Compatibility of Phytoseiulus persimilis (Acari: Phytoseiidae) with Beauveria pseudobassiana (Hypocreales: Cordycipitaceae) for the development of integrated pest management programmes for greenhouse vegetable crops

Tetranychus urticae Koch (TSSM) (Acari: Tetranychidae) is a major pest of vegetables in the Mediterranean region and has been known for rapid development of resistance to several chemical pesticide groups. The predatory mite Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) has been efficiently used for the management of TSSM. Therefore, other sustainable approaches should be developed for the management of other pests along with TSSM. The entomopathogenic fungus Beauveria pseudobassiana Rehner and Humber (Hypocreales: Cordycipitaceae) was reported to control several insect pests. The present study evaluated the compatibility between two local biological agents, P. persimilis and B. pseudobassiana for their simultaneous use in integrated pest management programmes. In two mite-proof cage experiments, the bioagents applied either alone or in combination were able to provide a significant reduction in TSSM population, ranging between 77 and 100% within three weeks of application, with the combined application giving the highest level of control. In the greenhouse experiment, P. persimilis resulted in 59% reduction of TSSM numbers within three weeks of its application; while the combined treatment, P. persimilis + B. pseudobassaina, gave 92.4% reduction. In the three separate experiments, and after two consecutive sprays with B. pseudobassiana applied at weekly interval, there were no significant differences in the number of Phytoseiulus between the Phytoseiulus treatment alone and the combined Beauveria and Phytoseiulus treatment. This shows that the biocontrol agents are compatible, and the combined application provided a high TSSM mortality. Therefore, for IPM planning, the combined application allows to control TSSM and other insect pests.