Landscape Update

COMMON PESTS IN THE TRI-CITY AREA- The following paragraphs discuss several of the insects pests commonly identified in the mid-Michigan landscape.

EMERALD ASH BORERS are currently present in Saginaw County, and the county is now a quarantined county. Midland county has had several outbreak areas, but is not yet a quarantined county (3/12/08). Bay City and Mt. Pleasant have experienced outbreaks also, with significant tree damage and loss. If homeowners want to save ash trees, we have proven methods to prevent serious borer infestation. TRUNK INJECTION of larger trees and GROUND INJECTION or DRENCH of smaller trees have been shown to be effective if applied properly and in adequate dosage. Properly timed insecticide sprays can also be used. We have a detailed discussion of this pest and effective control measures on the Emerald Ash Borer page.

BRONZE BIRCH BORERS (close relatives of the emerald ash borer) kill or disfigure many landscape birches in this area. These borers can also be prevented by TRUNK INJECTIONS or ROOT INJECTIONS with an insecticide which kills the borers before they can do damage. The injections also control BIRCH LEAF MINERS that cause brown spots on the leaves of many birches (a cosmetic problem). Sprays can also be used to control the adult phase of these borers, but it is difficult to get excellent control with this method.

COTTONY MAPLE SCALE (CMS) and LECANIUM SCALES are very common in this area, possibly due to the wide-scale spraying for mosquitoes, which kills some of the natural enemies of this pest. These "soft" scales are a nuisance, causing much honey-dew falling onto surfaces below and sooty mold growing in the honey-dew. We have developed very effective ways of dealing with these scales. See page on Scale Treatment.

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.