Innovative methods of weed management for Long Island vineyards

Innovative methods of weed management for Long Island vineyards

Summary

Control of vegetation in the strip under the trellis is a standard practice in the management of vineyards in the northeast. The goal is to minimize competition at key vine phonological stages. Excessive weed growth can impair fruit quality and quantity. Typically, weed control in this area is achieved through the use of herbicides. The potential for infiltration of herbicides into groundwater has motivated growers to seek alternate methods for managing weed growth. Cultivation has gained favor though it has distinct disadvantages in a perennial cropping system. We evaluated two less common methods of managing the area under the trellis. In one vineyard, we established two sets of plots examining the impacts of repeated mowing of vegetation under the trellis. Treatments include mowing alone and mowing in combination with glyphosate applications. Weed counts, vine nutrient status and harvest (yield and fruit quality) data will help judge the long term feasibility of this management technique. At the Cornell research vineyard and in two commercial vineyards, a mixture of winter annual weeds such as knawel, red sandspurry and perennial clover was seeded in replicated plots in fall, 2006. These groundcovers ideally minimize invasion of weeds while remaining minimally competitive with vines during the growing season. Our goal has been to determine the feasibility of these alternative methods for management of under trellis vegetation. The impacts of these strategies on vine productivity and fruit quality must also be quantified. It is important to ensure that these methods maintain or enhance vine health and productivity.

Objectives/Performance Targets

Under trellis mowing: Our goal is to ensure that the long term maintenance of weed cover under the trellis will not be detrimental to vines. If the mowing treatment turns out to be harmful, we are hopeful that minimal use of glyphosate will mitigate competition at key stages of grapevine growth and development.

We’ve encountered obstacles in this research. The plots were located at a commercial vineyard that had expressed strong interest and had a custom mowing unit constructed (a mower unit on a swing away arm mounted on a deck mower). We had plots in two locations on this farm. On one site, deer depredation of plots severely compromised results. The second site was on a slight hill with sandy soil. This led to low weed pressure even in untreated plots in both 2006 and 2007. For various reasons, fruit integrity at harvest likely also compromised the relevance of berry samples. Overall, there was too much statistical noise in the data. With the agreement of the grower, we chose to terminate this phase of the project.

Our subsequent plans are still in formation. We are expecting funds from Cornell University to purchase an Edwards under trellis mowing unit. We worked with a local equipment dealer this summer who secured a unit for demonstration in a local vineyard. We have also spoken with a progressive grower in Massachusetts who has this unit. We are hopeful the funds will become available so that we could purchase the unit in time for the 2008 season. We would then establish new plots at the LIHREC research vineyard. If the unit does not become available, we would continue with the work but use a push mower.

Groundcover sites: These sites were seeded in the fall of 2006 with either a mixture of red sandspurry knawel or Dutch white clover. In both the commercial vineyards and the LIHREC research vineyard, seed germination was poor to non-existent. In past trials, we have suspected that lingering levels of preemergence herbicides may suppress fall seeded covers. However, the research vineyard had not received preemergence materials of any type for more than seven years. We suspect the seed quality was poor, though seed came from both local harvest and a commercial source. We intended to reseed plots in 2007 but were unable to locate seed sources for any of the species – despite visiting several sites where these weeds had been seen growing in previous years. Because of insufficient amounts of fresh seed of these low growing species, this component of the project had to be abandoned.

Accomplishments/Milestones

Under trellis mowing: Mowing under the trellis as a means of weed control does facilitate the establishment of a solid stand of low growing weeds such as dandelions and crabgrass. These two species became the dominant vegetation in the mowed areas in this study. The yield results in this study suggest that no deleterious effect of mowed vegetation could be measured during the course of the study. This vineyard is equipped with drip irrigation, which may have masked potential competitive effects of the mowed weeds. It appears that under trellis mowing of native vegetation holds promise as an alternative to maintaining a bare ground strip. This would have to be verified however over several seasons. In vineyards that lack supplemental irrigation, this method of under trellis management is more likely to cause yield loss in drier than normal growing seasons.

Groundcovers: The concept of establishing living mulches under the trellis is a variation of mowed weeds. In this project we attempted to overseed low growing winter annual weed species like Red Sandspurry and knawel. These species are normally minimally competitive are should be self seeding once they are established. In a previous study at the LIHREC research vineyard, we not only were able to establish these species but we watched them thrive and spread. Our experience in 2006 and 2007 with the extreme difficulty in establishing these weeds where we wanted them to grow perhaps indicates that an effort of this type on a commercial scale is probably impractical.

Impacts and Contributions/Outcomes

Preliminary results and observations were presented as part of a talk on alternative weed management at Viticulture 2007, a regional grape industry meeting February 2007 in Rochester, NY. Approximately 100 people attended the session. The presentation, given by Wise, covered basic weed management issues, organic herbicides, CDA and sensor type herbicide applicators, groundcovers, mowing and cultivation. Based on audience reaction and comments, there remains great interest in other than conventional herbicides weed control. However, there is broad acknowledgement that issues such as cost, nuances of implement operation, efficacy of alternative materials must be evaluated, as almost all alternative methods are more costly. This is important as it can cost upwards of $6,000 an acre to manage grapes on Long Island. In general, growers are looking to slash costs, not increase them.

The same general talk is slated for presentation at a series of meetings that will take place throughout NY State over the winter. On Long Island, it will be part of a half day session on sustainable viticulture, including VineBalance, the NY sustainable viticulture program, alternative weed management, and hopefully a speaker from Oregon LIVE, a pioneering and very successful sustainable viticulture program.

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