Optimization of pollination of greenhouse-grown tomatoes by bumblebees

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Bees play a critical role as pollinators of most fruit and vegetable crops. Greenhouse grown tomatoes require active pollen transfer, either through mechanical means or by foraging bees such as the domesticated bumblebee, Bombus terrestris. In greenhouses, tomatoes pollinated by bumblebees have larger fruit and greater yield per hectare than those pollinated mechanically. However, using bumblebees has some drawbacks. Growers are limited to use the UK native subspecies of the buff-tailed bumblebee, B. terrestris audax, to prevent the spread of disease to wild bumblebees. However, these colonies generally decline within 2-4 weeks of placement and exhibit relatively poor pollination rates on soft fruit and vegetable crops including commercially-valuable tomato varieties. The reasons for their poor performance are unknown. At the present, growers place colonies in glasshouses without any direct monitoring of the colonies. With the exception of counting bitemarks on flowers left by visiting bees, they also have no way to relate the behaviour of the bees to actual pollination rate and yield of tomatoes. Here, we propose to develop methods to monitor and improve the management of B.terrestris audax on UK grown tomatoes in collaboration with the UK's biggest glasshouse tomato grower, Thanet Earth (Kent) and sensor-based bee technology company, Bee-Ops.Our project has four main objectives: (1) To measure the pollination efficiency of bumblebee colonies in tomato crops in greenhouses (2) To identify how colony phase and nutritional state influence colony longevity and foraging rate of bumblebee colonies; (3) To improve the pollination of tomatoes by B. terrestris audax through in-colony exposure to floral chemical cues; (4) To create a strategy for improved colony management that optimizes pollination rate using data from Objs 1-3.In Obj 1, through collaboration with Bee-Ops, we will employ the latest AI and sensor technology to monitor the activity of B.terrestris audax colonies in commercial glasshouses at Thanet Earth. Sensor technology will enable us to provide the growers important data about the current state of pollination: a rating of the quality of the colonies received from their preferred suppliers and high resolution information about floral visitation and foraging rate of colonies for specific varieties and its influence on yields under particular conditions (e.g. time of year, temperature). In Obj 2, we will comprehensively test how the developmental phase of the colony introduced to the glasshouse influences foraging rate. Using an optimized pollen substitute for bumblebees developed by Wright and Stevenson's laboratories, we aim to improve colony longevity by studying how nutritional intervention early in colony development affects the colony's population size and foraging rate. In Obj 3, we will measure the volatile compounds emitted by tomato floral odours. Using methods developed in Stevenson's laboratory, we will train bees to learn to orient towards tomato floral scents by exposing bees in colonies to tomato floral scent in association with caffeinated nectar. These data will form the basis of a strategy devised in Obj 4 to show how specific interventions improve the pollination efficiency of bumblebees on specific tomato varietals. Together with our project partners, we will devise new strategies for optimal tomato pollination. We predict that the combination of methods we develop through this proposal will generalize to bumblebee pollination of other fruit and vegetable crops grown in greenhouses or polytunnels.