SEE Mail Issue 020524 (May 24, 2002)

	Extension Entomology Mail Mike Catangui, Ph.D. Associate Professor & Extension Entomologist
May 24, 2002 (Issue 020524)

Corn seedlings, already stressed by the cold weather, may be vulnerable to cutworm damage.
Corn growers are encouraged to inspect their fields as soon as possible.

We have been tracking the black cutworm moths since early April and high moth numbers were
observed in the southeast last April 20-23. Thanks to Pioneer-A Dupont Company, Sax Agricultural
Services, and Syngenta Seeds for participating in this project.

Black cutworm moths are attracted to and prefer to lay eggs on weedy and wet low-lying fields. Fields
with these characteristics must be scouted first.

Larvae produced by the April moths are now cutting corn seedlings. Clay, Union, and Yankton Counties
are currently reporting significant infestations of black cutworms in seedling corn.

I personally inspected and found significant numbers of black cutworms at the SE Research Farm
near Beresford today (May 23). Some of the cutworms were about an inch long but some were
less than half an inch long.

Thanks to Meckling Fertilizer and Sax Agricultural Services for reporting infestations near Gayville
and Alcester, respectively. The pictures above are from the SE Farm taken today (May 23).

Last year (2001), cornfields along Interstate 29 from Union County in the south to Roberts County
in the north did experience significant black cutworm infestations. The same areas must be scouted
again this season.

Larvae of black cutworms can be very damaging because they cut the corn growing points from under
the soil. Wilted seedlings, scattered pieces of leaves, and small holes on leaves are common signs
of black cutworm infestation.

Cutworms are active at night and hide under loose soil during the day. Scouting during the day involves
scratching the soil surface to expose hidden larvae.

Insecticide treatment may be considered if 5% (1 in 20) of the seedlings show signs of cutting or leaf
feeding and most of the larvae are still less than an inch long.

Insecticides labeled for use against cutworm larvae on corn as seedling foliar sprays include Asana XL
(5.9-9.6 fluid ounces per acre), Capture 2EC (2.1-6.4 fluid ounces per acre), Lorsban 4E (1-4 pints per
acre), Mustang 1.5EW (1.4-3.0 fluid ounces per acre), Pounce 3.2EC (4-8 fluid ounces per acre), and
Warrior (1.92-3.20 fluid ounces per acre). Read and follow all directions on the label.

Most (but not all) corn rootworm insecticides applied at planting also protects against black cutworms.

Two species of cutworms commonly infest corn seedlings in SD. Dingy cutworms overwinter as partially
grown larvae in the soil then resume feeding in the spring. Dingy cutworms are not as damaging as
black cutworms because they usually cut seedlings above the growing point.