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.
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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! Simon
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Thanks for your comment. Yes it is Root Rot. I read that when the water temp. exceeds 70 degrees you can expect this fungus. The yellowing seems to be nutrient related problem. I can do a water change and the leaves start to green up again. The thing is I didn't start having this problem until 20 days after I added the lights. I thought it might be my supplier nutrient, so I used a different source. I just brought some young Lettuce to full sunlight and the leaves are a lighter green than normal. I really hate to stop using the lights as it has reduced my losses quite a bit. In Thailand they have started using another bactiera to fight this, but I don't as yet have any or the name of it. My wife deals with this end of matters. The Ph I keep at 6.4 to 6.6 and EC 1.8 to 2.1 I'm open to any thoughts you or other may have.
Regards Ray
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Answer from Simon:
Hey Ray, I think you provided a good clue when you said the plants green up when you change the nutrient (water). It may be largely a nutrient problem.
I suggest you drop the ph to 6.0 and the EC to 1.6. The solution may well be too alkaline and/or strong/rich. It is better to have it a little too weak than too strong. Give that a try.
