|
What Is It?
Bacterial leaf spot is a plant disease which occurs in both peach and nectarine trees. The bacterium xanthomonas pruni is responsible for this plant disease which in severe cases may cause a peach or nectarine tree to lose all of its leaves. Bacterial leaf spot also causes discolored, mottled and spotted fruit and can also be the catalyst for peach and nectarine trees to have a small crop or under grown fruits. Xanthamonas pruni is one of the most devastating and destructive diseases of the stone fruits in the region east of the Rocky Muontains in the United States. Bacterial leaf spot disease is also a prime attacker of both plum and apricot trees.
What Does It Look Like?
Damage from bacterial leaf spot in peach and nectarine trees begins on the leaves. The peach and nectarine leaves develop brown spots which are angular rather than circular. These spots can sometimes be black, but are most often a light to medium brown in color. The centers of the spots which appear on the fruit tree leaves may fall out, having disintegrated. However, often these spot simply cause the entire peach r nectarine leaf to turn yellowish, and then droop eventually dropping off and causing defoliation of the fruit tree. The peach and nectarine fruits, themselves, may also suffer from a similar angular spotting pattern of disease and infection. Once the stone fruits become infected, they will show brown and black spots which eventually become cracked and pitted in appearance. Once the disease of xanthamonas pruni becomes severe the spots will sink in as the fruits decays. If your fruit trees are infected with bacterial leaf spot, you may also note the appearance of lesions on the twigs of the tree. Both peach and nectarine trees can develop these lesions which will become oozy and sunken on their twigs. At the worst stage of infection, the entire peach or nectarine tree will defoliate leaving only infected branches and fruits unless the fruit has already dropped.
How Does It Manifest?
Bacterial leaf spot over winters in the lesions which develop on the trees. When spring thaws begin, the bacterium begins seeping from the sunken lesions and spores are emitted. Rainfall, splashing water and any form of watering can spread the bacterial ooze and infect nearby susceptible fruit trees. Xanthamonas pruni is very fond of moist, wet regions and when heavy rainfall occurs the spread can be quick and deadly to peach and nectarine trees. If the disease becomes so severe that the peach and nectarine trees defoliate before early summer, it is likely that the entire peach or nectarine crop will have growth problems, as well as produce crops that are both poor in quality and small.
What Can I Do About It?
Bacterial leaf spot is, unfortunately, a tenacious disease in peach and nectarine trees and there is no adequate chemical control for this disease. However, in early spring when buds first open you can try a preventative method to suppress bacterial leaf spot by spraying with basic copper sulfate. Unfortunately, this only suppresses, and does not destroy the xanthamonas pruni infection. Another method of temporary control is to prune out regions with infected lesions or to cut entire branches. This may stave off further infection of the tree, but it is likely once it rains, or water splashes any region where the bacterium still exists that it will continue to infect the tree. There are peach resistant varieties you can purchase, including the Bell of Georgia, Early-Free Red, and Hiley. The most susceptible forms of peach trees are the Blake, Elberta and Rio Oso Gem.
|
| |
