Leafcutter Bees (Hymenoptera: Megachilidae) as Pollinators of Pigeon Pea (Cajanus cajan (L.) Millsp., Fabaceae): Artificial Trap Nests as a strategy for their conservation

Abstract

Solitary bees of the family Megachilidae are the key pollinators of pigeon pea. Artificial trap nests were used to study nesting parameters, such as occupancy rate, nest establishment time, and building pattern during the vegetative and flowering stages of the Cajanus cajan (Fabaceae). The installed traps were occupied by three different leafcutter bees (Megachile lanata, M. laticeps, M. disjuncta) and one parasitic bee Coelioxys sp. Bees occupied the nest tubes for 16.01 ± 2.82 and 10.23 ± 2.30 days in the vegetative and flowering stages. We recorded 38.33 and 72.50% trap occupancy rates during crop vegetative and flowering stages, respectively. The percent parasitization by Melittobia sp was significantly higher during the vegetative stage (53.67%). Brood cells were parasitized by Coelioxys sp (6.67%) during the flowering stage. Many female bees tend to occupy trap nests with active nest construction during the flowering stage (7.21 ± 2.28 bees). In contrast, male bees merely took shelter inside the traps during the vegetative stage. Thus, it is concluded that female bees possess more wing wear during the vegetative stage of the crop when compared to the flowering stage. We also observed a significant increase in the percent pod set, the number of seeds per pod, and 100 seed weight in the experimental plot compared to the control plot, proving the importance of leafcutter bees for the pollination of Cajanus cajan crop. The present study results confirmed the role of artificial trap nests in providing habitats for the solitary leafcutter bees, thereby increasing their activity and nest abundance, which favors the pollination and better yield in pigeon pea.