Summary

The role of various types of pollination — self, wind, and insect — on robusta coffee (Coffea canephora) was studied in the Kodagu (Coorg) region in Karnataka state in south India. Robusta coffee is generally thought to be wind-pollinated, with fruit set being enhanced if cross-pollinated by insects.

Many insects (as well as other arthropods and birds) can act as pollinators, but in this study bees made up nearly 97% of the floral visitors to the coffee. The main pollinator was the giant Asian honeybee (Apis dorsata, a relative of the familiar European honeybee).  Apis cerana and Tetragonula iridipennis were the other two bee species that most frequently visited coffee flowers, and together with the giant Asian honeybee comprised 98.3% of all visits to coffee flowers. While pollination can occur from wind, bee pollination increased fruit set by 50% over wind.

Amegilla bee on lantana. This genus of bees were once common in coffee plots, but now feed on non-native lantana flowers. Photo from Wikimedia Commons.

The authors noted that in other countries studied, the suite of pollinators usually comprised of many more species, rather than being dominated by so few as in the present study. They looked at a similar, though limited, study of pollinators of coffee done in the same area in 1915.  In that study, Apis cerana was the most common; this species has recently (early 1990s) declined due to a virus. The older study listed the second most abundant bees pollinating coffee as those in the genus Amegilla; in the present study these made up a mere 0.1% of visits.  The authors observed Amegilla bees foraging instead on a non-native invasive plant, Lantana camara. This indicates that invasive species may change the behavior of coffee pollinators — and this role of invasive species deserves more study.

The giant Asian honeybees nest in nearby forests in large trees. The authors concluded that, given the high dependence on pollination by this species, preservation of these trees in remnant forests within the foraging range of the bee is crucial to the successful production of coffee in this area.