Coffee berry borer (Hypothenemus hampei) is considered the most devastating insect pest of coffee worldwide and was detected in Hawaii in 2010. The adult female (left) bores a hole into the coffee fruit (“berry”) and eventually into the seed (“bean”), where she digs tunnels to her lay eggs. The larvae feed on the endosperm (seed) tissue causing direct damage to the bean (right).

By Melissa A. Johnson, Ph.D.

Melissa A. Johnson, Ph.D.

Coffee is one of the most economically important crops in the State of Hawaii, and coffee produced in the islands is known globally for its high quality. The growing location, fertile volcanic soils, and variable microclimates all contribute to the unique profile of coffee from this region. More than 1,000 coffee farms operate in the state, most of which are small, family-owned farms less than five acres in size. Due to the rough terrain and close spacing of trees, these small farms rely on seasonal workers to harvest the coffee berries by hand.

Coffee berry borer (Hypothenemus hampei, hereafter abbreviated as CBB) is considered the most devastating insect pest of coffee worldwide and was detected in Hawaii in 2010. This tiny beetle infests the coffee seed (“bean”) and reduces the yield and quality of coffee products. With the introduction of this pest, growers have faced a significant challenge in producing the specialty coffee that the region is known for.

On small family-owned coffee farms in Hawaii, such as these in the Kona (left) and Ka’u (right) districts of Hawaii Island, coffee is hand-picked by seasonal workers due to the rough terrain and close spacing of trees.

Integrated pest management (IPM) guidelines to control CBB have been developed for Hawaii, with the recommendations including monitoring, field sanitation, biopesticide applications, and frequent and efficient harvesting. A combination of these control practices can result in the successful regulation of CBB populations and the production of high-quality coffee if the biology of the beetle and phenology of the coffee crop are considered.

While considerable research and effort have been invested into chemical and biological controls for CBB, cultural controls including pruning, sanitation, harvesting, and strip-picking (removal of all green, ripe, and over-ripe berries at the end of the season) are widely considered the most important strategy for managing CBB.

The CBB completes most of its life cycle within the coffee fruit, where it is protected from natural enemies and pesticide sprays. Each fruit can harbor hundreds of CBB and serve as sources of new infestations. The adult female CBB is only vulnerable when it leaves its natal berry to fly and look for a new berry to infest; sprays must be accurately timed with mass flight events (which typically occur early in the season and post-harvest) to be effective.

Coffee cherry (ripe berries) are gathered via standard harvesting rounds (left), while green, ripe, and over-ripe berries are gathered in end-of-season strip-picks (right). Coffee berries serve as reservoirs of coffee berry borer (Hypothenemus hampei), with each berry harboring potentially hundreds of borers that serve as sources of new infestations.

In contrast, the practice of frequent and efficient harvesting acts to remove reservoirs of CBB from farms. By frequent removal of coffee fruits from farms, growers can disrupt the life cycle of CBB and ensure that they start the new season with low infestation. However, frequent and efficient harvesting is often considered too expensive and labor intensive by growers, particularly in Hawaii, where production and labor costs are higher than any other coffee-producing region in the world.

In a study published in March in the Journal of Economic Entomology, my colleagues Luis Aristizábal, Suzanne Shriner, Marisa Wall, Ph.D., and I examined two CBB management strategies across 10 commercial coffee farms on Hawaii Island: (1) conventional management including frequent sprays of pesticides and few rounds of sanitation and harvesting, and (2) cultural control-focused management consisting of few sprays of pesticides and frequent sanitation and harvesting. Our aim was to determine the costs and benefits of each practice to provide growers with the information necessary to make the most economically viable choices for CBB management.

Results showed a significant positive impact of frequent and efficient harvesting (strategy 2) on the regulation of CBB populations. Over two consecutive coffee seasons, farms that used a combination of frequent harvesting and few pesticide applications exhibited significantly lower CBB infestation, better harvesting efficiency, higher harvested yields, higher quality of processed dried coffee, and higher net profits from the sale of harvested coffee compared to that of conventionally managed farms. In addition, the cost of chemical controls was 55 percent lower, and the net benefit of frequent harvesting was 48 percent higher on cultural versus conventional farms. Our findings demonstrate that frequent and efficient harvesting is an effective and economically viable alternative to frequent pesticide applications.

Management of coffee berry borer (Hypothenemus hampei) via cultural control emphasizes frequent and efficient harvesting of berries (left) and few sprays of pesticides, while conventional management emphasizes frequent pesticide sprays (right) and few harvesting rounds.

Frequent harvesting as an effective method of control for CBB in Hawaii will depend on farmers securing enough pickers to conduct frequent harvesting and coffee pickers receiving proper guidance and training in how to optimize sanitation picks, standard harvesting, and strip picks. Field workshops will likely be most effective in training pickers. The demonstration of proper technique could help to overcome any language barriers that may exist between farm owners and workers, particularly in Hawaii, where most of the coffee laborers are from Latin America, the Philippines, and Micronesia.

Further economic analyses that determine the costs and benefits of processing and roasting coffee with varying levels of quality could provide additional decision support for growers in selecting the best management strategy to reach the desired financial outcome.

Melissa A. Johnson, Ph.D., is a research biologist at the U.S. Department of Agriculture-Agricultural Research Service’s Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center in Hilo, Hawaii. Email: melissa.johnson@usda.gov.

All photos courtesy of Melissa A. Johnson, Ph.D.