No. 1 Article 5/March 19, 2009

IPM and the Integrated Control Concept: Progress after 50 Years in the Commercial Corn and Soybean Landscape?

Fifty years ago, a landmark paper--The Integrated Control Concept--was published by the California Agricultural Experiment Station (Hilgardia, Vol. 29, No. 2, pp. 81-99). The authors of this paradigm-shifting journal article were entomologists with the University of California system: Vernon M. Stern (Citrus Experiment Station Riverside), Ray F. Smith (Experiment Station, Berkeley), Robert van den Bosch (Citrus Experiment Station, Riverside), and Kenneth S. Hagen (Experiment Station, Berkeley).

After World War II, there were significant advances and successes with the control of insect pests (both agricultural and medical) with the widespread introduction of chlorinated hydrocarbon insecticides such as DDT. Initial results were so spectacular that some entomologists speculated that certain key insect pests could be eradicated. The promise of these "miraculous" products was short-lived. Stern and his colleagues, several years before the publication of Rachel Carson's Silent Spring in 1962, began to alert the scientific community of the many negative consequences resulting from the indiscriminate use of organic insecticides, such as 1) "arthropod resistance to insecticides"; 2) "secondary outbreaks of arthropods other than those against which control was originally directed"; 3) "the rapid resurgence of treated species necessitating repetitious insecticide applications"; 4) "the toxic insecticide residues on food and forage crops"; 5) "hazards to insecticide handlers and to persons, livestock, and wildlife subjected to contamination by drift"; and 6) "legal complications from suits and other actions pertaining to the above problem."

In recognition that these problems were significant and likely to worsen due to increasingly irrational approaches to insect control, these University of California entomologists began to describe concepts that are just as important and relevant today as they were 50 years ago, including economic injury level, economic threshold, general equilibrium position, integrated control, natural control, biological control, and selective insecticides. The authors of this seminal paper hoped that by applying these ecologically based concepts in the management of insect pests, future problems could be largely avoided.

A half-century has elapsed since Stern and his colleagues published their paper. Maybe now is a good time to pause and assess how well the integrated control concept is being applied in the commercial production of corn and soybeans in the Corn Belt of the United States. By examining the results of a few questions we asked participants at the 2009 Corn & Soybean Classics held in January, perhaps we can offer some insights.

The first question (Figure 1) focused on the relevance of economic thresholds in the production of corn and soybeans during a period in which input costs are high and many producers have seemingly adopted an "insurance approach" to pest management. The numbers of responses received (using Turning Point Technology to gather results) at Mt. Vernon, Champaign, Bloomington, Springfield, Moline, and Malta were 97, 160, 175, 212, 112, and 100, respectively. A range of 79% to 85% of those responding believe that the use of economic thresholds is still viable for managing insect pests in corn and soybean fields. However, 10% to 18% believe that economic thresholds are no longer relevant in the large-scale production of these crops. We are pleased that such a significant percentage of those polled still respect the viability of economic thresholds. Still, the results suggest that many acres of corn and soybeans are not scouted, thresholds are not used, and "insurance" insecticide applications continue to be made.

Figure 1. Do you think the use of economic thresholds is not relevant or is still viable?

Participants were asked a follow-up question regarding the primary criterion used to make insect control decisions in corn and soybean fields--control costs, potential yield benefits (with little concern about the level of insect infestation), or reliance on economic thresholds (Figure 2). The numbers of responses at Mt. Vernon, Champaign, Bloomington, Springfield, Moline, and Malta were 97, 163, 174, 204, 106, and 100, respectively. An average 73% of respondents indicated that their primary criterion for making insect control decisions is use of economic thresholds, similar to responses to the first question. Approximately 24% indicated that a potential yield benefit is their primary criterion. Based on the feedback from these two questions, we suspect that Stern and his cooperators would have been pleased at such an overall positive response to using economic thresh olds for insect management in corn and soybeans--not perfect for sure, but not bad.

Figure 2. Is your primary criterion for insect management decisions control cost, yield benefit, or economic threshold?

Certainly a factor in pest management that has changed agriculture in a revolutionary way is the introduction of transgenic corn and soybeans. When participants at the 2009 Classics were asked if they planted Bt corn in 2008, an overwhelming number indicated that they used Bt corn control insect pests (Figure 3). The numbers of responses at Mt. Vernon, Champaign, Bloomington, Springfield, Moline, and Malta were 90, 130, 118, 160, 93, and 93, respectively. More than 97% of respondents indicated that they planted a Bt corn hybrid in 2008, demonstrating remarkable adoption of this technology. Stern and his co-authors offered some forward-thinking perspectives on the use of Bt for insect management, relating specifically to their encouragement of the use of more selective insecticides: "More recently, interest has developed in the commercial use of virulent strains of Bacillus thuringiensis Berliner, for the control of certain truck- and field-crop pests in California. The use of disease pathogens as selective insecticides is in its infancy, but can be expected to increase in importance with additional research." We suspect that in several respects these California entomologists would have been delighted with the deployment of these selective Bt hybrids to control corn rootworms and some lepidopteran insect pests, such as European and southwestern corn borers. Would they have had some concerns as well? We believe one primary concern would be the lack of integration of other insect management tactics and an overreliance on transgenic technology, even when subeconomic densities of insect pests are the norm for many fields.

Figure 3. Did you plant a Bt hybrid in 2008?

On average, nearly 80% of respondents indicated that they would still plant a Bt corn hybrid even with the knowledge that anticipated damage levels of corn rootworm and/or European corn borer were anticipated to be low (Figure 4). The number of responses at Mt. Vernon, Champaign, Bloomington, Springfield, Moline, and Malta was 90, 140, 121, 159, 92, and 92, respectively. The use of an insect management tactic (insecticide or Bt hybrid) by a producer equipped with the knowledge that target pest densities are likely to be low (subeconomic) most likely would have been met with disapproval by Stern and his colleagues. We also believe that there will be unintended consequences resulting from this extensive use of one technology if it persists, particularly if a significant percentage of growers do not comply with insect resistance management strategies. We also acknowledge that use of Bt corn hybrids is widespread because producers want access to high-yielding, elite germplasm, which many growers perceive as unavailable in non-Bt corn hybrids. This seed industry inventory issue inhibits flexibility in pest management decision-making.

Figure 4. Would you plant a Bt hybrid for corn rootworm or European corn borer control knowing that anticipated damage levels were low?

We look forward to another growing season and to receiving your requests for the latest in insect management recommendations. We also offer our thanks to Vernon Stern and his colleagues for their visionary perspectives on insect management.--Mike Gray and Kevin Steffey

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