This plant disease, also known as bacterial gum-mosis or bacterial blast, is found on various fruit and nut trees but is most severe on cherries. This disease is caused by bacteria (Pseudo--monas syringae). Splashing rain spreads the bacteria to dormant buds, twigs, and branches. Infection occurs through wounds in the twigs and branches, and bacterial decay causes cankers to form. During the fall, winter, and early spring, large quantities of bacteria-containing gum ooze from the cankers. Bacter-ial activity decreases in the summer. Slowly developing cankers may encircle a branch, however, and by midsummer, affected branches and limbs start to die back. With the onset of cool, wet, fall weather, bacterial activity in-creases again. This disease is most serious on young trees.
Bacterial canker is difficult to control. Prune out diseased branches. Disinfect pruning. Prune in late winter or early spring rather than early in the dormant season.
This plant disease, caused by either of two closely related fungi (Monilinia laxa or M. fructicola), is very destructive to all of the stone fruits. The fungi spend the winter in twig cankers or in rotted cherries (mummies) in the tree or on the ground. In the spring, spores are blown or splashed from cankers or mummies to healthy flower buds. After penetrating and decaying the flowers, the fungus grows down into the twigs, producing brown, sunken cankers. During moist weather a thick, gummy sap oozes from the lesions, and tufts of gray spores may form on the infected areas. Spores from cankers and infected blossoms or mummies are splashed and blown to the maturing cherries. Young cherries are fairly resistant to infection, but maturing cherries are vulnerable. Brown rot develops most rapidly in mild, moist conditions.
Treat the tree with a fungicide that''s labeled for brown rot, following label directions. Remove and destroy all infected and dried-up fruit. Prune out cankers and blighted twigs. Clean up and destroy all debris around the tree.
Rhagoletis species These worms are the larvae of several closely related flies. The adult flies, about half the size of the common housefly, are black with dark bands on the clear wings. Adults appear in the late spring for a period of about a month. They lay eggs in the cherries through holes they puncture in the skin, beginning when the fruit has turned yellow. After several days, the eggs hatch into maggots that tunnel through the cherry flesh. Mature maggots exit the fruit and drop to the ground, where they burrow into the soil to pupate. They remain in the soil throughout the winter and emerge as adults the following spring. Damaged cherries have an exit hole. They may fall or remain on the tree.
You can''t control the worms in the current year''s fruit. When adults are active, apply an insecticide labeled for this pest, following label directions. Prevent maggots from burrowing into the ground to pupate by spreading black plastic under the tree.
This plant disease, also known as yellow leaf spot, is caused by a fungus (Coccomyces hiemalis). The fungus spends the winter in fallen leaves. About the time the cherry trees are finished blooming, large numbers of spores are splashed and blown from leaves on the ground to the emerging leaves. The infection and premature death of the leaves greatly reduces the amount of food the tree can make and store. This results in weakened trees and reduced, poor-quality fruit yields. Such trees are much more susceptible to cold injury during the following winter. Cherry leaf spot is most severe during mild (60° to 70°F), wet weather.
Treat infected trees with a fungicide labeled for cherry leaf spot, following label directions.
Synanthedon species The larvae of these moths damage stone fruits and some ornamental trees. The blue to black, clear-winged moths (which resemble wasps) lay their eggs in mid- to late summer. The larvae bore into the bark either at or just below the ground level or in the upper trunk and main crotches. Their tunnels interfere with the circulation of water and nutrients, causing twig and branch wilting and dieback. The borers feed throughout the winter and into the spring in their tunnels. A gummy sap may ooze from the borer tunnels. This sap is often mixed with sawdustlike particles, the product of larval feeding. Borers pupate in early to midsummer; their cocoons are located at the base of the tree or just inside their tunnels. The moths emerge several weeks later.
Apply an insecticide that''s labeled for peachtree borers, following label instructions. Avoid wounding trees.
Conotrachelus nenuphar The adult insects are 1/4 inch long, mottled brown-and-gray beetles with long, curved snouts. They hibernate in debris and other protected places during the winter. The beetles emerge in the spring when new growth starts and feed on young leaves, blossoms, and developing fruit. After 5 to 6 weeks, female beetles lay eggs in the young cherries. During this process, they cut distinctive, crescent-shape slits into the fruit. The young grubs that hatch from the eggs feed for several weeks in the fruit. Usually infested cherries drop to the ground. The grubs eventually leave the fruit and bore into the soil, where they pupate. The emerging beetles feed on fruit for a few weeks, then go into hibernation. Or, in the South, they lay eggs, producing a second generation of grubs in the late summer.
Once the fruit is infested, you can''t kill the grubs inside. Pick and destroy the infested fruit. The following spring, spray the plants with an insecticide labeled for plum curculio.