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Keep your eyes peeled for black cutworms

Agriculture.com Staff 06/11/2009 @ 10:39am

The infestation window for black cutworm is now open in most of the Corn Belt. Growers need to scout fields now for black cutworm to optimize plant stands and minimize potential yield damage, according to company and university reports.

Beginning with black cutworm, the other members of the multi-pest complex -- corn earworm, Western bean cutworm, fall armyworm, stalk borer and sugarcane borer -- can cause significant economic losses due to their erratic infestation patterns, abundant numbers and the destruction they create throughout the growing season.

"So far this season, black cutworms are very active in the southern growing areas, and late planting in the northern growing areas will increase the number of black cutworms there. In addition, growers using no-till planting techniques will have a higher concentration of black cutworms in their fields," says Bruce Battles, agronomy marketing manager for Syngenta. "Unfortunately, the seed technology available today means that corn is still very susceptible to the pests that make up the multi-pest complex. Growers need to be vigilant about scouting to ensure the best possible yield in the fall."

Due to continued planting delays in some areas, officials with Syngenta Seeds recommends growers continue scouting for black cutworm.

Two things must be balanced when deciding whether to apply pesticide, according to Iowa State University (ISU) Extension entomologists Erin Hodgson and Jon Tollefson: The cost of control and the value of the commodity that will be saved. Action thresholds are commonly used in field crop entomology, and are defined as the pest density at which chemical controls should be applied. Action thresholds are generally meant to be dynamic based on crop market value and ever-changing control costs.

An action threshold has been established for black cutworm larval damage in corn. Last year, 2008, corn was much more valuable and the thresholds were lowered. This year corn prices are somewhat lower and it would be appropriate to raise the threshold accordingly, i.e., don’t spend money on control unless it is profitable. This shows that it would be appropriate to routinely adjust the control action threshold as the expected yield and price per bushel of corn changes and the cost of control increases or decreases, according to the ISU specialists.

According to Syngenta, the black cutworm can cause substantial damage to growers' yield potential if not stopped early. This pest prefers to attack corn from emergence to V5, the five-leaf corn stage. Smaller black cutworm larvae initially feed on leaves and stems and can quickly cause big stand losses. The most commonly used thresholds for triggering insecticide applications are when small larvae are present with 2% to 3% clipped plants, and when 4% to 5% clipped plants occur with larger larvae.

The infestation window for black cutworm is now open in most of the Corn Belt. Growers need to scout fields now for black cutworm to optimize plant stands and minimize potential yield damage, according to company and university reports.

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