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Issue No. 8, Article 2/May 18, 2007

Maximizing Crop Production Inputs Does Not Equate to Integrated Pest Management

These are quickly changing times across the Corn Belt of the United States, manifested by the following significant changes, among others:

  • Surging interest and investment in biofuels
  • Favorable commodity prices
  • Significant increase in continuous corn acres
  • Escalating demand for triple-stack corn hybrids, even in areas where corn rootworms typically do not present a persistent economic threat
  • Use of insecticidal seed treatments (the neonicotinoids clothianidin and thiamethoxam) on every kernel of Bt seed
  • Increasing interest in the use of fungicides on corn
  • Concern over inadequate deployment or nondeployment of non-Bt corn refuges
  • Increasing reliance on a restricted spectrum of herbicides in corn and soybeans
  • Larger farms
  • Fewer farmers and more absentee landowners

Against this backdrop of factors, and many associated ones, the principles of integrated pest management (IPM) in the corn and soybean agroecosystem are increasingly being ignored. Of particular concern is the lack of integration of pest management tactics and the overreliance on single-tactic approaches without any scouting input. Some of the very costly and negative consequences associated with pesticide misuse and overuse are being forgotten. What are some examples?

  • Insecticide resistance
  • Secondary pest resurgence
  • Harmful effects against nontarget insects and other organisms
  • Potentially harmful pesticide residues on food products
  • Pesticide movement into our natural resources, such as ground and surface water

In a recent review article, several scientists described the many potential sublethal effects of pesticides on beneficial arthropods. (The citation for this article is Desneux, N., A. Decourtye, and J-M. Delpuech. 2007. The sublethal effects of pesticides on beneficial arthropods. Annual Review of Entomology 52: 81-106.) The authors described sublethal effects as "inducing no apparent mortality in the experimental population." Most of the scientific research on sublethal effects of pesticides has focused on two primary groups of arthropods, natural enemies and pollinators. Following are some examples of sublethal effects on arthropods the authors described in their review of the literature:

  • atypical development
  • reduced adult longevity
  • immunology (may increase or decrease)
  • reduced fecundity (biotic potential)
  • alteration of the sex ratio within a population
  • alteration of normal mobility patterns
  • alteration of navigation or orientation abilities
  • disruption of normal feeding behavior characteristics
  • interference with typical oviposition (egg-laying) behavior
  • interference with learning (of special importance with pollinators such as honey bees)

Even though no apparent mortality of natural enemies may be observed following an application of an insecticide, there may be numerous sublethal effects that have broader nontarget community impacts within a corn or soybean field. There still is much we have not learned with respect to the use of pesticides.

Pesticides will continue to play a vital role in IPM programs; however, greater care should be taken in using these inputs based on scouting and economic thresholds. There are many examples in the present agricultural climate in which the IPM paradigm has been put on the shelf.

Perhaps more than any recent entomological issue, the honey bee Colony Collapse Disorder (CCD) has captured the interest and attention of entomologists worldwide. The cause or causes of this disorder have not been determined. CCD has been reported in 27 states, but it has not been confirmed in Illinois at this time. In a 2005 journal article, some French scientists hypothesized that the decline in European honey bee populations since the mid-1990s was related to the use of systemic insecticides in field crops (specifically imidacloprid, a nicotinoid insecticide). (The citation for this article is Bonmatin, J.M., P.A. Marchand, R. Charvet, I. Moineau, E.R. Bengsch, and M.E. Colin. 2005. Quantification of imidacloprid uptake in maize crops. Journal of Agricultural and Food Chemistry 53: 5336-5341.)

Since 2004, the use of imidacloprid seed treatment on corn seed has been suspended in France. Even though the use of neonicotinoids (clothianidin and thiamethoxam) has soared across Illinois, due in part to the increasing demand for Bt seed, no honey bee colony collapses have been confirmed here. Investigators will continue to explore many possibilities (honey bee diseases, environmental factors, other pesticides) that may be linked to CCD.

Will we return to a more reasoned application of IPM tactics across the Corn Belt? Experience tells us that this may happen; however, let's hope that a movement back in the direction of IPM is not crisis driven.--Mike Gray and Kevin Steffey

Mike Gray
Kevin Steffey

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