Biological control of strawberry tarsonemid mite Phytonemus pallidus and two-spotted spider mite Tetranychus urticae on strawberry in the UK using species of Neoseiulus (Amblyseius) (Acari : Phytoseiidae)

Two species of Neoseiulus, N. californicus and N. cucumeris, showed potenti al for biocontrol of phytophagous mites on strawberry. N. californicus cont rolled Tetranychus urticae on potted strawberry plants in a gauze-sided gla sshouse at temperatures comparableto early summer in the UK (8-20 degreesC) . Both species of phytoseiid reducednumbers of the tarsonemid Phytonemus pa llidus on potted strawberry plants under glasshouse conditions (15-23 degre esC). In several experiments reductions in the range of 71-81% in numbers o f tarsonemid active stages and eggs, compared to non-release plants, were o btained. The importance of establishing a suitable predator: prey ratio at an earlystage was demonstrated in an experiment where an initial ratio of 1 N. cucumeris: 10 P. pallidus gave a greater degree of controlthan 1:20 or 1:40.