No. 3 Article 3/April 22, 2011

Intense Captures of Black Cutworm Moths Reported in Several Locations

The stormy weather pattern across much of Illinois the past several weeks has led to numerous reports of black cutworm moth captures in pheromone traps. Robert Bellm, University of Illinois Extension crop systems educator, reported the following captures: Montgomery County, 8 moths captured, April 11-12; Madison County, 11 moths, April 14-16; Pike County, 10 moths, April 18.

By using moth capture data, we can begin to project when cutting may occur in a given area of the state. When 9 or more moths are caught over a 2-day period (intense capture), we use this point as our biofix for black cutworms to project when cutting of plants may begin to occur. The first three black cutworm instars are considered primarily leaf feeders. Once the fourth instar is reached, cutting may begin. This stage typically requires an accumulation of 312 to 364 degree days (base 50°F) beyond the intense capture date. For a complete description of life cycle and management information on black cutworm, please visit ipm.illinois.edu/fieldcrops/insects/black_cutworm.

Fields with flourishing winter annual weed populations are most susceptible to black cutworm damage. Black cutworm moths are very attracted to these weeds, on which they lay their eggs. Curled dock and yellow rocket are very attractive egg-laying targets. Cornfields that match these characteristics and are tilled and planted late in the spring are most prone to economic infestations of black cutworms and should be scouted carefully. Early signs of injury include pinhole leaf feeding.

In issue 2 of the Bulletin, Aaron Hager depicted the common sight of henbit and purple deadnettle turning fields purple this spring. I urge producers to scout those fields for signs of cutworm injury once corn begins to emerge later this spring. Even fields that have been planted to certain Bt hybrids may be susceptible to damage if there is a heavy infestation of black cutworm. Don't be lulled into complacency when using transgenic hybrids and assume complete protection against intense populations of this insect pest. Rescue treatments may still be required in some instances. Continued delays in spring tillage and planting will heighten the chances for black cutworm damage this spring. If you find significant infestations, I would be interested in learning where in the state these are occurring.--Mike Gray

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