ABSTRACT
Bioassays were conducted in 2001 and 2002 to estimate toxicities and dose-response relationships of 24 Bemisica tabaci Gennadius populations to pyriproxifen, acemitaprid, and diafenthiuron. LC50s ranging from 0.014 to 0.096 mgL(-1), 0.60 to 1.3 mgL(-1), and 3.5 to 6.7 mgL(-1) were observed respectively for pyriproxifen, acemitaprid, and diafenthiuron. These LC50s much lower than the field doses recommended for each compound. A fast increase in rates of mortality within a narrow range of lethal concentrations was observed for each compound. indicating that all three compounds were highly effective at killing whiteflies. In a separate experiment, pyriproxifen, acemitaprid, and diafenthiuron were tested in 2001 and 2002 to compare their effectiveness and assess their impact on parasitism in the field. In both years all three compounds significantly prevented B. tabaci populations from reaching economic injury levels in cotton and minimized adverse effects on parasitism. Our results provide for the first time baseline toxicological, field efficacy, and effect on parasitism data for pyriproxifen, acemitaprid, and diafenthiuron against B. tabaci in West Africa. These compounds should be included in a resistance management program of the cotton pest complex and their use should be restricted to prevent the building of resistance in B. tabaci populations.
Subject(s)
Hemiptera , Insecticides/toxicity , Phenylthiourea/analogs & derivatives , Plants , Agriculture , Animals , Burkina Faso , Dose-Response Relationship, Drug , Insecticides/administration & dosage , Neonicotinoids , Pest Control, Biological , Phenylthiourea/administration & dosage , Phenylthiourea/toxicity , Pyridines/administration & dosage , Pyridines/toxicityABSTRACT
Research was conducted in 14 cotton fields (3-10 ha) selected in seven localities (two fields per locality) in Burkina Faso, with the objectives of: (1) estimating Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) population abundance, (2) assessing the levels of parasitism by Encarsia spp and Eretmocerus spp (Hymenoptera: Aphelinidae) and (3) estimating the susceptibilities of the pest and of an Eretmocerus sp to the insecticides currently sprayed on cotton. Yellow sticky cards and a leaf-turning technique were used to estimate adult B. tabaci population densities. Yellow sticky cards were also used to estimate the densities of adult Eretmocerus sp and the susceptibilities of B. tabaci to insecticides. Leaf disk techniques were used to estimate B. tabaci red eye nymph populations and parasitism by Encarsia spp and Eretmoceus spp was evaluated using stereo-microscopy. A leaf cage technique was used to estimate the susceptibilities of Eretmocerus sp to insecticides. A mean of 6.5-27.4 adult B. tabaci were trapped per yellow sticky card and 5.5 to > 34.9 were counted per leaf using the leaf turning technique. There were 0.14-13 Eretmocerus sp trapped per yellow sticky card. The levels of parasitism varied between 36 and 87% by the end of the season and parasitism by Eretmocerus sp predominated in most of the fields. The susceptibilities of B. tabaci and Eretmocerus sp varied from field to field and with the insecticide tested.
