Apples are one of the most popular fruits in America. Many a backyard gardener has an apple tree or two, or even a small orchard, and these trees need consistent care to thrive and grow fruit. Apple trees can be prone to disease and pests. The most common diseases are apple scab, powdery mildew and fire blight. Aphids and other insects can be problem pests on apple trees. There are a few pesticides approved for use in edibles but the safest way is to use only organic products. You must know when and how to spray to make the best use of these.
One of the best protections for your tree is to plant a resistant species. There are insect- or disease-resistant varieties. It is best to know what maladies apples are likely to succumb to in your region, as every area has its most prolific pests and diseases. Trees in the Pacific Northwest will run into problems with various fungi and powdery mildew more often than those in the Midwest. Following zonal information is another way to minimize spraying as a healthy, unstressed tree can fight off any problems more easily. Rootstock is important as well, with some rootstock used to highlight a control or resistance feature. Research is the key.
In late winter, just as the buds begin to show a little green, you should begin insect control. Spray insecticidal oils when temperatures are between 45 and 55 degrees Fahrenheit. Make certain spraying is done by noon so there is adequate drying time. Just before bud clusters show any flower color is time to spray insecticidal soaps to control hatching insects. If caterpillars are a problem, this is also the time to administer Spinosad. Vigilance on insect spraying is crucial during the pre-emergent period because there should be no spraying while flowers are open to protect honeybees.
When the first green tips peek out of the silver leaf spurs, you know it is time to start fungus management. The predominant problem is powdery mildew. Spray with lime sulfur, making certain to cover tops and bottoms of leaves. The spray needs to dry before evening, so it's best to apply after dew dries up but before noon. Do not spray Delicious apples with lime sulfur as it will cause blossom drop.
Preventative Spraying after Bloom
Ten days after the flowers have dropped their petals it's time to spray for pests that will infest or kill the apples. Coddling moths are the biggest culprit and plants should be sprayed every six weeks with Spinosad. Spraying should continue until early September. Affected apples should be removed so the larva cannot emerge and reinfect the tree. Apple maggots are also a problem after bloom and can be treated with Kaolin clay or exclusion bags, which are individual bags to protect the apples.
Methods of Application
You can apply sprays with a hose-end sprayer. Follow the manufacturer's instructions and use a different plastic container for each type of spray to avoid contamination. There are also industrial tunnel sprayers and misters. Tunnel sprayers can be rented and give more control. Misters will give even coverage but it is hard to control where the mist goes, and it can drift to plants that do not need the spray. It is best to spray when there is no wind to reduce drift, which can be harmful to other plants.