Optimization of Encarsia sp(Hymenoptera: Aphelinidae) rearing to control Bemisia tabaci (Hemiptera: Aleyrodidae)

Abstract

Whiteflies are sucking insects that cause direct and indirect losses in various commercial crops throughout the world (Brown et al., 1995). Leaf yellowing and drop is the main example of direct loss, in that it reduces growth and yield and severe attacks may even lead a plant to die. Indirect losses are related to virus transmission and conditions for the fumagina development which jeopardizes the photosynthesis and plant respiration processes. The fungus develops on the honeydew secreted by the insects while feeding and may, in critical infestations, kill a plant, especially the Biotype B ones. The whitefly is controlled especially by insecticides; a constant use of this method, however, may cause problems such as resistant populations, residues in foods and environment, further to intoxicating the handler. Thus, other handling forms such as the destruction of other crop residues that can serve as store and elimination of weeds as likely shelters to the pest and to the virus (cultural methods) can be efficient provided that it is adopted by a group of producers within the same region. Another alternative is using natural enemies, and the parasitoid Encarsia formosa (Hymenoptera: Aphelinidae) is probably the natural enemy mostly used worldwide to control whiteflies of the genera Trialeurodes and Bemisia in greenhouses. Thus, the project intends to develop mass rearing of the parasitoid Encarsia sp to control the B. tabaci biotype B whitefly in greenhouse. The steps to be developed will include: 1) Optimization of mass rearing of Encarsia sp instars B. tabaci biotype B based on studies on (i) the selection of the host plant for whitefly rearing; (ii) optimal number of whiteflies per rearing cage; (iii) the biology of Encarsia sp in different instars of B. tabaci biotype B; (iv) the study of thermal requirements and temperature threshold (base temperature), as well as (v) the effect of variable temperatures and relative humidity in the development of the parasitoid; and 2) The parasitism efficiency in the pest control based on studies of (vi) parasitoid dispersal; (vii) the optimal number of parasitoids to be released (parasitism capacity); (viii) comparison of different release techniques; (ix) biological control efficiency of whiteflies compared to the conventional control (chemical) and (x) Encarsia sp selectivity to the main pesticides used in greenhouse.