Lettuce: biology and management of Fusarium wilt

Lettuce: biology and management of Fusarium wilt

Purpose / primary objective

AHDB wish to commission research to gain further insight into the biology and management of lettuce Fusarium wilt, with a focus on race 4 of Fusarium oxysporum f. sp. lactucae (FOL). Research outputs will be used to provide recommendations to growers on best-practice for disease avoidance and control.


The first UK outbreak of lettuce Fusarium wilt was confirmed in October 2017. The pathogen was identified as FOL Race 4. The disease is reported as a serious constraint to lettuce production in mainland Europe and race 4 of the pathogen has previously been identified in the Netherlands and Belgium. The UK leafy salads industry and plant propagators are extremely concerned about the potential impact of the disease on UK production, both under protection (soil and soilless systems) and outdoors, due to lack of effective control measures.


An AHDB-funded technical review completed in February 2018 summarised available information on biology and management of the disease. Options for disease control using fungicides, biofungicides and soil disinfestation treatments are being explored further under SCEPTREplus in 2018. The review also highlighted knowledge gaps regarding aspects of pathogen biology where further work is required to better inform best-practice for disease avoidance and control. Addressing these knowledge gaps on pathogen biology and hygiene measures forms the basis of this AHDB call for proposals. 

While lettuce FOL is not a notifiable disease, industry remain concerned about pathogen transmission to new sites within the UK due to the soil-borne nature of FOL. Potential contractors are advised to supply details of biosecurity and quarantine measures that would be implemented to minimise risk of pathogen spread from a research site, in particular for work that will involve soil infestation.

Specific objectives

Pathogen detection

Scope development of a FOL4 specific quantitative molecular test for soil and plant testing

While full development of a molecular diagnostic tool specific for lettuce FOL4 is likely to be outside the remit of this project, AHDB is willing to consider preliminary work within this proposal, particularly if it can be seen to provide a valuable research tool to use in objectives below on pathogen biology. Proposed work would need to indicate how constraints such as differentiation of live from dead DNA could be overcome.

Pathogen biology

Define the temperature range and level of inoculum required for infection and development of lettuce FOL race 4

Anecdotal data suggests that race 4 may thrive at lower temperatures than has been determined for other lettuce FOL races. This has implications for potential development of the disease in outdoor lettuce crops. Moreover, there is negligible information available on the minimum threshold of FOL 4 inoculum required for lettuce infection to occur under different temperatures. Studies are therefore required to define the temperature range and level of inoculum required for infection and development of lettuce FOL race 4.

Evaluate the impact of fallow and non-host cropping on lettuce FOL survival

There is evidence from preliminary studies to indicate that FOL race 4 can survive on non-host crops. A more detailed investigation is needed to determine the extent of colonisation of non-host rotation crops (relevant to the UK) by FOL race 4 and the impact of fallow cropping and non-host rotations on subsequent soil inoculum levels and severity of disease.

Hygiene measures

Evaluate disinfectant products for elimination of lettuce FOL from equipment, surfaces and trays

While disinfection activity can be inferred from work on other F. oxysporum f. spp., there is a need to confirm results against FOL4, in particular to include tests for activity against i) chlamydospores as well as mycelium and conidia, and ii) the pathogen in the presence of soil organic matter as well as the pathogen alone. In addition, the work should seek potential alternatives to quaternary ammonium compounds which can be effective against F. oxysporum but are considered unsuitable for use in lettuce production.

Development of best-practice methods for sterilising trays/crates for elimination of lettuce FOL

Different methods for sterilising trays/crates (e.g. heat, steam) warrant further investigation in terms of efficacy, practicality and cost.


The outputs listed below are considered a minimum; potential contractors are encouraged to outline other relevant knowledge exchange activities for industry. 

  • Final report to AHDB

  • Article for AHDB Grower magazine

  • Presentation at up to two relevant grower events

Project duration

1 year

Examples of relevant publications from AHDB

AHDB, 2018. Technical review on lettuce Fusarium wilt, caused by Fusarium oxysporum f. sp. lactucae

HDC, 2007. Final Report. PC 213 - Protected stock: aspects of the biology and control of Fusarium wilt, a new disease problem

Other reviews on lettuce Fusarium wilt

EPPO, 2013. Mini data sheet on Fusarium oxysporum f. sp. lactucae. Https://gd.eppo.int/taxon/FUSALC/documents

Defra, 2017. UK Risk Register Details for Fusarium oxysporum f. sp. lactucae. Https://secure.fera.defra.gov.uk/phiw/riskRegister/viewPestRisks.cfm?cslref=11558


Prospective contractors are encouraged to submit a joint proposal if complementary expertise has been identified. AHDB may, if it is deemed desirable, request applicants to form a project consortium.


The indicative budget is in the range £45-50 k excluding VAT

Completion and submission of the application form

Please refer to the guidance notes for completion of application forms. Applicants should complete the AHDB Research and KE Application Form - Full Proposal Small, completed forms must be emailed to research@ahdb.org.uk no later than 12.00 noon on 13 August 2018.

Proposed timings for application and project delivery

Stage of process


Call published

4 July 2018

Full proposal submission deadline

13th August 2018

Applicants informed of the outcome

20th August 2018

Anticipated start date

10th September 2018

Project duration

1 year (ending 30th September 2019)


If you have a specific question related to this call, please email research@ahdb.org.uk. As part of the open tender process, AHDB cannot discuss specific project details with you before submitting your proposal. View the Questions and Answers for this Research Call.

Assessment criteria

Please note that the assessment criteria have been slightly altered for this tender. Please click here to access the relevant assessment criteria.