Green Thumbs: Scoliid wasp can help control grub population - Life

Green Thumbs: Scoliid wasp can help control grub population - Life

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Green Thumbs: Scoliid wasp can help control grub population

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Posted: Saturday, September 7, 2013 12:01 am

Question: There are numerous bees hovering around my lawn. We had them last year but this year we seem to have more. They don't sting but I am concerned by their numbers. Any recommendations on what course of action to undertake?

Answer: From the sample you submitted, it was identified as a scoliid wasp. This insect is large, more than 1/2-inch, hairy, dark in color and has distinctive yellow markings. The yellow markings are on each side of the body and appear as a band when the wasp is flying. It is also known as the blue-winged wasp because it has dark blue wings.

Even though these insects may seem intimidating they are beneficial to the environment and are very helpful in controlling grubs in your lawn, most commonly the green June beetle. They can be seen hovering over lawns anytime between June and October but are most often in the largest numbers around August. The wasps fly over the lawn making a figure eight pattern as they search for the grubs.

The female flies low to the ground, searching for a grub, and when successful, she begins to dig through the soil searching out the grub's tunnel. When located she will sting it in the throat, paralyzing it. Once paralyzed, it will never recover. An egg is then laid on the third segment of the grub and there the developing wasp larva that emerges from the egg will feed on the grub and be its only supply of food. When the larva is fully grown it spins a cocoon, pupates and emerges as a mature adult wasp the next growing season.

When not searching for grubs, the wasps search for nectar and pollen of flowers for food. In August they can be seen resting on plants during the day and at night they burrow into the soil.

Many fear they will be stung by these wasps as they hover above the soil, but there are no records of anyone having been stung. Because they pose no chance of harm, no control methods are needed. The presence of the wasp is an indicator of the presence of grubs and appropriate control measures for grubs are recommended. Applying a grub control will indirectly control the wasps as they will no longer have a host to attack and will leave the area. Leaving the wasps to do their intended job may bring the grub population below damaging levels negating the need for a chemical control of the grubs.

Mona Bawgus is a certified master gardener and consumer horticulturist with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email:

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