THE POSSIBILITIES FOR CONTROL OF 2-SPOTTED SPIDER-MITE TETRANYCHUS-URTICAE ON FIELD-GROWN STRAWBERRIES IN THE UK BY PREDATORY MITES

The potential of two species of predatory phytoseiid mites to control the two-spotted spider mite, Tetranychus urticae, on unprotected field-grown strawberries in the UK was investigated. Typhlodromus pyri, a native species, was able to control T. urticae in some circumstances, but was less effective under hot, dry conditions. Natural colonization by this species is likely to be too slow in plantations of 1 - 2 years life. Attempts to introduce this predator to strawberry fields on cut apple shoots were unsuccessful. The exotic predator Phytoseiulus persimilis, which is available from commercial sources, gave very good control of T. urticae when released onto strawberry plants in June. A release earlier in the year was less successful, so to prevent early build-up of mites and possible plant damage it may sometimes be necessary to reduce spider mite numbers early in the year with an acaricide, before a later release of P. persimilis. The success of this integrated control strategy was demonstrated.