Phil VanBuskirk...
Practical Grower
Harvest will soon be completed, and many orchardists will be putting their equipment away in the barn and attaching a sign on the door "gone fishing." However, these thoughts may be just a little premature. Fall is an excellent time to evaluate our orchards for nutrient problems and reduce our pest populations going into the next season.
Nutrient evaluation
Before an orchard tree can bear, it must grow, and this growth depends upon food and proper conditions of the soil. In order to supply the trees with the necessary nutrients required, either a leaf or soil analysis, and possibly both, should be taken every three to five years, along with annual visual observations on overall tree health.
The recommended timing for a leaf analysis is July 15 to August 15, too late for this year if you haven't already done so; however, a soil analysis can be taken anytime during the year.
If you're not sure how or where to have these tests conducted, call your local extension office for advice or assistance.
Once a soil sample or leaf analysis has been taken and recommendations made, you can begin to formulate a plan of attack to correct any identified problems over the next year. By having your test conducted early, deficiencies such as boron, which may affect fruit set the following spring, can be corrected in the late fall prior to leaf drop.
Insect pests
Just because your fruit has been harvested doesn't mean that the orchard pests feeding on your trees have gone away. A great man once said, "Bugs do not search for the poison, in order that they may accommodate the orchardists by committing suicide." Pests such as spider mites, San Jose scale, and pear psylla continue to feed until the leaves fall off or the first frost occurs.
A postharvest spray, such as lime sulfur plus horticultural spray oil, has been used for years as a fall cleanup spray for these insect pests and others like pear rust mite and pear blister mite. What makes this a great product is that it is one of a handful of spray materials to which insects and disease haven't developed resistance.
Advantages of using lime sulfur and oil in the fall are that it reduces the number of overwintering pear psylla, and aids in control of pear rust mite, pear blister mite, and San Jose scale. A spray of lime sulfur and oil may also aid in control of pear scab if present, and will defoliate trees so that pruning can begin earlier.
Sprays of lime sulfur plus horticultural spray oil should be applied to green leaves just prior to leaf drop and are most effective when large areas are treated at the same time.
Applications should be applied with the following precautions: 1) Do not apply with a pyrethroid, as you may add to resistance problems; 2) Do not apply to weak or moisture-stressed trees; 3) The use of sulfur alone or Sulforix in place of lime sulfur may work but will not cause defoliation so that pruning can be started early.
Cultural practices such as fruit removal (sanitation), trunk banding, and abandoned tree removal will also aid in controlling codling moth the following year. A sample from the cull bins in the packing house should also be taken from each identified block as it is run through the packing house. From this sample, the packing house should note specific problem pests such as codling moth, leafroller, grape mealybug, honeydew marking (aphids, pear psylla, mealybug), San Jose scale, scab, or anything else that can be reliably identified. From this information, you can make changes in your monitoring program or treatment regime to deal with these blocks where specific pest problems were observed.
If apple or pear scab was a problem this last year, leaves infected with the fungus provide an overwintering host and source for infection the following spring. Lime sulfur sprays may aid in the suppression of both apple and pear scab, but where heavy infections have occurred, foliar applications of urea have been shown to be more effective.
The urea applied before leaf drop helps to speed up leaf decay during the winter, thereby reducing primary spores the following spring. The fall application of urea is not a substitute for spring management of scab, and it will not prevent scab infections if conditions are favorable. This spray may also increase the nitrogen available to the next spring's flowers.
Fall cleanup sprays should be applied at a dilute or semidilute (200 gallons per acre or more) concentration to assure good coverage of the leaves, limbs, and trunks. Many insect pests overwinter under the bark and in cracks and crevices of the tree that concentrate sprays may not be able to reach.
Fruit growing is a year-round job and so is the control of our orchard pests. With a little additional work this fall, hopefully, your job will be made a little easier this next season. *
Phil VanBuskirk is the Oregon State University Cooperative Extension educator for Jackson County.
Postharvest orchard activities
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