by Karen Weiland, Advanced Master Gardener
Spider Mites are 8 legged pests that can seriously threaten the health of plants. They feed on plant leaves by piercing the tissue and sucking out the green liquid inside. Spider mites are not fussy about what they feed on as they like both indoor and outdoor plants.
There are many different kinds of spider mites and they will feed on trees such as oak and maple, vegetables and fruits such as melons, strawberries and tomatoes and landscape plants such as bushes and bedding plants. If the infestation gets heavy, the branches can become covered in an almost invisible web. Look for feeding marks that show up as light dots on leaves. As the feeding continues, leaves may turn yellow, dry up and fall off the plant.
There are warm season and cool season mite species. Warm season mites thrive during the summer when the daily high/low is 95 to 75 degrees F. They can become quite numerous when exposed to the south and are in a sheltered area. Cool season mites wreak their havoc during the spring and fall when daytime temperatures are below 75 degrees F.
To detect spider mites, place a white sheet of paper below a branch and hit the branch sharply. If mites are present, they can be seen as small specks crawling about on the paper. You will also get grit from the branch so watch for the crawling action of the mites. These little pests are very small, only about 1/60 of an inch long, so you may have to put the readers on to see these little guys.
A plant that is stressed is an open invitation to a spider mite. It is important to make sure plants have adequate light and are well watered to avoid being stressed.
Natural enemies abound in our landscapes that feed on spider mites and are our most important weapons when battling these little pests. Lacewing larvae, black lady beetles, minute pirate bugs and predatory mites are a few. Try to get by without using chemical insecticides if possible as they will kill the beneficial insects as well. If you do need to use an insecticide try using a least toxic material such as an insecticidal/miticidal soap and/or oils. Hosing down your plants with a steady stream of water will knock them off. Try doing this every three days for 9 days in a row. If after 12 days you are still finding large numbers of spider mites then an insecticide/miticide will need to be used.
As always, Happy Gardening!
More information about gardening and related subjects is available online at www.hort.purdue.edu/ext/garden_pubs The Purdue University cooperative Extension Service can be reached at 499-6334 in LaGrange Co., 636-2111 in Noble Co., 925-2562 in DeKalb Co. and 668-1000 in Steuben Co.
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