Cicada killer wasps burrow into ground, don't attack people

BACKYARD Q&A

August 01, 2004|By Jon Traunfeld and Ellen Nibali | Jon Traunfeld and Ellen Nibali,SPECIAL TO THE SUN

Some large insects that look like wasps on steroids are burrowing into a few places in my lawn. They leave a mound of dirt. They have not attacked my dogs or us, but I have about 10 mounds in my yard.

It's a cicada killer wasp. Despite their appearance and name, cicada killer wasps usually won't bother people even when provoked. They are considered beneficial because they reduce cicada populations - annual cicadas, not the 17-year species. Females are rarely seen because they are either in the burrows or out hunting cicadas. They must be large to take out a cicada in midflight. (Witnessing this is as dramatic as a scene out of Wild Kingdom.) Males cannot sting, but perch near burrow entrances and chase away intruders. Their life cycle is only a period of weeks.

Because they are short-lived and highly beneficial, and control is difficult, it is best to leave them alone.

Cicada killer wasps, as well as ground-nesting bees, prefer to dig burrows in areas where there is not good coverage on the soil. This fall, reseed your lawn and follow our recommendations to promote a dense turf less inviting to these insects. You can request lawn-care fact sheets by phone or view them online (see contact information below).

I'm having a problem getting the pH of my soil down to 6.0. After applying sulfur in the soil three times so far this season, the pH is still above 7.0.

Sulfur isn't lowering your pH because sulfur is an inert element and has no effect on the soil by itself. In order for sulfur to change the pH, it must be chemically altered by soil microorganisms. These microorganisms cause the release of hydrogen ions, which then lowers soil pH. The catch is that the microorganisms are not active when the pH is above 6.0. Sounds like a vicious circle, but there is a solution.

When you need to lower a pH that is above 6.0, the first step is to add iron sulfate. Iron sulfate can lower the pH to below 6.0. Then the microorganisms kick in, and you can use simple sulfur to drop the pH the rest of the way to where you want it. A rule of thumb is to add 10-15 pounds of iron sulfate or 6-10 pounds of sulfur per 1,000 square feet for each 1/2 pH unit drop you desire.

My pepper and tomato plants are getting twisted and distorted, both leaves and stems. Even the fruits are starting to make freaky shapes. I don't see any fungal spots or insect chewing. I fertilize regularly according to package directions, and I mulch with free grass clippings from a local golf course.

Your description suggests herbicide damage. (A phone call revealed that the golf course turf had been treated with an herbicide containing clopyralid.) This herbicide interferes with plant growth hormones, causing leaf distortion and small leaf size. It has a long residual effect, meaning it stays active for some time in all the treated grass along with the weed material that it killed. Contaminated grass clippings should not be composted or used as mulch. The mulch should be removed and discarded. This herbicide can contaminate beans, peas, tomatoes, peppers, sunflowers, and other crops at concentrations as low as 3 parts per billion.

I found a dead creature next to an indoor plant. It looks like a lizard about one inch long, with an arrow-shaped head and a long curvy tail. Do I need to send it to you for identification?

You may have encountered a baby lizard or salamander. Both are harmless. Our Web site has color photos of both under the Plant Diagnostics feature. Please do not send it to us! We accept only samples of plants and insect pests for identification and control recommendations. However, you could send us a digital picture through our Website's "Send a Question" feature on the menu.

Checklist:

To minimize disease problems, rake up and discard diseased leaves that fall off ornamental trees.

Plant broccoli and cauliflower seeds directly in loose, fertile garden soil for a fall crop. Cover seedlings with a floating row cover to prevent pest and wildlife feeding.

Sharpen your mower blade so it can cleanly cut, rather than tear, your lawn.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at the University of Maryland Cooperative Extension's Home and Garden Information Center. The center offers Maryland residents free gardening information and answers to plant and pest questions. Call the center's "hotline" at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail questions to www.hgic.umd.edu. (You can also download or order publications and diagnose plant problems online).

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