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Garden Help Desk: Protecting your peaches and growing good garlic

By USU Extension - | Sep 18, 2021

There may be just a few coryneum blight infections on a peach, but it isn't unusual to see many infections on one peach. (Courtesy photo)

What happened to my peaches? Everything looked good last month, and the peaches were beautiful. Now most of the peaches have dark spots and some look like they are spoiling under the spots.

My peaches looked nice a few days ago when I picked them and now they have rotten spots on them. Can you tell what’s wrong with them? Will they be safe to eat if I trim out they bad spots?

This looks like Coryneum blight. These deep decayed spots develop when nearly ripe peaches become infected. When peaches are infected earlier in the year, while young and green, the infected spots are small and look/feel like scabby freckles. Your peaches were probably infected during one of the rainstorms last month.

Coryneum blight is a fungal disease that can infect stone fruit trees and their ornamental relatives, but 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. Infection on the fruits that can look like crusty freckles or bumps if the infection occurs while fruits are young, or the disease may look more like deeper decayed lesions if the infection occurs on nearly ripe fruit. Sometimes fruit that looks normal will show symptoms of the disease after harvest. The fruit may be more difficult to peel, but it is still safe to eat.

We normally have a monsoon season from late July through August. A rainy, drizzly day along with mild temperatures can provide the perfect conditions for the spread of Coryneum blight. The fungus can spread quickly from infected fruit to healthy fruit.

Coryneum blight can show up in just a few days after infection. Fruit that looks fine at harvest may show symptoms within a few days. (Courtesy photo)

There are a few things you can do for your tree throughout the growing season to reduce or prevent this problem next year.

  • Take steps to prevent sprinklers from hitting the canopy of the tree.
  • Prune out and dispose of dead twigs, twigs with dead buds, and twigs with dark, sunken bark.
  • In the spring, spray the tree with chlorothalonil a few days after the petals drop from the blossoms, but before “shuck split.”
  • During the summer, keep an eye on the weather forecast and use protective sprays with the active ingredient myclobutanil or Captan when rain is expected.
  • In the fall, spray the tree with a fungicide that contains the active ingredient chlorothalonil or copper when 50% of the leaves have dropped from the tree.
  • Clean up thoroughly under the tree once all the leaves have dropped.

There are several different products you can use as protective sprays, but each has its own limitations. Copper spray can damage fruit; limit its use on fruit trees to before leaf-out or after harvest, but not while there is any fruit on the tree. Chlorothalonil can be used before shuck split and after harvest but not during the summer growing season.

Does it matter whether I plant my garlic now or can I wait until late fall?

Garlic can be planted anytime between the middle of September and early November and will do well if it’s planted somewhere in that window of time. Garlic will grow if it’s planted in the spring, but the quality and yield will be poor.

Right now, you have an opportunity to do the good soil preparation that will give your garlic plants what they need to thrive and reward you with a good harvest next summer. Garlic does best in soil that is well-drained and rich in organic matter. Work an inch of compost into the upper few inches of soil where you’ll be planting your garlic if you haven’t added any organic matter for the past year or two.

A monsoon-season rainstorm in late summer can easily spread Coryneum blight throughout a home orchard. Preventive fungicidal sprays will help protect your fruit when rain is in the forecast. (Courtesy photo)

Carefully separate large, healthy heads of garlic into individual garlic cloves but don’t peel them. Plant the largest cloves, pointed end up, about 2-3 inches deep and about 4 inches apart. If you’re planting multiple rows, or planting your garlic in a block, make your rows several inches apart.

Shallots can be planted at the same time you plant your garlic. Plant them like you would garlic-unpeeled, pointed end up, and about 2-3 inches deep, but space them a little farther apart.

You won’t see it happening, but during the rest of the autumn your garlic cloves will be busy developing the root system your garlic plants will need next spring. Water deeply as the season warms up, provide nitrogen fertilizer in mid-April and late May and you’ll have a nice supply of garlic by early July.

Garlic and shallots are best planted in the fall and require the same good care. (Photo courtesy Meredith Seaver)

Good soil preparation and good plant care will give you the healthy plants you need for a good garlic harvest. (Photo courtesy Meredith Seaver)


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