Oral and Topical Toxicity of Fipronil to Melon Fly and Oriental Fruit Fly (Diptera:Tephritidae)

Abstract

The objective of this study was to develop oral and topical toxicity data for fipronil in Solulys protein bait to wild melon fly, Bactrocera cucurbitae (Coquillett), and the oriental fruit fly, Bactrocera dorsalis (Hendel). For the oral study, both females and males were evaluated, whereas in the contact study only females were evaluated. The 24 h oral LC50 estimates for female B. cucurbitae and B. dorsalis were 113 and 108 mg ai/l, respectively. Female B. cucurbitae were more susceptible than males, but female and male B. dorsalis were equally susceptible to fipronil after the oral route of exposure. Female B. cucurbitae were significantly less susceptible to the fipronil-bait mixture after topical exposure compared with feeding exposure. However, female B. dorsalis were equally susceptible to either route of exposure. At the LC50, B. dorsalis was significantly more susceptible than B. cucurbitae by the topical route of exposure. At the LC90, B. dorsalis was significantly more susceptible than B. cucurbitae by both oral and topical routes of exposure. Results of this study indicate that there are differences In susceptibility between B. cucurbitae and B. dorsalis to fipronil, especially at the LC90. Bactrocera dorsalis was more susceptible to fipronil than B. cucurbitae by oral and topical routes of exposure. LC90 estimates were significantly lower than the 5,333 mg ai/l applied to Amulet Attract and Kill Stations for control of B. cucurbitae and B. dorsalis.