Author：Ming-Yi Chou ^{1, 5}, Yu-Bing Huang ², Horace C. Peng ³, Yi-Yuan Chuang ³, and Roger I. Vargas ⁴

¹ Agricultural Extension Center, National Chung Hsing University, Taichung, Taiwan, ROC
² Taiwan Agricultural Research Institute, Council of Agriculture, Executive Yuan, Taichung, Taiwan, ROC
³ Department of Entomology, National Chung Hsing University, Taichung, Taiwan, ROC
⁴ United States Department of Agriculture, Agricultural Research Service, Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, Hilo, Hawaii, USA
⁵ Corresponding author, e-mail: mingyichou@dragon.nchu.edu.tw

ABSTRACT

    Insecticide horizontal transfer extends pesticide efficacy from individual level to population-wide control through insect food sharing behavior. Social insects and nonsocial insects with food sharing behavior were most studied subjects for the effects of insecticide horizontal transfer. Very little was known about the food sharing behavior among tephritid fruit fly species, a group of serious pests of fruit commodities in tropical and subtropical area worldwide. Male oriental fruit fly (Bactrocera dorsalis (Hendel)) and melon fly (Zeugodacus cucurbitae (Coquillett)) are known to feed compulsively on methyl eugenol (ME) and cue lure (CL), respectively. These two semiochemicals in combination with broad-spectrum pesticides, i.e. organophosphate and carbamate, were the standard control tactics in the past decades. With the increasing environmental concerns for the use of broad-spectrum pesticides and that in turn cause the escalation of pesticide resistance indeed promoted the introduction of reduced-risk pesticides in recent years. This type of pesticide with strong bioactivity can cause fruit flies to regurgitate soon after ingesting insecticide-laced attractant. Insecticide horizontal transfer via fruit flies’ regurgitated droplets that contained insecticide active ingredient of chlorantraniliprole, acetamiprid, thiamethoxam, spinosad and fipronil were demonstrated in this paper. Field trials conducted in Hawaii demonstrated that not only male but also female Z. cucurbitae population density reduced significantly in the area treated with CL-fipronil. Laboratory studies further confirmed that droplets of regurgitated CL-fipronil caused high mortality in both male and female flies that received the regurgitated CL-fipronil within 24 h. Laboratory studies conducted in Taiwan demonstrated that exposing B. dorsalis males to individuals fed on MEspinosad and ME-thiamethoxam caused significantly higher mortality in male flies than that received ME-chlorantraniliprole and ME-acetamiprid treatments. Significantly higher female fly mortality was recorded in contacting flies that fed on ME-spinosad. Data from cage studies demonstrated that male flies did not show preference among ME-spinosad, ME-thiamethoxam and ME-acetamiprid regurgitants. The results from this study demonstrated that male annihilation technique using reduced-risk pesticides are suitable alternatives for organophosphates. The potential of employing insecticide horizontal transfer in fruit fly management was also discussed.

Keywords: Tephritidae, insecticide horizontal transfer, fipronil, spinosad, thiamethoxam, chlorantraniliprole

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