Hopefully someone can help me identify these dark necrotic spots on my lettuce. They start off on older leaves after about 3 weeks in the system then eventually spreads to the entire plant.
About the system:
DWC grow beds with airstones every two feet. Sufficient tilapia and catfish in the fish tank, 2500L radial flow settler, two 1000L fine solids filters, 1000L IBC tank MBBR.
Several fans around the greenhouse for circulation.
Seeds used: Rijk Zwaan
pH: 5.9-6.1
DO: 4-6 mg/mL
Nitrate: 40-60ppm
Nitrite: 0
Ammonia: 0
Iron: 1.76ppm
Water temp: 26-28C
Built this system with a friend as a side project to improve the availability of leafy greens in our local area. The system has been cycling for over a year and only recently started to produce healthy(ish) looking plants. More recently, this infection began to show up in various lettuces.
Any ideas would be greatly appreciated. submitted by /u/safetywu
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http://dlvr.it/TQMbGS