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Richard G. Snyder

A successful greenhouse tomato crop depends on the optimization of several factors; among these factors are water, nutrition, and all facets of environmental control. Good pollination, however, is one of the most important requirements for the production of fruit of high yield and quality. Poor pollination causes fruit that are smaller, angular, or puffy, due to reduced seed numbers and poor gel fill in the locules. In Spring 1993, two 7.3 × 29.3 double plastic-covered greenhouses were used to compare the conventionally used electric pollinator to bumblebees for effective pollination; replicated variety trials were performed within each. In one greenhouse (12 replications, RCBD), `Trust' performed better than `Caruso' in yield and quality, although it was smaller in fruit size. In the other greenhouse (four replications, RCBD), `Match' and `Switch' were better than all others (`Belmondo', `Capello', `Laura', and `Rakata') for most yield and quality variables. Means across varieties were similar for the two pollination techniques, with marketable weights identical. For gutter-connected greenhouse ranges of 0.1 ha or larger, bumblebees are an economically viable option for pollinating hydroponically grown tomatoes.

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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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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 bumblebees, Bombus impatiens, and honeybees, Apis mellifera, on the pollination of cucumber, Cucumis sativus, was compared at the individual bee level. A correlation between the number of bee visits a flower received and the resultant seed set was established. In both cucumber varieties, `Calypso' and `Dasher II', B. impatiens-visited flowers consistently had higher seed sets than A. mellifera when compared at equal visit numbers. This difference between bee types was found to be highly significant.

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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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Susan M. Stieve* and David Tay

Seeds of herbaceous ornamental accessions conserved by the USDA National Plant Germplasm System (NPGS) are traditionally produced in summer field cages with honey bees (Apis mellifera) when pollinators are required. Efficient methods to produce high-quality seed in greenhouses may allow for year-round seed production. Flower quantities and effects of pollinators on number and weight of seed produced were studied in field cages and greenhouses at the Ornamental Plant Germplasm Center in 2003 in a randomized complete-block experiment. Honey bees, bumblebees (Bombus impatiens), or blue bottle flies (Diptera calliphoridae) were used as pollinators. Field cages and greenhouse compartments with no pollinator were controls. Cultivars used were Antirrhinum majus `Gum Drop', Coreopsis tinctoria `Plains Bicolor', Dianthus chinensis `Carnation' (NPGS accession NSL 15527), Rudbeckia hirta `Indian Summer', and Tagetes patula `Jaguar'. Seeds were harvested, cleaned, weighed, and 100-seed weights calculated. On average Antirrhinum, Dianthus, Rudbeckia and Tagetes produced more flowers in greenhouses, Coreopsis produced more flowers in the field. Coreopsis and Rudbeckia produced more seed per flower on average with field pollination by honey bees, Antirrhinum and Dianthus produced most with bumblebees in the field, and Tagetes produced most with blue bottle flies in the greenhouse. Each genus had similar 100-seed weights on average in all treatments. Results show pollinators other than honey bees are useful for herbaceous ornamental seed production and that seed production in greenhouses may be an alternative method for seed production of herbaceous ornamentals.

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

Very little is known about the rate at which pollen grains are mobilized within insect-pollinated crop systems, and this is especially true the for commercial production of field-grown cucumber (Cucumis sativus L.), monoecious muskmelon (Cucumis melo L.), and triploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. The rates of pollen depletion for these crops were therefore investigated on plots simulating commercial crop production using a mixed honey bee (Apis mellifera L.) and bumble bee (Bombus impatiens Cresson) pollinator complex. At anthesis, staminate cucumber, muskmelon, and watermelon flowers contained on average 10539, 11176, and 30739 pollen grains/flower, respectively. At the time flowers closed in the early afternoon (1300 to 1400 hr), only 61% of the total pollen produced had been removed from staminate cucumber flowers, 44% to 62% from muskmelon, and 81% from watermelon flowers. The results suggest that total pollen production in these crops may not necessarily reflect total pollen availability to floral visitors (bees). However, of the total amount of pollen actually removed per flower, >57% occurred during the 2 h following flower anthesis of cucumber and muskmelon, and >77% occurred during the 2 h following flower anthesis of watermelon. Thus, most of the accessible pollen was removed shortly after anthesis, which is when these crops are most receptive to pollination. Nonviable triploid and viable diploid watermelon pollen were removed at similar rates (P = 0.4604). While correlation analyses were not possible for the influence of variable bee abundance on pollen depletion rates, higher bee populations in one year appeared to increase the rate at which pollen grains were removed from staminate flowers.

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Stephen J. Stringer, Donna A. Marshall, and Dennis J. Gray

). Average berry weight was 10.3 g less than ‘Black Beauty’ (14.6 g) but larger than most other cultivars, including other pistillate varieties. As a result of fruit heavy damage resulting from nectar scavenging by bumble bees ( Bombus impatiens ), it was

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Dennis J. Werner and Layne K. Snelling

cultivars in a screen cage and introducing a small hive of bumblebees [( Bombus impatiens Cresson), Koppert Biological Systems, Inc., Romulus, MI]. Preliminary research in our program provided strong evidence that eastern redbud is self