We studied mechanisms of resistance to Bacillus thuringiensis insecticidal crystal protein Cry1C in the diamondback moth, Plutella xylostella (L.). Binding assays with midgut brush border membrane vesicles prepared from whole larvae showed no significant difference between resistant and susceptible strains in binding of radioactively-labeled Cry1C. These results indicate that reduced binding of Cry1C to midgut membrane target sites did not cause resistance to Cry1C. Thus, the mechanism of resistance to Cry1C differs from that observed in several previously reported cases of resistance to Cry1A toxins in diamondback moth. We tested Cry1C toxin and Cry1C crystalline protoxin against resistant and susceptible larvae using leaf disk bioassays. After adjusting for the size difference between Cry1C toxin and protoxin, we found that with resistant larvae, toxin was significantly more toxic than protoxin. In contrast, with susceptible larvae, no significant difference in toxicity occurred between Cry1C toxin and protoxin. The resistance ratios for Cry1C were 19 for toxin and 48 for protoxin. These results suggest that reduced conversion of Cry1C protoxin to toxin is a minor mechanism of resistance to Cry1C. Because neither reduced binding nor reduced conversion of protoxin to toxin appear to be major mechanisms, one or more other mechanisms are important in diamondback moth resistance to Cry1C.

Soil insecticides were evaluated in laboratory and field studies against larvae of an insecticide resistant population (Phelps County, NE) of western corn rootworm,Diabrotica virgifera virgiferaLeConte. Insecticide toxicity was evaluated by topical application of technical insecticides to 3rd instars from Saunders County, NE (susceptible) and Phelps County populations. Resistance ratios (LD₅₀Phelps County/LD₅₀Saunders County) for the insecticides methyl parathion, tefluthrin, carbofuran, terbufos, and chlorpyrifos were 28.0, 9.3, 8.7, 2.6 and 1.3, respectively. Biochemical investigation of suspected enzymatic resistance mechanisms in 3rd instars identified significant elevation of esterase activity (alpha and beta naphthyl acetate hydrolysis [3.8- and 3.9-fold]). Examination of 3rd instar esterases by native PAGE identified increased intensity of several isoenzymes in the resistant population. Assays of cytochrome P₄₅₀ activity (4-CNMA demethylation and aldrin epoxidation) did not identify elevated activity in resistant 3rd instars. Granular soil insecticides were applied at planting to corn, Zea mays L., in replicated field trials in 1997 and 1998 at the same Phelps County site as the source of resistant rootworms for the laboratory studies. In 1997, planting time applications of Counter 20CR, Counter 15 G (terbufos), and Lorsban 15 G (chlorpyrifos) resulted in the lowest root injury ratings (1–6 Iowa scale); 2.50, 2.55, 2.65, respectively (untreated check root rating of 4.55). In 1998, all insecticides performed similarly against a lower rootworm density (untreated check root rating of 3.72). These studies suggest that resistance previously documented in adults also is present in 3rd instars, esterases are possibly involved as resistance mechanisms, and resistance to methyl parathion in adults is also evident in larvae, but does not confer cross-resistance in larvae to all organophosphate insecticides.

Heritability of Chilo suppressalis (Walker) tolerance to the Cry1Ab toxin of Bacillus thuringiensis Berliner was estimated using a half-sibling design. Artificial diet with and without Cry1Ab was infested with progenies of 20 males, each mated with 2 females, and mortality was scored 5 d after infestation. The progeny of each female was reared and scored separately. Mean mortality of the 20 families on the Cry1Ab diet was 46.5%. The effects of both male parent and of female parent within male parent were significant. Heritability was estimated to be 0.52, suggesting that a high proportion of phenotypic variation was because of genetic differences. Mortality on the Cry1Ab diet was not correlated with mortality on control diet, indicating that differences among families in tolerance to Cry1Ab were not attributable to differences in general fitness. Our results indicate that “high dose” Bt rice plants may be particularly important for Cry1Ab resistance management in C. suppressalis populations.

Cytochrome P450 monooxygenases (P450) are membrane-bound hemoproteins that play important roles in conferring protection against both naturally occurring phytochemicals and synthetic organic insecticides. Despite the potential for common modes of detoxification, cross-resistance between phytochemicals and synthetic organic insecticides has rarely been documented. In this study, we examined the responses of a susceptible strain of corn earworm, Helicoverpa zea (Boddie), a polyphagous noctuid, to exposure by an allelochemical infrequently encountered in its host plants and by an insecticide widely used for control purposes. Within a single generation, survivors of xanthotoxin exposure displayed higher levels of tolerance to α-cypermethrin than did unexposed control larvae. The F₁ offspring of xanthotoxin-exposed survivors also displayed higher α-cypermethrin tolerance than did offspring of unexposed control larvae, suggesting that increased α-cypermethrin tolerance after xanthotoxin exposure represents, at least in part, heritable resistance. Administration of piperonyl butoxide, a P450 synergist, demonstrated that resistance to both xanthotoxin and α-cypermethrin is P450-mediated. α-Cypermethrin-exposed survivors, however, failed to show superior growth on xanthotoxin diets. Assays with control larvae, larvae induced by both xanthotoxin and α-cypermethrin, and survivors of LD₅₀ doses of both compounds indicated that H. zea midgut P450s are capable of metabolizing both xanthotoxin and α-cypermethrin. Metabolism of each compound is significantly inhibited by the presence of the other compound, suggesting that at least one form of P450 in H. zea midguts degrades both compounds and may constitute the biochemical basis for possible cross-resistance. Compared with control larvae, xanthotoxin- and α-cypermethrin-induced larvae displayed 2- to 4-fold higher P450-mediated metabolism of both compounds. However, xanthotoxin- and α-cypermethrin-exposed survivors exhibited much higher (2.5- to 11-fold) metabolism of both compounds than did the induced larvae. The metabolism results, like the bioassay results, are consistent with the interpretation that increased α-cypermethrin tolerance after xanthotoxin exposure is attributable mainly to heritable resistance.

The refuge plus high-dose strategy for resistance management assumes that the frequency of resistance alleles is low. We used an F₂ screen to estimate the frequency of resistance to transgenic corn that produces Bacillus thuringiensis Berliner Cry1Ab toxin (Bt corn) in an Iowa population of European corn borer, Ostrinia nubilalis (Hübner). We also proposed a modification to the statistical analysis of the F₂ screen that extends its application for nonuniform prior distributions and for repeated sampling of a single population. Based on a sample of 188 isofemale lines derived from females caught at light traps during the 2nd flight of 1997, we show with 95% confidence that the frequency of resistance to Bt corn was <3.9 × 10⁻³ in this Iowa population. These results provide weak evidence that the refuge plus high-dose strategy may be effective for managing resistance in O. nubilalis to Bt corn. Partial resistance to Cry1Ab toxin was found commonly. The 95% CI for the frequency of partial resistance were [8.2 × 10⁻⁴, 9.4 × 10⁻³] for the Iowa population. Variable costs of the method were $14.90 per isofemale line, which was a reduction of 25% compared with our initial estimate.

Biochemical mechanisms of malathion resistance were investigated in a malathion-resistant strain of the parasitoid Habrobracon hebetor Say collected from a farm storage in Kansas. General esterase activities were significantly lower in the resistant strain compared with those in a susceptible strain. However, no significant differences were found in activities of malathion specific carboxylesterase (MCE), glutathione S-transferase and cytochrome P450 dependent O-demethylase activities, cytochrome P450 contents, and sensitivity of acetylcholinesterase to inhibition by malaoxon between the 2 strains. Because MCE was not elevated in the resistant strain, the weak malathion resistance in H. hebetor may result from a different mechanism compared with that hypothesized for some insect species in which reduced general esterase activity is accompanied by an elevated MCE. Decreased esterase activity in the resistant strain suggested that null alleles of some esterases were associated with the resistance. Indeed, E1 and E2, major esterases in the susceptible strain, were not present in the resistant strain on polyacrylamide gels that were stained for esterase activity using the model substrate 1-naphthyl acetate. In contrast, the activity of esterase E3 on the gels was much higher in the resistant strain as compared with that of the susceptible strain. These findings indicate that malathion resistance in H. hebetor is associated with both an increased activity of the esterase E3 and null alleles of the esterases E1 and E2.

The toxicity of imidacloprid to the cereal leaf beetle, Oulema melanopus (L.), was measured under laboratory and field conditions. Insect mortality and plant damage were determined from artificial and natural infestations of O. melanopus applied to various growth stages of barley. All rates of imidacloprid formulated and applied as a seed treatment caused >90% mortality to cereal leaf beetle larvae when barley was infested with eggs at the 4-leaf stage, but were ineffective when barley was infested with eggs at the early tillering or flag-leaf stages of barley. This window of susceptibility influenced results obtained in field trials where peak larval emergence did not occur until the early tillering stage of barley. The resulting mortality in plants from treated seeds never exceeded 40% in the field. Foliar imidacloprid, however, caused >90% mortality in the field, and may be another option in the management of the cereal leaf beetle.

The essential oil of Artemisia annua L. was tested for its toxic repellent and development inhibitory activities against 2 economically important stored product insects: Tribolium castaneum (Herbst) and Callosobruchus maculatus (L.). Adult beetles of T. castaneum were repelled significantly by oil of A. annua at 1% concentration (vol:vol) and above in filter paper arena test. Dose–response relationship of A. annua oil revealed a significant negative correlation between larval survival; pupal survival and adult emergence of T. castaneum (i.e., increase in dose caused decrease in survival and adult emergence). Effective concentration (EC₅₀) to reduce F₁ progeny by 50% was calculated to be 2.6 and 4.1 μl/ml solvent against both the insect species, C. maculatus and T. castaneum, respectively. The relationship between bioactivity of oil from A. annua and responses of T. castaneum and C. maculatus is discussed. We found that oil from A. annua was largely responsible for both repellent (behavioral) and toxic (physiological) actions on 2 species of insect tested.

Japanese beetle, Popillia japonica Newman is a major pest of turf and ornamentals. Laboratory bioassays were conducted to evaluate the potential interactions between a biological control agent, Heterorhabditis marelatus (Nematoda: Heterorhabditidae) IN strain and the insecticide halofenozide against both overwintered and nonoverwintered 3rd instars of Japanese beetle. Treatments consisted of all combinations of 2 rates of halofenozid with H. marelatus nematodes Imidacloprid was used as a standard. Percentage larval mortality was evaluated at 7, 14, and 21 d after treatment. No deleterious effects were observed. The nematode treatments generally produced significantly greater larval mortality relative to both chemical treatments. Twenty-one days after treatment, both rates of nematodes resulted in 100% mortality, whereas insecticide treatments did not surpass 60% mortality. No synergism was detected in any of the combination treatments. There were no significant differences in nematode reproduction in larvae exposed to halofenozide and nematodes versus larvae exposed to only nematodes.

Of ≈18,200 ha planted to sugarcane in south Texas, only ≈80 ha (<0.5%) are treated with insecticides because this type of control is widely regarded as ineffective against stalkboring pyralids, the key pests of sugarcane. Therefore, nonchemical control measures, such as resistant varieties and biological controls, must be evaluated to mitigate the losses caused by stalkborers. We performed laboratory and field evaluations on the use of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) (strain GHA) against the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Pyralidae), which causes damage in south Texas estimated at between $10 and $20 million annually. We also performed bioassays against the sugarcane borer, Diatraea saccharalis (F.) (Pyralidae), the key pest in other sugarcane growing areas. In the bioassays, E. loftini was substantially more susceptible to B. bassiana than D. saccharalis, based on both 5-d LD₅₀ values and survival times. A commercial oil-based formulation of B. bassiana was evaluated in the field using the following treatments: oil alone (control), B. bassiana oil, and B. bassiana Silwet L-77 carrier at an application rate of 5 × 10¹³ spores per hectare. Neither numbers of E. loftini per stalk, nor stalk damage (≈20% bored internodes) were significantly affected by treatment. The application of B. bassiana Silwet significantly affected the numbers of internodes showing high damage, but not those with low or medium damage. Analysis of yield data and juice quality showed no significant treatment effects. We conclude that the application of Beauveria Silwet offers the best chances for reducing damage caused by E. loftini of those treatments tested. However, reductions in insect incidence or damage did not result in measurable increases in yield or sugar quality, probably because of insufficient coverage. Effective control of stalkboring pyralids in sugarcane using B. bassiana will likely require improvements in delivery technology.

The effect of Metarhizium anisopliae (Metschnikoff) Sorokin strain ESC-1 alone and in combination with sublethal doses of commercial formulations of chlorpyrifos, propetamphos and cyfluthrin on mortality of CSMA strain of German cockroach, Blattella germanica (L.), was determined by conducting in vivo studies that included 3 bioassays. Spores of M. anisopliae cultured on SDAY media had germination of >90%. Based on bioassay 1, doses ranging from 0.5 to 300 ppm of chlorpyrifos and propetamphos, and 0.05 to 40 ppm of cyfluthrin were selected for bioassays 2 and 3. Cockroach mortality ranged from 5 to 20% for insecticides alone and 48 to 70% for insecticides M. anisopliae in bioassay 2. In bioassay 3, mortality ranged from 15 to 60% for insecticides and 57.5 to 92.5% for insecticides M. anisopliae. Percentage of cockroach mortality resulting from insecticide M. anisopliae combinations was significantly higher than insecticide alone. Mortality was also significantly higher in certain insecticide M. anisopliae combinations than M. anisopliae alone. There was no significant interaction between M. anisopliae and insecticides with their concentrations in bioassay 2, indicating an additive effect. But in bioassay 3, a significant interaction was observed when M. anisopliae was combined with multiple insecticide concentrations. The interaction indicated an additive effect for chlorpyrifos and cyfluthrin, and a synergistic effect for propetamphos. There were significant differences in LT₅₀ among various treatment combinations. M. anisopliae alone or insecticide M. anisopliae combinations did not affect body weight in treated German cockroaches.

We tested biological control agents for the control of 3rd-instar scarab turfgrass pests, both for the masked chafer Cyclocephala hirta LeConte and the Japanese beetle, Popillia japonica Newman. The former species is endemic in California whereas the latter, although not yet established, constitutes a permanent serious threat to agriculture and horticulture in California. We conducted experiments using C. hirta in California and P. japonica in New Jersey. A field trial conducted in 2 different California turfgrass sites compared the field persistence in the absence of hosts of Bacillus thuringiensis Berliner subspecies japonensis Buibui strain, the milky disease bacterium, Paenibacillus (= Bacillus) popilliae (Dutky), and the entomopathogenic nematodes Steinernema kushidai Mamiya and Heterorhabditis bacteriophora Poinar to that of the organophosphate diazinon. Soil samples taken 0–70 d after applications were bio-assayed with P. japonica. Only diazinon and the entomopathogenic nematode S. kushidai caused substantial mortality and S. kushidai activity persisted significantly longer than diazinon activity. In greenhouse experiments, combinations of entomopathogenic nematode species usually resulted in additive mortality of scarab larvae. Combinations of S. kushidai and diazinon also resulted in additive mortality. In field trials, the efficacy of H. bacteriophora and especially S. kushidai and S. glaseri, was comparable to that of diazinon over 14–18 d. However, it is likely that at least S. kushidai would have outperformed diazinon over an extended period because of its longer persistence and potential for recycling in the hosts. S. kushidai, should it become commercially available, deserves further examination as an alternative to chemical white grub control especially as a highly compatible component of sustainable turfgrass management.

Methyl eugenol (4-allyl-1,2-dimethoxybenzene-carboxylate) and cue-lure [4-(p-acetoxyphenyl)-2-butanone] are highly attractive kairomone lures to oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, B. cucurbitae (Coquillett), respectively. Plastic bucket traps were evaluated as dispensers for methyl eugenol and cue-lure for suppression of the 2 fruit flies in Hawaii. Methyl eugenol and cue-lure mixtures were compared with pure methyl eugenol or cue-lure over 4 seasons. B. dorsalis captures differed significantly with treatment and season. B. dorsalis captures with 100% methyl-eugenol were significantly greater than all other treatments (25, 50, and 75%). B. cucurbitae captures also differed significantly with treatment but not with season. Captures with 100, 75, and 50% cue-lure were not significantly different. Bucket traps baited with cue-lure ( malathion) and weathered under Hawaiian climatic conditions were attractive to B. cucurbitae up to 8 wk. Two methyl eugenol dispensers (canec disks and Min-U-Gel) were compared with bucket traps. Dispensers (methyl eugenol malathion) were weathered for 2–16 wk under Hawaiian climatic conditions and bioassayed during summer and winter. Initially, captures of B. dorsalis were not significantly different for the 3 dispensers. Bucket traps and canec disks were most resistant to weather, remaining attractive to B. dorsalis flies up to 16 wk. Min-U-Gel was least resistant, losing attractiveness to B. dorsalis flies within 2 wk. On the basis of performance, bucket traps and canec disks were equally long-lived up to 14 wk; thereafter, bucket traps were slightly more attractive during winter. Canec disks were cheapest, but on the basis of possible environmental concerns, bucket traps may be the best all-around choice for areawide suppression of fruit flies.

Graphocephala atropunctata (Signoret) is the principal vector of Xylella fastidiosa (Wells, Raju, Hung, Weisberg, Mandelco-Paul and Brenner), the bacterium that causes Pierce’s disease of grapevine in coastal California. Monitoring the activity of G. atropunctata in the early spring is important for timing insecticide sprays and assessing the potential for disease spread to adjacent vineyards. Trapping studies with yellow sticky traps over 3 yr in Napa Valley, CA, established a significant correlation between early spring trap catch and temperature. Sticky trap catches of G. atropunctata occurred in the springs of 1996–1998 only when temperature was greater than or equal to 14.5°C. In 1997 and 1998, the degree-hours (>14.5°C) per day from sunrise to sunset during March and April, but not in May, correlated significantly with trap catches. The temperature threshold of 14.5°C in the early spring can be used to improve the timing of insecticidal applications aimed at reducing G. atropunctata populations in vineyards affected by Pierce’s disease.

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.

Significant numbers of 3 pest species of noctuid moths were captured in traps baited with acetic acid, 3-methyl-1-butanol, and 3-methyl-1-pentanol. These were Lacanobia subjuncta (Grote & Robinson); Mamestra configurata Walker, bertha armyworm; and Xestia c-nigrum (L.), spotted cutworm. The combination of acetic acid and 3-methyl-1-butanol was superior to the individual chemicals in attracting all 3 species, whereas the combination of acetic acid and 3-methyl-1-pentanol was superior to the individual chemicals in attracting X. c-nigrum. For the 3 species of moths, numbers captured were similar in traps baited with the combination of acetic acid and 3-methyl-1-butanol or acetic acid and 3-methyl-1-pentanol. Traps baited with these attractants captured both males and females at a ratio near 1:1.

Methanol extracts of German cockroach, Blattella germanica (L.), fecal pellets have limited use as pheromone attractants in the urban environment because of their unpleasant color and odor. To eliminate these characteristics, a novel aqueous extract of German cockroach feces was formulated. Fecal material was extracted with methylene chloride and mixed with water. The aqueous phase of the extract was colorless and relatively odorless compared with methanol fecal extracts. Aqueous extract was bioassayed and compared with methanol extracts for aggregation activity. The efficacy of chlorpyrifos and boric acid formulations was tested with and without the addition of fecal extracts. In tests with chlorpyrifos, the addition of the aqueous extract produced significantly greater mortality in young nymphs than either chlorpyrifos alone or chlorpyrifos methanol extract. There were no differences in mortality between the 2 extract boric acid treatments during the test period, and both enhanced mortality.

An experimental 2.15% imidacloprid gel bait containing ≈44% water was evaluated in laboratory and field studies against the German cockroach, Blattella germanica (L.). In continuous exposure tests, toxicity and presumably bait consumption varied with cockroach stage, deprivation of competitive food, and temperature. The LT₅₀ values for cockroaches provided with competitive food ranged from ≈0.9 h for adult females to 190 h for small nymphs. The LT₅₀s for cockroaches not provided competitive food ranged from ≈1.7 h for adult females to ≈31 h for adult males. The LT₅₀s decreased exponentially with temperature between 10 and 30°C. Even though the bait was significantly more repellent (≈38%) than an untreated control (≈14%) when tested in Ebeling choice boxes, performance index values were positive and increased to nearly 100 (indicating high mortality and low repellency) after 14 d. When applied at 15–45 g per kitchen, the bait significantly reduced German cockroach trap catch in infested homes during a 4-wk period. There was a ≈50% reduction after 1 wk and ≈80% reduction 4 wk after treatment.

We investigated whether the Argentine ant, Linepithema humile (Mayr), trail pheromone, Z9–16:Ald, could enhance recruitment to and consumption of liquid sucrose solutions. All tests were done as paired comparisons with a 10% sucrose solution as food. In the laboratory, mixing 20 μl of a 10-μg/ml solution of the pheromone with 50 μl of the 10% sucrose solution increased the number of ants feeding by >150%. In a field test, we combined the trail pheromone with a 10% sucrose solution in 50-ml vials. These vials were covered with a plastic membrane that has 1.5-mm-diameter holes punched uniformly across its surface. Ants could drink from the holes after the vials were inverted. For half of the vials, 1 μg of the pheromone was put onto the plastic membrane before the vials were filled with a 10% sucrose solution. The remaining vials had no pheromone on the plastic membrane. After 4 h we measured the consumption in each vial. Bait consumption with the pheromone was enhanced by 29%. In a 2nd series of tests, vials were left outside for 24 h. The consumption rate was 33% higher with the pheromone compared with the controls that didn’t have pheromone.

An area-wide integrated tsetse eradication project was initiated in Zanzibar in 1994 by the International Atomic Energy Agency and the governments of Tanzania and Zanzibar, to eradicate Glossina austeni Newstead from Unguja Island (Zanzibar) using the sterile insect technique. Suppression of the tsetse population on Unguja was initiated in 1988 by applying residual pyrethroids as a pour-on formulation to livestock and by the deployment of insecticide impregnated screens in some of the forested areas. This was followed by sequential releases of gamma-sterilized male flies by light aircraft. The flies, packaged in carton release containers, were dispersed twice a week along specific flight lines separated by a distance of 1–2 km. More than 8.5 million sterile male flies were released by air from August 1994 to December 1997. A sterile to indigenous male ratio of >50:1 was obtained in mid-1995 and it increased to >100:1 by the end of 1995. As a consequence the proportion of sampled young females (1–2 ovulations), with an egg in utero in embryonic arrest or an uterus empty as a result of expulsion of a dead embryo, increased from <25% in the 1st quarter to >70% in the last quarter of 1995. In addition, the age structure of the female population became significantly distorted in favor of old flies (≥4 ovulations) by the end of 1995. The apparent density of the indigenous fly population declined rapidly in the last quarter of 1995, followed by a population crash in the beginning of 1996. The last trapped indigenous male and female flies were found in weeks 32 and 36, 1996, respectively. Time for 6 fly generations elapsed between the last catch of an indigenous fly and the end of the sterile male releases in December 1997.

Field studies were conducted to characterize the yield responses of pumpkin, Cucurbita pepo L., and winter squash, Cucurbita maxima Duch., to simulated striped cucumber beetle, Acalymma vittatum (F.), feeding damage. Preliminary studies in pumpkin (‘Spookie’) were conducted in 1993, and more complete studies in 1994 and 1995 in pumpkin (Spookie), and in 1995 and 1996 in winter squash (‘Waltham’). Plants were artificially injured 1 time at the cotyledon, 1st, 2nd, or 3rd true leaf stages by clipping specified percentages of leaf area from all leaves on the plant. Treatments consisted of a control treatment with no simulated injury and 4 levels of simulated injury. Pumpkin treatments were 10, 20, 40, and 80% leaf area removal in 1993 and 1994 and 20, 40, 60, and 80% in 1995. Winter squash treatments were 20, 40, 60, and 80% leaf area removal in 1995, and 10, 20, 40, and 80% in 1996. In 1993, 5 wk after planting, mean leaf, stem, and total dry weight were significantly lower on pumpkin plants subjected to ≥20% simulated leaf injury regardless of the growth stage when the injury occurred. Injury at the 3rd leaf stage resulted in a significant reduction in the mean leaf and total dry weight of plant, across all levels of injury. At 2–3 wk before crop maturity, fruit weight and number of fruit per plant were significantly lower with 80% leaf area removal. In 1994 and 1995, and when pumpkins were grown to full maturity and apparently able to compensate for the simulated damage, neither number nor weight of marketable fruit per plant were affected significantly by simulated injury at any stage of development nor level of simulated injury. In contrast, ≥20% and 80% leaf area removal to winter squash resulted in significant reductions in the weight of marketable fruit and/or number of marketable fruit, in 1995 and 1996, respectively. The results of this study indicate that pumpkins can tolerate relatively high levels of simulated defoliation, whereas winter squash is less tolerant. Variable results across years in winter squash may indicate an interaction between injury and plant stress caused by abiotic factors such as soil moisture availability.

A survey using modified azalea stems was used to establish a “tally threshold value” for assessing azalea lace bug, Stephanitis pyrioides (Scott), feeding injury to azalea shrubs. Consumers and green-industry professionals, represented by ornamental growers, landscape architects, and landscape managers, recognized azalea lace bug injury when injured leaf area exceeded 2%. Purchase and treatment decisions of professionals and consumers were evaluated by surveying responses to Rhododendron indica variety alba ‘Delaware Valley White’ azaleas representing a range of damage. Survey participants also provided a brief biographical background and answers to questions regarding pesticide use, ability to identify diseases, pests, and beneficial organisms, and willingness to consider pesticide alternatives. Professionals and consumers expressed a strong interest in limiting urban pesticide use. The 2 groups indicated a hypothetically acceptable level of 6–10% plant damage by arthropod pests. A 2% injury threshold was used to determine the level of proportional damage (the percentage of leaves displaying 2% or more lace bug leaf feeding injury) resulting in either the rejection of plant purchase or initiation of treatment. A nonlinear curve was fit to treatment and no-purchase responses of professionals and consumers using a modified 3-parameter Mitscherlich nonlinear growth function. Half of the surveyed professionals and consumers indicated that damage proportions >10% (1.03% actual injury) were sufficient to reject an azalea for purchase. Proportional damage levels >43% (3.3% actual injury) would be necessary to prompt 50% of the respondents to initiate treatment of damaged azaleas to control lace bugs.

Colorado potato beetle, Leptinotarsa decemlineata (Say), feeding, development, and survival to adulthood were examined after continuously exposing large larvae to Bacillus thuringiensis subsp. tenebrionis-treated potato foliage from the field. In laboratory assays, the overall consumption and the length of period to become prepupae were determined for larvae, which began as 3rd and 4th instars, that were offered potato leaf disks with naturally declining levels of B. thuringiensis residue. In small-cage field experiments, survival to adulthood and the period to adult emergence for beetles confined to potato plants treated with B. thuringiensis beginning as 3rd and 4th instars also were examined. Third instars remaining on plants after a B. thuringiensis application were unlikely to feed and 4th instars consumed only ≈50% as much foliage as those fed untreated foliage. Many late instars subjected to B. thuringiensis-treated foliage failed to survive to adulthood; 58–83% of these beetles died during the larval stage. Reduced feeding and poor survival of late instars suggest that counts of large larvae after application do not provide a complete picture of the efficacy of the B. thuringiensis treatment. Late instar Colorado potato beetles that were exposed continually to naturally declining levels of B. thuringiensis-treated potato foliage took an average of 1.8–4.5 d longer to become prepupae and 4–8 d longer to emerge as adults compared with those provided with untreated foliage. Delayed emergence of adults that fed on B. thuringiensis-treated potatoes as late instars indicated that development was prolonged in these insects because of ingestion of a sublethal dose of B. thuringiensis.

The responses of tufted apple bud moth, Platynota idaeusalis (Walker), the leafroller P. flavedana Clemens, redbanded leafroller, Argyrotaenia velutinana (Walker), and obliquebanded leafroller, Choristoneura rosaceana (Harris), to the pheromone blends of each, as well as to 3 putative generic blends (two- and three-component blends containing pheromone elements of each of the 4 species) were evaluated in small orchard plots. P. idaeusalis and P. flavedana, and A. velutinana and C. rosaceana comprise 2 pairs of species, each pair with broad overlap in pheromone blend, and quite different from one another. Each generic blend suppressed trap captures of all 4 species. The blends for P. idaeusalis and P. flavedana each reduced captures for these species. Furthermore, the blend for P. idaeusalis also suppressed captures of A. velutinana. The P. flavedana blend did not reduce captures of A. velutinana; in fact, at times captures increased. This study determines relative abilities of several sex attractant blends to reduce captures of 4 leafroller species in pheromone traps, presumably reflecting the ability of a blend to reduce orientation of males to females in a large block situation. This is a requisite 1st step in the development of a multispecies mating disruption blend.

The gall wasp Callirhytis cornigera (Osten Sacken) is a cynipid with alternating generations that produce large, woody stem galls and tiny blister-like leaf galls on pin oak, Quercus palustris Muenchhausen, in the United States. We tested 3 approaches to control the leaf-galling generation, and determined their impact on associated parasitoids and effectiveness in reducing numbers of new stem galls. First, trees were sprayed with bifenthrin or chlorpyrifos in late March to kill females emerging from stem galls before they oviposited into buds. Second, concentrated solutions of abamectin, imidacloprid, or bidrin were injected from pressurized containers into tree sapwood to control larvae developing in young leaf galls. Finally, systemic insecticides (acephate, abamectin, dimethoate, or imidacloprid) were sprayed at early leaf expansion (2 May) or to young, expanded leaves (17 May) to target larvae in leaf galls. Parasitoids, mostly eulophids, accounted for ≈70% mortality of leaf-galling C. cornigera larvae on untreated trees. Whole-canopy sprays during C. cornigera emergence from stem galls reduced overall numbers of galled leaves and leaf galls. Trunk injections of bidrin or abamectin resulted in significant mortality of gall inhabitants, including parasitoids. However, neither of the aforementioned approaches significantly reduced numbers of new stem galls. Sprays of abamectin, dimethoate, or imidacloprid applied on 2 May caused high mortality of all gall inhabitants. There was no net benefit, however, because parasitism caused a similar reduction in C. cornigera survival on unsprayed shoots. Sprays applied later in leaf expansion had little impact on gall inhabitants. Of the treatments tested, bifenthrin sprays at bud break provided the greatest reduction in new leaf galls, whereas bidrin injections provided the greatest reduction in gall wasps emerging from galled leaves. This study suggests that gall wasp outbreaks are unlikely to be controlled by a single treatment, regardless of application method.