The latest development comes from the USDA’s Agricultural Research Service branch in Gainesville, Fla., where researchers have come up with an acoustic trap that fools the male insects into forsaking the females for a sticky death trap, leaving the ladies unfertilized and generations of the gnat-sized troublemakers unborn. Researchers are field-testing the trap this summer.
The insect that brings the disease is the Asian Citrus Psyllid, a moth about the size of a pinhead which, it should be noted, is present all over Texas. The psyllid transmits the bacteria that causes Huanglongbing, better known as citrus greening, which causes trees to bear green and misshapen fruit that produces unmarketable, highly acidic juice. The trees eventually die. There is no cure.
In Florida, the disease has cost growers about $7.8 billion in revenue, 162,200 citrus acres, and 7,513 jobs since 2007, according to a University of Florida Institute of Food and Agricultural Sciences studies. Citrus growers who responded to a UF/IFAS survey in March said they lost as much as 90 percent of their citrus acreage and that 80 percent of their trees had been infected.
The disease showed up in Texas in 2012 in an orchard in San Juan County.
Currently, quarantines to prevent trees being removed are in place for all of Cameron, Hidalgo and Willacy counties. Houston-area nurseries were likewise quarantined after infected trees showed up in nurseries there.
ARS entomologist Richard Mankin in Florida hopes his acoustic trap will prove to be an effective, economical and environmentally friendly solution to the Asian psyllid problem. Mankin designed the trap after years of studying the tiny insects to determine how they use their sense of smell, sight or hearing to locate food and mates.
While most traps for crop-damaging insects use pheromones — chemical attractants — Mankin’s trap mimics the wing-buzzing vibrations male and female psyllids use to locate and court one another in citrus trees.
Normally, the courtship works like this: The male sends out wing-buzzing vibrations and the female responds, letting the male know where he can find her. Mankin’s trap eavesdrops, responding a fraction of a second before the females with a fake signal, luring the unsuspecting male into a nearby sticky trap. (We’re sure the females blame the males for the whole fiasco.)
Economic losses in Texas have been minimal so far, but researchers aren’t easing up on their efforts. John da Graca, director of the Texas A&M Kingsville Citrus Center in Weslaco, said the disease hasn’t hurt production in Texas — yet.
“We’re not seeing the decline they have in Florida,” da Graca told the McAllen Monitor. “It may still happen, but certainly the disease progression is a lot slower than we’ve seen elsewhere.”
Erik Mirkov, a Texas AgriLife Research plant pathologist at the Texas AgriLife Research and Extension Center in Weslaco, has experimented with two bacteria-fighting genes found in spinach to see if they will attack the HLB in the same way. The experiments have worked in the laboratory and are being field-tested in Florida now. Citrus officials in Texas have said they believe disease-resistant trees are the best long-term solution to citrus greening.
Monte Nesbitt, a pecan, fruit and citrus specialist for Texas AgriLife Extension in College Station, said in a webinar last year that control of psyllids will be an ongoing problem, one that will have to be repeated as long as there are citrus trees where the Asian citrus psyllid is present.
“Regardless of the product you use, psyllids are going to repeatedly re-infest the citrus trees,” he said. “No single application of any one product can be expected to provide long-term control.”