Issue No. 14/June 24, 2005
Corn Rootworm Larvae Abundant
An update is given regarding the large numbers of rootwarm larvae that are being reported from throughout the state.
Add Japanese Beetles to the List of Concerns
A new report of Japanese beetle captures means we will be watching for them to threaten corn production (silk clipping during pollination) and soybean production (defoliation in excess of 30%). Keep scouting.
Don't Wait to Begin Examining Soybean Fields for Spider Mites
The situation with twospotted spider mites infesting soybeans in areas of Illinois that are dry has worsened. Producers are urged to scout thoroughly now before the symptoms become dramatic (i.e., dead or dying soybeans). Make certain to diagnose any problem properly.
The Soybean Aphid Watch Continues
People throughout the Midwest continue to monitor soybean aphid populations. We have not witnessed much of an increase in densities from last week (June 13) to this week (June 20), at least not in Illinois.
We Probably Are in for Tough Times with Corn Rootworms
Reports of poor performance by soil insecticides and insecticidal seed treatments in cornfields planted in April have been numerous and widespread. Significant corn rootworm larval injury in corn planted after soybeans has been observed in counties south of I-70. Also, the emergence of rootworm adults is a reminder that as corn begins to tassel and silk, both rootworm adults and Japanese beetle adults may interfere with pollination.
Corn Leaf Aphids
As warm temperatures and lack of moisture around the state continue, be aware of corn leaf aphids in your cornfields and the potential for them to affect pollination. They often go unnoticed until populations reach very high levels.
European Corn Borer Larvae Found in Whorls
Keep an eye out for first-generation European corn borer larvae. If possible, examine 25 consecutive plants in each of five random locations for every 80 acres in a field.
Grasshopper Nymphs Moving into Field Edges
If the hot and dry weather continues, we can expect grasshoppers to become a problem in some areas. Grasshoppers begin to move into field margins of corn and soybeans when weedy hosts begin to dry up. Defoliation can be extensive if densities are large.
Burrower Bugs Make an Appearance in Several Fields
Burrower bugs have been identified in cornfields and soybean fields. Control measures are unlikely to ever be necessary, but be aware that you may encounter these insects during your scouting trips.
Rust Is Common on Many Crops, but Not Yet on Soybeans in Illinois
Rust diseases and rust fungi are among the most common and damaging diseases of crops and other plants worldwide. Rust diseases that may occur in Illinois on a variety of horticultural and agricultural plants are reviewed.
New Herbicide Injury on Soybean Fact Sheet
A new fact sheet available online covers a wide range of herbicides and “typical” symptoms associated with injury from them.
How quickly are crops losing yield potential as they continue growing without renewal of soil water? Based on similar patterns in previous years, crops are probably hanging on better than we fear. Soybean growth is being inhibited more than corn growth under current dry conditions.
Reports are provided this issue for northern, southern, and west-central Illinois.