Prepared by Frank Zalom, Emily Symmes, Mark Henderson and Mark Bell, July 2009 - UC Davis
European red mites (Panonychus ulmi) are not insects, but arachnids (related to spiders). There are several spider mites similar to the European red mite (ERM), such as the twospotted spider mite and the spruce spider mite- which also attack common orchard trees. However, the ERM has a significantly different lifecycle than other spider mites; it overwinters in the egg stage on twigs and branches. Because of this, management tactics commonly used for other spider mites differ from those used for ERM. Eggs (visible with a hand lens) are reddish-range and have a long spike. Immature mites are bright red and adult females are brick red with four rows of long curved hairs arising from white spots along the topside of the oval-shaped body. Adult males are brownish and smaller than females. Adult ERM are very small (0.4 mm), have 8 legs, and lack antennae. Overwintered eggs hatch early in summer at the bases of buds or on tree bark. There may be as many as 8 generations of ERM in a single summer. Unlike the twospotted spider mite, ERM produces little or no webbing.
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