After all the nuts drop off the tree and the leaves fall off, he needs to get ready for next years walnuts by spraying dormant oil on the whole tree. Wear old long clothes and mask, goggles, gloves & hat. Keep children & pets away until this is dry. Don't spray on windy days and don't spray if it is going to rain. This smothers any eggs that have been laid on the tree....in the spring it has to be sprayed according to the schedule on the container. We spray up to the bud stage....after the bud stage, we only spray the trunk up to & under the first branch. We need bees for polunation. Good luck with your walnut tree.