Does refuge spillover affect arthropod food webs associated with Bt maize?

Area of Science:

• Agricultural Entomology
• Ecology
• Pest Management

Background:

• The high dose/refuge strategy using Bacillus thuringiensis (Bt) crops is recommended to slow insect resistance.
• This tactic involves planting Bt crops with high Bt protein expression alongside non-Bt refuges.
• Concerns exist regarding the strategy's effectiveness, adoption, and impact on non-target arthropod communities due to potential spillover effects.

Purpose of the Study:

• To investigate the spillover of targeted and non-targeted arthropods between Bt maize and adjacent non-Bt refuge areas.
• To assess the impact of refuge proximity on arthropod community structure and food web metrics within Bt maize fields.

Main Methods:

• Arthropod communities were surveyed along transects from refuge borders into Bt maize fields.
• Sampling occurred throughout the maize vegetative and reproductive stages.
• Richness, abundance, and food web metrics were analyzed in relation to distance from the refuge and cultivation season.

Main Results:

• A total of 85 arthropod species were identified, with no significant variation in richness or abundance based on distance from the refuge.
• Arthropod communities were significantly influenced by the cultivation season, not by refuge proximity within Bt fields.
• Winter maize cultivation showed higher arthropod diversity and biomass across trophic levels.

Conclusions:

• No arthropod spillover was detected between Bt maize and refuge areas.
• The findings question the practical impact and cost-benefit of the high dose/refuge strategy, as neither target nor non-target species were affected by spillover.
• The study adds to the controversy surrounding this pest resistance management tactic, particularly in regions with lower adoption rates.