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Insurance pest management the norm in many Midwest corn and soybean fields

Published March 22, 2012

Insurance pest management, rather than integrated pest management, is becoming an increasingly common form of IPM in commercial corn and soybean fields.

"The increased use of crop production inputs without scouting or use of economic thresholds is being exacerbated by high commodity prices and will likely continue under the current crop production parameters," said professor of entomology and crop sciences Extension coordinator Mike Gray. "However, there are likely to be negative long-term consequences, such as insecticide resistance and reductions in natural enemy populations."

Over 50 years ago, some University of California entomologists outlined the key concepts in IPM. Specifically:

- Insect densities fluctuate within a growing season and over long periods of time, around a general equilibrium position,

- Densities are affected by biotic (predators, parasitoids, diseases) and abiotic (weather) factors,

- Densities can be estimated (scouted) and economic thresholds used to help make treatment decisions,

- The economic threshold can be used as a guideline to determine when to apply an insecticide to prevent insect numbers from increasing to a point where important economic loss will occur,

- Insect pest populations should be managed to optimize natural control.

"The question," said Gray, "is whether these IPM pillars are still relevant." The modern corn and soybean production system is characterized by fewer producers, increasing farm size and absentee landowners, and high commodity prices. Pest management decisions are often influenced by input suppliers, corn is increasingly viewed as a biofuel, and the market place is increasingly driven by transgenic traits.

Gray used an anonymous electronic audience response system (hand-held clickers) at seven regional meetings of the Corn and Soybean Classics to gather data on current insect control practices.

He found that during the past several growing seasons, the use of tank-mix applications containing both an insecticide and fungicide has been common in Illinois corn and soybean fields. In 2011, an average of 48 percent (sample size = 653) of the producers who responded said they treated their soybeans with an insecticide and fungicide combination. A smaller percentage of producers (33 percent, sample size = 645) indicated they treated their corn with a tank mix during the 2011 growing season.

Of most interest and concern is the admission by 50 percent of all producers (sample size = 423), and the majority of producers in Bloomington, Mt. Vernon, and Quincy, that they did not scout their fields or use a threshold to make their treatment decision.

These findings are surprising in light of the results of surveys led by Gray and crop sciences researchers Ron Estes and Nick Tinsley in July-August 2011. They found insect densities in corn and soybean fields to be very low across 47 Illinois counties. The numbers of bean leaf beetles, Japanese beetles, green cloverworms, and western corn rootworm adults were well below economic levels in most fields. Overall defoliation levels in soybean fields were low, and silk clipping in corn fields was negligible.