A team of researchers nationwide is trying to get fruit growers back close to where they were before 2010, before the brown marmorated stinkbug made its probing presence felt.
That year, before they knew what was happening, apple growers in the Mid-Atlantic states lost an estimated $40 million. The apples they’d stored emerged dimpled with corky tissue—stinkbug feeding damage that made them virtually worthless.
And it was downhill from there as the bugs took on the peach crop and virtually anything else they could stick their probing mouthparts into.
Since then, it’s been costing growers more to spray to protect fruit because the stinkbugs are a season-long threat.
And, because of the need to spray repeatedly with pyrethroids and neonicotinoids, the IPM programs have been damaged. Growers had carefully built IPM programs to reduce pesticide applications and conserve natural enemies that kept secondary insects and mites under control.
Now, it appears, progress is being made to restore the balance.
During the Mid-Atlantic Fruit and Vegetable Convention in Hershey, Pennsylvania, in late January, three speakers addressed the subject: Dr. Tracy Leskey, who coordinates the overall national anti-BMSB effort from U.S. Department of Agriculture’s Appalachian Research Center in Kearneysville, West Virginia; Dr. Greg Krawczyk at Pennsylvania State University’s Fruit Research Center in Biglerville; and Dr. Anne Nielsen at Rutgers University in New Jersey.
A key first step is being able to monitor the insect’s activity. “The brown marmorated stinkbug is not a resident pest in your orchards,” Krawczyk told growers. The bugs spend most of their lives outside orchards, in other crops and in woodlands, and move into orchards. Growers need to know when that occurs.
Early on, researchers found a pheromone that attracted adult stinkbugs, but it was most effective late in the season and not good at detecting early arrivals. This aggregation pheromone was greatly improved with discoveries of a second sex-attractant pheromone and of a synergist.
“BMSB adults and nymphs are attracted to the two-component pheromone alone and in combination with the synergist all season long,” Leskey said. “Baited traps likely provide a representative sample regarding the presence and relative size of the population in the local area.”
She tested spray programs based on threshold levels—the number of insects found in a baited trap—and was able reduce the number of insecticide applications. Instead of using a standard regime of an alternate-row-middle spray every seven days, she was able to cut the number of sprays by 10 to 50 percent by waiting until the chosen threshold number of bugs had been caught.
“Baited traps can be used to make management decisions,” she said. “A threshold of ten adults per trap reduced insecticide applications by 40 percent with no significant difference in injury at harvest compared to weekly alternate-row-middle sprays.” She plans to repeat the experiment this year.
The trap combined the visual stimulus—the black pyramid—with the olfactory stimulus, and the pyramid contained a capture mechanism—a funnel jar treated with insecticide. Traps were placed in perimeter rows around the orchard, where insects enter from fields and woods.
The new trap was quite effective at luring and trapping insects—so much so Leskey believes attract and kill may be an option.
“It actually increased injury in the nearest neighbor trees to the baited traps, as this is an aggregation pheromone,” she said. In a small test, she baited a single tree and sprayed it, killing gallons of stinkbugs. “The trap tree looked like it was surrounded by a swarm of hornets,” she said.
Krawczyk tested several commercial traps that growers can buy and found they generally worked well.
“Commercially available BMSB lures and traps are effective in detecting the presence of BMSB adults and nymphs during the late part of the season,” Krawczyk said. “The addition of attractants enhanced greatly the effectiveness of the bait.”
Nielsen, who did early work with brown marmorated stinkbug when earning her doctorate at Rutgers a decade ago, returned there after a sojourn at Michigan State University and has resumed work on the bug. She spoke during the Mid-Atlantic fruit meeting about controlling the pest in peaches.
The stinkbug has forced growers to increase insecticide use by four times, she said. Biological control of secondary pests was lost as the IPM program was decimated by the new invasive bug and growers had to adopt the season-long weekly insecticide programs. Her goal is to restore what was lost.
In 2012, the program was refined somewhat when it was recommended that growers not spray until after 266 degree-days had accumulated.
Meanwhile, Nielsen has been working on a program she calls IPM CPR—crop perimeter restructuring—for better and less spraying. She tried it on three New Jersey farms again last year.
Instead of spraying entire orchards, only the perimeter trees plus one row was sprayed. In two years of tests, “at no site did we have higher injury in the CPR blocks,” she said. “It was always equal or less. We are stopping movement into the block and stopping injury.”
The program reduces reliance on sprays but requires increased reliance on mating disruption for control of oriental fruit moth. So, overall, insect control cost increases by $5 to $10 an acre, she said.
Hypothetically, the program should increase the population of natural enemies in the interior of the peach orchards and enhance biocontrol of secondary pests, such as scale insects.
Nielsen is also screening insecticides to find better options to neonicotinoid and pyrethroid insecticides, the ones most destructive of nontarget, beneficial insects. •