Elm yellows

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elm4

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TreePhloem

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Trench digger lge

Elm yellows (also known as elm phloem necrosis) is a plant disease that affects species of elm trees. It is caused by a phytoplasma, a type of bacteria that lacks a cell wall and is obligate to the phloem tissue of plants. The disease is characterized by the yellowing and wilting of leaves, followed by the death of the tree.

Symptoms

The primary symptoms of elm yellows include:

• Yellowing of the leaves, which may start at the tips and edges and progress inward.
• Premature leaf drop.
• Phloem necrosis, where the inner bark turns brown and emits a wintergreen odor.
• General decline in tree vigor, leading to eventual death.

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 diseases such as Dutch elm disease. Laboratory tests, including DNA-based 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 include:

• 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.

Affected Species

Elm yellows affects several species of elm trees, including:

• American elm (Ulmus americana)
• Winged elm (Ulmus alata)
• Slippery elm (Ulmus rubra)

Related Diseases

• Dutch elm disease
• Phytoplasma

See Also

• Plant pathology
• Phloem
• Leafhopper