Following identification of Lettuce Fusarium wilt at two UK sites in autumn 2017, the disease has now been confirmed by laboratory diagnosis at two further sites in Lancashire, with a further case confirmed in Cambridgeshire this summer.
The disease has also been identified at a total of four sites in Ireland. All confirmed and suspect cases of the disease are from protected lettuce crops.
Lettuce Fusarium wilt caused by Fusarium oxysporum f. sp. lactucae (FOL) was confirmed as a new disease to the UK in October 2017, with all outbreaks to date on protected lettuce and caused by FOL race 4 (also present in the Netherlands, Belgium and Ireland). An AHDB Technical Review summarises current information on the disease and potential management strategies.
Lettuce FOL is primarily soil-borne so crop hygiene is essential to prevent spread of the fungus between lettuce crops, glasshouses, nurseries and plant propagators. Review crop hygiene procedures across your business (see hygiene information here), and where possible restrict access to cropping areas.
Prompt disease diagnosis is important to help minimise disease spread. Plants with suspect leaf symptoms should be cut in half from top to bottom to check for red/brown staining in the root which is characteristic of Fusarium wilt. Suspect samples can be sent to Warwick University to check for lettuce FOL - details below.
If the disease has been confirmed on-site, soil from affected beds should not be rotovated or spread to other areas of the nursery. Plant material should be uprooted and burned, or put in a covered skip for landfill. Do not bury the material in soil or add to discard piles or compost areas.
FOL survives in soil for several years, although levels of the pathogen decline over time in fallow soil. Consider leaving affected areas uncropped or plant a non-host crop, particularly during the summer when high temperatures are most conducive to disease development. For protected cropping, Basamid (dazomet) is approved for disinfestation of soil before planting (one application in every third year) and is known to have activity against lettuce FOL. Follow the label and read the manufacturers’ recommendations for most effective use of this product.
Trials under AHDB SCEPTREplus project are underway at University of Warwick to test the efficacy of conventional and biological products that could be used during propagation and cropping, or for soil disinfestation. New AHDB-funded work will commence this autumn to further investigate the biology of lettuce Fusarium wilt, including pathogen survival, infection thresholds, temperature range and disinfectant activity.
Samples can be posted for attention of: Andrew Taylor / Alison Jackson, Warwick Crop Centre, School of Life Sciences, University of Warwick, Wellesbourne Campus, Wellesbourne, Warwick. CV35 9EF