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By Dr. Lois Levitan
USDA ERS Appraisal of IPM Practice on US Cropland
USDA ERS developed a method for rapid appraisal of IPM on US cropland to use as a baseline estimate for monitoring progress toward the 75% IPM goal (Vandeman et al. 1994). Previously-collected data from USDA NASS grower surveys (1991-1993) were analyzed for pesticide use and the extent of IPM practice in the nation. Because pest pressures--and thus the need for specific pest control and prevention measures--differ by crop and with situation-specific conditions such as weather, Vandeman et al. chose two basic practices as the lowest common denominators for defining IPM: (1) scouting for pests and (2) use of economic thresholds in deciding whether to use a pest control treatment. "Scouting" is an IPM term that refers to monitoring pest levels by visual inspection or by trapping. This practice is a key prerequisite for applying economic thresholds. "Economic thresholds" require the justification of each pesticide application (or other pest control treatment) on the basis that the expected resultant increase in crop yield will bring greater economic return than the cost of application. I.e.: Expected economic benefits are greater than economic costs. The threshold is set by professionals (generally researchers in the Cooperative Extension system) who have determined the regionally-, and often temporally-, specific relationship between the numbers of pests found by scouting (following specified protocols and timing) and expected crop damage and yield reduction. The USDA ERS assessment method can only be used, therefore, for crops and conditions where thresholds have been set. This assessment system designates five categories of pest management on US cropland, including three levels of IPM:
Results of this assessment are presented separately for fruits, vegetables and field crops. When summarized they show that in 1993 IPM was practiced on 50% or more of US cropland, for at least one of the three major pest types--insects, diseases or weeds. Further analysis, synthesizing across types of crops and types of pests, indicates that no IPM was used on 35%-60% of US cropland; low-level IPM was used on 5%-15%; medium-level IPM, on 25%-35%; and high-level IPM, on 20%-30% (Hoppin 1996) (Figure 35). This assessment system has been criticized because the classification criteria used for the analysis do not differentiate among the objectives of different IPM practices. Practices for managing pest outbreaks are weighted equally as indicators of IPM adoption with practices that prevent pest outbreaks. A number of the practices listed--especially those for weed control--are essentially methods to increase the cost effectiveness of pesticides, but do not contribute to an integrated pest management that will reduce long-term dependency on pesticides.
