July 25, 2017

Effective method to control the Red Spider Mite

Photo Credit To By Gilles San Martin - originally posted to Flickr as Tetranychus urticae with silk threads, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=11208762

Red spider mite

If you’re growing plants in a greenhouse, frame or conservatory there’s a good chance you may get problems with red spider mite. Glasshouse red spider mite or two-spotted mite as it is also known is, to put it politely, a menace!

The tiny greenish kaki mites (less than 1mm long)  feed on the foliage of  plants in greenhouses, conservatories, frames and houses, and, during hot summers,  you may also see them on  plants outside too. You’re likely to need a magnifying glass to see them and the best place to check is on the lower leaf surface.  The infested foliage becomes flecked with numerous tiny spots  as the mites such the plant’s sap and leaves may even may become dry and dead.

So what can you do? Red spider mite hate wet feet, so misting with water regularly will help to deter them but it invariably takes more action if they have already got a hold . To say that  control is not easy would be a huge understatement.  I would always recommend binning heavily infested plants.  Many of the mites have now developed resistance to some of the most commonly used pesticides – so however much and frequently you might spray, it may well  have no effect. I’d suggest that you use my preferred option, biological control, where, crazy as it may sound, you introduce another mite.  phytoseiulusBut this mite, Phytoseiulus persimilis, is round, orange-red and is a rampant predator of the red spider mite pests and rushes around the infested plants, providing excellent control as it eats its way through the pest mites, their young and even their eggs.  If you do decide to try this option, do make sure that you know the greenhouse is not contaminated with pesticide residues (as these could prove lethal to the predatory  mites) and that the temperatures are high enough (no problem at this time of year!) The mites cannot be purchased in garden centres as, being living creatures, they need the right conditions to survive but you can order them online from my website and we send them out promptly, complete with a ‘snack’ to ensure they don’t get too hungry on their journey to you!  Once released into the greenhouse or conservatory, these  biological control mites work really well– and of course the great thing is, the predators get on and do the job for you…..whilst you sit back and relax!

About The Author

Profile photo of Pippa

With a BSc in Botany and a further degree specializing in protecting plants from pests and diseases Pippa spent 11 years working for The Royal Horticultural Society at their garden in Wisley, advising gardeners about their gardening problems. More recently Pippa has become a well-loved and respected TV and Radio broadcaster and a prolific writer, with a host of best-selling gardening books to her name. Pippa regularly gives gardening talks and lectures, worked as the horticultural consultant for the ITV murder mystery series 'Rosemary and Thyme' and in 2007 was awarded an honorary Doctorate.

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