Yellowing Leaves on a Young Plum Tree

Hunker may earn compensation through affiliate links in this story.

Some problems that plague plum trees (Prunus spp.) reveal themselves when their naturally green leaves turn yellow. Young plum trees -- those that have not produced fruit yet -- are sometimes more vulnerable to fungal diseases and soil fertility problems than established trees because of transplant shock, which is the disturbance of their roots from being dug at a nursery or removed from a container. Trees must overcome the effects of transplant shock before their roots become -- literally -- grounded, allowing the trees to stand firmly on their own.

The leaves of young plum trees may also turn yellow because of insufficient water and bacterial and viral diseases.

The first three years after planting a plum tree -- typically before it bears fruit -- are the most critical for its healthy establishment.

Tip

The perennial range of most plum trees is across U.S. Department of Agriculture plant hardiness zones 3 through 9.

Cultural and Environmental Problems

Watering

When a tree experiences drought stress -- not enough water for healthy growth -- its leaves scorch and turn yellow through a process called cladoptosis. This is a defense mechanism that allows the tree to conserve water by shutting off the water supply to its leaves. As the water supply dwindles, the leaves turn yellow and fall from the tree.

Heat stress -- usually during hot, dry summers -- causes similar symptoms to drought stress.

Tip

A newly planted plum tree needs 1 to 2 inches of water a week during its first year after being planted. If natural rainfall doesn't supply this, you'll need to apply 3 to 5 gallons of water each week around the tree.

Every year thereafter, the tree needs 1 inch of water each week.

Fertilizing

Unlike the guidelines for transplanting other trees, a plum tree shouldn't be fertilized when you plant it. A jolt of fertilizer at planting time is too harsh for a young, newly planted plum tree and can burn the leaves, causing them to turn yellow and then brown. Clemson Cooperative Extension experts suggest the following fertilization regimen: Wait until the following spring (or late winter) -- when the leaf buds begin to open -- before applying 1 cup of a granular 10-10-10 fertilizer in a 3-foot diameter around each tree. In mid-May and again in mid-July, add 1/2 cup of ammonium nitrate or calcium nitrate in a 2-foot diameter around each tree.

In subsequent years, make two fertilizer applications -- one in March and another in August. In March, apply 1 cup of 10-10-10 around each tree for each year of a tree's age (to a maximum of 12 cups). In August, apply 1 cup of ammonium nitrate or calcium nitrate around each tree for each year of a tree's age (to a maximum of 6 cups).

Tip

Apply fertilizer evenly to the soil from the drip line -- the imaginary line on the ground beneath the outermost spread of the limbs -- toward the trunk, being careful to avoid the 1-foot area around the trunk. Water the fertilizer in well.

Herbicide Injury

Chemicals used to kill plants -- typically weed killers -- can damage nontarget plants through chemical drift or volatilization. Yellowing foliage is the result.

Warning

  • Don't spray herbicides on windy days, because they may drift onto a plum tree.
  • Don't spray herbicides when the temperature is above 85 degrees F, because the spray can volatilize or turn into a gas that travels to, and settles on, a plum tree.

Fungal Diseases

Plum trees are susceptible to three primary fungal diseases:

Verticillium Wilt

A telltale symptom of verticillium wilt is yellowing leaves that retain some green color along the veins. Cut open a branch and look inside. If you see streaking just underneath the bark, the culprit is probably verticillium wilt. The fungal pathogen that causes this disease can lay dormant in the soil as long as 10 years to attack young or established trees. There is no cure for this disease.

Armillaria Root Rot

If a young tree has been planted in an area that has poor drainage, during a time of unusually high rainfall or if you've overwatered it, the roots can become infected with armillaria root rot. Like verticillium wilt, the fungal pathogen is long-lived in the soil, and there is no cure.

Peach Leaf Curl Fungus

Peach leaf curl, caused by the fungal pathogen Taphrina deformans, can cause infected leaves to turn yellow, pucker and curl. If you see these symptoms, it's too late to apply a fungicide. As a preventive treatment, you can apply a fungicide twice a year -- in fall/late winter as the tree enters dormancy and just before the leaf buds open in late winter/early spring.

Tip

Apply a fungicide containing copper hydroxide, typically at the rate of 1/3 to 5 1/3 teaspoons in 1 gallon of water. Spray all branch and trunk surfaces after leaves drop in fall and before leaves open in late winter/early spring.

Bacterial Leaf Spot

The bacterial pathogen Xanthomonas campestris pv. pruni can infect plum trees, causing the leaves to turn yellow. Bactericidal treatments are often ineffective, but preventive copper sprays may be applied just as leaves drop in autumn.

Tip

Apply a fungicide containing copper hydroxide, typically at the rate of 1/3 to 5 1/3 teaspoons in 1 gallon of water. Spray all branch and trunk surfaces after leaves drop in fall.

Warning

Prior to using any pesticides, including herbicides, fungicides and bactericides, carefully read and follow the label directions and familiarize yourself with the general guidelines for safe pesticide use.

Peach Mosaic Virus

Plum trees infected by peach mosaic virus are usually slow to leaf out in spring. When the leaves do emerge, they are small, yellow and crinkled. There is no treatment for plant viruses; remove the infected tree immediately.

references

Victoria Lee Blackstone is a horticulturist and a professional writer who has authored research-based scientific/technical papers, horticultural articles, and magazine and newspaper columns. Her writing expertise covers diverse industries, including horticulture, home maintenance and DIY projects, banking, finance, law and tax. Blackstone has written more than 2,000 published works for newspapers, magazines, online publications and individual clients.

View Work