Basic Insect and Disease Control for Apples

Table of Contents

1. Introduction
2. Green Tip
3. Bloom
4. Post Bloom (calyx)
5. Summer Sprays (when fruit is forming)

Introduction

In Ontario today it is very unlikely that quality apples can be grown without having some control over insects and disease. All apple growers, even organic and ecological producer, must confront this problem. It is difficult to know exactly what to do for pest control, and yet keep pesticide usage to an absolute minimum. The growes facing the greatest confusion are not the large commercial growers, and not the backyard gardeners, but they fall somewhere in between. Hopefully, this guideline will help such growers better understand the basics behind effective insect and disease control in apples.

The crop protection materials and timing of application used in this explanation are only suggestions. There are many commercial materials available that will do the job equally as well. For simplicity, only two products that do not require a Grower Pesticide Safety Certificate (as of 2001) are mentioned. Whatever materials you choose to use, BE SURE TO CAREFULLY READ AND METICULOUSLY OBEY ALL LABEL INSTRUCTIONS ON THAT PRODUCT. A pesticide is only as good as the care to which it is mixed and applied.

When spraying trees, thorough coverage of all foliage and fruit is essential. It is necessary to apply a spray to the point of run-off to accomplish this. This can be achieved by various devices, from a hand sprayer (knapsack), to a power sprayer that can be attached to motorised garden equipment. When applying pesticides, avoid spraying during brisk winds or during rain as coverage will be poor and so will retention of the product in the tree.

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Green Tip

The first problem of the season, and the one most often overlooked until it is too late is apple scab. There are now apple varieties that are resistant to this disease and do not have to be sprayed for control of apple scab. In the home garden situation the use of such varieties (cultivars) will greatly reduce the need to apply pesticides for production of clean fruit. Apple scab is caused by a fungus that thrives during wet weather. To control this disease a protective fungicide layer must be maintained over the leaves and fruit during the season. This protection must start when the first green tissue just begins to peek out of the buds. It is better to spray before a rain so there is fungicide protection present to stop any potential infection. Begin spraying with a fungicide at green tip and repeat every 7 days until the blossoms open and the tree is in flower. During extended periods of rapid growth and/or wet weather, it is advisable to apply apple scab control every 5 days as scab pressure can increase tremendously under these conditions.

For apple scab control, use a fungicide such as Dikar WP at the rate of 1 kg/500 litres of water. Dikar WP also has the added advantage of controlling another fungus disease called Powdery Mildew and suppressing an insect called the European Red Mite. If caterpillars or worms can be seen on the foliage during this pre-bloom period, add .45 kg of the insecticide Imidan 50% WP to 500 litres of the Dikar WP and water solution. This needs to be done only once before bloom when the caterpillars are very small.

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Bloom

To keep apple scab under control during this period, a fungicide (Dikar WP) must still be used every 7 days. However, avoid the use of a fungicide during the day when the bees are flying. Spray early in the morning or late in the evening when the bees are not in the blossoms. NEVER USE ANY INSECTICIDE DURING BLOOM OR BEE POISONING MAY RESULT.

Post Bloom (calyx)

When all of the blossoms have fallen and bees no longer are in the blossoms, apply a spray mixture of Dikar WP plus Imidan 50% at 1 kg and .60 kg/500 litres of water, respectively.

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Summer Sprays (when fruit is forming)

The next spray applied 10 to 14 days after the calyx spray should be Dikar WP at 1 kg/500 litres of water. For best results, fungicides spraying should continue on a 10 to 14 day interval up to the middle of July. Scab this time of year, if present, will appear as brown, sooty spots on leaves and fruit. If scab is visible, continue fungicide applications on a 10 to 14 day interval until the middle of August. Dikar WP cannot be used within 45 days of harvest. If fungicide is necessary within this time frame, Captan 50 WP (a Grower Pesticide Safety Certificate is required to purchase and use Captan) could be used at the same rate as Dikar WP.

To control insects that will damage the fruit it will be necessary to continue to apply Imidan 50 WP at .60 kg/500 litres of water every 18 to 20 days until the middle of August. FRUIT SHOULD NOT BE EATEN UNTIL 7 OR MORE DAYS HAVE ELAPSED SINCE THE LAST IMIDAN 50% WP SPRAY WAS APPLIED.

Occasionally, an insect or disease problem will appear that cannot be controlled by this simple program. Instead of giving you all of the problems that could occur and a complicated protection program, it is a better plan to consult your local garden expert if a problem should appear.

It should be noted that insect and disease control will be difficult if unsprayed trees of apple, crab apple, quince or hawthorn are growing nearby.

NEW TREES: If the apple trees are too young to bear fruit, use a fungicide every 7 to 10 days until mid-June and add an insecticide only if visual foliage damage from insects is evident.

NOTE: Under most conditions this simple program should give all the insect and disease control necessary to growing a rewarding crop. Remember, this program is one of many that can be used and is offered only as a guideline to help you better understand basic insect and disease control.

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