Click on Titles: Grower Adoption of Grape IPM Disease Management Strategies Implementing GBM Risk Assessment and Leafhopper Scouting in Lake Erie Region Vineyards Exploring Alternative Methods of Implementing ISOMATE-GBM™ in High Risk Vineyards Reexamination of Grape Berry Moth Management Practices in the Lake Erie Region I Reexamination of Grape Berry Moth Management Practices in the Lake Erie Region II Postemergence Vineyard Weed Management Program I Postemergence Vineyard Weed Management Program II Food Quality Protection Act Back to GIPM Home Page Back to Lake Erie Regional Grape Program Home Page

Principle Investigators: T. Weigle, Sr. Area Extension Educator, NYS IPM Program, R. Dunst, Research Support Specialist, NYSAES, Fredonia and J. Bixby, Program Assistant, NYS IPM Program. The authors wish to thank the following growers: Ed Barger and Joel Rammelt of Westfield, NY for providing vineyards, equipment, herbicides and labor toward this project. INTRODUCTION Under the row weed management in Lake Erie vineyards have traditionally relied on the use of a pre-emergence herbicide application in the spring followed by an application of a postemergence herbicide in June (or around grape bloom). Concerns over the potential for ground water contamination through the use of pre-emergence herbicides applied directly to the soil, the persistence of these herbicides in the soil and the need to increase the rates of these herbicides to achieve reliable weed management caused researchers to examine other weed management options. Research conducted by R. Dunst, et al., indicated that two properly timed applications of a broad spectrum, postemergence herbicide (early June and mid-late July) could be as effective as a conventional weed management program using persistent pre-emergence herbicides. In these experiments, the postemergence program selected for low growing winter annuals and managed annual grasses along with annual and perennial broadleaf weeds to an acceptable level.

The goal of this project was to move the results of this research into growers' fields to determine if: 1) it fit into a growers schedule of production practices, 2) was economically feasible, and 3) any persistent weed problems would result from yearly use of a postemergence weed management program.

METHODS

Four vineyard blocks were used in this experiment. Each block contained two treatments: 1) the growers conventional weed management program and 2) the postemergence weed management program. Three of the plots were in Westfield, NY in Chautauqua County, with the fourth located near Lewiston, NY in Niagara County. Each grower was asked to provide at least two rows for the postemergence program with remaining rows in the block to be treated with their conventional weed management program of pre-emergence and postemergence herbicides. Three of the vineyards were selected due to the growers' description of persistent problem weeds. Two vineyards had a problem managing foxtail with their conventional program, one vineyard had persistent velvetleaf, and the vineyard in Niagara county had patchy problem areas of perennial weeds such as field bindweed and poison ivy. Growers were instructed to apply one of the postemergence herbicides (Roundup, Gramoxone, or Rely) when first weeds were 4-6 inches in height. Research conducted by Dunst reported that this typically occurred during the first week in June. A second application was to be made when the weed regrowth reached a height of 4-6-inches, typically in mid-July. All growers involved with this project chose Rely as the herbicide to use in the postemergence blocks.

Weed ratings were conducted in both the conventional and postemergence plots prior to the first postemergent application, three weeks after the first application, and three weeks after the second application. A final evaluation was conducted in mid-September prior to harvest. The assessment involved identification of weed species present and the percent of ground cover each species represented. A total percent ground cover was then determined.

RESULTS & DISCUSSION

The postemergence weed management strategy was successfully implemented in two of the four vineyard blocks in this project. In the remaining two blocks the second application was not applied until early September. The final preharvest evaluation, conducted the week of September 13 - 17, showed nearly 100% ground cover in both blocks. In the first block the primary weed species was foxtail, approximately 12-inches in height, which had been killed by the herbicide application. In the second block there was a wide range of weed species present which had not yet been affected by the September application. Weed height in the second block ranged from the low growing weed species to grasses which were approximately 12-inches in height.

     * Percent ground cover calculated over entire treatment block.

Table 1 shows the results of the preharvest weed evaluation in the two blocks in which the program was fully implemented. In these blocks the postemergence weed management program compared favorably with the traditional pre-emergence herbicide approach. Weed growth covered approximately 27% of the under row herbicide strip with the conventional program in Westfield as compared to 3% weed cover in the postemergence program. Weed management was comparable in both blocks of the Niagara county vineyard with the conventional program having approximately 4 % ground covered with weeds as compared to 3.5% in the postemergence block.

Growers involved with the program were satisfied with the results obtained by using the postemergence herbicide program. The grower in Niagara county was particularly happy with the performance of the postemergence program and the reduction in his weed management costs. Due to a dry period during mid-late summer, regrowth of weeds after the first Rely application in June was delayed. This resulted in season long weed control with just one application. As is the case with most production practices, if the economics don't support the practice, it will not be adopted. Table 2 shows the spray programs, along with costs in the two vineyards which fully implemented the postemergence program.

     * Per acre sprayed

The Niagara costs really show the potential for savings using the postemergence herbicide program in years with summer dry spells which delay weed growth. Not only was the weed management comparable to the conventional program but the cost was almost $4 an acre less in materials alone. Figuring in labor and equipment costs for the second spray needed with the conventional program would increase per acre savings to approximately $11. The Westfield area received ample to excessive rainfall during the summer months and a second postemergence herbicide application was necessary. As shown in Table 2, this increased the cost of materials to over twice that of the conventional program. However, the postemergence program using Rely resulted in only 3% total ground cover under the row from weeds as compared to approximately 27% for the conventional as stated earlier, a reduction in ground cover of approximately 90%.

The failure to fully implement the postemergent herbicide program in two vineyards (second application of Rely was delayed until September) was due more to the small size of the treatment blocks than in the difficulty of implementing the practice. It is felt by the grower involved that an entire block treated with the postemergence program would be more of a priority and would be accomplished in a timely manner. With three- and four-row vineyard plots in the project, the herbicide application became a "when I have the time" priority.

There are several ways to evaluate the use of pesticides in vineyards. One common method is to examine the amount of active ingredient applied for the total pesticide program. The postemergence weed management program greatly reduced the amount of active ingredients applied to vineyards in the project. In the Westfield vineyard examined in Tables 1 & 2 the total amount of active ingredient applied due to herbicide use was over 400% lower with the postemergence program when compared with the growers traditional herbicide program (2.1 lb a.i./acre sprayed vs. 8.2 lbs a.i./acre sprayed). It is important to realize that that the term per acre sprayed is used due to herbicide applications being made only to the herbicide strip under the vine. The total area covered by the herbicide strip, in a particular acre, will vary due to width of the strip and the distance between rows. In general, a grower in the Lake Erie region will cover 2.5 to 3 acres of vineyard before applying herbicide to an area equal to an actual acre of land. The vineyard in Niagara county which used only one application in the postemergence program produced a decrease of approximately 670% with the postemergence weed management program (0.75 lb a.i./acre vs 5.06 lb a.i./acre). One of the newer methods of looking at pesticide is the Environmental Impact Quotient developed by Kovach, et al. (New York's Food and Life Sciences Bulletin Number 139). Unfortunately, Rely is a relatively new material and therefore its EIQ has not been developed at this time.

The first year's results of this program are very encouraging. Not only did we see exceptional weed management using the postemergence program in two of the blocks, there was an example of the cost-saving possibilities of this program in some years. The reduction in the amount of active ingredient applied directly to the soil is also very encouraging. However, with only one years results it is still too early to determine the long-term success of the postemergence program. Growers participating in this project have expressed an interest to continue this project next year. It is hoped that the size of demonstration blocks can be expanded to help reduce any variation in weed stand between treatments.

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