Is it Time to Spray Your Fruit Trees?
It’s again the time of year when trees start blossoming and gardeners start wondering when they should spray for pests.
“Thankfully, there are very few pests that will completely wipe out a tree or plant,” said Jerry Goodspeed, Utah State University Extension horticulturist. “There are only a couple of pests that most home fruit growers need to actively control, and most can be controlled with less spraying than was customary in the past.”
A great deal of research has been done on the life cycle and vulnerable times for most pests, he said. As a result, less spraying is necessary because specific periods can be targeted when pests are active and more susceptible. Better, safer products are now available on the market, and many of them are classified as botanical, which means they are not synthetic-based.
“Last spring was very hard on many stone fruit trees,” Goodspeed said. “The cool, wet weather had coryneum blight thinking it was back on the West Coast enjoying a foggy beach. This fungal disease thrives under such conditions, so it could cause problems again this year.”
Coryneum blight can destroy leaves, limbs, branches and much of the fruit, he said. Fortunately, the impact of this disease can be reduced with a spray applied right after the flowers drop to the ground. Using one of several registered fungicides available at local nurseries or garden centers can be an effective way to handle this disease.
“If you prefer a more environmentally safe, organic control, apply copper sulfate, fixed copper or a Bordeaux mixture,” Goodspeed said. “These may need to be applied more than once because of their shorter persistence on the tree, but that also makes them a little friendlier.”
Coryneum blight does not affect apples or pears, but powdery mildew does. This disease enjoys wet spring weather and is most prevalent on strains of Jonathon and many new apple varieties, he said. It can greatly diminish the energy in a tree, which reduces the amount of fruit harvested in the fall.
Control measures for this disease must also be timed correctly, he said. Apply a registered fungicide or use a sulfur product while the tree is putting out new growth. Consult the label for timing and frequency. Many trees are resistant to powdery mildew and do not need to be treated. If buying a new apple tree, select one that is labeled as resistant to powdery mildew.
“One insect pest that attacks apples and pears and makes them mostly inedible is the codling moth,” said Goodspeed. “This insect is responsible for those unsightly worms that relish the fruit as much as we do. They are not active in the early spring and do not need to be treated for a few more weeks. Spraying an insecticide on an apple tree right now only kills bees and aggravates the neighbors.”
Spraying to control the codling moth normally begins about three weeks after full bloom, he said. This insect’s activity is totally based upon the weather, so its emergence is based on the temperature, not the calendar.
“With this in mind, Utah State University monitors this hungry pest and can determine exactly when it needs to be sprayed,” Goodspeed concluded. “Contact your local county agent for further information.”
By: Jerry L. Goodspeed - May 12, 2006