Sweet 100 cherry tomato leaf disease identification
Hello officer(s) of the extension office, I am a new gardener growing on a 2nd story rooftop. I have two sweet 100 cherry tomato plants that I transplanted 3-4 weeks ago into a sub-irrigated planter (Earthbox). Their growth has been OK but the leaves are getting yellow spots that then become confluent and lead to discoloration of the whole leaf. Could the this problem may be related to underwatering vs viral disease? (I've been maintaining the water level in the reservoir with a float valve at about 1-1.5 inch depth.) Any advice you have would be greatly appreciated. Thanks, Mike
Although the pictures aren't quite clear, it looks like the tomato has a moderate infestation of spider mites. They prosper on stressed plants and in warm, dry weather. A rooftop's reflected and radiant (overnight) heat can promote conditions where mites would thrive. Under-watering might add to the mite problems, but if your tomato isn't wilting often and the soil a couple of inches beneath the surface isn't dry, then this is probably not an issue. If watering is irregular, however, this can lead to other tomato health problems like blossom-end-rot on fruit and damaged roots and leaves. We do not know what water level you'll need in self-watering planters like these such that the soil neither stays too wet nor too dry; hopefully the boxes came with instructions for guidance. You may need to experiment or switch to hand-watering from above as needed to supplement. We believe Earthbox planters come with a excess water drain high enough into the interior that any water level that would risk flooding the root zone will simply drain out. In that case, it's probably best to keep your water reservoir filled up to this point so the water level isn't too low for roots to reach.
Control tips for mites on vegetables can be found on this page: https://extension.umd.edu/hgic/topics/spider-mite-vegetables. When spraying, thorough coverage (including of lower leaf surfaces) is important, and re-treat as advised on the label's instructions, since multiple applications will be needed.
Thank you for speedy and extremely helpful response! Thrilled to hear that this is a problem that can likely be controlled.