2,4-D Herbicides in Central Washington

Usage of 2,4-D herbicides has been extensive in centrai Washington wheat-growing areas for many years. The rapid development of a grape industry, both Concord and Vinifera, since the early 1960’s has had periodic, widespread damage in vineyards due to drifting 2,4-D. Beginning in the Spring of 1973, programs of 2,4-D monitoring have been conducted in the lower Yakima Valley of central Washington. In 1976 a program was begun to test the drift potential of 2,4-D aircraft spray systems. Correlations between atmospheric monitoring data, observed vineyard damage, and weather patterns indicate that long distance transport—10 to 50 miles—is an important factor in the 2,4-D concentration pattern. Some simple models have been developed but many questions must be resolved.