How can I control apple tree borers in organic production?
Answer: Organic apple production has many challenges, and controlling trunk borers is one of the most serious. Left unchallenged, borers can kill young apple trees before they ever get started bearing fruit. And older trees are not immune from the ravages of these pests either.
The first line of defense is maintaining tree health, especially providing adequate water. A tree in good health and growing vigorously can literally drown or cast out a young borer before it really gets started. But this is an imperfect, though important, management technique.
A surer control is to wrap the trunks with window screen from the ground to about 18” high. The top should be tied off snug with twine or something biodegradable and the bottom needs to be tight against the ground (throwing a little soil around the bottom can help). We don’t want to girdle the tree so wire is not a good tying material and even the twine can be too tight, so use some common sense here or plan to come back later and loosen the twine.
Even wrapping with screen is only about 95% effective, so it’s still a good idea to inspect your apple tree trunks for borers once or twice during the growing season and look for the tell-tale little pellets of orange-red sawdust at the base of the tree.
ATTRA has several resources that will help you learn more: