Can we boost numbers of the predatory mite Amblyseius andersoni with pollen for more robust biological control of two-spotted spider mite Tetranychus urticae on raspberry in the UK?

Abstract: Two-spotted spider mite (TSSM), Tetranychus urticae, is a serious pest of many
horticultural crops including raspberry. Biological control of TSSM is key to successful
management since there are very few acaricides available for use in the UK in both protected
and outdoor raspberry. Growers use the predatory mite Phytoseiulus persimilis, which can give very effective control of TSSM. However, P. persimilis is vulnerable to pesticides used for
control of other pests in raspberry production. The predatory mite Amblyseius andersoni is
commercially available and also occurs naturally on raspberry crops and can contribute to the
control TSSM. This predator can establish at lower temperatures earlier in the season than P.
persimilis and natural populations are regarded as being more tolerant of pesticides than P.
persimilis. Typha pollen (NutrimiteTM) is commercially available and is being used to boost
populations of other released omnivorous predatory mite species, e. g., Amblyseius swirskii, on various other protected crops. This research has evaluated the use of NutrimiteTM to boost populations of A. andersoni on a commercial raspberry crop during propagation. Results indicated a potential benefit in adding pollen for improved TSSM control. Further research investigated whether adding pollen or an additional autumn release of A. andersoni augmented numbers of overwintering predatory mites during cold storage of raspberry plants. Results showed that both TSSM and A. andersoni overwintered in cold storage. The additional autumn release did not affect numbers of overwintered A. andersoni but NutrimiteTM applications may have boosted numbers of A. andersoni eggs the following season.