sikkim's most important cash crop is ailing. India's biggest producer of large cardamom, Sikkim, has recently witnessed a sharp fall in crop yields, forcing many farmers to abandon large cardamom plantations.
The decline has been largely attributed to a spate of viral and fungal infestations over the past three decades. But new research says pollen theft by a local breed of honeybees, which farmers maintain to facilitate pollination, could also be a major cause.
K R Shivanna, the biologist who led the two-year study in Sikkim, says that a native bumblebee species (Bombus haemorrhoidalis Smith) is the only effective pollinator of the cardamom flower. "Hardly any studies have been done on the pollination biology of large cardamom. There's just one old report that says honeybees are the pollinators based on the number of times bees were observed visiting the flowers," he says.
The biologists note that the flower of the large cardamom is better adapted for pollination by the bumblebee. The flower's nectar is protected in a 3 cm long nectar tube which is formed by the fusing of its petals with the labellum--the large central petal or lip of the flower. The nectar is thus accessible only to insects with a long proboscis--elongated sucking mouthpart.
The honeybee, with its short proboscis, buzzes in and out of same flower several times, trying in vain to reach the nectar. In the process, it depletes the flower of its pollen but is usually unable to penetrate it deep enough to effect pollination. Meanwhile, the bigger bumblebee, with its longer proboscis, penetrates the flower, sucks out the nectar and flits on to the next bloom, transferring pollen effectively.
So, the honeybees are "pollen robbers", says Shivanna. He adds that the decreasing population of the local bumblebee, possibly due to its habitat degradation, is yet another factor behind the low crop yields. "India lacks the technology to rear bumblebees, though the technology exists in the west," he says.
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