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While you're sitting back and enjoying a peach margarita or a fresh peach pie--however you choose to utilize this year's bounteous harvest-- start thinking about next year.
This year's peaches seem to have more blemishes on the skins than normal, says Jerry Goodspeed, Utah State University Extension horticulturist. There are three main reasons for this. The most obvious is hail damage many orchards experienced in May and early June. This damage appears as small sunken brown spots that sometimes crack.
Often peaches exude gum out of a small blemish on the skin, he explains. This is normally caused by small insects that feed on the fruit in the spring. The tree's natural defense against a feeding insect is to drown the critter or push it out with excess sap. By spraying the tree in late May or early June, some of this damage can be prevented.
"The most common cause of blemishes is a fungus called coryneum blight," Goodspeed says. "It is often referred to as 'shot-hole' disease because leaves infected by the fungus get small brown spots which eventually become holes as the centers fall out. This makes the leaves look like someone blasted them with a shot gun."
On fruit, the disease appears as small brown bumps on the skin. The infection is only skin deep. The fruit is still edible but may need to be peeled before the cream and sugar is added, he says.
"Coryneum blight damage is aggravated by wet springs," Goodspeed says. "To treat infected trees, apply a registered fungicide such as Daconil in the fall, right after leaf drop."
Cleaning up the leaves and debris from around the tree also helps, he adds. Because wet conditions increase the likelihood of coryneum blight, keep sprinklers from watering the tree canopy. Another application of the fungicide may be needed right after the blossoms drop in the spring. It may take two or three years to clean up this condition, but it can be treated. You can even start pruning and thinning in September.
"Leave about 5 inches between peaches when thinning," Goodspeed explains. "This gives each fruit a chance to grow without being crowded by other fruit. If peaches are not thinned, the fruit will be small. If the tree becomes overloaded, branches may break or the excess weight may even split the tree in half."
Thinning a prize peach tree is difficult for most people, he says. However, a peach tree has only a certain amount of energy it can put into producing fruit. When there are zillions of peaches on the tree, each one is allotted only a small amount of sugar and energy. This creates smaller peaches with less flavor.
Thinning peach trees allows them to put more energy into each fruit making them larger and sweeter, Goodspeed says. The overall volume of fruit is basically the same whether the fruit is thinned or not. The difference is the size and flavor of each peach.
By Dennis Hinkamp - Utah State University Extension
