Oranges glow in the Arizona sunshine.Listen:
By Amanda Solliday, Arizona Science Desk
YUMA - Arizona's citrus industry has escaped a tree-killing bacterial infection that is plaguing the three other states that grow citrus commercially. Researchers want to know if climates like Arizona’s offer citrus trees some natural protections against greening.
A small insect called the Asian citrus psyllid feeds on trees. It can transmit bacteria that lead to citrus greening disease, which causes a decline in fruit quality and eventually kills the infected trees.
In Arizona, where citrus is a $37 million a year industry, the psyllid has been spotted in commercial groves in Yuma County and on residential trees in Maricopa County. But so far, none of the insects carried the disease.
The psyllid has infected and killed citrus trees in Florida, California and Texas, all of which have much bigger citrus industries than Arizona.
Glenn Wright, a fruit tree specialist at the University of Arizona's Yuma Agricultural Center, said hot, dry weather may be protecting trees in the state.
"Arizona is the last major citrus producing state that does not have, has not been affected by greening," Wright said. "And it is in an unenviable position because of that."
Research in Brazil shows greening is less common in hot areas than cool parts of the country, Wright said, adding that scientists have placed infected young tree branches in a heat chamber set around 110 degrees Fahrenheit. That can eliminate the bacteria.
Heat can also change how citrus trees grow. Wright said high temperatures paired with low humidity slow growth during the summer. And psyllids prefer to feed on new tree tissue.
"And so there’s only a limited amount of time in Arizona where the psyllid can feed on the part of the citrus that it really likes," he said.
Wright said he will further study the effects of heat on citrus greening with colleagues at the University of California Davis and the University of Florida.
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