Q.plum tomato plant
I am in Ankara, Turkey. I have a plum tomato plant in a large pot on my balcony. It was doing fine and then suddenly it wilted. It recovered somewhat during the night, which is quite cool here, but now it is again wilting. Any ideas? I suspect some type of root borer.
Day time wilting with a recovery in the evening usually indicate that it needs water.
Daily watering is needed for container plants and even twice a day when the temperatures are above 85 degrees.
Also if the container is not large enough the roots can't take up enough moisture and nutrients.
If you see yellowing, spotted leaves, or leaves curling this can indicate insects or disease.
Here are a few links for you with care information.