Timing of Fungal Insecticide Application to Avoid Solar Ultraviolet Irradiation Enhances Field Control of Rice...

Area of Science:

• Agricultural Entomology
• Biological Pest Control
• Mycology

Background:

• Chemical control of rice planthoppers (RPH) is restricted in rice-shrimp rotation systems.
• Rice planthoppers, particularly Nilaparvata lugens, pose a significant threat to rice cultivation.
• Sustainable pest management strategies are crucial for integrated farming systems.

Purpose of the Study:

• To evaluate the efficacy of fungal insecticides Beauveria bassiana ZJU435 and Metarhizium anisoplae CQ421 against RPH in rice-shrimp rotation fields.
• To investigate the impact of application timing (solar UV avoidance vs. exposure) on the efficacy of fungal insecticides.
• To assess the potential of fungal biocontrol agents as an alternative to chemical pesticides.

Main Methods:

• Field trials were conducted over four weeks during high-temperature, high-sunlight conditions.
• Fungal insecticides Beauveria bassiana ZJU435 and Metarhizium anisoplae CQ421 were applied at 14-day intervals.
• Application timing was compared: before 10 a.m. (UV exposure) versus after 5:00 p.m. (UV avoidance).
• RPH population suppression was monitored throughout the trial period.

Main Results:

• Both Beauveria bassiana ZJU435 and Metarhizium anisoplae CQ421 demonstrated effective control of RPH populations.
• Fungal sprays applied after 5:00 p.m. (UV avoidance) showed significantly higher control efficacy compared to morning applications (UV exposure).
• Mean control efficacies for UV-avoiding sprays ranged from 56% to 84%, while UV-exposed sprays ranged from 45% to 80% over 28 days.
• Effective protection of rice crops from tillering to flowering stages was observed.

Conclusions:

• Fungal insecticides are a viable and effective method for controlling rice planthoppers in rice-shrimp rotation systems.
• Application timing is a critical factor; evening applications enhance fungal insecticide efficacy by avoiding detrimental solar UV radiation.
• This study provides valuable insights for optimizing biocontrol strategies in agricultural pest management, particularly during sunny summer conditions.