Hi there, I hope you can give me some advice, I watered my tomatoes this morning as I usually do, they were all looking quite vigorous and healthy, then I went out this afternoon to start staking them up as they are about 2 foot tall now and I noticed one plant had started to wilt quite noticeably. this morning it was fine and this afternoon it is all saggy, none of the other plants around it seem affected. I started these from seeds and transplanted them outside to raised beds a few weeks ago and they have been growing fine. I have 4 different varieties but I am not sure which one is the affected one as they got mixed up when I transplanted them outside. I hope you can help Thanks very much for your time and effort cheers!
Some reasons for wilt include overwatering, underwatering, are they located in the vicinity of a black walnut tree, and possible wilt diseases. See our publication on tomatoes for symptoms and causes. Looks like a top down wilt. Fusarium wilt is most common; however, verticillium wilt is similar. http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG56%20IPM%20Tomatoe...
and our website http://extension.umd.edu/growit/fusarium-wilt-tomato-vegetables
We cannot say for sure what you are dealing with from your photos. You will have to monitor the plant and your other plants for signs and symptoms. If located in the vicinity of a black walnut, roots exude juglone which can cause wilt. Make sure the plants are adequately watered and there was no root disturbance. If it continues to wilt, pull up the plant and look at the stem and roots. Slice the stem vertically and look for a brown tissue or streaking.
Make sure the roots are not black and mushy.
You can send us additional photos if you notice more symptoms.