Dreary days are a great time to peruse the garden catalogs with their dazzling photographs of vegetables and flowers. In addition to variety descriptions, they also provide a wealth of information about disease resistance and time of planting. The time of seeding is determined by the frost free date for planting outdoors and the type of seed. To produce transplants, cool season crops (broccoli, cabbage, and cauliflower) are seeded 10 weeks before planting in the garden. Tomatoes, eggplant, and peppers require about seven weeks indoors, but cucumber muskmelon, squash, and watermelon need only four weeks indoors before planting outside. When seeding, sterile growing medium should be used for disease prevention. Also, covering seed flats with a thin pane of clear glass or plastic wrap will help retain moisture in the growing medium and enhance germination success.
When seeds of disease resistant varieties are unavailable, disinfectants and protectants are another way to enhance germination and seedling growth. A simple hot water soak is an effective way to disinfect fungi and bacteria from some seeds when equipment is available that precisely controls a constant high temperature. For this type of treatment, seed is placed in a cotton or cheesecloth bag and immersed in water at 100°F for 10 minutes. After this, it is plunged into water at another high temperature (118 to 122°F) for a prescribed length of time. The water temperature and time of immersion varies with the seed type. The following web site provides more detailed disinfestation information: ipm.illinois.edu/diseases/rpds/915.pdf. Microwave, ultraviolet radiation, or bleach soaks can also be used to disinfect seeds, but methods vary for each seed type.
More commonly, seed companies treat their seed before shipping it to customers. A relatively new, organic seed treatment is Natural II, which is composed of microbial products, kelp, yucca, gypsum, and clay. Other organic products, such as Actinovate, RootShield, Mildew Cure, Oxidate, Regalia, etc. are marketed for seedling and/or soil borne disease control. Magenta or blue-colored seeds generally have been treated with more traditional fungicides such as thiram or captan. Seed labels must always list the pesticide applied and any health hazards associated with the treatment.
Some of the common seedling diseases may be fungal, bacterial, or viral and can be found on the seed coat, within the seed, or in the soil. Some of the common fungal pathogens are Pythium, Fusarium, Rhizoctonia, Verticillium, and Phytophthora. Tomato, tobacco, watermelon, and zucchini mosaic viruses may also be problematic. Unfortunately, seeds that resistant to these organisms are not available. Symptoms may include seed rot, damping-off (i.e. seedling wilting and death), and root rot. Several seed catalogs list resistance of seeds to specific disease organisms.
REVISED: March 5, 2013