Efficacy of Cover Crops for Pollinator Habitat Provision and Weed Suppression

Abstract

Pollinator declines have been documented globally, but little information is available about native bee ecology in Midwestern U.S. agriculture. This project seeks to optimize pollinator support and weed suppression in a 3-yr crop rotation with a fallow growing season. During fallow, one of five cover crop treatments (T1: crimson, red, and ladino clover and Bob oats [Fabales: Fabaceae - Trifolium incarnatum L., Trifolium pratense L., Trifolium repens L., and Cyperales: Poaceae - Avena sativa]; T2: crimson clover and oats; T3: red clover and oats; T4: ladino clover and oats; T5: no cover crop; T6/control: winter wheat [Cyperales: Poaceae - Triticum aestivum] L.) was seeded in one-half of 25 agricultural fields, whereas wheat was left unharvested in the other half as a comparison. Treatments that provide season-long floral resources support the greatest bee diversity and abundance (T1), and treatments with red clover support declining (Hymenoptera: Apidae) Bombus species (T1 and T3). Late-season floral resources may be important, yet limited (T1 and T4), and some species of agricultural weeds provide floral resources. Floral diversity may be less important than flower abundance or timing for pollinator diversity (T1–T4). Weed diversity was greatest in the no cover crop treatment (T5), least in winter wheat (T6), and intermediate in cover crop treatments (T1–T4) with no differences in weeds of economic concern. Wheat suppresses weeds but does not provide floral resources for pollinators. These results may also be applicable to marginal lands taken out of cultivation or field margin pollinator plantings in a typical corn–soybean rotation. Floral resource availability across the landscape is critical to maintain pollinator diversity.

Influence of flowering red clover on flower visitation in a sweet corn agroecosystem

“…Most studies evaluating pollinator attractiveness to cover crops have focused on single species annuals or a mixture of annuals with different flowering times so as to extend the blooming period (Carreck & Williams 2002;Mallinger et al 2019). Further, many of these studies evaluated floral visitor abundance in cover crops planted alone during the summer fallow period in lieu of interplanted within a cash crop (Bryan et al 2021). Red clover flowers provide bees with season-long access to pollen and nectar resources, including longtongued bees, many of which have experienced the greatest declines due to their specialized pollen requirements and the restricted availability of long-tubed flowers (Goulson et al 2005).…”

Climate change and managing insect pests and beneficials in agricultural systems

“…Intercropping or multiple cropping in which forbs are planted with cereals (e.g., legumes with wheat) increases pollinator diversity and abundance (Brandmeier et al., 2021; Kirsch et al., 2023; Norris et al., 2018). Flowering cover crops can also support pollinators, depending on crop species used in the cover crop mix (Bryan et al., 2021; Eberle et al., 2015; Mallinger et al., 2019). Cropping system diversification can offset the negative effects on pollinators resulting from agricultural intensification (Ellis & Barbercheck, 2015; Kovács‐Hostyánszki et al., 2017; O'Brien & Arathi, 2020).…”

“…This typically needs to occur at regional levels to ensure adequate habitat diversity is achieved (Garibaldi et al, 2021;Scherr et al, 2012;Tscharntke et al, 2021) posing challenges to policymakers (Steenwerth et al, 2014). crops can also support pollinators, depending on crop species used in the cover crop mix (Bryan et al, 2021;Eberle et al, 2015;Mallinger et al, 2019). Cropping system diversification can offset the negative effects on pollinators resulting from agricultural intensification (Ellis & Barbercheck, 2015;Kovács-Hostyánszki et al, 2017;O'Brien & Arathi, 2020).…”

Impacts of Wildflower Interventions on Beneficial Insects in Fruit Crops: A Review

“…Growers might also consider adding to floral mixes species that flower more consistently, e.g., clovers ( Trifolium hybridum, T. pratense, T. repens , L. corniculatus ), cornflower ( C. montana ), vetches (e.g., V. cracca, V. sativa ), and wild carrot ( D. carota ) [ 121 ]. Legumes are particularly important for bumblebees (but species with a shorter corolla can be selected to encourage shorter proboscis insects, e.g., hoverflies) [ 233 , 234 ], in addition to providing a source of nitrogen to orchards [ 235 ]. In addition, tall grasses are needed for overwintering bumblebees [ 205 ].…”