16November 17, 2016
If you remember back to the early spring, there was a little green caterpillar that was eating the leaves of many trees and shrubs. The caterpillar is known as the winter moth caterpillar. The caterpillar gets its name from the fact that the adult moths emerge in late November into early December. The male moths will fly around looking for female moths. As the females emerge, they climb up onto trees and shrubs on which the caterpillars will feast. The males find the females, they mate and the females lay clusters of eggs on the bark of the trees and shrubs. The moths soon die, but the eggs will survive the winter and hatch out in the spring when air temperatures average around 55 degrees. After the eggs are laid, the eggs are green in color and soon turn a reddish orange. In the spring, the eggs turn bright blue and eventually turn a blue- black before the eggs hatch.
People often ask me what they can do to prevent the moths from laying eggs. There is some thought that you can apply bands of sticky substances around the trunk of the tree to catch the female moths. The commonly used product for these sticky bands is called Tanglefoot. We do carry this in the store. It is very important for you to know that you never apply Tanglefoot or any other sticky substance directly to the bark of the tree. Generally speaking, you would put a band of foil or tree wrap around the trunk and then apply the Tanglefoot to that band.
There is also the thought that you can spray the trunk of the tree with horticultural oil after the eggs have been laid. The oil coats the eggs and causes the eggs to die. Horticultural oil can be applied in the fall and/or in the early spring. The spring application should be done well before the leaves have opened on the trees. Horticultural oil works best when it is applied at temperatures above 40 degrees. This allows the oil to flow into all the nook and crannies of the bark. Female moth will lay eggs in these protected areas so it is important for you to thoroughly get the oil into those areas. An application of horticultural oil may not be 100% effective, but it can help in controlling the caterpillar population.
Come the spring, there are some very effective organic sprays that can be applied to buds of blueberries and fruit trees. These sprays need to be applied early because the caterpillars will eat the buds before the flowers open. If the flower buds are destroyed, you won’t get any fruit that spring.
You can apply the same spray to the newly opened leaves to control the caterpillars. To be effective, the sprays need to be applied to the leaves while the caterpillars are small. If you wait until the caterpillars are large, you won’t get any effective control.
There is a new systemic spray that will be available this spring that is very effective against both the winter moth caterpillars and the gypsy moth caterpillars.
If you would like more information on the winter moth and their caterpillars you can go to the University of Massachusetts web site ag.umass.edu. It is a very informative web site and it has given me a lot of insight on control methods for this pest.
Well, that’s all for this week. I’ll talk to you again next week.