Compatibility of Insecticides with Rice Resistance to Planthoppers as Influenced by the Timing and Frequency of...

Area of Science:

• Agricultural Entomology
• Pest Management
• Plant Breeding

Background:

• The brown planthopper (BPH) is a significant rice pest in Asia.
• Integrated pest management strategies often combine host plant resistance with chemical insecticides.

Purpose of the Study:

• To evaluate the efficacy of seven insecticides when used with resistant rice varieties against BPH.
• To determine synergistic, redundant, or antagonistic interactions between insecticides and host resistance.

Main Methods:

• Screenhouse experiments using resistant (IR62) and susceptible (IR64) rice varieties infested with BPH.
• Application of seven insecticides (buprofezin, carbofuran, cartap hydrochloride, cypermethrin, deltamethrin, fipronil, thiamethoxam + chlorantraniliprole) at different timings and frequencies.
• Assessment of BPH biomass densities and rice yields.

Main Results:

• Carbofuran and fipronil reduced BPH densities, but host resistance was redundant.
• Synergistic effects between insecticides (cartap hydrochloride, cypermethrin, buprofezin) and host resistance were observed with single applications at specific timings.
• Multiple applications and other insecticide/timing combinations showed redundancy; deltamethrin with multiple applications was antagonistic.
• Insecticide applications did not significantly improve yields of infested resistant rice; late applications reduced yields of non-infested rice.

Conclusions:

• The interaction between insecticides and host resistance is complex and depends on the specific insecticide and application strategy.
• Prophylactic insecticide use may destabilize BPH populations and reduce the economic benefits of resistant rice varieties.
• Careful selection of insecticides and application timing is crucial for effective and sustainable BPH management.