My large fir, pine, spruce or evergreen tree is having its needles turn rusty brown. What can I do?
Your coniferous evergreen tree is likely a spruce or fir. Both kinds of trees have extremely difficult-to-see spider mites. Over the course of two years, the interior needles are often fed on by spider mites on trees about 15 years of age and older. The presence of spider mites can be detected by looking for minute, unstructured webs spun from needle to needle (see image). In the last year of feeding, the needles turn rusty brown and drop off in late summer, fall, or early winter. The solution is to power wash the evergreen tree with water only. The pressure of the water will dislodge the spider mites causing them to fall to the ground where they are ineffective in doing any more damage to the tree. This washing down process needs to be done monthly without skipping a month from May to early October, inclusively. Spider mites usually produce 5 or 6 generations during the spring, summer, and early fall; so it is important to control each new generation as it appears. The pressure from w
