Mortality of Fruit Flies (Diptera: Tephritidae) Exposed to Spinetoram Toxic Bait in the Laboratory

Abstract

Fruit flies (Diptera: Tephritidae) cause significant losses during the production and marketing of horticultural products. Brazilian growers usually adopt full-coverage insecticide spraying to control fruit flies, but toxic bait is a more strategic technique, because reach efficacy and the target surface is the foliage and branches. We provide information regarding the toxicity of spinetoram bait to two fruit fly species in the laboratory as an alternative to organophosphates and the specific spinosad formulation. We tested toxic baits in the laboratory, using commercial hydrolysed corn protein (10% v/v) plus 90 g, 120 g, 150 g and 180 g dilutions of spinetoram 250 WG (commercial product/1,000 litres of water). All toxic baits were compared with an untreated control (only protein) for the adults of females and males of Anastrepha obliqua (Macquart, 1835) and Ceratitis capitata (Wiedemann, 1824) up to 30 hours of exposure. Dry food for adults was included in all dilutions (5% w/v). In addition, we tested the residual effect of toxic baits applied to the leaves of mandarin seedlings. We used the same treatments of the earlier bioassay without dry food, collecting treated leaves and exposing them to C. capitata (medfly) females for 24 hours in the laboratory. Leaves were collected 1, 3, 7, 15 and 30 days after application. Overall, medfly adults were more susceptible to spinetoram baits than A. obliqua. All toxic baits resulted in 100% C. capitata mortality 24 hours after initial exposure, and the toxic bait at 150 g/1,000 L of water resulted in the maximum mortality (96%) in A. obliqua. Except for 90 g of spinetoram bait at 30 days after application, all spinetoram bait concentrations resulted in significantly, more dead C. capitata females than the control over all tested periods in the residual bioassay. At 30 days after application, spinetoram baits at 120 g, 150 g and 180 g resulted in 85%, 87% and 86% mortality in C. capitata, respectively. Spinetoram toxic baits have proven promising for long-term fruit fly management.