Toxicity, Penetration, and Metabolism of Acephate in Three Fruit Fly Species (Diptera: Tephritidae)

Abstract

Topical toxicity of acephate and methamidophos to Mediterranean fruit fly, Ceratitis capitata (Wiedemann); oriental fruit fly, Dacus dorsalis Hendel; and melon fly, D. cucurmbitae Coquillet, was assessed over a 20-d observation period. Mortality caused by acephate stabilized 2 d after treatment for C. capitata and 4 d for the Dacus species. LD50s and their fiducial limits for female C. capitata, D. cucurmbitae , and D. dorsalis were 6.72 /µg/g (6.08-7.81), 1.46 /µg/g, and 0.84 /µg/g (0.82-0.87), respectively. The LD50, and fiducial limit for male C. capitata was 14.20 /µg/g (12.11-18.62). LD50s for D. cucurmbitae and D. dorsalis males and females were similar. Mortality caused by methamidophos stabilized 1 d after treatment for C. capitata and 2 d for Dacus species. LD50s and their fiducial limits for female C. capitata, D. cucurmbitae , and D. dorsalis were 0.90 /µg/g (0.53-1.08), 0.80 µg/g (0.74-0.95), and 0.80 /µg/g (0.77-0.84), respectively. LD50, s were similar for males and females. Faster penetration, internal accumulation, and excretion of acephate in C. capitata compared with the Dacus species accounted for the faster toxic action observed. Lack of significant differences in metabolism between C. capitata females and males indicated that the toxicological differences between the sexes cannot be explained by the results of this study. Dacus species produced significantly higher levels of methamidophos than C. capitata thus explaining their higher susceptibility to acephate. Higher levels of tissue-bound radioactivity were found in D. cucurmbitae than in the other two species.