Wildflower Plantings Do Not Compete With Neighboring Almond Orchards for Pollinator Visits

Abstract

The engineering of flowering agricultural field borders has emerged as a research and policy priority to mitigate threats to pollinators. Studies have, however, rarely addressed the potential that flowering field borders might compete with neighboring crops for pollinator visits if they both are in bloom at the same time, despite this being a concern expressed by growers. We evaluated how wildflower plantings added to orchard borders in a large (512 ha) commercial almond orchard affected honey bee and wild bee visitation to orchard borders and the crop. The study was conducted over two consecutive seasons using three large (0.48 ha) wildflower plantings paired with control orchard borders in a highly simplified agricultural landscape in California. Honey bee (Apis mellifera L.) and wild bee visitation to wildflower plots were at least an order of magnitude higher than to control plots, but increased honey bee visitation to wildflower plots did not lead to any detectable shifts in honey bee visitation to almond flowers in the neighboring orchard. Wild bees were rarely observed visiting almond flowers irrespective of border treatment, indicating a limited short-term potential for augmenting crop pollination using wild bees in highly simplified agricultural landscapes. Although further studies are warranted on bee visitation and crop yield from spatially independent orchards, this study indicates that growers can support bees with alternative forage in almond orchards without risking competition between the wildflower plantings and the crop.

Limited phenological and dietary overlap between bee communities in spring flowering crops and herbaceous enhancements

“…Much of the focus on reversing losses of wild bee populations that have occurred as a result of agricultural intensification has concentrated on herbaceous plantings, in part due to the substantial declines of flowerrich agricultural grasslands in Europe (Carvell et al 2006) and the loss of prairie habitats in North America (Samson andKnopf 1994, Ramankutty andFoley 1999). The focus on herbaceous plant communities that flower outside of crop bloom is also partly driven by grower concerns that creating patches that flower during crop bloom will reduce the number of bees visiting their crop, though empirical evidence for this is mixed, with a negative impact seen in the tropics (Peters et al 2012) and no effect was seen in temperate areas (Lundin et al 2017).…”

Pre-almond supplemental forage improves colony survival and alters queen pheromone signaling in overwintering honey bee colonies

“…Cultivated landscapes with limited forage alternatives have been linked to reductions in honey bee nutrition, colony performance, and colony survival (Alaux et al 2017;Dolezal et al 2016;Requier et al 2015;Smart et al 2016). SF is one of several management approaches used to increase floral nutrients during times of nutritional stress (Decourtye et al 2010;DeGrandi-Hoffman et al 2016;Lundin et al 2017). Our study shows that modest plantings of mid-winter SF at high colony densities (50 colonies/ha forage) can improve colony survivorship during almond pollination.…”

“…Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13592-018-0607-x) contains supplementary material, which is available to authorized users. DeGrandi-Hoffman et al 2016;Lundin et al 2017). Three approaches for overwintering colonies have been suggested: (1) fall SF during winter bee production, (2) mid-winter SF before the first spring forage, and (3) SF during the first spring forage (Decourtye et al 2010;DeGrandi-Hoffman et al 2016;Alaux et al 2017).…”

“…The second approach is well suited to colonies used for California almond pollination. The limited forage available in winter around orchards is often insufficient to support the more than 1.7 million colonies used in almond pollination (Simone-Finstrom et al 2016;Lundin et al 2017). However, almond-bound colonies are often pre-staged in locations capable of supporting winter-blooming plants.…”

Annual flower strips support pollinators and potentially enhance red clover seed yield

“…For instance, flower visiting insects can be pulled away from a natural habitat by adjacent mass-flowering crops, negatively affecting wild plant pollination (Holzschuh, Dormann, Tscharntke, & Steffan-Dewenter, 2011). Less is understood on how organisms flow between crops (but see Bommarco & Fagan, 2002;Riedinger, Renner, Rundlöf, Steffan-Dewenter, & Holzschuh, 2014) and other managed habitats such as flower strips, and whether adding a highly attractive resource adjacent to the crop risks pulling away service-providing species from the target crop (but see Lundin et al, 2017).…”