A friend asked me to talk about spraying fruit trees. There are many opinions about pesticides and fungicides and whether to use them or not. This is not about what to use. This is about when and why and how to use whatever product you see fit to use. Remember that all pesticides, conventional or organic, are poisons. Their toxicities may vary but, they are all poisons.
Why Spray at all?
Spraying fruit trees is done to prevent damage, material or cosmetic that interferes with the usefulness of the fruit or the health of the tree. There are dozens of insects that feed upon trees and tree fruit. There are also dozens of diseases and fungi that damage trees and tree fruit either materially or cosmetically. Insecticides are for the insects and fungicides are for the fungi.
The first question to ask yourself before you spray your trees is what are my goals? Do I want fruit that looks like the fruit in the grocery store or do I want fruit that may not be perfect but is still usable at home? Do I want my trees to look good all summer or just good enough to ripen the fruit?
The answers to these questions will determine how much you have to spray and what kinds of products you will have to use. Large perfect fruit will require much more attention than the fruit to make jams and jellies.
Thought should be given to what you plant before you ever get started. How big do you want your tree to be? Dwarf trees produce just as much fruit and are manageable from the ground. A russet fruit like this Korean Giant Pear will need less care to get an acceptable fruit than a yellow late fall ripening apple. There are early ripening fruit varieties that ripen before the insects really get going. There are russet fruits that resist the cosmetic fungi that require repeated sprays.
Stone fruits, Peaches, Plums and Cherries, are much more susceptible to insects than say, Pears.
Some varieties are more resistant to leaf diseases like Cedar Apple Rust or Peach Leaf Curl or even Fireblight. Read about the varieties before you plant and buy trees from a reputable nursery. Look beyond the pretty pictures and study the strengths and weaknesses of each tree before it is planted. This will determine to some degree how much spraying will be necessary.
Take the time to learn to prune your trees properly. Properly pruned trees will be more productive and less prone to disease and insects. A properly pruned tree will be open enough for you to get good spray coverage. Good spray coverage is key to good control.
When to spray?
When to spray is based on knowing your enemies. Before you begin spraying you trees you must know what you are spraying them for and when the pest is active. There is no need to spray for something that is not there. Spraying then is a waste of time and money.
Many fungal diseases and Firebight which is a bacterial disease can be dealt a serious blow by spraying an agricultural copper spray in late February. Copper will kill the inactive spores that are waiting for the leaves to open and conditions to be right for infection.
DO NOT SPRAY INSECTICIDES DURING BLOOM! DOING SO WILL KILL THE BEES YOU NEED TO POLLINATE THE FRUIT! This should be common sense but it must be said. Fungicides and pesticides can be used before blooms open and after petal fall. Petal fall is when 80% of the petals have fallen from the blooms.
Curculio starts to do damage shortly after petal fall. It is active for 4 or 5 weeks after petal fall. Sprays for it will take care of the first round of Codling Moth.
Fireblight should have been taken care of by the dormant copper spray. Fireblight attacks through open tissue. Hail when the trees are actively growing is the second opportunity for infection after bloom. Agricultural Streptomycin is the only thing that will slow it down
There are a series of insects that damage fruit through the summer. Your state extension service should have a publication that will guide you to when these insects are active and what to spray them with. Study these insects life cycle and you will be much better able to deal with them. One of the best orchard men I ever met spent several years trying to grow organic fruit in Indiana. He failed at that but, he discovered that by knowing the pests, he could reduce his pesticide use by 90% and still get good results. KNOW YOUR ENEMY.
Cosmetic fungal diseases called summer diseases, Fly Speck and Sooty Blotch do no harm to the usability of the fruit but they are unsightly. They can be prevented by a bi weekly fungicide from June until harvest.
One more hint, Spray at night or in the late evening. Night time is when the insects and fungi are most active and vulnerable. No need to spray when the enemy is not there. Many pesticides begin to break down in sunlight so, if you spray in the morning and the sun shines on the spray material all day, it may be half as effective by the time the insects and fungi come in contact with it.
How to spray?
Spraying fruit trees effectively depends on the size of the trees and how many you have to spray. One or two in a yard will require different equipment than 20 or 30 on a small farm. How to spray is all about coverage. You cannot get good coverage when the wind is blowing over 5 miles per hour. Another reason to spray at night, the wind is usually the lightest after dark. You want as fine a mist as possible and enough pressure to reach the whole tree. It is much easier to get such coverage on a 10 foot tall dwarf tree than a 30 foot tall standard tree. Leaf surfaces should be coated top and bottom to the point of dripping. There are many types of sprayers out there and all will do an acceptable job if you learn how to use them.
When spraying just a few trees, it may be difficult to measure out the tiny amounts of material needed. With pesticides and fungicides more is not better. Too much product can make you sick or burn the leaves on the trees. If you have just a couple of trees, you might want to use premixed material that can be diluted into one or two gallons.
What to spray?
I am not going to get into the organic versus conventional argument. Both sides have pluses and minuses. I will let you decide what is best for you. I would recommend you getting a private pesticide applicators license through your counties extension service. This will require you to take a class in how to apply the sprays and give you some familiarity with the products available. It will also teach you how to properly dispose of unused products. An applicators license will allow you to purchase products that are more effective than what is available over the counter.
Fungicides must be rotated to prevent the buildup of resistance. Pesticides are somewhat insect specific. What works on beetles may not work on moths and vise versa.
There are some non toxic products available that act as deterrents for insects and fungi.
You are responsible to educate yourself about the materials you are going to spray and the responsible use of those products.
This is a brief comment on a broad subject. Growing fruit successfully is one of the most difficult arts in agriculture. If you can master tree fruits, you are truly a master gardener.
There is a book “The Orchard Almanac A Seasonal Guide to Healthy Fruit Trees” by Steve Page and Joe Smillie that cover the topic more in depth.
This as well as your states extension service fruit growing guides will take you farther down the path of successful fruit growing.