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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 Hubner) 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.

The fast-growing Central American tree Leucaena leucocephala (Lam.) de Wit (Leguminosae: Mimosoidaeae) has been widely planted in the tropics since the 1970s for agro-forestry, reforestation, and fodder. Since the mid-1980s the tree has suffered serious damage throughout its exotic range from the psyllid Heteropsylla cubana Crawford, which is also native to Central America. This article summarizes field studies on the tree and the psyllid conducted at 2 sites in north Thailand: a cool highland and a warm valley site. In the highlands, mean psyllid densities per shoot were slightly higher, defoliation was greater, and dry matter production losses due to the psyllid were >3 times higher than those at the valley site (62.5 and 18.3% losses, respectively). Using field data, the lower thermal thresholds for tree growth and psyllid development were 11.2 and 9.6°C, respectively. Psyllid abundance was negatively correlated to temperature. When maximum temperatures exceeded 36°C, psyllid abundance fell dramatically, mortality increased, and body size decreased. These data suggest that the tree and the psyllid are climatically mismatched. H. cubana prefers new shoots, and population cycles were related to tree growth cycles. Finally, populations of the introduced parasitoid Psyllaephagus yaseeni Noyes (Hymenoptera: Encyrtidae), native coccinellids, and spiders showed little correlation to the psyllid population’s intrinsic rate of increase. Percentages of parasitism by P. yaseeni were low (mean = 1.2–1.9%, maximum = 6.0%) and no evidence of density dependent regulation was found.

Populations of the cabbage maggot, Delia radicum (L.), occur in the field during all seasons in coastal northern California because the climate is mild, hosts are available, and a percentage of the population does not enter diapause. Laboratory experiments on this population of the cabbage maggot showed the following 6 results: (1) criteria for diapause vary with the conditions that induce diapause, (2) the proportion of larvae entering diapause is highest at low temperatures across all photoperiods and at short photoperiods across all temperatures, (3) developmental times of larvae producing diapause pupae were longer than for those producing nondiapause pupae, (4) rearing larvae at high temperatures and short photoperiods increased the diapause period for the pupal stage, (5) average pupal weights of diapause pupae (20.20 ± 2.27 mg) (mean ± SD) were higher than for nondiapause pupae (18.01 ± 3.31), and (6) fresh pupae weighing

Published bi- and tri-trophic physiologically based demographic system models having similar sub components are used to assess prospectively the geographic distributions and relative abundance (a measure of invasiveness) of six invasive herbivorous insect species across the United States and Mexico. The plant hosts and insect species included in the study are: 1) cotton/pink bollworm, 2) a fruit tree host/Mediterranean fruit fly, 3) olive/olive fly, 4) a perennial host/light brown apple moth, 5) grapevine/glassy-winged sharpshooter and its two egg parasitoids, and 6) grapevine/European grapevine moth. All of these species are currently or have been targets for eradication. The goal of the analyses is to predict and explain prospectively the disparate distributions of the six species as a basis for examining eradication or containment efforts against them. The eradication of the new world screwworm is also reviewed in the discussion section because of its pivotal role in the development of the eradication paradigm. The models used are mechanistic descriptions of the weather driven biology of the species. Observed daily weather data (i.e., max-min temperatures, solar radiation) from 1,221 locations across the United States and Mexico for the period 1983-2003 were used to drive the models. Soil moisture and nutrition were assumed nonlimiting. The simulation results were mapped using GRASS GIS. The mathematical underpinnings of the modeling approach are reviewed in the appendix and in the supplemental materials. © 2013 Entomological Society of America.

The specific mechanisms of host plant resistance in alfalfa, Medicago sativa L., to the spotted alfalfa aphid, Therioaphis trifolli f. maculata (Buckton), remain unknown despite three decades of research. Difficulties with Painter's commonly used concept of host plant resistance were avoided when the Salt/Doutt paradigm of host selection by a parasite was used instead. Mechanisms of host plant resistance proposed in the literature were reviewed with respect to this alternative concept. Published results on the effects of host plant resistance are not comparable across different studies because of arbitrary measurements used. This problem is avoided with the use of laboratory age-specific life tables. In this study, four alfalfa cultivars were tested for host plant resistance to the spotted alfalfa aphid at three temperatures, and the statistical tools needed for the analysis are presented. The intrinsic rate of natural increase ( r m) was used as the measure of aphid performance on each cultivar. At the same temperature, r m values of the spotted alfalfa aphid on susceptible plants were significantly higher than on resistant cultivars. A developmental threshold of 7.9°C was estimated from the data, and the optimal temperature for growth and reproduction of this aphid was ≈21°C. Life tables of two successive generations of the spotted alfalfa aphid on a resistant cultivar indicated that aphids do not transmit the capacity to overcome resistance in a simple Mendelian fashion. A mechanism involving the random transmission of internal symbionts required by this aphid to overcome alfalfa resistance is hypothesized.

A model for pink bollworm (PBW) diapause in response to decreasing photoperiod and fluctuating temperatures developed in California using a wild Arizona biotype is used to explain diapause induction, termination, and adult flight phenology of PBW under Brazilian conditions. The model suggests that the Arizona and Brazil biotypes do not differ in their diapause response, which is considerably broader than required to survive the conditions in the areas examined.

The interaction between bollworm and boll weevil and cotton development has been assessed under the climatic conditions of Nicaragua. The ratio of the rate of fruit point production to the rate of cumulative fruit damage (βT/β2) has been used to assess final yields in treated and untreated fields. An economic decision rule for pesticide applications was developed from these data.

A population model of cotton growth and development in response to weather, agronomic factors, and insect pests has been successfully used to examine cotton production in California. The impact of most arthropod pests on cotton yields is currently under investigation. Only the effects of defoliating insects, Spodoptera exigua (Hubner), Trichoplusia ni (Hubner), and Heliothis zea (Boddie), are reported here. The impact of moderate defoliation by S. exigua and T. ni populations causes only slight yield reductions. More important is the predation by S. exigua larvae on immature fruit (i.e., squares). Investigations on the interaction of plant age and developmental stage with defoliator damage (defoliation and predation on squares) indicates that the greatest yield reductions occur from attack early in the squaring period. The late season effects of H. zea are easy to measure and incorporate into the model.

Methods arc presented for estimating upper and lower thermal thresholds for walnut aphid development from field data. Age-specific life table techniques are also applied to field data to examine the effects of favorable and unfavorable temperatures on life table parameters. High-temperature extremes were found to delay development, shorten adult longevity, and reduce fecundity. As a consequence, the net reproductive rate and intrinsic rate of increase were reduced and the population doubling time lengthened as compared with life table parameters measured under more favorable temperature conditions.

The microhabitat distribution and spatial dispersion patterns of walnut aphid eggs and viviparae were assessed in a commercial walnut orchard in Tracy, Calif., during 1977 and 1978. Significantly higher egg densities were found on the smaller peripheral branches of walnut trees (1–2 cm diam) than on larger branches. Few eggs were found on extremely small twigs (ca. 0.55 cm diam) from the previous season's growth. Significant differences in egg density were sometimes observed between top and bottom regions and among cardinal quadrants of the tree. No significant differences in egg density were observed among tree. The spatial dispersion patterns determined for walnut aphid eggs were generally aggregated except at extremely low densities where the pattern was random. No significant differences in aphid density were observed among cardinal quadrants of the trees and only occasional differences were observed between top and bottom regions of the trees. Substantial variation in aphid density was observed among basal, middle, and terminal regions of the trees. Few significant differences in aphid density were observed among trees and none was observed among compound leaves. Significantly higher aphid densities were found on the middle and distal leaflets of compound leaves. Within-tree, among-tree, and among-compound leaf distribution patterns showed that the aphids were generally aggregated.

Populations of Mononychellus tanajoa (Bondar) increased on new leaf growth of cassava, Manihot esculenta Crantz, during the early dry season, averaging 20–200 active mites per leaf depending on plant age, leaf age, and cultivar. Mite populations declined later in the dry season, when severe defoliation and reduced leaf production followed prolonged drought. Early rains resulted in a flush of new foliage that supported an increase in mite numbers, but rainfall drove mite populations to less than one individual per leaf several months into the wet season. Throughout the growing season, mite age structure was relatively constant within, but varied between, strata of the canopy. Differences between strata were related to the age of the foliage. These results suggest that the availability of new foliage and the presence of rainfall are the primary factors limiting M. tanajoa populations in Africa.

Least-squares models were fit to data from 216 experiments on the effects of decreasing photoperiod and fluctuating temperatures on diapause induction and termination in pink bollworm, Pectinophora gossypiella Saunders. The diapause induction model compared very favorably with field data collected from various locations in southern California and Arizona. The times required for termination of diapause in larvae reared from the diapause induction experiments increased under high fluctuating temperatures and short decreasing photoperiods, whereas long day length and low temperatures (within limits) decreased it. A model is proposed which links the results of the diapause induction and diapause termination studies and estimates the pattern of diapause termination the following spring.

The incorporation of pesticide resistance into a realistic economic optimization model of the interaction of Egyptian alfalfa weevil populations (EAW = Hypera brunneipennis (Boh.)) and alfalfa ( Medicago sativa (L.)) is described. The model has 4 components: the population dynamics of the weevil; the dynamics of the crop; pesticide induced mortality; and the evolution of resistance in the weevil population. The paper presents the optimal within season and long-term pesticide spraying patterns after resistance develops for 2 cases: with and without information on the developments of resistance.

Environ. Entomol 11: 251-254 (1982) This paper reports the within- lant distribution of cabbage looper on cotton through results in a greater proportion of eggs being oviposited on mainstem leaves, and closer to the mainstem terminal. As the plants age and increase in size, the eggs are found higher on the plant. The larvae appear to prefer leaves 5 to 10 nodes from the terminal. The average age of leaves being consumed by cabbage looper is estimated. A sampling plan for cabbage looper eggs based on mainstem leaves for estimating the optimal sample size for a iven level of reliability is presented, taking into account plant age, time. Mainstem leaves receive t i e largest percentage of eggs. Increased plant density