Question
I have a white powder residue at the base of my two year old crabapple tree . The tree looks healthy and is really beautiful right now . I sure would like to keep it that way. Also , what should I fertilize it with ? I thank you so much for your help.I live in MS.

Answer
Fertilizer the tree in mid-April. If wait to long to prune you can potentially cutting of flower buds. If you fertilize too late in the season it confuses the tree. New plant growth could continue when it is suppose to be becoming dormant for the winter months. Rule of thumb never fertilize after July 1st especially in the cooler climates. Use 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good.

I am  not sure what the white could be. It could be Flathead Apple Tree Borers.  Flathead Apple Tree Borers tunnel under crabapple bark at or near the soil line. They can girdle (eat completely around the tree just inside the bark) and kill the tree if left undetected. A clue to their presence is a pile of sawdust at the base of the tree.

Borer attack can generally be avoided by promoting healthy tree growth and by preventing bark damage from lawn mower.

I would spray the lower trunk from ground level to about a foot up the trunk with an insecticide called Merit. This will be absorbed by the bark and kill the insect in the trunk. Check with your local nursery from Merit.