The spell of warm weather has awakened the dormant garden giant within many! Most soils are too wet to plow or rototill and plant. There are a few crocus peeking through but no flowers to tend, so our attention is directed to the woody plants such as fruit trees as the object of our pent-up desire to work at something.
Speaking of dormant, garden stores are promoting a spray for "dormant disease control" right now. By looking at the label closely, as all good gardeners do, you'll notice the main active ingredient is calcium polysulfides, lime sulfur or a similar name. If you've used it in the past, you'll notice a rotten egg smell to the area.Fruit and ornamental trees along the Wasatch front are damaged little by the diseases this dormant spray controls such as peach leaf curl, apple scab, and powdery mildew (except for the Jonathan apples). Our normally dry weather during spring and fall is not suitable for these diseases to be severe.
Coryneum blight has become much more serious the past few years. This blight of peaches and apricots is not one that can be controlled by a dormant spray of lime sulfur. The organism invades the plant tissue in the fall. The USU recommendation has been to apply preventive sprays of copper during October. Additional sprays of daconil at petal fall will help keep fruit clean and will help keep apricots from being freckled and peach fruit from exuding spots of gummy sap.
To get back to the spray program for our Intermountain area, the main concern here is to get a jump on insect control. The pests that overwinter on bark, twigs and buds emerge and rapidly reach leaf and fruit damaging numbers. As the season warms up, these insects become more active and are less protected than in the completely dormant stage. Replace that old "dormant spray" term in your memory bank with "delayed dormant."
Control for these can be obtained by covering thoroughly those twigs and buds with a specially refined petroleum oil. Such oils are marked as Volck, supreme, superior or dormant oils. Their action is to smother scales, aphids, mites and other soft-bodied insects with a coating which disrupts their respiration.
Combining an insecticide, such as diazinon or thiodan (especially for pear psylla) will greatly enhance the spray's effectiveness. Another factor in the spray's effectiveness is timing. The weather should be warm enough to promote insect activity, which will render them more susceptible to the chemicals. The trees should not have produced sufficient growth of tender foliage that the spray oil combination will produce a burn.
Apples and ornamental trees that produce leaves before the blossoms should be treated when the leaves are emerging from the buds about 1/4 inch. Pears and peaches, where blossoms are produced before many leaves come out, should be sprayed as the blossom bud swells, but before petals are evident.
Flowering fruit and ornamental trees are never sprayed during blossoming time. An exception is if fireblight has been a problem on pear trees. A spray to control this bacterial disease needs to go on open blossoms but will cause no problem for pollinating bees nor to the blossom itself.
Although insect control is the main purpose of this spray program, some major pests are not affected. For example, tree borers, such as the peach, aspen, ash and locust borers, are in the tree and protected. Pupae of the cherry fruit fly are deep in the soil. The codling moth pupae are virtually immune to chemicals at this time. Proper spraying time for these pests will be given in this column as the season advances and the insects emerge from their resting places to attack the various trees. With some of these pests the adult is the target while others must be sprayed as the small larvae develop.
As with most sprays, thorough tree coverage is vital. A small dwarf apple tree may require only 2-4 quarts of spray, while a large peach, apricot or cherry tree may require 2-3 gallons for proper coverage.
Pressurized hand sprayers and trombone sprayers ensure a proper ratio of spray to water. The dosage that is delivered by hose-end sprayers, according to some tests, may not be correct and consistent.
Before spraying with one of these convenient sprayers that require no pumping, test its output. Fill the sprayer bottle to a level of two to three gallons. Plain water can be used in the place of the pesticide. Turn the water faucet to full pressure and spray into a bucket or other large container. When the last of the water is gone from the bottle, turn off the water and measure how much spray has gone into the bucket. It should be very close to the two to three gallons that the sprayer was measured to deliver. If the volume is much less, that means the spray concentrate is increased and may damage the plant. If, on the other hand, you have four to five gallons, this means the dilution is too great and the spray application probably ineffective.
Hacking of the trees that homeowners call pruning can begin anytime. I'd suggest pruning before you apply the delayed dormant spray. Pruning techniques are difficult to describe in writing, at a meeting or over the phone. Our illustrated bulletin does a good job and can be picked up at our office for 50 cents (address below).
We'll have it at our pruning demonstrations along with fact sheets on the most frequently asked questions on "Peach Tree Borers," "Cherry Fruit Fly," and "Coryneum Blight."
The "Home Orchard Pest Control" fact sheet summarizes the minimum program for growing clean fruit in your yard.
To order fact sheets, send 10 cents for each one plus a self-addressed, stamped envelope to USU Extension, 2001 S. State St., Room S-1200, Salt Lake City, UT 84190-3350. The fact sheets listed will fit in one envelope.
March 15, 7 p.m., Ornamental tree and shrub care with emphasis on pruning. Extension Training Room, S-1010, South Building, County Government Center (CGC) 2001 S. State.
- March 18, 11 or 1. Pruning demonstration. 3705 S. 72nd West. Peaches, apples, pears and grapes.
- March 21, 7 p.m. Vegetable production. Granger Bishop's Storehouse, 3648 S. 72nd West.
- March 22, 2 or 7 p.m. Same subject, CGC, address above.
- March 25, 11 or 1. Pruning Demonstration, 9150 S. 2680 East, Sandy. Assorted fruit trees, grapes and raspberries.