Could you tell us what affected our peaches last year? What caused these rotten spots that started showing up just before harvest?

Last year my peaches had what I believe to be a fungal disease that put dark freckles on our peaches. I purchased Daconil spray for the peaches. Will Daconil help the peaches? Will it work on apricots as well? And the instructions said to spray right after pedal fall, when exactly is that?

The decayed spots look like late-season Coryneum blight. Coryneum blight can cause rough, raised speckles on the skin of peaches and apricots if the infection occurs early in the season while the fruits are still green and firm and sunken, necrotic spots if the peaches are at the ripening stage when infected.

Coryneum blight is a fungal disease that infects stone fruit trees and their ornamental relatives. It is most common on peaches and apricots. Coryneum blight causes necrotic spots on the leaves that dry and drop out, leaving holes. Infected buds die, and twigs can be girdled and killed when that happens. Early season infections on younger fruits can look like crusty speckles or bumps. New infection on nearly ripe fruits can cause sunken, necrotic spots but may not always show up on leaves.

There are a few things you’ll need to do for your trees to reduce or prevent the problem this year.

• Take steps to prevent sprinklers from hitting the canopy of the tree.
• Prune out and dispose of dead twigs, twigs with dead buds, twigs with dark, sunken bark.
• During the summer, protect your fruit with Captan or a fruit tree fungicide with the active ingredient myclobutanil when rain is in the forecast.
• In the fall when 50% of the leaves have dropped from the trees, spray the trees with a fungicide that contains the active ingredient chlorothalonil.
• Clean up thoroughly under the trees once all the leaves have dropped.
• In the spring, spray the tree again with chlorothalonil between petal drop (the stage where the petals drop off the blossoms) and “shuck split.”

The recommended controls for peaches are also effective for apricots.

Daconil has the active ingredient chlorothalonil, the one recommended for spring and fall control. You can use it up until shuck split. After that point you must stop using anything with chlorothalonil in it until after the peaches are harvested. If you need to protect your fruit during the summer because rain is in the forecast, you can spray myclobutanil (Spectracide Immunox, etc.) or Captan. You can use chlorothalonil (Daconil, etc.) again for your fall spray.

Our tree pruner/arborist noticed some old peach tree borer activity on our peach tree. What can we do this year to protect the tree?

If the old damage your pruner noticed was in the lower foot or so of the trunk, a Greater peachtree borer, a clearwing moth, is most likely the culprit. If the activity was higher than that above the soil line, the problem was caused by something else.

Greater peachtree borer eggs are laid on the lower trunk of stone fruit trees. When the eggs hatch, the larvae feed under the bark. Over time, their feeding can girdle the trunk and kill the tree. Larvae can sometimes be killed by pushing a wire into the entry hole, but prevention is the most effective control.

For Greater peachtree borer prevention, protective trunk sprays are needed on the lower 12″ of the trunk beginning in mid-to-late June once adult borers become active. The beginning spray date varies from year to year depending on the weather because insect development is closely tied to temperature. Recommended spray dates each year are included in our free email advisories and you can subscribe to our advisories here https://pestadvisories.usu.edu/subscribe/.

Your protective sprays must be repeated to be effective:

• Once every four weeks until about early September if you use permethrin
• Once every three weeks until about mid-September if you use Spectracide Triazicide
• Once every 7-10 days until late September if you use Spinosad or pyrethrin (organic options- spray to the point of runoff or saturation).

Each time you do your protective spray you should also spray the soil around the trunk heavily to protect roots in the area just below the soil. Sprays should be applied to provide protection until the end of September.

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