Greenhouse Monitoring

Growers should constantly monitor the crop from seeding to setting of transplants for signs and symptoms of disease. Frequently, wilted or yellow plants indicate disease is becoming established. Trays with diseased plants should be removed promptly from the vicinity and destroyed. Clippings should be collected in bag attachments and removed from the vicinity of the houses, as some pathogens (e.g. white mold) may continue to produce spores on dead plant material.

Sanitation 

Sanitation practices are also very important, both during actual production of the transplants as well as before and after a production run. Sanitation practices are those that strive to prevent introduction of pathogens into the production area and to prevent their spread. The use of sterile peat-vermiculite soil mixes, sanitizing clipping mowers with bleach solutions, washing used trays with bleach solutions, promoting good drainage and dry walkways, etc. are examples of sanitation practices. It is suggested that mowers be thoroughly cleaned with a 50% solution of household bleach after each clipping. This is very important for Mosaic control. Remove plant clippings from the vicinity of the greenhouse structure. Do not allow tobacco products to be used in the greenhouse. Workers should wash their hands with abrasive soap or dip them in milk prior to handling of transplants and trays. Do not use surface water (ponds, streams) for irrigation or filling of float trays. These waters may contain pathogens. After trays are used, they should be thoroughly washed to remove old soil mix and stored in a clean, dry location. Before they are used again, they should be washed or drenched in a 10% bleach solution, and rinsed with clean water. Producers should keep all aspects of tray filling and transport of filled, seeded trays to the greenhouse as sanitary as possible. Contamination of trays can occur anywhere in the path.

Walkways should be constructed so that they are as clean and dry as possible. Using gravel or even cement walkways promotes drainage and helps prevent pathogen-laden soil from being introduced into the production area. Make sure any equipment, including rubber boots used to work in float baths, are cleaned and sanitized before they are used in production houses. Do not use any tobacco products within or near the greenhouse. Do not bring fruit into the greenhouse structure.

Transplant Production 

Finally, strive to produce the transplants using good production practices. Make sure your water source is a good one and the pH and bicarbonate levels are acceptable. Allow adequate fertility for production, but do not over-fertilize, as this causes succulent plants to develop that are more susceptible to diseases. Make sure temperatures in the house do not become extreme (hot or cold) as these stresses may cause the plants to become weakened and more readily attacked by pathogens. Do not heat the float water. Tobacco seedlings can grow in float systems with very cold float water. Low float water temperatures reduce the spread of Pythium spp. in the float water. Heating the float water may increase Pythium seedling disease.

 For more information about greenhouse tobacco production, see the 2010 Growers' Guide.