You dont want to wash off the oil at any point, it stays. I try to prune first so I dont waste spray on branches that will be chopped off. Make sure and spray when its the proper temp range out, and concentration. Are you doing a fungicide? Probably a good idea.

I think I might use a fungicide with it.

I do not see any problems by pruning after the oil spray. I would suggest doing a fungucide spray on the peach trees to protect from the curl leaf fungus.Last year was really bad in Northern California. This year I already did spray against that pest. I used Bordeaux Mix that I mixed miself:I used the formula most recommended by gardeners,10-10-100,meaning 10 pounds copper sulfate,10pounds hydrated lime an 100 gallons of water.Of course home gardeners will only use a small fraction of that.I just mixed 0.5pouds of copper sulfate,0.5pounds of hydrated lime and 5 gallons of water.Wat remains can be kept in a bucket with a lid or other container,glass or plastic.Before using the mixture must be stirred for a few minutes.Then spray using a good sprayer.I used a 5 gallon Craftsman sprayer with a stirrer.I could not find any copper sulfate in stores around here.California law is too limiting and restrictive. I bougt it on ebay from out of state.Just follow the safety recommendations.See them on internet for information.I am from Europe and I grew in the farm.Also my family used to have vinyards.Bordeaux mix always worked against fungus invasion.Jim

Ready mixed Bordeaux is not nearly as effective as your fresh mixed. The other reason it is not used more is the staining of whatever it touches. California does not prohibit its use and it does remain effective through the rainy weather better than other fungicides. Al

I also have another question when you spray an insecticide onto a fruit tree in summer for eating insects(not anything to do with dormant oils)should you rinse off the insecticide after a certain number of hours. Because last year I sprayed my peach tree with an insecticide for the pests, I did this in the evening so no sun. Then several days later all its leaves fell off and it died. Srry for putting it in this post but I thought it would be better than starting a new one.

No, you don't have to rinse off pesticides. You do, however, have to use them in correctly measured solutions. It sounds to me like you sprayed too high of a concentrate and killed the leaves. I'd read the directions carefully again and see if you may have made a mixing mistake. If not, I'd not use that particular pesticide again.

Peachguy:

You have to tell us exactly what insecticide you used and its chemical components (listed on the label). "An insecticide" is just not specific enough for anyone to make a judgment. The application of a strong enough copper compound during the growing season could very well make a tree lose its leaves, as well as improperly mixed insecticides of several types. It should never be necessary to rinse off a pesticide once it has been applied.

It would be very rare, however, for a single application of an insectide, even badly mixed, to actually kill a tree. So something else may be going on that is unrelated to your pesticide application.

Don Yellman, Great Falls, VA

I appreciate the "calistoga" member comments. With respect to the copper sulfate not being prohibited in California I was quite surprised. I tried to get it here in the Bay Area in many different stores and nurseries like Homedepot, OSH, Lowes,Summer Winds nursery outlets, and many privately owned nurseries and everybody told me the reason they do not carry it was because the laws in California were too restrictive and did not allow the sale of copper sulfate to domestic consumers.However I did not check with a State Government Agency on the matter. I appreciate your feed back .Thank you.Jaime.

jmmedeiros, I agree you cannot buy Bordeaux mix from garden center or most retail nurseries. The reason is the ready mixed is not very effective and the staining is unacceptable for most home gardeners. The Copper Sulfate and the Lime is sold separately at your local farm supply and is mixed when you are ready to use it. Al