BIOLOGICAL CONTROL OF TETRANYCHUS URTICAE KOCH IN STRAWBERRIES OPEN FIELDS AND GREENHOUSES BY RELEASING PHYTOSEIULUS MACROPILIS (B A N KS) (ACARI : TETRANYCHIDAE & PHYTOSEIIDAE)

Biological control of Telranychus urticae Koch (Acari : Tetranychi­dee) on strawberries was investigated in open fields in three Egyptian Governorates by releasing the predatory mite. Phytoseiulus macropilis (Banks) (Acari : Phytoseiidae), at a rate of about 5 individuals/ bit. (i.e. 100000 predators/feddan). More experiments were carried out in Ismai­lia Governorate for releasing the predator to control the T. unite° popu­lation in plastic greenhouses and also release the predator in an open field with the rate of about 3 individuals/bit (i.e. 60000 individuals/ feddan). The percent reduction of T. urticae population reached more than 90 % after six weeks from release at Ismailia Governorate, while reached this level early in the fifth week at Qualubia and Sharkia Govern­orates. This was probably due to the low pest population at the time of release. The T. urticae reduction in the greenhouses reached more than 90 % in the sixth or seventh week of release. However, the pest and predator densities showed a tendency to increase in the greenhouses than those in open fields which could be attributed to the warmer tern­perature inside the greenhouse. The minimal release of the predator could maintain the pest population under relatively low level, yet the two-spotted spider mite outbreaks areas (hot spots) were occasionally observed in the released areas where additional predator release should be done. Results indicated the possibility of controlling the two-spotted spider mite. T. urticae on strawberries in open fields and plastic green­houses by releasing the predatory mite. P. mac.ropilis with the rate of about 5 predators/bit.