Dormant oil for Peach trees

The last few years, our peaches developed a small white worm on the inside. Yuck!

Supposedly spraying them with dormant oil in February (when the tree is dormant before bud bloom) will help with this.  So today, I mixed three ounces of dormant oil with one gallon of water and sprayed down both trees.  I am not highly convinced this will work, but I thought I'd give it a shot...