Dormant pruning and spraying the orchard
February 20, 2014
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URBANA, Ill. - Home orchardists should be planning their winter pruning while their apple trees remain dormant before the sap starts to flow for 2014, said a University of Illinois Extension horticulture educator. 

“Depending on the weather pattern, pruning can begin in perhaps mid- to late February,” said Richard Hentschel. “The later the pruning is done, the less damage really cold weather will do to the tissue that is now exposed where the pruning cuts were made. Dormant pruning is a lot easier because there is no foliage present to obscure the branches in the canopy.”

The easiest branches to remove will be the water sprouts. Water sprouts originate from the horizontally trained scaffold branches and grow vertically up through the canopy. Water sprouts do not contribute to fruit production and can limit the level of sunlight that is able to penetrate down through the canopy, which allows fruit production within the canopy.

Once the water sprouts are gone, additional pruning is more easily done.

“The goal of pruning is to balance vegetative growth with reproductive growth.  Depending on the variety and vigor of the apple tree, a portion of last year’s annual vegetative growth can be removed. This will help keep the apple tree smaller and at a more manageable size for a home orchard where growing space is often limited,” Hentschel said.

This time frame also allows the home orchardist the opportunity to review current scaffolds and determine the location of any needed branch spreaders for the season on older scaffold branches. If there are to be new scaffolds created, very small spreaders are used once the new young branch is 3 to 5 inches in length. Hentschel explained that traditionally branch spreaders have been made from a hard wire with a diagonal cut at each end or from linear pieces of wood with a nail in each end, with the nail head cut off similarly as the wire.

In both cases, a variety of lengths will be used to accommodate the varied sizes of branches in the canopy. In a back-yard setting where there are limited trees, the home orchardist can also use soft rope or twine to pull down scaffold branches into place, and then use a stake pounded into the soil beneath the apple tree. “Tie the rope or twine so it can be adjusted as needed during the growing season,” Hentschel recommended.

Dormant sprays are used to manage insect eggs laid during the previous summer as well as adult insects that are overwintering in the rough bark on the older trunk and branches. Dormant oil sprays work by smothering the eggs and adults so thorough coverage is critical for good control. 

“As a rule, dormant oils are applied in very late winter to early spring before any growth resumes,” Hentschel said. “Dormant oils are sprayed while the air temperatures will remain above freezing for at least 24 hours. Dormant oils will be mixed with water, and if allowed to freeze on the tree, will not soak in and be effective.”

He added that there are at least three different kinds of oil available right now. “Read the instructions on the label for specific application requirements because they will vary in their degree of refinement. Dormant oils are considered organic and can be used with other organic practices,” he said.