Nocturnal Pollination Services in Agroecosystems: A Case Study Examining Apple Horticulture in Norway

Abstract

The role of day active pollinators in agroecosystems has been broadly studied over the last 50 years. However, much less is known about the contributions of night active pollinators to overall agricultural and horticultural production yields. Apples are the most grown fruit crop in Norway, accounting for over 80% of total fruit production by weight. Insect pollination services greatly enhance both apple quantity and quality and are therefore crucially important for high yields of profitable fruit.

I explored how nocturnal insect pollinators contribute to apple production in Norway on two commercial apple farms in eastern Norway during the flowering season of 2023. Light traps were used to assess the diversity of the night-active insect pollinator community and apple flower-visiting insects were recorded by field cameras within orchards. In addition, a pollinator exclusion experiment was implemented to compare the independent contributions of nocturnal and diurnal pollinators to apple quantity (fruit set) and quality (seed set).

I found that the nocturnal pollinator community within my sites was limited both in terms of species richness and abundance. Only sixteen moths were captured in the light traps during the flowering season and the absence of moths in the camera images implies that they are most likely not important pollinators for apples in these sites. The moth community in my study area may have been affected by site-specific conditions such as light pollution, agricultural intensification, or pesticides.

Lacewings (Neuroptera) were frequently observed visiting apple flowers during the night and may be contributing to nocturnal pollination services. However, little is known about the role of lacewings in apple pollination and future studies should aim to test this insect group as potential providers of pollination services at night.

Nocturnal pollinators do not appear to play a substantial role in apple pollination in Eastern Norway, likely because of the limited nocturnal pollinator community present in the study area. However, exclusion of night active insects did result in pollination deficits (lower seed set), which suggests that nocturnal pollinators do have positive effects on apple production. Further research across various geographical regions is needed to increase our understanding of the contribution of nocturnal pollinators to agricultural and horticultural systems.