Estimation of efficacy functions for products used to manage corn rootworm larval injury

Abstract

Maize, Zea mays L., is an economically important crop grown throughout the world. Corn rootworm, Diabrotica spp. (Coleoptera: Chrysomelidae), larvae constitute a significant economic threat to maize production in the United States, where yield losses and management costs associated with corn rootworm species exceed $1 billion annually. Furthermore, the introduction of the western corn rootworm, D. virgifera virgifera LeConte, into maize‐producing regions of Europe has made managing corn rootworm larval injury an international concern. Larvae injure maize plants by feeding on root tissue and are the primary target of management activities. Products commonly used to protect root systems from injury include chemical insecticides (seed or soil applied) and genetically modified maize hybrids expressing toxins derived from Bacillus thuringiensis Berliner (Bt). The confirmation of field‐evolved resistance to various Bt toxins in populations of the western corn rootworm presents a significant management challenge. We performed a meta‐analysis to provide a broad understanding of the relative efficacy of the primary products currently being used to manage corn rootworm larval injury, including insecticidal seed treatments, soil insecticides and Bt hybrids (with and without the addition of soil insecticide). Our analysis is unique in the breadth of locations and years included – we analysed 135 individual trials conducted from 2003 through 2014 at multiple sites in both Illinois and Nebraska. Panel data were produced by pairing the mean node‐injury rating for each treatment of a given trial with the mean node‐injury rating for untreated maize. Linear regression models were developed to estimate the relationship between the potential for corn rootworm larval injury and product performance. For a given level of injury potential, the parameters estimated reveal differences in the degree of root protection offered by the various product categories analysed. Implications for developing long‐term, integrated, and sustainable practices for managing this important pest of maize are discussed.

Characterization of pyrethroid resistance in the western corn rootwormDiabrotica virgifera virgiferaLeConte

“…This study confirms that a relatively low level of WCR pyrethroid resistance detected in laboratory bioassays , Souza 2019) is enough to significantly reduce the performance of formulated soil-applied pyrethroid products in the field. A study that analyzed over a decade of research at multiple US maizeproducing sites indicated that nearly 86% less root injury occurred in conventional maize when a soil insecticide was applied in addition to a standard seed treatment (Tinsley et al 2015). Similar results were observed in this study, as treatments tested on the Saunders WCR pyrethroid-susceptible population provided 70-86% less root injury than untreated control plots.…”

“…Depending on the maize hybrid, pest infestation level, degree of abiotic stresses, and control strategies used, root damage by larval feeding may cause significant yield losses (Metcalf, 1986;Spike and Tollefson 1991;Davis 1994;Urías-López et al 2000;Urías-López and Meinke 2001;Tinsley et al 2013Tinsley et al , 2015. This insect pest also became a major concern for European countries after it was first found in 1992 close to Surcin International Airport in Belgrade (Berger 2001, Miller et al 2005).…”

Discovery of midgut genes for the RNA interference control of corn rootworm

“… 45 estimated that under field conditions, one node of root injury was on average associated with a corn yield loss of approximately 15–18%. Further studies are needed to confirm the efficacy 46 of dvssj1 events under field conditions 47 .…”

Discovery of midgut genes for the RNA interference control of corn rootworm

“…After 72 h of feeding, dvssj1 dsRNA treatment (100 ng μ l −1 ) resulted in an overall decrease in neonate length compared to untreated controls ( Supplementary Fig. 4a,b); in some cases, the gut [45][46][47][48] are killed by dsRNA at concentrations of 5 or 50 ng μ l −1 . Fragments of five active targets were selected for LT 50 determination based on dose response assay results (Table 1 and Supplementary Table 2).…”

“…Dun et al 44 and Tinsley et al 45 estimated that under field conditions, one node of root injury was on average associated with a corn yield loss of approximately 15-18%. Further studies are needed to confirm the efficacy 46 of dvssj1 events under field conditions 47 .…”