ERIOPHYID MITES ( Eriophyidae )
Eriophyid mites are tiny, carrot-shaped, translucent-pinkish creatures which feed in the fascicle between the flat surfaces of two needles. Eriophyid mites attack mainly two and three-needle pines. Although the insects are actively feeding by early June, we have often found it difficult to find the insects until weeks later when the damage becomes evident.
The most characteristic damage caused by these mites consists of bending, twisting or stunting of at least one needle per fascicle in several fascicles per branch. This is most noticeable at the tips of shoots where affected needles may be as little as 1/4 the length of unaffected ones. This is not definitive proof, but it is a pretty good sign of their activity.
Another type of damage we often see is mid-season defoliation. When eriophyid mite populations are really high, their feeding drains enough energy from the needles to cause them to die and be dropped. One or both needles in the infested fasicle may be lost, providing a general thinning to the crown.
To find these eriophyid mites, look for fascicles where one needle appears to be stunted. Carefully remove the two needles from the fascicle and examine the flat surfaces near the base for the mites. Where the population is very large, the eriophyid mites look very much like pale pink dust. They are very tiny, and to see them you need at least a 10x handlens. Even then, the insects are barely resolvable.
We do not recommend general preventative sprays, as most growers do not need them. Once injury is caused however, treatment will not cause stunted needles to resume growth; that damage is done. If you find this pest to be a problem this season, and the mites are still present, treat with a registered pesticide to decrease the population and to prevent needle loss from current feeding activity. Also, be prepared to treat to prevent injury next season. There are no established threshholds. Early control of the mites may help to prevent feeding injury.
Return to Pest Menu