Spraying apple trees is crucial to getting good fruit.
I don't really like spraying apple trees with chemicals, but something is necessary to save the trees from diseases. Many insects, fungi bacteria and other pests can make apples unappealing and can even kill the tree. There are many reasons to spray apple trees, so spraying multiple times during the year with different solutions is a must. In order to be spraying the right thing on the trees at the right time, we need to know why we are spraying apple trees. Here are some of the reasons:
1. To prevent fungal diseases
2. To protect against bacterial diseases
3. To kill insects such as codling moth, aphids, etc.
4. To give nutrition directly to the leaves of the tree
5. To stimulate the trees own immunity from various diseases
6. To protect the fruit from sunburn as well as insects and other pathogens.
You can reduce the need for spraying apple trees by doing the following:
First, try to use cultural preventatives.
• Make sure you pick up all the leaves in the fall and burn them, send them off to the city recycling dump, or compost them yourself if you are able to achieve a very hot compost pile.
• Plant scab resistant apple cultivars.
• For codling moth, remove every fallen apple immediately so that it doesn't allow the larva inside to become a moth. Put these fallen apples in the garbage can if they are green. If they are ripe, cut out the wormy part and put it in the garbage can. The rest of the apple can be eaten fresh, or made into applesauce. You can also make bands for your tree out of cardboard strips if the tree has pretty smooth bark. The bands provide a "convenient" place for the codling moth larvae to pupate. These can be stapled to the tree. You must change these frequently throughout the growing season and burn them or put in the garbage. During the winter dormancy, it is possible to find some of these overwintering larvae under loose bark on the tree. I like to knock off the loose bark and see how many of these little buggers I can find and destroy.
A little backpack sprayer is all you really need for spraying apple trees. If the tree is too tall, it will not be possible to reach the highest branches without a tall ladder (dangerous!). If you have a number of trees, then a larger sprayer might be a better option. There are 15-25 gallon yard and garden sprayers that could do the job. It is best not to use a sprayer for both pesticides and herbicides, as there could be herbicide residues in your sprayer that might harm the leaves of your trees.
What to spray:
Ever hear of compost tea? Spraying apple trees with compost tea can help your trees in many different ways. It is a brew made from compost, nutrients like fish emulsion and kelp and molasses, and water aerated continuously throughout the process. If carefully made with good compost it can be sprayed on the trees and on the ground in the fall. The organisms in the compost will help to break down organic matter in the soil and can coat the tree with beneficial organisms to help repel the disease causing organisms.
For disease and pests
Bordeaux is a mixture of copper sulfate and lime. It can be used before the buds come out to kill fungal spores for things like apple scab. Copper can build up and become toxic to beneficial organisms, so spraying apple trees with copper should not be done too frequently.
Sulfur can be sprayed on trees for scab. Use a good sticker with it. Spray when the buds are turning pink just before the next predicted rain. Repeat spraying before rain through the bloom time.
Oil can be used to smother small slow insects and their eggs. To be effective, you need to completely cover the plant - leaves bark and all.
Another oil that has great promise is Neem oil. The Neem oil has pest repellent and insecticidal properties. It interferes with the insect hormone, ecdysone, and inhibits molting. In addition to all this, Neem can also boost the health of your trees. Before buds begin to break, you can spray this on the bark of the tree and the ground right around it. A 1% solution (3.25 oz/gallon of water) will do it, and mix it with a soap emulsifier (1/2 Tablespoon)before adding the water. later in the season when you have leaves out, make the mixture half this strength so you don't burn the leaves.
Botanical Pesticides are plant-derived substances that have insecticidal properties. Neem has already been mentioned. Several botanical insecticides are commercially available. One must be careful with these. Know what pest you are trying to eliminate. That way you can use the pesticide only when and where you need it. They can often be toxic to bees, so be sure to hold off spraying apple trees during blossoming.
Biological sprays are organisms that can control certain pests. Bt, insect viruses, etc. can kill codling moths when eaten by the codling moth larvae. That's the catch. The eggs of the codling moth are laid pretty darned close to the newly forming apple, so the larvae don't have to go far before they can drill into the apple and happily eat apple seeds without being bothered by these biological controls. To use them successfully, one must know how to time the spray when the moth eggs are hatching. Coverage must be complete, and the addition of something tasty like molasses helps to make sure the larvae ingest the Bt or virus. This can be calculated by using the degree day model.