Some of my tomato plants are dying for no reason. I just transplanted a few seedlings in the pot and after 3-4 days, a few are dead and some are doing well. Is this some kind of transplant shock? This never happened to me before. Soil is coco peat + vermi compost + sand. The temperature range is 18-30 degree C.
Disclaimer: This answer is mostly based off of my own experience.
Yes. That appears to be classic transplant shock. As Ecnerwal said, it could be cutworms, too, though. Anything that disturbs (or removes) the roots could cause this. When you transplant seedlings, if the roots are damaged or disturbed, then light (particularly sunlight) can make them wilt and die. The plant's growth will be delayed for a while if it survives.
Here are some things I have found that one can do to avoid transplant shock:
- Don't put newly transplanted tomato plants in bright light for two days. After that, give them as bright of light as you like. It'll be good for them, then. Bright light can easily wither plants with newly disturbed roots (as well as cuttings being rooted in soil on the first few days). 8-10 hours of sunlight is way more than enough to cause this for a transplanted tomato (but it may depend on what kind of sun it is and what kinds and ratios of light are coming in). In fact, one hour of bright sun could.
- Give them potassium sulfate. Plants given potassium sulfate are much more resistant to transplant shock.
- Wait until the plants are larger and stronger before transplanting.
- Make sure your soil isn't high in nitrogen. Nitrogen is like the opposite of potassium and encourages transplant shock. Fertilizing a newly transplanted plant with nitrogen (unless it's balanced by sufficient potassium, and maybe phosphorus) is a really bad idea.
- Phosphorus may also play a role in preventing transplant shock, since it, like potassium, helps to encourage root growth. I have not experimented with it, however. If the roots are healthy and strong, and have the things they need, transplant shock shouldn't be as much of a problem.
- You don't need to do this, especially with plants of that size, but soaking a plant's roots in water (without a lot of soil) for 1-3 days before planting in its new destination can reduce transplant shock (like if you dig up a plant from the garden or something).
The vermi-compost may have microbes that make nitrogen highly available to plants. I've heard that worm castings can burn plants, sometimes (and burning is a sign of too much nitrogen). So, even if there wasn't enough nitrogen to burn them, there may have been enough to make transplant shock more severe.
Whatever the case, avoiding bright light for the first couple days is the most effective preventative measure I've found. Potassium sulfate definitely helps a lot, but if you don't want to use it, don't worry about it. They should survive as long as you avoid the bright light at first. If it's already been a couple days, avoiding bright light probably won't help.
It should be noted, however, that even some plants that avoid light for a couple days will wilt after a while, but these should recover much faster.
The problem with light is much worse with cuttings rooted in dirt than with transplants.
If your problem is cutworms, it's possible that it's just dehydrated, rather than sun damaged, in which case it should be able to recover more easily. Treating it as a cutting may revive it (e.g. plant some of the stem deeper, keep it moist, and go easy on the light for a bit). However, enough of the stem appears to be buried already (so it may just grow new roots on its own).
The plants should not have suffered such a traumatic outcome from careful potting on. Damage such as this could be due to root damage when separating from seed tray, under watering or fungal attack such as damping off (unlikely at the temperatures you describe) or damage to the stem.Young tomatoes have a delicate stem and handling at the stem can cause damage? The tomatoes in your picture would have been better grown on from smaller seedlings as separation at this stage of growth must cause root damage the roots being impossible to separate and at 30 degrees they need all the help they can get.When handling young tomato plants it is better to lift them using the leaves thus avoiding damage to the stem.your plants would have been better moved at the first true leaf stage, smaller plants have less transpiration Planting into small pots and thinning to one plant gives the plants a good start in life and transplanting can be done without damage or check to growth.
I think that your problem therefore has been root and stem damage You do have some good looking plants so hope you enjoy a good crop.