Pest Hatching

pest controlRecent warmer temperatures mean we’re getting close to the hatching time of insect eggs. It’s still too early to tell what the mortality rate of their eggs and larvae was due to extended periods of deep cold temperatures this winter, but it’s likely to be higher than normal for at least some species.

Common pests we run into include the winter moth, hemlock woolly adelgid, elongate hemlock scale, and spruce spider mite. Here are a few tips about each one:

Winter Moth: Once we can locate their eggs on the trunks of host plants, we can begin to visually monitor them. These orange-colored eggs turn a deeper red and then a deep shiny blue color just prior to hatching. Well-timed oil sprays mixed with a compatible insecticide can be an effective management strategy, especially if applied just prior to the eggs hatching. Once the tiny caterpillars have wriggled into the buds to feed, control measures are futile until the buds open and the caterpillars are once again exposed. At that time, the caterpillars can be easily managed with many different insecticides.

Hemlock Woolly Adelgid: It appears that this pest may have experienced heavy winter mortality. But since we can’t be sure if the eggs are alive or not, we may recommend an oil spray for specimen plants that appear to have large populations of this pest. Because the past several winters (prior to this past one) have been relatively mild, the numbers of this pest had built up to the point where host plants were being killed.

Elongate Hemlock Scale (a.k.a. FIorinia Scale): We’ve seen more of this tiny armored scale over the past several years. It’s common on hemlock, but can also be a serious pest of spruce, especially in Christmas tree plantations. They often appear on the needle undersides. We see the greatest success with oil sprays during the crawler stage, which occurs right after egg hatch when the very tiny first little ones emerge from under the protection of the adult female wax covering. Once the crawlers are settled and beginning to feed (which will occur later in the spring, we recommend a basal trunk spray application.

Spruce Spider Mite: These are often found on Spruce, Fir, Hemlock, and other hosts. The best way to look for them is by shaking branches over a white piece of paper and then inspecting with a hand lens. Make note of the number of mites present and if the numbers increase noticeably, it’s best to use an oil spray.

Ticks: Don’t forget that ticks are active as soon as temperatures get above freezing! Not all ticks carry Lyme disease or other disease pathogens, but the number that do is increasing. Try to avoid areas where ticks are prevalent, and always check your skin and clothing when you come in from an extended period of time outdoors.

Read more on the UMass Amherst Agriculture and Landscape blog.


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