Corn
Corn
Variety trials
Pest Management
Recommendations for pest management
Sampling Guidelines
| Growth Stage: Pre-Planting | |
| Pest | Sampling Method |
| White grub, Wireworm | Sample one square foot of soil 12 inches deep; one sample should be taken for each 10 acres with a minimum of 5 sites per field; field should not be tilled before samples are taken and soil temperature at 6 inches should be 45-50 degrees F. |
| Growth Stage: Emergence to Early Whorl | |
| Cutworms | Examine 10 plants in 10 locations for the presence of leaf feeding (small irregular holes) and cut plants; also look for live cutworms and estimate the average size of the larvae |
| Slugs | Examine 10 plants in 10 locations for the presence of feeding damage and slime trails; you will need to observe plants at night or during cloudy conditions to actually observe slugs feeding in plants; be sure to also check for slugs under surface trash and in open seed slots |
| Flea beetles, Cereal leaf beetle, and European corn borer | Examine 10 plants in 10 locations, count the number of beetles per plant and percent plants infested for the two beetles; count the percent infested plants for European corn borer, pull the whorls our of 5-10 plants per field to determine the size of ECB larvae as well as the average number per plant |
| Growth Stage: Mid-Whorl – Tassel Emergence | |
| Stalk borer, True Armyworm, European corn borer, Corn Earworm, Fall Armyworm | Examine 10 plants in 10 locations and count the percent infested plants |
| Growth Stage: Silking | |
| Corn rootworms | Count the number of beetles on 5 plants in 10 locations |
Insect Thresholds
Growth Stage |
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| Pest | Preplant | Emergence to 4 leaf stage | 5 leaf stage to silking |
| White Grubs | 1 per sq. ft. | ||
| Wireworms | 1 per sq. ft. | ||
| Slugs | 3 per sq. ft. | 3-5 per plant | |
| Cutworms | 1-2 leaf – 3% cut or 10% feeding damage 2-4 leaf – 5% cut and larvae present | ||
| Corn flea beetle | 5-6 per plant and 50% plants damaged | ||
| Common stalk borer | 2 leaf – 4% infested plants 3 leaf – 6% infested plants 4 leaf – 10% infested plants |
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| European corn borer | 50% plants infested (irrigated)80% plants infested (non-irrigated) | 50% plants infested (irrigated)80% plants infested (non-irrigated) | |
| True armyworm | 25% plants infested and larvae < 1″ | 25% plants infested and larvae < 1″ | |
| Cereal leaf beetle | 10 per plant and 50% plants damaged | ||
| Fall armyworm | 75% plants infested with 1 worm or 50% plants with 2 or more worms | ||
| Northern corn rootworm * | 2 adult beetles per plant | ||
| Western corn rootworm * | 1 adult beetle per plant | ||
* if both present – divide number of northern corn rootworms by two and add to number of western corn rootworms
Fact sheets
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