Originally Published In The Deseret News -- Wednesday, August 6, 1997
Destroy Walnut Husk Flies Before They Lay Their Eggs. Worms Also Pose Problem.
Larry Sagers is a horticulturist with the Utah State University Extension Service. By Larry A. Sagers
One pest that seems to cause ever increasing problems each year is the Walnut husk fly. These creatures have the most annoying habits and the most annoying relatives. Their relatives include the Western cherry fruit fly, the apple maggot, the current fruitworm and the publicity hungry Mediterranean fruit fly. All these are picture wing flies, meaning they have wings with both clear and dark areas. These patterns on the wings are very distinctive for each kind of fly and are the easiest way to identify the pest.
So you might be thinking that since you have no walnut trees you have no problems, but think again. These pesky critters just love to invade juicy ripe peaches and burrow under the flesh. The tiny maggots invade the flesh and cause brown areas to develop. These soft, brown spots make the fruits more susceptible to decay. Since no pest should ever come between a hungry gardener and fresh peaches, read on to find the best way to handle this problem and others that are affecting the Queen of Fruits.
Walnut husk fly is less of a problem on walnuts than on peaches. They attack the outer husk but do not destroy the nut. Commercially they make the husk stick to the shell and make it hard to remove. If it is removed, it leaves a dark stain on the shell that makes it unacceptable. Homeowner harvests are most likely a problem because the nuts are messy to crack.
Both walnuts and peaches require the same control program. The difficulty is controlling the adult flies. These invade trees and lay their eggs underneath the skin of the fruits so the pests must be destroyed before they lay their eggs. The adults are hard to control because they move quickly from tree to tree and are difficult to spray. The recommended spray is malathion, sprayed right now with repeated applications each week.
Two worms can invade ripening peach fruits. The peach twig borer and the oriental fruit moth are both hard, brown larvae that burrow into the stem end of the peachfruit. Finding these inside a peach is not pleasant, and the peach is ruined commercially. These worms tunnel around the stone and leave their fecal droppings. There are no controls once the larvae are inside the fruit. Preventive sprays are needed in June to prevent the pests from causing problems.
Another very unappetizing discovery is finding earwigs in the peaches. These are usually a problem if pests damage the fruit and make holes in the skins. They also enter fruits with split pits that are open to the outside. Prevent the insect damage by the above-mentioned controls. Split pits are caused by stressful conditions during pit hardening. Once the stress occurs the fruit will not be normal, but the splits are of no concern until the pests get inside.
Keeping earwigs out of the peaches is a prime concern. They do not fly so the first line of defense is to get them while they are on the ground. Try placing some flat boards near the base of the trees and let the earwigs collect under them each morning. Turn the boards over and kill the earwigs before they can invade your fruit. Next, wrap bands of corrugated cardboard around the trunks and let the earwigs collect under them. Finally, use some Tanglefoot in a band around the trunk. Tan-gle-foot is similar to the coating on fly paper and will catch any strays that try to climb up to bother the fruit. Don't bother trying to spray the pest in the top of the trees, as any sprays are rather ineffective.
Unfortunately, the wet spring weather left behind more than just the rain. Early outbreaks of coryneum blight are causing many people to see spots. The tiny spots turn purple and start exuding gum. The gumming is a symptom of the infection and spoils the purpose of the fruit. There are often small purple spots that drop out of the leaves and give the disease the common name of shot hole blight. Once the infection has occurred there is nothing you can do to solve the problem. Reduce future problems by spraying the trees with fixed copper or Daconil when the leaves drop off in the fall.
If you are fortunate enough to have a peach crop there are several problems to watch out for. One common mistake is failure to thin the fruit. You needn't bother now because any thinning now will not make the remaining fruit any larger. Overbearing trees are likely to break down and destroy branches or even the main trunks. If that happens, let the branches remain attached to the tree until the fruit ripens. After harvest, the broken branches should be promptly removed. Branches that need props to avoid breaking should be noted so they can be correctly pruned and thinned next year.
Peaches do not sweeten after they are removed from the tree and are best left attached until they are fully ripened. The fruit is highly perishable at this stage but it is never possible to get the highest quality fruit without letting it ripen on the plant. Peach flesh should soften and be free from green colors or tints. The soft texture and the sweet taste are the best gauges of ripeness. The fruit drops quickly when mature so check the fruit every day. Peaches should be color picked, which means that mature fruits are best removed when they reach their peak. Fruit on the south side of the tree ripen first, and those that are more shaded will ripen more slowly.
One of the more serious pests is birds. The ripe fruit is so tasty that many different kinds of birds feed on them. There is no easy solution to bird problems. Scarecrows, rubber snakes, plastic owls and many other remedies are touted but they are not always reliable. Nets are the most effective method but they are hard to put on the trees and are susceptible to tearing and other damage.
The Queen of Fruits is one of the tastiest treats you can grow in your orchard. Control the problems and reap the rewards. If you don't have your own trees call (801) 734-2039, code 330 for updated harvest information along Utah Fruit Way. Tree-ripened peaches are only in season for a short time so don't miss out on your share of these tasty delectable treats.
© 1998 Deseret News Publishing Co.