My blueberry bush has lost most of its leaves. The fruit and flowers are still on the bush! Will this affect the fruit as it ripens? The bush is in a planter box and gets sun.
Blueberries will very quickly drop their leaves if the plant becomes stressed. It is possible the plant has dried out at some stage or has become waterlogged and has a root rot problem which can happen if the container has been sitting in water. Unfortunately, you will need to remove all the fruit because the plant has gone into shock and trying to fruit now will add more stress and possibly kill it.
If the plant has dried out, begin watering it regularly and deeply, and modify to suit the conditions e.g. less water if lots of rainfall or more if drier weather. If the plant has been waterlogged, get the container up off the ground so water can drain out (little feet are available from your local garden centre). It would also be worth giving it a spray with a fungicide. Finally, add a light side dressing of Daltons Citrus & Fruit Fert. With reasonable care over the next few months the plant should re-clothe itself with new leaves.