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Kim Patten, Rod Macfarlane, and Dan Mayer

The pollination of cranberries and pears by honey bees is often inadequate. The pollination efficacy of feral (Bombus spp.) and/or commercial bumble bees was evaluated for these crops. Preliminary evaluation of commercial B. vosnesenskii and B. occidentalis hives indicated poor forage activity on pears, but good activity on cranberries. Hive stocking densities of B. occidentalis on cranberries required to match feral Bombus populations was 8-10 hive/ha. Hives required 1-2 weeks in the field prior to full bloom to achieve suitable forage density during bloom. Parasitism of commercial hives by wax moth and bumble bee brood fly was common. Commercial colonies did not appear to be cost effective at this time. Only short-tongued feral Bombus species foraged on cranberries. Acceptance of artificial domiciles by these species was poor. Enhancing feral populations required provision of supplemental food sources and improved nesting habitat. Management of alternative food resources for feral bumble bees will be discussed.

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M.S. Stanghellini, J.T. Ambrose, and J.R. Schultheis

The effectiveness of bumble bees, Bombus impatiens Cresson, and honey bees, Apis mellifera L., on the pollination of cucumber, Cucumis sativus L., and watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai, was compared under field conditions. Comparisons were based on fruit abortion rates and seed set as influenced by bee type (honey bee or bumble bee) and the number of bee visits to treatment flowers (1, 6, 12, and 18 bee visits), plus two controls: a no-visit treatment and an open-pollinated (unrestricted visitation) treatment. For both crops, an increased number of bee visits had a strong positive effect on fruit and seed set. All cucumber and watermelon flowers bagged to prevent insect visitation aborted, demonstrating the need for active transfer of pollen between staminate and pistillate flowers. Bumble bee-visited flowers consistently had lower abortion rates and higher seed sets in the cucumber and watermelon studies than did honey bee-visited flowers when compared at the same bee visitation level. Only slight differences in fruit abortion rates were detected between bee types in the watermelon study. However, abortion rates for bumble bee-visited flowers were consistently less than those for honey bee-visited flowers when compared at equal bee visitation levels, with one exception at the 12 bee visit level. As the number of honey bee colonies continues to decline due to parasitic mite pests and based on the data obtained, we conclude that bumble bees have a great potential to serve as a supplemental pollinator for cucumbers, watermelons, and possibly other vine crops, when honey bees available for rental are in limited supply.

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Michael S. Stanghellini, John T. Ambrose, and Jonathan R. Schultheis

The effectiveness of bumble bees, Bombus impatiens, and honey bees, Apis mellifera, on the pollination of watermelon, Citrullus lanatus (Thunb.), was compared at the individual bee level. Correlations between the number of bee visits a flower received and the resultant seed set and fruit abortion rates were established. Using `Royal Jubilee' watermelon, B-impatiens-visited flowers resulted in higher seed sets than A. mellifera when compared at equal bee visit numbers. This difference between bee types was highly significant. With respect to fruit abortion rates, no statistical difference between bee types was detected. However, bee visit count was significant. Increasing the number of bee visits received by a flower resulted in a lower percentage of aborted fruit.

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Marvin P. Pritts, Robert W. Langhans, Thomas H. Whitlow, Mary Jo Kelly, and Aimee Roberts

Floricane-fruiting (summer-bearing) raspberries (Rubus idaeus L.) were grown outdoors in pots in upstate New York until mid-December when the chilling requirement was fulfilled. They were moved into a greenhouse and placed at a density that is three times higher than field planting. Bumble bees (Bombus impatiens Cresson) were introduced at flowering for pollination. Fruiting occurred from mid-February through mid-April, a time when the retail price for raspberries is between $3.00 and $6.00 for a half pint (180 g). Fruit quality was high, and individual 2-year-old plants averaged 11 half pints (2 kg) of marketable fruit. These yields and retail prices are equivalent to 19,000 lb and $142,000 per acre (21 t, $350,000 per ha). Raspberry production during winter allows growers to dramatically extend the harvest season and to produce a high-value crop at a time when greenhouses often are empty.

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M.S. Stanghellini, J.T. Ambrose, and J.R. Schultheis

The number of honey bees (Apis mellifera L.) continues to decline due to parasitic mite pests and other factors. Honey bees and bumble bees (Bombus impatiens Cresson) were therefore compared for their effects on the seed set of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] in a 2-year field experiment. The experiment was a 2 x 4 + 2 factorial, comparing bee type (honey bee or bumble bee) at four visitation levels (1, 6, 12, and 18 bee visits) to pistillate flowers, with two controls: a no-visit treatment and an open-pollinated treatment. Bee visitation level had a strong positive influence on seed set (P ≤ 0.0001). All flowers bagged to prevent insect visitation aborted, demonstrating the need for active pollen transfer between staminate and pistillate watermelon flowers. Flowers visited by B. impatiens consistently contained more seed than those visited by A. mellifera, when compared at equal bee visitation levels (P ≤ 0.0001). We conclude that bumble bees have great potential to serve as a supplemental pollinator for watermelon when honey bees available for rental are in limited supply.

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Melissa Broussard, Sujaya Rao, William P. Stephen, and Linda White

focused on the use of commercially available bee species: honeybees, managed bumble bees ( Bombus spp.; Cane and Schiffhauer, 2003 ; Evans and Spivak, 2006 ; Stubbs and Drummond, 1997 ), leafcutter bees ( Megachile spp; Cane et al., 1996 ; Cane and

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S. Alan Walters and Jonathan R. Schultheis

many different insect pollinators of cucurbits, honeybees and bumble bees are two of the most important for this group of vegetables ( Delaplane and Mayer, 2000 ; Free, 1993 ; McGregor, 1976 ). Honeybees and bumble bees are strongly directional in

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Patricio Brevis, Scott NeSmith, and Lynne Seymour

Poor fruit set is one of the most important horticultural problems of the rabbiteye blueberry industry. Rabbiteye blueberries require cross-pollination and several bee species are expected to transfer pollen from one cultivar to another. A novel method was developed to measure bee-mediated pollen dispersion in rabbiteye blueberry. Pollen diameters were used to predict the proportion of cross-pollen in bumble bees' pollen load. Bumble bees visiting blueberry flowers had low proportions of cross-pollen. It is proposed that inadequate levels of cross-pollination play a major role in the failure of rabbiteye blueberries to set adequate commercial crops. The composition of bees' pollen load changed with the phenology of the crop. Data indicate that the greatest likelihood for cross-pollination occurred around the time of maximum bloom overlap of the two studied cultivars.

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Laura C. Merrick, Frank Drummond, Constance Stubbs, and Rhonda Weber

Managed and feral honey bee (Apis mellifera) colonies have declined dramatically in the past decade due largely to parasitic mites, pesticide contamination, and severe weather. Squash (Cucurbita spp.) is one of many agricultural crops whose production may be negatively effected by decline of these pollinators. A study was conducted on a set of nine farms in Maine to assess the relationship between bee abundance and fruit set of summer and winter squash. The organic and conventional farms targeted in the study included farms with and without the presence of honey bees. With winter squash, fields with more bees tended to exhibit higher fruit set. The average fruit set was slightly higher for farms with honey bees (42%) vs. those without (35%), but both types of farms were similar to that found in controlled hand pollinations (31% on average). In contrast, fruit set for summer squash averaged 95% to 96% for all farms, regardless of the relative abundance of censused bees. Bumble bees (Bombus spp.) were the most abundant wild bees found pollinating squash. Farms with honey bees on average had higher numbers of bees in squash flowers than farms without honey bees, although a difference in preference for floral sex type was detected for bee taxa. Honey bees were much more likely to be found in female flowers, while bumble bees were more abundant in male flowers. Significantly more native bees were found in squash flowers on farms without honey bee hives, although native bees were still present to some extent on farms that were dominated by Apis mellifera.

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Todd P. West and Thomas W. McCutcheon

The objective of this study was to investigate the use of hornfaced bees (Osmia cornifrons Radoszkowski) as a successful sustainable alternative for pollination of commercial highbush blueberry (Vaccinium corymbosum L.). The hornfaced bee is native to Japan and introduced to the United States in 1977 by the USDA. Hornfaced bees have been shown to be 300× more efficient in pollinating apples than honey bees. Hornfaced bees are active for 4–6 weeks (April to June), and then the adults die. The rest of the year (10 months), dormant hornfaced bees exist inside nest cells located in cardboard straws stored away from berry production areas. Currently, there are no reports on hornfaced bee use available for blueberry farmers. Five pollinator treatments were compared in 2005 including: hornedfaced bees; honey bees; bumble bees; natural pollinators; and no pollinators. Enclosed pollination cages were constructed around mature field-grown highbush blueberry plants to prevent mixing of pollinator treatments. Each cage contained a single pollinator treatment except for the natural pollinator treatment. The five pollinator treatments were replicated three times inside separate netted cages on the farm. Three branches per plant were randomly selected that had a minimum of five fruiting buds and blossom number recorded. After pollination occurred the cages were removed to allow the berries to ripen. Ripe fruit were picked weekly over the season (July to August), with the fruit from each sample being counted and weighed. Blossom number was compared to fruit number and weight to determine efficiency of pollination as a result of the pollinator treatments. The results showed that hornfaced bees pollinated blueberries as well as or better than the other pollinators.