Plant and Insect Diagnostic Clinic Update - August 11, 2010

The following are highlights and updates about samples and questions recently received in the Clinic:


Tiny Moth Outbreak.  The small, triangular, tan moths present in "outbreak" numbers around the state the past week are called the celery leaftier moth.  The name is misleading.  Though the caterpillars do feed on celery leaves and tie the leaves with silk webbing, the caterpillars are found on a great many other plants.  In Iowa, the caterpillars were abundant in soybean fields last month and now the moths that developed from those caterpillars in the bean fields are moving around at random, and settling into unlikely places (such as lawns and my front porch!).

The moths are harmless and no control is necessary.  In two weeks the moths will be gone. However, at that time we should be checking for the next generation of small, pale green caterpillars on soybeans, green beans, lettuce, beets, spinach, petunia, geranium, mums, snapdragon, violet, etc. The caterpillars do not feed on turfgrass, so home lawns do not need to be sprayed.

See BugGuide for more information, including close-up photos.

Milkweed bugs. I don't know what this means, but 3 people in the past week reported larger milkweed bugs feeding on a milkweed seed pods in their home landscape. The larger milkweed bug has not been common in Iowa in the past, in our experience. The BugGuide website on larger milkweed bugs says this insect is traditionally considered to be a southern and eastern USA insect. Stay tuned. Milkweed bugs have sucking mouthparts and feed on sap from the milkweed seed pods. They are not a pest unless you are trying to produce milkweed seeds.

Annual cicadas are out in force now and very noisy in the late afternoon.  Annual cicadas are discussed at the middle of the ISU Yard & Garden Column from June, 2008.   Annual cicadas are the ones that appear in mid- to late summer every year.  Just to be clear, the cicadas you have been hearing in the trees throughout the state since mid-July are NOT the periodical cicadas reported in south-central Iowa back in June.  See the photo below.  You can listen to annual cicada songs on the Sound of Nature website.  Click on the scissor-grinder cicada song and the Linne cicada song.  Cicadas are not a pest. Treatment is not warranted.

Larger milkweed bug nymphs on milkweed seed pods.Larger milkweed bug nymphs on milkweed seed pods.

Annual cicada.  Note the black eyes and green coloration of the body and wing veins.Annual cicada. Note the black eyes and green coloration of the body and wing veins.


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