Large-scale adoption of transgenic crops that produce Bacillus thuringiensis (Bt) toxins could greatly reduce populations of target pests and their specialist parasitoids. We used a spatially explicit model of host-parasitoid population dynamics to examine effects of Bt crops on parasitoid persistence. We modeled a 9,000-ha region with 900 fields of 10 ha, each planted with either a Bt crop or a non-Bt crop refuge. In the 13,524 simulations we conducted, the pest (i.e., host) was never lost from the region before the parasitoid. The parasitoid was lost from the region in 36% of the simulations. The host was lost after the parasitoid in 12% of all simulations. The probability of regional parasitoid loss increased as the percentage of Bt fields and rotation of field types (Bt and non-Bt) increased and as host reproductive rate and parasitoid attack rate decreased. Regional parasitoid loss also increased as the insecticide spray threshold for target pests in non-Bt fields decreased and as parasitoid susceptibility to insecticide increased. With field types fixed, regional parasitoid loss increased as parasitoid movement increased. However, with field types rotated, parasitoid movement did not influence regional parasitoid loss. Host movement did not influence regional parasitoid loss. Factors not modeled that would reduce risk of regional parasitoid loss include use of alternate hosts by the parasitoid, use of alternate host plants by the target pest, and evolution of resistance to the Bt crop by the pest. The results suggest that risk of regional parasitoid loss can be assessed from the parasitoid life history traits and reduced by increasing the percentage of refuge fields, fixing refuge locations, and increasing the insecticide spray threshold for target pests in refuges.

Survival after cold chilling and spring emergence of pea leafminer, Liriomyza huidobrensis (Blanchard), were evaluated in both the field and laboratory in 2001 and 2002. Spring emergence was evaluated through the use of traps placed in various fields and hoop-houses that had high populations of pea leafminers the previous season. No pea leafminer adults were captured in spring emergence cages during either year. To evaluate cold chilling in the laboratory, a factorial design with three temperatures (approximately −5, 0, and 5°C), eight exposure periods (0, 1, 2, 4, 8, 16, 32, and 64 d), and four replicates was employed. Pupal mortality increased as the length of exposure increased, with no survival after 64 d of chilling at any temperature. Chilling exposure periods in the laboratory were compared with the number of days per month that soil temperatures in the study area fell below 5, 0, and −5°C. No field-collected pupae exposed to winter field conditions survived until the spring. The pea leafminer seems to be unable to overwinter in southern Ontario, except in protected areas.

Adult survival is thought to be an important factor regulating the size of aquatic insect populations, yet very little is known about the factors that cause mortality during the adult stage. Percentage mortalities over varying time intervals and 96-h lethal temperature values (96-h_dmax LT₅₀) were calculated for the adults of the common New Zealand caddisfly Hydrobiosis parumbripennis McFarlane (Hydrobiosidae) and stonefly Zelandoperla decorata Tillyard (Gripopterygidae), and 48-h_dmax LT₅₀ values were calculated for the leptophlebiid mayfly Acanthophlebia cruentata (Hudson) using an amplitude of diurnally varying temperature regimens within and outside the insect’s normal environmental range. Maxima ranged from 18 to 40°C and amplitude varied from 6 to 18°C. Mortality of adult mayflies and caddisflies were consistently higher than that of stoneflies for all comparable diurnal temperature trials. Daily temperature maxima were more important than the diurnal range in regulating mortality, with a rapidly increasing mortality as temperature maxima exceeded 24 (Acanthophlebia) or 30°C (H. parumbripennis and Z. decorata). Interpolated LT₅₀ values for diurnally varying air temperature regimens were ∼31–33°C for adult H. parumbripennis and Z. decorata and ∼28–29°C for Acanthophlebia adults. The LT₅₀ value for Z. decorata based on diurnally varying air temperature regimens was ≈10°C higher than that for constant temperature regimens. These findings have potential implications for managing riparian zones alongside streams and also for predicting the impacts of global warming on aquatic insect distributions.

We attempt to quantify the impact of future climate change on the developmental dynamics of onion thrips in Slovenia. Monthly averaged results of simulations of future climate from four different general circulation models (GCMs) were projected to local scale by empirical downscaling. The GCM simulations were based on two emission scenarios (IPCC SRES A2 and B2). Local estimates of monthly averaged air temperatures for five locations in Slovenia were adjusted for an additional four emission scenarios (SRES A1T, A1F1, A1B, and B1) using a pattern scaling technique. They were further transferred to a daily scale using a first-order autoregressive model. A simple degree-day model, based on data reported in the literature, was used to relate the development of onion thrips to temperature. Potential changes in the period with favorable developmental conditions for onion thrips (i.e., temperatures above the lower developmental threshold) and in the number of generations per season were estimated with regard to the expected future climate change in Slovenia. The changes are influenced by the magnitude of temperature increase, its asymmetry within the year, and present climate conditions. Using this approach, one can obtain quantitative estimates of the impact of climate change on the developmental dynamics of an insect pest, but one must be fully cognizant of all the assumptions made in the procedure, which introduce uncertainties in the final results. Further research is needed to evaluate the plausibility of such simplified projections.

We examined how mosquito life history parameters and whole body carbon (C), nitrogen (N), and phosphorus (P) content responded to changing C, N, and P content in food. The southern house mosquito, Culex quinquefasciatus Say, and the western encephalitis mosquito, Cx. tarsalis Coquillett, were reared in containers with diary waste water (high food and C, N, and P concentrations) or effluent from a constructed wetland (low food and C, N, and P concentrations). Low food density decreased survivorship and delayed development from hatching to eclosion and reduced adult mass for both species. Adult females were always heavier than adult males, and Cx. tarsalis adults were heavier than Cx. quinquefasciatus adults. There was little change in C, N, and P content for Cx. quinquefasciatus adults across food treatments, whereas Cx. tarsalis was more variable in C and P, but there was little change in N. Adult Cx. quinquefasciatus had a higher P content (3.0%) than Cx. tarsalis (2.0%). Compared with other aquatic and terrestrial taxa, the relatively high percentage of N and P content (11.5 and 2.5%, respectively) of adult mosquitoes suggest an evolutionary trend toward rapid rates of growth, especially for species that use highly enriched habitats as developmental sites.

Developmental times and survival rates of the immature stages of Diorhabda elongata Brullé (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (Tamarix spp.), were studied in the laboratory at six constant temperatures (15–40°C). At 15 and 40°C, eggs did not develop and sustained 100% mortality. Similarly, larvae at 15°C and pupae at 40°C did not develop and sustained 100% mortality. For all three larval stages, the developmental time decreased with increasing temperature between 20 and 35°C and increased at 40°C. Developmental times also decreased with increasing temperature between 20 and 35°C for the pupal stage as did total developmental time from egg to adult. Both linear and nonlinear models were used to describe the relationship between developmental rates (1/d) and temperature (°C) and to determine stage-specific lower and upper developmental thresholds, respectively. The lower developmental thresholds, calculated using the linear model, ranged from 6 to 15°C for all life stages. Using the nonlinear model, the lower developmental thresholds ranged from 15 to 18°C for all life stages. Likewise, the high temperature thresholds for the first-, second-, and third-instar larvae, pupae, and total development ranged between 40 and 42°C. Results from this study were used to enhance the efficiency of mass-rearing methods for open field releases of D. elongata in California. More importantly, this study is the first step in the construction of a detailed population simulation model to predict field phenology and density of D. elongata to further optimize the use of this biological control agent in managing saltcedar in the western United States.

We evaluated the attractiveness of novel synthetic host plant volatiles alone and in combination with the synthetic aggregation pheromone, grandisoic acid (GA), to overwintered adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) in association with black masonite pyramid traps deployed in an unsprayed apple orchard in 2003 and 2004. Synthetic host plant volatiles evaluated included (1) those identified from foliar and woody tissues of a nonfruiting Stanley plum tree (6-Tree) or the two major components (2-Tree); (2) those identified from Stanley plum fruit (7-Plum) or two components eliciting positive GC-EAD response from plum curculios (2-Plum); and (3) benzaldehyde formulated into rubber septa and replaced weekly [Ben(s)] or dispensed into polyethylene vials and replaced weekly [Ben(r)], not replaced [Ben(nr)], and formulated with 10% 1,2,4-trichlorobenzene and not replaced [Ben(TCB)]. In 2003, the greatest numbers of plum curculios were captured in traps baited with 6-Tree GA and Ben(TCB) GA, with responses to these baits significantly greater than responses to unbaited control traps. In 2004, the greatest number of plum curculios was captured in traps baited with 6-Tree(h) (high release rate dispenser) Ben(TCB) GA, with response to this bait significantly greater than responses to unbaited traps. Combined results indicate that volatiles released by foliar and woody tissues of plum are at least as attractive as the single fruit-based attractant, benzaldehyde, when combined with GA and point toward more competitive attractants for plum curculio based on multiple component blends of volatiles released by the entire tree.

The life history of the agricultural pest Phyllotreta cruciferae (Goeze), including location of overwintering sites, time of spring emergence, reproductive phenology, and seasonal changes in feeding and responsiveness to yellow sticky traps, was studied in the northeastern United States from 2001 to 2003 to provide growers with information to improve their management of flea beetle populations in Brassica crops. Samples of leaf litter, organic debris, and soil were collected from a variety of vegetation types to determine the location of flea beetle overwintering sites surrounding agricultural fields. Significantly more P. cruciferae were found in the leaf litter beneath shrubs and brush or in wooded areas than in grass, within-field debris, or in soil samples taken within each vegetation type. Weekly dissections of field-collected female beetles suggested the occurrence of a partial second generation by P. cruciferae in 2003. In laboratory assays of beetles collected weekly from Brassica fields in Massachusetts, both adult beetle feeding on Brassica foliage and beetle responsiveness to yellow sticky traps shows two peaks (June and August) that corresponded to the first and second generations. Beetle catch on yellow sticky traps was highly correlated (2002: R² = 0.8; 2003: R² = 0.6) with the mean number of feeding holes on injured plants.

We examined the effects of white-tailed deer (Odocoileus virginianus Zimmerman) browsing on the abundance of the black-legged tick (Ixodes scapularis Say) in forested habitats. We estimated abundance of all active stages and recorded habitat variables at two heavily browsed and two control forest areas over 3 yr. Numbers of questing ticks varied significantly between years and between study areas in different years, but neither habitat structure nor tick abundance differed significantly between heavily browsed and control forests. Principal components analysis of habitat variables accounted for 73.4% of the variance in the data set, and tick abundance was directly related to shrub cover and leaf litter depth. However, regression analysis showed no relationship between tick numbers and browse damage. Whereas deer pellet count density was positively correlated with levels of deer browse damage, neither was related to numbers of host-seeking adult ticks. Foraging deer did not disturb the leaf litter and, even at park areas with nearly one-half of shrub stems browsed back, did not seem to alter forest vegetation in a way to affect tick habitats in the understory and shrub layers. In suburban landscapes, deer activity in, and consequently the relative likelihood of introducing ticks into, “edge” and “interior” habitats is likely to be very similar and may account for the lack of a detectable relationship between numbers of questing ticks and distance to ecotonal edges observed here.

We report the results of a 2-yr survey aimed at determining the identity and abundance of native parasitoids of fruit infesting tephritids attacking Psidium guajava L. (common guava) in the endangered northernmost Yungas forests of Argentina, which are being encroached by commercial citrus groves. The 3,200 guavas collected during the peak of the short guava fruiting period (February and March), yielded 10,701 Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) adults (97.4 and 2.6%, respectively) and 712 native parasitoids. The parasitoid species and proportion in the total sample during the 2-yr study period were as follows: Doryctobracon areolatus (Szépligeti), 37.9%; Doryctobracon brasiliensis (Szépligeti), 17.7%; Utetes anastrephae (Viereck), 1.1%; Opius bellus (Gahan), 0.7%; (all Braconidae, Opiinae), and Aganaspis pelleranoi (Brèthes), 32.6% (Figitidae, Eucoilinae). All parasitoids emerged from A. fraterculus pupae (i.e., none from C. capitata). The discovery of D. crawfordi represents the first report for Argentina and the southernmost record for the species. We discuss the practical implications of the role of guava as a reservoir for A. fraterculus and the implications for the biological control of both fruit flies. We also update the taxonomic status of the opiine parasitoids of A. fraterculus in Argentina given that a number of species previously reported in the literature had never been formally described (i.e., represent nomina nuda) or had been misidentified.

Metcalfa pruinosa (Say) is an exotic pest introduced into Italy in the early 1980s. It is a polyphagous pest and can infest several plant species used in agriculture, forest, and urban systems. To control this pest, Neodryinus typhlocybae (Ashmead), a specialist parasitoid attacking young M. pruinosa instars, was introduced in Italy starting in 1987. From 1999 to 2001, the establishment of N. typhlocybae was evaluated and a sampling plan developed to estimate its cocoon population density. The spatial aggregation of the cocoons was analyzed by Taylor’s power law. The aggregation index ranged from 1.064 to 1.136 and a common value (b = 1.1) was estimated. Sequential sampling was shown to be the more practical and least time consuming sampling method. The peak of the parasitoid cocoon population at the end of July (26th to 30th week of the year) is a suitable period in northern Italy to monitor the activity of the parasitoid and to estimate the field parasitization. The potential of the sampling method is discussed, with the aim to evaluate the impact of the parasitoid on M. pruinosa populations.

The effects of a nutrient-based feeding stimulant, Coax, and a stilbene-based optical brightener, Blankophor P167, on the activity of the nucleopolyhedrovirus of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (SfMNPV) on transgenic sweet corn, Zea mays L., expressing a CryIA(b) toxin from Bacillus thuringiensis (Berliner), were studied in the laboratory. Both Coax and Blankophor P167 increased virus-induced mortality. The effects of both materials did not differ between transgenic and nontransgenic corn. The greatest increase in virus-induced mortality occurred when Coax and Blankophor P167 were combined. Neither material affected the percentage of larvae killed by the CryIA(b) toxin.

The effects of multiple mating on fitness in the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), were studied. In the first of a series of experiments, the impact of multiple mating on female fitness was determined by evaluating the effects of a single mating period with one male, continuous exposure to one male, and continuous exposure to five males. Continuous exposure to one male increased lifetime fecundity by extending the period of time progeny were produced compared with a single mating period with one male, although average progeny size was reduced. Exposure to five males significantly reduced female survival and the number and size of progeny produced compared with the other treatments. In the second experiment, the number of progeny and the length of time progeny could be produced from a single copulation were determined. Females became sperm depleted within 7 ± 1 wk after laying 259 ± 22 progeny, but a second mating period 9 wk after the first copulation extended progeny production. In the final experiment, the mechanism for the decline in progeny production at high male densities was determined to be reduced oviposition, caused at least in part by a high proportion of time spent in copula. The number of copulations has costs and benefits for females that may affect population dynamics.

Physical exclusion shows some potential as a novel root weevil control strategy, but barriers to root weevil immigration may also exclude beneficial insects, such as ground beetles. A field study was undertaken in 1997 to assess the impact of two physical barriers—portable plastic trenches and aluminum fences with Teflon tape—on root weevil and ground beetle immigration into plots of strawberry, Fragaria x ananassa (Duchesne). Barypeithes pellucidus (Boheman) and Nemocestes incomptus (Horn), each comprised 43% of the root weevils caught at the site. Most (86%) of the ground beetles caught in control plots were longer than 1 cm, the width of the gap in the portable trench top. Trenches excluded 75 and 63% of B. pellucidus and N. incomptus, respectively, without significantly reducing immigration of large (<1 cm) ground beetles. Fences excluded 65, 84, and 99% of B. pellucidus, N. incomptus, and large ground beetles, respectively. Adding diatomaceous earth to trenches did not increase their efficacy, and fences without Teflon tape excluded ground beetles but not root weevils. The reduction in the population of root weevils and other strawberry pests caused by the use of barriers reduced damage to strawberry plant leaves and increased strawberry plant survival relative to unprotected control plots. Advantages and disadvantages of these physical control tools are discussed with a view to creating superior tools for root weevil exclusion, compatible with an integrated pest management approach. Portable trenches may offer a means of selectively excluding root weevils but not ground beetles.

In an effort to continue the development of a sterile insect release program against the invasive cactus moth, Cactoblastis cactorum (Berg), we released partially sterile males alone or in combination with fully sterile females at a 5:1 or 10:1 (treated:fertile) overflooding ratio inside large field cages containing Opuntia stricta Haworth (Haworth) host plants. Insects were allowed to mate and lay eggs, and all eggsticks were collected daily. Percent egg hatch and reduction in F₁ fertile larvae were used to ascertain the effectiveness of each release combination. In addition, limited field release-recapture experiments were conducted to examine the dispersal ability of untreated and treated cactus moth males. Results suggest that an overflooding ratio as low as 5:1 can effectively suppress C. cactorum in field cages and that releasing both genders together is more effective than releasing males only. In open field releases, the dispersal ability of C. cactorum was not significantly affected by treating the adults with gamma radiation.

Living and synthetic mulches were evaluated for control of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, and aphids in zucchini plantings. Two living mulches, buckwheat, Fagopyrum esculentum Moench, and white clover, Trifolium repens L., and two synthetic mulches (reflective and white) were evaluated during the fall of 2002 and 2003. Results from pan-traps, yellow sticky traps, and foliar counts showed that reflective and buckwheat mulches consistently had fewer numbers of adult whiteflies and aphids compared with the standard white mulch treatments. In 2003, a significant increase in the abundance of natural enemies was recorded in all treatments. Living mulch treatments had higher natural enemy populations than synthetic mulch and bare-ground treatments. However, there were no differences in the species diversity of natural enemies found between treatments. The effectiveness of mulches for controlling immature whitefly numbers and the incidence of squash silverleaf disorder were inconsistent between years. Additional data taken at the end of the 2003 season revealed that two viral strains (PRSV-W and WMV-2) were present in the field. However, visual symptoms associated with these viral diseases did not occur until the end of the season.

Quantitative knowledge of temporal and spatial distribution patterns of arthropod pests and their natural enemies is essential for understanding their interactions and is a prerequisite for the development of reliable sampling plans for estimating and monitoring pest and natural enemy abundance. Temporal and spatial distributions of the cassava green mite Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) and its predator Typhlodromalus aripo DeLeon (Acari: Phytoseiidae) were determined in two cassava fields in Southern Benin, West Africa. Samples were taken to follow predator and prey dynamics at monthly intervals, from August 1998 (shortly after planting), to harvest time in June 1999. In addition, within-plant distribution of both predator and prey was determined in the upper 20 nodes of selected cassava plants on four occasions during the study period. In both field sites, temporal trends in abundance of M. tanajoa and T. aripo were similar but with a slight delay in T. aripo response to changes in M. tanajoa densities. Overall temporal trends of T. aripo and M. tanajoa in both study sites were related to seasonal rainfall pattern, as expected. Aggregation indices calculated using Taylor’s power law indicated that both predator and prey had a clumped distribution, but M. tanajoa distribution was less aggregated after the introduction of T. aripo compared with its previously determined aggregation when efficient predators of M. tanajoa were still lacking in Africa. Within plants, M. tanajoa occurred largely on young leaves; however, the highest densities shifted from the first fully developed leaf (c. leaf 4) to leaves 6–12 in the presence of T. aripo. This downward shift in M. tanajoa distribution on cassava plants is most likely caused by the foraging patterns of T. aripo, which forages within the upper part of the cassava foliage during the night hours and spends much of the daylight hours sheltered in the apex (apical domatium) of the plant. New enumerative sampling plans were developed for M. tanajoa and T. aripo on the basis of the new Taylor’s power law aggregation indices. Limitations of the proposed sampling plans in monitoring population densities of T. aripo and M. tanajoa are discussed.

We present a methodological study that aims to help placate some of the criticism surrounding the use of pitfall trapping for carabid beetles in ecological studies. Because pitfall trap catches are dependent on the activity of carabids and not solely on density, characteristics of the trap construction may influence the success of the trap in different habitat types. Specifically, traditional opaque wooden lids may change the temperature and sun exposure of a trap relative to its surroundings. These abiotic factors may vary with the vegetation structure present around the trap. Thus, traditional opaque lids may offer a shade refuge in low vegetation habitats. We hypothesized that a change in microclimate associated with lid transparency would alter the behavior of ground beetles and thereby lead to a bias in trap catch results. To test this hypothesis, we performed a replicated, two-factor experiment manipulating lid transparency (opaque, partially transparent, and completely transparent) and vegetation height (>2, 1, <0.5 m) around 27 pitfall traps. Soil temperatures beneath each lid varied significantly with lid transparency and vegetation height. There was no effect of either treatment on carabid species richness, whereas species assemblages varied significantly with respect to vegetation height but not lid transparency. However, total carabid catch rates and overall carabid species composition varied significantly with vegetation height but not lid transparency. Therefore, our results show that lid transparency does not bias carabid beetle catch and lend support to the use of pitfall trapping to assess the effects of habitat change on epigaeic communities.

Ceratothripoides claratris Shumsher is one of the most important thrips pest of tomatoes in central Thailand. Hence we conducted studies to determine the intra- and inter-plant distribution of C. claratris on tomatoes in two types of greenhouses, i.e., open-plastic and closed net house. The experiments were conducted on the campus of the Asian Institute of Technology in Bangkok, Thailand. Both adults and larvae of C. claratris showed foliage-biased distribution. Sex ratios of adult C. claratris did not significantly differ on flowers and leaves, whereas on fruits males significantly outnumbered females. On flowers, no diurnal periodicity of occurrence of C. claratris was detected. Generally, thrips infestation commenced in the lower parts of the tomato plants and gradually spread to the higher strata of the plants. Depending on the greenhouse type and the stem system thrips infestation differed significantly over time in the lower but not in the uppermost strata of the plants. In the net house, infestations of C. claratris commenced one week after planting of the tomato seedlings. Soon after the peak in infestations, thrips numbers dramatically decreased. Estimates of Taylor’s power showed that C. claratris had an aggregated distribution pattern on the foliage of tomato plants. The importance of these findings for future monitoring programs of C. claratris infestations on tomatoes is discussed.

Herbivorous insects often feed on pathogen-infected plants in nature, and it is likely that pathogen infection alters host plant quality. We documented the effects of plant infection by a widespread plant virus on host plant quality for a generalist insect herbivore and tested the hypothesis that these effects vary among plant genotypes. We found that infection by Cucumber mosaic virus (CMV) altered the host plant quality of Mimulus guttatus (Phrymaceae) for meadow spittlebugs, Philaenus spumarius (Hemiptera: Cercopidae). The effects of CMV infection on host plant quality, however, varied among full-sib M. guttatus families, suggesting that these effects vary among plant genotypes. In most full-sib families, CMV infection either had no effect on host plant quality or increased host plant quality as measured by spittlebug size and development time. In a few M. guttatus families, however, CMV infection decreased host plant quality. There was no relationship between the effect of CMV infection on plant growth and the subsequent effect of CMV infection on spittlebug performance, suggesting that broad changes in host plant performance (e.g., growth rate) were not responsible for the effects of CMV infection on host plant quality for spittlebugs. We suggest that future studies of the effects of pathogen infection of plants on insect herbivores consider variation among plant genotypes in the mechanisms and ecological consequences associated with these effects.

Successful biological control of invasive weeds with specialist herbivorous insects is predicated on the assumption that the injury stresses the weeds sufficiently to cause reductions in individual fitness. Because plant gas exchange directly impacts growth and fitness, characterizing how injury affects these primary processes may provide a key indicator of physiological impairment—which then may lead to reductions in fitness. The objective of this study was to use physiological methods to evaluate how the invasive weed, Linaria dalmatica L. Miller (Dalmatian toadflax), is affected by two introduced biological control agents within different injury guilds: the stem-boring weevil, Mecinus janthinus Germar, and the defoliating moth, Calophasia lunula Hufnagel. All studies with M. janthinus were conducted under field conditions at two sites in Montana in 2003 and 2004. For C. lunula evaluations, a total of five greenhouse studies in 2003 and 2004 were used. One field study in 2003 and two studies in 2004 also were conducted. Variables measured included net CO₂ exchange rate, stomatal conductance, and transpiration rate. Results from both field sites revealed that the primary physiology of Dalmatian toadflax was deleteriously affected by M. janthinus larval injury. There were no significant differences among treatments for any of the gas exchange variables measured in all eight experiments with C. lunula. Our results indicate that insect herbivores in two distinct injury guilds differentially affect Dalmatian toadflax physiology. Based on the primary physiological parameters evaluated in this study, M. janthinus had more impact on Dalmatian toadflax than C. lunula. With such information, improved risk-benefit decisions can be made about whether to release exotic biological control agents.

Herbivore attack has important consequences on plant performance and on plant community composition, and understanding plant responses to herbivory is important for improving our ability to predict community dynamics and in developing biological control programs. The first objective of our study was to assess the response of purple loosestrife (Lythrum salicaria) to various levels of tissue loss (0, 10, 20, and 60–70%) caused by feeding by a chrysomelid beetle (Galerucella calmariensis) introduced as a biological control agent to North America. Leaf beetle herbivory changed flowering phenology, caused significant reductions in plant growth and inflorescence mass, and increased the branching pattern even in the lowest herbivory treatment. In general, plant performance measures (height, total length of inflorescence) decreased linearly with increasing defoliation level. A second objective was to evaluate whether commonly used artificial herbivory techniques (hole punching and clipping) can reproduce a plant’s response to beetle herbivory at different attack levels. Studies investigating plant–herbivore interactions often favor artificial over natural herbivory because of the control over amount and pattern of tissue loss. However, use of simulated herbivory rests on the assumption that plants respond in similar ways to natural and artificial herbivory. In the case of purple loosestrife (and other biocontrol programs), allowing artificial manipulation of aboveground herbivory may allow easier studies of the impact of multiple herbivores and potential competitive interactions among biocontrol agents. However, differences in growth, reproduction, and plant architecture of purple loosestrife in response to leaf beetle feeding could not be reproduced using simulated herbivory.

The purpose of this study was to assess the persistence and accumulation of the Cry1Ab protein in soil as a result of sustained planting of genetically modified Bacillus thuringiensis (Bt) corn hybrids. Soil samples were collected from agricultural fields in five corn-growing regions of the United States where Bt corn hybrids (MON 810 or Bt11) had been planted for at least 3 consecutive yr. At each site, soil samples were collected during the corn-growing period (postanthesis) and again within 6 wk after harvest. Multiple soil specimens from matched Bt cornfields and nearby, non-Bt control fields were analyzed by diet-incorporation insect bioassay, using growth inhibition (GI) of the European corn borer (Ostrinia nubilalis) as the toxicity endpoint. Positive control soil samples containing Cry1Ab protein at the GI₅₀ level (0.05 μg/g soil) were analyzed in tandem with test and control samples to verify that the bioassay was able to detect low levels of Cry1Ab protein. The limit of detection for Cry1Ab protein in soil was 0.03 μg/g soil. The presence of Cry1Ab protein in soil was assessed by statistical comparison of the insect toxicity (GI) of soils collected from Bt and non-Bt (control) cornfields. Only one soil sample, collected postanthesis in a Bt cornfield that had also been treated with carbofuran insecticide, showed insect toxicity. This toxicity was below the GI₅₀ level, and no toxicity was detected in the soil collected from the same plot shortly after harvest. Therefore, there is no evidence of persistence or accumulation of Cry1Ab protein in soils from fields planted for at least three consecutive growing seasons with Bt corn hybrids.

The tussah silkworm, Antheraea pernyi (Lepidoptera: Saturniidae), is an important natural resource for the silk industry and has been cultured using wild host plants for >2,000 yr in China. To clarify whether there is any risk from pollen of Cry1Ab-containing corn varieties on this insect, the frequency of pollen dispersal and deposition of corn pollen near cornfields and impact on the development of tussah silkworm larvae were studied separately in the field and laboratory. The field survey showed that the pollen density was the highest inside the cornfield with a value of ≈1,000 grains/cm². The pollen deposition rapidly declined with distance from the edge of the cornfield as expected in most cases. No significant differences were observed in the amounts of pollen deposited on glass slides positioned at different heights from the ground at each distance. In the laboratory bioassays, there were no significant differences in the larval mortality and weight of Chinese tussah silkworm between treatment with pollen grains from a transgenic corn line and a nontransgenic corn control at a density of 1,000 pollen grains/cm². Also no significant negative impact was found for efficiency of conversion of digested food (ECD), efficiency of conversion of ingested food (ECI), and efficiency of approximate digestion of food (AD) at the level of 1,000 pollen grains/cm². The results of this study suggest that the impact on the Chinese tussah silkworm of Bt corn pollen from the hybrid to be commercialized in China is negligible in the natural environment.

Water deficit and shade stress in weed-infested crops could alter plant growth and biochemistry and feeding and oviposition by the beet armyworm, Spodoptera exigua Hübner. Palmer amaranth pigweed, Amaranthus palmeri S. Wats., was grown under 25% of full watering (water deficit), 30% of full light (shade), or combined stress. All treatments decreased plant height and weight. Shade and combined stresses decreased leaf counts and increased leaf water content. Water deficit stress increased leaf water potential, soluble protein and carbohydrate contents, peroxidase activities, and accumulations of 10 individual free amino acids (FAAs), summed essential FAAs, and total FAAs. Combined stress increased water potential, soluble carbohydrates, 12 individual FAAs, summed essential FAAs, and total FAAs. Shade stress decreased water potential, soluble carbohydrates, seven individual FAAs, and essential FAAs. Beet armyworm larvae consumed similar leaf areas on water deficit–stressed and nonstressed plants and larger areas on plants grown under shade or combined stress. Larval survival was reduced, and time to pupation was higher on shade-stressed leaves. Adult females deposited more eggs on shade and combined stress plants and fewer eggs on water deficit-stressed plants compared with controls. Beet armyworm feeding and oviposition responded to variation in water content. Stress-induced changes in nutrients were not tied to insect preference but could have negatively influenced survival under shade stress. The results have implications for the plant stress hypothesis and for the use of pigweeds for beet armyworm detection.

We studied the intergenerational effects of nitrogen (N) fertilizer applications to rice plants on the size, fecundity, and intrinsic rate of increase (r_m) of Hysteroneura setariae (Thomas). Treatments consisted of rearing aphids on rice plants receiving 0, 50, 100, and 150% of the standard N fertilizer rates. Adult females produced on the 0 and 150% treatments were transferred to new plants at 0 or 150% N levels to create a matrix of four treatments: 0–0, 0–150, 150–0, and 150–150%. Second-generation aphids produced on 150% N plants had significantly higher survivorship, fecundity, and r_m regardless of the N treatment of plants that parents fed on. N levels had no observed effect on head width. Aphids reared on 0% N plants whose parents were also reared on 0% N plants had significantly shorter body lengths than aphids on all other treatments, including the 150–0% treatment, indicating that the effect of a high N diet was expressed in a second generation of aphids. Results are discussed in the context of aphid population outbreaks in rice fields and in greenhouses.

Anthers and pollen from corn, Zea mays L., expressing Bacillus thuringiensis (Bt)-derived protein frequently fall onto common milkweed, Asclepias syriaca L., growing in and near corn fields. Previous studies have shown that, alone, Bt anthers do not pose a significant risk to the monarch butterfly, Danaus plexippus L. To examine how exposure to a combination of Bt anthers and pollen affects larval fitness and behavior, three studies were conducted. A laboratory study using severed leaves in petri dishes and two studies with caged milkweed plants (tropical milkweed, Asclepias curassavica L., and common milkweed) in an environmentally controlled rearing room. In the petri dish bioassay, additive effects of Bt anthers and pollen were detected. The data suggest that the additive effects may be attributed to behavioral changes in larval feeding such as detecting and avoiding Bt anthers. An additive effect also was seen in both cage studies. In the common milkweed cage study, larvae exposed to Bt anthers and pollen took 1.8 d longer to develop and pupae weighed 6.4% less than those exposed to non-Bt anthers and pollen. These effects are similar to those found in a previous study with naturally deposited levels of Bt anthers and pollen, even though the anther levels we tested were two to three times greater. Despite these effects, when put into the context of risk, Bt corn is not likely to pose a significant risk to the monarch butterfly population in North America.

The exotic Brazilian peppertree, Schinus terebinthifolius Raddi, is an invasive plant that readily displaces native vegetation and develops monospecific stands in central and south Florida’s native ecosystems. Despite prior arthropod surveys of S. terebinthifolius in its adventive range, little is known concerning the acarofauna associated with the weed in Florida. Leaves of S. terebinthifolius also vary in the presence and development of domatia, which are small morphological structures that may benefit mites. We assessed the development of new mite associations with S. terebinthifolius in Florida and quantified within-plant distribution of these arthropods. Mites inhabited over one-third of the sampled leaves with greatest species diversity in the Prostigmata, followed by Mesostigmata, Astigmata, and Cryptostigmata, respectively. Fungivorous mites (dominated by Lorryia formosa) were the most common feeding guild, predatory mites were the most diverse, and herbivorous mites were rarely encountered during the survey. Interior leaves supported greater populations of mites than exterior leaves, whereas height of leaves in the canopy did not affect mite distributions. Foliar domatia varied in development and occurred on nearly two-thirds of the leaves sampled. More than three-quarters of all mites collected were found on domatia-bearing leaves, which supported three times more mites per leaf than leaves without domatia. Mite densities increased concomitantly with the number of domatia, while domatia development only affected tydeids and number of leaves had no effect. The potential influence of domatia-mediated, tritrophic interactions among existing predators and a potential biological control agent of S. terebinthifolius are discussed.

Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most important insect defoliator of potatoes worldwide. In this study, we conducted a series of no-choice assays comparing Colorado potato beetle reproduction and development on potato plants grown in manure-amended and synthetically fertilized soils. Manure-amended soil received annual applications of raw cow manure since 1991 and additional applications of cull potato compost and green manure between 1991 and 1998. Plants grown in manure-amended soil were inferior Colorado potato beetle hosts compared with plants grown in synthetically fertilized soil. The observed negative effects were broad in scope. Female fecundity was lower in field cages set up on manure-amended plots early in the season, although it later became comparable between the treatments. Fewer larvae survived past the first instar, and development of immature stages was slowed down on manure-amended plots. In the laboratory, first instars consumed less foliage from plants grown in manure-amended soils. These results show that organic soil management is associated with plant characteristics unfavorable for beetle reproduction and development, which should be taken into consideration when designing fully integrated crop management systems.

Flowers are sites of frequent visitation by pollinators and numerous other insect groups and thus could potentially represent high-quality resource patches for generalist predators that are able to exploit these aggregations of prey. In northeastern old-fields, the sit-and-wait predator Phymata pennsylvanica Handlirsch (Heteroptera: Phymatidae) occupies ambush sites on both inflorescences and nonflowering green plants. In 1998, a study was conducted to test the hypothesis that flowers are higher-quality hunting sites than nonflowering plants for these predators. Prey capture events were directly observed during daily and hourly checks on fifth-instar bugs placed on flowering or nonflowering ambush sites in the field. Prey capture rate, prey size, and food consumption rate did not differ significantly between the two site types. However, the taxonomic composition of the prey caught on the two site types was strongly divergent, with adult Diptera dominating on flowering sites and sap-feeding Homoptera dominating on nonflowering sites. These results indicate that there are times when flowering and nonflowering sites can be largely functionally equivalent for a predator in terms of prey capture success and suggest that nonflowering sites may be more important in the foraging ecology of P. pennsylvanica and other old-field ambush predators than has previously been realized. However, one implication of the existence of distinct prey communities on the two site types is that the relative quality of flowering versus nonflowering sites could potentially vary unpredictably among different locations or years depending on the particular dynamics of the dominant prey groups on each site type.

The oriental fruit fly, Bactrocera dorsalis Hendel, is one of the most destructive pest insects of tropical and subtropical fruits and vegetables. It is thought to be an introduced species in Yunnan Province, China, where it causes severe damage. Depending on the latitude, the fly occurs year-round or only during the warm season. To assess the genetic diversity of the fly and to understand the relative isolation of its populations in this mountainous region, we conducted an analysis of population genetic structure using mitochondrial cytochrome oxidase (COI) gene sequences. Twenty-eight haplotypes were detected among 37 individuals with up to 13 mutations between haplotypes. Within-population diversity was high, and genetic distances between haplotypes reached 2.2%. The haplotype network showed that many haplotypes were missing in the sampled populations. Intraspecific variability in Bactrocera dorsalis was thus high in Yunnan. The data suggested either a longer residence of the fly in Yunnan than recognized previously or a recurrent colonization process from different origins. One population, namely Ruili, was significantly isolated from the others, probably because of geographic barriers to gene flow. This population seemed to be in a contact zone with flies originating from surrounding regions. In contrast, some populations separated by >300 km were not significantly structured. We suggest that the insects engage in long range dispersal, most probably taking advantage of prevailing air currents. The data also suggested that the region of Kunming, where the fly only occurs seasonally, is recolonized each year by migrating flies from several southern regions.