Red spider mites are eight-legged animals less than 1 mm long. They are usually yellow or olive with dark patches on either side of the body, becoming orange or red during the autumn. They are found on the underside of leaves, where they suck the sap, producing yellow or white speckles on the foliage surface. As mite numbers increase, these speckles increase in number; the leaf will take on a bleached appearance and then die. In bad infestations, the mites will also spin webbing from leaf to leaf. These mites can remain active all through the year, and thrive in hot dry conditions, particularly in the greenhouse.

Control

Red spider mite can be controlled biologically indoors or outside by using their natural enemy, the predatory mite Phytoseiulus persimilis. The mites may also be discouraged in the greenhouse by keeping the humidity high; this may be done by regularly spraying the underside of foliage with water and damping down the floors.

Insecticidal soap may also be used on three or four occasions at five-day intervals, and those outside may be sprayed with several applications of pirimiphos-methyl or dimethoate.