March 26, 2014
As spring turns into summer, our plants develop problems with insects. It seems that every year, there are more insect pests that attack our plants. There is a way to prevent a lot of these insects from ever appearing on your plants. The way to eliminate many insect pests on your plants is to apply a dormant oil spray to your plants. This is a spray application that you should be doing soon.
In the fall or early winter, many insect lay eggs on plants. These eggs hatch out in the spring and the insects begin to feed on your plants. In some cases, the insects spend the winter hiding in all the cracks and crevices on the bark of your plants. Dormant oil is applied when the plants have not begun to put out new growth. The dormant oil is mixed with water and sprayed onto your plants. The oil covers the eggs and the eggs suffocate. Any over-wintering insects are covered with the oil and they too suffocate. As I said, the oil spray must be applied before the new growth appears on the plants. In order for the oil to flow properly and get into all those cracks and crevices, the spray needs to be applied at temperatures above 40 degrees. All things considered, the proper time to apply this spray is during late March through early to mid April. The length of time you have to apply this spray can vary from year to year based on how quickly temperatures warm up and consequently how soon your plants put out new growth. Fruit trees, rose bushes and many of your other deciduous trees benefit from an application of a dormant oil spray. The vast majority of your evergreen trees and shrubs do not need an application of a dormant oil spray. The exception to this is the treatment of hemlocks to control the wooly adelgid. This cottony looking insect has resulted in the demise of many hemlocks in this area.
For many years, there didn’t seem to be a need to spray our maples and oaks with dormant oil. In the last few years, many of you have seen a small green caterpillar that has attacked our oaks and maple trees. You will have seen them on many of your flowering trees as well. This caterpillar is from the winter moth. If you think back to November into early December, you probably saw a lot of moths flying around the outside of your home. This was the male winter moth and he was looking for the female winter moth. The females tend to gather on the trunks and lower branches of trees. After the moths mate, the females lay eggs on the trunks and branches of the trees. The moths then die and the eggs wait for warming temperatures before they hatch. The tiny caterpillars will, early on, attack the flower buds of fruit and ornamental flowering trees. They can kill the flower buds and dramatically decrease the amount of fruit produced on fruit trees. They can do major damage to the foliage of trees. In many cases, they can cause major damage to the new leaves of maples, oaks, ornamental flowering trees and even some shrubs. It has been shown that several years of this early in the season damage to leaves can lead to the death of branches or even the death of the trees. For this reason, the eggs should be controlled by an application of dormant oil to the trunk and the lower branches of your oak, maple and ornamental flowering trees. The oil spray will kill many of the eggs and thus decrease the number of caterpillars that feed on your trees. You may have to follow up with an insecticide once the leaves begin to open. However, it is a lot easier to kill the eggs now than it will be to control those caterpillars that are all over the tree. Remember that temperatures need to be above 40 degrees when you apply the oil spray and it need to be done before the flower buds swell in early spring.
Well, that’s all for this week. I’ll talk to you again next week.