Aphid Divide: New Research Reveals England’s Lettuce Fields Are Under Uneven Attack

Aphids attacking lettuce fields in England are showing distinct regional patterns that could redefine how growers manage one of the nation’s key salad crops, according to new research.

The currant-lettuce aphid (Nasonovia ribisnigri)—a long-standing scourge of outdoor lettuce production—has been found to divide its populations between the east and west of England. The finding comes from a comprehensive analysis using data from the Rothamsted National Insect Survey and the University of Warwick Crop Centre, spanning nearly two decades of genetic sampling.

Researchers discovered that these aphids migrate from western regions into eastern lettuce fields, but rarely in the reverse direction. The team attributes this to the insect’s dependence on blackcurrant and other Ribes plants as winter hosts, while lettuce remains its preferred summer home.

The results, drawn from samples collected at ten monitoring sites between 2003 and 2020, challenge previous assumptions that N. ribisnigri populations were freely mixing across the country. Instead, the research suggests a more localised pattern of spread, strongly influenced by the geography of lettuce production.

Traditional defences—particularly resistant lettuce varieties—have lost their edge in recent years, narrowing growers’ options for control. Yet, despite warmer temperatures and more variable weather, aphid populations have remained remarkably stable.

Dr Dion Garrett, who led the study, said the findings could have significant implications for future pest management. “The clear geographic divide we see has major implications for how we monitor and control N. ribisnigri,” he explained. “These insects are highly inbred and reproduce in seasonal cycles, which may help explain their persistence. The next step is to design region-specific strategies that target populations where they’re strongest.”

With lettuce representing a cornerstone of the UK fresh produce sector, the study highlights the growing need for localised, adaptive pest management systems—ones that take regional movement patterns into account to safeguard future salad supplies.

Read the analysis here.