Horizontal Transfer of Spinosad in Coptotermes formosanus (Isoptera: Rhinotermitidae)

Area of Science:

• Entomology
• Pest Management
• Environmental Science

Background:

• Termiticides that are slow-acting and nonrepellent can be transferred between nestmates (horizontal transfer).
• Spinosad is a potential candidate for this transfer mechanism.
• Understanding spinosad's horizontal transfer is crucial for effective termite control strategies.

Purpose of the Study:

• To investigate the horizontal transfer of spinosad in the termite Coptotermes formosanus Shiraki.
• To evaluate the efficacy of spinosad transfer in different substrates (sand and soil) and concentrations.
• To determine the factors influencing spinosad's bioavailability and transfer.

Main Methods:

• Coptotermes formosanus termites were exposed to spinosad (Entrust®) in sand and soil at 1, 25, and 50 ppm for 1 hour.
• Treated termites (donors) were mixed with healthy untreated termites (recipients) at a 1:1 ratio for 21 days.
• Termite mortality was recorded at 1, 3, 7, and 14 days post-treatment.

Main Results:

• Spinosad transfer was more effective in sand than in soil.
• Significantly high mortality in both donor and recipient termites was observed in sand at 25 and 50 ppm after 7 days.
• Exposure to treated soil for 21 days resulted in significantly higher mortality across all concentrations compared to controls.

Conclusions:

• Spinosad is effectively transferred horizontally by donor termites.
• The transfer and efficacy of spinosad are dependent on its bioavailability and concentration.
• Further field studies are necessary to assess spinosad's effectiveness against C. formosanus under natural conditions.