Insects
EMERALD ASH BORER
There are new developments in the EAB story all the time. A good starting place is an article from our newsletter Spring 2008 page 1.pdf. You also might want to visit this website. The website is from the Michigan State professor who first discovered EAB in the U.S. He has some interesting things to say that might differ from what you have heard. Please contact us if you have any questions.
BAGWORMS
You may be looking at your trees this winter and see what you might think are nature’s Christmas ornaments. These spindle shaped bags are actually made by an insect, the common bagworm. Despite the name, bagworms weren’t that common in the Chicagoland area until a few years ago.
Bagworms spend most of their lives in the bags they spin out of silk and foliage of their host plants. In our area they are most common on evergreens, especially Arborvitaes and Junipers, but can be on deciduous trees too. Their populations can build rapidly and they quickly defoliate their hosts. Healthy deciduous trees can usually tolerate three consecutive years of severe defoliation before they are killed but evergreens can be killed with just one severe defoliation.
Bagworms overwinter as eggs inside their bags, they hatch in early summer and the young caterpillars hang from a silk string and can move to nearby plants by “ballooning” using the wind. The damage caused by young larvae result in brown spots and holes in the foliage. As they grow the caterpillars enlarge their bags and feed on the entire leaf leaving only the veins.
Control of bagworms is very important. One of the best controls is to simply remove the bags from the trees. This can be done now since they can be easily seen on deciduous trees with no leaves. On evergreens the bits of plant material turn brown and can be easily located. It is very important to cut the silk band so that the branch will not be girdled in the future. The bags should be squashed, burned, put in a garbage disposal or sealed in a plastic bag.
The biological control, Bacillus thuringiensis, commonly referred to as Bt, can be an effective control if used on the young larvae. Chemical controls are available but they also must be used on the young larvae. In either case timing of sprays is critical. They should be done in late June to early July. If the larvae are allowed to mature (mid-August) the sprays will not be effective. Consult your plant health care provider for scheduling of treatments.
Whatever you do, don’t ignore the presence of bagworms or you might lose your evergreens in just one season.
Below is an illustration of adult bagworm and bag.
Source: The Ohio State University extension
ZIMMERMAN PINE MOTH
The larvae (caterpillar) of this moth is what causes the damage. In the spring, branches of infested trees wilt and curve downward. Wounds caused by these insects are found along the trunk at branch whorls. Branches attached to the main trunk at infested whorls or treetops can be girdled and killed.
ZPM caterpillars overwinter in cocoons under bark scales. They emerge in early April and tunnel into trees in late April at the bases of branches where they create pitch masses. They continue to feed while inside the tree and in August the adult moths emerge. The moths lay eggs which develop into larvae that feed for a short time before preparing to overwinter.
The caterpillar is the most vulnerable stage to insecticidal sprays. This means there are two times during the season when they can be applied. The first is in spring(April) and the second is summer (mid-August). The exact time is linked to the blooming of indicator plants.
Since insects can sense when trees are under stress it is important to keep your trees in good health by proper watering and fertilizer (chemical or biological) treatments when needed.
GYPSY MOTHS
For a non-chemical control you can do yourself check out this product: Bug Barrier Tree Band
Egg masses are the beginning of the gypsy moth life cycle. They are buff colored, approximately the size of a quarter. They are present from late August through April. Look for them on undersides of branches, tree trunks, stone walls, fences, house eaves, under dead bark, inside birdhouses, etc. They can also be brought to your home on cars, trailers, Christmas trees, firewood, mulch, etc. Old egg masses stay on the trees for more than one year – to tell the difference between old & new egg masses—new egg masses will be firm to the touch and old egg masses will feel soft and spongy. Only new egg masses hatch.
Tiny Larvae: 500–1000 hatch from each egg mass in April and May. Shortly after hatching, they cling to tree branches and leaves, hanging from their own silken threads. They do not build nests. They can be blown by the wind to other areas. Once on a hardwood tree, they will climb to the tree top and feed on the crown of the tree, chewing small holes in the leaves. At this stage, they are largely unnoticed due to their small size.
Adult Caterpillars will become noticeable as the larvae develop and the leaves begin to grow. They will feed on the foliage, chewing holes at first, then devouring the foliage completely. The larger caterpillars are distinguished by their charcoal grey color and by the double row of five blue dots and six red dots down their backs. In high populations, the caterpillars feed day and night and travel up and down the tree trunk looking for shelter.
Pupa of the gypsy moth appear in late June or early July when caterpillars shed their skin for the last time and become pupae. The pupa is a dark brown shell–like stage where transformation to an adult moth takes place. You will find them on trunks of trees and other nearby objects. Handpick and destroy pupae by crushing them completely.
Adult Moths emerge in late July and early August. Their only function is to mate and lay eggs. They do not feed. The female moth, which does not fly, is white with black markings on the wings and secretes a sex hormone that can lure the male gypsy moth from considerable distance. Male moths, small with dark brown wings, have been found to fly up to two miles to find a female. Soon after mating, the female starts to lay eggs and the life cycle begins all over again. The moths die after mating and egg laying.
Timing and method of treatments is vary for each stage. Treating the egg masses is done with Golden pest oil spray. Small caterpillars can be treated by sprays or direct trunk injections. Once the caterpillars become large the sprays are not affective and treatment of the pupa stage does not work. Although gypsy moths have a lot of hosts, they seem to prefer Oak trees in the Chicagoland area. This is unfortunate since Oak trees are one of the trees we value the most. Have your trees checked annually by a qualified, certified arborist. From Loudoun County Va. website