Economic Benefits of Bt Maize Maize containing a transgenically expressed toxin originating from Bacillus thuringiensis (Bt maize) is planted across the United States to combat insect herbivory. Non-Bt Maize is also planted alongside Bt maize fields to provide refuges for the insects, which helps to prevent resistance to Bt maize from evolving. Hutchison et al. (p. 222 ; see the Perspective by Tabashnik ) analyzed how Bt maize affected the economic impact of the European corn borer moth in the midwestern United States, as well as its population dynamics. Larval density, a predictor of corn borer population size, has dropped in correlation with the percentage of Bt maize planted. In the highest Bt maize producing state, the positive effects of Bt maize in controlling insect herbivore populations extended to non-Bt maize. Furthermore, the decrease in insect populations demonstrated an overall economic benefit outweighing the overall extra costs associated with planting Bt maize.

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1 Aphid populations may show strong year-to-year fluctuations, but questions remain regarding the dominance of factors that cause this variation, especially the role of natural enemies. To better understand the dynamics of aphid species that occur as pests in cereals, we investigated the relative influence of top-down control by a predator and weather (temperature and precipitation) on population fluctuations of three cereal aphid species. 2 From 1987 to 2005, populations of Metopolophium dirhodum , Sitobion avenae and Rhopalosiphum padi in insecticide-free stands of winter wheat were monitored in the Praha-Ruzyné region of the Czech Republic. Densities of an aphidophagous predator, the ladybeetle Coccinella septempunctata , were recorded from an overwintering site in the landscape. Weather was quantified using historical records. 3 A significant bottom-up effect of densities of aphids on those of C. septempunctata was found, but evidence of direct top-down regulation of aphids by C. septempunctata was only significant in the case of R. padi . There was no significant periodicity in the dynamics of the aphid or C. septempunctata , suggesting that there was no clear predator-prey cycle. Combinations of C. septempunctata and weather variables could be used to explain M. dirhodum and R. padi per capita rate of change. There were also indications that weather directly affected peak density of M. dirhodum . 4 We conclude that regional estimates of C. septempunctata densities are not sufficient to determine whether aphid population dynamics are driven by predatorprey interactions. Feasibility of time series analysis as an investigative tool in aphid population dynamics studies is discussed. , 73-82 2 was negative and the randomization procedure indicated lack of first-order density dependence ( P = 0.59). 78 T. W. Leslie et al.

Many ecological studies have focused on the effects of transgenes in Þeld crops, but few have considered multiple transgenes in diversiÞed vegetable systems. We compared the epigeal, or soil surface-dwelling, communities of Coleoptera and Formicidae between transgenic and isoline vegetable systems consisting of sweet corn, potato, and acorn squash, with transgenic cultivars expressing Cry1(A)b, Cry3, or viral coat proteins. Vegetables were grown in replicated split plots over 2 yr with integrated pest management (IPM) standards deÞning insecticide use patterns. More than 77.6% of 11,925 insects from 1,512 pitfall traps were identiÞed to species, and activity density was used to compare dominance distribution, species richness, and community composition. Measures of epigeal biodiversity were always equal in transgenic vegetables, which required fewer insecticide applications than their near isolines. There were no differences in species richness between transgenic and isoline treatments at the farm system and individual crop level. Dominance distributions were also similar between transgenic and isoline farming systems. Crop type, and not genotype, had a signiÞcant inßuence on Carabidae and Staphylinidae community composition in the Þrst year, but there were no treatment effects in the second year, possibly because of homogenizing effects of crop rotations. Communities were more inßuenced by crop type, and possibly crop rotation, than by genotype. The heterogeneity of crops and rotations in diversiÞed vegetable farms seems to aid in preserving epigeal biodiversity, which may be supplemented by reductions in insecticide use associated with transgenic cultivars.

The invasive brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), has been an important agricultural pest in the Mid-Atlantic United States since its introduction in 1996. Biological control by native species may play an important role in suppressing H. halys populations and reduce reliance on chemical control. We collected H. halys adults in agricultural areas of five Pennsylvania counties over two years to examine the extent and characteristics of adult stink bug parasitism by Trichopoda pennipes (Diptera: Tachinidae), a native parasitoid of hemipterans. The overall parasitism rate (in terms of T. pennipes egg deposition) was 2.38 percent. Rates differed among counties and seasons, but not between years. Instances of supernumerary oviposition were evident, and eggs were more commonly found on the ventral side of the thorax, although no differences in egg deposition were found between males and female hosts. T. pennipes has begun to target H. halys adults in Pennsylvania and has the potential to play a role in regulating this pest. Adult parasitism of H. halys by T. pennipes should continue to be monitored, and landscape management and ecological pest management practices that conserve T. pennipes populations should be supported in agricultural areas where H. halys is found.

Using multiple locations and a series of field trials over 2 yr, we evaluated an integrated pest management program for Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) management in peppers involving biorational chemistries, inundative releases of Trichogramma ostriniae (Pang & Chen), and conservation of generalist predators. In small plot trials, three biorational insecticides (spinosad, indoxacarb, and methoxyfenozide) provided comparable control of O. nubilalis as two broad-spectrum conventional insecticides (acephate and lambda-cyhalothrin). However, lambdacyhalothrin at most locations, and indoxacarb at one location, resulted in outbreaks of green peach aphids. We also observed significant effects on the generalist predator community: beneficial communities in methoxyfenozide-treated plots were most similar to untreated controls, and acephate-treated plots were the least similar. Management systems comparing untreated controls, inundative release of T. ostriniae with methoxyfenozide applied when lepidopterans exceeded thresholds, or weekly applications of acephate or lambda-cyhalothrin, showed no effects on marketable fruit or percentage of fruit damaged, but the conventional insecticide approach caused aphid flares. Inundative releases of T. ostriniae and biorational chemistries provide a more environmentally sound approach to managing O. nubilalis in peppers, due, in part, to conservation of generalist predators.