Sustainable biocontrol of greenhouse vegeteable pests in Lebanon: Mass production of Amblyseius swirskii and its efficacy against whiteflies and thrips.

Abstract

Pest attacks contribute to significant yield losses in vegetable production. Most farmers rely mainly on toxic synthetic pesticides to control these pests. However, due to the repeated use of pesticides and their misuse, pests, mainly whiteflies and thrips, have developed resistance to several pesticides; often leading to failure in pest control and/or a high number of pesticide applications resulting in great economic costs to farmers and negative impact on human and environmental health. Therefore, biological control can be an essential component in controlling these pests within an IPM strategy. Amblyseius swirskii (Anthias-Henriot), a beneficial predatory mite is used as biological control agent against a wide range of arthropod pests, including thrips, whiteflies, eriophyid mites, broad mites and spider mites. Since, at present, the Lebanese government doesn’t allow farmers to import such arthropod natural enemies, our objective in this thesis was to search for these beneficial predatory mites in Lebanon, rear them, evaluate their efficacy in controlling the pests and hopefully at a later stage, supplying them to farmers. A local strain of A. swirskii was collected from Batroun area and was confirmed to be A. swirkii, using both morphological and molecular tools. Laboratory trials were performed to determine the best rearing media for A. swirskii and its prey, Carpoglyphus lactis (Linnaeus). Coarse autoclaved wheat bran along with 20% yeast was the best combination for rearing C. lactis, while 15 A. swirskii per gram of culture media of coarse autoclaved wheat bran along with 20% yeast with 1:50 A. swirskii to C. lactis ratio was successfully able to yield 300 A. swriskii per 1 g of culture media four weeks post inocculation. A small scale greenhouse trial on cucumber plants proved that the locally reared A. swirskii were capable of successfully controlling whitefly eggs with 90 and 97% and whitefly nymphs with 85 and 93 % efficacy, respectively at two release rates 50 and 100 A. swirskii/ m2, five weeks post introduction. A large scale greenhouse experiment for evaluation of the efficacy of the local A. swirskii for the management whiteflies and thrips was carried in two commercial size greenhouses in Kfarmashoun.One greenhouse served as a control, where the farmer followed his normal plant protection measures while in the second one, IPM practices were implemetned.The populations of insects on cucumber and pepper leaves were monitored and recorded on weekly basis. With no insecticide sprays during the entire growing season, A. swirskii successfully maintained the thrips and whiteflies populations below their economic threshold level (ETL) with an efficacy similar to 14 insecticidal/acaricidal sprays in the control greenhouse. The maximum population of adult thrips, larvae thrips, whitefly adults and whitefly nymphs recorded were 1.54, 6.36, 1.65 and 1.45, respectively per cucmber leaf and 1.14, 0.4, 0.63 and 0.33, respectively per pepper leaf in the IPM greenhouse. These trials showed that the local A. swirskii could be mass reared in laboratories under controlled environmental conditions, in order to be provided to Lebanese farmers to help them in reducing damage by the two major insect pests in cucumber and pepper greenhouses, with considerable reduction in insectiside sprays leading to minimizing risks to human health and the environment.