9: Impact of SmartStax PRO® dietary exposure on western corn rootworm (Coleoptera: Chrysomelidae) life history traits and fitness

The western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) is a pest of corn (Zea mays L.) across the U.S. Corn Belt. Field-evolved resistance to crop rotation, insecticides, and Bacillus thuringiensis (Bt) proteins has made WCR management increasingly difficult. New products with novel modes of action are needed to complement current tactics in WCR management programs.
SmartStax PRO®, containing two rootworm-active Bt proteins and DvSnf7 RNA, is the newest transgenic technology for WCR management to be deregulated in the United States. In 2018 and 2019, experiments were conducted to evaluate male and female fitness after dietary exposure to SmartStax PRO^®. WCR adults were collected from emergence tents in SmartStax PRO^® and control plots at a stewarded trial site in northeast Nebraska. Individual male/female pairs were maintained in the laboratory on various diets per experiment objectives. Life history traits measured included adult lifespan, adult size, egg production, and egg viability to characterize the impact of different diet combinations on WCR fitness. Results to date indicate that adult or lifetime dietary exposure to SmartStax PRO^® reduced adult WCR longevity and lifetime female egg production. Adult WCR size was only affected by exposure to SmartStax PRO^® in the larval life stage. Lifetime dietary exposure to SmartStax PRO^® significantly reduced both F₀ and F₁ WCR lifetime egg production, indicating that fitness costs may be passed to subsequent generation(s) and contribute to significant population suppression. Results are discussed within the framework of resistance management.