Grape growers are faced with many challenges across the growing season, including insect pests (leaf hoppers, moths, mealy bugs, mites), diseases (Pierce's disease, oak root fungus), mammalian pests (gophers, voles), weeds, erosion, nutrient loss, frost damage and grape quality. This case study combines an ecological approach with data from a variety of studies to illustrate how different plant species and management approaches can solves these many interacting management issues. There are always trade-offs between beneficial and negative effects of cover vegetation choices (see: effects of cover crops) and the approach chosen depends on local issues and management goals, etc. (see: factors to consider). By examining the suite of ecological functions that a given species and/or combinations of species can have (see: traits of vineyard vegetation), these tradeoffs may be minimized and vegetation management strategies can be developed that best achieve the multiple goals of vineyard management. 

Ecologically-distinct plant types like grasses and legumes generally have similar effects on ecological processes, yet some species perform additional functions (see: traits of vineyard vegetation). For example, all grasses prevent erosion, enhance soil structure, organic matter, traction and water penetration, and most tolerate mowing and persist without added irrigation. Nevertheless, oats remove excess water and open hard soil, orchard grass and tall fescue inhibit weeds and decrease vine vigor (enhancing fruit quality), while zorro fescue and blando brome interact little with vines. Growing native perennial grasses in vineyards also conserves rare species while enhancing attractiveness for tourists. Vetches boost soil nitrogen, attract beneficial insects, and inhibit nematodes. Still, high N levels decrease fruit quality and increase pests, so that legumes with low N-fixation, like clovers and medics are usually best. These also tolerate drought, suppress weeds and compete little with vines.

There is no perfect way to manage vegetation to address multiple issues; using one strategy or species can lead to other problems. Cover crops can compete for water and nutrients, inhibit vine establishment, and increase frost damage- while mowing reduces this, it also reduces cover benefits. Varying cover species between rows can balance nutrient inputs, vine vigor and beneficial insect attraction. Management can modify vegetation effects as well- disking incorporates cover nutrients, while mowing without incorporation can facilitate N losses and minimize competition. Legumes can increase gopher damage, but interplanting Blando brome with legumes can decrease gopher pressure without significantly impacting vines or using up legume N. Some cover species can increase beneficial insects and inhibit disease, nematodes, and insect pests. Still, the effects of species-rich covers are stronger than single species, at least on nematodes. Even plants bordering vineyards can serve as refugia for beneficial insects, and woodlands and riparian vegetation increase water infiltration, nutrient filtering and storage. The integrated use of multiple cover crop and border species based on ecological knowledge of vegetation functions and interactions can improve vineyard sustainability.  

Use Renewable Resources

Legume cover crops can provide biologically fixed N to vines.

Minimize Toxics

Cover cropping can decrease use of toxic herbicides and pesticides.

Conserve Resources

Cover crops decrease erosion, sustain and increase soil organic matter and nutrients, and can conserve species diversity.

Manage Ecological Relationships

By choosing specific cover crops, farmers can manage nutrient cycling, pests, beneficial insects, diseases and weeds.

Diversify

Diversifying landscapes (cover crop strips, oak preservation, riparian zones) and biota (species of cover crops, natural vegetation) is beneficial for vineyards. 

Cover crop publications from UC Davis

The Viticulture and Enology Research Center

Related Publications:

Daane, KM, MJ Costello, GY Yokota, WJ Bentley. 1998. Can we manipulate leaf hopper densities with management practices? Grape grower.

Eysberg, CD. 1990. The California wine economy: natural opportunities and socio-cultural constraints- a regional geographic analysis of its origins and perspectives. Faculty of Geographical Sciences, University of Utrecht, The Netherlands.

Flaherty, DL, FL Jensen, AN Kasimatis, H Kido, WJ Moller (editors). 1981. Grape pest management. Division of Agricultural Sciences, University of California. Publication 4105.

Hanna, R, FG Zalom, CL Elmore. 1995. Integrating cover crops into grapevine pest and nutrition management: the transition phase. Sustainable agriculture technical reviews.

Ingels, CA, RL Bugg, GT McGourty, LP Christensen (editors). 1998. Cover cropping in vineyards: a grower's handbook. University of California, Division of Agriculture and Natural Resources. Publication 3338

Ingels, C. 1998. Cover crop selection and management in orchards and vineyards. California Plant and Soil Conference Proceedings, Modesto, CA.

Merenlender, AM, and J Crawford. 1998. Vineyards in an oak landscape: exploring the physical, biological and social benefits of maintaining and restoring native vegetation in and around the vineyard. University of California Division of Agriculture and Natural Resources. Publication 21577

Striegler, RK, MA Mayse, W O'Keefe, DR Wineman. 1997. Response of Thompson seedless grapevines to sustainable viticulture practices. CATI publication # 970102