Diet improvement for western corn rootworm (Coleoptera: Chrysomelidae) larvae

Abstract

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is the most serious insect pest of corn (Zea mays L.) in the United States and parts of Europe, and arguably one of the world’s most expensive pests to control. Several diet formulations are currently used by industry and public researchers to evaluate WCR larvae in diet-toxicity bioassays. However, a publicly available diet that produces normative insects that are physiologically similar to WCR larvae reared on corn roots will accelerate development of management technologies. We report a new diet formulation that supports improved weight gain, larval development and survival compared with the only public diet for WCR that is currently available in the refereed literature. The formulation was created by using response surface methods combined with n-dimensional mixture designs to identify and improve the formulation of key ingredients. Weight gain increased two-fold, and survival and molting rates increased from 93% and 90%, respectively when reared on the public diet, to approximately 99% for both survival and molting at 11 days when reared on our new formulation. This new formulation provides a standardized growth medium for WCR larvae that will facilitate comparison of research results from various working groups and compliance with regulatory requirements.

A new artificial diet for western corn rootworm larvae is compatible with and detects resistance to all current Bt toxins

“…Nutritional improvements of an artificial diet 35 and validation of compatibility with all current Bt proteins documented here, support the utility of the diet toxicity assay in resistance monitoring efforts. We recommend a standardized approach to how these diet toxicity assays are conducted to reduce data variability in IRM programs.…”

“…dsRNA) are possible using techniques described here and in Huynh et al . 35 . Consequently, we were able use molting as a measure of resistance, similar to studies with Ostrinia nubilalis (Hübner) 40 .…”

“…The lyophilized mCry3A and eCry3.1Ab proteins and their proprietary diet were provided by Syngenta Biotechnology. The WCRMO-1 diet was produced by the USDA-ARS Biological Control of Insects Research Laboratory (BCIRL) in Columbia, MO 35 . Buffers to suspend the protein in solution were prepared at BCIRL (Table 1 ).…”

“…The WCRMO-1 diet was prepared in new 96-well immunoassay plates (product #3370, Corning Inc., Corning, NY) using sterile techniques described in Huynh et al . 35 All proprietary diets were prepared in 96-well immunoassay plates by the registrants. For shipment, proprietary diets were placed in sterile packaging and shipped to the BCIRL in styrofoam containers with ice packs.…”

“…Efforts have been underway to improve WCR diets and the first new publicly available diet was recently published 35 . Referred hereafter as “WCRMO-1”, this diet has improved characteristics compared to the only other publicly-available diet 36 and all the proprietary diets used in the current study (Hibbard/Coudron labs unpublished data).…”