“Why is my evergreen tree turning brown?” That’s a common question we get as a professional tree service with Certified Arborists on staff. Although the answer could be one or a few explanations among many possibilities, a lot of times when an evergreen starts to lose color in mid-summer could be evidence of mite damage. There are many types of mites that affect plant health but the Spruce Spider Mite is considered one of the most destructive spider mites in our area here in Lancaster, PA.
This mite injures the needles of spruces, arborvitae, junipers, hemlocks, pines, Douglas-firs, and occasionally other conifers. One favorite target of this mite is the Dwarf Alberta spruce and its browning appearance in summer is usually a dead give-away. In a lot of cases, you can spot this damage from the street before even walking up to the landscape beds.
Spruce Spider Mite eggs overwinter on host plants and hatch early in the spring. One reasons mites are such a formidable foe is because how quickly they can mature and reproduce. In as little as 15 days, an egg can hatch and become a reproductive adult. By late spring and early summer there can be 7-10 generations on a single host plant. That’s a lot of mites feeding!
Mites harm plants by sucking plant fluid from needles. At first, the trees may exhibit a yellowing or dull color. Give it a little time, and then the color turns to brown and needles start dropping from the host plant. Spider Mites get their name from the small webs on the needles they can produce.
If you suspect you have mite damage there is an easy test to find out for sure. Do this on several parts of the plant. Get a piece of white paper and hold it under a branch suspected of having mites. Shake the branch onto the paper so that it causes mites to fall off of needles. Even though they are extremely small, you’ll be able to see these dark, oval mites against the background. You can even swipe your hand across the paper and some may squish and streak. Relax, they’re tiny and it won’t be that gross.
To get rid of mites, you need to apply a miticide. This is NOT an insecticide, it is a miticide. Don’t make that mistake. Doing so can actually kill beneficial insects that feed on mites. Since many mites are cool season hatches, they need to be treated throughout the season. Spraying should be done with equipment that has enough pressure to penetrate all parts of the plants. Horticultural oil should be applied as a dormant treatment at the beginning or end (or both) of the season to smother overwintering eggs to reduce populations.
Mites often develop resistance to miticides, so alternating miticide products throughout the year from spring until fall is advisable. Another management tool is spraying smaller plants with water. A strong stream of a garden hose can actually dislodge mites from branches and wash them completely off of the host plant. This works well for the small Alberta Spruces that often decorate porch planting pots. It has also been seen that mite populations may increase following the use of certain insecticides. Be sure to find a tree service with Certified Arborists that understand these challenges and can create a tree and shrub care program that is best for the plants in your landscape.
If you suspect mite damage on your plants and are looking for a mite control option don’t hesitate to contact us.