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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Black cutworm. Note the small, black dagger-shaped marking on each outer wing.
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Black cutworms likely to begin cutting soon

Some insects such as the western corn rootworm, soybean aphid, bean leaf beetle and corn flea beetle overwinter in Illinois, while others such as black cutworms, army worms and corn earworms migrate into the state from more southerly regions.

Each year, many members of the University of Illinois Extension field staff work with the Illinois Natural History Survey's Kelly Estes to gauge local and state-wide risk of insect damage to corn and soybean. This is done through the use of pheromone traps.

Black cutworm (BCW) moths are attracted to sex pheromones in pheromone traps and when they investigate the trap expecting to find a mate, they are captured on a sticky surface (Figures). The BCW trap at the Northwestern Illinois Agricultural Research and Demonstration Center (NWIARDC) accumulated 11 moths in a 2 day period ending May 15th. This is considered a 'significant flight' by entomologists.

Significant flights indicate that high populations of BCWs have arrived in an area and have begun seeking mates. After mating, BCW females lay their eggs on weeds. If these weeds happen to be in a corn field when eggs hatch, the larvae begin to feed on corn, initially causing small pin-sized holes.

Just like corn plants that need to accumulate degree days to reach certain points in their life cycle, the same concept applies to BCWs. It takes approximately 300 degree days for larvae to reach a size (4th instar) where they can begin to cut corn plants. If a corn plant is cut below the growing point, it will not survive. Corn is most at risk for economic damage between the 1 and 4 leaf stage of growth.

According to historical weather data at the NWIARDC, we would expect to reach 300 degree days, and black cutworms to begin cutting around June 6th.

The cool, wet 2013 growing year has delayed many field operations including pre-emergence herbicide applications and planting. Fields most at risk for black cutworm injury include those heavily infested with winter annual weeds.

Trapping is a way to gauge whether the pest is in the area and when BCWs may begin cutting. Decisions about whether to spray insecticides should not be based projected cutting dates alone. Certain Bt traits provide protection, but under heavy infestations, may not provide adequate control. Scouting is recommended before considering an insecticide treatment.

There are several resources that can be explored to gather more information about BCWs and pheromone trapping.

  • University of Illinois Entomology Extension Specialist Mike Gray recently released a video in the Bulletin where he discussed BCW in detail.
  • A fact sheet about BCW is available on the University of Illinois IPM website.
  • If you are interested in BCW trapping data from other areas of the state or are interested in other insects that are part of the trapping network, please visit the North Central IPM website.

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