No. 4 Article 4/April 21, 2006

Insect News Around Illinois

Alfalfa weevils gaining steam. Reports of alfalfa weevils are starting to increase, particularly in the southern half of Illinois. There are no reports of significant feeding yet, although the number of larvae being found in field sweeps is increasing. Just as a reminder, alfalfa weevil larvae begin feeding around the accumulation of 300 degree-days (base 48°F, starting January 1). Feeding evidence begins as pinholes, and as larvae mature, leaf skeletonization may occur. For up-to-date accumulations of degree-days near you, visit the Degree-Day Calculator. Degree-days can be calculated for accumulated degree-days or project degree-days up to two weeks.


Early instar alfalfa weevil feeding.

Aphids found in alfalfa. Kevin Black, Growmark, has received reports of and has found cowpea aphids and pea aphids in alfalfa fields in southern Illinois. Pea aphids are a concern in early spring as alfalfa is becoming established and around the time of the first cutting of hay. Pea aphids prefer cool, dry weather. Populations of these aphids rarely reach levels that cause economic injury. Both predators and fungal pathogens will keep populations low, especially as temperatures increase. Kevin reports that while he found significant numbers of pea aphids in one alfalfa field, a nearby field had fungal pathogens actively working on the aphids. Given the recent warm weather and rain, it is uncertain how the pea aphid populations will respond.


Pea aphid on alfalfa (photo courtesy of Matt Montgomery).

True armyworm larvae found. A few true armyworm larvae have been found in some wheat fields. Ron Hines, Dixon Springs Agricultural Center, reported a couple of larvae in wheat and tall fescue fields this week, though his findings were "few and far between." No injury has been seen in fields from other reports. Given the number of moths caught in traps in Kentucky and southern Illinois, growers should continue to monitor fields for true armyworm injury.


True armyworm larvae (photo courtesy of Ron Hines).

On a final note--I wanted to let readers know that this will be my last issue as a contributor to the Bulletin. Next week I will start a position at the Illinois Natural History Survey, Center for Ecological Entomology, as the state coordinator of the Cooperative Agriculture Pest Survey, overseeing survey efforts on invasive species that are a threat to Illinois. I don't think I could ever express how much I have enjoyed being a part of University of Illinois Extension. I have learned a tremendous amount during my time in this position and have loved meeting and interacting with everyone along the way. Thanks to all who have made the past three years such a great experience. I'm sure I will still see a lot of you at meetings and field days. Be sure to stop by to say hello.--Kelly Cook

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