Control of Pythium Root Rot of Vegetable Pea Seedlings in Soilless Cultural System

This study was initiated to develop non-pesticide methods to control Pythium root rot of vegetable pea seedlings in a soilless cultural system. The disease was not prevalent when new seedling trays were used for growing pea seedlings. However, when the cultural trays were used repeatedly for the same purpose, mycelia and oospores of Pythium aphanidermatum and P. ultimum produced by the infected roots contaminated the trays and became an important inoculum source to cause severe root rot. Drying the used trays under sunlight for months or immersing the trays in a calcium hypochlorite solution (2,000 ppm) for 24 hours before planting was effective in preventing this disease. Incidences of the disease were drastically reduced from 60-80% to less than 10% and yields of pea seedlings averaged 772 g/tray to 212 g/tray when the used trays were pre-treated with calcium hypochlorite solution comparing to the non-treated controls during hot growing season.