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So I had about 50 tomato seedlings. 3 different kind. They were quite beautiful, big and some of them already flowering. I made holes for them, put some dried organic manure pellet to the bottom. I removed the bottom leaves, and bent the tomatoes in a bit. After I buried them back I gave them some water (to form a small pond over them what leaks in a few minutes) This is exactly how I done it in the previous years as well with a really good result. But now after a few days they seem to be dying out. The lower branches are drying off completely. I noticed that there are small fruit fly like insects on a lot of them. I removed them with my hand today just in case. I don't know if they are causing this. Also the day after the planting there were a bigger rain. Is it possible that because of that the plants have been over watered?

Please see the images: https://imgur.com/a/ftPkEcV

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It looks like your young tomato seedlings experienced some sun scald. Sun scald effects plants that go from a climate controlled environment (your greenhouse/home) to the variable and often harsh environment of mother nature. In other words your tomato seeds did not acclimate quick enough to the outdoor environment. The UV rays from the sun are so powerful that the tomato plant hasn't built a resistance to it yet. As the tomato plant matures and gets acclimated to the suns' rays and outside weather/temperature, the tomato leaves will thicken. The thick leaves are much more resilient to sun scald. To prevent this from happening it is best to move your tomato seedlings from your greenhouse and place them outside in the evening once the overnight temperature remains above 55F. Under 50F can stunt the growth of tomatoes. Put them outside in the shade for the first 3 days. Do not allow the sun to shine on them for more than 15 minutes. Then gradually place them in indirect sunlight for 30 minutes in the evening hours, then 60 minutes the next day, then 2 hours, 3 hours and so on until they're outside all day. Build up the hours from the evening and work backwards. Since the evening sun is less powerful than the midday and morning sun. This process usually takes about 10-14 days. As soon as you see the leaves start wilting, move them into the shade and make sure they are watered but not soaked. They should perk up in an hour.

To completely avoid this hassle you can start your tomato seeds outdoors. A waterproof heat mat will help with the germination and provide bottom warmth in case of some colder nights. Since the seeds will see the sun as their first light source, there will never be a need to acclimate the seeds from your greenhouse/home to the outdoors, thus saving you 10-14 days of having to move you seedlings every night. Another benefit to starting tomato seeds outside is the plants will have a much stronger trunk. The wind and strong UV rays cause the plant to build up a resistance to the elements.

As for the sun scalded leaves, they will eventually fall off. But tomatoes are very vigorous and new growth should appear at the top.

I experienced this scenario last year. Lost about 30 tomatoes to sun scald due to a couple >80F April days. This year I gradually acclimated my greenhouse tomatoes as well as started tomatoes seeds outdoors. The outdoor started tomatoes where much stronger (I didn't have to stake them until they were 3ft. tall) and there was not one single leaf with sun scald.

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  • I give my tomatoes about a week outside in semi-shade to sunharden them, and never get scalding. Some years you can get away with just planting in sun. Other years your plants can get toasted. It's best to play safe. – Wayfaring Stranger Jul 30 at 19:54
  • Thankfully every one of them survived, though a few of them had to start over from the ground and they are producing a lot of fruit now. Next year I'll try out what you wrote to let them acclimatise better. Thanks! – emul Aug 2 at 14:31

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