|I have some tomato plants growing in full sun in the tropics and when they reach a height of about 3 feet some of them begin to wilt from the top downwards and finally die. I am not sure if it is due to fungus or lack of water. Do you know what the problem is?|
|The diseases common in Malaysia may or may not be very different than the diseases found here in the U.S. If possible, check with local growers or other knowledgable people in your region.
That said, a few thoughts on the problem: Wilting can be caused by lack of water--be sure your plants are getting the equivalent of at least 1" of water per week. If your soil is sandy, that might be part of the problem--sandy soil dries out quickly. The addition of organic matter (compost, well-rotted manure, etc.) helps improve such soils.
Wilting can also be caused by other factors. It can indicate a problem with the roots, such as nematodes, that interfere with the plant's ability to take up water. There are also wilt diseases, caused by fungi, bacteria or viruses, which damage the plant's water uptake. You'll need to identify the culprit so you can take appropriate action.
I hope this is helpful.