New study shows how HLB bacterium changes bug behavior patterns

Citrus greening promotes its own spread, according to researchers

SOMETIMES, Mother Nature is just not very nice to the agriculture industry, as a recent study by University of Florida researchers stands to confirm. Citrus greening, according to the five researchers involved, has a built-in, bug-driven method of spreading itself far and wide — making it more difficult to deal with. Asian citrus psyllids fly earlier in their life cycles, farther, and more frequently when they are infected with the citrus greening (HLB) bacterium.

In other words, carrying that citrus-destroying cootie just fires them up to fly sooner, go farther, and venture out more often.

The results of the study have global implications for how the disease spreads — and for approaches to control it, researchers say. Kirsten Pelz-Stelinski and the team of researchers at UF’s Institute of Food and Agricultural Sciences’ Citrus Research and Education Center in Lake Alfred conducted the study.

The threat to the Sunshine State’s $10.7 billion citrus industry appears to be even more ominous with the knowledge that insect behavior is impacted in that way. “To our knowledge, this is the first description of direct changes to insect behavior caused by a bacterial pathogen in an insectplant-pathogen system,” Pelz-Stelinski elaborates. “These newly discovered behavior changes seem to increase dispersal of the insect — and thus the disease.”

Citrus greening bacterium finds its way to trees initially by way of the psyllid. The pest sucks on leaf sap and leaves the greening bacteria behind. The bacteria travels, then, through the veins of the tree. The disease deprives trees of nutrients and damages roots. Trees produce green or misshapen fruits, not suitable to sell as fresh fruit or — most of the time — for juice, until eventually the tree is no longer able to produce fruit and dies.

Found initially in Florida in 2005, it has carved a lethal path through groves. From 2004 to 2011, the state’s commercial citrus acreage and number of trees decreased 28 percent. Greening is one of the primary reasons for the decrease, along with development.

Most infected trees die. Citrus greening has harmed millions of North America citrus trees; recently, it was found in California. The devastating bug doesn’t live long enough to cause so many problems: adult psyllids have a lifespan of about 40 days at 77 degrees Fahrenheit.

Control of the spread of citrus greening is now limited to methods such as the removal and destruction of infected trees and insecticide-based management of the population of psyllid.

But researchers are diligently working to wipe it out in various ways, such as eradication of the psyllid, breeding rootstock with higher resistance to greening, and testing various ways to treat trees.

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