June 6, 2023
Anyone growing an apple orchard, whether it is commercial in size or just for home use, cannot wait for harvesttime. That’s when you get to taste the “fruit” of your labors.
However, there is plenty of hard work and management all year long that goes into those apples. Insects and disease issues don’t take a day off, so even in the fall and winter months, there is work for orchardists to do.
The best way to make sure your apple trees produce fruit that is free of disease and insect problems is to encourage a healthy tree to begin with. Plant disease-resistant cultivars, mulch the base of trees and plant trees in proper, well-drained soil conditions.
Aaron Steil, Iowa State University Extension consumer horticulture specialist, suggests cleaning up downed fruit and leaves in the fall to help eliminate potential inoculum and overwintering eggs and larva that could cause problems during the following growing season.
Keep the weeds down to cut back on pest habitat and overwintering locations. Prune the trees properly, removing diseased wood and promoting good airflow among well-spaced branches.
Much of the spraying schedule for apple trees is accomplished early, from dormant stage through petal drop. But after the last petal from apple blossoms has hit the ground, a regular spraying schedule is important, with spray required generally every seven to 14 days or so — to combat issues such as apple scab, powdery mildew, plum curculio or apple sawfly.
The spray schedule and formulations are outlined on the product labels, so Steil recommends always reading and following label directions.
For most apple growers, there are three major diseases to watch for, including scab, cedar apple rust and fire blight. There are other disease issues, but most of those are more cosmetic, Steil says.
Here is a look at some types of spraying:
Home orchard spray. “The best place to start for most homeowners is with the home orchard sprays,” Steil says, because they are formulated to control apple pests and diseases — combining mixtures of one or more insecticides and fungicides.
“These are by far the best for home orchard owners because the spraying schedule is there on the label for the whole season,” he notes.
The downside is that you may be applying products that are unnecessary for the problems your trees are having, and these chemicals may unwittingly harm some beneficial insects and pollinators. The best time to apply these home orchard sprays is before or after the bloom period — or at dawn or dusk when bees, for instance, are less active.
Organic spray. A summer spray schedule, using organic sprays to help control insects and diseases, may include spraying sulfur or potassium bicarbonate every seven to 14 days if a disease is observed, stopping 30 days before harvest — or spraying pyrethrum, spinosad, insecticidal soap or neem when an insect pest is observed, following the same basic schedule.
Nonorganic spray. A spraying schedule using more traditional nonorganic sprays for control in the summer might include spraying captan or sulfur every 10-14 days for scab and stopping 30 days before harvest — or spraying carbaryl, malathion, indoxacarb, acetamiprid or spinetoram for apple maggot and coding moth, using the same schedule.
Traps and bagging. Steil says that traps like sticky cards inside small tents with pheromone lure or red spheres or yellow cards using color and shape to lure apple maggot flies, for instance, are occasionally used in hopes of eliminating pest issues. Generally, Steil says these traps are best used as monitoring stations to let growers know of the presence and potential population of individual pests.
Other methods of alternative pest control may include bagging fruit with a mesh bag to prevent insect damage, but he notes that for larger orchards or even highly productive trees, this process may be time-consuming and expensive, depending on the commitment and labor availability of the operation.
Learn more at the Iowa State Extension website.
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