Nutrition affects insect susceptibility to Bt toxins

Area of Science:

• Entomology
• Insect Physiology
• Pest Management

Background:

• Pesticide resistance is a major threat to global food security, primarily attributed to resistance alleles.
• Gene-by-environment interactions, particularly nutritional effects on susceptibility, are often overlooked in resistance studies.
• The cotton bollworm, Helicoverpa zea, prefers protein-biased diets for optimal performance.

Purpose of the Study:

• To investigate the influence of dietary protein-carbohydrate ratios on Helicoverpa zea susceptibility to the Bt endotoxin Cry1Ac.
• To determine if current Bt bioassay methodologies, often using carbohydrate-biased diets, accurately reflect field conditions.

Main Methods:

• Larvae of Helicoverpa zea were reared on diets with varying protein-carbohydrate content.
• Susceptibility to Cry1Ac was assessed using standard bioassay protocols.
• Larval survival and performance were measured under different dietary conditions.

Main Results:

• A 100-fold increase in the LC50 (lethal concentration for 50% of the population) was observed for larvae fed optimal, protein-biased diets compared to carbohydrate-biased diets.
• Significant diet-mediated variation in survival and performance was detected when larvae were challenged with Cry1Ac.
• Ecologically and physiologically mismatched diets in bioassays can lead to inaccurate assessments.

Conclusions:

• Dietary nutrition is a critical factor influencing insect susceptibility to Bt toxins.
• Current Bt resistance bioassays may overestimate susceptibility and underestimate resistance due to inappropriate diet compositions.
• Future research and pest management strategies should consider the role of nutrition in mediating pesticide efficacy.