Watching the WI DATCP Wisconsin Pest Bulletin black light trap network, we know that black cutworm eggs are being laid and larvae have started to hatch near Beloit and La Crosse.
Black cutworm activity approaching in Corn
Eileen Cullen, Extension Entomologist, UW Entomology Department
Thursday, May 18, 2006
Article for print --> Black cutworm_May 17 _2_.pdf
Watching the WI DATCP Wisconsin Pest Bulletin black light trap network, we know that black cutworm eggs are being laid and larvae have started to hatch near Beloit and La Crosse. As black cutworm moths migrate to WI from overwintering sites in the southeastern U.S., oviposition is typically concentrated on low-growing vegetation such as chickweed, curly dock, mustards or plant residue from the previous year’s crop. Generally, black cutworm moths will not lay eggs in fields that have already been tilled and planted. Late planted corn fields tend to be most heavily damaged during an outbreak of black cutworms.
Photo: Peter Sonnentag, UW Madison
Black cutworm moths have a wingspan of 1.25 to 2 inches. The forewing is mottled dark brown to gray with a distinctive small dark “dagger” marking pointing outwards in the direction of the outer wing margin. The hindwings are light gray or brown with darker brown wing veins visible. Larval black cutworms are divided into segments. On each segment there are four small dots, (“tubercles”). Larvae have a “pebbly” skin texture, light gray to black, with an overall “greasy” appearance.
WI DATCP also operates a black cutworm pheromone trap network, from which degree days can be accumulated to help predict when cutting stage larvae may be present in corn fields. As of May 12th, pheromone trap counts last week were as follows: Janesville 6, East Preston 3, Tomah 1, Sparta 2, Cataract 3, Ontario 0, and 0 or 1 at 19 additional southwestern Wisconsin trapping sites. The Wisconsin Pest Bulletin is posted each Friday at http://pestbulletin.wi.gov/, I encourage you to continue checking each week for update on black cutworm pheromone trap captures.
Black cutworm is an occasional pest in WI, and catching moths in black light or pheromone traps does not indicate the intensity of cutting damage, nor that an outbreak is underway. Field scouting near anticipated cutting time is the only reliable approach to determine if a problem exists. Timely detection is critical and post emergence insecticide applications should be based on percent of damaged plants in a sampled field, size (vulnerability) of the corn plants, and size of the black cutworm larvae (preventable yield loss). The corn crop will be most vulnerable to cutworm feeding damage during the first ten days to two weeks following emergence.
To scout, examine a minimum of 250 plants (e.g., 50 plants in each of 5 locations) in a field. When damaged plants are found, dig around the base of the plant for live cutworms. Foliar insecticides should be considered in IPM programs utilizing chemical control when 2-4 percent of the plants are cut below ground, or 5 percent of the plants are cut above the soil surface, and cutworm larvae smaller than 6th instar or smaller are present.
When corn plants have reached the V5 stage with five fully developed leaves, plants have a large enough stalk diameter that larger instar larvae can no longer cut plants.
For more information on staging black cutworm larval instars (there are 7 total) and to view a list of insecticides labeled for black cutworm, consult:
Wisconsin-Extension bulletin number A3646 "Field Crop Pest Management in Wisconsin".
You can access the bulletin on-line at UW-Extension publications http://cecommerce.uwex.edu/. From the main page, follow the “Agriculture” link at the top left of page and click on “Crops and Forages”. Black cutworm information on pp. 62-63; and 72 of Publication A3646.
Article for print --> Black cutworm_May 17 _2_.pdf