Biological Control 50 www.agrii.co.uk Spider mite Glasshouse spider mite or two spotted mite (Tetranychus urticae) is one of the most damaging pests which attack horticultural crops. A wide range of crops are affected, both protected and ﬁeld grown. Spider mites have a rapid reproduction and development which make resistance to chemicals more likely. The mites feed by sucking sap from under the surface of the leaf. This produces groups of small white speckles which are clearly seen from the upper surface of the leaf. When mite numbers become high, these spots coalesce, giving a bleached appearance to the affected tissue. This can affect both plant appearance and reduce photosynthesis which may in turn result in plant death. Spider mite also produce webs and some strains have toxic saliva which can cause serious damage when only few mites are present (toxicity is most common on tomato plants). Some of the biological agents we can supply to control Spider mite include: Phytoseiulus persimilis Phytoseiulus persimilis Feltiella acarisuga For speciﬁc advice and guidance on these and the other biological control options, contact your local Agrii agronomist.