Healthy Home Orchards (cont)
By: Whitney Cranshaw
This pest often rivals the codling moth as a fruit grower's headache, at least in the midwest and eastern states where this "snout beetle" is well established. Capable of damaging almost all tree fruits, plum curculio can cause several kinds of injuries throughout most of the growing season.
Early in the year, around the time when petals fall, the overwintered beetles cut semicircular scars in fruit as they feed. These puncture wounds scar and deform the fruit. The beetle then lays eggs in some of these wounds. The eggs hatch into the grublike immature forms that tunnel in the developing fruit, causing infested fruit to fall in late spring, well before it has ripened. For the rest of the season, the new crop of adult beetles is present, chewing on and pitting whatever fruit they choose to feed.
Again, a variety of precautionary measures is best. Pick up fallen fruit in late spring or early summer. This will clear up the main source of the new crop beetles, which are developing within the fruit. Prune and train the tree to open up and accept more light: plum curculio hates light and thrives where vegetation is most dense.
Control of adult beetles, as they awaken and move to trees in spring, is also recommended. Usually they begin to show up after the first warm spell in spring. (Three days with an average temperature of 60° F and a bit of rain is a perfect scenario for plum curculio kick-off.) Shake the branches to dislodge the beetles, which tend to drop when disturbed. They can be collected on sheets placed under the tree. Insecticides are frequently used, although plum curculio is difficult to control with many of the more commonly available products. Phosmet (Imidan) is one of the few insecticides that work well against this pest.
Fruit flies (Rhagoletis), such as the apple maggot and the cherry fruit flies, are also common orchard pests. Apple maggot, also called the "railroad worm," tunnels inside apples (less commonly hawthorn, cherries, pears and most other fruit) and creates meandering brown streaks that often cause decay. Similarly, cherry fruit flies tunnel and destroy cherry fruit. Damage by fruit flies is also caused when the adult insect lays eggs in the fruit, causing puckered wounds on the fruit surface.
Yellow panels are very attractive to the flies during the first couple of weeks after they become active. Use yellow sticky cards to detect when the insects are active, and when sprays are most appropriate. These traps also can be used to control these insects. Later, other traps can be used, notably the "Super Apple" a red sticky sphere resembling a somewhat oversized apple. Hung on the tree, this serves as a super attractant to the female flies as they seek out places to lay eggs.
Cleaning out infested fruit is also important when managing fruit flies. Pick over cherries as completely as possible and destroy apples showing the "stings" of apple maggot so that developing insects in fruit are destroyed.
Fruit flies also breed on the fruits of wild plants. Apple maggot prefers hawthorn, and cherry fruit fly prefers wild black cherry. If these pests are problems, consider destroying any of these plants that a nearby.