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Black cutworm larvae coming from eggs laid earlier this spring are approaching the 4^th instar (worm stage) stage of growth. This is the growth stage at which the larvae are capable of cutting corn plants above and below the soil surface. Smaller instars will often leaf feed causing minor defoliation of corn seedlings, but damage increases significantly as the larvae grow to 4^th instar or larger stages and begin cutting plants. A predictive model is used to predict the different developmental stages for BCW. The model is based on intensive captures of moths during early spring and uses both a 30-year average of meteorological data along with real time data collected from several weather stations located throughout Missouri. The predicted date of first cutting may change by location as current 2007 meteorological data are entered into the model.

Scouting activities should occur from first emergence of corn plants and continue through the 5^th leaf stage of plant development. If this is not possible, then scouting of fields should begin a minimum of one week prior to the predicted date of cutting. Early damage by black cutworm larvae smaller than 4^th instars may be visible as leaf feeding on corn plants. Some reports of black cutworm larvae cutting field corn have been received from southern Missouri during the past week. The black cutworm model predicts additional cutting in many areas of the state during the next two weeks.

For more information on the black cutworm predictive model and the counties currently monitoring for black cutworm, please visit our Website at: http://ipm.missouri.edu/pestmonitoring/blackcutworm/index.htm

Black cutworm infestations may occur in scattered areas within a field or be found throughout the entire field. When scouting be sure to check all areas of the field, but focus some effort on those areas of the field where black cutworm infestations have been found in the past. Although the economic threshold for black cutworm varies from state to state, under normal conditions in Missouri treatment is recommended when cutting of corn seedlings reach or exceed 4-6% cutting above ground and 2-3% cutting below ground. These thresholds are based on the location of the plant growing point at the time of cutting by black cutworm and the potential for yield loss. Cut plants may be left on the soil surface or partially pulled into the soil by the larvae. If the economic threshold is reached, then treatment with a recommended insecticide is justified. It is possible for a field of corn to be infested more than once by black cutworm due to migratory patterns of arriving moths.

Corn fields most at risk from this pest are those late planted and have a history of winter annual weeds in the field. Scouting for this pest on seedling corn should begin with emergence and continue through the 5^th leaf stage of plant development. Seed treatments will provide partial control of this pest, but heavy populations of larvae may cause significant damage in seed treated fields. The Herculex event has been shown to provide excellent control of black cutworm in Missouri field trials whereas other available transgenic events have not provided control for this insect in field corn.

Read and follow all label direction, precautions, and restrictions.
* Designated a restricted use product.

Wayne Bailey
573-864-9905
BaileyW@missouri.edu