On-Farm Innovation: The Analysis of the PUR Database to Identify Locally-Optimized Ecological Farm Management Practices - Final Report

Disclaimer

This report was prepared by an EPA assistance agreement recipient and represents only the views of the author rather than EPA.

Minghua Zhang^{1, 2} and Rick Miller¹
¹Department of Land, Air and Water Resources, University of California Davis
²Department of Pesticide Regulation, Sacramento, CA
530-752-4953 or 916-324-1256, mhzhang@ucdavis.edu or mzhang@cdpr.ca.gov

Executive Summary

The Pesticide Use Report (PUR) database was used to analyze two commodities, prunes in Sutter and Yuba counties, and winegrapes in Madera, Sonoma, and Napa counties. The project explored the potential for the identification of alternative, low-pesticide farm management practices in these five counties. Several methodologies were developed, tested and improved, with the intent of comparing and contrasting different pesticide management strategies. The results were presented in meetings with commodity boards and growers, where they offered suggestions as to the utility of the pesticide use practice and further refinement of the methods used in this study.

1. Data source and PUR-GIS Application

The data source for analysis was the 1993 through 2000 Pesticide Use Reports, which was compiled by the California Department of Pesticide Regulation. We used an Arcview/Oracle interface program to facilitate pesticide use data queries. Due to the user-friendly interface of the program, the analysis for this study was facilitated, generating results in a time-effective manner. In turn, the data processing experience in this study has also yielded further modifications to improve the PUR program for wide user groups.

2. Geographic level of investigation

Four levels of comparisons were used in the data analysis: county level, with different geographic, political and technical (extension offices); appellations level, with different microclimates and soils; grower management level, in which multiple fields over multiple years reported by one grower can be compared with a similar set of data for another grower; and, at the field level, which is the basic unit used to report PUR data, and contains information of products used, dates and rates of pesticide application. Average use rates on acres planted are calculated by dividing the total pounds of active ingredient used for a particular pesticide by the reported total acres planted that received an application of that pesticide. Based on aggregated values for county and appellation reported pesticide use, fields and growers were classified into four categories: very low use, low use, moderate use, and high use, representing 0-25%, 25-50%, 50-100% and over 100% of county or appellation average use rates based on acres planted, respectively.

Pesticide use in prunes was analyzed to assess county use trends from 1993 to 2000 for Yuba and Sutter counties. The 1999 and 2000 data was then further analyzed for 71 growers in Yuba and 228 growers in Sutter. In Sutter County, prune yield data was obtained for 44 fields managed by six growers with diverse practices, representing the four categories of use. Similarly, in Madera, Sonoma and Napa counties, reported pesticide use on winegrapes was assessed using the county use trends from 1993 to 2001. The winegrape data, encompassing over 1000 growers, was further analyzed for the year 2000 in three counties: Madera with 208 growers, Sonoma with 653 growers and Napa with 242 growers. Sonoma County was further subdivided by appellations, or legally defined winegrape growing regions, which coincide with specific watersheds in the county. The examined specific management practices from the PUR analysis were verified in the field for Napa County.

3. Results

Prunes in Yuba and Sutter counties

Both Yuba and Sutter counties had similar overall average pesticide use rates. No trends in pesticide reduction were found at the county level for the period 1993-2000, but both counties exhibited great variety at the field and grower management level. In the 2000 data of Yuba County for prunes, 74% of fields used no herbicides, 4.5% used no insecticides, and 38% used no fungicides. We found that 11out of the 68 prune growers in Yuba County could be identified as low pesticide use growers where they used less than 50% of the average rate per acre planted. In the 2000 data of Sutter County, 77% of fields used no herbicides, 9% used no insecticides, and 25% used no fungicides. We found that 8% of the 226 growers in Sutter County could be identified as low pesticide use growers.

We presented the analysis to prune growers on June 6, 2002. Typical comments from growers were: “The detailed pesticide use profiles could be used to demonstrate that there are farmers who have successfully managed to use fewer chemicals over time,” and “County trends were useful as references to compare our practices with other growers in the county.” Comments from a farm advisor included: “Outreach programs will be strengthened by including data from the PUR analysis.”

Yield data from selected growers with contrasting pesticide management styles showed that low pesticide use was not an impediment to high yield. Average dried plum yield was 2.4 tons/acre in Sutter County in 2000, yet 7 fields under one grower ID number with no FQPA (Food Quality Protection Act) chemicals yielded 3.1 tons/acre, while 20 fields under another grower, using high rates of diazinon (2 lbs a.i./acre), yielded 3.2 tons/acre.

Wine grapes in Madera, Sonoma and Napa counties

Pesticide use in winegrapes showed use of similar materials in the three counties investigated. Major differences between counties were found in the higher rates of sulfur used in Madera County, and a greater use of soil fumigants in Sonoma County for the installation of new vineyards. Although Napa County and Sonoma County used similar materials, and are in close geographic proximity, Sonoma County treated twice as much acreage with herbicides, three times as much acreage with copper-based fungicides, and four times as much acreage with miticides. Both these counties relied less on sulfur, but more on other fungicides than Madera County.

As a consequence, when a search was made for fields with low pesticide use, Napa County had the highest proportion of low-use acreage. In a comparison where acreage was tallied for fields with no reported insecticide use, and no use of pre-emergent herbicides, 28% of the acreage in Napa, 16% in Sonoma, and 11% in Madera fell into this category. On an aggregate level, these low-use fields also reported lower than average rates of sulfur application for fungal control.

These differences in pesticide use rates can be attributed to at least three clearly documented trends by the growers identified as low users:

Lower use rates made possible by technological advances, such as electrostatic sprayers, which apply all products more efficiently, or ultra-low volume under-vine herbicide application equipment, which allows more flexibility in choice of herbicide timing and product used.
Intentional avoidance of problem pesticides, by planning and experimentation with low-impact materials, such as the use of cinnamaldehyde in the place of propargite, to avoid posting warnings on tourist roads in Napa Valley
Adoption of ecological management practices which can directly, or indirectly, maintain fields’ sanitation and reduce pest problems, making pesticide use less necessary.

Often, interactions between all three scenarios exist on properties of growers who have successfully demonstrated pesticide reduction. Fields which have no insecticide application have lower than average sulfur use, a correlation that pest control advisors have identified as being the result of greater number of beneficial insects found in vineyards with less use of sulfur dust. Other interactions are more complex and difficult to interpret. Active programs for promoting barn owl populations are common in areas that have reduced use of pre-emergent herbicides. By first establishing biological control of gophers, growers were able to experiment with less herbicides and more vegetative cover in vine rows.

Introduction

There is a tremendous diversity of farm management practices across commodities, geographic regions, and among growers, particularly in terms of pesticide use. There are numerous explanations for the wide variations in the quantity and quality of pesticides used among growers, including weather, pest pressures, economic situations, soil types, and irrigation, among others. The purpose of this study is to determine if the variation in California pesticide use can also be attributed to differences in management strategies that are based on an applied understanding of local conditions. This study utilizes California’s Pesticide Use Report (PUR) database, which provides a new way of identifying low pesticide use systems.

Background

Up to now, California’s Pesticide Use Report (PUR) database has been used primarily to monitor statewide and county trends in chemical use. Because of the detailed nature of the reporting system, PUR offers a unique opportunity to investigate pesticide use at the grower and field levels. By examining the database with a field-level resolution, low pesticide use growers can be identified. However, due to the complex and local nature of farming systems, farmers should be involved in evaluating the PUR information in order to ensure correct interpretation of the data. With farmer insight, low-use reference systems can be applicable to other growers interested in reducing pesticide use.

Objectives

The objectives of the study were to assess county trend of pesticide use, to examine the variations in pesticide use among growers in a given commodity and county, both within years and across multiple years, and then to identify low pesticide use. Data analysis results were then shared with growers to evaluate and interpret the pesticide application variations. The goal of this process was to strengthen farmer exchanges of locally-adapted pesticide use information based on communities of growers with similar conditions, but differing rates of pesticide use. Specific tasks included examining and identifying variations in rates of use by fields and by chemicals.

Participants or collaborators

The project team was comprised of researchers at the Agricultural Geographic Information Systems Laboratory (AGIS Lab) and four collaborating partners. The project collaborators were the California Prune Board, the California Association of Winegrapes Growers, the California Alliance with Family Farmers (CAFF), and The Nature Conservancy. The collaborators were a unique and important aspect of the investigation, helping AGIS Lab researchers define the parameters of analysis and the criteria for selecting low-use pesticide practices. Their insight into grower management strategies, alternative production systems, and the complex economic, agronomic, and social variables affecting growers in their respective commodities helped the researchers design the project with growers’ needs in mind.

Materials and Methods

The data source for the study was the Pesticide Use Reports (PUR) from 1993 to 2000 (CDPR, 2000). Although PUR data sets are available beginning in 1990, there are concerns about the accuracy and quality of the records from 1991 and 1992, thus only the data from later years were used. The study sites for prunes were Yuba and Sutter counties, while the study sites for winegrapes were Madera, Sonoma and Napa counties. GIS programming was used to sort and query the PUR database by county, commodity, and year, and to obtain detailed summaries of chemical, product, and field pesticide use. Simple statistics were used to analyze rates and intensity of pesticide use. Pesticide use was measured by pounds of Active Ingredients (AI) and the intensity of pesticide use was measured by pounds of AI per acre planted.

The data was organized according to overall county trends, variation in the use of selected chemicals, and detailed summaries of field and farm applications.

County trends were used to identify variation in the types of chemicals used and within chemical types. Pesticide use categories were used to identify variation in the intensity of use within selected chemicals and by fields. Chemicals were selected for investigation according to degree of use and in conjunction with collaborating commodity organizations. The use categories formed the foundation for identifying low pesticide use fields and growers.

For prunes, fungicides and insecticides were selected for intensive study because they were the most heavily and frequently used chemical types in prunes (by pounds of AI) over the eight-year period under investigation. Insecticides were separated into dormant and in-season use categories as a result of differences in risk exposure and regulations on use associated with the rainy versus the dry season. The dormant period was defined as December 10 of the previous year through February 28 of next year, while in-season was defined as March 1 through September 30, as suggested by our collaborator from Dried Plum Board. Four groups of insecticides were examined: oils, organophosphates (OP’s), pyrethroids, and BT. Insecticides such as carbamates were not isolated for investigation because their use was minor relative to other insecticides. The total number of fungicide AIs used was small, so the research examined each one of them: sulfur, copper, captan, iprodione, and chlorothalonil, propiconazole, and cyprodinil. These fungicides were assessed using the data from year round (January 1 through December 31).

Total winegrape acreage Madera, Sonoma, and Napa Counties was examined to find fields that grouped into categories that had no application of certain herbicides, insecticides, and fungicides, specifically those restricted under FQPA guidelines. These categories were developed to find rapid and efficient methods of screening a large database for examples of low-pesticide use fields.

Pesticide use in individual fields was categorized relative to the county average of pounds of chemicals applied per acre planted (lb/acre planted) of the selected chemicals. Four pesticide use categories were created, as explained in Chart 1. The pesticide use categories provided a quick reference point for comparing pesticide use intensity.

Chart1: Pesticide Use Categories

Pesticide Use Category	% of county average of lb a.i./acre planted
Very-Low Use	0-25%
Low Use	25-50%
Moderate Use	50-100%
High Use	Over 100%

Fields were chosen as the initial unit of measurement and then aggregated up to the grower level. Low-use fields were identified and compared with a grower’s total reported fields. Growers demonstrating patterns of low use on all or most of their fields were tracked back to 1998 to determine if use was consistently low or decreasing from 1998.

The criteria used to define low pesticide use were:

Low number of active ingredients used
Low toxicity of chemicals used as defined by the EPA FQPA list and known groundwater contaminants
Low use of fungicides and insecticides for prunes, low use of herbicide for winegrapes
Low number of applications by chemical
Low lb/acre planted of the chemicals used, or intensity of use
Low percent of acres treated, or spot treatments
Low or decreasing rates of chemical use from 1998 to 2000.

Initially, these categories pertained to the aggregate of active ingredients applied during a calendar year to each field. Some pesticides use rates are higher than the other. For example, bulkier products such as sulfur and dormant oils are applied at higher rates where thus weighed more heavily when they were aggregated with other active ingredients applied at lower use rates. Therefore, the methodology was then refined to use these categories to compare individual chemical application rates, and only among fields on which these specific chemicals had been applied.

Due to the complicated management strategies and reasoning behind each decision made during the analysis process, explanations for the variations in pesticide use cannot be ascertained from the database alone. Therefore, the results must be reviewed and interpreted by growers in order to gain a better understanding of the pesticide use profiles. One important methodology of this project is to communicate with our collaborators and growers about the research results, then use their comments to direct the research process to help ensure that the data is applicable for farmer exchanges of information and education.

Project Activities

Four planning and feedback meetings among collaborator team members were held, in October 2001, December 2001, March 2002, and June 2002. In addition, bi-weekly or monthly individual participant briefings and discussions were held during the project time.
The prune analyses results for Yuba and Sutter were presented three times: in April 2002 to the Prune Board and their management team, June 2002 to the prune growers, and July 2002 to the Central Regional Water Quality Control Board.
Results from the prune PUR analysis were published in CAFF Lighthouse Newsletter; winegrapes results are currently in progress for publication as well.
The analyses results on the winegrapes were presented and discussed with the pest management project members in California Associations of Winegrape Growers in Napa during November of 2002, and some growers in Hudson Vineyards in Napa during February 2003.
Information dissemination to local communities and regional organizations–local and state farming groups and regulatory agencies were informed through phone conversations regarding the project.
Research–data analysis and joint information gathering with collaborators to interpret the results and planning field day meetings.
A paper is being prepared for publication to document the importance of growers’ involvement in research project. Another potential paper will be prepared for publication to report the findings of the PUR analyses.

Results

1. Prunes

The pesticide use trends over time, for both counties and individual growers demonstrate the intent of many growers to move away from some specific chemicals towards use of safer alternatives. This change is in part facilitated by the Dried Plum Advisory Board, and in part by environmental awareness of chemicals such as diazinon, frequently found at high concentrations in the water of the Sacramento River, and/or methyl bromide, a known problematic pesticide of stratospheric ozone. Further investigation at the grower level found cases of growers who had implemented ecological management strategies, which is differentiated from the substitution patterns by simply precluding the need for insecticides and herbicides.

1.1 Pesticide use trends from 1993-2000

In Yuba County, the total pounds of AI did not change significantly from 1993 to 2000. The total acres planted increased 5% while the number of applications decreased 18%. In Sutter County, the total pounds of AI used also did not change dramatically from 1993-2000. The total acres planted increased 6% and the number of applications increased 17%.

In Sutter County, oil was the most heavily used AI from 1993-2000. In 2000, oils were 38% of all chemicals used. Dormant oil use showed increase from 1993 to 1996 and then decreased, while in-season oil use showed a slightly increase but fluctuated as well. Sulfur, methyl bromide (replaced in 1999 by 1-3 dichloropropene), copper, and captan were consistently in the top five most heavily used chemicals while diazinon, methidathion, chlorothalonil, iprodione, and glyphosate closely followed (Figure 4, 5). During both the dormant and growing season, oils were the most heavily used AI, followed by OP’s, and pyrethoids (Figure 1, 2, 3). Total county use of dormant pyrethroids increased from 17.1 lbs. in 1993 to 370.63 lbs. in 2000, with a similarly dramatic increase of in-season use (Figure 3) at the same time as BT use increased. From 1993 to 2000, sulfur use increased 6% while captan use decreased 13%. Some substitution did occur between OP’s and pyrethroid products, and an increase in BT use was observed.

In general, there were no pesticide reduction trends on a county level, which complements the PUR information reported by Epstein and Bassien (2002) for the years 1992-1998.

1.2 Identification of fields and growers with low pesticide use

In contrast to county trends, analysis of data aggregated by field and grower code demonstrated evidence of pesticide use reduction trends, as well as substitution trends. In 2000, 74% of Yuba prune fields used no herbicides, 4.5% used no insecticides, and 38% used no fungicides. Using three years of PUR database for analysis, 16% of growers were identified as low-use from 1998-2000. Table 1 displays the low to high use categories for the pesticides of interest in 2000. Most growers used pesticides at more than 50% of county average use rates, so they were classified into the moderate and high use categories. However, five fields out of a total of 68 were found to use the OP and pyrethroids at low rates during dormant seasons, and four fields were found to use low rates of sulfur during in-season. It was interesting to note that the no pesticide use fields were at a high percent across all the pesticide use types.

In 2000, 77% of Sutter prune fields used no herbicides, 9% used no insecticides, and 25% used no fungicides. We identified 8% of growers as low-use from 1998-2000. Pesticide use by growers in both counties was analyzed to identify examples of reduction in chemical use, substitution of products, and ecological management that precludes the use of chemical products. Table 2 displays the low to high use categories for the pesticides of interest for 2000. Similar patterns of use categories were observed in Sutter County. However, Sutter County has slightly different strategies than Yuba County in pesticide use. For example, oils were mostly used in the dormant season with declining trend after 1995. Higher percent of fields were treated with pyrethroids than with OP indicating a potential replacement of OP by pyrethroids. Higher percent of pesticides were used in dormant season overall perhaps signifying either the higher pest pressure and/or the different approaches to control pests. Higher use of sulfur, copper and captan was found in Sutter County than in Yuba County. The no use of pesticide fields, the fields applying no pesticides, could also be seen across all the pesticide use types.

Yuba growers were profiled for low or decreasing use of pyrethroids, OP’s, sulfur, copper, captan, propiconazole, cyprodinil, and iprodione. Examples of some successful growers who practiced reduction of chemical use, substitution of products and ecological management are given as follows. One grower applied oil and esfenvalerate once each on 40% of the field in 2000. This grower demonstrated a consistent trend of oil/esfenvalerate use over the three-year period, with iprodione and adjuvant use in 1999. Another grower showed a transition from diazinon, sulfur, and propiconazole in 1998, to diazinon, sulfur, and chlorothalonil in 1999, to sulfur and esfenvalerate in 2000. Another grower had consistently low intensity fungicide use from 1998 to 2000. This grower used oil and esfenvalerate in 1998 and 1999, and no insecticides in 2000. Fungicides were only applied on 2/3 of the field each year.

Another grower had very low applications of OP’s over the three -year periods. Copper, methidathion, and oil were applied once on 1/3 of the field in 1998. In 1999, methidathion and oil were applied once on 30% of the field. And in 2000, diazinon and oil were applied once on 20% of the field. The third grower used only iprodione in one application in both 1999 and 2000, and demonstrated a similar pesticide use pattern as the second grower in Sutter County. The fourth grower, with over 1,000 acres planted, used propiconazole, oil, and esfenvalerate on 2/3 of the fields, and oil and esfenvalerate on 1/3 of the fields. A similar use pattern existed in 1999 in which propiconazole, oil, and esfevalerate were applied once on 1/3 to 2/3 of each field. This grower’s pesticide use in 1998 was comparable to 1999, with the addition of diazinon applied once on half of each field. These examples of low pesticide use differ dramatically from the profile of a moderate to high use grower. One such grower used 11 AI’s, including captan, diazinon, iprodione, oryzalin, and oxyflourfen with multiple applications of each AI.

Sutter growers were profiled for low or decreasing use of BT, pyrethroids, sulfur, captan, propiconazole, cyprodinil, iprodione, and chlorothalonil. One grower used only iprodione in both 1999 and 2000, and used iprodione and esfenvalerate in 1998. Another grower with 8 fields used a combination of sulfur, oil, BT, and some herbicides over the three years. The third grower applied captan once on 1/3 of the field, and herbicides on half of the field in 2000. In 1999, captan was applied once on the entire field, in addition to several applications of herbicide. In 1998, captan was applied on 1/3 of the field with one application of glyphosate. The fourth grower transitioned from diazinon, sulfur, and propiconazole in 1998 to BT, oil, and copper in 1999, to BT alone in 2000. The fifth grower used only propiconazole in 1999 and 2000, after using propiconazole, diazinon, and sulfur in 1998. The sixth grower with three fields used diazinon, sulfur, and propiconazole in 1998 and 1999. In 2000, the same grower used oil and esfenvalerate only. In contrast, one moderate to high-use grower applied 13 AI’s, including captan, iprodione, diazinon, fenbutatin-oxide, oryzalin, and paraquat. Table 3 provides an example of how the detailed analysis on the user profiles was conducted.

1.3 Meetings with growers and cooperators

Grower meeting feedback about the research was positive. Comments include “the results were helpful in demonstrating the variations that exist in pesticide use; we might be able to use the data to contact growers about sharing their management strategies at field days; the detailed pesticide use profiles could be used to demonstrate that there are farmers who have managed to successfully use fewer chemicals over time.” Comments from a farmer advisor and Dried Plum Board were “Outreach programs will be strengthened by including data from the PUR analysis”; “County trend of pesticide use is helpful for us to monitor the use changes of alternative pesticides”.

It was acknowledged by the growers, regulators and scientists that it is difficult to determine if the profiled growers are viable models without corroborating economic and agronomic factors. One grower did suggest that by tracing the use history and showing consistently low or decreasing rates of use, some degree of economically-sensible management has already been demonstrated. The next step will be comparing the PUR data with information on annual yield, orchard age, pest pressure, % damage, climatic factors, prune prices, and cost per acre to confirm that these practices are viable examples of low-use. Although we had collected some yield data for our interpretation of the PUR analyses, the data was limited to some extent due to a small samples size. A brief report about the yield is presented in the next section.

1.4 Yield data of selected growers

Yield data from growers selected with contrasting pesticide management styles showed that low pesticide use was not an impediment to high yield. This statement was exemplified by the grower who had 7 fields and used no FQPA chemicals and yielded 3.1 tons/acre when the average dried prune yield was 2.4 tons/acre in Sutter County in 2000. Another grower had 20 fields and used high rates of diazinon (2 lb a.i./acre), yielded 3.2 tons/acre. Since we did not have farm pest management costs for pesticide use and other relevant farm management to reduce pesticide use, it is difficult to conclude whether the reduced use of pesticides is economically profitable regarding net income return. However, the yield data provided us with the certainty that the reduced use of pesticide can potentially be economically viable in production while the environmental impacts can be reduced.

2. For winegrapes

Pesticide use in winegrapes showed use of similar materials in the three counties investigated. Major differences between counties were found in the higher rates and the total amount of sulfur and insecticides used in Madera County, and a greater use of soil fumigants in Sonoma County for the installation of new vineyards. Although Napa County and Sonoma County used similar materials, and are in close geographic proximity, twice as much acreage in Sonoma County is treated with herbicides, three times as much acreage is treated with copper-based fungicides, and four times as much acreage is treated with miticides. Both these two counties rely less on sulfur, but more on other fungicides than Madera County.

2.1 Pesticide use trends from 1993 to 2001

In Madera County, the total amount of AI continuously decreased from 5 million pounds in 1993 to 3.3 million pounds in 2001 except for in 1998 when the use was the highest at 5.3 million pounds (Figure 6). The total acres planted increased 12% from 1993 to 2000 and the total number of applications showed no significant changes during this period. Sulfur was the dominant pesticide used in the county followed by insecticides and herbicides, 4.3 millions lbs in 1993 to 3 millions lbs in 2001 (Figure 7). However, insecticide use decreased and herbicide use increased from 1993 to 2001. Fungicides except sulfur fluctuated in their use during the period. Fumigants had the highest use in 1998, while other year’s fumigant use varied only slightly

In Sonoma County, the total pounds of AI decreased 31%, from 3.6 millions lbs in 1993 to 2.5 millions lbs in 2001 (Figure 6). The total acres planted increased 34% from 1993 to 2000 and the number of applications increased 46% from 1993 to 2001. Among the total pesticides used, highest proportions were fungicides (more than 85% of total), then fumigants, herbicides and insecticides. Furthermore, while sulfur was consistently more than 70~85% of all the fungicides used, sulfur also showed a declining trend from ~3.2 million lbs in 1993 to over 2 million lbs in 2001, a 38% decrease (Figure 8). Fumigants also showed a declining trend of use while herbicide use increased from 1993 to 2000 and then decreased in 2001. Insecticide use increased slightly over the time period of eight years.

In Napa County, the total pounds of AI decreased from 3.8 millions lbs in 1993 to 2.1 millions lbs in 2001, a 45% decrease (Figure 6). The total acres planted remained almost constant from 1993 to 2000. The total number of applications increased 12% during the period. The amount of sulfur steadily decreased from ~3.3 million lbs in 1993 to 1.7 million lbs in 2001, a 48% decrease. However, the other fungicides except sulfur significantly increased their use from 1993 to 2001 (Figure 9). Fumigants decreased the use. Herbicide use fluctuated over the time. Insecticides use increased slightly. The reduction of sulfur use in Napa was the main contributor to the decreased overall trend in the county.

2.2 Pesticide use at appellations level in Sonoma County

Table 4 displays the differences between the seven appellations in Sonoma County. These seven appellations include Carneros, Sonoma, Russian River, Chalk Valley, Dry Creek, Alexander Valley, and Knights Valley. For most of the chemicals, these appellations had similar average use rates. However for some chemicals such as sulfur, lime sulfur, copper oxychloride sulfate, glyphosate, and simazine, average use rates greatly varied among the seven appellations. For sulfur, the Carneros appellation had the largest average use rates, 72 lbs per acre planted, while Knights Valley had the lowest use rates, 28 lbs per acre planted (Table 4). The Sonoma appellation had the highest use of copper oxychloride sulfate while Carneros had high average use rates for glyphosate and simazine, 1.48 and 1.31 lbs per acre planted respectively. Overall observations for chemical use showed Knights Valley with the least amount of pesticide useage. The differences among appellations may be due to local weather conditions and pest pressures. Details of the local climate impacts on pesticide use are being explored in the current FQPA-funded pesticide use analysis project.

2.3 Comparisons of low pesticide use at field and grower levels

As a consequence, when a search was made for fields with low pesticide use, Napa County had the highest proportion of low-use acreage (Figure 10). In a comparison where acreage was tallied for fields with no reported insecticide use, and no use of pre-emergent herbicides, 28% of the acreage in Napa, 16% in Sonoma, and 11% in Madera fell into this category (Figure 10). On an aggregate level, these low-use fields also reported lower than average rates of sulfur application for fungal control. This level of study is also being carried out in the current FQPA pesticide use analysis project.

2.4 Meeting with growers and communicating with county farmer advisors

The presentation to share the PUR analysis results in a field day in Napa November of 2002 was well received by the growers, scientists from California Department of Pesticide Regulations, US EPA region 9, and coordinators of pest management project in California Association of Winegrape Growers (CAWG). The comments include “This is a wonderful project to utilize the PUR analysis results for outreach activities”; “The information from the PUR can actually be useful to growers as demonstrated by this project”. Some information from the project was actually used by the coordinator of pest management project in CAWG for outreach activities.

A group of researchers at the AGIS lab also went to visit Hudson Vineyards in February 2003 to share the PUR analysis with a few growers. The group met with Lee Hudson, Jason Kesner from Hudson Vineyards and Jill Klein, an Association of Applied IPM Entomologists. We presented a summary of PUR data for three growers during 1999-2001 in the Carneros District. A line-by-line summary for 1999-2001 in Hudson Vineyards pesticide applications, and a line-by-line report of pesticide applications for a very low pesticide use grower from the Carneros area were presented to Hudson Vineyard. With the exchange of information, Hudson Vineyards presented a floor management transition plan for 2000-2002 (Table 5). Growers were receptive to the “very low use” information and were curious about how other people manage to use less than they did.

By communicating with a farmer advisor in Sonoma County, we found out that farmer advisors are equally curious about the PUR analysis and are interested in learning how each county is doing in pest management and pesticide applications. Comments from farmer advisors were “PUR analysis is so valuable to farmer advisors for outreach activities” and “I am curious how the IPM innovators are doing in their pesticide applications”.

Discussion

The similar county trends of pesticide use in Sutter and Yuba for prunes indicated that the pest types and pest management approaches might be similar in these two counties for growing prunes. However, the county use trend of pesticide use in winegrapes showed the different patterns among the three counties, Madera, Sonoma and Napa. These differences may be due to the differences in climate and environmental pest stresses. Heavier use of insecticides in Madera may mean a higher presence of insects in this county or it may reflect a county accepted strategy of applying more insecticides in pest management. The occurrence of heavier sulfur use with heavier insecticides use in Madera may relate to the association of heavier sulfur use with higher amount of insecticide use as suggested by county farmer advisors and growers in one of our field days.

Although the county trends of pesticide use are helpful to examine the increase or decrease of use over time, and they can be used for comparisons between counties, the grower and field level analyses are more helpful in identifying low use and successful pest management strategies. The more detailed field-level information would also allow us to explain some of the use trends by chemical transition and replacement, and by local ecological knowledge in pest management. The detail field level information also allows us to identify the outliers and any possible data quality issues.

The differences in pesticide use rates can be attributed to at least three clearly documented trends by the growers identified as low users: first, technological advances allow more flexibility in choices of herbicide product used and application timing; secondly, some growers intentionally try to avoid problematic pesticides, by careful planning and experimentation with low-impact materials; thirdly, some advanced growers adopted ecological management practices which can then directly, or indirectly, help maintain a sanitary field and reduce pest problems, hence making pesticide use unnecessary. Visits to prunes and winegrapes fields confirmed our explanations for the reduction of pesticide use.

The technology, i.e., electrostatic sprayers, has the functions of adjusting the application rates and spray nozzle sizes during the field applications of pesticides. This equipment applies all products more efficiently at low volume in vineyards to reduce pesticide offsite runoff or drift. In the past few years, many government supported research and demonstration projects may have influenced growers to see the benefits of pesticides use reduction. It is possible that tight regulation on certain pesticides also played an important role in reducing use of pesticide among the grower community. Although the technology applications and the pressures from the regulations can help reduce the use of pesticide, it is more important to adopt ecological management practices which can lead to long term benefit to the environment and to sustainable agriculture.

The interactions of the listed three possible trends in reducing use of pesticides were also observed on the properties of growers who have successfully demonstrated pesticide reduction. It was also interesting to find out from the PUR analysis that fields, that received no insecticide treatment, used less sulfur than average. A complete understanding of the association between insecticide and sulfur use reductions is not clear at the present time. However, growers confirmed the association during our field trips. The reduction of herbicides seemed to associate with the barn owl population. The herbicide use reduction and cover crop promotion in vineyards often increase gopher density that can damage the vines to reduce production. In order to encourage reduction of herbicides and increase use of cover crops, controlling gopher was the immediate need. Barn owl is the natural enemy of gopher. Each owl can eat more than 200 gophers each season. Therefore, active programs for promoting barn owl populations are common in areas that have reduced use of pre-emergent herbicides. With the biological control of gophers, growers can then experiment with less herbicides and more vegetative cover in the vineyards.

Because agriculture is a complex system, some other explanations for the reduction of pesticide use can also be possible. As we continue to explore the research in this area, we expect to learn more about the ecological connections of reducing pesticide use on farms using improved pest management strategies.

Conclusion

The PUR database can be an effective tool for identifying low-use growers. Low-use criteria must be flexible and adapted to the unique conditions of individual commodities and counties. Selecting chemicals of research and outreach interest is helpful for defining low-use criteria and should be done in partnership with commodity representatives for usefulness and accuracy. Detailed grower profiles are effective tools for describing pesticide practices, but are most effective when accompanied by economic and agronomic data such as annual yield, cost/acre, orchard age, and other field-specific facts. Working with the collaborators is a key to understanding pesticide use trends. There is potential for using the profiles to contact growers for farmer-to-farmer exchanges of information or to be used as references for alternative pesticide management strategies. This research offers an exciting new way of looking at the Pesticide Use Reports by bringing the PUR database back to farmers.

Acknowledgement

We wish to thank the PESP program of the US EPA Region 9 for the financial support in this study. We thank all the collaborators for their contributions and the growers who allow us to visit their fields. We also thank Emily Oakley, Jennifer Campos, Zhihao Qin and Ye Chen for their hard work on this project.

References

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