I have a Macintosh apple tree about six or seven years old. I use horticultural oil after the last frost and early on it seems to do quite well. Every year I get lots of apples but by the time they get to be the size of a quarter or so they all fall off. How can I prevent that this year?
I would recommend fertilizing this tree once a year. This sounds like a phosphorus deficiency or maybe even a little potassium deficiency as well. Fertilizing once a year with an apple fertilizer will ensure that the tree has no deficiencies. Here is an article that will help: https://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-feeding.htm
Can we grow McIntosh apples here in Lincoln county?
The USDA says you are in Zone 7A. Here are a couple of helpful articles. The first article mentions McIntosh as one of the fruits that can be grown in your region. The second article is additional information about growing different types of apples in your zone.
https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-7/growing-zone-7-fruit-trees.htm
https://www.gardeningknowhow.com/edible/fruits/apples/growing-mcintosh-apples.htm