PE0 31a: Tomato: Phase 2 of an investigation into poor pollination performance by the native bumblebee, Bombus terrestris audax

Summary/Findings:

• In 2014, Natural England withdrew permission to use non-native bumblebees, Bombus terrestris terrestris (Btt), in unscreened glasshouses and tomato growers must now use the native sub-species, Bombus terrestris audax (Bta) to pollinate crops. As a consequence, many growers have suffered substantial financial losses due to poor fruit set (e.g. up to £50k per hectare reported).
• In 2017, the British Tomato Growers’ Association (TGA) conducted an AHDB-funded survey ([PE-031]) to determine the extent of the problem. The report highlighted several important areas for further investigation which triggered this study (Phase 2).
• Phase 2 investigated Bta colony activity in greenhouses and how environmental conditions, such as hive temperature, and pollen availability affect the foraging behaviour of Bta.
• The study found that of the 161 Bta colonies monitored across 12 production sites, 62% went into decline within 2 weeks of being placed in the tomato crop, increasing to 90% within 4 weeks. Manual recording showed that adult bees were active (exiting and entering the hive) over a 12 hour period with peak activity between 11:00 and 14:00 and the total activity (number of times bees exited and entered the hive) was considerably higher in hives kept outdoors compared to hives in greenhouses.
• The study also found that, although variable, peak pollen release occurred between 12:30 and 13:30 on average each day. High day temperatures (>29^◦C) inhibit pollen production and pollen release and may affect pollen viability.

Aim: To reduce financial losses resulting from production deficit, increased labour and excessive hive input caused by the enforced change to Bombus terrestris audax for pollination of UK tomato crops. 

Objectives: 

1. To investigate Bta biology and behaviour under different environmental conditions with particular emphasis on synchrony between bumblebee foraging and optimum pollen flow.
2. To investigate Bta colony life in commercial tomato crops and the impact this has on hive input schedules and frequency of hive deliveries.
3. To investigate the influence of environmental conditions on flower quality and pollen flow in the small fruiting cultivars which now make up 76.9% of UK production.
4. To transfer the results of these studies to the UK tomato industry.
5. To determine the need for further studies to satisfy the overall aim of the project.