Elevated CO₂ concentrations can increase plant growth and change plant nutritive value for herbivores. Several reports indicate that leaf-chewing insects consume more foliage of plants grown at elevated CO₂ concentrations than of plants grown at ambient CO₂. Research with additional plant–pest systems is needed to determine if this phenomenon is widespread and if increased insect feeding might affect productivity. Effects of CO₂ enrichment on foliar consumption and population size of Western flower thrips [Frankliniella occidentalis (Pergande)]) were measured on white clover (Trifolium repens L.). White clover infested with thrips was exposed for 24 h/d to ≈396 (ambient) or 745 μLL⁻¹ (elevated) CO₂ for up to 35 d in 10 greenhouse exposure chambers. At elevated CO₂, clover shoot weight and laminae weight were ≈50% greater, and laminar area was ≈20% greater than at ambient CO₂. Thrips population size was not significantly affected by CO₂, but laminar area scarred by thrips feeding was ≈90% greater at elevated than at ambient CO₂. Because of increased growth, however, undamaged leaf area was approximately 15% greater at elevated than at ambient CO₂.

Functional responses and superparasitism by the indigenous parasitoid wasp Lysiphlebus testaceipes Cresson (Hymenoptera: Aphidiidae) and the introduced parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae) on the greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae), were measured at four temperatures (14, 18, 22, and 26°C) during a 24-h period (12:12 L:D). At each temperature, 5–75 greenbugs were exposed to individual wasp mating pairs for 24 h. At all experimental temperatures, functional responses for both wasps most closely fit the type III model. Instantaneous attack rates (a) for A. colemani were not significantly different among experimental temperatures. However, for L. testaceipes, the estimate for a at 14°C was significantly lower than estimates at 22 and 26°C when data were fit to a type II functional response model. When data were fit to a type III functional response model for L. testaceipes, the estimate for a at 14°C was significantly lower than estimates at 18, 22, and 26°C. Superparasitism for both wasps was often less than expected if superparasitism were a random occurrence, suggesting that these parasitoids may be able to sense when the host has been previously parasitized. A. colemani achieved higher parasitism rates than L. testaceipes at lower temperatures. This observations suggests that A. colemani may be an effective addition to the parasitoid guild for biological control of the greenbug during cooler periods in the Southern Great Plains.

Field experiments were conducted in 1997 and 1998 to understand the physiological responses of soybean, Glycine max (L.) Merrill, to injury from two-spotted spider mite, Tetranychus urticae Koch, and to examine the contribution of soil moisture toward soybean tolerance to spider mite injury. A split-plot treatment design was used consisting of moisture stress as the main plot and spider mite injury as the sub-plot treatments in a randomized complete block design with eight replications. Soybeans were moisture-stressed beginning approximately at V10 growth stage, and spider mites were maintained on soybeans for 10 d, and then physiological responses of soybean were determined. Moisture-stressed soybeans had lower leaf water potentials, photosynthetic rates, stomatal conductances, and transpiration rates. Spider mite injury also caused a significant reduction in photosynthesis, stomatal conductance, transpiration, and chlorophyll content. The lack of a significant impact of spider mite injury on chlorophyll fluorescence and similar light curves, at low light intensities, of soybean leaves with and without spider mite injury, suggest that spider mite injury does not interfere with the light reaction center at the initial stage of photosynthesis. Despite measurable reductions in total chlorophyll content from mite injury, fluorescence data and light curves strongly indicate photosynthetic rate reductions from mite injury were not immediately associated with chlorophyll loss or effects on photosynthetic electron transport. There were significant interactions between moisture stress and spider mite injury for some gas-exchange parameters. Photosynthetic rate reductions by spider mites were greater in moisture-unstressed than stressed soybeans. Superimposing spider mite injury did not reduce photosynthetic rates greatly in moisture-stressed soybeans because of an initially low photosynthetic rate from moisture stress. However, comparison of absolute photosynthetic rates of spider mite-injured soybean leaves with and without moisture stress suggested that soil moisture improved soybean tolerance to spider mite injury.

We investigated the effects of temperature and food sources on the longevity of Apanteles galleriae Wilkinson (Hymenoptera: Braconidae), a koinobiont solitary larval endoparasitoid reared on Achroia grisella F. (Lepidoptera: Pyralidae). Adults were supplied with one of the seven food types (comb without honey; pure honey; 50%, 30%, or 10% honey solutions; glycerin; or water) or kept water- and food-deprived at each temperature (0, 10, 20, 30, 40°C). Adult parasitoids provided with honey solutions lived the longest at 10°C. Maximum mean longevity was 47.1 and 42.0 d for males and females, respectively, fed on 30% honey solution at 10°C. Longevity of adults did not differ markedly by sex at each temperature across all food treatments. Longevity of females fed a honey solution was slightly but not significantly shorter than males at optimal temperatures (10 and 20°C). However, females provided comb without honey or kept food- and water-deprived lived significantly longer than males. Our results may be of value for biological control applications and in developing mass rearing techniques for A. galleriae.

Temperature and seasonal effects on foraging activity of Solenopsis invicta Buren (red imported fire ant) in Oklahoma were investigated by periodically quantifying the number of ants captured in baited vials for 2 yr. All temperature parameters (soil surface, 2 cm, 15 cm, mound surface, mound 5 cm deep, and mound 10 cm deep) except ambient at 1 m above soil surface were significant predictors of foraging activity; soil temperature at 15 cm was the best individual predictor, explaining 34% of variability in foraging activity. A combined quadratic model including mound surface temperature and season (weeks) explained 63% of the variability in foraging activity. Comparison with a similar study conducted in Florida revealed differences in the percentage of the year favorable for maximal foraging (≈25% in Oklahoma versus 42–59% in Florida). These data suggest that recommendations for timing of insecticidal bait applications against S. invicta that are appropriate in more southern portions of the fire ant range may not be appropriate for Oklahoma.

The cottonwood leaf beetle, Chrysomela scripta F., is a serious defoliator of plantation Populus in the United States. Current control methods include biorational and synthetic chemicals as well as selecting Populus clones resistant or tolerant to C. scripta defoliation. Specific ratios of long-chain fatty alcohols to alpha-tocopherylquinone (α-TQ) on the leaf surface of Populus spp. act as phagostimulants to adult C. scripta. The chemical concentrations and ratios vary among Populus clones; however, the effect of defoliation on the subsequent production of these chemicals is unknown. We investigated the effects of defoliation, clone, and season on Populus leaf surface chemical production. Chemical concentrations and ratios were monitored in 1998 and 1999 on eight Populus clones with and without larval C. scripta defoliation. Chemicals were extracted from the leaf surface and analyzed via gas chromatography. Larval C. scripta defoliation rarely caused changes in leaf surface chemistry at the defoliation levels tested; however, the production of these phagostimulants did vary by clone and season. Foliar alcohol and α-TQ concentrations and α-TQ:total alcohol ratios differed significantly among clones. Furthermore, α-TQ concentrations and α-TQ:total alcohol ratios varied temporally in some, but not all, clones. In general, foliar alcohol and α-TQ concentrations either did not vary or increased, but α-TQ:total alcohol ratios declined throughout the growing season. This research illustrates that the production of leaf surface phagostimulants is not a function of defoliation, but is most likely controlled by genetic and physiologic processes. Additionally, because Populus clones vary in their foliar chemistry, this variation could be exploited in tree breeding programs.

Both defensive and nutritional hypotheses have been used to explain the improved performance of sucking insects on variegated plants. With portions of leaves unable to photosynthesize, variegated plants are likely to have less carbon assimilate to allocate to the production of defensive compounds than green plants. Alternatively, like plants grown in the shade, improved response of sucking insects on variegated plants may be caused by greater mobility of amino acid nitrogen and carbohydrates in the phloem to fuel compensatory production of leaves. We examined amino acid and sucrose content of stem exudate collected from red-variegated, yellow-variegated, and green-leafed coleus plants, Solenostemon scutellarioides (L.) Codd, and their relation to life history characteristics of citrus mealybug, Planococcus citri (Risso), to test these defensive and nutritional hypotheses. Although higher concentrations of both total amino acids and sucrose were found in green- and red-leaved plants, these quantitative measures were uncorrelated with life history parameters of mealybugs. In contrast, our analysis of qualitative measures of amino acid composition supported both defensive and nutritional hypotheses. Green-leafed plants had the greatest levels of shikimic acid precursors and lowest levels of other nonessential amino acids. Life history characteristics of citrus mealybugs were correlated negatively with increasing proportions of shikimic acid precursors and positively with increasing proportions of other nonessential amino acids. Thus, our studies of life history and stem chemistry indicate that improved suitability of variegated plants is consistent with both carbon- and nutrient-based theories of plant defense.

The total and relative amounts of (Z)-11-tetradecenyl acetate (Z11-14:Ac), (E)-11-tetradecenyl acetate (E11-14:Ac), (Z)-11-tetradecen-1-ol (Z11-14:OH) and (Z)-11-tetradecenal (Z11-14:Al), and the EAG response of male antennae to these pheromone gland compounds were compared in laboratory reared Choristoneura rosaceana Harris (Lepidoptera: Tortricidae) from British Columbia, Michigan, Ontario, New York, and Quebec. A field trapping experiment was conducted in each of these locations to determine the effect of Z11-14:Al on the numbers of moths captured. The amount of each of the four pheromone-gland compounds declined successively in moths from British Columbia, Quebec, Ontario, Michigan, and New York. The relative amount of Z11-14:Ac was greatest in moths from New York and smallest in moths from Ontario, whereas the relative amount of E11-14:Ac was greatest in moths from Ontario and smallest in moths from British Columbia. Moths from Ontario, Quebec, British Columbia, Michigan, and New York contained decreasing relative amounts of Z11-14:OH and Z11-14:Al. There was a trend of increasing antennal sensitivity to each of the four pheromone-gland compounds in moths from New York, Michigan, Ontario, Quebec, and British Columbia. The addition of 1% Z11:Al to a three compound blend of Z11-14:Ac, E11-14:Ac and Z11-14:OH (97:2:1) resulted in a >twofold increase in average trap catch in British Columbia, Ontario, and Quebec; this compound had no effect on trap catch in Michigan or New York.

Alternative methods for controlling Douglas-fir beetles, Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), were examined in terms of the number of beetles removed from a population and in terms of beetle flight activity near treated sites. Methods that were tested included pheromone-baited Lindgren funnel traps, standing, continuously pheromone-baited trees, standing, temporarily pheromone-baited trees with bait removed after beetles began invading the tree, and single felled trees. Funnel traps captured more than twice the number of beetles over the flight season than a baited or felled trees. The tree methods did not differ from each other in the number of beetles captured. Trees in all three methods became saturated within the first 20–30 d of flight. Baited traps continued to catch beetles during the whole test period. Beetle flight remained active around continuously baited trees even after beetle attacks ceased. Beetle flight around temporarily baited trees ceased after the trees became saturated. Density of beetles per tree did not differ between different sized decks of felled trees. Large decks (with 9 to 12 trees) absorbed three times the beetles than small decks (with 3 to 4 trees), and nine times as many as did single felled trees. Spillover to neighboring trees from baited trees or traps is minimized when baits are removed after initial attacks. A tree deck of three or four felled trees of DBH ≈40 cm is equivalent to one trap in terms of the number of beetles removed. Trees in a deck become saturated within the same time span as trees in the other methods. Single felled trees or decks produce no spillover into the neighboring stand.

Laboratory and field bioassays were conducted to determine whether adults of the cactus weevil, Metamasius spinolae (Gyllenhal), produce attractant compounds. The attraction of males in a dual choice olfactometer to male volatiles combined with volatiles of prickly pear, Opuntia ficus indica (L.), was greater than attraction of males to females or to host volatiles alone. Response of weevils to female volatiles alone or in combination with prickly pear was not different from response to controls. In field tests using pitfall traps baited with live male or female weevils in covered cages, significantly more females responded to traps baited with males than to traps baited with females or controls. Attractancy responses in laboratory and field studies suggest that a male-produced aggregation pheromone is the prevalent mechanism of chemical communication among cactus weevils. This study is the first report of such a pheromone system for this tropical species.

The Angoumois grain moth, Sitotroga cerealella (Oliver), is one of the major storage pests of cereals, and no antibiotic resistance in wheat against this insect has been identified to date. Midgut proteases are vital to insects that digest food in the midgut and have been considered as targets for the control of insect pests. Protease inhibitors are attractive for their potential use in developing insect-resistant plant varieties via genetic engineering. Characterization of the midgut proteases of S. cerealella larvae revealed the major digestive proteases were trypsin-like and α-chymotrypsin-like serine proteases. The partial inhibition of proteolytic activity by pepstatin A, however, suggested the presence of another protease in the midgut sensitive to this inhibitor. The potential value of naturally occurring plant protease inhibitors as resistance factors for S. cerealella was assessed in bioassays using artificial seeds prepared by freeze-drying a flour paste in Teflon molds and then coating the seeds with gelatin. Soybean trypsin inhibitor (Kunitz inhibitor) had an adverse effect on the development of the insect and suggested a protease inhibitor might serve as a transgenic resistance factor. To evaluate the potential value of seed resistance in conjunction with an egg parasitoid on S. cerealella population dynamics a predictive model was developed. The model was directed toward grain storage in developing countries. While the model was hypothetical, outputs supported the use of resistant seed in conjunction with parasitoids to control the population growth of S. cerealella in a small seed storage room.

Seasonal dispersal and diversity of aphid species were monitored on pepper farms in St. Catherine, Jamaica throughout 1998 and 1999 to identify the most likely vectors of tobacco etch virus (TEV) in pepper fields. Flight activity was monitored weekly on five farms using water pan traps. More than 30 aphid species were identified, 12 of which are new records for Jamaica. Ninety-two percent of the aphids captured from October 1998 through July 1999 belonged to only seven of the >30 species identified. Of these seven species, Aphis gossypii Glover and those in the Uroleucon ambrosiae (Thomas) complex comprised more than two-thirds of the total. Five known vectors of TEV were captured: A. gossypii, Aphis craccivora Koch, Aphis spiraecola Patch, Myzus persicae (Sulzer), and Lipaphis pseudobrassicae Davis. Generally, more aphids were collected from mid-September through mid-May than from mid-May through mid-September. The influence that rainfall and temperature had on periods of aphid flight activity also was investigated. Results indicated that flight of some species increased 3–4 wk after a rainfall event, whereas temperature did not appear to affect flight activity. High populations of A. gossypii as well as the presence of four additional known TEV vectors were encountered in October and November, which is the period that significant acreage is transplanted to pepper for harvest to coincide with the winter export market. Because pepper is most vulnerable to yield loss when young plants become infected with TEV, pepper production in Jamaica may be threatened if commonly abundant species such as A. gossypii are carrying TEV. Based on this information, implications for management of pepper viruses and their aphid vectors in Jamaica are discussed.

There is little quantitative information on relationships between insect attacks and fire damage for ponderosa pine, Pinus ponderosa Douglas ex Lawson, in the southwestern United States. Tree mortality and insect attacks were measured on 1,367 trees for three years after a spring wildfire (4 May 1996), a summer wildfire (20 June 1996), and a fall prescribed fire (9 September 1995) in northern Arizona. Western pine beetle, Dendroctonus brevicomis LeConte, mountain pine beetle, D. ponderosae Hopkins, roundheaded pine beetle, D. adjunctus Blandford, red turpentine beetle, D. valens LeConte, Ips species, and wood borers in the Buprestidae and Cerambycidae families were found in fire-damaged trees. The most frequently occurring insects, listed from most to least frequent, were wood borers, red turpentine beetle, Ips spp., western pine beetle, roundheaded pine beetle, and mountain pine beetle. Trees attacked by Dendroctonus and Ips spp. as a group had more crown damage from fire than unattacked trees. The percentage of trees attacked by Dendroctonus and Ips species was lowest during the fall fire (11%, 25 of 222 trees), intermediate during the summer fire (19%, 154 of 833 trees), and highest during the spring fire (41%, 127 of 312 trees). More than one-half of all wood borer colonization (58%) and attacks by western pine beetle (68%), roundheaded pine beetle (56%), and Ips spp. (66%) occurred in the first year after the fire. Measures of tree damage from fire and insect attacks were used to develop logistic regression models of tree mortality to quantitatively investigate factors that influenced tree mortality. Tree mortality 3 yr postfire was low until crown damage by fire exceeded 70–80% for unattacked trees, 40–50% for trees with partial attacks by Dendroctonus and Ips species, and 30–40% for trees with mass attacks. We concluded that several Dendroctonus and Ips species colonize fire-damaged ponderosa pines in northern Arizona and colonization is promoted by heavy crown damage from fire.

Hemlock woolly adelgid, Adelges tsugae Annand, is an exotic forest pest threatening the health of New England’s eastern hemlock, Tsuga canadensis (L.) Carrière. Research indicates that the northern spread of this insect may be slowed or prevented by cold temperature. We conducted laboratory studies to assess the coldhardiness of A. tsugae, collected at sites within plant hardiness zones 5a (Northern), 6a (Central), and 6b (Southern) in January, February, and March. Adelgids were exposed to −15, −20, −25, −30, and −35°C for 2, 4, or 8 h, and comparisons in survival were made with insects held at 0°C. For all months and sites, mortality increased as temperature decreased, and no survival occurred among those from the Central and Southern sites exposed to −30 and −35°C. In January and February, ≤3% of the adelgids collected from the Northern site survived −30°C, and none survived −35°C in January or March. Adelgids from all sites entered the winter with similar levels of coldhardiness, but those from the Central and Southern sites lost their tolerance to cold earlier in the season than those from the Northern site. In January and February, −25°C was a critical temperature at which significant reduction in coldhardiness was observed. Despite the evidence that adelgids in the Northern site possessed greater tolerance to cold temperatures than the other sites, only 14% survived exposure to −15°C in March. In all sites the actual percentage of adelgids that survived after exposure to −15°C decreased 50–60% from January to March. Our results show that adelgid coldhardiness differs depending on geographical location and time of year, and further confirm that cold temperature has a significant impact on their survival.

The oviposition biology of the bertha armyworm, Mamestra configurata Walker, was studied with emphasis on the effect of conspecific eggs on oviposition site selection. Bertha armyworm lay clusters of up to 700 eggs, and larvae have feeding and growth habits similar to those of other Lepidoptera that gain advantages from feeding aggregations. In a field-cage experiment, multiple egg masses per leaf were noted, although the vast majority (85% ) of leaves available for oviposition received no eggs. A series of dual-choice laboratory experiments was conducted using paired excised leaves with and without eggs or egg-wash extracts. Females strongly preferred to oviposit on leaves with eggs of a different female than on leaves without eggs. However, females did not prefer leaves with their own eggs over control leaves without eggs. Gravid females also preferred leaves treated with a methanol egg-wash over leaves treated only with methanol, indicating that the source of oviposition stimulation may be chemically based. The potential relevance of these observations is discussed in the context of host-plant distribution and their exploitation by bertha armyworm.

Pitfall traps were used to compare assemblages of ground beetles (Coleoptera: Carabidae) among treatments of two intercrop trials replicated at each of two sites in each of three years. The first trial comprised canola (Brassica napus L.) and barley (Hordeum vulgare L.) in monoculture and three intercrop treatments of canola and barley. The second trial comprised pea (Pisum sativum L.) and barley in monoculture and three intercrop treatments of pea and barley. Treatment had little effect on species richness. For taxa combined, a significant effect of treatment was detected in 3 of 11 cases, reflecting greater captures of beetles in canola or pea than in barley. Captures of individual taxa were compared among canola or pea versus each of the three intercrops versus barley. For 14 of 15 cases showing significant differences between monocultures, more beetles were captured in canola or pea than in barley. For 12 of 14 cases showing significant differences between monocultures and intercrops, captures of beetles were highest in canola or pea. These cases primarily reflected different captures of Amara spp. and Bembidion spp. across treatments. Results show that under the experimental conditions of the current study in Alberta, Canada, intercropping barley into canola or pea did not increase the activity abundance of populations above that observed in the latter two crops.

Ant richness within 14 Colombian dry forest fragments varies from at least 34–128 species. We have collected the little fire ant, Wasmannia auropunctata (Roger) in each of the fourteen forest fragments, by means of tuna baits, pitfall traps, sampling of logs, understory vegetation and forest litter sampling. A highly significant negative relation was found between the percentage of W. auropunctata samples per forest fragment and richness for the ant community. Additionally, a significant positive relationship was found between the abundance of W. auropunctata and the number of ant-plant associations in nine of the forest fragments. The displacement of other ants by W. auropunctata could be explained in terms of its competitive performance, natural history and ability to exploit disturbed sites. This opportunistic species displays high interspecific aggressiveness, recruiting workers massively to a variety of food resources. It also colonizes different substrates and forms unicolonial societies, which disperse broadly by detaching groups of workers along with multiple queens. The species can be easily monitored with tuna baits, which showed the same significant negative relation. We propose that the abundance of the little fire ant can be used as an indicator of low diversity ant communities in dry forest fragments of the Cauca river valley of Colombia.

The invasive ant, Solenopsis invicta Buren, is a threat to native arthropod biodiversity. We compared areas with naturally varying densities of mostly monogyne S. invicta and examined the association of S. invicta density with three diversity variables: (1) the species richness of ants, (2) the species richness of non-ant arthropods, and (3) the abundance of non-S. invicta ants. Pitfall traps were used to quantify S. invicta density and the three diversity variables; measurement of mound areas provided a complementary measure of S. invicta density. We sampled 45 sites of similar habitat in north central Florida in both the spring and autumn of 2000. We used partial correlations to elucidate the association between S. invicta density and the three diversity variables, extracting the effects of temperature and humidity on foraging activity. Surprisingly, we found moderate positive correlations between S. invicta density and species richness of both ants and non-ant arthropods. Weaker, but usually positive, correlations were found between S. invicta density and the abundance of non-S. invicta ants. A total of 37 ant species, representing 16 genera, were found to coexist with S. invicta over the 45 sites. These results suggest that S. invicta densities as well as the diversities of other ants and arthropods are regulated by common factors (e.g., productivity). Many invaded communities may be more resistant to S. invicta than generally believed, or possess an unexpected resilience for recovery if S. invicta can be permanently suppressed.

Two experiments were conducted testing for lethal and sublethal effects of the transgenic proteins Cry1Ac and chitinase, and the chemical seed and soil treatment imidacloprid on bumble bees (Bombus occidentalis Greene and B. impatiens Cresson, Hymenoptera: Apidae). In the first experiment, B. occidentalis colonies were exposed to realistic residue levels of Cry1Ac, chitinase, and imidacloprid found in pollen. There were no effects on pollen consumption, bumble bee worker weights, colony size, amount of brood, or the number of queens and males produced. In the second experiment, using B. impatiens, we tested the effects of Cry1Ac and two levels of imidacloprid. Similar colony health measures were collected as in the first experiment, but in addition foraging ability of individual bees was tested on complex artificial flowers. There were no differences in colony characteristics among treatments. However, bees in the high-imidacloprid treatment had longer handling times on the complex flowers than bees in the other treatments. No lethal, sublethal colony, or individual foraging effects of these novel pesticides were found at residue levels found in the field, suggesting that bumble bee colonies will not be harmed by proper use of these pesticides. Use of an artificial flower foraging array proved to be a sensitive method for detecting sublethal response of bees to pesticides.

The diversity and abundance of arthropods in feral and cultivated hop, Humulus lupulus L., in the major hop producing area of Canyon Co. in southern Idaho was measured during 2000 and 2001 from leaf and vacuum samples. A total of 133 arthropod species was collected from cultivated and feral hop during the 2-yr study. More species were collected using vacuum than leaf samples, but both methods indicated that feral sites were more diverse than cultivated sites. For leaf samples, the higher diversity of feral sites resulted from greater species evenness in feral than in cultivated sites. For vacuum samples, species evenness was similar, and species richness higher, in feral compared with cultivated sites. Cultivated hop had 5–10 times as many Tetranychus urticae Koch/leaf than feral hop; however, no statistically significant differences in the number of T. urticae/leaf on cultivated and feral hop were detected in either year. Hop plants in feral sites were infested with a greater number of Phorodon humuli (Schrank) in 2000 but not in 2001. The diversity and abundance of phytoseiid predators of T. urticae, did not differ between feral and cultivated hop.

In New York, the primary coccinellid in corn and sweet corn (Zea mays, L.) has historically been Coleomegilla maculata (DeGeer). However, Harmonia axyridis (Pallas) has also been observed the last few years. The objectives of this study were to document the level of establishment of both species in corn and sweet corn and to understand their interactions. The temporal and within-plant distributions of all coccinellids were recorded for 3 yr. The results indicated that H. axyridis and C. maculata were the only abundant coccinellids in corn and sweet corn, with adults and larvae of both species having distinct temporal and within-plant distributions. C. maculata adults were found earlier in the season and lower on the plant than H. axyridis adults. Larvae of both species were often found at the same time and were lower on the plant than their respective adults. Temporal distributions of both species were correlated to crop maturity, aphid density, planting date, and corn type, but not to nearby vegetation. The within-plant locations were correlated to crop maturity, aphid density, planting date, nearby vegetation, and the presence of conspecific coccinellids. While the distribution of each population was unique, some C. maculata and H. axyridis shared time and space, providing the potential for intra-guild predation. An encounter between H. axyridis and C. maculata was most likely to occur when the corn had high aphid populations during pollen shed. These extra-guild food sources minimize intra-guild predation, allowing these two species to co-exist in New York corn and sweet corn fields.

Encarsia transvena is a potentially useful parasitoid of Bemisia tabaci (Gennadius) in India. Development, host preference and parasitism by the parasitoid were studied at 25–30°C and 70–75% RH. Results showed that E. transvena is a solitary, arrhenotokous, heteronomous, autoparasitoid. Female eggs are laid internally in whitefly nymphs and develop as primary parasitoids. Males develop as hyperparasitoids, either on females of their own species or on other primary aphelinid parasitoids. Both sexes have an egg, three larval, a prepupal and pupal stage. Development from egg to adult took 11.3–15.0 d for females and 12.1–14.6 d for males. Superparasitism was common under cage condition, either on specific females or other primary parasitoids. E. transvena females were able to develop in all B. tabaci nymphal stages but preferred the third and early fourth instars. Oviposition and developmental periods of the parasitoid were longest on first and fourth (late) instars of B. tabaci. The highest percentages of parasitization occurred in third instar and fourth (early) instar B. tabaci and the lowest percentages in first and fourth (late) instars. The information should be useful in designing mass rearing protocols and in release trials for suppression of B. tabaci populations.

Little information regarding the biology and ecology of dermapteran predators has been reported. For possible use of Euborellia annulipes (Lucas) (Anisolabididae) in biological control programs against the cotton boll weevil Anthonomus grandis grandis Boheman (Curculionidae), it is important to know the effect of temperature on reproduction in this predator. Our objective was to evaluate the reproductive potential and the longevity of females of E. annulipes under laboratory conditions using an artificial diet, at 25 and 30°C, and to estimate life-fertility tables and growth rates. Fecundity began to decline on day 84 at 25°C and on day 74 at 30°C of adult age and ended with the death of the females at both temperatures. Females of E. annulipes oviposited an average of 206 and 306 eggs, and had a mean longevity of 198 and 149 d at 25 and 30°C, respectively. The gross reproductive rates were 89.2 at 25°C and 91.4 at 30°C; the net reproductive rates were 65.3 at 25°C and 40.3 at 30°C; the generation times were 195.2 d at 25°C and 142.9 d at 30°C; the doubling time was 33.0 d at 25°C and 26.7 d at 30°C; the intrinsic rates of increase were 0.02 at 25°C and 0.03 at 30°C, and the finite rates of increase were 1.02 at 25°C and 1.03 at 30°C. The predator population increased by 52 at 25°C and 20 at 30°C adult progeny per female per generation in the laboratory. The best age for inoculative releases of E. annulipes against cotton boll weevil populations is the age with the highest age-specific reproductive values, that is, newly emerged females at 25 or 30°C.

A statewide survey of New Jersey was carried out during 2001 to determine the current establishment and distribution of introduced natural enemies of euonymus scale. One hundred twenty-two sites were surveyed, and their location was recorded. Euonymus scale infestations were recorded at 89% of the sites surveyed. The most commonly encountered natural enemies were Cybocephalus sp.nr. nipponicus Enrody-Younga, Chilocorus kuwanae Silvestri, and the endoparasitoid, Encarsia citrina Craw. Neither of the introduced aphelinid parasitoid species, Encarsia sp.nr. diaspidicola (Silvestri) and Aphytis proclia (Walker), were recovered from the collection sites. The geographic distributions of the most commonly encountered natural enemies of euonymus scale are discussed.

Bemisia tabaci (Gennadius) (B-biotype) was introduced in the Caribbean in the late 1980s. This new pest drastically changed plant protection management in this region, because of direct damages on cucurbits and transmission of numerous begomoviruses on tomatoes and beans. Parasitoids have been reported for the A-biotype B. tabaci and other species of whiteflies. After the introduction of the new biotype, a few additionnal surveys of associated parasitoids were conducted. To assess the importance of the parasitoid complex of B. tabaci in a Caribbean island, we monitored the parasitoid populations in Guadeloupe in three locations that varied by climatic and agroecological conditions. Three host-plants species were sampled monthly continually for parasitized B. tabaci nymphs during 4 yr. Different phenologic stages of the host plants were present throughout the study. The nymphs were reared in laboratory, and data on the emerging parasitoids and whiteflies were recorded. In every locality, the most common species was Encarsia sophia (Girault and Dodd). This species was not recorded in Guadeloupe before 1997, and it may have displaced other parasitoid species. The greatest diversity and efficiency of parasitoids occurred in agrosystems including diverse crops on small plots, with little pesticide use and with the proximity of a natural forest. Species of the parasitoids composition changed during the 4 yr of the study, suggesting a progressive adaptation of the indigenous parasitoid fauna after the introduction of E. sophia.

We conducted laboratory experiments to determine whether the tick parasitoid Ixodiphagus hookeri Howard uses chemicals of the host tick Amblyomma variegatum F. as host recognition cues. When given a piece of polyethylene sheet containing an air bubble (a dummy host) treated or untreated with hexane, I. hookeri females did not respond to the dummy. However, when females contacted the dummy host treated with hexane extracts from unfed nymphs, engorged nymphs, or unfed adults of the host ticks, they probed the dummy with their ovipositors. When given a choice of dummies treated with hexane extract of engorged nymphs, hexane, or nothing, they did not demonstrate any selective attraction for the dummy with hexane extract from engorged nymphs over the other dummies. A fraction (hexane 9: ether 1) of hexane extract from engorged nymphs strongly stimulated ovipositor probing by females. These results suggest that I. hookeri females use chemicals contacted on host ticks as host recognition cues.

We studied effects of parasitism by two Tiphia species (Hymenoptera: Tiphiidae) on burrowing behavior of their respective scarabaeid hosts and tested the hypothesis that parasitoid alteration of host hormones accounts for the observed behavioral change. In turf field-plots, third-instar masked chafer grubs, Cyclocephala sp., parasitized by native Tiphia pygidialis Allen burrowed to depths of 12–16 cm within 21 d, whereas nonparasitized grubs remained in the upper 4 cm of soil. Grubs bearing an egg or early-instar Tiphia larva were found relatively close to the surface, whereas those with a fourth- or fifth-instar parasitoid were deeper. Experiments in soil-filled, vertical observation chambers confirmed downward movement by parasitized Cyclocephala, and similar response in third-instar Japanese beetle, Popillia japonica Newman, parasitized by Tiphia vernalis Rohwer. Removal of the Tiphia egg from masked chafers was followed by initial downward movement of grubs and then a gradual ascent, suggesting that host behavior is affected both by the venomous sting and feeding by the wasp larva. Significant but inconsistent differences were found in juvenile hormone-III (JH III) titers in hemolymph taken from nonparasitized grubs or grubs parasitized for 1 or 14 d. Topical application of JH III and methoprene acid resulted in grubs moving deeper into the soil, whereas injection of 20-hydroxyecdysone did not affect grub behavior. Failure to dig deeply enough in soil when sampling for parasitized scarab grubs or Tiphia cocoons likely will result in underestimation of parasitism rates.

There is phenotypic variation among individual trees of interior Douglas-fir (Pseudotsuga menziesii variety glauca [Beissn.] Franco) in their resistance to defoliation by the western spruce budworm (Choristoneura occidentalis Freeman). We are evaluating the factors associated with this resistance using grafted clones derived from parent trees that are resistant versus susceptible to budworm defoliation in the field. We tested the potential role of feeding and oviposition behavior in determining the resistance using C. occidentalis larvae and moths from our nondiapausing laboratory colony, and foliage from grafted ramets (6–8-yr-old potted trees) of resistant and susceptible Douglas-firs. In the larval feeding bioassay, fifth instars were offered a choice between branches from susceptible and resistant ramets. There was no difference in the proportion of current-year buds and shoots consumed, indicating that larvae do not discriminate between foliage from susceptible and resistant trees. When offered a choice in cage arenas made of metal screen, female moths laid significantly more of their egg masses on susceptible foliage (54%), compared with resistant foliage (34%), artificial foliage (6%), or nonfoliage material (6%). Conversely, no oviposition preference was detected when resistant versus susceptible Douglas-fir twigs were the only substrates available in paper bag arenas. Western spruce budworm feeding and oviposition behavior do not appear to be important factors associated with Douglas-fir resistance.

This research investigated how the striped cucumber beetle, Acalymma vittatum (F.), responds to the presence of a predator, the wolf spider Rabidosa rabida (Walckenaer). We answered four questions. (1) Does a beetle alter its behavior in the presence of a wolf spider in a laboratory microcosm? (2) Do striped cucumber beetles in nature modify their behavior when a wolf spider is nearby? (3) If beetles do respond to the presence of a wolf spider, what types of cues do the beetles use to detect the predator? (4) Does the proximity of other beetles affect how beetles respond to the predator? In laboratory microcosms, the presence of a spider reduced the frequency at which beetles fed, but beetles did not change their feeding behavior in the presence of a nondangerous arthropod, the cricket Achaeta domestica. Field observations conducted at night in cucurbit gardens revealed that a spider within 15 cm of groups of beetles increased by ≈1.6-fold the rate at which beetles left the plant. The proportion emigrating was higher as group size increased, but group size did not affect the responsiveness to the predator. Further laboratory microcosm experiments revealed that the striped cucumber beetle consistently relies on tactile cues and sometimes on visual cues to detect the wolf spider. In one experiment, the presence of the wolf spider affected the feeding rate of a beetle when it was on the plant, but the most consistent behavioral response to the presence of the spider was to leave the plant at a higher rate.

Although the importance of plant mineral nutrition on insect herbivory has long been recognized, studies have focused almost solely on the effects of varying levels of a single nutrient. One aspect of the relationship between plant nutrition and herbivory largely ignored is the proportions among minerals. The mineral balance hypothesis postulates a plant nutritional state with optimal levels and proportions among minerals that enhances plant growth and suppresses herbivore performance. As part of a systematic series of studies to determine the optimal proportions of minerals for soybeans (Glycine max), plants were grown in hydroponic solution with different proportions of boron (B), zinc (Zn), and iron (Fe), using a D-optimal experimental design for constrained mixtures. In this design, B and Fe varied from 0 to 0.05 mM in the nutrient solutions, whereas Zn ranged from 0 to 0.01 mM. Three soybean feeders, the polyphagous soybean looper (Pseudoplusia includens [Walker]), the oligophagous Mexican bean beetle (Epilachna varivestis Mulsant), and the velvetbean caterpillar (Ancarsia gemmatalis Hübner), were fed leaves from the plants and their developmental performance was evaluated using polynomial models. For all three species, developmental performance was highest on plants grown in solutions without B. Weight gain by velvetbean caterpillar larvae, whose feeding was terminated at 6 d, showed a linear response to mineral proportion (adjusted r² = 0.49), peaking at B:Zn:Fe = 0:20:80. Soybean looper pupal weight and larval developmental time showed predominantly quadratic responses determined primarily by B:Fe ratio (adjusted r² = 0.33 and 0.67, respectively). Mexican bean beetle showed the most complex response to mineral proportion, with cubic models of adult weight (adjusted r² = 0.66) and developmental time (adjusted r² = 0.45) that indicated significant interactions among all three minerals. Soybean shoot growth was described by a reduced cubic model (adjusted r² = 0.83), but unlike the insects, plants grew poorly in nutrient solutions lacking B. Rather, soybeans grew best at intermediate mineral proportions, and consistent with the mineral balance hypothesis, herbivores did relatively poorly on these plants. Also consistent with the hypothesis, the effect of Zn on plant growth and herbivore development was dependent on the ratio of the other two nutrients.

We conducted a study linking mechanistic relationships among fire injury, tree physiological condition, and bark beetle (Coleoptera: Scolytidae) susceptibility. Crown scorch of 40 Pinus ponderosa trees was estimated in a naturally regenerated stand that was thinned and prescribed burned in winter and early spring 2000. Net photosynthetic rate (P_n) of undamaged foliage was higher in heavily and severely than moderately and lightly scorched trees. This trend was more pronounced in the dry season (June) than the wet season (August). This suggests the mechanism underlying the increase in P_n was an improvement in water relations. This was also supported by differences observed in predawn water potential and stomatal conductance (g_s). Constitutive resin volume did not differ among crown scorch classes in June, but was negatively related to crown scorch intensity in September. This suggests that constitutive resin was formed and stored before fire injury, and therefore not strongly affected by crown scorch levels in June. Induced resin production (resin produced after depletion of constitutive resin) generally decreased with increasing crown scorch in both June and September. Induced resin appeared to be related to carbon available for resin synthesis. The proportion of successful colonization attempts by Ips spp. and Dendroctonus spp. was low throughout the season. Colonization of Ips sp. and Dendroctonus spp. was not spatially separated in host trees. Colonization attempts were generally positively related to intensity of crown scorch in both pheromone and no-pheromone treatments. This finding suggests that pheromones attracted insects to the tree, but host physiological condition or other factors ultimately determined host colonization. Our results also suggest that intensity of crown scorch may affect colonization attempts of Ips and Dendroctonus spp. on P. ponderosa trees.

Greenbug, Schizaphis graminum (Rondani), populations over-summering on noncultivated grass hosts may be implicated in early fall infestations in wheat. The purpose of this study was to examine the relationship between over-summering greenbugs on noncrop hosts and fall infestations on wheat. Since greenbug populations on noncultivated hosts may also act as reservoirs of virulence genes, the biotypes of collected aphids were also determined. The grass species present at three sites (two in Oklahoma and one in Kansas) were identified and a species richness curve was generated. Greenbugs were collected at these sites and their hosts and biotypes determined. At Hays, KS, a persistent over-summering greenbug population lead to an early fall infestation in wheat. At the sites in Oklahoma, where over-summering greenbugs were not detected, the fall infestation occurred 3 months later. Biotypes G, I, K, and a new biotype (i.e., previously undescribed) were found on noncultivated hosts at Hays, but only biotypes I and K were found on the cultivated wheat. Finding a new biotype supports the hypothesis that biotypic diversity (new combinations of virulence genes) is generated and maintained on noncultivated grasses, which may then act as reservoirs of virulence genes found in populations on crops.

Dendroctonus frontalis Zimmerman is a major disturbance agent in American pine forests, but attack preferences for various host species, and their relative suitability for reproduction, are poorly known. We studied patterns of beetle attack and reproduction during an infestation of stands containing Virginia pine and loblolly pine. Nearly all Virginia pine were attacked and killed, whereas a third of the loblolly pine escaped attack. Among attacked trees, the density of landings and attacks on Virginia pine was 56–106% higher than on loblolly pine at one site, whereas it was similar between species at another site. Paradoxically, D. frontalis preferred the host that was least suitable for reproduction: mean ± SE = 0.89 ± 0.33 versus 4.65 ± 1.40 progeny/attack in Virginia pine versus loblolly pine. Poor reproduction in Virginia pine was attributable to increased adult mortality, decreased oviposition, and decreased larval survival. Phloem thickness and nitrogen content were similar between the two pine species. Loblolly pine was significantly more suitable for the growth of Ophiostoma minus, a fungal associate of D. frontalis. Resin flow was lower in Virginia pine than in loblolly pine, although oleoresin chemistry may partly explain poor reproduction in Virginia pine. A simulation model predicted that beetle infestations will tend to collapse within stands dominated by Virginia pine, and that increasing availability of loblolly pine will promote infestation growth. Because of beetle preferences, forests that contain even modest proportions of Virginia pine relative to loblolly pine may be less likely to sustain beetle infestations. Management of species composition may provide a means for mitigating the undesirable impacts of this herbivore in pine forests.

Dwarf gorse bush (Ulex minor) heathlands in Limousin, France, are ecological islands often separated by tens of kilometers of grasslands and hedges, where several species of grasshoppers belonging to the genus Chorthippus (Acrididae: Gomphocerinae) coexist. Chorthippus binotatus (Charpentier) feeds only on Ulex minor; nymphs feed exclusively on leaves whereas adults become florivorous at the end of the season. The other species studied (C. biguttulus (L.), C. albomarginatus (De Geer), and C. parallelus (Zetterstedt)) are all graminivorous. The importance of sugars, nitrogen content, sparteine (a quinolizidine alkaloid), and plant architecture in food selection was investigated. Chorthippus binotatus is sensitive to sucrose and fructose, consistent with the high sugar content of Ulex minor flowers. Experiments with grass coated with sparteine showed that this molecule associated with sucrose is a phagostimulant for this grasshopper. Different behavioral responses of graminivorous species are observed with sparteine alone, but never phagostimulation. We compared the response times corresponding to decision-making between the different species toward several components involved in food selection. The food choice toward host plant and sugars is as quick for C. binotatus as for the two graminivorous species (C. parallelus and C. albomarginatus), whereas C. biguttulus is slower and exhibits atypical reactions. Chorthippus binotatus can feed on Poaceae, but with more time spent, leading to an increasing predation risk. This situation is a limitation toward dispersal between different heathlands (patchy habitats).

This study deals with the description, in field conditions, of the oviposition preferences and mortality at the egg stage of the proposed biocontrol agent Anacassis fuscata on its host plant, Baccharidastrum triplinervium, in Southern Uruguay. Egg clusters were classified according to their location on the adaxial or abaxial surface of annual or seasonal leaves. The main tendencies were a very high preference for the oviposition on annual compared with seasonal leaves, and a lack of preference for the adaxial or the abaxial surfaces of the leaf. We propose that this behavior has evolved to create a niche separation between early stage larvae and conspecific adults. Temporal variations in the ovipositing preferences were observed throughout the 2-mo oviposition period, which can be related to changes in the phenology of the host plant. Egg mortality was high in both years studied, and showed variability. The highest incidence was found on the adaxial surface of seasonal leaves, a finding that may be related with an observed low preference for the oviposition on this site. Egg size was smaller in Uruguay than in Argentina and Brazil, which might be explained by the fact that in Uruguay the average number of eggs per cluster is higher. Based on our observations that A. fuscata is a latent species, and that intensive defoliation by larvae does not affect the viability of the host plant, we conclude that even when A. fuscata has features that make it a good candidate for the control of Baccharis and Baccharidastrum, it is not an effective agent for biocontrol under field conditions.

The influence of food item availability on boll weevil, Anthonomus grandis grandis Boheman, feeding and reproduction was determined by providing different numbers of cotton squares (flower buds) to individual weevils. Squares were replaced daily after a 5-d feeding and mating conditioning period. The number of lifetime punctures produced by boll weevil females and males increased with square availability. The total number of punctures caused by boll weevil females was 2.7-fold higher than that caused by males. Fecundity was significantly higher in the 10:1, 15:1, and 20:1 (squares:female) treatments than in the 1:1 treatment. The relationship between eggs laid per day and the square to female ratio significantly changed over the life of the female, with the largest differences among treatments occurring in the first 3 wk of adulthood. Survival of weevil progeny to adulthood was about two-fold higher in the 10:1, 15:1, and 20:1 treatments than in the 1:1 and 5:1 treatments. When each boll weevil female was provided 10, 15, or 20 cotton squares per day, estimates of a population growth index (percent of immatures surviving to adulthood divided by immature development time) and the exponential rate of increase (r_m) were significantly higher than for those provided only one or five squares per day. Boll weevil populations maintained at a square:weevil ratio of 10:1 or above will increase >60-fold each generation (R_o), a rate significantly higher than that exhibited under 5:1 or 1:1 square:female regimens. These data show that daily provision of 10 squares per female provides sufficient resources to elicit a maximal oviposition response in the laboratory. Our results also will be useful in predicting changes in boll weevil populations relative to crop phenology and starting population density.