Use of hydroponic cultivation syste

Use of hydroponic cultivation systems in greenhouses offers a unique situation that may make conditions more favorable for diseases. Because the treatment for removal of microorganism from the liquid media has not been effective, a hydroponic culture system is easily infected by soil-borne pathogens such as Fusarium and Pythium fungi. Most pathogens cannot be completely excluded from the greenhouse environment. Airborne spores enter through doors and screens, soil-borne pathogens enter through dust or contaminated soil on shoes, tools, or equipments, and some pathogens are introduced on seeds or contaminated propagating materials. The temperature, light and fertilizer regimes are optimized for maximal plant growth, but these conditions may also be favorable for pathogens. The nutrient solutions lack the microbial diversity, allowing soil-borne pathogens to grow and spread quickly, especially in closed re-circulating systems. Hydroponic systems, such as rockwool, nutrient film, or ebb and flow, present another set of disease problems ( Paulitz, 1997).