Elm yellows is a

plant disease Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...

elm Elms are deciduous and semi-deciduous trees comprising the flowering plant genus ''Ulmus'' in the plant family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North ...

trees that is spread by leafhoppers or by root grafts."Elm Yellows." Elmcare.Com. 19 Mar. 2008 . Elm yellows, also known as elm phloem necrosis, is very aggressive, with no known cure. Elm yellows occurs in the

eastern United States The Eastern United States, commonly referred to as the American East, Eastern America, or simply the East, is the region of the United States to the east of the Mississippi River. In some cases the term may refer to a smaller area or the East C ...

, and southern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

in Canada. It is caused by

phytoplasmas Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-lik ...

which infect the

phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is c ...

(inner bark) of the tree.Price, Terry. "Wilt Diseases." Forestpests.Org. 23 Mar. 2005. 19 Mar. 2008 . Similar phytoplasmas, also known confusingly as 'Elm yellows', also occur in Europe.Conti, M., D'Agostino, G., Mittembergher, L. (1987) A recent epiphytotic of elm yellows in Italy. ''Proceedings of the 7th Congress of the Mediterranean Phytopathological Union'', 208–209. Consejeria de Agricultura y Pesca de la Junta de Andalucia, Granada, Spain Infection and death of the

effectively girdles the tree and stops the flow of water and nutrients. The disease affects both wild-growing and cultivated trees.

Importance

Elms are very important to the American landscape, prized for their unique shade characteristics. Most native elms are susceptible to elm yellows and there are few resistant cultivars. Large, healthy, landscaped elm trees can easily be worth thousands of dollars. Penn State University is home to one of the oldest and largest elm stands in the country. Penn State has been battling

Dutch elm disease Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into Americas, America ...

for many decades, and the recent introduction of elm yellows into the Penn State campus poses many threats.Ruskin, Paul. "Penn State Prepares for 'Elm Yellows' Disease." PSU Live 12 Nov. 2007.19 Mar. 2008 . A tree near the university president’s house had to be removed and numerous trees in

State College, Pa State College is a home rule municipality in Centre County in the Commonwealth of Pennsylvania. It is a college town, dominated economically, culturally and demographically by the presence of the University Park campus of the Pennsylvania Sta ...

have died or have been removed due to elm yellows. Elm malls across the US are at risk of being destroyed by elm yellows.

Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

, for example, had a large elm collection which was being managed for Dutch elm disease, much like Penn State, but once elm yellows had spread to the campus, all of the elms were destroyed within a matter of years.

Transmission

In North America the disease is transmitted from infected to healthy trees by the whitebanded elm leafhopper ('' Scaphoideus luteolus'' Van Duzee), the meadow spittlebug (''

Philaenus ''Philaenus'' is a genus of insects belonging to the family Aphrophoridae, the spittlebugs. The meadow spittlebug ''Philaenus spumarius'' is a common insect in much of the Northern Hemisphere, and it is sometimes a pest on crops such as alfalfa ...

spurarius'') and by another leafhopper ('' Allygus atomarius''), although other insects are also suspected of being vectors. Transportation of nursery trees is another way for elm yellows to be spread over long distances. As leafhoppers move very slowly so movement of elm yellows has been slow.

Symptoms

When an elm is infected with elm yellows, the root hairs die. The phytoplasma infection then moves up the bark and infects the phloem, depriving the tree of nutrients. Death of the phloem essentially strangles the tree. As the phloem is infected, it will change color and take on a wintergreen smell, similar to that of

black birch Black birch is a common name for several trees, and may refer to: * Asian black birch, the English name for '' Betula dahurica'', tree species native to eastern Asia * Black birch, a common name for ''Betula lenta'', tree species native to eastern ...

birch beer Birch beer is a beverage, commonly found as a carbonated soft drink made from herbal extracts and birch bark. It was originally made from the extracts of both oak and pine barks (which are sometimes combined). There are dozens of brands of birch ...

. The crown, top of the tree turns yellow all at once, it can occur from July till September, when the leafhoppers are active."How to Differentiate Dutch Elm Disease From Elm Phloem Necrosis" US Forest Service. 1981. Accessed: May 29th 2016 . It turns yellow from a lack of nutrients to the top of the tree.

Control

Aggressive control is needed if trees show symptoms of being infected. Time is of the essence since nearby trees may already be infected. Removal and destruction of the infected tree is the first step, followed by trenching around the next two rows of trees near it to isolate infection. Spraying trees with insecticide will also help reduce the chances of transmission by leafhopper. Injecting trees with

tetracycline Tetracycline, sold under various brand names, is an oral antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. Common side effects in ...

antibiotics has been shown to slow the progress of elm yellows. Tetracycline inhibits protein synthesis by preventing

tRNA Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino ...

from attaching to the Ribosome."Antibiotics." Elmhurst.edu. 30 May 2016. . Phytoplasma bacteria do not have a Cell wallJacqueline Fletcher and Astri Wayadande. "Fastidious Vascular-Colonizing Bacteria." apsnet.org. 2002. Accessed: 30 May 2016. . Since Elm yellows and other phytoplasma do not have cell walls, most antibiotics will not be effective, this is why tetracycline and antibiotics that target internal functions of the cell are needed.

References

{{Reflist, 2 Bacterial tree pathogens and diseases

Importance

Transmission

Symptoms

Control

See also

References