Question
i have a plum tree that has some curled leaves & on under side of leaves there are lots of tubes coming out of the leaves  witch are about 1/4"long. some leaves have a lot of them on. it does not look  like eggs. it looks like its coming out of the leafs. any idea of what it is .will it harm my tree???

Answer
Hi Grant, DESCRIPTION OF THE PEST
The leaf curl plum aphid is often found inside curled leaves. It is shiny and varies considerably in color from green to brownish green or brownish yellow. This aphid overwinters in the egg stage near the base of buds. In spring it rapidly builds populations on new foliage, causing affected spurs to develop tightly curled leaves. In May, the aphids migrate from the orchard to summer host plants in the family Asteraceae.

DAMAGE
Colonies of this pest cause leaves to curl tightly. Often only one limb or a portion of a limb is infested early in the year. Large amounts of honeydew are secreted by this aphid. Tree growth and fruit sugar content can both be reduced by populations of this aphid.

MANAGEMENT
Several natural enemies are important in the control of aphids in the orchard, but aphid populations often require treatment. The best indicator of populations is orchard history. The best time to treat is during the dormant or delayed dormant period. If aphids are a chronic problem in the orchard, apply a treatment early in dormancy; otherwise, sample during dormancy to determine the need to treat as described below. Spring treatments may also be made. After harvest, a zinc sulfate application will provide zinc to the trees as well as hasten leaf fall. Without the leaves on the tree, the aphid life cycle is disrupted. Zinc sulfate (36%) applied at 10-20 lb/acre can be applied in early to mid-October to help in this process.

kathy