Whenever you prune, it is most important that the tools you use must be completely sterile, particularly if you hire someone who may be bringing tools that just worked in another garden. The transfer of fungi, bacteria, and virus kills more trees, than just about any other cause.

Be it Lysol, Chlorox, or TSP just make sure that however works on your tree uses something to sterilize their tools. Even after warning a customer of mine, she hired someone prune her anthracnose infected plants. He then went on and pruned everything else in her garden. The pruning was great -- the spread of the disease was not. Worse yet she had made a practice of composting everything.

Diseased limbs and leaves should always be burned and never put into the compost bin. Some fungal diseases can also be transmitted through the soil and up into the tree.

When you are doing the actual pruning in your orchard, keep your bucket of clorox (at least a cup per gallon) or TSP mix where you are working, and disinfect your tools every few minutes. This is because you can cut out something like an apple tree limb, which is infected with a disease like 'fireblight', and quickly transfer it to another part of the tree, or another tree.

Bacterial problems are or may be controlled with such disinfectant dips -- viruses are not. Read also that Clorox will affect the life expectancy of the tool, same as would alcohol and fire-heat treatments. Oil your tools to prevent them from rusting.

As far as I know a two-minute dip in Clorox will not kill viruses. (This is very worrisome as it is a 'proven' tool (one in three) usually used in killing pathogens in wastewater treatment.)

One other and very safe method (used in orchid houses) is to leave your tool to soak overnight in a mixture of water and TSP. Tri-Sodium-Phosphate. This according to their experiences is one of the best anti-virus methods of treating tools. Best of all TSP has no effect on the tool whatsoever. Keep dipping the tool as you use it. Stop and let the tool rest in the solution between trees. (One ire of mine is seeing "Pruning experts" not use ANY method of sterilization at all!)

Virus are very hard to control by any chemical means! Funguses such as some armillaria , or fusarium, or galls in trees can be controlled by Clorox or Copper fungicides etc., so can bacterial cankers, anthracnose or pseudomonas.

Some fungus diseases or bacterial ones need to be controlled by very specific products; Verticillium wilt should be treated by pruning (and then burning the limbs) to living tissue and the wounds painted by a fungicidal product such as thiram or benomyl. Repeat two weeks later.

Virus's and trees ... call in a professional! AND PRAY!

________________________________________________________________

Much was discussed in this about "sterile", "disinfectants, Clorox, Lysol etc. I would also like to put in a plug for the native mycorrhriza and bacteria. I personally believe in borrowing some soil from a healthy and productive tree and seeding that new planting area with some of it. Beneficial soil organisms are sometimes destroyed in all of our spraying and tinkering with nature. In the same vein adding some healthy compost is also a great idea to make that new tree happier.
Over-spraying and over-fertilizing can not only negatively affect groundwater but also the very soil itself.

As for the right way to do things.

I will always remember one lesson taught to me a few years ago. We have a local vintner who was teaching a course on managing the vineyard. I wanted to learn more about pruning grapes so offered to help him in exchange for a few sips at the end of the day.
After pruning a rather large cut he took his thumb, spit on it, rubbed it in the dirt and rubbed it on the wound. "To make it heal better!" HUH! Well, not that I recommend this, but he knew his soil and he was confident of what was in it.

Herbert Senft

Who even flosses with TSP