Coating combined with dimethoate as a quarantine treatment against fruit flies (Diptera: Tephritidae)

Grapefruits infested with Caribbean fruit fly, Anastrepha suspensa (Loew), larvae were coated with Nature Seal containing 1.5% hydroxypropyl cellulose or Sta-Fresh 360 HS with or without 300 ppm dimethoate. Another treatment was dipped in 300 ppm dimethoate in water, and a final group of infested grapefruits remained untreated (control). Coating or dimethoate alone reduced the number of Caribbean fruit fly larvae emerging from grapefruits significantly (95% confidence level). The combination of coating plus dimethoate yielded 93-98.7% less larvae than either coating or dimethoate alone. Dimethoate residues in the pulp of grapefruits coated with Sta-Fresh 360 HS plus dimethoate (<0.005 ppm) were lower than residues in grapefruits coated with Nature Seal plus dimethoate (0.014 ppm) or dimethoate in water (0.009 ppm) three days after coating. These studies show that the combination of coating plus dimethoate may serve as a quarantine treatment for fruits infested with tephritid fruit flies. This combination treatment would allow lower doses of dimethoate than current dimethoate dips.