46 May 19, 2010

During the last week, we have had many customers who have told us about problems with caterpillars eating the leaves of various types of trees. At this point in time, the caterpillars are small and green in color. It is not a species that I have seen before and checking photographs of various caterpillars leads me to believe that the caterpillars may be from the winter moth. If this is the case, these caterpillars can be very destructive. There are several different ways to control this or any type of caterpillar.

For many years, the insecticide called Sevin was the choice for many people when it came time to control caterpillars on all types of trees, shrubs, flowers and vegetables. Sevin comes in both a powder and a liquid form. The leaves of the plant are treated with Sevin. Once caterpillars eat the insecticide, they quickly die.

Some people look for an organic control method when it comes to eliminating caterpillars. The most widely used organic control is called Bt. It is sold under several trade names including Thurgicide and Dipel. This is a bacterium that is host specific. This means that it only kills caterpillars. Even if a bird were to come along and eat the caterpillar after the caterpillar came in contact with the Bt, the bird would not be harmed. Bt comes in both a powder and a liquid form. It is applied to the leaves of the plant. Once the caterpillars eat even a small amount of the Bt, the caterpillars stop eating and die within a few days.

If you have trees that are being attacked and it is too difficult to spray an insecticide on the leaves, there is a systemic insecticide that can be applied to the soil. This insecticide is absorbed by the roots and is then taken up to all parts of the tree. The insect control lasts a long time because the insecticide is within the tree and not subject to being washed off by rain. It takes about a week from the time of application until the systemic action is completely effective.

There is also another type of caterpillar that is attacking Mugho pines. This type of caterpillar is the larval stage of the sawfly. If you see these on your pines, you will notice that when you create movement near the caterpillars, they will all move in unison. Very strange indeed! The insecticides that I listed earlier will all be effective at controlling this caterpillar.

Hopefully we are now into our planting season. We had a frost a week ago Tuesday that killed many plants. We recorded a low temperature of 27 degrees on Tuesday morning at the garden center. The last average frost date for our area is May 10 th. If you have planted and hear a frost warning, be sure to cover the plants or bring the containers of plants into your house. Better to be safe than sorry.

Well, that’s all for this week. I’ll talk to you again next week.

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