Assessment of toxic baits for the control of ants (Hymenoptera : Formicidae) in South African vineyards

[摘要] ENGLISH ABSTRACT: Ant infestations comprising the Argentine ant Linepithema humile (Mayr), commonpugnacious ant Anoplolepis custodiens (F. Smith) and cocktail ant Crematogasterperingueyi Emery are a widespread pest problem in South African vineyards.Integrated Pest Management (IPM) programmes aimed at suppressing theproblematic honeydew excreting vine mealybug Planococcus ficus (Signoret)(Hemiptera: Pseudococcidae) on grapes must include ant control to optimize theeffectiveness and efficacy of mealybug natural enemies. If ants are eliminated,natural enemies are able to contain mealybugs below the Economic Threshold Level(ETL). Current strategies for ant control are limited and generally include theapplication of long term residual insecticides that are detrimental to the environment,labour intensive to apply and can disrupt natural biological control if appliedincorrectly. A more practical method of ant control using low toxicity baits wastherefore investigated. Field bait preference and bait acceptance assessmentsaimed at determining bait repellency and palatability, respectively, were carried outduring spring, summer and autumn in three vineyards of the Cape winelands regionduring 2007/08. Five toxicants comprising gourmet ant bait (0.5%), boric acid(0.5%), fipronil (0.0001%), fenoxycarb (0.5%) and spinosad (0.01%) dissolved in25% sugar solution were tested against a 25% sucrose solution control. Gourmet antbait was significantly more preferred and accepted by all ant species than the otherbaits. Laboratory bait efficacy assessments using four insecticides (gourmet, boricacid & spinosad) at concentrations of 0.25; 0.5; 1; 2 and 4 times the field dose andfipronil at 0.015625; 0.03125; 0.0625; 0.125; 0.25 times the field dose were carriedout. Results revealed that boric acid (2%), gourmet ant bait (2%) and fipronil (1.0 X10-5%) exhibited delayed toxicity for L. humile and C. peringueyi while spinosad(0.01%) showed delayed action on L. humile. Field foraging activity and foodpreference tests were also carried out for the three ant species during 2007/08.Foraging activity trials revealed that vineyard foraging activity of L. humile is higherrelative to A. custodiens and C. peringueyi. This means fewer bait stations arerequired for effective L. humile control making low toxicity baits a more affordableand practical method of controlling L. humile than the other two ant species. Foodpreference trials showed that L. humile and C. peringueyi have a high preference forsugar while A. custodiens significantly preferred tuna over other baits. However, allant species had a preference for wet baits (25% sugar water, 25% honey, tuna & agar) as opposed to dry ones (fish meal, sorghum grit, peanut butter & dog food).This research concludes that low toxicity baits show potential in ant pestmanagement and can offer producers with a more practical, economical andenvironmentally friendly method of ant control which is compatible with vineyard IPMprogrammes.

[发布机构] Stellenbosch University