No. 1 Article 3/March 22, 2012

Insurance Pest Management the Norm in Many Corn and Soybean Fields of the Midwest

The 7th International IPM Symposium will convene next week (March 27-29) in Memphis, Tennessee. Many of the presenters, including me, will focus on the status of IPM adoption by producers. Historically, the level of adoption has remained difficult to measure. A key measurement challenge has been the frustrating lack of consensus on a satisfactory definition or goal. Textbooks are filled with definitions and goals of IPM. Some within the IPM community have settled on the general goals of reducing the risks of crop production, reducing the risk of negative environmental consequences, and reducing the risk of negative human health and safety consequences. Accurately measuring reductions in these risks has been hard to quantify and more difficult to explain to the public and potential supporters of IPM programs than just measuring reductions in pesticide use--certainly a more simplistic approach, yet also more easily understood by the public, policy makers, and political supporters (new and old).

Over 50 years ago, entomologists at the University of California laid the foundation for many of the most important concepts in IPM:

  1. Insect densities fluctuate not only within a growing season but over long periods of time, and they have a general equilibrium position.
  2. Insect densities are affected by factors both biotic (predators, parasitoids, diseases) and abiotic (primarily weather).
  3. Insect densities can be estimated (scouted) and economic levels determined.
  4. A subeconomic density (economic threshold) can be used as a guideline to determine when an insecticide should be considered to prevent an increasing insect density from reaching a point where economic loss will occur (economic injury level).
  5. Insect pest populations should be managed, not eradicated, thus optimizing natural control.

A question that I often ask producers and will ask again in Memphis is this: Are these IPM pillars--scouting, economic thresholds, economic injury levels--still relevant in a modern corn and soybean production system? Currently, this system is characterized by fewer producers, increasing farm size, absentee landowners, pest management decisions often influenced by suppliers of inputs, corn increasingly viewed as a biofuel, high commodity prices, and a marketplace driven by transgenic traits.

In January 2012, I used an anonymous audience response system (handheld electronic clickers from Turning Technologies of Youngstown, Ohio) to gather input on current insect control practices at seven regional meetings of the University of Illinois Corn and Soybean Classics. These are meetings attended by producers and members of the agribusiness sector.

During the past several growing seasons, tank-mix applications containing both an insecticide and a fungicide have been in common use in corn and soybean fields across much of Illinois (Figure 1). An average of 48% (sample size = 653) of producers who responded indicated they had treated their soybeans with one of these combinations in 2011. Use was greatest in Moline (63% of 128 respondents) and Malta (60% of 97).

Figure 1. Answers provided at the 2012 Corn and Soybean Classics meetings to the question "Did you spray your soybean fields in 2011 with a tank mix of fungicide and insecticide?"

A smaller overall percentage of producers (33% of 645) indicated having treated their corn with a tank mix during the 2011 growing season (Figure 2). The percentages were highest in Bloomington (37% of 111), Malta (39% of 100), and Springfield (42% of 110).

Figure 2. Answers provided at the 2012 Corn and Soybean Classics Meeting to the question "Did you spray your cornfields in 2011 with a tank mix of fungicide and insecticide?"

Of most interest and concern is the admission by producers that 50% (sample size of 423) did not scout their fields or use a threshold to make their treatment decision (Figure 3). A majority of producers in Bloomington (58% of 78), Mt. Vernon (61% of 31), and Quincy (57% of 23) indicated they did not scout or use a threshold before making treatment decisions.

Figure 3. Answers provided at the 2012 Corn and Soybean Classics Meeting to the question "If you answered 'yes' to either question, did you scout your fields and use a threshold to make your decision?7quot;

In late July and early August of last year, several University of Illinois survey teams in the Department of Crop Sciences led by researchers Ron Estes, Nick Tinsley, and me found insect densities in corn and soybean fields to be very low across 47 Illinois counties. Within each of the 47 counties sampled, five cornfields and five soybean fields were selected at random. In the soybeans, sweep nets were used to take 100 sweeps per field. In corn, 20 consecutive plants in a row were sampled for western corn rootworm adults. The numbers of bean leaf beetles, Japanese beetles, green cloverworms, and western corn rootworm adults were well below economic levels in the great majority of fields. Though overall defoliation levels in soybean fields were low and silk clipping in cornfields was negligible, insecticide treatments were common last year, as evidenced by the responses received at the Classics.

It seems that a new form of IPM has become commonplace across many commercial corn and soybean fields--insurance pest management. The increased use of crop production inputs without scouting or use of economic thresholds is being exacerbated by high commodity prices, and it will probably continue under the current crop production parameters. However, there are likely to be unintended and unforeseen long-term negative consequences, such as insecticide resistance and reductions in natural enemy populations--the same potential undesirable outcomes mentioned more than 50 years ago by the University of California entomologists--when fundamental ecological principles of pest management are largely ignored.--Mike Gray

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