—by Ross Courtney
Researchers and consultants are attempting to count beneficial insects in and around pear orchards near Hood River, Oregon, using sticky card traps with lures, to inform integrated pest management decisions.
Not that there’s a single correct way to scout for predators, but Jeff Heater prefers the traps, paired with four lures scented with plant volatiles, over the traditional approach of tapping on a branch and quickly identifying what drops onto a tray before the insects fly off.
“Sticky cards are so much faster,” said Heater, a G.S. Long Co. crop consultant.
Heater has tried beat trays, but he gave up on them because he didn’t think he was finding enough beneficials to make the effort worth it. Now, he just changes the hanging traps once per week during his rounds, and he likes the results.
Together, he and his counterparts at Wilbur-Ellis and Chamberlin Agriculture manage about 50 trapping sites throughout the Hood River Valley. They count lacewing, deraeocoris, trechnites and other predators and send the data to Chris Adams, Oregon State University entomologist at the Mid-Columbia Agricultural Research and Extension Center in Hood River. Heater makes his counts then delivers the cards to Adams, so he can offer another set of eyes.
The consultants use their site-specific counts to advise their clients, while Adams crunches the data and sends it out via his weekly entomology updates for the whole area.
The goal is to establish formal thresholds for the beneficial populations to help inform spraying and other IPM decisions.
“It’s going to take years to figure it all out,” Adams said.
Adams had been experimenting with the traps with partners in Washington under a three-year Washington Tree Fruit Research Commission grant. During that project, they found correlations between psylla and predator populations. Not surprisingly, when they had a lot of predators on the traps, they measured less psylla pressure. Adams also found the traps tracked year-to-year cycles in psylla and natural enemy populations.
The project wrapped up with some leftover lures, so Adams issued them to the local consultants to keep the data flowing. Adams has applied for Western Sustainable Agriculture Research and Education funding to continue the project and offer those consultants some predator identification training.
It’s not as if Adams hates beat trays, the scouting method researchers and crop consultants in Washington are using to track beneficial populations and make threshold-based management decisions. His team is using them to contribute data for Robert Orpet, a Washington State University collaborator also studying beneficial insect populations.
Both methods have advantages.
The sticky cards skew toward adult flying insects attracted to the four plant volatiles. Deraeocoris, lacewings and yellow jackets are common catches. They would fly away the moment you whack a branch for a beat tray sample.
And don’t worry: The cards hang on just a few sample trees and won’t trap enough bugs to diminish the population and undo the benefit of beneficials, Adams said.
The traps don’t net many earwigs or spiders, psylla predators that do not fly or use plant volatiles to track prey, Adams said. Beat trays are better for those.
That’s why Chamberlin Agriculture staff are still using both.
“Is there a way we could blend the two together?” said Bruce Kiyokawa, a Chamberlin crop advisor.
The method is still new, so thresholds are not yet canonized. But the traps have informed decisions while Adams builds his database, Kiyokawa said.
“It’s given us the confidence in some cases to say, ‘Let’s let it go another week to see what happens,’” he said.
In March, one of Heater’s traps caught 100 deraeocoris, prompting him to advise a grower to entirely skip early spring sprays. It turned out that the neighboring block had just been sprayed with Surround (kaolin). Heater speculates that pushed the predators into his block.
Later, in the heat of summer, the same trap also caught high counts of yellow jackets and bald-faced hornets.
The orchard almost never has psylla pressure; Heater figures the predator population is why.
That revelation made him excited about Adams’ sticky card idea. He had been skeptical up until that point.
“That’s probably the one example that caused me to get enthusiastic about this project,” he said. •
Leave A Comment