PVCC Puma Press

Citrus greening disease threatens citrus throughout the U.S.
By Lisa Racz, November 2009
Environment Editor

Citrus greening disease, also called Huanglongbing, is actually a very serious virus that destroys citrus crops worldwide and is carried by a tiny insect called a psyllid that is no bigger than a gnat.
How does this insect spread the disease?

“Basically the virus is in the nutrient or fluid of a plant. So when the insect sucks liquid from the infected plant and goes to another uninfected plant and feeds, the remnants of fluid from the infected plant gets placed in the newly fed on plant,” says Brian McGrew, quarantine program coordinator with the Arizona Department of Agriculture.

There are two types of quarantines. One for citrus carrying the insect alone and the other for citrus that carries the virus.

“Citrus plants containing the virus may not have any insects and some psyllids may not carry the virus because they have not fed on an infected plant yet,” says McGrew.

Citrus greening is a threat to the United States citrus industry and many states such as California, newly hit with greening, Texas and Florida have been placed under quarantine for the citrus greening disease since there is no cure once a tree is infected. In Florida, the citrus sunshine state, the hostile greening disease has almost annihilated the entire state’s citrus crops since the discovery of the disease in 2005. The origin of the disease has been released to the public stating that it has originally come from China.

Citrus plants that are infected by the greening virus have symptoms such as yellowing or blotchy leaves that appear on a single branch, stunted growth of foliation and most noticeable is the deformed, lopsided half green and unripe production of fruit.

“The disease doesn’t allow citrus to fully ripen, if at all, and the fruit remains green and very inedible,” says McGrew. “That’s how the disease got its name.”

Arizona is known as a citrus growing state yet has not been hit with the greening virus because of Arizona’s hot desert location and due to precautionary measures that the Arizona Department of Agriculture is taking to prevent the virus from entering Arizona.

“Arizona has been planning for over a year on how to keep the virus out of our state,” says McGrew. “Arizona will not take risks by taking in any citrus plants from high quarantined states such as California (or from) Mexico. Whether or not there are any signs of either the insect or the virus. Arizona is the only citrus producing state without the virus because of a big gap of hot desert between California and Mexico, which helps prevent the infected insect from crossing over and infecting Arizona’s citrus.”

Nurseries throughout the U. S. are taking precautions and have certain quarantine rules to follow in order to prevent the spreading of the disease.

“The disease not only attacks citrus, but other plants become hosts as well like herbs such as curry leaf and bushes like Orange Jasmine, which is not allowed in Arizona anymore as of last year,” says McGrew. “All citrus goes through a registration process to trace where trees come from. Nurseries are not allowed to take plants from any quarantined state.”

Though Arizona is not among the quarantined, the Arizona Department of Agriculture is constantly taking precautions to prevent any citrus greening from hitting home.

“The Department of Agriculture is constantly stetting out sticky traps around citrus plants throughout the state to check if there are any Asian psyllid captured and monitoring any changes with citrus plants for possible greening virus,” says McGrew.