APHIDS.  Aphids are common insects in the landscape, but rarely need any treatment.  They usually do not cause any significant harm or stress to trees.  Spray companies often will tell homeowners that they are spraying for "aphids and mites", and in fact may be using chemicals which kill those insects, but it is usually unnecessary and the spray may be killing beneficial insects that would usually keep populations of aphids and mites under control.  Aphids do excrete honeydew and can be a nuisance in that way, however, the most significant honeydew drippings are usually due to scale insects.

GYPSY MOTHS AND CANKERWORMS can cause defoliation damage to oaks, maples, ash, and some other deciduous trees. PINE SAWFLY caterpillars can cause defoliation damage to Austrian, Red, Scotch and Mugho pines. When significant populations of these pests are present, they can be controlled with biologic or chemical pesticide sprays.

ERYPHYOID MITES can cause gall formation such as MAPLE BLADDER GALLS and ASH FLOWER GALLS, which are primarily cosmetic problems. These mites can be difficult to control with sprays, but newer injectables may offer some promise in controlling them. 

SPIDER MITES can also cause discoloration of foliage and defoliation when populations are large. Selective miticides are used to control the harmful mites while preserving natural predator mites and insects.  These mites attack burning bushes, Alberta spruces, boxwoods, serviceberry, and some other landscape trees and shrubs almost every year, but a mid-July spray can usually prevent the problem.

BASSWOOD LEAF MINER BEETLES have become quite common in our area and cause damage to leaves of native basswoods and some ornamental linden trees.  They may have several generations per season, with the larval stage mining the leaves and the adult beetle phase skeletonizing leaves.  A well timed spray in May, possibly followed by a second in June can prevent most of the damage.  Injectables may offer long term control without the need for spraying.

TWIG GALLS ON OAKS.  Each year we get many calls about gall formations on oak trees. There are literally dozens of different types of galls which form on leaves, petioles (leaf stems), and twigs of oak trees. Most are caused by some type of insect. Perhaps the most persistent and most common cause for customer calls are the twig galls. Twig galls are hardened woody swellings on the twigs of oak trees, seen best when the leaves are not present. They vary in size, with the average being about the size of a golf ball.

 

TYPES. The two common types seen in Michigan are Gouty Oak Galls and Horned Oak Galls. Both are caused by a type of wasp. The wasp deposits its eggs in the twig and as the larva develops, a swelling of the woody twig tissue develops. Each of these “galls” contains several developing larvae. In the spring, the adult wasp emerges and feeds on the leaves for a time, then mates and lays eggs in twigs and the cycle begins again. The cycle may be two or three years in duration.

 

NATURAL HISTORY. The old galls never shrink away, but remain present for as long as that branch or twig remains on the tree. Sometimes the twig is killed beyond the gall, but that is uncommon. The galls seldom cause large branch dieback, even when present in large numbers. They are primarily a cosmetic problem which is much less obvious during the summer when leaves are present.

 

MANAGEMENT.   Sprays could be applied during the adult phase, but would involve spraying large heavily foliated trees with insecticides several times without good evidence that it does much to improve the problem. Trunk injection of insecticides may prevent new galls from forming, but will not rid the tree of the old ones.  We recommend deep-root fertilization of trees once every two to three years to help maintain vigor and healthy foliage. The galls are far less noticeable in the summer months, especially if the trees have healthy, thick foliage. If branches die, they should be pruned during the months of September through March, avoiding the warm months when the beetle vector of oak wilt is active.

 

TRUNK INJECTION.  Trunk injection may give control of this pest.  If a tree has soft scale infestation (lecanium scale), injection will control both the scale and the galls.  It is difficult to document and quantify the results on the galls, but it will be easy to document success with the scales.

 

 TriCity Tree Doctor  Call us at 989-454-0227

United Tree Service  Call us at 810-266-4363