Controlling Fruit Tree Pests

The biggest frustration for backyard orchardists is the many pests that destroy their fruit. Each year we anticipate a wonderful harvest. Pruning and training, fertilization, spring frosts, summer heat and all the other problems are frustrating enough to most people. When you add pests to these, many question whether they want to try to grow fruit.

Wormy apples and cherries, blight on our peaches and apricots and even the death of our favorite trees from borers and root rot are just some of the hazards. Most pests are unseen until they have done major damage and the crop is nearly destroyed.

Fruit trees are among the most difficult crops in the garden when controlling pests. Many "integrated pest management" techniques that work well on other plants do not work on fruit.

Crop rotation, altering planting dates, substituting resistant varieties and many others are ineffective. Trees are perennial crops and remain in the same place and grow during the same seasons each year. The pests continue to grow and multiply because we cannot effectively break their life cycles.

Although all this may seem discouraging, most pests are still controllable. The key is timely controls, applied at appropriate times, to manage the pests so damage is minimal.

Start by distinguishing the kinds of and severity of damage.

Problems fall into three categories:

Pests that will kill the trees

Pests that will destroy the fruit

Pests that cause cosmetic damage.

Knowing what they attack and which are the most serious helps in the ongoing battle against the pests.

In most cases, pesticides are needed for effective control. Usually there are alternative organic controls are available, although they may not be the easiest or the most effective choices. Carefully monitor the pests and apply timely controls as needed.

The time for backyard orchardists to begin the annual ritual of fighting insects for their fruit is near. Unfortunately, these pests insist on going after the best and tastiest treats from the garden.

Some unwritten gardening law requires pests to attack anything that I'm trying to grow in my garden. They seem to ignore any weeds and leftover fruit or vegetables and consume the juicy ripe peaches, mouth-watering cherries and crispy apples.

I strongly recommend a dormant oil spray on susceptible fruit and ornamental plants. Oils are among the oldest pesticides known to man. The popularity of these products is increasing because they are relatively nontoxic to pets and people and are highly effective products.

Insects breathe through their hard exoskeletons. Oils are effective in controlling most insects, because they coat the pests and prevent them from breathing. They are strictly contact sprays.

They do not kill insects that crawl on branches sprayed with oil, nor is there any fumigating action from the oil. Apply horticultural oils when insects are most likely to be affected.

Traditionally, these were "dormant sprays" applied midwinter when the plants are totally dormant. More highly refined oils are now available so you can apply them later in the season without damaging the plants.

The critical application in upcoming weeks is the "delayed dormant spray." Delay application of this spray until the bud scales separate and expose the pests to spray contact. Warm weather encourages the pests to move from under the scales, which brings them into spray contact. Primary target organisms are aphids, scale and spider mites.

Aphids cause extensive curling of the leaves in the spring. Properly timed and directed, dormant oil sprays destroy the overwintering aphids and their eggs before they damage newly emerging leaves. This treatment is the only effective way to prevent leaf curl on fruit trees as well as flowering plums, snowballs and other highly susceptible plants.

Scale is the second target. This unusual insect attaches itself to the plant and proceeds to secrete a waxy armored coating over its body. This armored coating protects it from most chemical pesticides except systemics. Oil coats the insect covering, preventing it from breathing.

Spider mites are not insects but still are serious fruit pests. Oil destroys the overwintering adults and eggs. These tiny creatures hide inside the buds, so wait for them to start to open before spraying.

Individual plants require a single spray, but the spray must be applied at the proper stage of plant development. Stone fruits are sprayed when flower color begins to appear on the end of the bud.

Apples are sprayed when the green tips are clearly visible on the leaf buds. Delay spraying pears until the blossom cluster starts to separate and the individual buds are visible. The reason for waiting so long is that the pear russet mite is slower to develop, and most emerge from under the bud scales and other hiding places.

All insecticidal sprays must be completed before any blossoms open. Once the blossoms open, bees start visiting the trees. Although oils are not particularly harmful to bees, the other products mixed with the oil sprays are often fatal.

Virtually every manufacturer packages an oil spray. The brand names include Volck, Superior, Supreme and Scalacide. Mix the oil with the water according to the label directions. Organic gardeners use only the oil, while other gardeners add another insecticide to the mix. Read and follow all label directions to protect yourself and desirable organisms.

Oil sprays are extremely useful but do nothing to protect the fruit from some serious pests. Cherry fruit fly, codling moth, peach tree borer and several others all require extensive and precise controls later in the season. Keep reading for the latest information on growing quality fruit and everything else in your garden.

For the most up to date pest control information, go to Utah State University Extension's website at http://utahpests.usu.edu/.