Constance S. Stubbs

Bombus impatiens (Hymenoptera: Apidae): An Alternative to Apis mellifera (Hymenoptera: Apidae) for Lowbush Blueberry Pollination

Abstract The pollination effectiveness of the commercially reared bumble bee Bombus impatiens Cresson, was compared in field studies to the honey bee, Apis mellifera L., for lowbush blueberry, Vaccinium angustifolium Ait. A preliminary study indicated that B. impatiens had potential as an alternative pollinator. In a 3-yr study, percentage fruit set, percentage harvested berries, berry weight, and seeds per berry were compared in blueberry fields stocked at 7.5 A. mellifera hives per hectare to 5, 7.5, or 10 B. impatiens colonies per hectare. Percentage of harvested berries (yield) was significantly higher in fields stocked with B. impatiens at 10 colonies per hectare. No other parameters measuring pollinator effectiveness were significantly different at 5, 7.5, or 10 colonies per hectare. Flower handling time was significantly faster for B. impatiens and it more frequently collected blueberry pollen. All parameters of pollinator effectiveness were similar for B. impatiens, A. mellifera, and native wild bees in a follow-up study. Overall, B. impatiens was a suitable alternative to A. mellifera.

Sampling Native Wasps Along Both Vertical and Horizontal Gradients in the Maine Lowbush Blueberry Landscape

Abstract Native wasps were sampled from 33 lowbush blueberry (Vaccinium angustifolium) fields and adjacent forests in eastern Maine during the summers of 1997 and 1998. Sampling was conducted along a horizontal transect that bisected the field/forest interface using two methods: window-pane traps suspended at varying heights (1, 7, and 14 m above the ground) and ground-level malaise traps. The objectives of this study were to assess (1) the spatial distributions of wasp species assemblages associated with the two distinct habitats and (2) the potential interactions of wasp species assemblages across the blueberry/forest landscape. Wasp samples from the two trap types collected different wasp species assemblages, each of which were consistent across the 2 yr. Both methods documented lower abundances of wasps in blueberry fields in comparison with adjacent forests. Window pane traps at varying heights identified statistically significant but remarkably minor differences in height even at the highest traps in the middle of blueberry fields in both years of the study. The malaise traps detected distinct species assemblages whose horizontal distributions differed substantially from each other. Distributions ranged from those that were trapped exclusively in the forest, through those that were evenly distributed across the landscape, to taxa that were almost exclusively found in the blueberry field centers. Our results suggest that forest and edge habitats may be important refugia for wasp species assemblages that contribute to regulation of blueberry insect pest populations. Detailed knowledge of specific taxa should assist in the management of the blueberry/forest landscape for the conservation and enhancement of beneficial insects.

BEE CONSERVATION AND INCREASING OSMIA SPP. IN MAINE LOWBUSH BLUEBERRY FIELDS

Conservation of bees is of growing concern in many areas of the world due to their importance as pollinators. In northeastern North America at least eight species of Osmia (Megachilidae) pollinate Vaccinium angustifolium Ait, lowbush blueberry. Local populations of native wild bees in many Maine fields are presently below levels necessary to adequately pollinate the crop without reliance on rented honey bees. Nesting sites are an essential and often limiting resource for native bees. Since 1993 we have been investigating the effect of providing artificial nesting sites, wooden trap-nest blocks, on popula? tions. Visual estimates of Osmia spp. densities from m2 plot counts and sweep net samples during blueberry bloom indicate Osmia populations increased in two of the three fields that had trap-nest blocks provided. In contrast, popula? tions did not increase in the three fields where nesting blocks had been provided.

Dispersal of soredia by the oribatid mite, Humerobates arborea

Frequency of soredia acquisition and deposition by the oribatid mite, Humerobates arborea, was investigated. A survey of tree trunks in five unevenaged forests in central Maine revealed that 25% of...

Effect of a Botanical Acaricide on Ixodes scapularis (Acari: Ixodidae) and Nontarget Arthropods

ABSTRACT We tested the effectiveness of the rosemary oil-based insecticide, Eco-Exempt IC2, to control all stages of Ixodes scapularis (Say) in southern Maine. We selected plots in oak-pine forest where I. scapularis is endemic and recorded the abundance of ticks and nontarget arthropods before and after applications of IC2, bifenthrin (a synthetic pyrethroid), and water (reference treatment). Licensed applicators applied high-pressure spray treatments during the summer nymphal and fall adult seasonal peaks. Both acaricides sprayed during the summer nymphal season reduced nymphal I. scapularis/hour to zero. IC2 was as effective as bifenthrin in controlling nymphs through the rest of the nymphal season and also controlled adult ticks 9 mo postspray compared with 16 mo for bifenthrin, and both acaricides reduced larvae through 14 mo postspray. Both acaricides sprayed during the fall adult season reduced adult I. scapularis/hour to zero; IC2 controlled adult ticks 6 mo postspray compared with 1 yr for bifenthrin. Both fall-applied acaricides controlled nymphs 9 mo postspray and reduced larvae up to 10 mo postspray. Impacts on some nontarget arthropods was assessed. Colleoptera, Hymenoptera, and Collembola declined 1 wk postspray in acaricide-treated plots, and in IC2 plots all numbers rebounded by 20 d postspray. For bees and other flower-visiting insects there were no detectable reductions in nests produced, number emerged from nests, or number of foraging visits to flowering plants in IC2 or bifenthrin plots. IC2 was phytotoxic to the leafy portions of select understory plants that appeared to recover by the next growing season.

The relationships between Apocrita wasp populations and flowering plants in Maine's wild lowbush blueberry agroecosystems

Abstract This was the first study to have surveyed the spatial and temporal structure of Apocrita wasps in lowbush blueberry fields, a unique native agricultural landscape in Maine and eastern Canada. The relative abundances of wasps associated with lowbush blueberry (Vaccinium angustifolium Ait.) were investigated in 33 blueberry fields throughout Washington County, Maine, USA. Native wasps were captured during the springs and summers of 1997 and 1998 in Malaise traps erected along a transect in each field. Vegetation sampling was also conducted along these transects to quantify available floral resources. Data indicate the abundance of the total wasp community was positively associated with the abundance of sheep laurel (Kalmia angustifolia L.). Relationships between trap capture of 13 wasp morphospecies and other flowering weeds were also investigated. Most taxa in 1998 were positively associated with one or more of the following flowering plants: bunchberry (Cornus canadensis L.), bush honeysuckle (Diervilla lonicera P. Mill.), dogbane (Apocynum androsaemifolium L.), sheep laurel, and witherod (Viburnum nudum var. cassinoides L.). Similar results were not evident in 1997 because the method used to sample vegetation was not as extensive as that used in 1998. However, sheep laurel was positively associated with the wasp genera Microplitis spp. and Phanerotoma spp. during both years.

Stem and Leaf Diseases and Their Effects on Yield in Maine Lowbush Blueberry Fields

SUMMARY In 2001, six lowbush blueberry (Vaccinium angustifolium Ait.) fields in crop production were examined for the effects of stem and leaf diseases on yield. Symptomatic and control stems were tagged during bloom and the flowers per stem were counted. In late July, the berries were counted. Fungi commonly found on stems and leaves included Alternaria, Aureobasidium, Cladosporium, Colletotrichum, and Gloeo-sporium. For one field, stems with disease at their base showed a significant reduction in yield compared to healthy stems. Fungicides being evaluated for control of Monilinia blight had no significant effect on either stem disease or leaf spot incidence.

Bees of Maine, with a State Species Checklist

Abstract We present a new county checklist developed from bee research in Maine since the 1800s. The list contains 278 bee species in 37 genera and 6 families, of which all but 8 are native, with ≥50 taxa each in Andrena and Lasioglossum. Data for 16 counties from publications, museum collections, and recent surveys varied in number of species from 8 (Androscoggin) to 197 (Hancock). Research since 1930 on Vaccinium angustifolium (Lowbush Blueberry) led to many records. Twenty-one species are considered unusual, including 3 first recorded in 2016: Epeoloides pilosulus, Melitta melittoides, and Holcopasites calliopsidis. Maine records provide evidence of declines in Bombus affinis, decline in B. terricola followed by partial recovery, and increase in B. impatiens. Crops that should be studied regarding associated bees are Malus pumila (Apple), Vaccinium corymbosum (Highbush Blueberry), Vaccinium macrocarpon (American Cranberry), and Curcurbitaceae (cucurbits). Montane, sandy, and island habitats were identified as priorities for future sampling. We discuss records of bee species from New England relevant to understanding the Maine fauna, bee diversity, changes in abundance, cleptoparasitism, pesticide impacts, habitat requirements, and climate change.

A Natural History of Change in Native Bees Associated with Lowbush Blueberry in Maine

Abstract More than 120 native bee species have been documented in Maine since 1930 in association with the native plant Vaccinium angustifolium (Lowbush Blueberry). We report 3 studies in commercial Lowbush Blueberry fields: (1) a survey of diversity in Osmia (mason bees) and closely related Megachile (leaf-cutter bees) using trap nests in 93 fields from 1990 to 2012, (2) a 29-year study of a native bee community, and (3) an examination of climate-change effects on bee-foraging periods during blueberry bloom. Osmia appeared to be more stable over a 22- year period in their species richness and relative abundances in Lowbush Blueberry fields when compared to Megachile over a similar 17-year period. The native bee community in a single location in Winterport was observed to fluctuate in abundance 2 to 3 times annually. Modeling of the total bee community and taxa-specific group abundances (Bombus, Megachilids, Andrenids, and Halictids and other bees) suggest that while stochastic density-independent processes such as weather can play a role in determining their annual oscillations, density-dependent lags of 1 and 2 years appear to be the main driving forces. Estimation of fruit set over the same 29-year period, based upon native bee abundance, suggests that pollination is more buffered than community bee abundance, resulting in a lesser degree of fluctuation over time. We speculate that this finding is due to redundancy in floral preferences, multiple floral visitations, and differing pollination efficiencies by the highly diverse native bee community associated with Lowbush Blueberry. Effects of climate change in Maine Lowbush Blueberry fields during May bloom was investigated using a historic weather database. Since the early 1990s, precipitation has, to a large degree, reduced the number of optimal bee foraging days during bloom, with implications for pollination and bee species abundances. This new information reinforces the need for provision of pollinator gardens to support native pollinators of Lowbush Blueberry.