We should have anticipated a unique year when March was warmer and drier than May. Whenever Mother Nature gets the months confused, our plants have problems.
“Freezing temperatures in late April and early May started our problems with a disappointingly early exit of many of our apples, peaches and apricots,” says Jerry Goodspeed, Utah State University Extension horticulturist. “The wet weather also added to the problem of coryneum blight in stone fruits. This means most stone fruit tough enough to make it through the freezing temperatures are now spotted with little brown freckles.”
Coryneum blight cosmetically affects the fruit, but it is still edible and can be preserved, Goodspeed says. Nothing can be done about it right now, but if the disease goes unchecked in the coming years, it can infect the twigs and severely damage the tree. This fall, pick up and remove all the leaves after they fall, then spray the tree with Daconil to control the overwintering parts of the disease.
“This has also been a great year if you are a black cherry aphid,” he says. “These aphids roll the leaves of the tree, leaving a sticky, messy goo behind.”
Many natural predators help control the black cherry aphid, he explains. Normally, about this time of the year, they begin to eat the nasty pests and the problem dissipates. Spraying the tree with an insecticidal soap will help, but complete coverage of the insect is hard to achieve because they are snuggled comfortably inside the rolled leaves. A registered insecticide can also be used, but it may also kill the natural predators.
Some raspberries are also looking a little tough this year, Goodspeed says. The biggest problems seem to be over-watering and the raspberry cane borer. Over-watering aggravates iron chlorosis, causing the leaves to turn pale yellow with green veins. To improve this condition, reduce the frequency of watering and allow the soil to dry between watering.
“Raspberry cane borer is a hard-headed insect that bores through the middle of the canes near the top,” he says. “Since the insects bore inside the cane, the only way to see them is by splitting the cane open. Their boring disrupts the water flow to the top of the cane, which causes the top of the cane to wilt and the leaves to turn brown.
“Of course, when the plant looks dry, the first thought is to water more. Unfortunately, this promotes iron chlorosis, which weakens the plants, making them more susceptible to the cane borer. What a vicious, ugly cycle.”
If you suspect the cane borer, simply squeeze the top of the cane with your finger. Wear a glove to protect your fingers from the thorns, he cautions.
When the cane borer is present, the cane smashes quite easily, Goodspeed says. Split the cane open with a knife and you can look at the little critter. The only treatment for the cane borer is to remove the top portion of the cane where the borer has been munching. Throw the cane away. Do not compost it or use it for mulch in the yard.
Another problem this year has been leaf spot and other diseases in oak, aspen and maple trees, he adds. These diseases are common when we have cool, wet springs. Right now there is not a lot that can be done, but normally the tree won't die from this condition. They will be weakened, however, which leaves them more susceptible for other pests. The best thing to do is clean up all the leaves in the fall and remove them from the yard.
For more information, contact your local USU County Extension office.
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Issued in furtherance of Cooperative Extension work, Acts of May 9 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert L. Gilliland, Vice-President and Director, Cooperative Extension Service, Utah State University, Logan, Utah. (EP/08-99/DF)