed biotypes. The response of 66 horseweed biotypes to cloransulam-methyl and glyphosate was determined in the greenhouse. Application of 0.07 kg ai cloransulam/ha reduced plant biomass by less than 60% for 38 of the 66 biotypes. Application of 3.4 kg ae glyphosate/ha reduced biomass by at least 80% for the 51 biotypes collected in 2001, but biomass was similar to that of nontreated plants for 11 of the 15 populations collected in 2002. A dose–response study was conducted with selected biotypes, and a nonlinear, logistic dose–response curve was fit to the data to calculate the herbicide dose required to reduce fresh weight 50% (GR₅₀). On the basis of GR₅₀ values, the resistance ratio (R/S) for two ALS-resistant biotypes was 34 and 943 for chlorimuron-ethyl and 32 and 168 for cloransulam, respectively. The R/S ratio for two glyphosate-resistant biotypes was 33 and 39. Results of these studies indicate that, in 2002, ALS-resistant horseweed was widespread throughout Ohio, whereas resistance to glyphosate occurred primarily in several counties in southwestern Ohio.

Nomenclature: Chlorimuron-ethyl; cloransulam-methyl; glyphosate; horseweed, Conyza canadensis (L.) Cronq. #³ ERICA.

Additional index words: Acetolactate synthase, herbicide resistance.

Abbreviations: ALS, acetolactate synthase; GR₅₀, herbicide dose required to reduce fresh weight 50%; R/S, resistance ratio.

Perennial pepperweed, found throughout the western United States, reduces biodiversity and causes economic losses in the form of control costs as well as decreased quantity and quality of agricultural yields. The future stream of net benefits of weed management and the future point in time at which they will have accumulated enough to equal total management costs were estimated under different land-use and expansion rate scenarios. Benefits and costs were calculated in present value terms by applying a rate of discount to future values. On land used solely for grazing, the total economic returns from management did not equal total costs until 15 yr after initial treatment. However, on land used for grazing plus hay harvest, cumulative benefits equaled and began to exceed cumulative costs after 4 to 5 yr. The costs and benefits of management efforts were also estimated for a landowner, who controls an adjacent infestation before it spreads. This landowner benefited economically from weed management in as little as 5 to 6 yr, highlighting the importance of cooperative efforts to control nearby weed infestations.

Nomenclature: Perennial pepperweed, Lepidium latifolium L. #³ LEPLA.

Additional index words: Economic externality, economic impacts, economic threshold, GIS, GPS, invasive species, invasive weeds, nonnative species.

Abbreviations: AUM, animal unit months; GIS, Geographic Information System; GPS, Global Positioning System.

CGA-362622 has been registered for postemergence (POST) over-the-top or POST-directed application in cotton. Research was conducted during 1998 in Texas to determine potential cotton phytotoxicity after POST application of CGA-362622 alone and with the insecticides acephate, dicrotophos, azinphos methyl, oxamyl, thiamethoxam, dimethoate, and malathion and to determine the response of four cotton cultivars to CGA-362622 applied alone. CGA-362622 applied with malathion injured cotton more than either pesticide applied alone, and yield was reduced in one of four locations when the pesticides were applied in mixture compared with nontreated cotton. Pyrithiobac or CGA-362622 mixed with malathion injured cotton similarly. The other insecticides tank mixed with CGA-362622 generally did not adversely affect cotton. The cotton cultivars ‘Delta and Pine Land 50’, ‘Paymaster 1220’, ‘Paymaster 1220RR’, and ‘Stoneville 474’ responded similarly to CGA-362622 applied alone or with insecticides.

Nomenclature: Acephate, O,S-dimethyl acetyl-phosphoramidothiate; azinphos methyl, {O,O-dimethyl S-[4-oxo-1,2,3-benzotriazin-3(4H)-yl methyl]phosphorodithioate}; CGA-362622; dicrotophos, dimethyl phosphate of 3-hydroxy-N,N-dimethyl-cis-crotonamide; dimethoate, [O,O-dimethyl S-(N-methylcarbamoylmethyl) phosporodithioate]; malathion, O,O-dimethyl phosphorodithiate of diethyl mercaptosuccinate; oxamyl, {methyl-N′N′-dimethyl-N-[(methyl carbamoxyl)oxy]-1-thiooxamimidate}; pyrithiobac; thiamethoxam, {4H-1,3,5-oxadiazin-4-imine, 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro}; cotton, Gossypium hirsutum L. ‘Delta and Pine Land 50’, ‘Paymaster 1220’, ‘Paymaster 1220RR’, ‘Stoneville 474’.

Additional index words: Cotton injury, pesticide interaction, sulfonylurea herbicide.

Abbreviations: ALS, acetolactate synthase; DAP, days after planting; DAT, days after treatment; OT, over-the-top; POST, postemergence; PRE, preemergence.

Turf managers combine ethephon with trinexapac-ethyl (TE) on bentgrass greens to suppress annual bluegrass, inhibit turf growth, and enhance turf quality; however, effects of this growth regulator combination have not been reported on bermudagrass greens. Two experiments were conducted at the Clemson University Greenhouse Complex to investigate the response of ‘TifEagle’ bermudagrass to ethephon and TE. TifEagle bermudagrass plugs were placed in pots with 23-cm depths, 324-cm² total surface areas, and a soil medium of an 85:15 (v/v) sand and peat moss mix. Ethephon was applied at 0, 3.8 (EP1), and 7.6 (EP2) kg ai/ha/3 wk with TE at 0 and 0.04 kg ai/ha/ 3 wk over a 9-wk period. Initial responses of bermudagrass to ethephon included chlorotic leaves and severe thinning. Bermudagrass treated with ethephon had quality reduced as much as 33% from nontreated turf. TE enhanced turf quality 4 to 22% from 4 to 9 wk after initial treatment. TE helped mask ethephon-induced quality decline after the third application. In the presence of TE, bermudagrass clipping yield was reduced from nontreated turf by 57, 70, and 72% when ethephon was applied at 0, 3.8, and 7.6 kg/ha/3 wk. Ethephon linearly reduced root mass after 9 wk from nontreated turf by 20 and 33% at 3.8 and 7.6 kg/ha/3 wk, respectively. Compared with respective ethephon rates alone, bermudagrass treated with TE and ethephon at 0, 3.8, and 7.6 kg/ha/3 wk, averaged 28, 8, and 15% more root mass. Ethephon at 3.8 and 7.6 kg/ha/3 wk without TE reduced TifEagle bermudagrass root length 14 and 16%, respectively, compared with untreated turf. Bermudagrass treated with ethephon at 0, 3.8, and 7.6 kg/ha/3 wk with TE averaged 3, 11, and 17% higher root length compared with respective ethephon rates after 9 wk. Overall, ethephon may have negative effects on TifEagle root mass, root length, and turf quality. However, combining ethephon with TE may help reduce these deleterious effects.

Nomenclature: Ethephon, (2-chloroethyl)phosphonic acid; trinexapac-ethyl, 4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester; annual bluegrass, Poa annua L.; TifEagle bermudagrass, Cynodon dactylon × C. transvaalensis.

Additional index words: Dwarf bermudagrass, plant growth regulator, turf injury.

Abbreviations: GA, gibberellic acid; PGR, plant growth regulator; TE, trinexapac-ethyl; WAIT, weeks after initial treatment.

Field trials were conducted in 2001 at the Tobacco Research Station near Oxford, NC, and in 2002 at the Lower Coastal Plains Research Station near Kinston, NC, to determine tobacco yield, injury, and shikimic acid accumulation in response to simulated glyphosate drift. Glyphosate was applied to 12- to 13-cm-high tobacco ‘K326’ early postemergence at 0, 9, 18, 35, 70, 140, 280, 560, and 1,120 (1×) g ai/ha. Crop injury was rated 7 and 35 d after treatment (DAT) and shikimic acid accumulation in leaves at 7 DAT, tobacco yield, and leaf grade index (whole-plant index of harvest interval leaf value) were also assessed. Shikimic acid accumulation and injury symptoms increased similarly as glyphosate rate increased. Glyphosate rates of 140 g/ha (0.125 of recommended rate) or higher resulted in significant crop injury, reduced tobacco yield, and decreased leaf grade index. Shikimic acid accumulation at 7 DAT was inversely related to tobacco yield. Shikimic acid accumulation was found to be an effective diagnostic tool to determine glyphosate drift in tobacco; however, in-season data are needed to correlate shikimic acid accumulation with yield loss.

Nomenclature: Glyphosate; tobacco, Nicotiana tabacum L. ‘K326’.

Additional index words: Crop injury, herbicide assay, shikimate.

Abbreviation: DAT, days after treatment.

Field studies were established in 1999 and 2000 to evaluate Italian ryegrass, wheat, and double-crop soybean response to fall and spring postemergence applications of flucarbazone, sulfosulfuron, clodinafop, diclofop, and tralkoxydim applied alone and in combination with thifensulfuron tribenuron to winter wheat. Fall-applied herbicides caused 5% or less wheat injury. Spring-applied herbicides caused 3 to 45% wheat injury, and the greatest injury occurred with the combination of flucarbazone with thifensulfuron tribenuron in the spring of 2001. Spring-applied sulfosulfuron, tralkoxydim, diclofop, and clodinafop caused 3 to 6% and 16 to 26% wheat injury in 2000 and 2001, respectively. Herbicide injury to wheat did not reduce wheat grain yield compared with the hand-weeded treatment. Italian ryegrass competition in the nontreated plots reduced wheat yield by as much as 33% compared with herbicide-treated plots. Italian ryegrass control was 89 to 99% from clodinafop and diclofop and 78 to 97% from flucarbazone, with no differences because of application timing in either year of the study. Italian ryegrass control from sulfosulfuron and tralkoxydim was greater from the spring of 2000 applications (94 to 99%) compared with the fall of 1999 applications (65 to 88%). However, in 2001, application timing (fall vs. spring) for sulfosulfuron and tralkoxydim did not affect Italian ryegrass control. Thifensulfuron tribenuron combined with tralkoxydim reduced control of Italian ryegrass control compared with tralkoxydim alone in both years of the study. Italian ryegrass control was not reduced when thifensulfuron tribenuron was combined with sulfosulfuron, flucarbazone, diclofop, or clodinafop. Italian ryegrass was controlled effectively by the acetyl-CoA carboxylase–inhibiting herbicides diclofop, clodinafop, and tralkoxydim. However, control of Italian ryegrass with the acetolactate synthase–inhibiting herbicides flucarbazone and sulfosulfuron was inconsistent. Double-crop soybean after wheat did not have foliar symptoms or yield loss from fall- or spring-applied herbicides.

Nomenclature: Clodinafop; diclofop; flucarbazone; sulfosulfuron; thifensulfuron; tralkoxydim; tribenuron; Italian ryegrass, Lolium multiflorum Lam., Marshall #³ LOLMU; soybean, Glycine max (L.) Merr, ‘BT369CR’; wheat, Triticum aestivum L., ‘Pioneer 25R26’.

Additional index words: Application timing, herbicide carryover, tank mixtures.

Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); DAT, days after treatment; POST, postemergence.

Field studies were conducted from 1998 through 2000 to compare weed population shifts in soybean and cotton using a total glyphosate system, preemergence (PRE) herbicides followed by glyphosate, and a conventional herbicide program. In the first year of the soybean study, populations of hemp sesbania were highest for treatments of PRE herbicides followed by either glyphosate or the conventional herbicide program because of better control from the total glyphosate system. Barnyardgrass populations in the first year of the study for the nontreated plots were 0 plants/m² but increased in the third year to 61 plants/m². Flumetsulam plus metolachlor followed by glyphosate at the lower rates and the nontreated check were the only treatments in which there was an increase in barnyardgrass over the 3-yr study. Broadleaf signalgrass populations increased in the third year with 0.1 kg ai/ha flumetsulam plus 2.1 kg ai/ha metolachlor followed by 0.84 kg ae/ha glyphosate, primarily because of reduced competition from lower populations of other weeds such as hemp sesbania. Pitted morningglory populations for all treatments decreased in the third year because of good control of this species and the high level of interference from other weed species in the first 2 yr. Johnsongrass populations decreased in the third year with 0.4 kg ai/ha flumetsulam plus 1.1 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Johnsongrass populations decreased with timely glyphosate sequential applications, with 5 plants/m² in 1998 and 0 plants/m² in 2000. Yields increased from the first year to the second year, corresponding to reduced weed pressure, and yields varied from 710 to 1,420 kg/ha. Because of weed pressure, soybean yields were not different in any of the treatments, including the nontreated, although treatments changed the species present. In the cotton study, weed populations over the 3 yr decreased, with the most significant reductions from the treatments of fluometuron plus prometryn plus metolachlor followed by either pyrithiobac or glyphosate. Weeds that showed the most significant decline were barnyardgrass and hemp sesbania, whereas johnsongrass increased, with 27 plants/m² in treatments of 0.6 kg ai/ha fluometuron plus 0.3 kg ai/ha prometryn plus 0.7 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Lint cotton yields varied from 0 to 128 kg/ha. Because of the weed pressure, cotton yields were not different in any of the treatments, although treatments changed the species present. This research has shown that weed species can decrease over time with the continued use of any of these herbicide programs.

Nomenclature: Glyphosate; flumetsulam; fluometuron; metolachlor; prometryn; pyrithiobac; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #³ ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash # BRAPP; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex. A. W. Hill # SEBEX; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; cotton, Gossypium hirsutum L.; soybean, Glycine max (L.) Merr.

Additional index words: Ecological niche, population dynamics, weed succession.

Abbreviations: PRE, preemergence; POST, postemergence.

A 2-yr experiment evaluated the effect of spring soil disturbance on the periodicity of weed emergence. At four locations across the northeastern United States, emerged weeds, by species, were monitored every 2 wk in both undisturbed plots and plots tilled in the spring with a rotary cultivator. Eight weed species including large crabgrass, giant and yellow foxtail, common lambsquarters, smooth pigweed, eastern black nightshade, common ragweed, and velvetleaf occurred at three or more site-years. Spring soil disturbance either had no effect or reduced total seedling emergence compared with undisturbed soils. Total seedling emergence for large crabgrass, giant foxtail, smooth pigweed, and common ragweed were on average, 1.4 to 2.6 times less with spring soil disturbance, whereas eastern black nightshade and velvetleaf were mostly unaffected by the soil disturbance. The influence of soil disturbance on yellow foxtail and common lambsquarters emergence varied between seasons and locations. Although the total number of emerged seedlings was often affected by the soil disturbance, with the exception of yellow foxtail and common ragweed, the periodicity of emergence was similar across disturbed and undisturbed treatments.

Nomenclature: Common lambsquarters, Chenopodium album L. #³ CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; giant foxtail, Setaria faberi Herrm. # SETFA; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; smooth pigweed, Amaranthus hybridus L. # AMACH; velvetleaf, Abutilon theophrasti Medicus # ABUTH; yellow foxtail, Setaria glauca (L.) Beauv. # SETLU.

Additional index words: Integrated pest management, periodicity of weed emergence, spring soil disturbance.

Although dandelion has been recognized for some time as a common weed of perennial plant stands, recent weed surveys in western Canada indicate that dandelion has become more common in fields where annual spring crops are grown. Because little has been published on dandelion control in annual crops, a field study was conducted at two locations in southern Manitoba in 1999 and 2000 investigating the effect of spring tillage, glyphosate dosage, and application timing on dandelion control in a spring annual glyphosate-resistant canola crop. The experiments were situated in areas known to have natural infestations of dandelion. Final assessments of dandelion control were performed the spring following treatment, i.e., the next year, to provide a better indication of treatment efficacy on this perennial weed. Spring tillage alone did not significantly reduce dandelion density, as assessed the following spring, but did reduce dandelion shoot dry matter at three of the five site-years by up to 84%. Glyphosate was applied preplant, in-crop, and postharvest at dosages ranging from 450 g ae/ha in-crop to 2,700 g ae/ha postharvest. Glyphosate application after the canola crop had been harvested provided the greatest level of dandelion control, with a single postharvest application of 900 g ae/ha of glyphosate reducing dandelion density and shoot dry matter by 88 and 96%, respectively, the following spring. Applications of glyphosate either preplant or in-crop were not nearly as effective as the postharvest treatments in reducing dandelion density and shoot dry matter the following spring.

Nomenclature: Glyphosate; dandelion, Taraxacum officinale Weber ex Wiggers #³ TAROF; canola, Brassica napus L. ‘LG 3235’.

Additional index words: Dandelion control, glyphosate application timing.

A study was conducted in 2000 and 2001 to evaluate interaction of fenoxaprop with other herbicides for barnyardgrass control in rice. Changes in herbicide interaction over time were also evaluated, and herbicide combinations were ranked on the basis of compatibility. Fenoxaprop at 0.075 kg/ha plus bentazon or propanil plus molinate resulted in an additive response for barnyardgrass control at 10, 20, and 30 d after treatment (DAT); however, when the rate of fenoxaprop increased to 0.089 kg/ha, an antagonistic effect was found. Carfentrazone and halosulfuron consistently antagonized the activity of fenoxaprop at both rates on barnyardgrass. Bensulfuron at 10 and 20 DAT and triclopyr at 20 DAT were antagonistic to fenoxaprop. An increase in interaction over time was detected when fenoxaprop at 0.089 kg/ha was applied in mixture with carfentrazone at 0.04 kg/ha or halosulfuron at 0.05 kg/ha. These results indicate that propanil plus molinate and bentazon are more compatible with fenoxaprop at 0.075 kg/ha for barnyardgrass control, whereas bensulfuron, carfentrazone, halosulfuron, and triclopyr can antagonize fenoxaprop activity on barnyardgrass.

Nomenclature: Bensulfuron; bentazon; carfentrazone; fenoxaprop; halosulfuron; molinate; propanil; triclopyr; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #³ ECHCG; rice, Oryza sativa L. ‘Cocodrie’.

Additional index words: Antagonism, synergism.

Abbreviations: DAT, days after treatment; NLMIXED, nonlinear mixed procedure; POST, postemergence.

Weed-wipers may provide effective weed control while minimizing the application of herbicide to nontarget species in rangeland and pasture. To date, few herbicides are recommended for use in weed wiping systems. We assessed Canada thistle and non–Canada thistle herbage responses in two experiments in pastures, the first examining wiped glyphosate, the second comparing glyphosate with three broadleaf herbicides at cost-equivalent concentrations [on a volume to volume (v/v) dilution basis]. In both studies, wiping with a glyphosate solution (33% v/v, equivalent to a one to two dilution ratio of herbicide to water) resulted in lower Canada thistle density and biomass than check plots, with control lasting up to 2 yr. However, significant reductions in grass biomass also occurred and were associated with an increase in the abundance of weedy annual forbs. In contrast, wiping with a concentrated solution of clopyralid (2% v/v), picloram plus 2,4-D (20% v/ v), or 2,4-D plus mecoprop plus dicamba (24% v/v), resulted in similar levels of Canada thistle control but no reduction in grass biomass. Despite direct application of herbicides to tall weeds, clover species in mixed stands were injured. In grass-dominated pastures, wiping with broadleaf herbicides was superior to nonselective glyphosate because the former more effectively balanced Canada thistle control with the retention of grass production.

Nomenclature: Glyphosate; clopyralid; picloram; 2,4-D; mecoprop; dicamba; Canada thistle, Cirsium arvense L. #³ CIRAR; clover, Trifolium spp.

Additional index words: Broadleaf, herbage production, herbicide residue, legumes, weed density.

A study was conducted in 2002 and 2003 to evaluate response of seven rice cultivars to V-10029 applied at 20 and 40 g ai/ha to two- to three- or four- to five-leaf rice. Differential response of the rice cultivars to V-10029 was observed. Medium-grain ‘Earl’ was less tolerant to V-10029, as reflected by increased injury, shorter plants, and fewer plants at 7 d after late postemergence treatment and shorter plants and lower grain yield at harvest, when compared with nontreated Earl. Growth of medium-grain ‘Bengal’ was initially inhibited by V-10029; however, plant height at harvest and rice grain yield of Bengal were not affected. All long-grain cultivars exhibited tolerance to V-10029, both initially and at harvest. The results indicate that rice cultivars vary in tolerance to V-10029.

Nomenclature: V-10029, sodium 2,6-bis[(4,6-dimethoxypyrimidin-two-yl)oxy]benzoate; rice, Oryza sativa L. ‘Bengal’, ‘Cl-141’, ‘CL-161’, ‘Cocodrie’, ‘Cypress’, ‘Earl’, ‘Wells’.

Additional index word: Herbicide tolerance.

Abbreviations: ALS, acetolactate synthase; DAT, days after late postemergence treatment.

Field experiments were conducted to evaluate the influence of preemergence (PRE) herbicides metolachlor at 1,700 g ai/ha, pyrithiobac at 70 g ai/ha, or pendimethalin at 840 g ai/ha applied alone or with fluometuron at 1,300 g ai/ha and glyphosate postemergence (POST) at 840 g ai/ha on seedling diseases in glyphosate-resistant cotton. Hypocotyl disease severity both years averaged across PRE herbicide treatments was greater after glyphosate application to four-leaf cotton than cotyledon cotton. The PRE herbicide treatments, particularly those including fluometuron, increased root and hypocotyl disease ratings compared with a nontreated control, and a sequential application of glyphosate did not further increase disease severity. Greenhouse experiments using soil infested with Rhizoctonia solani confirmed findings from the field study showing that PRE herbicides can predispose cotton to greater seedling disease injury with no increased seedling disease severity associated with application of glyphosate. In the field study, glyphosate applied at cotyledon or four-leaf growth stages decreased disease severity on cotton hypocotyls both years. This inhibitory effect of glyphosate was less evident in the greenhouse study and may have been related to species of fungi present, infestation level, and differences in environmental conditions when compared with the field.

Nomenclature: Fluometuron; glyphosate; metolachlor; pendimethalin; pyrithiobac; Rhizoctonia solani; cotton, Gossypium hirsutum L.

Additional index words: Gossypium hirsutum L., ‘D&PL 5690 RR’, ‘D&PL 5415 RR’, ‘D&PL 436 RR’, herbicide–pathogen interactions, seedling diseases.

Abbreviations: EPSP, enolpyruvylshikimate phosphate; fb, followed by; PDA, potato dextrose agar; PRE, preemergence; POST, postemergence.

Herbicides are an important tool for managing weeds where prescribed fire is used for rangeland improvement. Understanding how the season of herbicide application relates to prescribed burning is important. Our objective was to determine the effect of picloram and chlorsulfuron on Dalmatian toadflax cover, density, and biomass, where these herbicides were applied in the fall before burning or in the spring before or after burning. Six herbicide treatments and an untreated check were applied in a randomized complete block design with four replications to a prescribed burn at two sites infested with Dalmatian toadflax in Montana, United States. Herbicides were applied in the fall preburn, spring preburn, and spring postburn. Site 1 was treated in 1999 and 2000, and site 2 was treated in 2000 and 2001. Cover, biomass, and density of Dalmatian toadflax were sampled in September 2000, 2001, and 2002 at site 1 and September 2001 and 2002 at site 2. At site 1, cover, biomass, and density of Dalmatian toadflax were at least 76% lower compared with the check in both spring-applied picloram treatments, whereas the fall picloram treatment had similar Dalmatian toadflax cover, biomass, and density compared with the check 3 yr after application. By 2002, chlorsulfuron reduced Dalmatian toadflax cover, biomass, and density by at least 79% compared with the check in all timings of application at site 1. At site 2, Dalmatian toadflax cover, biomass, and density were reduced by at least 86% for all picloram and chlorsulfuron treatments in 2002, 2 yr after application. Chlorsulfuron applied in the fall or the spring and picloram applied in the spring effectively suppressed Dalmatian toadflax cover, biomass, and density for up to 3 yr.

Nomenclature: Chlorsulfuron; picloram; Dalmatian toadflax, Linaria genistifolia ssp. dalmatica (L.) Maire #³ LINDA.

Additional index words: Integrated weed management, invasive weeds, noxious rangeland weeds, restoration using fire and herbicides.

Two trials were conducted to evaluate the effects of herbicide and mulch on weed management and strawberry yield. Napropamide at rates of 4.50, 6.75, or 9.00 kg ai/ha; oxyfluorfen at 0.57 kg ai/ha; and napropamide plus oxyfluorfen at 4.50 plus 0.57 kg/ha were applied pretransplant on pressed beds covered with either low-density polyethylene mulch or virtually impermeable film. There was no herbicide by mulch interaction. Mulch types had no influence on weed counts and fruit yield, whereas herbicides affected both variables. The napropamide plus oxyfluorfen treatment resulted in the highest fruit number and weight, increasing yield by 20% with respect to the nontreated control. This herbicide combination provided the best weed suppression.

Nomenclature: Napropamide; oxyfluorfen; strawberry, Fragaria × ananassa Duch.

Additional index words: Acetamides, crabgrass, diphenylethers, interference, mulch, primrose, ragweed.

Abbreviations: GCREC, Gulf Coast Research and Education Center; WAP, weeks after planting.

Diflufenzopyr is an auxin-transport inhibitor that has increased broadleaf weed control by some auxin herbicides. The effects of auxin herbicides when applied with diflufenzopyr for leafy spurge or Canada thistle control, herbage production, and herbicide absorption and translocation in leafy spurge were evaluated. The influence of diflufenzopyr on leafy spurge and Canada thistle control varied by herbicide. Diflufenzopyr applied with quinclorac increased both Canada thistle and leafy spurge control. Diflufenzopyr added to picloram increased leafy spurge but not Canada thistle control, whereas control of both weeds generally increased when diflufenzopyr was applied with dicamba. Canada thistle control slightly improved when diflufenzopyr was applied with clopyralid or clopyralid plus 2,4-D compared with the herbicides alone. Diflufenzopyr did not influence weed control from imazapic and reduced weed control from glyphosate. Weed control was not influenced by the ratio of diflufenzopyr to herbicide or by whether diflufenzopyr was tank mixed with or applied before the herbicides. Diflufenzopyr did not affect cool-season grass production in the greenhouse or field but did reduce sideoats grama and switchgrass production when applied alone and with dicamba in greenhouse trials. ¹⁴C-picloram and ¹⁴C-quinclorac absorption was increased when applied with diflufenzopyr in leafy spurge but nearly all absorbed herbicide remained in the treated leaf compared with the herbicides applied alone. ¹⁴C-dicamba absorption decreased from 60 to 14% when applied with diflufenzopyr and translocation to the roots decreased by a factor of 10. Overall, the increase in weed control from the addition of diflufenzopyr was much more pronounced with leafy spurge than with Canada thistle.

Nomenclature: Clopyralid; 2,4-D; dicamba; diflufenzopyr; glyphosate; imazapic; picloram; quinclorac; Canada thistle, Cirsium arvense L. #³ CIRAR; leafy spurge, Euphorbia esula L. EPHES; sideoats grama, Bouteloua curtipendula (Michx.) Torr; switchgrass, Panicum virgatum L.

Additional index words: Absorption and translocation, invasive weed control, plant growth regulator.

Abbreviations: DAT, days after treatment; MAT, months after treatment; MSO, methylated seed oil; NIS, nonionic surfactant.

Limited information exists on sweet corn tolerance to postemergence (POST) applications of clopyralid under Ontario growing conditions. Eight sweet corn hybrids were evaluated for tolerance to clopyralid in three field experiments conducted in 2001 and 2002 in Ontario. Clopyralid was applied POST at 200 and 400 g ai/ha, the proposed and twice the proposed registered rate for use in sweet corn in Ontario. Sweet corn response to clopyralid did not vary among the hybrids tested. In 2001, visual injury among hybrids 7 d after treatment (DAT) with clopyralid at 400 g/ha was less than 3%. Subsequent visual injury evaluations at 14 and 28 DAT showed no differences among sweet corn hybrids at either rate of clopyralid evaluated. The application of clopyralid at 200 and 400 g/ ha had no detrimental effect on plant height or marketable yield of any of the eight sweet corn hybrids. On the basis of visual injury, height, and marketable yield response ‘Calico Belle’, ‘CNS 710’, ‘DelMonte 2038’, ‘GG 222’, ‘GG 246’, ‘GH 2684’, ‘Reveille’, and ‘Rival’ are all tolerant to the POST application of clopyralid.

Nomenclature: Clopyralid; sweet corn, Zea mays L.

Additional index words: Clopyralid, herbicide injury, sweet corn, sensitivity, tolerance.

Abbreviations: DAP, days after planting; DAT, days after treatment; POST, postemergence.

Studies were conducted at four sites during a 2-yr period in Oklahoma, Texas, and Arkansas to determine effectiveness and safety of halosulfuron in honeydew crops. Halosulfuron applied postemergence at 26.3 to 78.8 g ai/ha controlled yellow nutsedge 85 to 97%, golden crownbeard 100%, and tumble pigweed 83 to 95%. Control of yellow nutsedge continued to increase for 3 to 6 wk after treatment. Golden crownbeard and tumble pigweed efficacy increased to its highest levels after 4 and 3 wk, respectively. Reduced crop growth and yellowing of foliage did not exceed 13%. No differences were recorded for yield, earliness, or percentage of marketable fruit.

Nomenclature: Halosulfuron; golden crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray #³ VEEEN; tumble pigweed, Amaranthus albus L. # AMAAL; yellow nutsedge, Cyperus esculentus L. # CYPES; honeydew, Cucumus melo L. Inodorus group ‘Honeybrew’.

Additional index words: Melon crops, mulch, plasticulture, plastic mulch.

Abbreviations: POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

There is little information on the sensitivity of dry beans to flumioxazin. Tolerance of eight cultivars of dry beans representing four market classes (black, cranberry, kidney, and white beans) to preplant incorporated (PPI) and preemergence (PRE) applications of flumioxazin at the rate of 52.5, 70, and 140 g ai/ha were studied in three field experiments in Ontario in 2002 and 2003. There were no differences (P < 0.05) between two cultivars within a market class in their responses to flumioxazin. However, the four market classes differed in their responses to flumioxazin. Black and white beans were more sensitive to the PRE application of flumioxazin than cranberry and kidney beans. Flumioxazin applied PRE at 140 g/ha caused as much as 34% visual injury and reduced plant height by 23 to 28%, shoot dry weight by 35 to 39%, and yield by 20 to 30% in black and white bean market classes. Flumioxazin-applied PPI did not injure any market class. On the basis of this research, there is an acceptable margin of crop safety in these black and white bean cultivars only when flumioxazin is applied PPI. The two cranberry and kidney bean cultivars were tolerant to all rates of flumioxazin applied both PPI and PRE.

Nomenclature: Flumioxazin; black bean, cranberry bean, kidney bean, navy bean, white bean, Phaseolus vulgaris L.

Additional index words: Dry beans, herbicide tolerance, preemergence herbicides, preplant incorporated herbicides.

Abbreviations: DAE, days after emergence; OM, organic matter; PPI, preplant incorporated; PRE, preemergence.

The agrestal field violet, a pervasive weed in Europe, has been identified in reduced-tillage cereal fields in Alberta. The efficacy of herbicides in direct-seeded spring wheat was assessed on natural field violet infestations in Alberta in 2002 and 2003. Only fluroxypyr 2,4-D, applied postemergence, provided control of field violet in 2002 when rainfall was limiting. Over both years, this herbicide combination reduced biomass by 59 to 69% and plant density by 83 to 91%, relative to nontreated plots. The herbicides metsulfuron, sulfosulfuron, and thifensulfuron tribenuron only suppressed weed growth under drought conditions in 2002 but controlled the weed in 2003 when rainfall was greater, reducing plant density by 82 to 92% and rendering remaining plants sterile. Suppression was also observed with MCPA mecoprop dicamba in 2002 and 2003 and with metribuzin only in 2003. Effective control of field violet was conferred by a pre–crop emergence application of glyphosate at 445 g ae/ha in 2003, the only year that this treatment was evaluated. Activity of herbicides on three- to four-leaf seedlings was also evaluated in a greenhouse dose– response assay. All herbicides had greater efficacy in the greenhouse, and those that provided control in situ reduced field violet dry weight by 85% at less than the recommended rate used in field experiments. Management of field violet is possible with herbicides registered for use on spring wheat in Alberta. However, the weed does not appear to cause significant crop production losses; hence, herbicide selection should be based on knowledge of all weed species present within the field.

Nomenclature: 2,4-D; dicamba; fluroxypyr; glyphosate; MCPA; mecoprop; metribuzin; metsulfuron; sulfosulfuron; thifensulfuron; tribenuron; field violet, Viola arvensis Murr. #³ VIOAR; hard red spring wheat, Triticum aestivum L. ‘AC Barrie’.

Additional index words: Bentazon, direct seeded, herbicide evaluation, linuron, metribuzin, weed control.

Abbreviations: ALS, acetolactate synthase (EC 4.1.3.18); ED₅₀, effective herbicide dose necessary to cause a 50% reduction in weed dry weight; ED₈₅, effective herbicide dose necessary to cause an 85% reduction in weed dry weight; POST, postemergence; PREPLANT, pre–crop emergence; RU, reproductive units; WAT, weeks after treatment.

Experiments were conducted in the 2000 to 2001 and 2001 to 2002 growing seasons to evaluate the efficacy of AE F130060 03 plus AE F107892 with nonionic surfactant (NIS) or methylated seed oil (MSO) plus urea ammonium nitrate (UAN) applied in November (early postemergence, EP), January (middle postemergence, MP), and March (late postemergence, LP) for control of Italian ryegrass in barley. AE F130060 03 plus AE F107892 was also combined with MSO and UAN and various postemergence (POST) small grain herbicides at the three application timings. All AE F130060 03 plus AE F107892 treatment combinations controlled Italian ryegrass at least 84% at the three application timings. Treatment combinations of AE F130060 03 plus AE F107892 applied LP generally resulted in lower yields because of increased duration of Italian ryegrass competition, increased barley injury, and insufficient time for barley to recover from the injury. Transient phytotoxicity to barley occurred after EP and MP applications of all AE F130060 03 plus AE F107892 treatment combinations. LP applications of MSO and UAN or other POST small grain herbicides combined with MSO and UAN increased barley injury compared with injury from AE F130060 03 plus AE F107892 applied with NIS. Results indicate that AE F130060 03 plus AE F107892 treatments are an effective method for control of Italian ryegrass in barley; however, treatments should be applied either EP or MP to reduce early Italian ryegrass competition and allow sufficient time for barley recovery from injury before harvest.

Nomenclature: AE F107892, [diethyl 1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-3, 5-dicarboxylate]; AE F115008 00, [methyl 4-iodo-2-[3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-ureidosulfonyl]benzoate, sodium salt]; AE F130060 00, [methyl-2-[3-(4,6-dimethoxypyrimidin-2-yl)ureidosulfonyl]-4-methane-sulfonamidomethylbenzoate]; AE F130060 03 is a mixture of AE F130060 00 and AE F 115008 00; Italian ryegrass, Lolium multiflorum (Lam.) #³ LOLMU; barley, Hordeum vulgare (L.) # HORVX, ‘Nomini’.

Additional index words: Bromoxynil, chlorsulfuron, crop tolerance, dicamba, diclofop, diclofop resistance, metsulfuron, thifensulfuron, tribenuron, Triticum aestivum, TRZAW.

Abbreviations: EP, early postemergence; LP, late postemergence; MP, middle postemergence; MSO, methylated seed oil; NIS, nonionic surfactant; POST, postemergence; UAN, urea ammonium nitrate; WAT, weeks after treatment.

Field experiments were conducted in southwestern Oklahoma near Colony in 2000 and near Ft. Cobb in 2001 to quantify the effect of time of removal of a natural population of crownbeard on peanut yield. Weed densities and dry weed weights were measured at eight weed-removal times, and in-shell peanut yields were determined at harvest. Crownbeard was removed at 0 (the weed-free check), 4, 6, 8, 10, 12, 14, and 16 wk (full season) after crop emergence (WAE). Weed density was a poor predictor for dry weed weight and peanut yield; however, dry weed weight and time of removal were good predictors for peanut yield. Weed growth was minimal up to 4 WAE and increased linearly after that time. For each week of weed growth, a 0.52 kg/plot increase in dry weed weight was measured. Peanut yield decreased linearly because of crownbeard competition. For each kilogram per plot increase in dry weed weight, a 129 kg/ha or 5.1% peanut yield reduction took place. For each week of weed interference, a 75 kg/ha or 2.8% peanut yield reduction occurred. Crownbeard removal by or before 4 WAE will minimize losses in peanut yield because of interference.

Nomenclature: Crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray #³ VEEEN; peanut, Arachis hypogaea L.

Additional index words: Competition, competitive duration, dry weed weight, interference, weed density, yield.

Abbreviations: ANOVA, analyses of variance; WAE, weeks after crop emergence.

2,4-D is the most widely used herbicide for weed control in grain sorghum in northern Tamaulipas, Mexico. Crop injury caused by 2,4-D drift to nontarget crops commonly occurs because of prevailing high winds. Field experiments were conducted from 2001 to 2003 to evaluate an integrated weed management program in grain sorghum with alternative postemergence herbicides to 2,4-D at registered and reduced rates. Bromoxynil applied at 480 (registered rate), 360, and 240 g/ha provided excellent broadleaf weed control when adequate rainfall occurred. Prosulfuron at 14.2 g/ha applied broadcast without cultivation provided excellent weed control and sorghum yield comparable with 28.5 g/ha (registered rate). This treatment represented a 32% cost reduction and 50% reduction in herbicide input compared with prosulfuron applied at registered rate without cultivation, and 31% cost reduction compared with 2,4-D at the registered rate (590 g ae/ha) plus cultivation, considered the commercial standard.

Nomenclature: Bromoxynil; prosulfuron; 2,4-D; grain sorghum, Sorghum bicolor (L.) Moench. ‘Pioneer 82G63’.

Additional index words: Integrated weed management, IWM.

Abbreviations: POST, postemergence; WAT, weeks after treatment.

Field experiments were conducted in 2001 and 2002 at two sites in Ohio to characterize the effect of isoxaflutole herbicide applied the previous year to field corn on processing tomato, bell pepper, cabbage, snapbean, and cucumber. Isoxaflutole was applied preemergence to field corn in 2001 at 0, 53, 70, 105, and 210 g ai/ha. There were no rotational crop cultivar by herbicide rate interactions at either site. Generally, there was a higher level of visible injury on crops at the Fremont site. Isoxaflutole residues at either site did not affect processing tomato yield. Bell pepper yield was reduced 33% when rotated into 210 g ai/ha rate plots only at Fremont. Snapbean marketable yield was reduced by isoxaflutole carryover from 70 and 210 g ai/ha rates resulting in 0.39 and 0.0 t/ha at Fremont. Similarly, isoxaflutole soil residues from 105 and 210 g ai/ha resulted in 14 and 24% visible injury on cucumber but did not reduce marketable yield. Site differences in soil characteristics and precipitation in the application year may have contributed to observed differences in crop response.

Nomenclature: Isoxaflutole; bell pepper, Capsicum annuum L. ‘Aristotle’ and ‘Paladin’; cabbage, Brassica oleraceae L. var. capitata ‘Red Dynasty’ and ‘Huron’; corn, Zea mays L. ‘Pioneer 34B29 LL’; cucumber, Cucumis sativus ‘Vlasset’ and ‘Dasher 2’; processing tomato, Lycopersicon esculentum Mill. ‘Peto 626’ and ‘Heinz 9437’; snapbean, Phaseolus vulgaris L. ‘Strike’ and ‘Hialeah’.

Additional index words: Herbicide carryover, herbicide soil residues, rotational crops, vegetable crops.

Abbreviations: ANOVA, analysis of variance; CEC, cation exchange capacity; DAE, days after emergence; PRE, preemergence; SOM, soil organic matter.

Field experiments were conducted to compare large crabgrass control by clethodim or sethoxydim applied alone and with selected fungicides registered for use in peanut. Fluazinam, propiconazole plus trifloxystrobin, or tebuconazole did not affect efficacy of clethodim or sethoxydim. Azoxystrobin, boscalid, chlorothalonil, and pyraclostrobin reduced efficacy of clethodim and sethoxydim in some experiments. Increasing the herbicide rate increased large crabgrass control regardless of the addition of chlorothalonil. In laboratory experiments, ¹⁴C absorption was less when ¹⁴C-clethodim or ¹⁴C-sethoxydim was applied with chlorothalonil. Pyraclostrobin and tebuconazole did not affect absorption of ¹⁴C-clethodim or ¹⁴C-sethoxydim.

Nomenclature: Azoxystrobin, methyl (E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate; boscalid, 3-pyridinecarboxamide,2-chloro-N-[4′-chloro(1,1′-biphenyl)-2-yl]; chlorothalonil, tetrachloroisophthalonitrile; clethodim; fluazinam, 3-chloro-N-[3-chloro-2,6-dinitro-4-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2-pyridinamine; propiconazole, 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl]-1H-1,2,4triazole; pyraclostrobin, carbamic acid,[2-[[[1-(4-chlorophenyl)-1H-pyrazol-3yl]oxy]methyl]phenyl]methoxy-,methyl ester; sethoxydim; tebuconazole, α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol; trifloxystrobin, benzeneacetic acid, α-(methoxyimino)-2-[[[(E)-[1-[3-(trifluoromethyl)phenyl]ethylidene]amino]oxy]methyl]-,methylester (E,E); large crabgrass, Digitaria sanguinalis (L.) Scop. #³ DIGSA; peanut, Arachis hypogaea L.

Additional index words: Herbicide absorption, pesticide interaction.

Abbreviation: LSS, liquid scintillation spectrometry.

Field studies were conducted in 2000 and 2001 at Rohwer, AR. Trifloxysulfuron (5.3 and 8 g ai/ha) and pyrithiobac (70 g ai/ha) were applied preemergence (PRE) and postemergence (POST) broadcast at the two- to three-leaf (EP) and three- to four-leaf (MP) cotton growth stages. Both materials were also applied POST in combination with glyphosate at 560 g ae/ha or bromoxynil at 560 g ai/ha at both growth stages. Trifloxysulfuron applied EP or MP at 8 g/ha provided greater control of sicklepod and pitted morningglory 28 d after application (DAA) than trifloxysulfuron at 5.3 g/ha or pyrithiobac at 70 g/ha; however, control of prickly sida was greater with pyrithiobac than with trifloxysulfuron at either rate. Glyphosate alone controlled sicklepod, prickly sida, and pitted morningglory greater than 80%. The addition of trifloxysulfuron at 8 g/ha and pyrithiobac at 70 g/ ha increased control of all species over glyphosate alone 28 DAA. Bromoxynil at 560 g/ha controlled pitted morningglory and hemp sesbania at all application timings; however, sicklepod and Palmer amaranth control was less than 50% with bromoxynil applied alone. When bromoxynil was applied in combination with trifloxysulfuron at either rate, control of sicklepod and Palmer amaranth increased to 80% or greater at all application timings. Trifloxysulfuron has the potential to complement both the glyphosate-resistant and bromoxynil-resistant weed control programs by providing control of less susceptible weeds and by providing residual control to both programs.

Nomenclature: Bromoxynil; glyphosate; pyrithiobac; trifloxysulfuron; hemp sesbania, Sesbania exaltata (Raf.) Rybd. ex A.W. Hill #³ SEBEX; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; sicklepod, Senna obtusifolia L. # CASOB; cotton, Gossypium hirsutum L. # GOSHI.

Additional index words: Application timings, bromoxynil-resistant cotton, glyphosate, glyphosate-resistant cotton, residual herbicides, transgenic cotton, trifloxysulfuron sodium.

Abbreviations: BXN, bromoxynil-resistant; DAA, days after application; EP, early postemergence; MP, mid-postemergence; POST, postemergence over-the-top; PRE, preemergence.

Small broomrape is an annual, parasitic weed that was discovered recently in Oregon's red clover seed production system. Field experiments were conducted in 2002 and 2003 at two locations to evaluate 10 herbicide treatments applied after small broomrape emergence in red clover. Bentazon, bromoxynil, glyphosate, imazamox, imazamox plus bentazon, imazethapyr, MCPA, and pendimethalin were evaluated. Small broomrape density, small broomrape seed viability after treatment, and clover injury and seed yield were quantified. Small broomrape control with imazamox, glyphosate, and imazamox plus bentazon treatments was greater than the nontreated check in both years. However, imazamox and imazamox plus bentazon treatments were the only herbicide treatments that consistently exhibited a high level of crop safety, reduced small broomrape density, and did not reduce red clover yield. Herbicide treatments did not prevent production of viable small broomrape seeds. Future research is needed to develop control options that will prevent red clover yield loss and viable small broomrape seed production when applied before small broomrape emergence.

Nomenclature: Bentazon; bromoxynil; glyphosate; imazamox; imazethapyr; MCPA; pendimethalin; small broomrape, Orobanche minor Sm. #³ ORAMI; red clover, Trifolium pratense L. # TRFRE.

Additional index words: Parasitic weed.

Abbreviations: DAT, days after treatment.

Infestations of Italian ryegrass are difficult to control and decrease marketability of cool-season sod. Tests were conducted at three locations in Virginia in 2002 and 2003 to determine herbicide control options for Italian ryegrass in 90:10 tall fescue:Kentucky bluegrass turfgrass seeded the previous fall. Chlorsulfuron, diclofop, fluazifop plus fenoxaprop, and metsulfuron controlled 5- to 30-tiller Italian ryegrass less than 50% 10 wk after initial treatment (WAIT). Nicosulfuron at 53 g ai/ha controlled Italian ryegrass 69 to 95% and injured turf no greater than 10% at all locations 10 WAIT. Primisulfuron at 53 g ai/ha controlled Italian ryegrass less than 30% in 2002 and 59 to 63% at two locations in 2003 10 WAIT and injured turf less than 5% at all locations. Results indicate nicosulfuron can be used for Italian ryegrass control in tall fescue or tall fescue and Kentucky bluegrass turf if temporary injury is acceptable.

Nomenclature: Chlorsulfuron; diclofop; fenoxaprop; fluazifop; metsulfuron; nicosulfuron; primisulfuron; Italian ryegrass, Lolium multiflorum Lam. #³ LOLMU; Kentucky bluegrass, Poa pratensis L. ‘Midnight’, ‘Millenium’; tall fescue, Festuca arundinacea Schreb. ‘Falcon III’, ‘Rebel II’.

Additional index words: Sod production, turfgrass injury, weed control.

Abbreviations: ESF, Enfield Sod Farm, Aylett, VA, 2002; TRC, Turfgrass Research Center, Blacksburg, VA, 2003; VTF, Virginia Turf Farm, Baskerville, VA, 2003; WAIT, weeks after initial treatment.

Studies were conducted at Clayton, Lewiston-Woodville, and Rocky Mount, NC, to evaluate weed and cotton response to herbicide systems in glyphosate-resistant cotton in 1995 and 1997. Herbicide systems evaluated included various combinations of soil-applied (trifluralin and fluometuron) and postemergence (POST) (glyphosate or pyrithiobac) herbicides with or without late postemergence-directed (LAYBY) treatments of cyanazine plus MSMA. Glyphosate-resistant cotton injury was less than 5% with all herbicide treatments. Glyphosate POST systems were as efficacious in weed control as other herbicide systems. Depending on location, glyphosate and pyrithiobac POST systems usually required cyanazine plus MSMA LAYBY for season-long control of common lambsquarters, goosegrass, large crabgrass, pitted morningglory, prickly sida, and Texas panicum. Glyphosate POST applied as needed provided weed control equivalent to soil-applied plus POST herbicides, although lint yield was slightly reduced depending on location. Herbicide systems that included soil-applied herbicides required one to two treatments of glyphosate POST and post-directed for season-long weed control and high cotton lint yields, whereas the same herbicide systems without soil-applied herbicides required two to three glyphosate treatments. In all herbicide systems, a residual soil-applied or LAYBY herbicide treatment increased yield compared with glyphosate POST only systems. Location influenced weed control and cotton yield. Generally, as herbicide inputs increased, yield increased.

Nomenclature: Cyanazine; fluometuron; glyphosate; MSMA; pyrithiobac; trifluralin; common lambsquarters, Chenopodium album L. #³ CHEAL; goosegrass, Eleusine indica (L.) Gaertn. # ELEIN; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; Texas panicum, Panicum texanum Buckl. # PANTE; cotton, Gossypium hirsutum L. ‘Paymaster 1330RR’.

Additional index words: CHEAL, DIGSA, ELEIN, herbicide-resistant crops, IPOLA, PANTE, SIDSP.

Abbreviations: ANS, as needed spray; fb, followed by; LAYBY, late postemergence-directed; PDS, post-directed; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Field studies investigated possible interactions associated with early-season coapplication of the herbicide pyrithiobac and various insecticides. Pyrithiobac at 70 g ai/ha, in combination with the insecticides acephate or dicrotophos at 370 g ai/ha, fipronil at 56 g ai/ha, imidacloprid at 52 g ai/ha, lambda-cyhalothrin at 37 g ai/ha, or oxamyl, carbofuran, or dimethoate at 280 g ai/ha did not reduce cotton leaf area, height, main stem node number, main stem nodes to first square, days to first square or flower, main stem nodes above white flower, or seed cotton yield compared with pyrithiobac alone. Pyrithiobac alone reduced dry weight of pitted morningglory, hemp sesbania, prickly sida, velvetleaf, and entireleaf–ivyleaf morningglory 28 d after treatment (DAT) 86, 98, 51, 94, and 91%, respectively, and weed control was not affected by the coapplication of insecticides. Control of thrips (adult plus larvae) 5 DAT with insecticides was unaffected by pyrithiobac addition at the P = 0.05 level of significance. At the P = 0.1 level, however, addition of pyrithiobac to dimethoate resulted in a reduction in insecticide efficacy in one of three experiments. Efficacy of other insecticides was unaffected.

Nomenclature: Acephate, O,S-dimethyl acetylphosphoramidothioate; carbofuran, 2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate; dicrotophos, 3-dimethoxyphosphinoyloxy-N,N-dimethylisocrotonamide; dimethoate, O,O-dimethyl-S-methylcarbamoylmethyl phosphorodithioate; fipronil, 5-amino-1-(2,6-dichloror-α,α,α-triflouro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile; imidacloprid, (EZ)-1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine; lambda-cyhalothrin, reaction product comprising equal quantities of (S)-α-cyano-3-phenoxybenzyl (Z)-(1R,3R)-3-(2-chloro-3,3,3-trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate and (R)-α-cyano-3-phenoxybenzyl (Z)-(1S,3S)-3-(2-chloro-3,3,3-trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate or of (S)-α-cyano-3-phenoxybenzyl (Z)-(1R)-cis-3-(2-chloro-3,3,3-trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate and (R)-α-cyano-3-phenoxybenzyl (Z)-(1S)-cis-3-(2-chloro-3,3,3-trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate; oxamyl, (EZ)-N,N-dimethyl-2-methylcarbamoyloxyimino-2-(methylthio)acetamide; pyrithiobac; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray #³ IPOHE; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A. W. Hill # SEBEX; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; velvetleaf, Abutilon theophrasti Medic. # ABUTH; cotton, Gossypium hirsutum L.

Additional index word: Herbicide–insecticide interaction.

Abbreviations: DAT, days after treatment; NAWF, node above white flower; POST, postemergence; PPI, preplant incorporated; PRE, preemergence.

Field research was conducted in Arkansas for 3 yr to evaluate imazamox for control of diclofop-resistant Italian ryegrass in imidazolinone-tolerant wheat. Italian ryegrass was controlled at least 89% 49 d after wheat emergence (DAE) in year 2 and 3 by imazamox at 36 g ai/ha applied to one- to two-leaf wheat (POST1), by imazamox at 54 g ai/ha applied sequentially at POST1 followed by (fb) application to three- to four-leaf wheat (POST2), by pendimethalin at 1120 g ai/ha preemergence (PRE) fb imazamox at 36 or 54 g/ha POST1, and by chlorsulfuron plus metsulfuron at 22 plus 4 g ai/ha PRE. Italian ryegrass was controlled at least 95% 150 DAE with all applications in year 1 because of extremely cold temperatures and snowfall in December and January. Only sequential imazamox applications or pendimethalin PRE fb imazamox POST1 equaled the commercial standard, chlorsulfuron plus metsulfuron, for control of Italian ryegrass 150 DAE in years 2 and 3. These treatments controlled Italian ryegrass greater than 80% 150 DAE. Sequential postemergence applications of imazamox or programs containing pendimethalin PRE fb imazamox POST1 are necessary to optimize Italian ryegrass control and wheat yield in an imidazolinone-tolerant wheat production system.

Nomenclature: Chlorsulfuron; diclofop; imazamox; metsulfuron; pendimethalin; Italian ryegrass, Lolium multiflorum Lam. #³ LOLMU; winter wheat, Triticum aestivum L. # TRAES; ‘AP110CL’, ‘Washington’.

Additional index words: Diclofop resistance, sequential applications, wheat yield.

Abbreviations: AHAS, acetohydroxyacid synthase (EC 4.1.3.18); DAE, days after wheat emergence; fb, followed by; POST1, one- to two-leaf wheat; POST2, three- to four-leaf wheat; PRE, preemergence.

Volunteer potato is becoming increasingly detrimental in potato production regions. We assessed methods to manage the weed in field corn with herbicides and arthropod herbivory. In greenhouse trials, new tuber production was reduced at least 95% in ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, and ‘Shepody’ potato varieties by mesotrione applied at 0.11 kg/ha. In field studies conducted near Paterson, WA, a single application of mesotrione at 0.07 or 0.11 kg/ha applied at the time of tuber initiation (mid-postemergence [MPOST]) controlled potato top growth 96 to 98% in 2002 and 2003. Mesotrione applied at earlier stages of potato growth, preemergence or early postemergence, controlled potatoes less than mesotrione applied MPOST. All herbicide treatments prevented yield loss in field corn compared with nontreated checks. Mesotrione reduced new potato tubers and tuber weight more than any other herbicide. Herbivory of volunteer potato by Colorado potato beetle reduced tuber number 21% and tuber density 23% in the absence of herbicides and appeared to further suppress the weed in combination with herbicides. Whereas treatments containing mesotrione were most effective against volunteer potato, arthropod herbivory supplemented weed suppression and may be an important component in reduced or low-input weed management systems.

Nomenclature: Mesotrione; volunteer potato, Solanum tuberosum L. ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, ‘Shepody’; field corn, Zea mays L.; Colorado potato beetle, Leptinotarsa decemlineata Say.

Additional index words: Arthropod herbivory, biological weed control, groundkeeper (volunteer potato), integrated weed management.

Abbreviations: CPB, Colorado potato beetle; EPOST, early postemergence; IWM, integrated weed management; LPOST, late postemergence; MPOST, mid-postemergence; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

Experiments were conducted during 1999, 2002, and 2003 to evaluate sicklepod control by 2,4-DB applied alone or in mixture with selected fungicides and insecticides registered for use in peanut. The fungicides boscalid, chlorothalonil, fluazinam, propiconazole plus trifloxystrobin, pyraclostrobin, or tebuconazole and the insecticides acephate, carbaryl, esfenvalerate, fenpropathrin, lambda-cyhalothrin, methomyl, or indoxacarb applied in mixtures with 2,4-DB did not reduce sicklepod control by 2,4-DB compared with 2,4-DB alone. The fungicide azoxystrobin reduced control in some but not all experiments. Sicklepod control was highest when 2,4-DB was applied before flowering regardless of fungicide treatment. Seed production and germination were reduced when 2,4-DB was applied 81 to 85 d after emergence when sicklepod was flowering. Applying 2,4-DB before flowering and at pod set and pod fill did not affect seed production.

Nomenclature: Acephate, O,S-dimethyl acetylphosphoramidiothioate; azoxystrobin, methyl (E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate; boscalid, 3-pyridinecarboxamide,2-chloro-N-[4′-chloro(1,1′-biphenyl)-2-yl]; carbaryl, 1-napthyl N-methylcarbamate; chlorothalonil, tetrachloroisophthalonitrile; 2,4-DB; esfenvalerate, (S)-cyano (3-phenoxyphenyl) methyl (S)-4-chloro-α-(1-methylethyl)benzenacetate; fenpropathrin, α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate; fluazinam, 3-chloro-N-[3-chloro-2,6-dinitro-4-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2-pyridinamine; indoxacarb, (S)-methyl 7-chloro-2,5-dihydro2-[[ (methoxy-carbonyl) [ 4(trifluorometoxy)phenyl]amino]-carbonyl]indeno[1,2-e][1,3,4]oxadiazine-4a-(3H)-carboxylate; lambda-cyhalothrin, [1,α(S*),3α(Z)]-(±)-cyano-(3-phenoxyphenyl)methyl-3-(2-chloro-3,3,3-tifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate; methomyl, S-methyl-N-[(methylcarbamoyl)oxy] thioacetimidate; propiconazole, 1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl]-1H-1,2,4 triazole; pyraclostrobin, carbamic acid, [2-[[[1-(4-chlorophenyl)-1H-pyrazol-3yl]oxy]methyl]phenyl]methoxy-,methyl ester; tebuconazole, α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol; trifloxystrobin, benzeneacetic acid, α-(methoxyimino)-2-[[[(E)-[1-[3-(trifluoromethyl)phenyl] ethylidene]amino]oxy]methyl]-, methylester (E,E); sicklepod, Senna obtusifolia L. Irwin and Barneby #³ CASOB; peanut, Arachis hypogaea L.

Additional index word: Pesticide interaction.

Abbreviation: DAE, days after emergence.

Experiments were conducted in North Carolina during 2002 and 2003 to evaluate broadleaf signalgrass and large crabgrass control by clethodim and sethoxydim applied in two-, three-, or four-way mixtures with fungicides, insecticides, and foliar fertilizer–plant growth regulator treatments. Broadleaf signalgrass and large crabgrass control by clethodim and sethoxydim was not reduced by the insecticides esfenvalerate, indoxacarb, or lambda-cyhalothrin. The fungicides azoxystrobin, chlorothalonil, pyraclostrobin, and tebuconazole reduced large crabgrass control by clethodim or sethoxydim in one or more of three experiments for each herbicide. Disodium octaborate and the plant growth regulator prohexadione calcium plus urea ammonium nitrate (UAN) mixed with clethodim and fungicides improved large crabgrass control in some experiments. In contrast, prohexadione calcium plus UAN and disodium octaborate did not affect broadleaf signalgrass or large crabgrass control by sethoxydim.

Nomenclature: Azoxystrobin, methyl (E)-2-{2-[6-(2-cyanophenoxy) pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate; chlorothalonil, tetrachloroisophthalonitrile; clethodim; esfenvalerate, (S)-cyano (3-phenoxyphenyl) methyl (S)-4-chloro-α-(1-methylethyl)benzenacetate; indoxacarb, (S)-methyl 7-chloro-2,5-dihydro2-[[(methoxy-carbonyl)[4(trifluorometoxy)phenyl]amino]-carbonyl]indeno[1,2-e][1,3,4]oxadiazine-4a-(3H)-carboxylate; lambda-cyhalothrin, [1,α(S*),3α(Z)]-(±)-cyano-(3-phenoxyphenyl)methyl-3-(2-chloro-3,3,3-tifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate; prohexadione calcium, calcium 3-oxido-5-oxo-4-propionylcyclohex-3-enecarboxylate; pyraclostrobin, methyl ester of [2-[[[1-(4-chlorophenyl)-1H-pyrazol-3yl]oxy]methyl]phenyl]methoxy-, carbamic acid; sethoxydim; tebuconazole, α-[2-(4-chlorophenyl)ethyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol; broadleaf signalgrass, Brachiaria platyphylla (Griseb). Nash #³ BRAPP; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA.

Additional index words: Pesticide compatibility, pesticide interaction.

Abbreviations: PGR, plant growth regulator; UAN, urea ammonium nitrate.

Leafy spurge is a deep-rooted perennial weed that displaces native rangeland vegetation and replaces forage for cattle and other forages used by vertebrate herbivores. Strategic planning to control this weed requires monitoring its distribution and spread. Classical monitoring techniques, which often involve extensive ground survey efforts, can be aided by the synoptic nature of remotely sensed imagery. This research addresses the use of Space Imaging's 4-m multispectral Ikonos imagery for the survey and detection of leafy spurge infestations. Survey data were collected at a site in western North Dakota and used to produce supervised classifications of leafy surge infestations with Ikonos imagery. Multiple image dates per year were combined with each other to assess the added accuracy afforded by multitemporal imagery. Finally, individual patches of leafy spurge were analyzed to determine the minimum patch size and percent cover that were detectable with supervised classification of Ikonos imagery. Under some circumstances, the imagery was effective at detecting leafy spurge, but in areas with a higher forb component, the classification was not as effective. Multidate imagery provided increased accuracy, but improvements were not consistently significant. Leafy spurge infestations of <30% cover and 200 m² were not reliably detected.

Nomenclature: Leafy spurge, Euphorbia esula L. #³ EPHES.

Additional index words: Accuracy assessment, digital photography, EPHES, global positioning system, Ikonos, image analysis.

Abbreviations: GPS, global positioning system; RMS, root-mean-square.

Increasing the pH of the spray water to solubilize the weak acid herbicide nicosulfuron and then decreasing pH below its pK_a so that it converts into a neutral form enhances biological activity under some conditions. The water-dispersible granule formulation of nicosulfuron starts as dispersed particles. Adding 1% wt/wt K₃PO₄ solubilizes nicosulfuron and increases its activity compared to its dispersion without base. The type of buffer and the surfactant HLB or hydrophilic lipophilic balance, a measure of the molecular balance of the hydrophilic and lipophilic groups, altered the activity of nicosulfuron. Adding 1% wt/wt K₃PO₄ increases the pH, and the optimum HLB ranged from 13 to 17 on large crabgrass. Adding 1% wt/wt H₃PO₄ reduces the pH and lowers the optimum HLB range from 10 to 14 on large crabgrass. Adding the acidic buffer converts the solubilized nicosulfuron into its neutral form and increases activity under some surfactant conditions. Thus, neutral nicosulfuron is more active with lipophilic surfactants, while ionic nicosulfuron is more active with hydrophilic surfactants. When tested on other species, low HLB surfactants are the most active at low pH. These results support the concept that the physicochemical properties of the herbicide, adjuvants, and weed species should be matched for optimum activity.

Nomenclature: Common cocklebur, Xanthium strumarium L. #³ XANST; common lambsquarters, Chenopodium album L. # CHEAL; giant foxtail, Setaria faberi Herrm. # SETFA; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; purple nutsedge, Cyperus rotundus L. # CYPRO; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; velvetleaf, Abutilon theophrasti Medicus # ABUTH.

Additional index words: Acid, adjuvant, base, basic blend, buffer, formulation, hydrophilic–lipophilic balance, nicosulfuron, nonionic surfactant, phosphoric acid, potassium phosphate, sulfonylurea, water-dispersible granule, weak acid.

Abbreviations: HLB, hydrophilic–lipophilic balance; NIS, nonionic surfactant; NPE, nonylphenol ethoxylate; WDG, water-dispersible granule.

Field experiments were conducted in 2002 and 2003 in Beaumont, TX, to evaluate the effect of flood timing on red rice control with imazethapyr applied at different cultivated rice growth stages. Treatments included flood establishment at 1, 7, 14, and 21 d after postemergence (POST) herbicide treatment (DAT). Imazethapyr was applied preemergence at 70 g ai/ha followed by 70 g/ ha POST when imidazolinone-tolerant rice cultivar ‘CL-161’ had three- to four-leaf stage (EPOST) or five-leaf stage (LPOST). Flood needed to be established within 14 DAT to achieve at least 95% red rice control when imazethapyr was applied EPOST. However, flood needed to be established within 7 DAT to provide at least 95% red rice control when imazethapyr was applied LPOST. Delaying the flood up to 21 DAT reduced rice grain yield for both application timings.

Nomenclature: Imazethapyr; red rice, Oryza sativa L., #ORYSA³; rice, Oryza sativa L., cultivar ‘CL-161.’

Additional index words: Acetolactate synthase (EC 4.1.3.18), ALS inhibitor, Clearfield rice, imidazolinone, water management.

Abbreviations: ANOVA, analysis of variance; DAPOST, days after postemergence treatments; DAT, days after treatment; EMS, ethyl methanesulfonate; EPOST, early postemergence; LPOST, late postemergence; POST, postemergence; PRE, preemergence.

Postdispersal seed predation by ground beetles may be an important form of biological weed control. Field experiments conducted in 2002 and 2003 determined invertebrate seed predators' ability to detect and remove seeds from different experimental substrates. Predation of wild mustard and common lambsquarters was greater when seeds were presented on sand compared with the two types of synthetic finishing pads; however, predation of velvetleaf, redroot pigweed, and hairy galinsoga was unaffected by substrate. Predation rates were not consistent across all experimental substrates. Estimates of invertebrate predation of common lambsquarters, yellow foxtail, and velvetleaf were greater for seeds offered on sand or synthetic pads than for seeds offered on soil or double-sided tape covered with soil. Although each substrate would be useful to estimate treatment effects on relative predation rates, the weed species by substrate interaction should be considered when comparing predation rates across experiments or when the absolute rate predation is of critical importance.

Nomenclature: Common lambsquarters, Chenopodium album L. #³ CHEAL; hairy galinsoga, Galinsoga ciliata (Raf.) Blake # GALCI; redroot pigweed, Amaranthus retroflexus L. # AMARE; velvetleaf, Abutilon theophrasti Medicus # ABUTH; wild mustard, Brassica kaber (DC.) L.C. Wheeler #BRAKA; yellow foxtail, Setaria glauca (L.) Beauv. #SETLU.

Additional index words: Biological control, biocontrol, Carabidae, ground beetle, invertebrate seed predators, methods in weed ecology, seed bank dynamics, seed predation.

Diagnosis of herbicide injury can be complex because of the large number and interaction of factors leading to herbicide injury. Computer-based expert systems have great potential to assist users, particularly nonexperts, in accurate diagnosis of herbicide injury. Rule-based and case-based reasoning are the most widely used forms of expert systems, and each system has strengths and limitations. Approaches that integrate rule-based and case-based reasoning may augment the positive aspects of the two reasoning methods and simultaneously minimize their negative aspects. The Herbicide Injury Diagnostic Expert System (HIDES) integrates rule-based and case-based reasoning and uses field-specific information, injury symptoms, herbicide use history, and herbicide information to diagnose crop injury from herbicides. The HIDES program uses a set of rules to identify suspect herbicide(s) that is the candidate for causing the observed injury and possible sources of the suspect herbicide(s). Case-based reasoning is used to propose a probable cause of injury by making an analogy to previously solved cases. A four-step procedure is followed when using HIDES: information collection, suspect herbicide identification, suspect herbicide source determination, injury reason suggestion, and knowledge accumulation.

Additional index words: Case-based reasoning, knowledge-base, rule-based reasoning.

Abbreviation: HIDES, herbicide injury diagnostic expert system.

A survey was conducted in 2000 across 38 counties in Mississippi on 192 randomly selected soybean fields to assess the most common occurring weeds. Statewide, prickly sida, which was present in 40% of the fields sampled, was the most common. Pitted and entireleaf morningglory were present in 34 and 29% of the soybean fields, respectively. Broadleaf signalgrass and barnyardgrass were the most common annual grasses, and yellow nutsedge was the most common sedge observed. Trumpetcreeper and redvine were the most common perennial vines. In the Mississippi Delta region of Mississippi, prickly sida was present in 45% of the fields sampled. The trend of occurrence of other species in the Delta mirrored statewide results. In eastern Mississippi, prickly sida and broadleaf signalgrass were found in 43% of soybean fields. Sicklepod, common cocklebur, and balloonvine were more prevalent in eastern Mississippi, when compared with the Mississippi Delta. Since 1982, there has been a sevenfold decline in the occurrence of common cocklebur and a fourfold decline in the occurrence of johnsongrass in Mississippi soybean. Also, the occurrences of redroot pigweed, common ragweed, and fall panicum have declined. Conversely, the occurrences of yellow nutsedge and broadleaf signalgrass have increased. The occurrences of barnyardgrass, prickly sida, redvine and trumpetcreeper have been relatively static over the past two decades.

Nomenclature: Balloonvine, Cardiospermum halicacabum L. #³ CRIHA; barnyardgrass, Echinochloa crus-galli (L.) Beauv. # ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash # BRAPP; common cocklebur, Xanthium strumarium L. # XANST; common ragweed, Ambrosia artemisiifolia L. # AMBEL; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray # IPOHG; fall panicum, Panicum dichotomiflorum Michx. # PANDI; johnsongrass, Sorghum halepense (L.) Pers. # SORHA; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; redvine, Brunnichia ovata (Walt.) Shinners # BVRCI; sicklepod, Senna obtusifolia (L.) Irwin and Barneby # CASOB; trumpetcreeper, Campsis radicans (L.) Seem. Ex Bureau # CMIRA; yellow nutsedge, Cyperus esculentus L. # CYPES; soybean, Glycine max (L.) Merr.

Additional index words: Annual grasses, common weeds, Mississippi Delta, nutsedge, perennial vine, weed survey.

Abbreviations: ALS, acetolactate synthase; EM, eastern Mississippi; MASS, Mississippi Agricultural Statistics Service; MD, Mississippi Delta.