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 has 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 the 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.

In the first year's results of this implementation project were very encouraging with up to a 400% reduction in the amount of herbicide active ingredient applied. Growers participating in the project expressed an interest in continuing the project and expanding the acreage involved.

The goal of this project was to implement the post-emergence weed management program in 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 continued use of a postemergence weed management program.

METHODS

Three 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. Two of the plots were in Ripley, NY with the third located near Westfield, NY (Chautauqua County). Each grower provided at least 10 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. Vineyards were selected based on the growers' description of persistent problem weeds. All vineyards had trouble managing foxtail with their conventional program and one vineyard had persistent velvetleaf problems. Growers were instructed to apply one of the postemergence herbicides (Roundup®, Gramoxone®, or Rely®) when first weeds were 6-8 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 weed regrowth reached a height of 6-8 inches, typically in mid-July. The two vineyard blocks in Ripley received two applications of Gramoxone® in the postemergence blocks. Rely® was used in the post emergence program in the Westfield vineyard.

Weed ratings were conducted in both the conventional and postemergence plots on, or around May 15 (timed to be prior to the first postemergent application) and July 14 (timed to be prior to the second postemergent application). A final evaluation was conducted in late August to assess weed species present for use in the planning of next years program. The assessment involved identification of weed species present and the percent ground cover of each species represented. A total percent ground cover was then determined.

RESULTS & DISCUSSION

The mild winter and early spring made weed management a difficult task during the 1998 growing season. Weeds remained green over the winter and growers found the early flush of weed growth created another job which competed for their time during a hectic spring. The 1998 growing season was the warmest (as determined by accumulated growing degree days or heat units) in the past 35 years. Plant growth, as determined by grape vine phenology, was consistently 3 weeks ahead of a 'normal' year.

---

    * Percent ground cover calculated over entire treatment block.
    ¹ Growers Conventional Program
    ² Post Emergence Program

Table 1 shows the results of the weed evaluations in the Westfield, NY block. In this vineyard, 26 weed species were present when the assessment was completed on any one date. However, only weed species which represented 1% of total ground cover, or more, were included in this table. This is the second successful year of implementing the post emergence weed management program in this vineyard. Of the 78.6% ground cover recorded in the May weed assessment, 50% were low growing winter annuals (bluegrass and chickweed) which have been shown to occur with the successful use of this program. In the August weed assessment, 43% of the ground cover also consisted of low growing winter annuals. This vineyard had persistent velvetleaf problems when it was placed in the program in 1997. Velvetleaf was not found at significant levels during any of the assessment periods during 1998. Applications were timed to take the early season into account. Applications of Rely® were applied as a postemergence treatment at the rate of 4 qts/acre on May 18 and 6 qts/acre on June 20. Velvetleaf was also managed in the growers conventional block with an application of Solicam followed up with an application of Roundup. Solicam is a persistent pre-emergence herbicide which growers consider too costly to use on a yearly basis.

1998 was the first year of implementing the post emergence weed management program in both the vineyards located in Ripley, NY. While the grower participated in the project last year there was the desire to expand the scope of the project so larger blocks were used for the project this year. The early spring and consistently early growing season are reflected in the spray records for both these blocks. Two applications of Gramoxone at the 1 pt/Acre rate were used as the postemergence treatments in both these vineyards. Timing of the applications were a bit late for the 1998 growing season although they would be fairly consistent with the timing necessary in a 'normal' year. Applications were made on June 5 and July 25 which missed the critical stage of weed growth (6-8 inches) called for in the protocol.

---

    * Percent ground cover calculated over entire treatment block.
    ¹ Growers Conventional Program
    ² Post Emergence Program

Table 2 shows the results obtained in one of the Ripley vineyards using a postemergence herbicide with later timings. Results from the two Ripley vineyards were similar in that winter annuals made up a high percentage (up to 90%) of the ground cover during the May assessment but were almost absent from the August assessment. Summer annuals made up the majority of weed species (up to 55%) present in these blocks in August. It is important to note that although the spray timings were delayed this year, weeds did not take over the post emergence blocks. Weed assessments found comparable weed populations, with the exception of the May assessment, between the conventional and postemergence treatments. The difference in weed management between the Ripley and Westfield vineyards is most likely caused by the difference in timing of applications (with the Ripley applications being made later than called for by the protocol) rather than a difference in the effectiveness of the materials.

As is the case with most production practices, if the economics don't support the practice, it will not be adopted. Table 3 shows the spray programs, along with costs in the Westfield and one of the Ripley vineyards. Only one of the Ripley vineyards is shown as both received identical herbicide applications.

---

    * Per acre sprayed

The postemergence program using Rely® is the most expensive program while the Gramoxone® postemergence treatment was the least expensive by far. Additional work is needed to see if the two applications of Gramoxone®, coupled with timing of application at 6-8 inches of weed growth will compare favorably with the Rely® treatments this year. A postemergence program using two applications of Gramoxone® would represent a savings to growers of 61% over the conventional program used in the Ripley vineyards and 68% savings over the conventional program used in the Westfield vineyard. While Rely® is more expensive than either of the conventional programs examined here, it provided excellent management of foxtail and velvetleaf, the problem weeds in the vineyard prior to the implementation of this project.

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, the total amount of active ingredient applied due to herbicide use was 65% lower with the postemergence program when compared with the growers traditional herbicide program (2.5 lbs a.i./acre sprayed vs. 7.0 lbs a.i./acre sprayed). In the Ripley vineyards the postemergence approach resulted in a decrease of 83% pounds of active ingredient per acre sprayed (1.9 lbs vs. 10 lbs). 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 second year's results of this program are still very encouraging. Not only did we see exceptional weed management using the postemergence program in one 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, two years is not enough time to determine any long term effects of a postemergence program. This project will be continued for a minimum of one more year. This would be the third year in the program for the vineyard in Westfield and should give a good indication of any effects this program has in weed management.

You are visitor number