Tomato Leaf Problem

Asked April 27, 2020, 12:06 PM EDT

I started some tomato plants in the house about 6-7 weeks ago and they have been doing great until this last week. They have white spots on the back of the leaves now on a bunch and it is for the most part killing the leaves. Suspect it will kill the plant eventually. I have noticed some gnats flying around and was wondering if that is what is happening to them - flying insect eggs. I don't see powder from what I can see so I don't believe it to be powdery mildew. The dirt I am using is store bought from Lowes. I have included two pictures which show my issue for the most part. Any help would be greatly appreciated. I have unique stuff growing here in the house and you can't get anywhere else. By the way, I am growing these plants in my finished basement. They are a heat mat. Been on one since the beginning. Never took them off. The room is usually 78-80 degrees thanks to computers running and those heat mats. There is humidity in the air. Not a huge amount but definitely there. I have full spectrum fluorescent bulbs giving light source. No natural sun yet. Was going to start taking them outside this week or next for hardening. They really have looked good up to this week. I was patting myself on the back they were doing so well. I originally started them in peat plugs, then when they sprouted about 2 weeks or so I took the humidity lid off and transplanted to larger peat pod (3-4 inch size) and filled with dirt. Been watching every day for watering and waiting till the peat pots start to feel dry and then I water so I don not believe I have been watering too much. When I do water I put a little water on top dirt and fill containers with about half inch of water so the pots absorb the water. I try to not get water on leaves but that does happen on occasion. Most of the water does evaporate because of the heat mats. Please help.

St. Mary's County Maryland

4 Responses

Hi- the flying insects are likely fungus gnats, a type of small fly that thrives in warm, moist, humid conditions. Digging around in your containers may reveal the larvae that feed on microorganisms in the grow mix and plant roots. They are not considered a serious pest:
https://extension.umd.edu/hgic/topics/fungus-gnats

The symptom you see on the tomato leaves appears to be edema- a rupturing of plant cells due to moist, high humidity conditions. The plants are taking up more water than they can release through transpiration. Remove any plastic covers, create more space between plants, if possible, and use a small fan to circulate air. Water just enough to keep the grow mix moist.
https://extension.umd.edu/hgic/topics/edema-vegetables
Your plants should fully recover.
Jon

Thanks for the info. I will do that. Couple more questions for you. I stared the tomatoes and peppers the first week in March so I am in line with time. I was going to plant in my garden this coming weekend. We have had so much rain the garden is like a swamp. It is really wet. So I figure I would wait till it dries up some so maybe the following week. I was going to start the hardening process last Sunday but decided against it because of waiting some more. I still have the plants on heat mats. The heat mats are causing major evaporation with no lids on the containers. My basement heats up to 70-80 with all the mats. Normally the basement is about 68 degrees. Can I turn off the heat mats and should I not put them outside and wait because they will get seriously rained on? We aren't expecting sun for a bunch of days.

Last question: I got killed last year with disease and blight. This year I plan on using mulch right as I plant them in the garden. How much of a layer should I put down and should I put the mulch right up to the stem. Wasn't sure of the acid in the mulch would burn and kill the stem.

Last Question, on the tomatoes a bunch of starter seeds did not grow at all for me and some of my tomatoes I only have one plant so only way to get tomatoes will be through cross pollination. Can I snip a stem off one of the starters and try to get it to root so I can have two? I have stuff that supposedly will root anything. I wasn't sure as a starter only 6 weeks old if that would kill the starter. Other than the ones I am having an issue with they all look pretty good. Good color and lots of leaves.

Bill Orr

Also another question. When I do plant tomatoes and peppers in the garden, what is the spacing I should use to allow air flow?

I was planning the following:

X - 1 - X - 4 - X - 1 - X - 4 - X - 1 - X - ......
2
X - 1 - X - 4 - X - 1 - X - 4 - X - 1 - X - ......

Where 1, 2 and 4 are the spacing. 1 represent 1 foot and 2 represents 2 feet and 4 is 4 feet. I plan on putting plants of the same type in the 1 foot separation areas. I.e. 2 Purple Cherokee tomato plants will be 1 foot next to each other. Then 4 feet away I will have 2 black cherry plants right next to each other 1 foot away. I tried 3 feet and 2 feet last year with 2 feet separation on rows and i had a bad year last year. I got told it was too close together. I use 1 foot rigid square cages for every tomato plant in the garden. Each one has its own cage. I try to keep stems and leaves inside the cage until they grow larger than the 4 feet cage and then use an 8 foot rod in the middle of the cage to keep them going straight up. They do spread out more once they get longer then the height of the cage if they grow that big. Last year I didn't have that issue. Most died fairly quickly.

And how high should I mound the dirt where I plant? Last year I had 8 inch mounds. Looked funny being so tall and I had a terrible year last year.

Last question. I had hook worms for the first time last year. What Do I do to make sure they don't come back?

Hi-
Yes, turn off the heat mats.

Put your plants outside to harden about one week before you intend to plant them. They need to be under some type of cover (porch, carport) if heavy rain is expected.

Spread a 2-4 inch thick mulch around plants- last year's tree leaves, grass clippings (no herbicides), or newspaper covered with straw.

Here are some web pages to read about foliar tomato diseases:
https://extension.umd.edu/hgic/topics/early-blight-vegetables
https://extension.umd.edu/hgic/topics/septoria-leaf-spot-vegetables

The key is adequate spacing between plants (see below), removing lower leaf branches and pruning of suckers to increase air circulation, and possibly spraying a preventative fungicide (e.g., copper, mancozeb, daconil) before you see symptoms. Water at the base of your plants; try to keep foliage dry.

Tomato is self-fertile so one plant of one cultivar will produce fruit without cross-pollination. You can plant suckers of any of your plants to increase the population.

Spacing- you should shoot for 4.5-5 ft. between rows of tomato with 2-3 ft. between plants, especially since you are using cages. Pepper spacing is very dependent on the type. You need 3 ft. between Habanero but just 15 in. between Cayenne. In general, most types need 18-20 inches between plants.
https://extension.umd.edu/hgic/topics/tomatoes
https://extension.umd.edu/hgic/topics/peppers

Sorry, but we're not trained to answer questions about hookworm.
Jon