All deciduous fruit trees are susceptible to insects and diseases that affect the quality of the fruit and the health of the trees. The winter dormant period — after leaves have fallen off but before buds open in the spring — is the best time to tackle those pests.
Begin by pruning the trees. The absence of leaves provides a clear view of the framework of the tree and is a good opportunity to remove or cut back any branches. Take out dead, diseased, crossed or broken branches as well as water spouts and root suckers. Dispose of all diseased wood away from the orchard.
Rake up leaves before the first rain. Remove and destroy any fruit or dry, shriveled mummies that are still on the trees or the ground.
Apply dormant sprays, such as copper, lime sulfur, or a synthetic fungicide. These limit the spread and infection of certain fungal diseases such as leaf curl, shot hole, powdery mildew and scab.
The exact timing during the dormant period varies depending on the disease being controlled. But once flower buds begin opening, you risk damaging fruit and killing pollinating bees.
Spraying after pruning allows maximum coverage as there are no leaves to block the spray. Avoid making applications on water-stressed trees as that may harm them.
A good time to spray is right after a period of rain or foggy weather. Don’t spray in fog, rain, or during or prior to freezing weather (under 32 degrees F).
Dormant treatments may not always be required. For some pests and diseases, one dormant application may be adequate with good spray coverage. For other problems, up to three applications may be needed for good control.
When using any chemicals, always remember to read and carefully follow all precautions and safety recommendations on the container label.
For more information, go to http://anrcatalog.ucdavis.edu/pdf/8368.pdf.
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