Natural enemies delay insect resistance to Bt crops

Area of Science:

• Agricultural Entomology
• Insect Ecology
• Biotechnology

Background:

• Insect resistance to Bt crops is a growing concern for sustainable agriculture.
• Biological control agents and non-Bt refuges are key components of integrated pest management (IPM).

Purpose of the Study:

• To determine if natural enemies slow Bt crop resistance development in Plutella xylostella.
• To assess the efficacy of biological control combined with Bt crops and refuges for pest suppression.
• To evaluate the impact of insecticide-sprayed vs. unsprayed refuges on resistance evolution.

Main Methods:

• Experiments utilized Bt broccoli expressing Cry1Ac and Plutella xylostella populations with pre-existing resistance.
• The natural enemy Coleomegilla maculata was introduced in various treatment groups.
• Multiple generations were monitored to assess pest population dynamics, crop damage, and resistance levels.

Main Results:

• Pest populations were lowest and resistance evolution significantly slower when natural enemies were present with unsprayed non-Bt refuges.
• Bt crops without refuges or natural enemies led to complete crop defoliation.
• Insecticide-sprayed refuges, while reducing pest numbers, accelerated resistance to Bt toxins.

Conclusions:

• Natural enemies play a crucial role in delaying insect resistance to Bt crops.
• Combining biological control with Bt crops and unsprayed refuges is a promising IPM strategy.
• The use of insecticide-sprayed refuges may inadvertently accelerate resistance, necessitating careful consideration in IPM programs.