Comparison of biological control of the raspberry leaf and bud mite on two raspberry varieties


Abstract: The raspberry leaf and bud mite, Phyllocoptes gracilis, has become increasingly important as a vector of Raspberry Leaf Blotch Virus with the growing popularity of the raspberry variety Glen Ample. Simultaneously, expanding use of polythene tunnels for raspberry cultivation has increased the importance of spider mite infestations. Biological control of P. gracilis is desirable but has rarely been tested. Consequently a field experiment was arranged under tunnel and open field conditions to establish if predatory mites could limit the extensive damage caused by eriophyid and spider mites. In addition to Glen Ample, a local raspberry variety, Maurin Makea, was included in the experiment. Predatory mites were released several times during the season and leaf samples were collected for mite counts at two or three week intervals. The releases of Neoseiulus cucumeris reduced the numbers of P. gracilis on cv. Glen Ample by about 50% both in the tunnel and open field. On cv. Maurin Makea the effect was the same in the tunnel whereas in the open field the population remained low also on the untreated plants. The effect of a naturally occurring phytoseiid species Phytoseius macropilis and cecidomyiid predatory larvae was significant, especially on untreated Glen Ample grown in a tunnel.

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