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PLP407 Lecture 16


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What is a phytoplasma and how does it spread? How might you control a phytoplasma disease? Name 2 diseases that are caused by phytoplasmas.
A phytoplasma is a bacteria without a cell wall; it cannot survive in the open. They are spread by pircing and sucking insects and are present on the mouthparts. COntrol is limited to removal of the infected plants and control of the vectors. Ash yellows and X-disease of peach and cherry
Ash yellows- discribe the disease
Disease- phytoplasm Vector- leaf hopper and aphids Symptoms- witches broom, basal stem cracks, chlorosis Control in forest- clear out the dead and dying trees and select for resistant trees Control in landscape- Keep growth vigorous and keep dead branches pruned off.
what are four symptoms of phytoplasma disease?
Witches broom, flowers turning into leaves, foliage turning yellow, epicormic branching, bud breaking out of season.
List three diseases caused by phytoplasmas.
Ash yellows Palm and ash yellow Elm phloem necrosis
What is one distinct Characteristic of Rickettsiales? What is one disease caused by Rickettsiales? Where in the plant are they found and how are they transfered?
Rickettsiales are bacteria that have thin cell walls. One Rickettsiales disease causes leaf scortch and burn. Rickettsiales is found in the xylem and transported by spittlebugs and sharpshooters.
If we can cure these trees infected with phytoplasmas by injecting them with antibiotics then why dont we do that?
Over use of antibiotics can result in resistance which can result in host jumping and can eventually end up affecting humans.
Why does Gerry think it is rediculous for the government to list the citrus strain of fastidiosa as the one and only bacterial plant disease to be listed as a “select agent” with potential as a biochemical warfare weapon?
Because this disease cannot survive outside of its host. its an obligate organism and extremely difficult to culture in mass amounts. And if cultured, it must be vectored by giant leafhoppers...which dont exist.
Gerry is studying ash yellows in Michigan. Why is there reason to study this disease on trees that are doomed to die by EAB?
Ash forests have just reached maturity and this might be the last time to gather information that might be useful in future studies of how to manage ash forests in the future.
Gerry is studying bacterial leaf scortch in 11 northcentral plain states. Why is it important to understand/document the distrabution of BLS?
BLS leads to the decline in oaks. Knowing the current distrabution can help us estimate the future impacts of BLS due to global climate change
⬢ Pierces disease of grapes in California is caused by xylem limiting bacterium Xylella fastidiosa has suddenly become a very serious problem, even though the disease has always been present there at low incidence. Why?
A new exotic vector has arrived, the glass-winged sharpshooter, which is more efficient in transmitting the disease than the native ones have been in the past.

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