5 MIN READ

Identification of Early Season Insects in Corn

March 3, 2024

Table 1. Timing of plant injuries from early season corn pests.

Timing of plant injuries from early season corn pests.

Table 2. Diagnostic Injury of Common Early Season Corn Pests.

Diagnostic Injury of Common Early Season Corn Pests

Where to Find Insect Pests

Early season insects can be found attacking the seed (seedcorn maggot, seedcorn beetle), the seed and below-ground parts of the seedling (wireworm, sugarcane beetle), the roots (white grubs), or the underground stem (sandhill cutworm). A small garden trowel or pocketknife are handy tools to use when searching for below-ground pests.

Two examples of below-ground pests that might be found while digging are corn rootworm larvae and white grubs. Corn rootworm larvae may be present during the later stages of early season growth, but may be too small to readily detect. If detected, they will have a brown to black head and a brown to black anal plate (Figure 4, Table 2). White grubs—a generic term for the larval stage of insects like the Japanese beetle, rose or sand chafer, and May or June beetles, though true white grubs are the larval stage of May and June beetles—can be identified by the raster pattern, or the setae (hair) pattern on the posterior end (Figure 13, Table 2). Michigan State University has developed an excellent publication that can be used to help identify white grubs in the field: https://www.canr.msu.edu/news/severe-grub-damage-spotted-in-northern-michigan-grass-hay-field

Some of these insect pests feed above ground but can also be found below ground. For example, the cutworm species feed above ground at night but spend the day under soil clods.

Reference Images

Black cutworm. Image courtesy of Roger Schmidt, University of Wisconsin-Madison, Bugwood.org.
Figure 1. Black cutworm. Image courtesy of Roger Schmidt, University of Wisconsin-Madison, Bugwood.org.


Seed Corn Maggot image
Figure 2. Claybacked cutworm. Image courtesy of James Kalisch, University of Nebraska, Bugwood.org.


Common Stalk Borer. Image courtesy of James Kalisch, University of Nebraska, Bugwood.org.
Figure 3. Common Stalk Borer. Image courtesy of James Kalisch, University of Nebraska, Bugwood.org.


Corn rootworm larvae. Image courtesy of Scott Bauer, USDA Agricultural Research Service, Bugwood.org.
Figure 4. Corn rootworm larvae. Image courtesy of Scott Bauer, USDA Agricultural Research Service, Bugwood.org.


European corn borer. Image courtesy of Frank Peairs, Colorado State University, Bugwood.org.
Figure 5. European corn borer. Image courtesy of Frank Peairs, Colorado State University, Bugwood.org.


Maize billbug image
Figure 6. Maize billbug. Image courtesy of Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org.



Sandhill cutworm
Figure 8. Sandhill cutworm. Image courtesy of James Kalisch, University of Nebraska, Bugwood.org.


Seed corn maggot.
Figure 9. Seed corn maggot.


Southern corn stalk borer.
Figure 10. Southern corn stalk borer. Image courtesy of Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org.


Southwestern corn borer.
Figure 11. Southwestern corn borer. Image courtesy of Frank Peairs, Colorado State University, Bugwood.org.


Sugarcane beetle.
Figure 12. Sugarcane beetle. Image courtesy of Clemson University, USDA Cooperative Extension Slide Series, Bugwood.org.


White grub.
Figure 13. White grub. Image courtesy of Alton N. Sparks, Jr., University of Georgia, Bugwood.org.


Wireworms.
Figure 14. Wireworms. Image courtesy of Frank Peairs, Colorado State University, Bugwood.org.

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