NSWG Hosts Largest Workshop To Date:
Sustainable Weed Management in Vineyardsby Remi Cohen
On February 25, one hundred and sixty attendees spent one of the stormiest days of the year at NSWG’s Sustainable Weed Management workshop at the Napa Valley Exposition, making it the largest NSWG workshop to date. The workshop’s master of ceremonies was Ed Weber, University of California Cooperative Extension (UCCE) Napa Valley Vineyard Technical Advisor and NSWG member. The event was quite a success, with attendees coming from all over Napa County, from Calistoga to Pope Valley to Carneros and even Sonoma County.
The program began with a research presentation entitled Alternatives to Pre-Emergents by Kendra Baumgartner, UC Davis and USDA plant pathologist research scientist and NSWG member. Trial treatments included conventional winter and spring glyphosate Round-Up treatments, an organic essential oil based fungicide called Matran1, and cultivation with a Clemens mechanical weed remover and combinations of the above treatments. The conventional winter and spring Round-Up treatment was most effective at reducing weed biomass, and the organic herbicide Matran1 and spring-only cultivation methods were the least effective treatments. However, treatments with fall cultivation combined with other methods in the spring were intermediate in efficacy and could potentially be used as a means of reducing herbicide use in vineyards. Baumgartner prefers a mix of weed removal techniques to prevent selection of a few dominant weed species. Matran was ineffective on grasses, but did provide excellent broadleaf control. Questions were raised about the efficacy of the newly formulated Matran2, which does not have acetic acid and Baumgartner’s preliminary greenhouse trials illustrate a potentially reduced efficacy.
Tom Lanini, UCCE Weed Specialist based at UC Davis, spoke about Organic and Low Input Weed Control in Vineyards. Lanini discussed the pros and cons of several treatments. Mulches are an effective control of most weeds because of their light-blocking attributes, but a thick layer must be applied and maintained at amounts greater than or equal to 4 t/ treated acre. Experiments with buried drip irrigation systems are effective in reducing weeds under the vines but can be problematic in terms of maintenance. Lanini discussed several options for under the vine row (UVR) cultivation, including the Kimco, the Bezzerides, the Weed Badger, and a customized and very impressive looking over the vine row UVR 2-row cultivator. Cultivation works best with small weeds, shallow cultivation, and repeated passes. Hand hoeing is necessary as all treatments leave some weeds around the vine base. UVR mowing can successfully reduce weed growth, but some hand hoeing is required after and the distribution of weed species and vineyard terrain will impact the success of mowing. Propane flamers act like contact herbicides, and they work well with small weeds, but may require several passes. Steamers on the other hand are not practical for vineyard use according to Lanini. Lanini discussed the use of animals such as sheep, geese, and goats that graze on weeds. All of these animals require intensive management but can be effective, as was his experience with geese controlling grasses. Lanini has had some success with organic herbicides based on essential oils such as cinnamon, thyme, and clove, but suggests blending your own and reminds about the need for surfactants. Ed Weber warned that this is not a registered technique for vineyard application!
As Baumgartner had mentioned, Lanini also stressed the need to rotate and combine treatments for effective weed control to avoid the selection of a few dominant weed species. He also noted that some weeds are developing resistance to glyphosate, the active ingredient in the ubiquitous Round Up.
Joe DiTomaso, UCCE Weed Specialist based out of UC Davis presented Yellow Star Thistle (YST) Management, a very relevant topic considering yellow star thistle has significant distribution in Napa County. YST is a formidable weed with a very deep root system that uses a lot of water and a long growing season, germinating at first rainfall and enduring well into the summer. YST is a prolific seed producer and the seeds can survive from 3 to 5 years in the soil seed bank. Control options include labor-intensive hand removal or hoeing for small populations of YST and before seed production. Mechanical tillage can provide some control in agricultural settings if performed before seed production. Mowing is probably not an effective strategy in vineyards according to DiTomaso and improper timing and height of mowing on the part of CalTrans has caused the proliferation of YST along our CA highways. Animal grazing before spine production can suppress YST populations but will not be an effective eradication technique. Don’t let horses eat YST as it can cause mortality from a brain lesion! In open fields, burning is one of DiTomaso’s preferred techniques despite potential air quality concerns. It is extremely successful in a long-term management strategy combined with other techniques. A revegetation program can be successful in providing long-term sustainable control but requires intensive knowledge and management and other techniques as part of the management strategy. DiTomaso mentioned some biocontrol methods such as releases of the hairy weevil or the false peacockfly or even a rust disease, but these also need to be combined with other control methods. The most effective chemical controls include Transline and Round Up and, again, are best as a component of a long term integrated pest management program of YST.
The workshop concluded with a dynamic panel of diverse speakers including Kirk Grace from Robert Sinskey Vineyards, Richard Camera from The Hess Collection, Jon Kanagy from Nord Coast Vineyard Services, and Pete Richmond from Silverado Farming Company, all NSWG members. Grace discussed practical applications of many organic techniques, as he is the vineyard manager for 160 acres of organic vineyards for Robert Sinskey Winery. Grace believes the timing of operations is critical for successful weed control. Covercropping and soil fertility are his most effective tool for row middle weed management. He also has effectively used low mowing and grazing with sheep. As for UVR weed management, Grace believes in the use of Weedeaters with proper worker protection. He has had success with both mower and tiller attachments by Kimco, but they are slow, requiring operator skill and a dedicated tractor. The Clemens has provided him with mixed success depending on the terrain but can be quicker than many of the other cultivators. Grace is an advocate of a new UVR tiller by Baiano, but as many of the other speakers suggested, rotation of techniques is always a good idea. Grace has had practical experience with flaming and believes it can be successful in creating a manicured vineyard look, but can create problems in terms of compaction. Using sheep for grazing is a recent undertaking at Sinskey, but has been quite successful.
Jon Kanagy discussed the best management practices for use of glyphosate-based herbicides such as Round Up. Nord Coast Vineyard Services manages many vineyards in the Napa Valley and they use covercropping in the vine row middles. Under the vine, they prefer a small band of Round Up for effective weed control. They use low rates, a 24-inch strip width, and Kanagy also expressed the importance of timing of application. Hand weed removal will assist in late season control. Kanagy has had experience with cultivation but has been met with mixed success and challenges especially if there are late season rains like in 2003. Nord Coast is experimenting with flamers although it is a slow technique requiring multiple passes. Kanagy discussed the advantage of erosion control when using Round Up compared to UVR tillage. He is also experimenting with UVR covercropping, which is promising but can create potential problems harboring rodents.
Pete Richmond manages 200 acres in Napa, one third of which are organic, on 23 separate properties. Richmond echoed Kanagy’s concerns of UVR tillage because of the potential disruption of fine roots in the upper soil layer and the damage to grapevines from the machines. The Sunflower is one of Richmond’s preferred devices because it is less intrusive and does a clean job. Richmond uses low rates of ATV-applied Round Up as part of an IPM program because he feels it reduces erosion and eliminates a substantial portion of fossil fuel combustion that occurs with tractor driven mechanical tillers.
Richard Camera’s vineyard management philosophy is low chemical inputs on Hess’s 350-acre vineyard on Mount Veeder. His challenges are one of a hillside farmer, where steep, rocky terrain creates a major potential for erosion and makes the use of mechanical tillers difficult if not impossible. Camera used UVR mowing at Hess but this was very slow and expensive and caused outbreaks of vole populations. He uses Round-Up banding and spot spraying, but installs an electric solenoid valve to prevent dripping from the spray nozzles. He uses customized Mankar sprayers, applying low volume amounts of spray with low drift potential. Camera plans on purchasing a Weed Seeker, a device that sprays only green vegetation, and not any dried or dead vegetation, potentially reducing the amount of Round Up applied. Camera maintains a composting program and applies composted wood chips UVR.
The take home messages from the workshop were to use a variety of techniques in weed management in a vineyard. Timing of operations is critical with every control option. An intimate knowledge of a particular site is essential to develop a program that is environmentally friendly but cost effective and successful. This workshop is to be followed by a field demonstration of many of the aforementioned techniques on April 22, 2004 at the Napa Valley College Vineyard in Napa.