What is in this article?:
- A U.S. research collaboration is under way, funded in part through a $9 million USDA grant, which has the Asian citrus psyllid (ACP) pest directly in the crosshairs.
University of Arizona scientist Judith Brown uses knowledge gained from research on the potato psyllid on tomato plants in her ground-breaking work to control the Asian citrus psyllid in the fight against the disease Huanglongbing in citrus.
Going for the gut
“We are working to develop a modified Asian citrus psyllid with biological changes to the insect’s gut and salivary glands to halt bacterial uptake,” Brown explained.
The Brown team has learned that large numbers of Liberibacter bacteria pass into the insect’s alimentary canal (gut). The bacteria cause lesions in the gut. This could be tied to an enzyme or toxin generated by the bacteria or the psyllid.
It appears that as the gut wall breaks down, bacteria enter the blood stream and move to the salivary glands. As an infected psyllid feeds on the citrus tree, the bacteria are released causing Liberibacter infection.
Several years can pass after the initial infection before the tree shows visual symptoms, which include mottled leaves and tree yellowing. Fruit from diseased trees is pithy, tastes bitter, and is unmarketable.
Brown is confident her research team will be successful.
“We know which organs to target and how to feed the RNA inside the psyllid. I believe we will find answers to stop the problem at the psyllid level.”
Brown hopes to have an early modified insect to test in the next four or five years.
Brown says gains in past research projects have formed the foundation for current research work. The knowledge gained in this current wave of psyllid research by her and other researchers can be extrapolated for future vector management issues.
“We are hoping this new generation of knowledge and applications will open the door for important improvements in how we study and manage pest complex problems in all crops,” Brown said.
HLB was first found in the U.S. in 2005 in Florida which has led to millions of dollars in economic losses. Two cases of HLB were found in Texas citrus groves last year.
A single case of HLB was found in California in Spring 2012 in a residential citrus tree near Los Angeles. The tree was quickly removed and destroyed. The Liberibacter pathogen and the disease it causes have not been detected in California commercial citrus.
Likewise, the psyllid has been found in several southern Arizona locations. HLB has not been found.
The western U.S. is the last citrus-growing area in the world to get HLB. Some California citrus leaders contend a severe outbreak of HLB in California groves could wipe out the state’s $2 billion commercial citrus industry. The same could be the case for Arizona’s $37 million citrus industry.
Thousands of psyllids are in the Los Angeles area and moving into commercial citrus. Every psyllid found in commercial citrus has tested negative for HLB.
Until now, ACP-HLB research has focused on a variety of possible HLB solutions, including the psyllid itself, the development of HLB-resistant tree varieties, parasitic wasps, and other methods. The USDA funded research strictly targets the psyllid.
The grant-funded research is underway in Arizona, California, Florida, and Texas. The UA team, working collaboratively with the David Gang lab at Washington State University, will receive about $870,000 in grant funds.
MaryLou Polek, vice-president of science and technology with the California Citrus Research Board, is very involved in the fight against the psyllid and disease.
Polek helped write the exhaustive 900-page USDA grant application, along with project director Tom Turpen of Florida, and other researchers.
“I am confident that though cooperation and collaborative research that viable solutions will be found within the next 3-5 years,” Polek said.