I seem to recall that in Texas, we should be spraying with dormant oil spray before the peach trees bud out, but cannot remember. Can someone advise? Thanks!
Yes, it is time to be thinking of dormant spraying your peach trees just as the buds begin to break.
But dormant oil, while effective against a narrow range of insects that overwinter as eggs or larvae in the cracks and crevices of the trees, is not the dormant medicine that is usually most important to stone fruit trees. I use oil spray on apples and pears to control aphids, scale insects and psylla, but the most serious problems on my peach trees are diseases that are fungal or bacterial in origin. Peaches are also subject to insects like the oriental fruit moth and the plum curculio, but these cannot be controlled with dormant sprays and must be dealt with during the growing season since their origins are normally away from the tree itself and sometimes beneath it.
The most troublesome diseases of peach trees are bacterial spot/bacterial canker, peach scab, brown rot, and the leaf disease called peach leaf curl. All of these diseases can overwinter on the trees, especially in a mild climate such as yours. One traditional dormant compound for peaches is lime/sulfur spray, but I have found copper sprays to be more effective, especially against bacterial diseases. My current favorite is Kocide, a strong copper formulation sold as a soluble powder, but there are other copper sprays sold as liquids. It would be nice if we could use copper all season long, but we can't since it usually causes serious leaf damage. So the time to copperize your trees is now. You can, if you like, apply dormant oil and copper as a mix, and I often do this when I have a good supply of leftover oil spray. Oil spray cannot, however, be applied with lime/sulfur.
Pruning of peach trees is about as important to fruit production as any spray you can use. I begin pruning right at fruit thinning time, opening the center, removing any crowded branches, as well as any top growth that prevents the sun from striking the fruit, and often return to prune the trees again about 4-6 weeks later if they develop too much bushy growth. Peaches need lots of air circulation, particularly in warm, humid climates, and sunlight is essential to developing large, healthy peaches. I do not dormant prune my peaches, but make sure you remove any mummies from the trees and keep the area around the base free from leaf litter and debris that could harbor disease.
Don Yellman, Great Falls, VA