Guiding farmers' choice for an integrated pest management program against the invasive Bactrocera dorsalis Hendel (Diptera: Tephritidae) in mango orchards in Tanzania

Abstract

Trials were conducted in the Morogoro Region, Tanzania, to evaluate the effectiveness of three Integrated Pest Management (IPM) programs against Bactrocera dorsalis over five seasons. Spot application of molasses bait was compared with broadcast sprays of insecticide dimethoate/lambda cyhalothrin (Karate 5 EC) and spot application of a spinosad bait (Success, Dow AgroSciences) plus mass trapping using methyl eugenol, as components of IPM programs for B. dorsalis. Orchard sanitation and early harvesting of fruits were standard practices in each program. The molasses bait was formulated with crude extracts of Derris elliptica, water and brewery yeast waste. The effective median dose of the bait was determined by exposing adults of B. dorsalis to a range of concentrations of crude extracts of D. elliptica in a laboratory bioassay.Each program was applied in an individual mango orchard and replicated for five seasons with populations being monitored using McPhail traps baited with torula yeast. In addition, fruits were sampled at ripening and individually placed in containers to determine the incidence and infestation rates of emerged fruit fly species. Results show that for the molasses bait 9 g of D. elliptica roots powder soaked in 5 L of neutral soap are required to kill 50% of a B. dorsalis population. The three IPM methods did not differ significantly in reducing fly incidence and infestation rates. We analyzed the three IPM methods on the basis of cost-benefit, environmental protection and health safety, in the light of purpose and market focus of the farmer. It is finally recommended that spot application of botanical bait can be used in IPM programs for fruit flies in smallholder settings. Spot application of Success bait is recommended for commercial farmers targeting organic and export market markets. Broadcast spray of Karate is recommended for commercial farmers, mostly targeting regional markets.