Often, Pythium is a “secondary infection.” This means that Pythium does not actually attack plants until they have been damaged in some manner. Even an absolutely clean indoor hydroponic system will still have some Pythium spores present as such fungi are naturally present anywhere – in the soil, water, air, dust, and vegetation – so it is not easy to eliminate the source of this root rot disease. But there are ways to reduce the number of Pythium spores present in a hydroponic system. One is to sterilize the supply of water which could be contaminated with intolerable levels of Pythium. Water from streams, rivers or dams should be sterilized before it’s used for a hydroponic system.
Even under ideal environmental conditions, a plant at any growth stage is susceptible to Pythium. The symptoms of this disease in an older plant are wet and browned root system, and collapsed and hollow roots. An infected plant may grow poorly and then eventually wilt for no obvious reason.
Pythium spores thrive in temperatures between 20°C – 30°C (68°F – 86°F). But a plant could still get infected even outside this temperature range when the damaged tissue of the plant is available for the pathogen’s fast colonization. A low level of Pythium that could not infect a plant at a cooler condition will spell disaster at a warmer condition, particularly when the higher temperature is associated with plant stress and oxygen deficiency in the root zone.
Pythium is one of the so called “water moulds”, that is, it thrives in wet conditions, just the conditions normally found in a hydroponic garden or in coconut coir or a potting soil.