Leaf Galls & Cicadas

Steve Allgeier
Carroll County Master Gardener

"What wrong with my leaves" has been a recent and frequently asked question this month. Carroll residents have been wandering into my office with a variety of leaves that have strange looking growths and abnormal swelling on the leaves and stems of leaves.

These growths are commonly called "galls" and are typically produced by mites and tiny wasps. This abnormal swelling of plant tissue is caused when the insect or mite is laying their eggs. Basically the insect is trying to create protective plant tissue to shelter her eggs and young by injecting the plant with a growth hormone while laying her eggs in the stem or leaf, thus producing a gall.

There are also galls caused by fungi and bacteria, but insects typically cause the majority found on Carroll County trees. Once a gall appears on a leaf there is no way of controlling it and the "damage" to the leaf. This damage is mostly cosmetic anyway and typically does little or no harm to the tree. Galls are difficult and challenging to prevent, since this requires predicting when and if the insect is active, and what product to use to prevent this activity. That is why we recommend no control of galls.

An interesting experiment, if you are curious as to what insect formed the gall (assuming the gall is due to insects), is to remove some of the gall tissue and place it in a sealed plastic bag. Store the bag near the tree, but in the shade and check it daily to see if anything has hatched out. Once it hatches, then it is relatively easy to identify and evaluate if a treatment measure is needed for the following year. The identification can be done at your Carroll County Extension Office in the Ag center. Normally, galls cause little harm to their host, so no control is typically warranted.

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What's the buzz about Cicadas?

After being bombarded by TV, radio and the press about a massive cicada onslaught, many Carroll residents are beginning to wonder where are the Cicadas? Well, if you live in Eldersburg area, parts of Mt Airy and the Hampstead / Manchester area then you will see and hear the little critters. However, for much of the central portion of Carroll County, including Westminster, New Windsor and Taneytown there just aren't any or very few of these critters. Cicadas are scarce in these portions of the county because of the lack of old established tree inventories. Much of the County has been in agriculture for so long that the populations of these screaming red-eyed bugs have been pretty much decimated. For more information on Cicadas, please contact the Carroll County Cooperative Extension office at 410 386 2760 or hortman@umd.edu to request HG 43 - Periodical Cicadas.

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