Integrated pest management of greenhouse pests by locally collected entomopathogenic fungi and predatory mites

Abstract

An effective biological control based integrated pest management system has been developed for greenhouse Lebanese farmers, as an alternative to the use of pesticides. Pesticides have long been criticized for their harmful effects to the environment, plants, and human health and their misuse lead to a reduced efficacy in the control of pests due to buildup of pest resistance against many pesticides belonging to different chemical families. For that reason, mass production of a locally collected entomopathogenic fungus Beauveria pseudobassiana and the predatory mite Phytoseiulus persimilis were conducted and followed by laboratory and field studies to assess their efficacy in the control of arthropod pests. Mass production trials of B. pseudobassiana on 4 grain substrates at two grain: water ratios, showed that the highest yield was 3x109 conidia g-1 harvested from burghul at 1:1 grain: water ratio. Laboratory tests then aiming at improving the germination percent of conidia showed that addition of mannitol at 10 g L-1 or 1% corn oil to the conidial suspension significantly improved conidia germination. The local fungal isolate was then tested for its efficacy in the control of Myzus persicae and Bemisia tabaci on cucumbers and Tuta absoluta on tomato, under greenhouse conditions. The treatments were 108 conidia mL-1of Beauveria + 1% corn oil + 0.01% Tween-20 and 1% corn oil + 0.01% Tween-20. The fungus was able to reduce the M. persicae colonies by 83%, and the B. tabaci population by 88% compared to the control. On tomatoes, the sprays of Beauveria were effective in controlling the egg stage of T. absoluta, causing 80% corrected mortality at 20℃ and 70% RH, and 100% mortality at 14℃ and 75% RH. In parallel, mass production system of P. persimilis was established by examining three different ratios of spider mites: Phytoseiulus. The 40:1 ratio was the fastest in producing high numbers of predatory mites. Two small scale greenhouse experiments were conducted to determine the efficacy of Phytoseiulus against Tetranychus urticae and its compatibility with Beauveria within an integrated pest management program on cucumbers. The results demonstrated that the local Phytoseiulus showed 96% efficacy against spider mites and was compatible with the fungal isolate when sprayed 108 conidia mL-1+ 1% corn oil + 0.01% Tween-20, resulting in 100% control. The local isolate of B. pseudobassiana was also highly active with 88% efficacy, without significant difference between the last three treatments. The biological agents were then evaluated in two commercial greenhouses cultivated with cucumber and pepper plants. In the control greenhouse, the farmer followed his normal plant protection practices and applied 14 sprays of pesticide mixtures but failed to prevent the outbreak of spider mites during June. While in the Integrated pest management (IPM) greenhouse, IPM practices were implemented including natural enemy releases. In the IPM greenhouses, P.persimilis was highly effective in reducing spider-mite infestations, even at elevated temperature (T. average 26 ºC and max 40) recorded in May and June. In addition, three sprays of B. pseudobassiana were able to manage the population of aphids on pepper plants. Thus under commercial greenhouse conditions, it was possible to control all cucumber and pepper arthropod pests in Kfarmashoun area without using any insecticide or acaricide by relying on IPM practices and using three local natural enemies, P. persimilis, B. pseudobassiana and Amblyseius swirskii (data presented in another study). The extra costs incurred by using natural enemies may be compensated by a higher price of the better-quality fruits suitable for export. Local production of natural enemies may reduce their cost.