Influence Of Flower Strips On Insect Pollinator Recruitment And Crop Yield In Day-Neutral Strawberry Production

Abstract

Around 35% of our food comes from pollinator-dependent crops, especially many fruit crops. In light of emerging threats to the honey bee industry, recent research has highlighted the importance of wild insect pollination services in agroecosystems. Pollinator “farmscaping” practices, which provide habitat and floral resources for wild insect pollinators on farms over space and time, are being investigated for horticultural crops. However, there is relatively little research directly linking pollinator farmscaping practices to crop yields, especially considering the wide variation in pollination requirements between crop species. Strawberries (Fragaria x ananassa), though self-fertile, appear to produce higher quality fruit when flowers are more thoroughly fertilized by pollinating insects. Ensuring effective pollination services for strawberry crops may be even more beneficial in day-neutral cultivars, which flower and fruit continuously throughout the growing season, as opposed to the short-day (June-bearing) cultivars commonly grown in the US Midwest. While some research has shown increased pollinator abundance in strawberry fields adjacent to annual wildflower strips, there is less research on direct benefits to strawberry production, particularly for day-neutral strawberries. In addition, most flower strip research focuses on diverse wildflower strips, despite evidence that bees may benefit more from flower plantings with clumps of single species rather than heterogeneous mixtures. This research investigates the potential of planting an attractive annual flower strip as a “magnet species” to recruit wild pollinators and enhance pollination services, and therefore yield, in an organic day-neutral strawberry production system over two growing seasons. Flowering borage (Borago officinalis) strips were established on one end of three experimental fields of day-neutral strawberries. Strawberry yield and pollinator presence were hypothesized to decrease with distance from the flower strip. Though distance from the flower strip did not have a statistically significant impact on production parameters and pollinator presence, average strawberry yield and berry number was lowest in plots furthest from the flower strip in both years. Individual berry weights of the ‘Evie-2’ cultivar decline with distance from the flower strip, perhaps due to high pollination requirements. Strawberry floral visitor abundance declines steadily with distance from the flower strip in 2017, but this pattern is not clearly observed in 2018. The borage flower strip was highly attractive to insects, though primarily honey bees (Apis mellifera) and bumble bees (Bombus spp.). Primary strawberry flower visitors were hoverflies (Syrphidae), root maggot flies (Anthomyiidae) and native bees (Halictidae, Megachilidae, etc.), suggesting day-neutral strawberry pollination may rely more on Diptera taxa and small bees rather than larger pollinators like honey bees or bumble bees. More research is necessary to examine the potential of borage as a “magnet species” to facilitate day-neutral strawberry crop pollination. This project presents further evidence on the potential of pollinator farmscaping practices, such as annual flower strips, to recruit wild insect pollinators and improve pollination services for the benefit of small fruit crops.