I planted three 6 foot apple trees last September (Fireside, Golden Delicious and Pink Lady). By mid-July, the leaves from the lower branches of all three trees have almost all disappeared, although the branches are not dead. The upper branches seem to be doing well and one of the trees even has 3 apples on it. Is there cause for concern about this leaf loss on the lower branches? Is there anything I should be doing?
Inspect the leaves and the tree for any signs of pests or disease on the leaves to determine if the leaves drop due to these issues.
Here are some links that will help you know what to look for and how to treat you trees.
If you rule out disease or pest issues, move on to soil; watering and nutrients your tree needs.
http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/managing-apple-scab/
https://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-diseases.htm
https://www.gardeningknowhow.com/edible/fruits/apples/no-fruit-on-apple-trees.htm
https://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-planting.htm