Scales are not just on lizards but also on trees!

The one thing exciting about my job is that every day is very different, and I never know what question will be asked when I answer the phone. This can both be challenging and rewarding. I have been in extension in Knox County for nearly 10 years and have seen things in the last two weeks that I have never seen before. Therefore, this week you get to learn what I learned!

I am very familiar with scale insects (not the scales on lizards!) because when I was new I visited many homes with raining trees caused by them. Some scale excrete a sticky substance, called honeydew, and if scale infestations are high enough it looks like it is raining under the tree. Typically, the scale we see in Knox County are noticeable in the late summer to early fall time frame.

So what are scales? They are a small insect that will attach to a tree by their mouth and suck fluids out of the tree. They tend to form structures that look like scales on the tree branches. The new part for me is that we are seeing some early species of scale, oyster shell scale and Japanese maple scale. These two look similar. Oyster shell scale are grayish and elongated scales that look like oysters, whereas the Japanese maple scale is typically whiter in appearance. These scale are in the crawler stage in May-June time frame, which is the only time in their life that they will be mobile. The crawlers are small and flattened and look like dust on the plants. The crawler stage is also the best time to manage this pest, if needed. There are insecticides available; however, they should only be used if there is a major infestation and/or young trees as these insects typically cause little harm to trees, especially mature ones. Common damage we see is small branches or branch tips will die.

Scale insects have many natural enemies, such as lady beetles and microscopic wasps, that feed on them. Many of the insecticides will kill the beneficial insects, as well as the nuisance insects. Trees invaded by scale are typically under stress, so keeping trees watered during dry times can help reduce some stress. If there are some branches that are heavily infested you can prune them out of the tree and dispose of the infected branches.

So, there you have it. I learned about identification of early season scale insects, and you learned that lizards aren’t the only thing with scales. You can learn more about the common scale insects in Indiana by visiting or contact the Purdue Extension-Knox County office by calling 812-882-3509 or by emailing

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