Suppression of female melon fly, Zeugodacus cucurbitae(Coquillett)(Diptera: Tephritidae), with cue-lure and fipronil bait stations through horizontal insecticide transfer

Authors: SPAFFORD, HELEN - University Of Hawaii; CHIOU, MING-YI - University Of Hawaii; MAU, RONALD - University Of Hawaii; Vargas, Roger

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2017
Publication Date: 2/20/2018
Citation: Spafford, H., Chiou, M., Mau, R.F., Vargas, R.I. 2018. Suppression of female melon fly, Zeugodacus cucurbitae(Coquillett)(Diptera: Tephritidae), with cue-lure and fipronil bait stations through horizontal insecticide transfer. Entomologia Experimentalis et Applicata. 166(2):94-101.

Interpretive Summary: The Hawaii area-wide melon fly management program registered new technologies for farmers and homeowners that promoted the use of safer or reduced risk fruit fly protein baits and male lure traps or novel dispensers in what became popularly referred to as the “Easy as 1 (sanitation), 2 (protein bait), 3 (male lure mass trapping) Program” for melon fly control. One such male lure “attract and kill” product was Amulet Cue-Lure (C-L) Bait Stations (BASF, Triangle Park, NC) with fipronil. The efficacy of this approach was thought to be limited to individual male flies contacting the male lure. Horizontal insecticide transfer extends pesticide control from the individual to the population level through insect food sharing behavior. In field trials at a large melon farm near Honolulu,HI, ARS and University of Hawaii scientists conducted large field suppression trials and subsequent laboratory trials to examine the role of food regurgitation behavior for insecticide horizontal transfer from males to females. Female captures were significantly lower in bait station treated field plots than those in field plots treated with weekly protein bait spot treatments alone. In subsequent laboratory studies, direct toxicity transfer from male flies exposed to Amulet C-L for 1-4 minutes resulted in 100% female mortality within 6 hour. These findings are the first published field demonstration trials of Amulet C-L and horizontal transfer of fipronil to female melon flies in the laboratory and have important implications for improved Integrated Pest Management programs for fruit flies.

Technical Abstract: Melon fly, Zeugodacus cucurbitate (Coquillett),(Diptera:Tephritidae), is an important quarantine tephritid fruit fly with resident populations established in Hawai’i. Use of dispensers with cue-lure(C-L) in combination with organophosphate insecticides is a standard practice for suppression of male of Z.cucurbitae in Hawaii. However, there has been a need to investigate alternative “attract and kill” tactics that could be useful in fruit fly management. Fipronil has been included in the pest management tool box for male fruit fly suppression through development of Amulet C-L bait stations. However, the efficacy of this approach is thought to be limited to individual flies, males, contacting the lure. Horizontal insecticide transfer extends pesticide control from the individual to the population level through insect food sharing behavior. We tested the role of food regurgitation behavior for insecticide horizontal transfer in Z.curcurbitae in field and laboratory studies. Two repeated field trials were conducted to compare the effects of Amulet C-L (0.34% fipronil A.I.) bait stations as part of the Hawaii Area-Wide Z.cucurbitae IPM program at Aloun Farms, Kapolei,HI. In field plots treated with Amulet C-L bait stations in conjunction with sanitation and weekly protein bait spot treatments of GF-120 Fruit Fly Bait, female captures were significantly lower than those in field plots treated with weekly protein bait spot treatments alone. In subsequent laboratory studies, direct toxicity transfer from male flies exposed to Amulet C-L for 1-4 minutes resulted in 100% female mortality within 6h. Indirect toxicity transfer through regurgitation was determined by collecting regurgitated droplets from fipronil fed male flies and fed to males and females. Mortalities were higher for the C-L compound, compared to sugar compound and for males compared to females. However, there was 47% mortality for females, confirming the toxic effect of the regurgitate. These findings are discussed in the context of Z.cucurbitae IPM programs in Hawaii.