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Fruit trees, properly cared for, can furnish a crop with nourishing, tasty, health-enhancing goodness. Unfortunate-ly, other animals find them delectable, and so the battle lines are drawn.

It's the time of year that gardeners, remembering the outcome of that battle in 1988, are inquiring about how to repeat their successes or prevent their failures.Let's consider one of the most universal crop pests first. The codling moth is a problem worldwide where apples are grown commercially. Some Oregon coastal residents don't have the codling moth because the cool climate doesn't allow the completion of the pest's life cycle. But their fruit is of poor color and quality because of these same low temperatures and cloudy days.

Codling moths appear at a different time each spring, depending on the heat accumulation after winter passes. The warm days of 1989 are bringing the adult moths into activity about two weeks earlier than usual.

The moth appears about the time the apples are in bloom. It emerges from a cocoon that has spent the winter under bark or debris around the base of the tree. If the weather is cool, development to the egg-laying stage is slowed.

Tony Hatch, Utah State University tree fruit specialist, has a computer program that accurately predicts when those eggs will be laid and the emerging larvae can be controlled. His research has saved money and environmental contamination. Sprays are recommended on the actual development of the pest rather than an automatic "two weeks after petal fall" standard timing used in the past.

Control measures are not directed at the night-flying moth that is seldom seen. Eggs are laid on or near small, developing fruit. Hatching larvae must crawl across surfaces to enter the fruit, usually at the calyx end, opposite the stem. Control of this very small worm is relatively easy if your spray material provides thorough coverage of that area. There are several generations per year and treatment must continue until mid-August. IT'S TIME TO PREVENT WORMY APPLES NOW!

Two chemicals are recommended - Imidan and Zolone. They are very effective against the worm and need to be applied every 2 to 21/2 weeks.

Imidan is a settable powder and will not spray as easily with a hose-end sprayer. If you mix the powder in a small amount of water so it is smooth, creamy and without lumps before you put it in the jar, plugging is less likely. Do the same before you add it to a knapsack sprayer tank, also.

Zolone is easier to use because it is a liquid. Use caution when you mix and spray it because it is more toxic than Imidan.

The other fruit-invading insect is well-remembered because hardly anyone wants to share their luscious, sweet, dark Bing cherry with a maggot. The Western cherry fruit fly is a more recent invader of the Utah area but is well known in cherry orchards throughout the country. Any cherry tree owners in northern Utah should plan to spray this year or just eat cherries without looking at the flesh around the pit.

DO NOT SPRAY YET! This information is given so you can prepare for the battle of the flies. Call 468-2857 (GOT-BUGS) evenings and weekends to get the proper time.

After spending the winter in the soil as a pupae, the adult fly emerges and must mature for a few days before laying eggs. It is about the size of a house fly and is a fairly strong flyer. Control measures must be directed at the adult fly. The female deposits the eggs under the skin of the cherry, where they are immune to sprays.

Many people report wormy cherries even when they have sprayed. Factors that could be involved include: 1) inadequate coverage of a large cherry tree; 2) rains or sprinkler irrigation that remove spray residue; 3) an abundance of flies from neighbors' unsprayed trees, or 4) improper timing.

Diazinon or methoxychlor are recommended for Western cherry fruit fly control. Methoxychlor is an excellent product, but it is limited in its formulation. Fertilome and Black Leaf include it in their fruit tree spray. It is also the active ingredient in Marlate Methoxychlor Insecticide available at farm supply stores. Use diazinon or methoxychlor on a weekly basis and cover other foliage where the flies may rest.

The flies are present until harvest time, so tart or sour cherries will require more sprays. Methoxychlor requires a seven-day interval between spraying and harvest. During the 10 days that must elapse between spraying of diazinon and harvest, an egg could be laid and develop into a worm. You may want to use a last spray of malathion, which has a three-day waiting period.

It's with hesitation that I suggest FMC Dimethoate 267. Not that it isn't a good product. Complaints of control failure are fewer with this product than any other program. It's available in farm supply stores and the smallest size is a gallon. Since the recommended rate is one-half teaspoon per gallon of water, you'll have it for a long time!

You spray only once and must wait 21 days before harvest.

Whenever you spray, whether it is an insecticide, fungicide or weed killer, consider using a spreader-sticker because the leaf or insect is made "wetter." After the residue dries, removal by rain is less likely so the product lasts longer.

Full-service nurseries sell spreader-sticker products. The amount to add to a gallon of spray is small, but be sure to follow label directions.

Some of our printed material may be of assistance: Home Orchard Pest Control, Wormy Cherries, Peach Teach Borer (by July 1). Stop by our office or send 10 cents for each one wanted plus a self-addressed, stamped envelope to USU Extension, 2001 S. State, Room S-1200, Salt Lake City, UT 84190-3350.

-PLANT SALE AND GREEN SPREE: The State Arboretum's annual plant sale will be May 20, 9 a.m.-3 p.m., on the University of Utah campus, southeast of the Huntsman Center. Herbs, vegetables, unusual plants, natives, house plants and more will be available. Supplies will be restocked at noon. Bring garden questions and visit the problem-solving booth.

-UTAH IRIS SOCIETY SHOW: May 20, noon-7 p.m., and May 21, 1-4 p.m., free, Layton Hills Mall.

-LAWN WATER: Rains from the past week just about meet lawn needs. Check soil for water content before watering.