Elm yellows

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Elm yellows is a plant disease that affects elm trees. It is caused by a type of phytoplasma, a specialized bacterium that lacks a cell wall. The disease is also known as elm phloem necrosis due to the damage it causes to the phloem tissue of the tree.

Symptoms

The symptoms of elm yellows can vary depending on the species of elm and the environmental conditions. Common symptoms include:

• Yellowing and drooping of the leaves, which may eventually lead to leaf drop.
• Premature leaf drop, often starting at the top of the tree and progressing downward.
• Inner bark discoloration, turning a butterscotch or tan color.
• A distinct wintergreen odor emitted from the inner bark when it is peeled back.
• Dieback of branches and eventual tree death if the disease progresses unchecked.

Transmission

Elm yellows is primarily spread by leafhoppers, which are insects that feed on the phloem of infected trees and then transmit the phytoplasma to healthy trees. The disease can also spread through root grafts between adjacent trees.

Diagnosis

Diagnosis of elm yellows can be challenging due to the similarity of its symptoms to other elm diseases, such as Dutch elm disease. Laboratory tests, including polymerase chain reaction (PCR) assays, are often required to confirm the presence of the phytoplasma.

Management

There is currently no cure for elm yellows. Management strategies focus on prevention and control, including:

• Removing and destroying infected trees to prevent the spread of the disease.
• Controlling leafhopper populations through the use of insecticides.
• Planting resistant or tolerant elm species and cultivars.
• Avoiding the planting of elms in areas where the disease is known to be prevalent.

Affected Species

Elm yellows affects several species of elm, including:

• American elm (Ulmus americana)
• Siberian elm (Ulmus pumila)
• Winged elm (Ulmus alata)

See Also

• Dutch elm disease
• Phytoplasma
• Leafhopper
• Plant pathology

External Links

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