Ask Erik

Dear Rik,

That sounds like a frustrating situation to have. In spite of having installed a first-rate water/nutrient handling system you are experiencing symptoms of disease, which you suspect is pythium.

It may sound simple, but is the growing medium or system staying too wet? Also, even though the reservoir temperature is totally optimal, is the temperature in the growing medium excessive, or higher than optimal?

In N.F.T., (Nutrient Flow Technique) there is typically just a film of nutrient solution surrounding the roots. In a hot environment, the temperature of the root zone may not be sufficiently protected from higher air temperatures by smaller volumes of solution, even if the solution originates into the system at optimal temperatures. The temperature inside of the growing channels should also be monitored, including the temperature of the solution in the channels. With slightly longer channel runs or slower draining channels you may find the temperature of the solution going in is optimal, while the solution coming out is not in the correct range, and may be contributing to the pythium problem you have described.

Also, what is the growing medium that your seedlings/transplants are in? If it is a slower draining medium such as peat or coco, it may be holding too much moisture around the plant’s stem once transplanted into your N.F.T. system. The material used in your starter plugs may also be heating up, although the solution in your reservoir is optimal.

Note that treating your water and growing system greatly reduces the population count of pythium spores, but it would seem virtually impossible to eliminate the fungal spores from any growing situation. Pythium spores may also be present in the surrounding air. As you are likely aware, the trick is to prevent the conditions which pythtium requires to prevail. Anytime the growing medium or root system is kept warm and wet for prolonged periods, the door for pythium infection is open. N.F.T. systems tend to be on the wet side, as the flow of solution is relatively static compared to more intensive re-circulating hydroponics systems.

I recommend the following to you:

• Slope the channels for improved and faster drainage; the chilled solution may stay in the optimal range for the entire duration in the channel before being returned to the reservoir.
• If your channel depth is adequate, increase the depth of solution surrounding the plant’s roots, but avoid submerging the transplant/plug material. The increased volume of solution around the roots will better help to buffer temperatures. If you increase the depth, you must ensure that there is sufficient flow rate to keep the solution moving past the roots.
• Inspect the root system for insects and larvae such as fungus gnats. If insects are piercing the roots to feed, they are potentially introducing diseases causing agents directly into your plants.
• If the pythium is water-borne, using a high quality non-ionic wetting agent may help to prevent the fungal spores from sticking to the roots system, decreasing the incidence of pythium infection.
• Adding a digestive enzyme for hydroponics to your nutrient solution or as a weekly treatment will help to reduce the amount of decaying organic matter which may be present in your system. Roots grow back and die all the time. These decaying roots are a perfect host for pythium in warmer conditions. The digestive enzyme will help to eliminate any decaying organic matter at an accelerated rate, and help to improve the overall health of the root system.

Please feel free contact me again to confirm some of the details regarding your growing situation so that a more exacting diagnosis and solution can be formulated and shared with Maximum Yield’s readership.

Cheers, Erik Biksa