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October 2016 WINES&VINES 77 WINE EAST GRAPEGROWING species could be used as an envi- ronmentally responsible means to suppress the use of herbicide and as a proactive measure to reduce excessive vine growth through competition with the grapevine root system for soil resources. Cover crops as an herbicide alternative Herbicides are the most widely used pesticides in the United States because they effectively suppress weed growth and are easy to apply. 4 However, repeated herbicide use increases the risks of resistance development. 5 Also, bare soil left exposed after herbi- cide use or tilling is susceptible to erosion, soil structure degradation and crusting, as well as increased water runoff and leaching of ni- trates and pesticides. 4 One alternative option to the under-trellis herbicide-treated strip is to establish cover crops directly beneath the vines (intra- row) in addition to between the rows (inter-row), thereby creating a complete floor cover (see photo at right). Under-trellis cover crops could serve multiple purposes, depending on growers' needs and the cover crops used. Cover crop species have differ- ent degrees of competition with vines for soil resources such as water and nutrients. For example, annual cover crops tend to be less competitive for soil nitrogen re- sources than perennial plants be- cause of their shorter growth cycle and less root development. Fur- thermore, fine fescues such as Festuca ovina tend to be less com- petitive than other perennial grasses such as tall fescues (Fes- tuca arundinacea Shreb). 6 Planting annual cover crops such as buckwheat (Fagopyrum esculentum) or annual ryegrass (Lolium multiflorum) under the vines may eliminate the need for herbicide with little impact on vine size or fruit composition. Most of the work on under-trellis annual cover crops has been con- ducted in the cool and humid Fin- ger Lakes region. 4,7,8,9 In the northeastern United States, peren- nial cover crop species are not suitable for the under-trellis area due to the need to mound soil from the under-vine row around the graft union for insulation to protect scion budwood from low winter temperatures. However, annual buckwheat planted in late May in mature vineyards in up- state New York (at a seeding rate approximately equal to 350 pounds per acre) was found to compete extremely well with weed pressure without compro- mising vine size 8,10 or fruit compo- sition 7 (see top photo on page 78). Cover crops to reduce excessive vine growth and increase crop load Despite the presence of cover crops between the rows (the inter- row area), grapevines can still exhibit excessive vegetative growth in regions with deep, fer- tile soils and ample precipitation during the growing season (see middle photo on page 78). Large and dense canopies with heavily shaded fruit may contribute to reduced fruit and wine quality as well as an increase in disease pres- sure. 11 In addition, excessively vigorous grapevines are more ex- pensive to train and manage. Main and later shoot thinning, multiple passes of fruit-zone leaf removal and hedging are costly manage- ment practices 1 often required to improve the light environment for the clusters. Cool season perennial grasses have been planted by researchers under the trellis in vineyards lo- cated in Virginia, North Carolina, Long Island, N.Y., and Pennsylva- nia to impose competition for moisture and nutrients early dur- ing the growing season, when grapevines grow vigorously in the eastern United States. 6,12,13 Compared to an herbicide- treated soil strip, complete vine- yard floor cover cropping reduced excessive vigor of Cabernet Sau- vignon vines in the wet and humid region of North Carolina over a six-year-period. 6 Among the pe- rennial grasses tested, Festuca arundinacea cv. Elite II (a turf-type tall fescue) and cv. KY-31 (a for- age-type tall fescue), were the most effective in reducing vine vigor and increasing light avail- able to the fruit with minimum impact on crop yield. 6 Creeping red fescue (Festuca rubra) planted under Cabernet Sauvignon vines in the fall of the second year of vineyard establish- ment reduced vine size in a favor- able way (an average of 26%) and increased sunlight fruit exposure by 35% over a seven-year-period compared to herbicide-treated strip. 10 It is important to note that this study was conducted by Dr. Tony Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER Complete vineyard floor cover cropping is achieved using annual ryegrass (Lolium perenne) planted under the trellis (intra-row), while resident/native veg- etation is established in the inter-row.