I started using a UV light to kill this bacteria on my lettuce and had some good results, but a few weeks later my lettuce started turning yellow. does a UV light have a negetive effect on the fertilizer? Is there another way to deal with Pythium? I live in Thailand and the water temperature is 80 degrees and I have no way of getting the temperature down to below 70 degrees.
Answer from Simon:
Can I ask if you have somehow confirmed by an expert that your yellowing problem is indeed Pythium?
We are not experts on plant diseases, but do know that Pythium is a fungus infection which causes wilting. The outer, older leaves of infected plants can become yellow. Many growers use this symptom as a positive diagnosis of Pythium root rot, but since other factors may cause yellow lower leaves this should not be the only criterion used. Always examine the roots, being sure to look for the rot or death of feeder roots. Yellowing can also be caused by too alkaline a solution, so check the ph for that.
As far as nutrient solution being 80 degrees, you obviously have been having some luck with hydro even with it that warm. Sometimes you gotta make do with what you have, as the alternative is expensive and electricity-hogging water chillers. I do not think the nutrient temp has anything to do with your problem, as fungus actually prefers a cold/damp environment.
Plant stress, excess water, low aeration, and high salts (nutrient concentration too high) can contribute to conditions ideal for Pythium infection.
As far as treating this disease, I am afraid that from all we have read, it is best to rip the plants out, dispose of far away from the growing area, thoroughly sterilize your growing apparatus, and start over with disease-free seedlings.
As far as using UV to treat fungus diseases, not familiar with that method, however I do know that UV is a pretty benign treatment that is not likely to mess with your nutrients.
Hope this helps!
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