Knowledge Bank

A survey was conducted to document the weeds that persisted in vineyards after weed control practices were complete.  A particular interest was detection of weeds potentially resistant to glyphosate. The survey was conducted throughout the state of Ohio by visiting 31 vineyards in 2004. Each grower provided us with an area ranging from 0.33 to several acres that they felt was representative of the general weed problems in the vineyards. Weed species and numbers were counted in 20 random drops of a 25×25 cm quadrat. Herbicide spraying history, grape varieties, vineyard locations, and grapevine age were collected by interviewing the growers and visiting the vineyards. Data were analyzed by SAS 9.1 using GLM model, and means were compared according to Student-Newman-Keuls (SNK) at the 0.05 level. Crabgrass, dandelion, pigweed, foxtail, fall panicum, clover, chickweed, common ragweed, smartweed, and oxalis were the most prevalent weeds in Ohio vineyards with relative abundance values of 44.2, 25.4, 17.7, 17.1, 14.3, 11.6, 11.3, 10.6, 10.3, and 9.3, respectively. When glyphosate was the sole means of management control of crabgrass, dandelion, and oxalis was poor, relative to control with other herbicide management programs. These data suggest that glyphosate resistance may be a potential problem in these weeds. The survey also showed that weed problems were more severe in Vinifera vineyards than in Concord and French hybrid vineyards. Vinifera vineyards require hilling of soil around the base of the vines in autumn to protect the graft union from winter injury and mechanical removal of the soil hill in spring.