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I have spider mites on my IIiamna rivularis. It looks like I also have spider mites on my Mirabilis jalapa. I don't remember of having any problems with growing Mirabilis jalapa before. They have always been an easy plant for me to raise. I have read the article on spider mites and I am wondering if I should just let them go or buy an insecticide like Bayer Advanced 3 in 1 Insect, Disease and Mite control. The spider mites are taking over my yard.

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Spider mites are most active during the hot dry months of the summer - if there is large infestation you may actually see "webs" thereby the name of spider mites is that they produce silk like webs.  The actual spider mites are too small to see without a magnifying glass or under a microscope. The result of spider mites on your plants is a speckled mottled appearance and yellowing.  A way to control spider mites it to hose the underside of the leaves to knock off the mites.  Usually a chemical control is not necessary, because these general broad spectrum insecticides have the potential of harming beneficial insects in your garden.  Also there are predatory mites that feed on spider mites that would be knocked out and often times, the target pest becomes a bigger problem because the natural predators are killed off by the chemical control.  Another method would be use an insecticidal soap or summer horticulture oil sparingly (oil and soap in hot months may burn leaves) to control the mites. Horticultural oils can be used on perennial and woody ornamentals during the summer at the 1 to 2 percent rate. Higher rates of horticultural oil (3 to 4 percent) or dormant oil are useful for killing mite eggs and dormant adults in the fall and spring. The insecticidal soaps are useful in the warm season. Remember that mites are very tiny and soaps and oils work by contact only. Therefore, thorough coverage of the plant is necessary for good control.

Posted on 30 Jul 2008

Maggie Shao
Horticulture Agent, Salt Lake County

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