Abstract
This study investigated alternative in-field chemical controls against Bactrocera tryoni (Froggatt). Bioassay 1 tested the mortality of adults exposed to fruit and filter paper dipped in insecticide, and the topical application of insecticide to adults/fruit. Bioassay 2 measured the mortality of adults permitted to oviposit on fruit dipped in insecticide and aged 0, 1, 3, or 5 days, plus the production of offspring. Bioassay 3 tested infested fruit sprayed with insecticide. The field bioassay trialed the mortality of adults exposed to one- and five-day insecticide residues on peaches, and subsequent offspring. Abamectin, alpha-cypermethrin, clothianidin, dimethoate (half-label rate), emamectin benzoate, fenthion (half- and full-label rate), and trichlorfon were the most efficacious in bioassay 1, across 18 tested insecticide treatments. Overall, the LT50 value was lowest for fenthion (full-label rate), clothianidin, and alpha-cypermethrin. Fenthion, emamectin benzoate, and abamectin had the greatest effect on adult mortality and offspring production. Infested fruit treated with acetamiprid, fenthion, and thiacloprid produced no/very few offspring. Alpha-cypermethrin demonstrated good field efficacy against adults (one day post treatment: 97.2% mortality, five day post treatment: 98.8% mortality) and subsequent offspring (100% across one and five day post treatments), comparable to that of fenthion (full-label rate) (100% mortality for offspring and adults across both post treatments). Alpha-cypermethrin is a possible alternative to fenthion against B. tryoni; as a pyrethroid, it may not be desirable if adjunct biological control is imperative. Thiacloprid and Acetamiprid may be useful as a post-harvest treatment.
Highlights
The genus Bactrocera (Diptera: Tephritidae) includes approximately 500 described species, most of which are endemic to Southeast Asia and South Pacific islands [1]
As abamectin is derived from a Streptomyces spp. and is not long lived in comparison with the pyrethroid alpha-cypermethrin, it is considered the more environmentally-friendly specimen and was chosen to study in bioassay 2
When stone fruit was dipped in insecticide and exposed to adult flies, to mimic a cover spray followed by wild flies subsequently moving into the area, the traditional insecticides used in B. tryoni control, the organophosphates dimethoate and fenthion, showed the highest efficacy
Summary
The genus Bactrocera (Diptera: Tephritidae) includes approximately 500 described species, most of which are endemic to Southeast Asia and South Pacific islands [1]. 70 polyphagous Bactrocera species attack commercial fruit and vegetable crops, and are a serious obstacle to international trade [2,3]. In Australia, the Queensland fruit fly, Bactrocera tryoni (Froggatt), is the most significant biosecurity pest affecting Australia’s $9 billion-plus per annum horticultural industry, including both domestic and international markets. This species attacks most fruit and Insects 2017, 8, 49; doi:10.3390/insects8020049 www.mdpi.com/journal/insects. Insects 2017, 8, 49 many vegetable crops, with over 240 reported hosts [4]. The majority of domestic and international markets have nil tolerance for B. tryoni
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