Spatio-Temporal Variation in Landscape Composition May Speed Resistance Evolution of Pests to Bt Crops

Area of Science:

• Agricultural Entomology
• Insect Pest Management
• Molecular Genetics

Background:

• Transgenic Bacillus thuringiensis (Bt) crops are vital for controlling moth and beetle pests.
• Widespread use of Bt crops can accelerate the evolution of insect resistance.
• Pyramid Bt crops use multiple toxins to combat pest resistance.

Purpose of the Study:

• To model the impact of spatio-temporal variation in Bt and non-Bt habitats on insect resistance evolution.
• To investigate how fluctuations in habitat availability affect selection intensity.
• To inform resistance management strategies for key agricultural pests.

Main Methods:

• Developed a mathematical model for a two-toxin Bt crop system.
• Incorporated spatio-temporal variation in Bt crop area (K) and non-Bt refuge proportion (Q).
• Analyzed effects on resistance evolution rates for cotton bollworm pests (Helicoverpa armigera, H. punctigera) using Australian field data.

Main Results:

• Variability in Q or K over time can increase resistance evolution rates through selection surges.
• High larval densities in refuges due to temporal variation can exacerbate selection.
• Even small proportions of Bt fields with sparse refuges can cause significant selection in a single generation.
• Rapid resistance evolution can occur when Bt crops are less common in the landscape.

Conclusions:

• Spatio-temporal dynamics of Bt and non-Bt habitats are critical for resistance management.
• Understanding landscape fluctuations is essential for designing effective strategies to delay Bt resistance.
• Management practices must account for temporal variations in habitat availability to maintain Bt efficacy.