By: Mary H. Dyer, Credentialed Garden Writer
Plum mosaic virus was discovered in Texas in the early1930s. Since that time, the disease has spread throughout orchards in thesouthern United States and certain areas of Mexico. This serious diseaseaffects both plumsand peaches,as well as nectarines,almondsand apricots.Mosaic virus of plum trees is spread from tree to tree by tiny peach bud mites(Eriophyes insidiosus). The virus canalso be spread by grafting.
Unfortunately, there are no cures for mosaic virus of plums,but there are ways to prevent the disease from affecting your fruit trees.Thanks to strict quarantine programs, mosaic virus of plums is now relativelyunusual. Let’s learn the signs and symptoms of plum mosaic virus and how toprevent the disease from infecting your trees.
Symptoms of Mosaic Virus on Plums
Plum mosaic virus shows up on the leaves, which are mottledwith green, white or yellow blotches. The leaves, which are delayed, may alsobe crinkled or curled. Fruit of trees affected with plum mosaic virus are bumpyand deformed. They are unsalable and generally not good for eating.
There is no cure for mosaic virus of plums and infectedtrees should be removed and destroyed. The tree may live on for a few seasons,but the fruit is inedible. There are, however, ways the disease can beprevented.
How to Prevent Mosaic Virus of Plums
When you plant new plum trees, plant only virus-resistantcultivars.
Treat new trees with miticide.Follow the manufacturer’s instructions carefully, especially in terms of timingof spray and how much to use. Be sure the product is registered for use onfruit trees.
Often, mites can be controlled with horticultural oil orinsecticidal soap spray at bud swell – just before blossoms begin to emerge. Toprotect bees and other pollinators, never spray miticide when the trees are inflower.
Water trees regularly. Mites are attracted to dry, dustyconditions.
This article was last updated on
Read more about Plum Trees
Apple mosaic virus
Apple mosaic virus (ApMV) is a plant pathogenic virus of the family Bromoviridae. It is named after its symptoms that were first present on apples.  ApMV is a positive sense RNA based virus.  The disease itself has several synonyms including Mild Apple Mosaic Virus, Hop Virus, Rose Mosaic Virus, and European Plum Line Patten Virus.  It causes a severe yield reduction and decreased life-expectancy of fruit trees.
Birch line pattern virus
Birch ringspot virus
Dutch plum line pattern virus
European plum line pattern virus
Hop A virus
Horse chestnut yellow mosaic virus
Rose mosaic virus
The European plum “President” (Prunus x domestica) is cited by many botanists as a very resistant plum variety. Growing best in U.S. Department of Agriculture Plant Hardiness Zones 5a through 10 b, “President” and other European plums are suited to areas with late frosts and cool, rainy weather in the spring. European plums bloom and produce fruit later in the season than Japanese varieties.
According to Dr. Sharon Douglas at the Department of Plant Pathology and Ecology at the Connecticut Agricultural Experiment Station, Japanese plum varieties (Prunus salicina) have more resistance to black knot than other varieties. Among the varieties named by Dr. Douglas and others are “Santa Rosa,” which grows well in USDA Plant Hardiness Zones 5b through 6b and 7b through 10b, and “Shiro,” which grows well in Zones 5b through 10a.
Pruning a plum tree
For a plum tree, pruning fulfills two functions: caring for the tree itself, and enhancing fruit harvest.
General pruning principles
It’s recommended to prune only what is strictly necessary because plum trees are delicate and wounds make it vulnerable to diseases.
After each cut, apply pruning paste like pine tar to protect the wood from fungus and other diseases.
Nonetheless, you may perform directional pruning in the first year to shape the structure of the tree.
- Directional pruning is performed in winter but not during freezing weather.
- The goal here is to thin out the shoots from the trunk to end up with 3 or 4 main branches facing outwards.
- Like all pit trees, especially the cherry tree, pruning is performed at the end of the summer or in the beginning of fall.
After having harvested the plums
Maintenance pruning is performed in winter but not during freezing weather.
- Once you have harvested the plums, remove dead wood and fragile branches.
- Remove fruits that haven’t fallen from the tree – they are often diseased – and destroy them.
- Also, remove suckers, which are those shoots that emerge at the base of the tree. These suckers draw sap from the tree and will not produce any fruits.
After pruning, using pruning paste helps avoid infection due to fungus and diseases.
Controlling abutilon mosaic disease on flowering maples is unnecessary because it does not harm the plant. However, for gardeners who wish to rid their trees of mottled foliage, management is available. If possible, gardeners may place trees in subdued lighting as a means of diminishing the color contrast on foliage. In addition, some reports indicate that where symptomatic leaves are persistently removed, completely green, asymptomatic leaves may be produced, according to the University of Hawaii at Manoa Cooperative Extension Service.
Sooty mold disappears on its own when the underlying pest infestation is under control. Manage aphids on maple trees by releasing natural enemies onto the tree as a chemical-free first step toward control. Purchase enemies such as parasitic wasps from garden supply retailers. For a persistent problem, saturate trees with a botanical insecticide such as neem oil to kill aphids.
Tarah Damask's writing career began in 2003 and includes experience as a fashion writer/editor for Neiman Marcus, short fiction publications in "North Texas Review," a self-published novel, band biographies, charter school curriculum and articles for various websites. Damask holds a Master of Arts in English and creative writing from the University of North Texas.