Reducing the coffee berry borer population at the get-go and keeping the pesky bug at bay with a once-a-month spray of Beauveria fungus appears to give the best bang for the buck, a scientist told coffee farmers at an expo Friday in Kailua-Kona.
Three straight weeks of spraying the fungus early in the season can reduce the berry borer population enough that farmers can effectively control the borer during the remainder of the season by spraying the fungus just once a month, said Lisa Keith, a plant pathologist with the U.S. Pacific Basin Agricultural Research Center based in Hilo. The finding is based on an ongoing study of the fungus’ persistence and efficacy at three South Kona coffee farms that started in April.
Keith presented the research during the Kona Coffee Farmers Association’s annual Kona Coffee Expo and Trade Show held Friday at Old Kona Airport Park’s Makaeo Events Pavilion. The six-hour event, now in its seventh year, featured dozen of exhibitors providing information and products to farmers as well as workshops and speakers.
“You don’t have to do that two sprays — definitely not more than one,” Keith said, presenting data from farms located at the 1,869-, 535- and 450-foot elevations. The study did not include a control, or untreated, farm.
However, she cautioned, every farm and situation is different.
“As you’re going along the season, there are still times of the year that a variety of things are going on, which means there’s probably a general time of spraying,” she said. “But, you’ll need to be looking because there will be additional times that you will need to spray.”
For example, at the highest elevation farm, located in Honaunau, there was a high population of the beetle early in the season, around May, and three consecutive weeks of spraying knocked back the infestation, she said. Monthly sprays thereafter kept the coffee berry borer at bay.
At the lower elevations, the knock-back spray initially followed by the monthly sprays also helped keep the borer numbers down, though the infestation was less severe at the start.
“The product definitely works and it helped maintain a much lower level over time,” Keith said. She later noted that the research indicated farms at lower elevations, with less infestation from the start, might not need the Beauveria sprays as often as higher elevation farms.
As a possible example of the regimen being successful, Keith pointed to October’s federal government furlough, which left scientists unable to spray and study the farms for about a month.
“The trend was very low until the spraying stopped,” Keith said. “Then we saw the beetle increase, giving further evidence the product works.”
The findings, though yet to be published in a peer-reviewed journal, are exciting, Keith said, because they mean farmers likely don’t need to spray twice a month, effectively reducing the cost of battling the coffee berry borer. Diluted at one quart of fungus to 100 gallons of water, Keith said it costs, depending on the size of the farm, approximately $50 to $100 per application.
“The goal is to be economically viable as well,” Keith said, also noting cost-savings from labor applying the product.
The study, which collaborated with the University of Hawaii at Manoa, is funded via a $1 million U.S. Department of Agriculture grant the research center received in 2013 to study and mitigate the effects of the coffee berry borer.
Native to Africa, the coffee berry borer is a small, dark-brown beetle about the size of a sesame seed that was first confirmed in the Kona area in September 2010, Ka‘u in 2011 and Hilo in October. The pest destroys coffee when the female burrows into the fruit and lives its life cycle within the seed, or bean, causing damage that can make the coffee relatively worthless.
The center’s research also found that farmers should spray the fungus after 3 p.m., Keith said, noting the fungus doesn’t thrive when subjected to high ultraviolet levels, heavy rain and high temperatures.
In addition, the early knockdown of the coffee berry borer appeared to positively affect the finished product’s size, she said.
“When you start controlling the beetle, the size of the cherry got better,” Keith explained, noting the study indicated farmers should increase fungus use near harvest to keep levels high. “We know the beetle is affecting the product, but with the spray and control it’s possible to reduce that.”
The fungus is just one component farmers need to use to be successful in reducing the effect of the beetle, she emphasized throughout the presentation.
“We’re starting to see better trends that the product can be used as a general management scheme,” she said. “No matter where you are, it’s effective.”
“Beauveria alone is not the substitute for sanitation,” Keith said. “Start with sanitation then work in a manageable Beauveria management plan and then we’re definitely seeing good results.”