Supplemental Stingless Bee Pollination in Fennel (Foeniculum vulgare Mill.): An Assessment of Impacts on Native Pollinators and Crop Yield

Abstract

The yield of many crops benefits from pollinating insects; thus, recently reported declines in pollinator abundance and diversity are concerning for global food production. The pollinator dependency and amount of yield enhancement may vary according to crop species and geographical location. Fennel (Foeniculum vulgare) is an important spice crop cultivated in Indian states. However, comprehensive knowledge about pollination demand and yield enhancement potential of managed bees is still unknown. Here, we conducted a replicated study in two successive years (2020 and 2021) in West Bengal by combining pollinator surveys, pollinator-exclusion experiments, and field manipulation on fennel, which quantifies the impacts of supplemental stingless bees (Tetragonula iridipennis) pollination on native pollinators and crop yield. The crop species attracted many insect species belonging to diverse groups. Among those, important native pollinators (based on “approximate pollination value”) were Apis cerana, Apis dorsata, Apis florea, and Oxybelus furculatus in open condition (i.e., without field manipulation and in the absence of managed bees). We derived the coefficient of pollination deficit (D) from the fruit set percentages in open and manual cross-pollination treatments. The obtained value (D = 0.18) implies that the crop species have pollen transfer limitations, resulting in retardation of crop yield. From field manipulation with managed stingless bee colonies, the abundance of visitors (especially stingless bee foragers) on fennel increased (without altering the foraging activity of other native pollinators), thereby fruit set and crop yield increased by about 14.89 and 19.31%, respectively. Native managed stingless bees had no negative impacts on other native unmanaged species and can be promoted as complementary and short-term means of boosting yields and improving agricultural sustainability.

Spatial and Temporal Variations in Richness, Diversity and Abundance of Floral Visitors of Curry Plants (Bergera koenigii L.): Insights on Plant-Pollinator Interactions

“…We estimated the pollen-carrying value (PCV) of floral visitors according to the method of Layek et al [20] by summing two components: (i) PCV 1 (based on the average number of pollen grains attached to a visitor body surface, omitting stack pollen loads on abdomen, corbiculae, or scopae; value ranged from 0 to 5) and (ii) PCV 2 (based on the average number of pollen grains found in stack pollen loads on abdomen, corbiculae, or scopae; value ranged from 0 to 3). We entrapped the flower-visiting species with an insect collecting net to estimate the number of pollen grains carried by an insect species.…”

Floral biology, floral volatile organic compounds and floral visitors of Chromolaena odorata, an invasive alien species in West Bengal, India

“…To guess the importance of the floral visitors as pollinators of the plant species, we calculated an 'approximate pollination value (APV)' for each flowervisiting species (according to Layek et al 2022) as follows:…”

Intercropping with Pigeonpea (Cajanus cajan L. Millsp.): An Assessment of Its Influence on the Assemblage of Pollinators and Yield of Neighbouring Non-Leguminous Crops

“…Pollinator declines can result in the loss of pollination services, which significantly negatively impacts the maintenance of biological diversity, broader ecosystem stability, crop production, food security and human welfare. A reduction in pollinator service can directly influence reproductive output, decreasing the quantity and/or quality of fruit and seed sets [ 5 , 6 ]. Pollinator crisis also increases the selfing rate and thus causes an increase in inbreeding depression [ 7 , 8 ].…”