by 
The Curious Bag
-
<h4 class="dechead">On One Hand: Early Spraying
According to the Department of Horticultural Science at North Carolina State University, "A spray to control fungus problems should be applied when the first sign of green tissue appears." They also suggests spraying a horticultural oil to suffocate insects, mite and aphid eggs at the same time. They recommend spraying every five to seven weeks after that.
On the Other: Midterm Spraying
GardeningTips.Today.com suggests waiting until the first buds appear and begin to show color, but are not yet blossoming, before spraying. It suggests that you don't spray again until "[90 percent] of the apple blossoms have fallen off the apple tree." Trees are then sprayed every two weeks until just before harvest.
Bottom Line
Spraying early to prevent insects at first greening, and then only occasionally after that, will reasonably protect your apple trees from insect infestation or disease damage, but will not subject your tree and its fruit to a lot of chemicals throughout the season.
Source:
Department of Horticultural Science at North Carolina State University
RELATED QUESTIONS
Copyright 2023, Wired Ivy, LLC