Woody plants are commonly fertilized in ornamental landscapes, based in part on the rationale that fertilization enhances pest resistance. However, a critical evaluation of evidence finds little to support this claim. Rather, many studies have found that fertilization decreased woody plant resistance to spider mites, sap sucking insects, mandibulate folivores, subcortical feeding insects, and browsing mammals by enhancing the nutritional quality of the plant and/or decreasing secondary metabolite concentrations. The growth/differentiation balance hypothesis (GDBH) postulates a physiological trade-off between growth and secondary metabolism, and predicts a parabolic response of secondary metabolism to variation in nutrient availability. Specifically, fertilization of moderately nutrient-deficient plants is predicted to decrease secondary metabolism if growth is increased but photosynthesis is not affected. However, fertilization of extremely nutrient-limited plants is predicted to increase secondary metabolism if photosynthesis is also increased. A number of studies have found fertilization to increase growth and decrease secondary metabolism. A few studies on extremely nutrient-deficient sites found fertilization to increase foliar secondary metabolism, but insect performance was not affected, possibly because increased foliar nitrogen counteracted effects of secondary metabolites on host quality. These studies, while consistent with the GDBH, do not represent adequate tests because none measured effects of fertilization on photosynthesis as well as growth. Only a few studies have addressed effects of fertilization on the ability of woody plants to tolerate herbivory, and all found fertilization to have no effect. The entrenched paradigm that fertilization enhances the insect resistance of woody plants in ornamental landscapes needs to be reassessed.

In several field assays, Macrodactylus subspinosus (F.) adults were significantly more attracted to feeding adult conspecifics than to any other treatment; males were more attracted to feeding virgin females than feeding field-collected (i.e., mated) females. Alternative treatments among the experiments included plant material, artificially damaged plant material, screened artificially damaged plant material adults, virgin females, mating adults, field-collected males, and field-collected females. Repeated-measures experiments in laboratory bioassays indicated that wild grape leaf disks damaged and treated with beetle regurgitant were no more attractive than unaltered or artificially damaged disks; however, the treatments that had been fed upon first attracted significantly more beetles than those that had been fed upon subsequently. Beetles were never observed “calling”, and scanning electron microscopy did not reveal cuticle pores as in some scarabs. We conclude that the act of feeding causes the immediate release of plant volatiles that act with normal levels of plant volatile release to increase adult attraction. Furthermore, virgin females enhance male attraction over mated females by causing the release of either female-based or plant-based volatiles.

RESUMEN En varios experimentos de capturas de campo, adultos de la especie Macrodactylus subspinosus (F.) fueron significativamente más atraídos hacia aquellos adultos que estaban alimentándose que hacia los otros tratamientos. Los machos fueron más atraidos hacia las hembras virgenes que estaban alimentándose que hacia las hembras colectadas en el campo que tambien estaban alimentándose. Los otros tratamientos fueron tejido de planta, tejido de planta con daño artificial, tejido de planta con daño artificial protegido con tela antimosquito adultos, hembras virgenes, adultos fértiles, machos colectados en el campo (i.e., fértiles), y hembras colectadas en el campo. Los experimentos de laboratorio indicaron que discos de hoja de uva silvestre, dañados y cubiertos con rejurgitado del escarabajo no fueron más atrayentes que discos inalterados o artificialmente dañados; sin embargo, los tratamientos en que los adultos fueron alimentados primero atrajeron considerablemente más escarabajos que aquellos en que los adultos fueron alimentados al final. Se podría concluir que el acto de herbivoria induce la liberacion immediata de volatiles de plantas que son atractivas a conspecificos e induce a las hembras a producir compuestos que actuan con los volatiles de la plantas para atraer mas machos.

Males of many species of fruit flies (Tephritidae: Dacinae) respond to chemical lures of botanical origin. Such lures (e.g., cuelure and methyl eugenol [ME]) have been successfully used in fruit fly population management. The hypothesized role of these chemicals by males is exclusively ecological (pheromonal and/or allomonal), and male response has been classed as pharmacophagy. However, for a response to plant-derived lures to be classified as pharmacophagous sensu stricto, it must be demonstrated that the role of these chemicals is ecological and not primarily metabolic (e.g., nutritional) or associated with host plant recognition. To specifically test the primary metabolic effects of feeding on ME, we investigated the physiological consequences of exposure to ME in the dacine fly, Bactrocera cacuminata (Hering). Our results indicate that feeding on ME does not confer any physiological advantage to B. cacuminata. This is reflected in the lack of any consistent difference over time between ME-fed and non ME-fed flies in terms of overall weight and lipid, carbohydrate and protein reserves. Survival was not significantly influenced by exposure to ME either. These results support the hypothesis that ME use by B. cacuminata could be pharmacophagous.

Synthetic female sex pheromone was used to monitor the phenology of male Ascogaster quadridentata Wesmael, an egg-larval parasitoid of codling moth, Cydia pomonella (L.), in conjunction with pheromone trapping of the moth and the banding of trees to determine larval parasitism. Catch of this parasitoid was typically ≈10 times less than the moth catch, and larval parasitism varied from 7 to 12%. The emergence of the parasitoid occurred slightly later than the female moth emergence, by both outdoor emergence cages and pheromone trapping. The seasonal activity of male parasitoids was otherwise synchronous with male codling moth flight. A survey of orchards in four regions of New Zealand showed considerable regional variation in the capture of the parasitoid in pheromone traps. The potential value of the parasitoid may be limited by the nil tolerance of the pest in export fruit, but pheromone trapping of this parasitoid could improve the understanding of biological control in non-export situations, where the economic threshold is higher. Pheromone trapping for insect biological control agents is a valuable tool that can help to determine and improve parasitoid success.

We examined the effect of irrigating alfalfa (Medicago sativa L.) with selenium-contaminated water on the oviposition response, larval feeding preference, development and survival of the beet armyworm, Spodoptera exigua Hübner, a generalist herbivore. Alfalfa was grown in sand cultures under three levels of sodium selenate irrigation: (1) control with no Se added; (2) a low rate of 0.0066 g sodium selenate/60 liters water; (3) and a high rate of 0.20 g sodium selenate/60 liters water. The low concentration treatment resulted in 2.88 ± 0.52 μg Se/g plant dry weight and did not affect percent survival to adult eclosion compared with the control at 1.26 ± 0.11 μg Se/g dry weight. The high rate generated 305.81 ± 52.14 μg Se/g dry weight of alfalfa and significantly fewer insects survived compared with insects fed control alfalfa at 1.11 ± 0.12 μg Se/g dry weight. High Se levels, but not low levels, decreased the relative growth index for larvae. In two-choice bioassays (treated/control) neonate larvae did not discriminate between control and Se-treated plants at high or low levels. Fourth instars did not discriminate between plants with low Se levels and control plants, but preferred to consume plants with high, usually lethal concentrations of Se. Females preferred ovipositing on plants with low Se concentrations over control plants, but did not discriminate between plants with high Se levels and untreated controls. This indicates that although females and late instars may be able to differentiate between Se-treated and control alfalfa they do not avoid plants containing high concentrations of Se. Thus, alfalfa with high Se-treatment levels is resistant to S. exigua, and may serve as a population “sink,” where females oviposit and few offspring survive to reproduce.

The relative attractiveness of natural and synthetic pheromone of the obliquebanded leafroller, Choristoneura rosaceana (Harris), the codling moth, Cydia pomonella (L.), and the oriental fruit moth, Grapholita molesta (Busck), was compared in apple orchards. A piezoelectric sprayer was used to emit the main and selected minor pheromone compounds at an equal rate from two adjacent traps, one baited with natural and the other baited with synthetic pheromone. The average number of moths captured in traps baited with natural C. rosaceana pheromone was two times greater than the average number captured in traps baited with synthetic pheromone, and the average number of moths captured in traps baited with natural C. pomonella pheromone was four times greater than the average number captured in traps baited with synthetic pheromone. The average number of moths captured in traps baited with natural G. molesta pheromone was two times greater than the average number captured in traps baited with synthetic pheromone; however, the difference was not statistically significant. The results suggest that more effective synthetic pheromone formulations could be developed for monitoring C. rosaceana, C. pomonella and G. molesta, and for orientation disruption of C. rosaceana and C. pomonella.

Changes in the mean, variance and developmental instability of morphological traits have often been used to detect environmental stress in insects. Studies have focused on linear measurements, whereas modern morphometric techniques allow the separation of shape and size effects. To examine stress effects on shape we assessed wings of Helicoverpa punctigera moths exposed to two stresses (pesticide, low temperature). The pyrethroid esfenvelerate applied in larval medium increased development time but did not affect viability, whereas low culture temperatures (7–18°C) influenced both fitness traits. Neither stress affected mean wing size, but both stresses had a marked influence on wing shape. Changes in shape were stress-specific and detectable despite moderate sample sizes. The variance in wing size was altered by low temperature stress but not pesticide exposure. Neither stress increased the asymmetry of wing shape or size; in fact cold stress decreased asymmetry for centroid size. However, measurement error of asymmetry could not be accurately assessed in these wings because scales of both wings could only be removed once. Shape changes therefore appear to be more sensitive to stress in this moth species than other morphological measures, and stress effects on variation among individuals appear to be different than those on asymmetry.

Starvation of immature boll weevils resulting from square desiccation is considered a major determinant of natural mortality. However, the critical weight below which a larva cannot complete development without further feeding has not been determined. Critical weights of second and third instars were investigated using food-removal techniques, and the age and size distributions of larvae in newly abscised squares were estimated from field collections. Second instars examined averaged 3.22 mg in weight and ranged from 0.23 to 5.55 mg. About 80% of second instars weighing ≥1.67 mg molted, but none pupated. The estimated critical weight for 50% of unfed second instars to survive to third instar was 2.49 mg. Third instars examined averaged 14.64 mg in weight and ranged from 1.81 to 34.43 mg. About 64% of third instars weighing ≥5.29 mg developed into adults, ranging in weight from 1.61 to 21.49 mg and averaging 10.44 mg. Estimated critical weights for 50% of unfed third instars to survive to the pupal and adult stages were 6.63 and 8.89 mg, respectively. The estimated critical weight for 50% of pupae to survive to adulthood was 4.52 mg. Larvae collected from newly abscised squares were predominantly second (56%) and third instars (39%). Furthermore, an estimated 19% of all larvae collected were capable of development to adulthood without further feeding. In light of the rapid rate of larval growth and development, our results suggest that square desiccation sufficient to deter feeding by larvae must occur within 1–3 d of square abscission to produce a high proportion of starvation-induced mortality.

The collection of macronutrients (fats, carbohydrates, proteins) under natural conditions by the black carpenter ant, Camponotus pennsylvanicus (De Geer), was examined. Carbohydrate and crude protein were the primary macronutrients retrieved, with 2.3 times more carbohydrate than crude protein collected per trip. Only negligible amounts of crop lipid were detected. Collection patterns varied with macronutrient. Carbohydrate collection was consistently strong over all months, but varied between years and nests. In contrast, crude protein collection was consistent between years and nests, but exhibited peaks in June and September, when colonies typically contain mature larvae. Retrieved food was transported internally: <1% of returning foragers carried solid matter in the mandibles.

The height distribution of adult parasitoids of the Dendroctonus frontalis Zimmermann complex trapped on the boles of Pinus taeda L. trees was examined. The study was conducted within two active D. frontalis infestations in the Talladega National Forest in Alabama in July 1998. Stickem Special-coated 15 × 20 cm wire mesh (6 mm²) traps were placed on pines with late instar to adult D. frontalis and Ips spp. at 2 m intervals to a height of 16 m on 12 trees and at 4-m intervals to a height of 16 m on 6 trees. Traps were changed on alternate days for 14 d, and all adult parasitoids of the D. frontalis complex were identified and counted. There was a positive correlation between height and number of parasitoids. This is most likely due to the high proportion of Roptrocerus xylophagorum Ratzeburg and Heydenia unica Cook and Davis collected, because both of these species preferred the upper bole. Each parasitoid species had different height distributions. R. xylophagorum, H. unica and Dendrosoter sulcatus Muesebeck all preferred the upper bole, with a peak trap catch between 12 and 16 m. In contrast, Coeloides pissodis (Ashmead) and Dinotiscus dendroctoni (Ashmead) both preferred the midbole, with a peak catch at 6 m. Only Spathius pallidus Ashmead showed no height preference; however, this species also had the lowest trap catch. Although each parasitoid species had its height preferences, all species were distributed throughout the length of the infested bole.

To elucidate the temporal response of parasitoids to their host density, we investigated the temporal relationship between the density of the leafroller moth, Eudemis gyrotis (Lepidoptera, Tortricidae), and larval and pupal parasitism in the field. E. gyrotis had overlapping-generations, and the density of larvae and pupae of E. gyrotis varied seasonally. Analysis of the temporal relationship between the density of E. gyrotis and the percentage parasitism revealed a tendency toward positive density-dependent attack by the parasitoid Apanteles sp. (ater-group) (Braconidae) on early-stage E. gyrotis larvae, and inverse density-dependent attack by Goniozus japonicus (Bethylidae) in late-stage larvae. However, no temporal density-dependent attack was observed by the pupal parasitoids Brachymeria excarinata (Chalcididae), B. lasus, and Itoplectis alternans spectabilis (Ichneumonidae). These different responses to host density by the parasitoid species were discussed in terms of the mode of parasitism, the host stages attacked, host-searching behavior, and the effect on the host population.

Laboratory studies on the temperature-dependent development of Lacanobia subjuncta were performed at 10 constant temperatures ranging from 10.0°C to 37.5°C. Lower developmental thresholds for eggs, larvae, and pupae were calculated as 6.6, 6.7, and 4.9°C, respectively. Degree-days required to complete a stage were estimated as 75, 476, and 312, for the egg, larval, and pupal stages, respectively. A comparison of the degree-days required to complete immature development under fluctuating field temperatures indicated the laboratory data could be used to predict results in the field. Larval head capsule measurements indicate distinct size ranges for each larval instar with the exception of a slight overlap for fifth and sixth instars.

Aculops lobuliferus (Keifer) is a little known pest of plantation Populus spp., which is capable of causing substantial damage. This is the first documented occurrence of A. lobuliferus in South Carolina. Previous anecdotal data indicated clonal variation in Populus susceptibility to A. lobuliferus damage. A damage rating scale was created to monitor mite damage in 2000–2001 in a short-rotation woody crop plantation; damage descriptions and seasonal phenology also were recorded. Foliar damage and terminal mortality were monitored on two Populus deltoides Bartr. clones, ST66 and S7C15, receiving one of three silvicultural treatments (irrigated [I], fertilized [F], or I F) or no treatment (control). In 2001, early season foliar damage ratings were significantly higher on clone S7C15; however, damage on clone ST66 was greater after miticide treatments later in the year. Terminal mortality did not differ between clones. Silvicultural treatment significantly affected foliar damage levels in both clones. Trees receiving I F and F treatments had higher damage ratings than did trees receiving irrigation alone or the control at times. Clone S7C15 trees receiving fertilizer had significantly less terminal mortality than their nonfertilized counterparts. Application of a commercially available miticide significantly reduced A. lobuliferus damage levels. This study demonstrates that A. lobuliferus damage levels can be influenced by Populus clone and silvicultural treatment. Foliar and terminal damage levels observed in this study indicate the potential for substantial economic impact of A. lobuliferus on plantation Populus. Although an effective control method may be to select and plant resistant Populus clones, chemical control remains a viable option.

The CLIMEX model was used to infer the climatic requirements of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), from the fruit fly’s observed geographical distribution in the Mediterranean region. The model indicated that the potential distribution was limited by cold to the north in Europe and by dryness in northern Africa and in the south of Spain and Portugal. The model was then used to estimate the potential geographical distribution of the species in Argentina and Australia. The results agreed with the observed distribution in Argentina and much of the historical distribution in Australia, but they did not agree with the present distribution in eastern Australia. In the latter region, another species of fruit fly, Bactrocera (Dacus) tryoni (Froggatt) has been credited with displacing C. capitata. Seasonal and year-to-year variation in climatic suitability was explored at three selected locations in Argentina. The results indicated that some detrimental effects of summer temperatures, or of extremes of precipitation, occurred in particular areas. Some of these limiting factors, especially dry stress, were prolonged enough to restrict the geographical distribution of medfly. However, when irrigation was included in the simulations, the detrimental effect of dryness was removed. Finally, a global risk map for medfly was produced, which highlights the areas at risk from this major quarantine pest.

Leptoglossus occidentalis Heidemann is a serious pest of second-year cones in conifer seed orchards. We investigated the impact of this insect on first-year pine conelets. L. occidentalis adults and nymphs were caged on conelets of lodgepole pine, Pinus contorta var. latifolia Engelmann, and western white pine, Pinus monticola Dougl. ex D. Don. Abortion in lodgepole pine conelets was negligible, but feeding by nymphs reduced seed production by 75% compared with unexposed controls. Mortality of nymphs on lodgepole pine conelets was almost 100%, suggesting that conelets of this species are not a suitable food source for L. occidentalis. When nymphs had access to second-year cones, seed set in conelets was unaffected, and survival of nymphs greatly improved. Seventy-five percent of western white pine conelets exposed to L. occidentalis nymphs aborted, compared with none in unexposed controls. Seed set in surviving cones was reduced by 47%. Conelet abortion fell to 10% when nymphs were provided with an alternative food source. In pine seed orchards, damage to conelets probably is caused primarily by nymphs remaining on trees after second-year cones have been harvested.

Understanding the relationship of parasitoids with their insect hosts and crop plants is needed to develop good management strategies for Bemisia tabaci (Gennadius), a whitefly pest. The abundance and establishment of parasitoids of B. tabaci B-biotype were tested with taxonomically diverse plants in the greenhouse (7 plant species) and in the field (16 plant species in Egypt). Greenhouse tests were conducted on plants free of whitefly nymphs to avoid this influence on parasitoid behavior, and field tests were conducted in crops with feral populations of B. tabaci. In the greenhouse, the parasitoid, Encarsia pergandiella Howard, was most abundant on Vigna unguiculata (L.) Walpers, followed by Gossypium hirsutum L. The propensity for this parasitoid to forage on the bottom leaf surface compared with the top surface varied among crops (45–90% were on the bottom leaf surface) and over time (≈50% were on the bottom leaf surface around sunrise, whereas ≈90% were on the bottom surface by mid-day). Inundative releases of laboratory-reared parasitoids, Eretmocerus mundus (Mercet), into field crops increased parasitization rates in all crops tested. Some crops (e.g., two Brassica species and V. unguiculata) were more conducive to parasitism of B. tabaci than other crops (e.g., Cucumis sativus L. and Lycopersicon esculentum Miller). Findings from this research may be useful in the enhancement and conservation of parasitoids of Bemisia.

Camponotus vicinus (Mayr) is a common ant species found in the Pacific Northwest. It is an important predator of many forest insect pests, a potential biological control agent, and is also a serious structural pest. However, little knowledge is currently available about its nest location and distribution. The study is designed to examine the biotic and abiotic factors in affecting the distribution of carpenter ants. Investigations during 1993 and 1994 showed that in conifer forests in northern Idaho, C. vicinus was found nesting mostly in fallen logs and tree stumps. The diameter of logs used as nest sites was 5–55 cm, but most nests were found in logs with diameters between 15 and 35 cm. Tree bark, duff, and wood beneath stones were also used as nest sites. Most nests were found in dry areas associated with an opening in the forest canopy. This kind of site can be called a C. vicinus carpenter ant zone. To study the effect of biotic and abiotic factors on nest aggregations of C. vicinus, five factors were tested in conifer forests of northern Idaho: habitat availability, food abundance, competition, moisture, and temperature. Competition is not a main factor in restricting the distribution of C. vicinus because food and habitat are relatively abundant throughout the forests. The main factors that restrict the distribution of the carpenter ant, causing colonies to aggregate in open and dry forest areas are an interaction between temperature and moisture during the daylight hours.

We sampled bark beetle (Coleoptera: Scolytidae) populations in 17 declining and healthy red pine plantations in Wisconsin over 3 yr. We tested for potential relationships among numbers of bark beetles, conspecifics and competitors, and predators within and among flight seasons to help identify factors affecting population densities. The two most common bark beetle species obtained were Ips pini (Say) and Ips grandicollis (Eichhoff). The predominant predators obtained were Thanasimus dubius (F.) (Cleridae), Platysoma cylindrica (Paykull) (Histeridae), and Platysoma parallelum Say. Declining stands contained significantly more Ips than did healthy stands during the early portion of the season. Healthy stands had more predators than declining stands. There were strong delayed inverse relationships between I. pini and predators at the site level, both within and between flight seasons. The number of I. pini caught during the late portion of the season was lower when each of the above predators was more abundant earlier in the season, during both 1998 and 1999. Likewise, numbers of I. pini and I. grandicollis caught during the early portion of the year were inversely related to numbers of predators caught during the previous year. Although Ips trap counts showed significant correlations with each predator species, simple predator-prey models did not necessarily improve fits based on habitat quality (i.e., Ips numbers regressed on prior Ips numbers). We did not observe evidence for interspecific competition among Ips spp. This pattern is consistent with the view that host plant quality and predation jointly affect I. pini and I. grandicollis population dynamics. These results emphasize the importance of interactions among host tree physiology, predation, and dispersal in the population dynamics of phloeophagous herbivores, and have implications to forest management.

Parasitoid assemblages associated with Phyllonorycter spp. leafminers (Lepidoptera: Gracillariidae) were examined on six deciduous oak species (Quercus, Fagaceae) in Japan to understand how host leafminers, host food plants, and geographic location influence the structure and function of parasitoid assemblages. The parasitoid assemblages on five of the six oak species showed similar species richness (18–20 spp.), regardless of the number of host leafminer species and the abundance of hosts. Species composition was influenced by geographic location as well as host food oaks, and to a lesser extent by the leafminers. The assemblages varied in guild structure but showed nearly equal ratios of koinobiont/idiobiont species. The ratio was almost the same as that in Great Britain. These results suggest that the well-known argument that parasitoid communities are mostly influenced by host food plants is not universal, and that parasitoid assemblages may be organized with a balance between numbers of koinobiont and idiobiont species regardless of species richness, species composition, or geographic location. Total rate of parasitism did not correlate with the number of parasitoid species or the evenness of the assemblage. This implies that the host–parasitoid system is not under top-down control.

Two existing models for predicting first entry of pecan nut casebearer (Acrobasis nuxvorella Neunzig) larvae into pecans were evaluated in Oklahoma over a 2-yr period. In 1996, the Texas model had a mean accuracy for predicting first significant nut entry of 5.2 d late, and the Georgia model estimated this same parameter 8.2 d early. Predictions for 1997 were better for both models with the Texas and Georgia models predicting first significant entry 3.2 and 4.0 d early, respectively. The Texas model was consistently late in predicting first significant entry dates in 1996 although three of the seven sites were within 1 d of the observed entry date. The Georgia model was consistently early in its prediction for 1996. Both models showed a mix of over and under predictions for 1997, possibly due in part to the severe spring freeze observed over much of the state. Based on 2 yr of data, as well as data collected in 1998, degree-day (DD) thresholds derived from the Texas model were established for the following phenological events; onset of trapping for adults using pheromone-baited traps (1,100 DD), initiation of scouting for eggs (1,500 DD), and initiation of scouting for damage (1,600 DD).

A computer model of the interaction between the fungal pathogen Entomophaga maimaiga Humber, Shimazu & Soper and its host, the gypsy moth, Lymantria dispar (L.), had previously been developed to simulate infection by fungus resting spores (azygospores) that are present in soil and germinate in spring if moisture is adequate. This model is now expanded to include infection caused by conidia that are produced on dead, infected caterpillars when relative humidity is near 100%. As inputs, the model uses temperature, relative humidity, rainfall, abundance of resting spores in the soil, and gypsy moth population density. From plots in 1999, 2000, and 2001, data on weather conditions (the first year from daily weather station data and the last two from in-plot data loggers) were obtained, and gypsy moth density and resting spore abundance were determined. Also, collections of gypsy moth larvae were taken weekly to determine proportion of infection by the fungus. These data were used to find best-fitting parameters for the model. Using the same parameter values, model output was close to data for all years. When conidial dispersal was incorporated in the model, output and data were even closer. A validated model should be useful for evaluating and predicting gypsy moth-fungus interactions in forests.

The focal distribution of Ixodes scapularis Say and Amblyomma americanum (L.) was measured at 10-m intervals across the 1-ha study area placed within a mixed hardwood-pine forest with a sparse to dense shrub layer. At each of the resulting 100 locations, 1-m² plots were established and, following characterization of vegetation and edaphic conditions, were periodically flagged throughout the nymphal tick season. I. scapularis and A. americanum nymphs appeared to be nonrandomly distributed within the forested study area. Although only a few I. scapularis nymphs were collected overall, several locations consistently yielded more A. americanum nymphs than the remaining sites. I. scapularis was found in plots with substantial shrub density, extensive leaf litter, and deep soil duff layers, all of which contribute to creating high-humidity conditions for questing ticks. Questing A. americanum were more frequently encountered in more open canopy situations with less dense shrub layers and significantly reduced litter and duff layers. A. americanum appears to be more tolerant of desiccating conditions and so is able to occupy microsites or microhabitats that are less favorable for sympatric I. scapularis. The implications of these findings on the ability to sample ticks and estimate disease transmission risk are discussed.

Surveys were conducted at four Texas Army National Guard training facilities to assess the natural distribution and prevalence of Thelohania solenopsae Knell, Allen and Hazard infection in polygynous imported fire ants, Solenopsis invicta Buren. T. solenopsae was found at three of the four training facilities; intercolonial prevalence ranged from 9 to 47%, and worker prevalence ranged from 0.15 to 0.57. A plot containing fire ants infected with T. solenopsae at one of the training facilities was monitored for 2 yr to determine whether natural infection rates fluctuate over time, whether infection affects colony size, as indicated by mound volume, and whether there was a relationship between climate and infection prevalence. At this site, intercolonial prevalence ranged from a high of 47% in July 1999 to a low of 11% in October 2000, and mean worker prevalence ranged from 0.20 to 0.57. Mound volume of infected colonies was consistently less than the volume of uninfected colonies. There was no correlation between temperature or precipitation and proportion of infected colonies, but there was a positive correlation between colony density and percentage of infection with T. solenopsae.

In this study, we asked whether different predatory assemblages (i.e., flying invertebrates, crawling invertebrates, and birds, representing vertebrate predators) in a temperate forest impose significantly different levels of predation on larvae of Orgyia leucostigma (J. E. Smith), the whitemarked tussock moth and also whether the size of whitemarked tussock moth larvae influence invertebrate and vertebrate predation. Predation by species in vertebrate and invertebrate predator assemblages on two sizes of O. leucostigma larvae on box elder, Acer negundo (L.) (Sapindales: Aceraceae) was compared using exclusion cages. Cages covered with mesh of different sizes and sticky barriers were used to exclude different kinds of predators (i.e., birds, flying invertebrates, and crawling invertebrates). Five small and five large larvae were placed on box elder saplings. Predation by birds was the greatest source of mortality of large larvae when compared with that caused by flying and crawling invertebrates. Predation played an insignificant role in the disappearance of small larvae whose disappearance was associated with their dispersal behavior.

Overwintering pupae obtained from early and late emerging blueberry maggot populations were kept at similar temperatures to determine if phenological differences are caused by initial exposure to different temperature conditions in the soil after pupation. The effect of temperature and duration of exposure on time to emergence was determined by dividing pupae of each population into two cohorts placed at 20 or 25°C. Subsequently, at periodic intervals, samples were first transferred to 5°C for 6 mo to ensure diapause completion, and later kept at 20°C to measure time to emergence. In addition, we studied postdiapause pupal temperature-dependent development of the late population under laboratory and field conditions, and compared rates of development at constant temperatures and outdoors using degree-day emergence models. Longer exposure of pupae to similar temperature conditions did not decrease differences in time to emergence between populations. In the early population, there were no differences in postdiapause development with relation to temperature exposure, but in the late population, pupae exposed to 25°C emerged slower than pupae exposed to 20°C. In both populations, longer exposures to high temperature after pupation resulted in slower postdiapause development. Also in the late population, 52% of individuals emerged after 60 d exposure to 25°C, without going through diapause. Field pupal development of the late population was characterized by longer postdiapause than the early population. The presence of a transient change in the temperature-development rate relationship, observed during outdoor postdiapause development in July, was also apparent from degree-day model predictions. This developmental slowdown had not previously been observed in any Rhagoletis species.

We evaluated the population dynamics of Colorado potato beetle in processing tomatoes and potatoes using immigration profiles, density through time, rates of development and survivorship. We also evaluated the beetle’s influence on yield of processing cultivars. Colorado potato beetle immigrated into both crops. The first available crop had the earliest immigration event and higher immigrating adult and egg mass densities. Length of time that overwintering adults spent in the field, and duration of oviposition, were more closely related to accumulated degree days than time of immigration. Later in the season there was a trend toward fewer eggs per egg mass from overwintered adults. Rates of development suggested that large larvae developed more quickly in potatoes in 1998, but not in 2000, and small larvae developed at similar rates in either crop. Egg-to-adult survivorship ranged from 0.02 to 0.06, even though initial egg densities varied by approximately an order of magnitude. Survivorship varied more between years than between crops. Colorado potato beetle did not influence yield of processing tomatoes. Our field studies estimated similar life table parameters and population dynamics of Colorado potato beetle in two solaneaceous crops, and concurred with laboratory bioassays in the literature suggesting that this beetle has the potential to achieve similar fitness on both tomatoes and potatoes. However, beetle densities did not influence yield, and thus may have little affect on pest management in processing tomato cultivars.

Racemic disparlure sprayed at doses of 37 to 75 g/ha (AI) for mating disruption of gypsy moths, Lymantria dispar (L.), interfered with male moth search behavior outside of treated plots. Counts of feral male moths in pheromone-baited traps and the number of recaptured laboratory-reared moths gradually increased with increasing distance from treated areas. In most cases this effect was observed up to 250 m from treated plots. However, in one location it extended to 600 m along a narrow valley. The proportion of tethered females that mated during 1-d exposure increased gradually with increasing distance from treated plots. The relationship between male moth capture rates in pheromone traps and mating success of tethered females near treated plots was the same as the one observed in previous studies in pheromone-free areas.

Traps baited with the synthetic aggregation pheromone of the boll weevil (Anthonomus grandis Boheman) are often used to monitor population fluctuations, distribution, and behavior. However, many factors generate variability in daily captures, making interpretation of trapping data difficult. Previous studies have shown that wind speed in the microenvironment around a trap can greatly affect numbers captured on a given day. It is possible that variation in air movement may also generate variation in trap captures through its effects on the pheromone plume. The current study was conducted to determine whether five traps placed in a line at two commonly used spacings (15 and 20 m) interfere with one another. There was no evidence for interference on days when winds struck the trap line at a nearly perpendicular angle. However, for both spacings, there were significant and substantial effects of relative trap placement within a line on days when winds struck it at an angle (>22.5°) away from the perpendicular. The largest and most consistent effect was that the trap furthest upwind in the line captured the most weevils, especially on days of moderate wind speeds (10–20 km/h). The upwind trap captured 1.5–2.0 times as many weevils as the next trap in the line, which usually had the lowest percentage of capture of any of the traps. Until the minimum adequate spacing has been established, traps should be placed at least 30 m apart in experiments in which such biases can adversly affect interpretation of results.

Bertha armyworm, Mamestra configurata Walker, oviposition preferences were examined using choice and no-choice experiments with intact cruciferous plants. Previous larval feeding experiments had indicated that some Brassica juncea L., Sinapis alba L., and B. carinata L. lines were relatively resistant to bertha armyworm feeding. To examine oviposition preferences, a representative cultivar from each species was compared with the Brassica napus L. cultivar AC Excel using plants at the full-flower stage in a choice experiment. The S. alba cultivar AC Pennant received the greatest number of eggs, despite being relatively resistant to larval feeding and offering the least amount of foliage among the plants tested. AC Excel was also compared with the B. juncea cultivar AC Vulcan in dual-choice and no-choice experiments. Bertha armyworm oviposition was substantially greater on AC Excel than on AC Vulcan in all experiments. The effects of crop phenology on oviposition were examined using three growth stages (preflower, full-flower, and pod) of B. napus AC Excel in choice tests. The number of egg masses and total number of eggs on each plant were used to measure oviposition. The full-flower plants were significantly more preferred for oviposition than plants in preflower or pod stages. Bertha armyworm laid most eggs in the upper portion of the crop canopy on the underside of leaves.

Macroinvertebrate communities in a central Kansas grassland were examined to assess their responses to differences in land management and explore their viability for biological assessment of grasslands. Canopy (drop-trap) and ground-dwelling (pitfall traps) communities were quantitatively sampled from June-September 1998 and 1999. The responses of the whole arthropod community and two focal groups, Coleopteran families and Orthopteran species, to three land use types (brome fields, old fields, and native prairies) were examined. Vegetation analyses reflected clear differences among land use types. Bromus inermis Leyss, an exotic grass, and Andropogon gerardii Vitman, a native grass, dominated brome fields and native prairie sites, respectively. Old fields were composed of a mixture of native and exotic plant species. Coleopteran family richness and diversity were significantly greater in native prairies than brome fields (P < 0.05), whereas orthopteran species richness and diversity peaked in brome fields. Diversity and richness of all arthropod groups examined were significantly, positively correlated with plant species diversity and richness in drop-trap samples (P < 0.05). Coleopteran family diversity and richness in pitfall samples were positively correlated with abundance of native plants, but orthopteran species diversity and richness were negatively correlated with native plant abundance. Coleopteran and orthopteran responses to land use appeared linked to differences in management practices. Whereas coleopterans appeared most influenced by plant community composition, orthopterans showed sensitivity to mechanical disturbance associated with haying on native prairie. Plant and arthropod group diversities were not consistently correlated, demonstrating that arthropod groups can reflect differences in a landscape that may not be apparent from examining plant communities alone.

While searching for hosts on plants, female parasitoids meet different plant structures and host densities that will influence their host finding success. In this study, we determined whether plant structure, host density, and foraging duration influenced the percentage of Ephestia kuehniella Zeller eggs parasitized by Trichogramma evanescens Westwood. One female was introduced to forage either 4 or 24 h on artificial plants of three different structures (simple, intermediate, and complex) on which 4 or 16 host eggs were glued. Plant structure influenced rate of parasitism in both foraging durations, whereas host density was found to be significant only when female had 4 h to forage. Mean rate of parasitism generally decreased with an increase in complexity of plant structure and host density in both foraging durations. Almost twice as many eggs were parasitized on simple plants compared with complex plants for all host densities and foraging durations. Overall, female parasitoids parasitized, on average, <1 egg/h, except when they foraged 4 h in the presence of 16 eggs. Plant structure therefore affects host-encountering success. Physical structure of a plant mediates ecological interactions and is involved in parasitoid-host population dynamics. It operates by increasing costs associated with host finding.

Distribution patterns of five grasshopper species (Orthoptera: Acrididae) were related to microtopography, plant zonation, and diet preference on a Virginia barrier island. Trimerotropis maritima Harris occurred on the landward side of incipient foredunes dominated by Ammophilia breviligulata Fernald (Poaceae), a C₃-grass. Psinidia fenestralis Serville occurred primarily on and adjacent to older dunes dominated by Spartina patens (Aiton) Muhlenberg (Poaceae), a C₄-grass. Melanoplus bivitattus Say, Melanoplus femurrubrum De Geer, and Melanoplus differentialis Thomas were more widely distributed than the other two species but were most common in wet swales dominated by S. patens and the shrub seedlings, Myrica cerifera L. (Myricaceae) and Baccharis halimifolia L. (Asteraceae). Laboratory feeding preference experiments indicated a strong influence of host plants on grasshopper distribution patterns. The diet specialists, T. maritima and P. fenestralis, were limited to the distribution of their host plant species, whereas the Melanoplus congeners were generalists in diet and in distribution. Although distribution patterns were related to host plant specificity, microtopography was important to the small-scale distribution of all five species within the distribution range of host plants. The preference of M. differentialis for Myrica cerifera foliage may affect shrub establishment in the grass-dominated swales.

The red imported fire ant, Solenopsis invicta (Buren), is an invasive species in the southern United States and is expanding its range westward to California and eastward up the Atlantic Coast. This voracious predator can reach extremely high densities and have widespread effects once it invades an ecosystem. We conducted a 2-yr sampling study and a series of greenhouse and field experiments to document the impact of red imported fire ants on beneficial insects in cotton. We found that the densities of 12 of 13 natural enemies sampled on cotton plants in 1999, and 8 out of 8 sampled in 2000, were negatively correlated with the densities of foraging fire ant workers. Red imported fire ants reduced the survival of lady beetles (Coccinella septempunctata L., and Hippodamia convergens Guérin-Méneville) (Coleoptera: Coccinellidae) by 50% and green lacewing larvae (Chrysoperla carnea Stephens) (Neuroptera: Chrysopidae) by 38% in greenhouse experiments. Fire ants did not, however, reduce the survival of spiders (Oxyopidae, Thomisidae, and Clubionidae). We used a commercially available fire ant bait to suppress fire ant populations in cotton fields during the 2000 growing season and compared the densities of beneficial arthropods in treated versus control fields. Densities of lady beetles, spiders, and big-eyed bugs (Heteroptera: Geocoridae) were significantly higher in fields with suppressed fire ant populations than in fields with relatively large fire ant populations. The effect of fire ants on minute pirate bugs (Heteroptera: Anthocoridae) was inconsistent, and populations of damsel bugs (Heteroptera: Nabidae) and hooded beetles (Coleoptera: Anthicidae) were not affected by fire ant suppression. The results of this study suggest that red imported fire ants are major intraguild predators of important beneficial arthropods in cotton.

Red imported fire ants, Solenopsis invicta (Buren) (Hymenoptera: Formicidae), are an invasive species found in high densities throughout southeastern agricultural systems. We tested the hypothesis that fire ants tend cotton aphids, Aphis gossypii Glover (Homoptera: Aphididae), and thus release them from predation by lady beetle larvae, Coccinella septempunctata L. and Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae), and green lacewing larvae, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae). Fire ants preferentially foraged on aphid-infested cotton, Gossypium hirsutum L., plants (x̄ = 103 ± 47 ants per plant) compared with plants without aphids (x̄ = 5 ± 3 ants per plant). In caged greenhouse experiments, fire ants reduced survival of lady beetle larvae by 92.9% and green lacewing larvae by 83.3%. Furthermore, strong mortality imposed on aphid predators by fire ants affected aphid survival. With the addition of fire ants to aphid-predator treatments, aphid survival approximately doubled. In a field experiment, predator larvae were more abundant in cotton plots with experimentally suppressed densities of fire ants (0.62 ± 0.11 lady beetle larvae per sample; 0.06 ± 0.02 lacewing larvae per sample) than in plots with high fire ant densities (0.23 ± 0.06 lady beetle larvae per sample; 0.01 ± 0.01 lacewing larvae per sample). Conversely, cotton aphids were more abundant in high fire ant density field plots (x̄ = 6.83 ± 0.03 aphids per leaf) than in low fire ant density plots (x̄ = 4.04 ± 0.03 aphids per leaf). These data suggest that red imported fire ants enhance cotton aphid survival and density in the field through predator interference.

Azalea plant bug (Rhinocapsus vanduzeei Uhler) fifth instars and a commercially obtained green lacewing (Chrysoperla rufilabris Burmeister) first and second instars exhibited a type II functional response when caged with varying densities of fourth or fifth instar azalea lace bug, Stephanitis pyrioides (Scott), prey. Attack coefficients for combined fourth and fifth instar prey were statistically similar for R. vanduzeei and C. rufilabris (0.052 and 0.057, respectively). The handling time was significantly greater for R. vanduzeei (3.96 h) than C. rufilabris (2.41 h). Search efficiency generally declined for both predators as initial azalea lace bug density increased. C. rufilabris killed significantly more fourth and fifth instar prey than R. vanduzeei (8.0 and 6.0, respectively) in 24 h. Results indicate that C. rufilabris is a more suitable candidate for augmentative, not inoculative, release for azalea lace bug control than R. vanduzeei. However, R. vanduzeei can effect reductions in azalea lace bug populations in the landscape as a component of the guild of lace bug’s natural enemies and should be considered in conservation efforts.

The potential for nontarget effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin, when used for biological control of ticks, was assessed in laboratory trials. Fungal pathogenicity was studied against convergent ladybird beetles, Hippodamia convergens Guérin-Méneville, house crickets, Acheta domesticus (L.), and the milkweed bugs Oncopeltus fasciatus (Dallas). Fungal spores applied with a spray tower produced significant mortality in H. convergens and A. domesticus, but effects on O. fasciatus were marginal. Placing treated insects with untreated individuals resulted in mortality from horizontal transmission to untreated beetles and crickets, but not milkweed bugs. Spread of fungal infection in the beetles resulted in mortality on days 4–10 after treatment, while in crickets mortality was on day 2 after treatment, suggesting different levels of pathogenicity and possibly different modes of transmission. Therefore, M. anisopliae varies in pathogenicity to different insects. Inundative applications can potentially affect nontarget species, but M. anisopliae is already widely distributed in North America, so applications for tick control generally would not introduce a novel pathogen into the environment. Pathogenicity in lab trials does not, by itself, demonstrate activity under natural conditions, so field trials are needed to confirm these results and to assess methods to minimize nontarget exposure.

The management of agroecosystems affects intricately linked assemblages of organisms, and nontarget species are not necessarily unimpacted. We examined the effect of Bt-cotton and of lepidopteran prey (Spodoptera exigua Hübner) that had ingested it on the adult survivorship of four important heteropteran predators of cotton pests. Longevity significantly decreased for Orius tristicolor White and Geocoris punctipes Say (by 28 and 27% of the control value, respectively), whereas no effect was found for Nabis sp. and Zelus renardii Kolenati. This finding contrasts with the results of previous studies in which Orius spp. and G. punctipes were either fed only plant material or nonlepidopteran prey. S. exigua is a lepidopteran with low susceptibility to the Bt toxin expressed in cotton and therefore exemplifies the possible effect on predators of lepidopteran pests that would become resistant to Bt. The importance of Bt toxin type, the difference between plants and prey and between different prey species as routes of ingestion of Bt toxins, and the need for studies assessing the population and ecosystem-level effects of Bt cotton are discussed.

Fungicidal effects of glyphosate and glyphosate formulations on the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metchnikoff) Sorokin, Nomuraea rileyi (Farlow) Samson, and Neozygites floridana Weiser & Muma were evaluated under laboratory conditions. Media previously inoculated with entomopathogenic fungi were exposed to distilled water, glyphosate (active ingredient), seven glyphosate formulations, and five blank formulations (carrier only). The fungicidal activity was determined by measuring inhibition in mycelial growth in solid media (B. bassiana, M. anisopliae, and N. rileyi), and spore concentration in liquid medium (N. floridana). Glyphosate did not have fungicidal activity against any of the fungi tested. Fungicidal properties of glyphosate formulations varied among fungal species. Neozygites floridana and M. anisopliae were susceptible to all glyphosate formulations. RoundUp Ready-To-Use was consistently the glyphosate formulation with one of the strongest fungicidal properties. Fungicidal activity of some formulations had a synergistic effect with glyphosate. RoundUp Original was the only formulation that did not show any interaction on fungicidal activity between glyphosate and the formulation. The results showed that the four fungi tested are susceptible to various glyphosate formulations when exposed to field concentrations.

RESUMEN Los effectos fungicidas de glyphosato y formulaciones de glyphosato fueron evaluados bajo condiciones de laboratorio en los hongos entomopatógenos Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metchnikoff) Sorokin, Nomuraea rileyi (Farlow) Samson, y Neozygites floridana Weiser & Muma. Medios de crecimiento previamente inoculados con los hongos entomopatógenos fueron expuestos a agua destilada, glyphosato (ingrediente activo), siete formulaciones de glyphosato, y cinco formulaciones sin ingrediente activo (solamente inertes). La actividad fungicida fue determinada en medios de crecimiento sólidos midiendo el área de crecimiento miceliar inhibido (B. bassiana, M. anisopliae, y N. rileyi), y en el medio de crecimiento líquido determinando la densidad de esporas (N. floridana). Glyphosato no tuvo ninguna actividad fungicida para ninguno de los hongos. Las propiedades fungicidas de las formulaciones de glyphosato diferieron entre las especies de hongos. Neozygites floridana y M. anisopliae fueron susceptibles a todas las formulaciones de glyphosato. RoundUp Ready-To-Use fue consistentemente una de las formulaciones de glyphosato con propiedades fungicidas mas fuertes. La actividad fungicida de varias formulaciones tuvieron un effecto sinérgico con glyphosato. RoundUp Original fue la única formulación que no mostró ninguna interacción en la actividad fungicida entre glyphosato y la formulacion. Los resultados muestran que los cuatro hongos en este estudio son susceptibles a varias de las formulaciones de glyphosato cuando expuestos a concentraciones de campo.

Coleomegilla maculata DeGeer is a polyphagous predator that is important for suppressing pest populations in corn. We evaluated the impact of Cry3Bb-expressing transgenic corn pollen (event MON863) on C. maculata fitness parameters in the laboratory. C. maculata larvae were fed mixtures of pollen containing 0, 25, 50, 75, or 100% transgenic pollen, aphids, or were not fed; and the duration of each instar and pupal weight were compared among treatments. In a second trial, other C. maculata larvae were reared on one of the pollen mixtures or artificial diet; and the duration of larval and pupal stages, pupal weight, adult mobility, adult survivorship, and female fecundity were compared among treatments. There were no differences in any of the fitness parameters among C. maculata in the treatments fed different mixtures of pollen. Beetles in the pollen mixture treatments had faster larval development times, greater larval survivorship, and greater pupal weight than the beetles fed only aphids or an artificial diet. We conclude that we did not detect any effects on the fitness of C. maculata that ingested pollen from event MON863. However, these results do not necessarily apply to other transgenic crops expressing toxins specific to Coleoptera.

Location and parasitism of Diatraea saccharalis (F.) by Cotesia flavipes (Cameron) were compared between hosts fed either conventional or transgenic sugarcane expressing Galanthus nivalis L. agglutinin (GNA) under choice and no-choice conditions. In olfactometer experiments, females of C. flavipes randomly visited the different odor zones available but spent significantly more time in odor zones corresponding to plants damaged by D. saccharalis versus blank (control) odor zones. However, they spent similar amounts of time in odor zones corresponding to damaged transgenic and conventional sugarcane. Laboratory and field-cage experiments showed that C. flavipes equally parasitized D. saccharalis feeding on transgenic and conventional sugarcane plants. Moreover, sex ratio and brood size of C. flavipes were similar on hosts fed transgenic or conventional sugarcane. The results of this study suggest that transgenic sugarcane expressing GNA would not significantly affect host location and parasitism of D. saccharalis by C. flavipes in the field.

Interactions between Steinernema scapterisci Nguyen & Smart and Ormia depleta (Wiedemann), introduced natural enemies of Scapteriscus spp. mole crickets, within hosts were examined by exposing mole cricket hosts to each natural enemy alone, both natural enemies simultaneously, or to one natural enemy 3 d before exposure to the other. Also, O. depleta life stages were exposed to the nematode directly (in water) and in sand. Host mortality was greatest (≥98%) when hosts were exposed to both natural enemies or when exposed to planidia (fly larvae) only. All hosts exposed to both natural enemies simultaneously and to planidia first produced nematode progeny; 79% of hosts exposed to nematodes only produced nematode progeny. When exposed to both natural enemies, fewer hosts produced fly progeny. From 10 to 31% of multiparasitized hosts produced progeny of both natural enemies. Adult fly eclosion from puparia developing in multiparasitized hosts was substantially less, but not significantly so, than eclosion from puparia produced in hosts exposed to planidia only. Development times for tachinids were shorter when developing in hosts exposed to planidia only. Nematode infective juveniles emerged sooner from hosts exposed to planidia first, but emerged more slowly from hosts exposed to the nematode first. Exposure to nematodes did not affect larvae as they exited hosts and formed puparia. Successful adult fly development and eclosion did not differ after exposure of fly larvae and puparia to nematodes directly and in sand. Adult eclosion from puparia formed from larvae exposed to nematodes in sand (79%) was less than that of puparia formed from larvae exposed to sand only (97%). A few pupae that had been exposed to nematodes as larvae were found infected with the nematode. No pupal infection occurred when puparia were exposed to nematodes. More than one-third (34.5%) of adult O. depleta were found infected after eclosing and crawling through sand containing the nematode. Because O. depleta appeared to be somewhat disadvantaged within multiparasitized hosts and larvae and adult flies were susceptible to infection when exposed to the nematode in sand, the potential exists for populations of the fly in the field to be adversely affected in areas where S. scapterisci is abundant.

We monitored egg parasitism and larval populations of Pieris rapae (L.) and Trichoplusia ni (Hübner) in cabbage plots treated with point and broadcast releases of Trichogramma brassicae Bezdenko, and we investigated whether weekly sugar sprays improved egg parasitism rates. We also compared yield and pest densities in cabbage treated with Bacillus thuringiensis (Dipel), methomyl (Lannate), or point releases of T. brassicae to an untreated control, and investigated the economics of these control strategies. Egg parasitism was highest in the point release treatment (46%), and parasitism in the broadcast and the broadcast sugar spray treatments (31 and 24%, respectively) did not differ from the control. Weekly applications of sucrose did not increase egg parasitism or decrease larval pest populations. Releases of T. brassicae did not significantly reduce P. rapae and T. ni larval populations, and plant damage and cabbage head weight were unaffected in the T. brassicae treatments relative to the control. In addition, the cost of applying the T. brassicae wasps was not recouped with significant yield improvements relative to the control. Methomyl and Bt consistently suppressed P. rapae and T. ni populations below action thresholds in a cost-effective manner.

The population dynamics, persistence, and efficacy of Heterorhabditis bacteriophora Poinar (Oswego strain) applied to control the clover root curculio, Sitona hispidulus (F.), were investigated in a Pennsylvania alfalfa (Medicago sativa L.) field. Nematodes established and persisted following application rates of 2.5, 7, and 15 billion infective juveniles per hectare. Significant differences in nematode densities between treatments were not observed beyond 43 d after application, indicating that application rate likely did not affect long-term persistence. In the third field season, plots that received the original 15-billion nematodes per ha treatment were split into clover root curculio-excluded and clover root curculio-present subplots to assess the effect of this insect on nematode persistence. Nematode populations were significantly lower in the curculio-excluded plots by October, suggesting that the nematodes recycled through that host. However, nematode populations were not significantly different by April of the fourth field season. Nematode efficacy throughout the study was inconsistent. In the first field season, emergence of clover root curculio adults was significantly reduced in plots receiving the 15 billion nematode per ha treatment. However, alfalfa taproot ratings for clover root curculio feeding injury indicated that scarring was reduced only in the 7 billion nematodes per ha treatments. No significant reductions in taproot injury were observed in the second field season, but by the third year, significant reductions in root injury were evident in the plots that originally received 7 and 15 billion nematodes per ha.

The sample distribution of oviposition scar counts of the carrot weevil, Listronotus oregonensis (LeConte) was best fit by the Poisson distribution when the mean number of carrot weevil oviposition scars per plant was ⩽0.047. When the mean was ⩾0.06 oviposition scars per plant, the distribution of oviposition scar counts was best fit by the negative binomial distribution. Seventeen spatial patterns of parsley plants (Petroselinum crispum) infested with carrot weevil oviposition scars were obtained from sampling four commercial fields weekly for 4–5 wk on a 10 × 10 grid pattern. Using a 95% confidence level, 148 parsley plants having no oviposition scars indicates that the percentage of infested plants is <2%. Conversely, if one infested plant is found before 148 plants have been examined, then the desired level of confidence has not been achieved, and a treatment is indicated. Sampling with this decision rule and a variety of sampling transects was simulated using the data from commercial fields. Sampling in X- or V-shaped patterns resulted in the most correct decisions and the fewest incorrect decisions overall. The X-shaped pattern led to the fewest cases of failing to correctly classify an infestation that required control. It had one of the largest average sample sizes when the infestation was below the action threshold, and one of the smallest when the infestation was above the action threshold. Results of this study can assist parsley growers with better timing of pesticide applications or biological controls.

A more practical method than limb jarring is needed to monitor the plum curculio, Conotrachelus nenuphar (Herbst), in peach trees. Of 223 orchard visits made in Arkansas, traps captured plum curculio adults on 114 visits, whereas limb jarring did so on only 29 visits. Pyramid traps and jarring tree limbs along the orchard edge began to capture plum curculio adults 1 wk before the start of fruit feeding damage and continued to capture plum curculio adults until after harvest. Pyramid traps located at the edge of the peach orchard caught significantly more adults than did traps placed >30 m into the orchard interior or traps placed along the edge of an adjacent woodlot. Pyramid traps and screen traps captured similar numbers of plum curculio adults in 14 of 17 samples. Only one orchard in Oklahoma and another in Arkansas had smaller circumference tree trunks (<38 cm) than the other orchards resulting in significantly more plum curculio adults captured in pyramid traps than in screen traps. The screen trap was less expensive and sustained environmental conditions better than did the pyramid trap and may be used on trees >38 cm in circumference. The derived economic threshold of 0.045 plum curculio adults per pyramid trap per day equated to 1% new fruit damage. This study suggested that combining trap counts with percentage of new fruit damage should be used to make insecticide application decisions against plum curculio.

The feasibility of disrupting sexual communication in oriental beetle, Exomala orientalis (Waterhouse) with a microencapsulated sprayable formulation of (Z)- and (E)-7-tetradecen-2-one, the major and minor pheromone components, respectively, was evaluated in blueberries and ornamental nurseries during 1998 and 1999 seasons in southern New Jersey. In 1998, pheromone-baited traps captured significantly fewer male beetles in blueberries, treated with a 9:1 blend of (Z)- and (E)-7-tetradecen-2-one at 100 g (AI)/ha of the major component, or in nurseries treated with (Z)-7-tetradecen-2-one alone at the same rate, compared with trap captures in untreated control plots. The percentage of reduction in trap captures (disruption index) in plots treated with the blend in blueberries was comparable to reductions in trap captures in nurseries (97 versus 92%) treated with the major component alone. During 1999, pheromone trap captures in blueberry and nursery plots treated with a 93:7 blend of (Z)- and (E)-7-tetradecen-2-one at 37.5 g (AI)/ha of the major component were on an average 92 and 82% lower compared with trap captures in untreated control plots, respectively. Significantly fewer tethered virgin female oriental beetles were found in copula/contact with males in treated blueberry fields relative to those deployed in untreated control plots. These results suggest that communication disruption is a promising strategy to manage oriental beetle populations in blueberries and ornamental nurseries. This is the first study to document the feasibility of disrupting sexual communication in a soil-dwelling coleopteran with applications of sex pheromone components to the soil.

We examined genetic variation in host selection behavior of a phloeophagous insect herbivore. Data from paternal families of the bark beetle Ips pini (Say) were used to estimate the heritability of host acceptance and gallery construction behaviors. Males are the host-selecting gender in this genus. Male beetles were assayed over three generations to determine whether they rejected or accepted host media amended with concentrations of alpha-pinene that simulated host tissue, and 10% from each group were selected for breeding lines. In a separate experiment, 10% of individuals constructing the shortest and 10% of individuals constructing the longest galleries in this medium were established in separate breeding lines. The results indicate high additive genetic variation with respect to both traits. On the basis of the results with full-sib breeding lines, we estimated heritability of host acceptance behavior (i.e., entry into simulated hosts) at 0.78 and heritability of gallery construction behavior at 0.64. The divergence between lines in host acceptance and gallery construction behaviors was associated with paternal performance and was symmetrical. This study demonstrates that the use of phytochemical cues to accept potential hosts has a heritable component in bark beetles. I. pini is a useful and convenient model for such studies.

The purpose of this study was to monitor tobacco thrips populations during the early spring in Georgia and to determine the role of brachypterous tobacco thrips in epidemics of tomato spotted wilt virus (TSWV). Potted peanuts were placed into fields at four locations in south Georgia throughout the spring of 2000 and 2001. During March 2001, half of all potted peanuts were covered with exclusion/inclusion cages. Tobacco thrips were collected from terminals and flowers on a weekly basis and were identified as macropterous or brachypterous. Nonstructural protein enzyme-linked immunosorbent assay (ELISA) was performed on individual thrips to determine the proportion of brachypterous and macropterous viruliferous thrips in the population. Macropterous thrips were more abundant than brachypterous thrips, except at the Coffee County location during late February and early March. Peaks in thrips abundance and percentage of viruliferous thrips shifted approximately 2 wk later for 2001 than for 2000 at the Tift County location. In laboratory transmission experiments, no difference was found in the ability to transmit TSWV for the two wing morphs. Macropterous thrips appear to be more capable of colonizing and subsequently transmitting TSWV to newly emerged crops. Therefore, it appears that brachypterous tobacco thrips may help to perpetuate the disease cycle of TSWV by harboring the virus over the winter, and by keeping inoculum in the population until temperatures rise and the percentage of macropterous thrips in the population increases.