In New York state, there are three races of European corn borer moths, which are characterized principally by differences in voltinism and the sex pheromone communication system. One race is bivoltine, with females producing and males responding to a 99:1 EIZ isomeric ratio of~1l-14:0Ac's as the sex pheromone. Two races, one univoltine and one bivoltine, produce and respond to a 3:97 E 12 blend of~1l-14 :OAc·s. The races are referred to as BE, UZ, and BZ to denote these differences. Analyses by gas chromatography of field-collected females indicate that there is significant hybridization between the Z and E races when in sympatry, with hybrid females producing a 68:32 ratio of E/Zl1-14:OAc. Gene flow among the races was investigated using differences in triose phosphate isomerase (TPI) allozyme frequencies of moths from sites sampled across the state. The fixed nature of the Tpi-l allele in the BE race and increases in the Tpi-l allele frequencies in UZ populations in sympatry with the BE race support the hypothesis that gene flow following hybridization is unidirectional from BE populations into the Z populations. In addition, the TPI genotypes of the 10 hybrid females analyzed were consistent with hybridization occurring by E males mating with Z females.

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Northern, Diabrotica barberi Smith & Lawrence, and western, D. virgifera virgifera LeConte, corn rootworms (Coleoptera: Chrysomelidae) are major economic pests of corn, Zea mays L., in North America. Corn hybrids expressing Bacillus thuringiensis Berliner (Bt) toxins are commonly used by growers to manage these pests. Several cases of field-evolved resistance to insecticidal proteins expressed by Bt corn hybrids have been documented in many corn-producing areas of North America, but only for D. v. virgifera. In 2016, beetles of both species were collected from five eastern North Dakota corn fields and reared in a growth chamber. In 2017, larvae reared from those populations were subjected to single-plant bioassays to screen for potential resistance to Cry3Bb1, Cry34/35Ab1, and pyramided Cry3Bb1 + Cry34/35Ab1 Bt toxins. Our results provide the first documented report of field-evolved resistance in D. barberi to corn hybrids expressing Cry3Bb1 (Arthur problem population) and Cry34/35Ab1 (Arthur and Page problem populations, and the Ransom and Sargent populations) proteins in North America. Resistance to Cry3Bb1 was also observed in the Ransom population of D. v. virgifera. Increased larval survival on the pyramided Cry3Bb1 + Cry34/35Ab1 hybrid was observed in both species. No cross-resistance was evident between Cry3Bb1 and Cry34/35Ab1 in any of the D. barberi populations tested. Our experiments identified field-evolved resistance to Bt toxins in some North Dakota populations of D. barberi and D. v. virgifera. Thus, more effective control tools and improved resistance management strategies are needed to prolong the durability of this technology for managing these important pests.

These data demonstrate that an IPM approach, combining scouting and foliar-applied insecticide where necessary, remains the best option for treatment of soybean aphids, both in terms of protecting the yield potential of the crop and of break-even probability for producers. Furthermore, we found that thiamethoxam concentrations in foliage are unlikely to effectively manage soybean aphids for most of the pests' activity period across the region. © 2017 Society of Chemical Industry.

Landscape simplification associated with agricultural intensification has important effects on economically important arthropods. The declining cover of natural and semi-natural habitats, in particular, has been shown to reduce natural-enemy attack of crop pests, but also in some cases reduced crop colonization by such pests. In this study, we examined the influence of changes in two elements of landscape composition, natural grassland cover and cover of a highly suitable crop host, on infestation by a generalist insect pest in wheat, and parasitism of this pest by its dominant natural enemies. Surprisingly, we found no significant influences of increasing natural grassland habitat, at either local or landscape scales, on infestation by the wheat stem sawfly, Cephus cinctus, or parasitism of this pest by the native parasitoid wasps, Bracon cephiand Bracon lissogaster. In contrast, we found significant increases in levels of C. cinctus infestation with increasing wheat cover at the landscape scale. This pattern was consistent across six study regions spanning three states in the northern Great Plains of North America, despite large differences in cropping systems and pest population densities across regions. Regional variation in pest infestation was best explained by long-term averages in precipitation, with higher C. cinctus infestation rates found in drier regions. Results suggest that landscape-mediated variation in pest pressure in this system is better explained by a direct response of pest insects to increasing cover of a highly suitable crop rather than an indirect response via reductions in natural enemies as natural habitat declines. The implication is that habitat diversification at the landscape scale could play a role in suppressing agricultural pest populations via reductions in area of suitable crop hosts. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. b s t r a c tLandscape simplification associated with agricultural intensification has important effects on economically important arthropods. The declining cover of natural and semi-natural habitats, in particular, has been shown to reduce natural-enemy attack of crop pests, but also in some cases reduced crop colonization by such pests. In this study, we examined the influence of changes in two elements of landscape composition, natural grassland cover and cover of a highly suitable crop host, on infestation by a generalist insect pest in wheat, and parasitism of this pest by its dominant natural enemies. Surprisingly, we found no significant influences of increasing natural grassland habitat, at either local or landscape scales, on infestation by the wheat stem sawfly, Cephus cinctus, or parasitism of this pest by the native parasitoid wasps, Bracon cephi and Bracon lissogaster. In contrast, we found significant increases in levels of C. cinctus infestation with increasing wheat cover at the landscape scale. Thi...

Since the first observation of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in North America in 2000, it has become the most economically damaging insect of soybean in the Upper Midwest of the United States. For the last 17 yr, soybean aphid management has relied almost entirely on the use of foliar-applied broad-spectrum insecticides. However, in 2015 in Minnesota, failures of foliar-applied pyrethroid insecticides were reported and pyrethroid resistance was confirmed with laboratory bioassays using lambda-cyhalothrin and bifenthrin. In 2016 and 2017, further reports of failures of pyrethroid insecticides and/or laboratory confirmation of resistance occurred in Iowa, North Dakota, South Dakota, and Manitoba. In response to the challenge posed by insecticide-resistant soybean aphids, we recommend several management strategies for minimizing further development of resistance and subsequent pest-induced crop losses: 1) scout and use the economic threshold to determine when to apply insecticides, 2) apply the insecticides properly, 3) assess efficacy 3–5 d after application, and 4) alternate to a different insecticide group if another application is required. In the long term, soybean aphid management must move beyond insecticide-based management to true integrated pest management by incorporating multiple tactics.

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a major pest of wheat (Triticum aestivum L.) in the northern Great Plains of North America. The use of solid-stemmed cultivars helps mitigate crop losses and can also affect the survivorship of C. cinctus. The efficacy of a plant's resistance is based on its ability to develop pith in the culm of the stem, which is influenced greatly by interactions between the genotype and environment. Precipitation-related weather interacts with photoperiod to reduce pith expression in solid-stemmed wheat. A model that predicts pith expression could serve as a management tool to prevent losses by alerting producers if in-season precipitation patterns have caused less than ideal pith expression in a cultivar. Artificial Neural Network (ANN) models are used to make predictions for complex, non-linear systems with many co-related variables. Our objective was to improve upon past models that used regression analyses by deploying an ANN model to predict in-season stem cutting of wheat by wheat stem sawfly. Results indicate that stem cutting is influenced by the precipitation within a 5 wk period from 1 June to 5 July. These results were successfully deployed in a model that should assist with predictions of potential late season stem cutting. Deployment of this ANN model as a transferable executable file may facilitate predictions of stem cutting by wheat stem sawfly in any given year, which will empower producers to implement the appropriate harvest management strategies to reduce losses.Key words: Triticum aestivum L., host plant, bread wheat, solid-stemmed, sawfly, Cephus cinctus.Résumé : Dans le nord des grandes plaines nord-américaines, le cèphe du blé, Cephus cinctus Norton (Hymenoptera: Cephidae), est un important ravageur du blé (Triticum aestivum L.). L'usage de cultivars à tige pleine concourt à atténuer les pertes et peut affecter la capacité de survie de l'insecte. La plante résiste dans la mesure où elle réussit à produire de la moelle dans la tige, propriété qui subit considérablement l'influence des interactions entre le génotype et l'environnement. Un temps pluvieux modifiera la photopériode, ce qui réduira la synthèse de moelle chez les variétés à tige pleine. Un modèle qui prévoirait la production de moelle aurait son utilité en agronomie, car on pourrait alors éviter des pertes en signalant aux cultivateurs si les précipitations saisonnières engendrent une production insuffisante de moelle chez tel ou tel cultivar. On se sert des modèles à réseau neuronal artificiel (RNA) pour formuler des prévisions sur les systèmes complexes, non linéaires, comportant de nombreuses variables apparentées. Les auteurs voulaient améliorer les anciens modèles de prévision reposant sur l'analyse par régression en recourant à un modèle RNA pour établir l'importance des dommages causés par le cèphe au blé durant la période végétative. Les résultats obtenus indiquent que ces dommages sont influencés For personal use only.par l'intensité des précipitati...

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