Nikki Rothwell

Evaluation of dodine, fluopyram and penthiopyrad for the management of leaf spot and powdery mildew of tart cherry, and fungicide sensitivity screening of Michigan populations of Blumeriella jaapii

BACKGROUND Field trials were conducted on the tart cherry cultivar Montmorency to evaluate the efficacy of dodine and the succinate dehydrogenase inhibitor (SDHI) fungicides fluopyram and penthiopyrad for control of cherry leaf spot (CLS) and powdery mildew (PM). The in vitro sensitivity of Blumeriella jaapii (CLS) to the same fungicides was also tested. RESULTS Treatments with dodine or fluopyram were among the most effective for controlling CLS, while fluopyram or penthiopyrad treatments were among the most effective for controlling PM. In vitro studies detected a wide range of minimum inhibitory concentrations (MICs) among the isolates (0.05-400 µg AI mL(-1) ) in response to dodine. Orchard isolates showed reduced sensitivity to dodine as compared with baseline isolates. B. jaapii was more sensitive to fluopyram (0.01-10.0 µg AI mL(-1) ) than to penthiopyrad (0.01-25 µg AI mL(-1) ), and orchard isolates also showed a shift towards reduced sensitivity. CONCLUSION The results indicate that dodine remains effective in CLS control. In addition, as penthiopyrad and fluopyram become available to growers, this research establishes baseline information that will be important for future monitoring and analysis of B. jaapii population responses to exposure to dodine and these SDHI fungicides.

Does Passive Sampling Accurately Reflect the Bee (Apoidea: Anthophila) Communities Pollinating Apple and Sour Cherry Orchards?

Abstract During bloom of spring orchard crops, bees are the primary providers of pollination service. Monitoring these insects for research projects is often done by timed observations or by direct aerial netting, but there has been increasing interest in blue vane traps as an efficient passive approach to collecting bees. Over multiple spring seasons in Michigan and Pennsylvania, orchards were monitored for wild bees using timed netting from crop flowers and blue vane traps. This revealed a distinctly different community of wild bees captured using the two methods, suggesting that blue vane traps can complement but cannot replace direct aerial netting. The bee community in blue vane traps was generally composed of nonpollinating species, which can be of interest for broader biodiversity studies. In particular, blue vane traps caught Eucera atriventris (Smith), Eucera hamata (Bradley), Bombus fervidus (F.), and Agapostemon virescens (F.) that were never collected from the orchard crop flowers during the study period. Captures of bee species in nets was generally stable across the 3 yr, whereas we observed significant declines in the abundance of Lasioglossum pilosum (Smith) and Eucera spp. trapped using blue vane traps during the project, suggesting local overtrapping of reproductive individuals. We conclude that blue vane traps are a useful tool for expanding insights into bee communities within orchard crop systems, but they should be used with great caution to avoid local extirpation of these important insects.

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

Wild bee populations have undergone declines in recent years across much of the Western world, and these declines have the potential to limit yield in pollination-dependent crops. Highbush blueberry, Vaccinium corymbosum, and tart cherry, Prunus cerasus, are spring-blooming crops that rely on the movement of pollen by bees and other insects for pollination. Wild bee populations can be increased on farmland by providing floral resources, but whether the addition of these plants translates into increased pollinator density on crop flowers has not been documented in most cropping systems. To determine the importance of providing additional floral resources for wild bee pollinator communities, we selected blueberry fields and tart cherry orchards with and without herbaceous floral enhancements in western Michigan, USA. The bee communities visiting crop flowers, enhancements and control grassy field margins were sampled over a 5-yr period. In addition, the pollen diets of the most abundant wild bee crop pollinators were quantified across Michigan to better understand their foraging niches and to identify potentially important alternative host plants. The presence of floral enhancements did not increase the abundance of wild bees on either blueberry or cherry flowers during bloom. The bee community visiting blueberry was evenly composed of short-season bees that fly only during the spring and long-season bees that fly in both spring and summer. In contrast, the bee community visiting cherry was dominated by short-season spring bees. The majority of pollen collected by the wild bee communities visiting blueberry and cherry was from spring-flowering woody plants, with limited use of the herbaceous enhancements. Enhancements attracted greater abundance and species richness of bees compared to control areas, including twice as many floral specialists. Conserving summer-flying, grassland-associated bees is an appropriate goal for pollinator conservation programs. However, herbaceous enhancements may not provide adequate resources for the wild bees that pollinate spring-flowering crops. This study demonstrates that an examination of the pollen collected by wild bees across their flight periods can identify plant species to help them persist in intensively managed landscapes.