How can I revive my wilting silver birch trees?

I have a few silver birch trees that are about 2-3 years old and have been doing well. Recently, I noticed that the leaves on one or two of them are turning yellow, and one tree is wilting badly, with about one-third of the tree hanging low. I tried watering it, but it doesn't seem to have helped. What could be causing this problem?

It is common for birch trees on dry ground to suffer in mid-summer, especially if the soil has dried out at depth in spring and has not been replenished by rainfall. However, if the affected tree is also exuding a tell-tale exudate from the stem, it may be suffering from bacterial soft rot, which cannot be treated. Another possibility is root damage caused by chafer larvae, which is usually temporary and may not trouble the tree again. Unfortunately, chafer larvae are difficult to control, and any damage they have caused is already done. Since watering an established tree is not very effective, especially if it is not planted in suitable ground, you may need to take some other measures to help the tree recover.