- Fruits: berries (blueberries), berries (other)
- Animals: bees
- Education and Training: demonstration, on-farm/ranch research, workshop
- Pest Management: integrated pest management
- Production Systems: holistic management
- Soil Management: soil analysis
This project explored the effects of pest management program intensity and wildflower plantings on native bee communities present on highbush blueberry farms in western Michigan, with the goal of identifying best practices for managing pests and conserving beneficial insects on Great Lakes fruit farms. We revisited 15 blueberry farms sampled for bee community composition from 2004-2006 to assess the short- and long-term effects of insecticide program intensity on the bee community foraging on highbush blueberry during bloom. Prior-year insecticide program risk at the field scale had a significant negative effect on wild bee species richness, but not bee abundance or diversity. Intensive sampling of soil-nesting bees on four farms with wildflower plantings adjacent to blueberry fields determined that wildflower plantings support increased nesting by soil-nesting bees over grassy field margins and wooded habitats. We are currently developing printed and electronic educational materials on how to minimize risk to beneficial insects from pest management practices in Great Lakes specialty crops. We surveyed growers attending the 2013 and 2014 Great Lakes Fruit, Vegetable, and Farm Market EXPOs to assess rates of adoption of best practices for beneficial insect conservation.
An estimated 80% of wild plant species and 75% of the leading global food crops depend on animal pollinators, primarily bees (Klein et al. 2007). Declines in global wild bee abundance and richness, especially in intensively managed agricultural areas, may be threatening the provision of pollination services to wild and domesticated plant species (Kremen et al. 2002; Biesmeijer et al. 2006; Potts et al. 2010). Understanding the non-target effects of pest management programs on native bees and identifying management practices to conserve and restore these beneficial insects will be important for mitigating pollinator declines and maintaining stable and sufficient crop pollination services (Allen-Wardell et al., 1998; Garibaldi et al., 2011).
Highbush blueberry (Vaccinium corymbosum L.) requires insect pollination for economically viable yields (Isaacs and Kirk, 2010). While most Michigan blueberry growers rely on rented honey bee colonies for pollination, the steep declines in managed honey bee colonies across North America over the last 20 years have led to sharply rising rental prices and some hive shortages, underscoring the importance of identifying and supporting wild pollinators to ensure the resilience of pollination services and crop yields (Allen-Wardell et al., 1998; Winfree et al. 2007). Over 100 wild bee species have been recorded in Michigan blueberry fields during bloom, including ~10 species exhibiting high abundance and/or fidelity to Vaccinium flowers (Tuell et al., 2009). However, management of insect pests following bloom generally necessitates several insecticide applications per season. While short-lived bees that are tightly linked with blueberry bloom may not be affected by post-bloom insecticides, the sprays may have fitness consequences for bees with longer life cycles, including bumble bees (Bombus sp.), some of which are showing significant population declines in the eastern US (Colla and Packer, 2008; Grixti et al., 2009; Cameron et al., 2011; Bartomeus et al., 2013).
For the past ten years, blueberry production in Michigan has trended toward greater adoption of integrated pest management (IPM) strategies, including reductions in the quantity and toxicity of insecticides applied per season (NASS, 2001-2011). The use of broad-spectrum insecticides, such as azinphos-methyl, malathion, and carbaryl, declined strongly from 2001-2011, in favor of reduced-risk insecticides such as imidacloprid, acetamiprid and methoxyfenozide. However, the recent arrival of spotted-wing drosophila (Drosophila suzukii), an invasive pest that can cause serious economic damage to stone and small fruits (Lee et al. 2011), threatens the continued viability of IPM strategies in many fruit crops, including the region’s nation-leading blueberry and cherry crops. Additionally, these reduced-risk insecticides are generally not effective on D. suzukii (Van Timmeren and Isaacs, 2011). Estimates for Michigan indicate 2012 losses due to D. suzukii worth nearly $27 million. This invasive pest, with its short generation time, high dispersal ability, and lack of natural enemies, is likely to reverse trends toward adoption of reduced-risk insecticides. Since its discovery in 2010, Michigan blueberry growers have switched to prophylactic use of broad-spectrum insecticides applied on a calendar schedule to control this insect prior to harvest, a trend that may be highly deleterious to the bees active in and around crop fields after bloom. It will be essential to develop strategies for controlling D. suzukii and other blueberry pests that minimize risk to these wild bees.
One conservation practice that has been extensively studied in our lab over the past few years has been the establishment of native perennial wildflower plantings in blueberry field margins. These plantings can increase local bee and natural enemy abundance and richness, augmenting crop yields in adjacent blueberry fields through increased pollination services (Blaauw and Isaacs, 2014). However, it is not clear whether enhanced bee abundance and richness result from the addition of floral resources or from the provision of nesting habitat. For long-lived ground-nesting species like bumble bees (Bombus sp.), it may be both, as these species require floral resources to support their colonies after blueberries have finished blooming. However, for the species that exhibit tight linkage with the blueberry bloom period, when the wildflowers in the habitat planting have not yet begun blooming, nesting resources may be more important than available floral resources for the location of nest-site selection. Preferential nesting by ground-nesting bees in wildflower plantings would suggest that these restorations have the potential to function as source habitat for wild bees that forage on adjacent blueberry fields.
Over the past five years, several SARE projects have evaluated or encouraged farmer adoption of flowering conservation plantings to support pollinating insects and natural enemies in a variety of cropping systems (Surcica, 2009; Walton, 2009; Vaughan, 2010; Wilson, 2010; Blaauw and Isaacs, 2011; Blaauw, 2012; James, 2012). Others have investigated farm management practices or developed “best practice” guidelines to support native bees on-farm (Kuehn, 2009; Williams, 2009; Rao, 2011), as well as evaluated the contribution of the surrounding landscape context to the on-farm bee community (Alesch, 2012; Johnson and Sieving, 2012). Several projects have also evaluated methods to enhance nesting of Bombus and Osmia bees near crop fields (Bogash, 2009; Sidhu, 2011). This project complements previous work evaluating the use of conservation strips to enhance pollinator populations and the delivery of crop pollination services by investigating the mechanism by which these plantings support and enhance native bee populations. Similar to Sardinas (2012), who evaluated rates of nesting in sunflower fields adjacent to restored hedgerows, we assessed the soil-nesting bee community in established wildflower plantings and compared nest density within the plantings to the density of soil-nesting bees captured in the crop fields, adjacent wooded areas, and grassy field margins. Preferential nesting in the wildflower plantings would suggest that the plantings have the ability to enhance nest habitat for ground-nesting bees.
Our objectives were: 1) to assess how the intensity of insecticide applications affects the abundance, diversity, and richness of native bees foraging on highbush blueberry; 2) to determine the effects of wildflower plantings on soil-nesting bee communities; and 3) to develop educational resources on how to minimize the effects of pest management activities on beneficial insects.
Our audience is fruit growers – mainly blueberry, but also apple, cherry, pear, and grape producers – in western and northern Michigan. Our intermediate-term goals were to increase grower knowledge and awareness of the risks of insecticide use to beneficial insects, the benefits of using precision application equipment and IPM techniques to minimize drift and off-site movement, and the benefits of conservation plantings for maintaining abundant and diverse on-farm bee communities.
Our long-term goals included reducing the use of broad-spectrum insecticides during or near bloom, increasing adoption of bee-safe application practices (including the use of precision technology and evening/night application timing), and increasing the adoption of conservation plantings through the CRP-SAFE pollinator habitat restoration program. Adoption of practices that conserve wild bees, such as conservation plantings, can improve delivery of pollination services, increase farm profitability, and sustain and improve the environmental quality and natural resource base upon which these pollination-dependent crops depend.