Posted by Brent Wilson on 10/1/2017 to FAQ (Frequently Asked Questions)
So you have a juniper or other type of plant or tree and have noticed the foliage rapidly changing from green to light green, yellow or white. There could be several causes for the foliage color change including soil pH, excessive heat or cold, too much sun or shade, or a soil moisture or drainage problem...but it could also be spider mites.
Spider mites are tiny little critters that are most common on junipers but will also visit oaks, roses, azaleas, marigolds, tomatoes, green beans, watermelons and apples. They will visit many other types plant types when populations are high.
The first sign of spider mite infestation is a loss of leaf color in the center of the leaf, usually more pronounced toward the stem end of the leaf. Leaves with spider mites change from green to a yellow or off-white color rather quickly. When mites first start feeding, discoloration has a speckled appearance. Soon, the discoloration becomes more solid as the mite population increases.
Spider mites are so small that when on a plant they are usually not visible to the naked human eye.
Identifying Spider Mites
Because spider mites are so small and hard to see, you'll most likely need to test for their presence. To do so simply shake some foliage on the plant over a solid white sheet of paper. If you see tiny specks moving around on the paper you know it's spider mites.
Controlling Spider Mites
If spider mites are present, the first thing I advise is trying a natural method of control, which can be effective when populations are light. Pressure spray all the foliage and stems of the plant with a stream of water from the garden hose. Repeat this process several times during the same day and for several days thereafter for this type of control to be effective.
If after several days you test for spider mites again and they are still present it will be necessary to use chemical control. Though Malathion can work to kill spider mites, I usually suggest using less harsh products such as neem oil or insecticidal soap, following the instructions on the product label for use. These substances will cling to and kill spider mites rather effectively.
Note of Caution: To avoid harm to pollinating and other beneficial insects, spray insecticides in the early morning or late evening hours, when these beneficial insects are not active. Also, note that any chemical sprayed needs to touch the spider mites to kill them. Therefore, make sure you spray the undersides of foliage, where spider mites hang out, as well as the top sides.
Hope this information was helpful. If you need more details or have any questions don't hesitate to contact us.
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