One of the most frustrating aspects of growing fruit trees in the backyard garden is pest control. Not many of us are willing to share 50 percent to 90 percent of our fruit with pesky insects that insist on devouring our fruit. Because we are not willing to share the harvest with them, we need to implement a control strategy. Recent frosts have severely thinned the fruit. Preserve what's left with a careful spray program.
When controlling a pest consider an integrated pest management program. Spraying in and of itself is not likely to be successful unless you use related cultural controls.Pest management does not mean eradication. Choose and apply products correctly. The most serious pest of apples and pears on a worldwide basis - and in the Intermountain area - is the codling moth. The codling moth lays eggs that hatch into the familiar worm that we see when we bite into an apple. Codling moth control programs start at a different time each spring based on the weather. Careful timing will use less pesticide and the pesticide will be more effective in controlling problems. Timing should be based on temperature and insect development rather than on calendar dates.
The adult codling moth is a night-flying moth and is seldom seen. It is about three-eighths of an inch long, gray in color and has a band of iridescent colors on the tips of its wings. The eggs are laid on or near the small developing fruit. The hatching larvae must crawl across the fruit surface to enter the fruit.
It is easy to control this small worm if you use the right product at the right time. Unfortunately there are several generations of this pest each year and the fruit must be protected until mid-August. Gardeners in the Salt Lake, Weber and Farmington area should spray immediately. In Utah County and cooler areas spraying should be delayed a few days.
The most effective product to control codling moth in the home orchard is Imidan. It should be applied every 14-18 days. Imidan is a wettable powder and does not spray easily with a hose-end sprayer. Wettable powders are less damaging to fruit finish so most commercial orchardists prefer them. To use Imidan, mix the powder with a small amount of water so it forms a smooth, creamy paste before mixing with the water in the jar. This makes plugging of your sprayer less likely. Do the same thing before you add it to a pressurized tank or knapsack sprayer.
Zolone is still available to homeowners and is easier to use because it is a liquid. It is more toxic so you must use protective clothing and the respirator specified on the label.
Diazinon is another choice for many gardeners. Unfortunately, diazinon does not give as good as control and must be applied more frequently, that is, every 7 days. Diazinon is probably not the best choice for codling moth control because frequent applications kill off many of the desirable predatory insects.
Some gardeners are curious about organic pest control for codling moth. Unfortunately, there aren't any practical methods.
In Japan, apples are sometimes covered with bags so the codling moth cannot get into the fruit. This is an effective method, however, most gardeners are unwilling to spend the time and effort necessary to do this.
Codling-moth traps are useful for monitoring, but they do not provide any pest control. Pheromone traps trap only the males. The males do no damage to the fruit because they do not lay the eggs. The so-called bait traps made of molasses and other materials will attract the moths, but some researchers have shown that they actually attract more insects to trees.
Garden sanitation is an important part of controlling pests. Overwintering sites such as fallen apples or trash around the base of trees should be destroyed. If you don't like to spray, consider removing apple and pear trees and replacing them with ornamental trees that do not require extensive pest-control programs.
We will discuss wormy cherries in detail in a future column. It is not yet time to spray for wormy cherries. Wait until the cherries turn from bright green to straw yellow in color. Spraying prior to this time defeats our integrated pest management programs and uses more pesticide without getting any results.
Remember to read and follow all label directions when spraying your trees. Every year I get a number of complaints from gardeners who have fruit with large burned areas or spots and blemishes caused by using too much spray. Too much spray does not improve insect control and may do serious damage to the fruit and tree.
Other garden tasks include planting warm season crops. Right now is the time to take care of problems that could surface later. Large tomato vines covered with green tomatoes that never ripened, were probably the result of too much nitrogen fertilizer. Too much nitrogen promotes green growth at the expense of flowering, fruiting and consequently ripening. Avoid the problem by using high phosphorus fertilizer (the second number of the bag).
If you have had problems getting tomatoes to fruit in the past or have applied large amounts of fresh manure, don't add any nitrogen. If you are looking for a separate phosphorus source, look for treble super phosphate, (0-45-0). As with any fertilizer don't apply excessive amounts as it may damage plants.
-Annual Iris Show of Utah Iris Society: May 26-27, 1990 - Saturday 1-6 p.m., Sunday 10 a.m. to 5 p.m. at the Garden Center in Sugarhouse Park, 1602 E. 2100 South.
-Lawn water this week: 1.1 inches.