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They're on Their Way: Black Cutworms Arrive in Southern Illinois Traps

April 10, 2003

It's that time of year when black cutworm pheromone traps are swinging in the wind, the synthetic sex pheromone calling out to the unsuspecting males of the species. We used to have a relatively large network of black cutworm pheromone traps monitored by willing cooperators throughout Illinois. The results from those efforts gave us a reasonable idea of the intensities and localities of black cutworm flights from year to year. Unfortunately, we had to discontinue the network because we depleted our funding for the program. So now we rely on the kindness of strangers (and friends) to send us information voluntarily. If you have set up black cutworm pheromone traps this spring, don't hesitate to send us your moth-capture data. We'll be happy to share it with others.

Black cutworm pheromone trap. (Photo courtesy of Ron Hines, Dixon Springs Agricultural Center.)

Ron Hines, senior research specialist at the University of Illinois Dixon Springs Agricultural Center, has been vigilant this spring, and he already has observed an intense capture of black cutworm males in one of his traps. An intense capture is defined as nine or more moths captured in a 1- to 2-day period. On April 7, Ron found 19 black cutworm moths in a pheromone trap in Pulaski County. He checked the traps on the morning of April 7, after the storms that passed through the preceding weekend. The trap in Pulaski County captured a total of 24 moths during the week of April 1 through April 8 (counts are accumulated every Tuesday). You can obtain more particulars about Ron's trapping efforts from the "Hines Report" on our IPM Web site

Jeff Staley, with Wabash Service Company in Ridgway (Gallatin County), also provided information from the black cutworm pheromone traps that he is monitoring. Like Ron Hines, Jeff reported an intense capture from two of his traps after the April 5-6 weekend. He captured 12 black cutworm males in one trap and 11 in another trap. So the traps in southern Illinois are picking up the leading edge of the migration of this pest from the South.

We use the dates of intense captures to run a degree-day-driven model that projects when the first signs of cutting of corn seedlings might occur. We anticipate cutting of corn plants by black cutworms about 300 degree-days (base 50°) after an intense capture. Obviously, the occurrence of cutting injury depends on many other factors, including the presence of larvae in the field, prevailing weather conditions, and conditions of the field. For example, a field that has been tilled and planted before black cutworm moths arrive in the area usually escapes black cutworm damage. On the other hand, a field that has not been tilled and planted and is full of weeds that are attractive to egg-laying black cutworm females may be a good candidate for black cutworm damage. We provide the output from the degree-day model as an early warning for people scouting for black cutworms and signs of their presence. Only with legwork will you be able to determine whether black cutworms pose a threat in any given field.

Black cutworm larva and cut corn seedling.

Some field cultivation and planting occurred in some areas of Illinois early in the week of March 31, but cold, wet weather slowed down that activity. If fieldwork resumes soon, a lot of growers will be able to plant early enough to avoid concern about black cutworms. If fieldwork is delayed by rains and black cutworm moths continue their migration into Illinois, the potential for black cutworm damage increases.

We continue to encourage most growers to rely on timely field scouting and application of an insecticide only if the level of cutworm damage exceeds published thresholds. The application of insecticides before or at planting to prevent black cutworm damage often does not pay off economically, especially if corn is planted relatively early. Some growers, however, have had a history of black cutworm problems in certain fields, so the application of preventive insecticide might be justified. Table 1 shows the preventive insecticides that might provide adequate control of black cutworms in the event of an infestation. The information in Table 1 was extracted from the labels. Please consult the insecticide labels for additional information, including directions for use and precautionary statements.

Another product that may prevent substantial black cutworm damage is a corn hybrid with Herculex I Insect Protection. Herculex I transgenic hybrids contain a different protein (Cry1F) than YieldGard Corn Borer hybrids, which contain the Cry1Ab protein. Both proteins, however, were derived from the soil bacterium Bacillus thuringiensis. Herculex I and YieldGard Corn Borer are equivalent in their efficacy against European and southwestern corn borers. Other pest Lepidoptera controlled by Herculex I include black cutworm, corn earworm (suppression), and fall armyworm. The efficacy of Herculex I hybrids against black cutworms is essentially equivalent to the efficacy of insecticides applied at planting for control of black cutworms. Refer to the article "New Products for Insect Control" in issue no. 1 (March 21, 2003) of the Bulletin for more information about Herculex I products.

Please keep us posted regarding black cutworm activity in your area. Black cutworms seem to appear and cause damage rather suddenly, so early warnings are really helpful.--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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