Corn Billbugs
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Symptoms of Corn Billbugs
- Corn leaves twisted and fail to uncurl because of corn billbugs
- Rows of oval holes in whorl leaves
- Small plants may be killed
- Excessive tillers on surviving plants
- Injury often more severe in border rows
- Corn susceptible to injury to the V6 leaf stage
- Larvae will tunnel into the base of the plant
Pest ID
Key Characteristics
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All billbugs have their mouthparts at the end of a "snout" or "bill" from which they get their name (see image below)
Related Species
Corn billbug damage can be easily confused with wireworm, cutworm, seedcorn maggot, stink bug and seedcorn beetle.
Pest Facts and Impact on Crop
- There are several species, primarily of the Sphenophorus genus: bluegrass billbug, maize billbug (black), southern corn billbug (brown or gray), clay-colored billbug (tan and cream striped)
- Importance relatively minor but increasing in no-till or other heavy cover rotations
- No significant natural enemies known
- Host range is primarily larger grasses, sedges and rushes
- Small corn plants may be killed or misshapen by adult feeding
- Plants to V6 leaf stage may tiller and be deformed
- Severe infestations have reduced yields up to 40%
- Damage is most severe in yellow nutsedge-infested fields or along border rows with this weed
Yellow Nutsedge is recognized as a major host.
Favorable Conditions
- Poorly drained, organic soils
- Corn-after-corn fields
- No-till corn fields
- Fields infested with yellow nutsedge or grassy perennials with a heavy corm or rootstock
Distribution
Billbugs that sometime feed on corn exist across the United States but are more of a problem in the Southeast and the Southern Corn Belt
Common Billbug Species
Southern Corn Billbug (photo above)
Maize Billbug (photo above)
Clay-Colored Billbug (photo above)
Bluegrass Billbug (photo above)
(photo by Jeff Hahn, University of Minnesota)
Life Cycle
- Adults often leave field in fail and overwinter in protected areas around cornfield
- Adults crawl, or rarely fly, back into the field; they may play dead when distributed
Management Practices for Corn Billbugs
Transgenic offerings are not available for this pest.
Cultural Controls:
- Crop rotation with a non-grass crop
- Early planting with good fertility to grow the seedling rapidly past the susceptible stages
- Plant strong emerging and fast-growing hybrids
- Control yellow nutsedge and other weeds
- Scout susceptible fields for first 3 weeks after emergence
Chemical Controls:
- At-planting soil insecticide
- Seed treatment insecticide may reduce pressure
- Rescue treatments may be used with fair success if fields are scouted shortly after corn emergence
*Photo of billbug larva from Purdue University Extension Service