August 1996
Needle Sheath Mite, also called the Pine Bud Mite, is a mite that can cause problems for pines in Virginia. Although sporadic, they can be serious in some plantings. These mites primarily attack white, Scotch, Austrian, and red pines.
The observable damage varies from tree to tree and can vary within a single planting. The most common symptom is sickly yellow needles with browned tips, although some needles may have a blotched appearance. Mites feed on needle sap and cause a small white or yellow spot at the feeding site. Many mites feeding give the needle a stippled or rusted appearance. The needle sheath mite gets its name from its habit of feeding in the sheath at the base of the needle. Needles need to be pulled apart in order to see the mites. Most trees usually support a small population of such mites that causes no visible damage. Flare-ups often occur on stressed trees or after applications of broad spectrum insecticides that kill mite predators. Damage appears first on the south side of the tree and may or may not spread around to the other sides.
The needle sheath mite is a small mite in the family Eriophyidae. These mites are some of the smallest arthropod plant pests known. They are creamy white and about 1/125 of an inch (0.2 mm) in length. Their bodies gradually taper toward the end and somewhat resemble a carrot in shape. Their legs are held at the front of the body. They have piercing-sucking mouthparts and do not have wings.
These mites breed continuously and are active in cold weather, but populations tend to build up in the spring. Eggs, nymphs, and adults can be found at all times. They spend almost their entire lives between the needles. They can be moved from tree to tree by wind, birds, or by moving along touching branches.
In Virginia, the best time to treat is in March or April, although treatments anytime these mites are discovered will be effective. Unlike spider mites, needle sheath mites are controlled best with Sevin. (However, Sevin is the worst thing you can do for spider mites!) Check your broad spectrum insecticide label to see if it will kill sheath mites. Horticultural oils will give good control in late winter, but the oil will remove the "waxy bloom" from the needles and give an oily appearance. Oil should be used at the lowest rate because it may cause some burn as well. The presence of damage should be used as an indicator to treat, because trees can support low, non-damaging populations of this pest. If mites and damage are found, it is best to treat the whole stand.
The damage of this mite can mimic abiotic problems, such as air pollution injury or drought, and these need to be taken into consideration when diagnosing the problem.
(Source: Pine Bud Mite/Needle Sheath Mite Entomology Fact Sheet, by Eric R. Day, Department of Entomology, Virginia Tech. 1992. Virginia Cooperative Extension Publication 444-241. Contact your local Extension agent for the current ordering instructions for this publication.)