Alternative fumigants for methyl bromide in tobacco and pepper transplant production

Tobacco and pepper are high-value cash crops in the southeastern USA that require vigorous transplants free of pathogens and insects. Typically soil seedbeds are treated with methyl bromide prior to seeding. Soil fumigants metam-sodium, dichloropropene, chloropicrin and dazomet covered with polyethylene film were evaluated at several rates alone and in combination as alternatives for methyl bromide soil fumigation of tobacco and pepper seedbeds. The studies were conducted over a three-year period, with materials applied in the fall prior to seeding at the beginning of the following year. Nematode and insect pressures were low in each of three sites, but the tests extensively evaluated weeds and soilborne fungi management. Metam-sodium at 935 L ha(-1) performed well in all three tests. The combination of metam-sodium (468 L ha(-1)) plus dichloropropene+17% chloropicrin (126 L ha(-1)) provided good control of most of the pests and had high plant yield and vigor when covered with a polyethylene film immediately after treatment. A similar treatment not covered with polyethylene film but sealed with a mechanical soil cultipacker provided poor control of weeds. Stunting of tobacco and pepper was noted, especially in plots treated at the highest rates of metam-sodium plus dichloropropene and chloropicrin. These treatments had a pungent odor associated with the treatment, which persisted for several weeks after polyethylene film removal. Many of the treatments, especially metam-sodium and metam-sodium in combination with dichloropropene and chloropicrin, compared well with methyl bromide fumigation for seedbed pest control. (C) 1997 Elsevier Science Ltd.