Chemical weed control of burley and dark fire-cured tobacco

Tobacco culture as it is known today was adapted from original Indian culture. Exactly how long the Indians grew and used tobacco is not known, but the earliest reference to it occurred when Columbus arrived in the Americas in 1492. After the settlement of Jamestown, Virginia, the production of tobacco increased substantially and by 1622 commercial production had reached 60,000 pounds. Today, the United States leads all other countries in the production of tobacco; however, China leads in total acreage grown. In 1963 Tennessee ranked fourth as a tobacco producing state, producing approximately 7 per cent of the total United States crop (43). Variation in climate and soils enables the production of hurley, dark air cured, and dark fire-cured tobaccos in Tennessee. Production of an acre of tobacco requires approximately 450 manhours of labor which includes growing, harvesting, and marketing the crop (34). Usually three to six cultivations and one to three hoeings sure required, the number depending on weediness and effective ness of cultivation. These operations may injure the plants, reducing yield and quality of the leaf unless caution is used. Tobacco farmers are subjected to high labor costs; therefore, selective herbicides offer potential for reducing production costs. Richards (36) has estimated that weeds cost United States' farmers five billion dollars per year. Estimates by Parris (32) indicate that plant bed weed control and losses in yield cost Tennessee tobacco farmers $1,342,000 in 1962. This figure does not include labor costs for plant bed preparation and field cultivations. When used properly, herbicides may; (1) reduce labor requirements to produce a crop, (2) give weed control regardless of moisture conditions, and (3) reduce leaf and root injury associated with cultivation. The objectives of this study were to determine: 1. The tolerance of hurley and dark fire-cured tobacco to several herbicides. 2. The effects of these herbicides on the tobacco plant and on the yield and quality of the leaf. 3. The effects of these herbicides on weeds common to tobacco fields. 4. The most effective rates and methods of application of herbicides under Tennessee conditions.