Agronomic Crop Insect Scouting

David Owens, Extension Entomologist; owensd@udel.edu

Watch out for seedcorn maggot this week and next if you are working a cover crop in. Seedcorn maggot peak second generation activity is predicted. This does not mean that flies can’t affect a stand after the peak date. Fields with cool soil, higher organic matter and incorporation of a green cover crop are at greater risk. This doesn’t mean SCM will show up; it can be a spotty pest. They sometimes also show up if only a couple of these variables are present.

Be sure to scout corn for early season Lepidopteran pests. True armyworm larvae can be found in seedling corn. Thresholds are pretty high, 25% infested plants. Although true armyworm moth activity seems to have diminished in the area, black cutworm moths are active. It takes 300 degree days base 50 °F for eggs to hatch and larvae grow large enough to cut plants. Having said that, some large larvae have been reported in low numbers cutting seedlings. Signs of early larvae are multiple circular holes in a straight line across the leaf blade. Thresholds are 10% feeding damage or 3% cut seedlings in 1-2 leaf corn.

Although it has been warm and windy this spring and slug counts in fields that were heavily affected last year are much lower, do be on the lookout for slug activity. We found slug eggs present in some areas this week; when they hatch, juvenile slugs can cause quite a bit of feeding injury.

Early Season Moth Activity

Trap Location True Armyworm per night Black Cutworm per night
Willards, MD 0.3 0.7
Salisbury, MD 0 1.3
Laurel, DE 0.2 2.8
Seaford, DE 1 1
Bridgeville, DE 0 0.7
Harrington, DE 0 3.7
Smyrna, DE 0.2 11
Kenton, DE 0.3 1.7
Pearson’s Corner, DE 0.1 3.1
Sudlersville, MD 0 5.1
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