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Thursday, Jul. 18th 2013

Another Mite Pest?


Yes, The Boxwood Spider Mite

boxwood spider mite fig94

When we discuss spider mite pests in landscapes and gardens the two that are often mentioned are thetwospotted spider mite (Tetranychus urticae) and the spruce spider mite (Oligonychus ununguis). However, there is another spider mite pest in Kansas called the boxwood spider mite (Eurytetranychus buxi) that feeds exclusively on boxwoods including the common, English, and European. Adults are small and tan to dark yellow brown in color with long protruding front legs that make them look like a spider. The young life stages (larvae and nymphs) are smaller than the adults. Eggs typically hatch in May,and the young spider mites feed onboth the upper and lower leaf surface. Heavily infested leaves may turn yellow to brown, and premature leaf drop may occur. There are several generations per year. Boxwood spider mite overwinters as an egg on leaf undersides.

A forceful water spray directed toward the leaf underside will quickly remove all the life stages (eggs, larvae, nymphs, and adults) and will preserve any natural enemies. Similar to other pest spider mites, the boxwood spider mite is susceptible to natural enemies including predatory mites and bugs, lacewings, and ladybird beetles. It is also possible to prune or shear off the damaged growth, and then allow the new growth to emerge, which may cover or mask any remaining leaves that exhibit feeding damage.

Applications of dormant or horticultural oils to the undersides of leaves in winter will kill the eggs. In addition, an insecticidal soap (active ingredient=potassium salts of fatty acids) or horticultural oil (petroleum or paraffinic based) will kill the larva, nymph, and adult life stages. Thorough coverage of all plant parts and multiple (repeat) applications are important in order to obtain sufficient regulation of boxwood spider mite populations. Pesticides with miticidal properties including abamectin(Avid), bifenazate (Floramite), clofentezine (Ovation), hexythiazox (Hexygon), fenbutatin oxide (hexakis), and pyrethroidbased pesticides including those with the active ingredients bifenthrin and lambda-cyhalothrin may be used to regulate populations ofthe boxwood spider mite. However, a number of these materials are harmful to natural enemies. Therefore, it is important to only apply pesticides when absolutely necessary.


Article brought to you from K-State’s Insect Newsletter




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