Spider Mite Outbreaks
Originally posted on ecoIPM.org
Things are heating up and the twospotted spider mite, Tetranychus urticae, thrives in hot dry weather. I have found many spider mites in the landscape on roses and many other plants. My butterfly bushes (Buddleja), which are particularly susceptible, are losing leaves (which have turned yellow anyway) due to mite damage. It is important to scout for twospotted spider mites now because they reproduce most rapidly in hot dry weather. Under these conditions they can mature from egg to reproducing adult in 5 days! Nursery crops are especially susceptible because they may be exposed to more sun than landscape plants and tolerance for damage is lower.
My plants had predatory minute pirate bug (Orius) nymphs mixed in with the spider mites but so far they were not keeping up with the rapid spider mite population growth. I rarely see spider mite webbing on plants especially outdoor plants.
Twospotted spider mites feed on over 100 plant species sucking the fluid out of leaf cells. This ‘stippling’ damage can rapidly cause entire plants to take on a bronzed appearance. Look on the underside of leaves on susceptible hosts or beat foliage on a white piece of paper to scout for spider mites. If you notice mites or damage a range of control options are available the best of which are several new miticides that provide efficacy against many mite life stages. Pyrethroids can make mite populations worse by killing natural enemies. Imidacloprid can also cause spider mite outbreaks. For more information and product suggestions visit a comprehensive guide from University of Florida.