Black Cutworm Activity Reported

May 22, 2008

Because of the planting delays and cooler temperatures encountered this spring, there could be a greater potential for black cutworm damage this season. Iowa State University Extension, University of Missouri and the University of Illinois have recently released their predicted first cutting dates for black cutworm. Corn plants are susceptible to cutting through the 5th leaf stage of development and from observations; most of the corn will not be past the 5th leaf stage before the predicted first cutting dates.
 
Here is a breakdown of predicted first cutting dates for several different states:
 
¬    Southern Iowa- May 17-18
¬    Central Iowa- May 18-20
¬    Northern Iowa- May 22-23
 
¬    Central and Southern Missouri- May 11
¬    Northern Missouri- May 15
 
¬    Southern Illinois- May 12
¬    Northern Illinois- May 20
 
¬    Eastern Nebraska- Follow Iowa cutting dates
 
Black Cutworm moths migrate northward and will be attracted to weedy, low, poorly drained fields. Also, fields rotated from soybeans tend to be targeted for egg laying. Fields with winter annual or early spring annual weeds that are present during or close to planting should be scouted first and then low lying fields being rotated from soybeans.

Scouting for cutworm damage should begin near the first predicted cutting date and should continue through the 5th leaf stage. To scout for cutworm damage, select several locations within the field and inspect plants for leaf damage or cut plants. Leaf damage will appear as irregular holes, generally along the edge of the leaf. If leaf feeding is observed, mark 100 plants in these locations and monitor them daily for cutting through the 5th leaf stage. 

The economic thresholds for cutting by black cutworm larvae have been revised this season due to the high price of corn. Iowa State Extension and the University of Missouri Extension recommend treatment when 1-2 percent or more of plants have been cut. Below is a list of insecticides labeled for treatment of black cutworm infestations.
 
 Ambush®                6.4-12.8 oz/acre
Warrior ®                1.92-3.2 oz/acre
Asana® XL                5.8-9.6 oz/acre
Baythroid® 2            0.8-1.6 oz/acre
Discipline® 2EC        2.1-6.4 oz/acre
Capture® 2EC           2.1-6.4 oz/acre
Hero®                      2.6-6.1 oz/acre
Mustang Max®          1.28-2.8 oz/acre
Lorsba®n 4E             1-2 pt/acre
Nufos® 4E                1-2 pt/acre
Penncap-M ®            4 pt/acre
Pounce® 3.2EC         4-8 oz/acre
Sevin® XLR Plus        2 qt/acre
Source: Iowa State University Extension
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