The Role of Insects in the Pollination of Durian (Durio zibethinus Murray) Cultivar 'Monthong'

Abstract

The durian (Durio zibethinus, Malvaceae) cultivar 'Monthong' is among the most tasteful cultivars and is grown widely throughout Thailand. Nocturnally-foraging insects may be supplementary pollinators to bat-pollinated plants when bats are scarce. Previous studies have stated that insects visit durian flowers, yet no studies have assessed the role of insects in 'Monthong' durian pollination success. Four pollination treatments were conducted on 19 trees from three durian orchards in southern Thailand. Stigmas were receptive by 17h00, and over 50% of 'Monthong' anthers had dehisced by 17h30. Several bee species began foraging on flowers during the late afternoon, and the giant honey bee (Apis dorsata) continued to visit throughout the night. At two weeks after pollination, average percent fruit set was highest for hand-crossed pollination (39.3%), followed by open pollination (31.1%), automatic autogamy (19.6%) and insect pollination (16.4%). The yields from insect pollination, open pollination, and automatic autogamy were not significantly different, but hand-crossed pollination was significantly greater than automatic autogamy. At four weeks after pollination, fruit set from hand-crossed pollination (13.5%) still differed significantly from automatic autogamy (2.0%), indicating that this cultivar is highly self-incompatible. Moreover, the yields of open pollination (5.5%), insect pollination (3.3%) and automatic autogamy were not significantly different, similar to the 2-week results. Insects appear to be important pollinators of 'Monthong' durian in areas where nectar bats visit infrequently. One bee species in particular, Apis dorsata, commonly foraged on flowers at dusk and appears to be the most effective insect pollinator of durian. Consequently, insect pollination could be an alternative method for durian farming. Preservation of forests and caves is suggested to maintain the nesting and foraging habitat of wild pollinators.