Jaramillo, J., A. Chabi-Olaye, C. Kamonjo, A. Jaramillo, F. E. Vega, H.-M. Poehling, and C. Borgemeister 2009. Thermal tolerance of the coffee berry borer Hypothenemus hampei: Predictions of climate change impact on a tropical insect pest. PLoS ONE 4(8): e6487. doi:10.1371/journal.pone.0006487.
A paper just published in the journal PLoS ONE explores the impact of climate change on the life history and distribution of the world’s worst coffee pest, a minute beetle called the coffee berry borer (CBB), Hypothenemus hampei.
The study modeled potential changes in mortality, number of generations per year, and developmental rate, among other traits, under eight different temperature regimes. The model indicated that CBB successfully develop at 20-30°C, and the intrinsic rate of increase (rate at which a CBB population increases in size) is highest, and the population doubling time lowest, at about 25-26°C (around 77°F).
As mean seasonal temperatures in coffee-growing countries move toward the optimum development temperatures for CBB, these areas become more vulnerable to increasing pest pressure from CBB. This could be especially problematic in Colombia, where multiple flowering of coffee plants means nearly year-round availability of coffee cherries.
The predicted optimal temperature for CBB increase is higher than that which is best for arabica coffee, which prefers a temperature range of 18-21°C (above which yields are reduced), while robusta coffee thrives at temperatures several degrees higher. Climate change is already predicted to reduce area suitable for coffee production. This is probably an even more pressing threat to coffee than changing pest dynamics.
As far as mitigation of the effects of higher temperatures on CBB and coffee production in general, the authors state:
A proven strategy to alleviate the potentially negative effects of climate, especially warmer temperatures, on coffee production is the introduction of shade trees in coffee plantations.
They point out that shade trees can lower temperatures around coffee by up to 4°C at low altitudes (<700 m) and 2°C higher up (>1100 m), that shaded farms harbor more CBB enemies which can provide bio-control of these pests, and that coffee cherry weight and quality is higher when grown under shade, thus offsetting lower yields.
A number of the authors are associated with the International Center of Insect Physiology and Ecology.
Photo of a female CBB entering an unripe coffee cherry, part of Figure 1 from the PLoS paper, photo by Gonzalo Hoyos of CENICAFE. Don’t discount small enemies.
Jaramillo, J., Chabi-Olaye, A., Kamonjo, C., Jaramillo, A., Vega, F., Poehling, H., & Borgemeister, C. (2009). Thermal Tolerance of the Coffee Berry Borer Hypothenemus hampei: Predictions of Climate Change Impact on a Tropical Insect Pest PLoS ONE, 4 (8) DOI: 10.1371/journal.pone.0006487