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AG-IMPACT Email Discussion Group
Decision Tool for Integrated Pesticide Selection and Management in Minnesota Corn and Soybean Production


AG-IMPACT Email Discussion Group
The Ag-Impact Internet discussion group is an international forum for discussing issues, problems, and progress in developing methods for assessing the environmental impacts of agriculture. We hope the discussion will be useful and interesting to the growing body of researchers and practitioners working to develop and apply environmental impact assessment tools.

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Institute for Agriculture and Trade Policy Environment and Agriculture Program
TECHNICAL PROJECT DESCRIPTION

Decision Tool for Integrated Pesticide Selection and Management in Minnesota Corn and Soybean Production

INTRODUCTION
The objective of this project is to facilitate the adoption of environmental impact assessment in the selection and management of pesticides in row crop production. The approach is to integrate environmental criteria with other, non-environmental decision factors. Non-environmental factors include production cost, persistence (carry over) ratings, and resistance risk ratings. The environmental focus is ground and surface water protection. The project area for 1998 is the Minnesota River Basin in southern Minnesota, a major corn and soybean producing area. Herbicides are the primary pesticide inputs.

WINDOWS PESTICIDE SCREENING PROCEDURE
The central component of the Decision Tool is the USDA Natural Resource Conservation Service's (NRCS) Windows Pesticide Screening Tool (WinPST) 1. In the first step of WinPST, the user looks up ratings for the active ingredients in the pesticide(s) selected. Then, using a different table, the user finds an equivalent set of ratings for the soil type (map unit) of the field(s) where the pesticide will be applied. The ratings are in the form of qualitative categories, representing the relative likelihood that a pesticide will leave the site of application via runoff or move down through the soil below the root zone. Three modes of water contamination are considered: groundwater contamination via leaching; surface water contamination via dissolved pesticides and via pesticides adsorbed to soil particles. For both soil type and pesticide active ingredient, there are three possible rating classes - "high," "intermediate," and "low" - for each mode of contamination (plus a "very low" class for leaching). These ratings are primarily based on physico-chemical properties. Combining the two ratings in a matrix table, results in an overall interaction rating for the potential for contamination to occur: "Potential I" (large), "Potential 2" (medium), and "Potential 3" (small; and for leaching, "Potential 4," very small). A rule-based protocol is used to adjust the ratings so that the procedure is responsive to the effects of case specific conditions such as the method of pesticide application, the depth to the water table, field slope, and the probability of rainfall. The ratings can be adjusted in each of the three steps of the procedure-pesticide, soil, and interaction. The maximum adjustment is limited to one class in each step.

DECISION TOOL FOR INTEGRATED PESTICIDE SELECTION AND MANAGEMENT
The Decision Tool is a set of documents designed to accompany the introduction of WinPST in hard copy form, as well as provide supplementary information.

(* - currently available)

The Reference Tables are described below.

REFERENCE TABLES
The following is a general description of the reference tables. There are separate sets of tables for corn and soybeans. Each crop-specific table has separate sections for the different pest classes (insects, weeds, etc.). The weed section has separate subsections for the use category (i.e., the timing of application: no-till, pre-plant, pre-emergence, post-emergence). In each subsection, the first column contains the pesticides, listed in groups (adjacent rows) according to their mode of action. Within these groups, they are listed alphabetically by active ingredient. Major brand names and general target groups (broadleafs, grasses, perennials) are given in the second and third columns. From left to right, the other columns are: rate range (lb. a.i./acre), price range ($/acre broadcast), the three unadjusted pesticide ratings, and sections for toxicity, persistence, and resistance management.

The toxicity section has ratings for effects on nontarget groups. The current software version contains two toxicity databases for long-term exposure, one for humans (via drinking water, based on the Maximum Contaminant Level) and another for fish (calculated Maximum Acceptable Toxicant Concentration). The Reference Tables present the toxicity information in the form of qualitative ratings (low, intermediate, high) based on provisional NRCS criteria. Although, the focus of WinPST is water contamination, there are other environmental concerns that should not be neglected. However, risks to nontarget groups such as soil organisms, terrestrial vertebrates, native plants, and beneficial insects are relatively difficult to evaluate in a formal or standardized way because of serious data gaps and/or the lack of satisfactory and practical measures of exposure. Rather than ignore these risks entirely, future versions of the Reference Tables will include additional qualitative ratings. We are also investigating the use of multicomponent indices, rather than single component ratings. For example, measures of acute and/or chronic toxicity to fish and various aquatic invertebrate groups can be combined to produce a single index value for aquatic organisms. There are a number of general approaches to doing this, including the use of: an algebraic equation or algorithm, a rule-based system (e.g., decision tree), and an expert consensus evaluation process.

For the "carry over" (persistence) column, we have adopted a three-category rating system (from north Dakota State Univ. Extension) for likelihood of crop injury twelve months after application (N = never, S = seldom, 0 = often). Under resistance management, there are three subcolumns: mode of action, risk rating, and "recent use?" Mode of action is given as an abbreviation such as CMD for cell membrane disrupters and GR for growth regulators. The second subcolumn has a qualitative, relative risk rating (low, medium, high) for likelihood for resistance to develop (from Univ. of Wisconsin-Extension). The next-to-last column has the query, "recent use?" Here the user should ask, "Have I used a material with the same mode of action in the same field in the last two years?" (The question should be adjusted somewhat for different pest classes.)

The Reference Tables as described here, are available for herbicides used in corn and soybean production. A single, simplified table for insecticides is also available.

ORGANIZATIONAL BACKGROUND
The Institute for Agriculture and Trade Policy (IATP) was founded in 1986 by agricultural and environmental leadership who recognized the need for an independent, nonprofit research organization dedicated to finding and promoting economically, environmentally, and socially sustainable solutions to the challenges acing farmers and rural communities. IATP's work includes research, outreach, and policy analysis on issues concerning national agriculture policy, food safety, international trade, food security, biodiversity, and biotechnology. The Environment and Agriculture Program does research, development, and/or outreach in many areas including on-farm environmental assessment tools, farmer-led watershed protection, incentives for environmental protection in agriculture, and sustainable forestry certification. The program is staffed by Kathryn Gilje, Phil Guillery, Jackie Hunt-Christensen, Mark Muller, John Vickery, and Bill Vorley. IATP has an annual budget of $1,500,000 and a staff of 27. For more information about IATP and the Environment and Program, see http://www.iatp.org OR contact Bill Vorley, Director at 612-870-3436 or bvorley@iat.org.

FOR MORE INFORMATION about pesticide environmental impact assessment or the pesticide Decision Tool, contact:

John Vickery, Environment and Agriculture, Institute for Agriculture and Trade Policy
2105 1st Ave., S., Minneapolis, MN 55404-2505
612-870-3430; FAX -4846
jvickery@iatp.org
www.iatp.org/iatp

IATP's pesticide environmental impact assessment work is funded by grants from the Great Lakes Protection Fund, the Joyce Foundation, and the Minnesota Office of Environmental Assistance.

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1 also known as the Soil-Pesticide Interaction Screening Procedure II (SPISP II). Back to text.