In 2014, Natural England withdrew permission to use non-native bumblebees in unscreened glasshouses due to concerns over the risk of local extinction of the British native sub-species Bombus terrestris audax (Bta) due to hybridisation.
Following the change, tomato growers began to express concerns about the pollination performance of the native bumblebee, Bta. To investigate these concerns, consultant Rob Jacobson conducted a survey with UK tomato growers (AHDB project PE 031).
Of the growers surveyed, 65% said they believe that Bta performed poorer than non-native species and suggested that they are more likely to fail to provide adequate pollination should any aspect of flower development or ambient conditions be suboptimal for their performance.
Reduced confidence in Bta has led to 75% of growers devoting more labour to monitoring fruit set, at additional cost to their businesses. One grower estimated that poor fruit set from poor pollination cost his business £50,000 per hectare in 2015.
Shorter-than-anticipated colony life of Bta could be resulting in gaps in the planned schedule. Some growers have increased their hive deliveries from fortnightly to weekly in an to attempt to reduce peaks and troughs in activity.
An important factor that may play a role in poorer pollination by Bta is the increase in smaller fruiting cultivars, which produce more flowers and are most affected by poor fruit set. In 2011, only 29% of UK tomato production was cherry/cocktail, but by 2016 it had increased to 77%.
In addition, one grower commented that pollen does not flow freely in humid conditions and speculated that Bta is unable to cope with this as well as non-native species. New research from AHDB hopes to build on this survey to address the issues raised.