EMERALD ASH BORERS.
The Emerald Ash Borer continues to be a threat to all ash trees. Trees that have been treated with emamectin (TREE-Age) in proper dosage do very well. Trees treated by soil treatments, bark treatments and trunk injections with chemicals other than emamectin may not fare as well.
This year will be our 14th year treating and saving ash trees from this deadly pest. Since 2008 those treatments have been done with emamectin. The success rate with this chemical is 99% or more. To our knowledge, we have never lost an ash tree that was in decent condition when treated. (Decent condition defined as having at least 70% of normal leaf canopy.) For that reason, we guarantee the treatment of ash trees with over 70% leaf cover. We have also treated many trees in worse condition and most of them survive as well. A few trees that were treated with less than 20% of normal leaf cover have recovered to be normal in appearance and leaf cover.
Since virtually all of Michigan is considered to still be an ash borer “hotspot” with high populations of the borer, the recommendation for treatment is still injection with emamectin every two years (also, that is the product label recommendation.) The hope is that when most native and untreated ash trees have died, the population of ash borers will be lower and longer treatment intervals will be adequate.
Magnolia scale has been severe for the past two years, so we have a full page devoted to this insect and its management.
The Two-Lined Chestnut Borer (2LCB) attacks and kills oak trees and some other hardwoods, including chestnut trees (the original host.) We have treated a number of infested oaks over the past few years and have had good control of the borers using the same regimen as for ash borers. If you see thinning or branch dieback in the top of your oak tree, it should be evaluated for the possibility of this serious insect pest. We have seen this pest in Midland, Saginaw, Bay City, Beaverton, and in the Traverse City area. It is considered to be the number one insect killer of oak trees. It primarily attacks oaks that are stressed from drought or root injury, but can attack healthy oaks that are near severely infested oaks.
The Bronze Birch Borer attacks, disfigures and kills smooth barked white birch trees, especially European and Asian ornamental varieties of birch. This borer is in the same family of borers as the ash borer and 2LCB and works the same way, burrowing under the bark, causing dieback from the top down. Native birches have evolved with this pest, so they are usually resistant unless they are stressed by drought or root injury. Older birches that are infested can be treated with emamectin trunk injection to kill the borers within and then maintained by annual soil applied imidacloprid or emamectin injection every two to three years.
This disease is severe in some parts of the state and is a serious killer of oak trees. See full page in this website for a discussion of this disease. It can be prevented and in some cases treated.
SOFT SCALE INSECTS (the ones that drip sap on driveways, roofs, patios, cars, etc.)
The soft scale insects are making a comeback. The soft scales include cottony maple scale, lecanium scale, magnolia scale, Fletcher scale, spruce bud scale, others. They were severe a few years ago and now we are seeing increasing populations in 2014 and 2015 and we expect even worse in 2016. These insects do not usually kill trees (unless the homeowner gets frustrated with the sap drippage and cuts the tree down.)
If you have trees that are dripping sap, especially maples, oaks, locusts, lindens, magnolias, ashes, we can treat them with trunk injected and/or soil applied insecticides to control the scales. Sprays are not usually effective and may actually make the problem worse. See the full page discussing scale treatment.
BASSWOOD LEAF MINER (on basswoods and linden trees)
This mainly nuisance pest is a beetle that skeletonizes leaves as an adult and mines the leaves as a larva. It has multiple generations per year, resulting in severely damaged leaves littering the lawn in mid-summer.
We have had some success injecting these trees with emamectin, giving at least a two year reduction in the leaf damage caused by this insect.