Economists, farmers say overtreatment of coffee berry borer breaking banks

KAILUA-KONA — To spray or not to spray?

That’s no longer just a question of crop preservation for Kona coffee farmers trying to manage the coffee berry borer, but one with significant economic implications now nearly a decade since the invasive pest was identified as an industry threat.

“We still have a lot of farmers who are operating from a crisis mode, which is, ‘I need to spray every two weeks, and if I don’t do this my farm is going to fall apart,’” said local coffee farmer Suzanne Shriner, president of the Kona Coffee Farmers Association.

Shriner spoke Wednesday at King Kamehameha’s Kona Beach Hotel as part of a Coffee Berry Borer Conference put on by the University of Hawaii College of Tropical Agriculture and Human Resources (CTAHR) and the U.S. Department of Agriculture’s Agricultural Research Service.

She said since CBB was discovered in Hawaii coffee fields in 2010, management of the pest has been honed to a point that by incorporating correct monitoring practices, coffee farmers can be more effective with treatments while saving themselves thousands of dollars annually.

Based on calculations, Shriner said it costs roughly $100 per acre to administer BotaniGard, the most common defense against CBB in which the active ingredient is a naturally occurring fungus, Beauveria bassiana. Many farmers are spraying upward of a dozen times per season, but Shriner said four or five times is all that’s actually necessary.

And even on a small farm, the difference quickly adds up.

“About 30 percent of farmers have (the treatments) really dialed in,” she added. “The other 70 percent are spending way too much trying to control this beetle.”

Andrea Kawabata, an extension agent with CTAHR, said the key is getting to the pest early in the season.

“You have to start spraying early, and you need to know when flowering is happening and time it according to your flowering,” she explained. “If you let it go, once those berries become mature, the seed becomes hard and (the beetle) is able to go … directly into the bean. It’s very difficult to control CBB at that point.”

Shriner and Kawabata both promoted the 30-tree method. The method, scaled to the needs of a 5-acre farm, calls for picking cherries with holes in them from 30 different trees and opening them up.

If the CBB is near the outer edge of the bean, spraying is prudent. If it’s burrowed into the center, the damage is done and treatment amounts to spraying dollars needlessly into the wind.

Kawabata advised farmers to begin spraying between January and March, depending on the timing of flowering. Shriner said over the last few years, she’s never treated her crop later than early August.

“That saves us a lot of money by ending early,” she said.

Stuart Nakamoto, extension economist with CTAHR based on Oahu, told the crowd at the conference that the lower initial infestation rate, the more economically viable spraying will be. The key, he explained, is to correctly determine the window for the initial spray.

Cost-benefit analysis of spraying should also take into account expected yield. A few decades ago, Nakamoto said, the average yield per acre was 80-100 bags. He added based on current agricultural statistics, that number is now closer to 30-50 bags per acre.

“If you had an acre of coffee and you went out to spray, it’s going to cost you the same amount whether you get 10 bags of coffee or 100 bags of coffee off that acre, yes?” Nakamoto posed.

Both Kawabata and Nakamoto also stressed the importance of testing for root-knot nematode, which impacts the health of coffee trees and can have a profound effect on overall yield.