Aphids infesting lettuce fields in England are showing unexpected regional differences that could complicate pest management for one of the country’s key salad crops, according to new research.
The currant-lettuce aphid (Nasonovia ribisnigri) is a major pest of outdoor lettuces. A new analysis, using data from the Rothamsted-based National Insect Survey in collaboration with the University of Warwick’s Crop Centre, found that aphid populations are clearly divided between eastern and western England. Based on nearly two decades of genetic sampling, the results suggest that the pest’s movement is closely linked to lettuce-growing areas and may be more limited than previously assumed.
Examining insects collected from ten sites between 2003 and 2020, researchers discovered that while aphids tend to migrate eastward into major lettuce-producing regions, they rarely move westward. The team believes this pattern reflects the insect’s seasonal life cycle, alternating between its winter host — blackcurrant and related Ribes plants — and its summer host, lettuce, according to a press release.
The findings come at a crucial moment for UK lettuce growers. Traditional defences, such as pest-resistant lettuce varieties, have begun to lose effectiveness in recent years, leaving few reliable options for control. Yet, despite warmer temperatures and changing weather patterns that favour the pest, populations of N. ribisnigri have remained relatively stable.
Lead researcher Dr. Dion Garrett also found that the aphids are highly inbred and largely reproduce in seasonal cycles — traits that may contribute to their long-term persistence.
With the UK lettuce industry valued at hundreds of millions of pounds each year, the study underscores the urgent need to develop new, sustainable strategies for managing this resilient pest.
“The clear geographic divide we see has major implications for how we monitor and control N. ribisnigri,” said Garrett, warning that growers will need region-specific approaches to tackle the pest in future.
