Dataset Information

Field Trial Performance of Herculex XTRA (Cry34Ab1/Cry35Ab1) and SmartStax (Cry34Ab1/Cry35Ab1 + Cry3Bb1) Hybrids and Soil Insecticides Against Western and Northern Corn Rootworms (Coleoptera: Chrysomelidae).

ABSTRACT: Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), and northern corn rootworm, Diabrotica barberi Smith and Lawrence (Coleoptera: Chrysomelidae), are important insect pests in corn, Zea mays L. For more than a decade, growers have been using transgenic plants expressing proteins from the bacterium Bacillus thuringiensis (Bt) to protect corn roots from feeding. In 2011, western corn rootworm populations were reported to have developed resistance to Bt hybrids expressing Cry3Bb1 and later found to be cross-resistant to hybrids expressing mCry3A and eCry3.1Ab. The identification of resistance to Cry3 (Cry3Bb1, mCry3A, and eCry3.1Ab) hybrids led to concerns about durability and efficacy of products with single traits and of products containing a pyramid of a Cry3 protein and the binary Bt proteins Cry34Ab1 and Cry35Ab1. From 2012 to 2014, 43 field trials were conducted across the central United States to estimate root protection provided by plants expressing Cry34Ab1/Cry35Ab1 alone (Herculex RW) or pyramided with Cry3Bb1 (SmartStax). These technologies were evaluated with and without soil-applied insecticides to determine if additional management measures provided benefit where Cry3 performance was reduced. Trials were categorized for analysis based on rootworm damage levels on Cry3-expressing hybrids and rootworm feeding pressure within each trial. Across scenarios, Cry34Ab1/Cry35Ab1 hybrids provided excellent root protection. Pyramided traits provided greater root and yield protection than non-Bt plus a soil-applied insecticide, and only in trials where larval feeding pressure exceeded two nodes of damage did Cry34Ab1/Cry35Ab1 single-trait hybrids and pyramided hybrids show greater root protection from the addition of soil-applied insecticides.

SUBMITTER: Johnson KD

PROVIDER: S-EPMC5444676 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Publications

Field Trial Performance of Herculex XTRA (Cry34Ab1/Cry35Ab1) and SmartStax (Cry34Ab1/Cry35Ab1 + Cry3Bb1) Hybrids and Soil Insecticides Against Western and Northern Corn Rootworms (Coleoptera: Chrysomelidae).

Johnson K D KD Campbell L A LA Lepping M D MD Rule D M DM

Journal of economic entomology 20170601 3

Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), and northern corn rootworm, Diabrotica barberi Smith and Lawrence (Coleoptera: Chrysomelidae), are important insect pests in corn, Zea mays L. For more than a decade, growers have been using transgenic plants expressing proteins from the bacterium Bacillus thuringiensis (Bt) to protect corn roots from feeding. In 2011, western corn rootworm populations were reported to have developed resistance to Bt hybri ...[more]

PMID: 28430986

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Project description:Bean leaf beetles (Ootheca spp.) (Coleoptera: Chrysomelidae) are one of Africa's most important pests of the common bean (Phaseolus vulgaris L.). Roots, leaves, floral parts, and young pods are all attacked, leading to a considerable loss in grain yield. In Uganda, there are no comprehensive prescribed management strategies for bean leaf beetles, but farmers typically try to control the pest by delaying bean crop sowing, and to a lesser extent, using insecticides. Although farmers have consistently implemented the two approaches, there is no information on the effects of the approaches in Uganda. To assess the impact of planting timing and insecticide spray regimes on bean leaf beetle populations, concomitant foliar damage, and grain yield, we set up trials in three agro-ecological zones with known presence of the beetles during the second rainy season of 2016 (2016) and the first rainy season of 2017 (2017). The first planting, coinciding with early planting, was conducted within one week after the onset of rains. The second planting, coinciding with mid planting, followed two weeks later, while the third planting, considered late planting in this study, was conducted one month after the second planting. A foliar application of cypermethrin commencing at 7 days after emergence (DAE), 14 DAE, 21 DAE, 28 DAE, and 35 DAE; a soil drench of imidacloprid at planting combined with a foliar spray starting at 7 DAE; and an untreated control were among the insecticide spray regimes evaluated. Higher bean leaf beetle abundance was recorded from mid-planting, while higher foliar damage was recorded from late planting in two of the three agro-ecological zones. However, higher marketable grain yield was recorded from early planting in all agro-ecological zones, suggesting that delayed planting may not be beneficial. Insecticide application reduced foliar damage and increased marketable grain yield, with a combination of soil drench and foliar spray resulting in much less foliar damage and, as a result, higher grain yield. However, this did not result in economic benefits. Furthermore, marketable grain yield was higher when insecticide spray regimes were combined with early planting in all agro-ecological zones during both seasons. Our findings suggest that the common bean should be planted early and that the control of the bean leaf beetle should target both the adults and the juvenile stages in the soil. Therefore, there is a need for farmers to be able to access less-expensive soil treatments.

Project description:Repeated use of field corn (Zea mays L.) hybrids expressing the Cry3Bb1 and mCry3A traits in Nebraska has selected for field-evolved resistance in some western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte) populations. Therefore, this study was conducted to characterize spatial variation in local WCR susceptibility to Cry3Bb1 and mCry3A traits in Keith and Buffalo counties, Nebraska, and determine the relationship between past management practices and current WCR susceptibility. Adult WCR populations were collected from sampling grids during 2015 and 2016 and single-plant larval bioassays conducted with F1 progeny documented significant variation in WCR susceptibility to Cry3Bb1 and mCry3A on different spatial scales in both sampling grids. At the local level, results revealed that neighboring cornfields may support WCR populations with very different susceptibility levels, indicating that gene flow of resistant alleles from high trait survival sites is not inundating large areas. A field history index, comprised of additive and weighted variables including past WCR management tactics and agronomic practices, was developed to quantify relative selection pressure in individual fields. The field history index-Cry3 trait survivorship relationship from year 1 data was highly predictive of year 2 Cry3 trait survivorship when year 2 field history indices were inserted into the year 1 base model. Sensitivity analyses indicated years of trait use and associated selection pressure at the local level were the key drivers of WCR susceptibility to Cry3 traits in this system. Retrospective case histories from this study will inform development of optimal resistance management programs and increase understanding of plant-insect interactions that may occur when transgenic corn is deployed in the landscape. Results from this study also support current recommendations to slow or mitigate the evolution of resistance by using a multi-tactic approach to manage WCR densities in individual fields within an integrated pest management framework.

Dataset Information

Field Trial Performance of Herculex XTRA (Cry34Ab1/Cry35Ab1) and SmartStax (Cry34Ab1/Cry35Ab1 + Cry3Bb1) Hybrids and Soil Insecticides Against Western and Northern Corn Rootworms (Coleoptera: Chrysomelidae).

Publications

Field Trial Performance of Herculex XTRA (Cry34Ab1/Cry35Ab1) and SmartStax (Cry34Ab1/Cry35Ab1 + Cry3Bb1) Hybrids and Soil Insecticides Against Western and Northern Corn Rootworms (Coleoptera: Chrysomelidae).

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