Onions: Investigation into the control of White Rot in bulb and salad onion crops

Summary: Allium white rot, caused by Sclerotium cepivorum, can cause severe crop losses in UK bulb and salad onion crops.  S. cepivorum resting bodies (sclerotia), which can survive 20 years, have built-up in fields due to intensive repeat cropping, particularly in many of the fen and silt soils most suitable for Allium crops. 

Considerable research effort has been expended worldwide to increase understanding of Allium white rot disease and its control, particularly by soil treatments, and this was critically reviewed in FV 449.  This included a review of the epidemiology of S. cepivorum, the efficacy of physical, chemical or biological pre and post-planting treatments, plus the practicality and cost of different disease management options. Options developed for other soilborne plant pathogens will also be examined.

Following discussion of the review results with BOPA and AHDB a research project to investigate the most promising, practical and economic treatments appropriate to UK onion growers has been funded in FV 449a.  In this study researchers have evaluated a range of management options in glasshouse, pot experiments and field trials as appropriate over two cropping years. Integrated strategies for communication to growers will be identified and developed to facilitate the sustainable production of onion crops, aiming to work towards effective and long-term management of the disease.

Added value was gained in the main project by testing some of the soil treatments on the same crops to investigate possible options for management of Fusarium oxysporum f.sp. cepae

Project Dates:

FV 449 - 01.04.2016 - 30.09.2016

FV 449a - 01.03.2018 - 28.2.2022

FV 449

Aim:

To develop an integrated crop management strategy for sustainable control of Allium white rot in bulb and salad onions.

Objectives

1. To critically review recent worldwide research on Allium white rot and its control;
   2. To identify from the review the most feasible and promising control treatments for management of Allium white rot in the UK and their cost of application;
   3. To determine the efficacy of selected disease management treatments in controlling Allium white rot in pot trials and in the field, alone and in combination;
   4. To propose an integrated crop management strategy for Allium white rot based on the literature review and project results;
   5. To communicate results to growers through reports, a factsheet, articles in AHDB Grower and growers meetings.
   The work will cover both conventionally and organically grown bulb and salad onion crops as appropriate.

FV 449a

Aim:

To reduce crop losses to Allium white rot in salad and bulb onions, whilst helping to avoid loss of growing areas where the risk of infection is too high using integrated strategies that could reduce reliance on pesticides.

Objectives

1. Test fungicides and biological control agents for their effect on Allium white rot disease and generate preliminary data on effect of selected products on Fusarium basal rot
2. Test Allium products for their effect on germination of S. cepivorum sclerotia
3. Test biofumigants for their ability to reduce viability of S. cepivorum sclerotia and reduce Fusarium inoculum
4. Test combined treatments for their effect on Allium white rot disease development
5. Communicate white rot information and results through reports, presentations, a workshop and a factsheet