Tobacco mosaic. Photo courtesy of www.ipmimages.org.
Pests and Diseases in Seedling Beds: Tobacco mosaic, also called “calico” or “walloon,” is a serious viral disease that often gets a head start in the seedling bed. Sterilization of the soil (by wood fire or steam, as mentioned above) is a first step in suppression, followed by common sani- tation procedures like removing crop res- idues, washing hands, and restricting use of tobacco products when working with the seedlings. In the field, the spread of mosaic may be slowed by similar procedures, and by removing and destroying diseased plants and eliminating solanaceous (nightshade family) weeds.
One novel approach to controlling tobacco mosaic was reported in the Indian Journal Honey Bee. The journal stated that farmers in parts of India used skimmed milk as a treatment to prevent this disease. A solution of five liters of milk in 100 liters of water is sprayed about one month into the season.(5)
Bacterial diseases such as angular leaf spot (Pseudomonas angulata), also called “blackfire,” and bacterial leaf spot (P. tabaci), also called “wildfire,” can be problematic in seedling beds. Strepto- mycin and copper sprays have commonly been used in these instances.
Blue mold or downy mildew in tobacco is caused by the fungal organism Peronospora tabacina. Primarily confined to planting beds, the disease is a serious one that may cause complete loss of plants if not con- trolled. It is favored by wet warm weather,
Blue mold. Photo courtesy of www.ipmimages.org.
and winds easily scatter the spores over large areas.
Traditional cultural techniques to suppress blue mold include (3):
Rotating the planting bed to a new location each year
Selecting sites with good air and water drainage, sunny exposure, and no shade
Sowing more bed space than is needed for the crop and compart- mentalizing the planting—creating two to three smaller beds rather than one large one
Sowing beds early
Avoiding high plant densities
Removing covers from plant beds frequently to admit sunlight and air
Fertilizing and watering properly to assure vigorous plants
Transplanting as early as conditions permit
Cutworms are an occasional pest of tobacco in seedling beds. Removing weeds from around the bed area is a good prevention measure. Bacillus thuringiensis (Bt), for- mulated as a granular bait, may be used to control the pest. More information on cutworm control can be found in ATTRA’s Organic Field Corn Production.
Organic Tobacco Production