Science into practice: downy mildew control for baby leaf crops

Baby leaf crucifer crops, such as rocket grown at high densities, are particularly susceptible to downy mildew from emergence, especially the cotyledons and first true leaves.

Symptoms range from yellow blotches to small black speckles. Downy mildew is limiting production on some farms and entire crops continue to be lost. Almost all crops are at risk because the fungus requires only short periods of surface wetness to achieve infection.

HDC project FV 316 set out to compare varieties for susceptibility, investigate the role of seed treatments and find out whether crop covers influence the incidence of the disease.

For wild rocket, clear differences in resistance were found between the 26 varieties tested. The most resistant varieties decreased severity by more than 80 per cent compared with a susceptible standard. Nine salad rocket varieties were tested but no significant differences were found. Downy mildew was less severe than in wild rocket - symptoms were restricted to small spots.

Seed treatments were effective at protecting the crop for about three weeks. Downy mildew is able to overcome host resistance and fungicides so growers must be aware that there is a risk that there may be a breakdown of resistance if new races of downy mildew are selected.

Some types of crop covers caused increases in disease incidence and in crop vigour, compared with uncovered crops in 2008. In 2009, crop covers were used for 13 days from emergence. The Enviromesh, Ultrafine and Fleece covers provided an acceptable balance of features by reducing pest damage and increasing yield while slightly increasing downy mildew risk.

Horticultural Development Company

For details on all HDC activities, visit

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins

Sign up now
Already registered?
Sign in

Before commenting please read our rules for commenting on articles.

If you see a comment you find offensive, you can flag it as inappropriate. In the top right-hand corner of an individual comment, you will see 'flag as inappropriate'. Clicking this prompts us to review the comment. For further information see our rules for commenting on articles.

comments powered by Disqus

Read These Next

What challenges and opportunities lie in store for tomato growers?

What challenges and opportunities lie in store for tomato growers?

The British Tomato Growers Association (TGA) conference today (21 September) heard a range of perspectives on what changes lie in store for the sector and how to anticipate them.

Buoyant demand for UK apples but frost and labour remain concerns

Buoyant demand for UK apples but frost and labour remain concerns

As the British apple season begins, English Apples & Pears (EAP) is warning that growers will feel the effects of both a late frost in spring and also constrained labour supply.

Tomorrow's tractors

Tomorrow's tractors

These machines have advanced rapidly over recent years but what does the future hold? Sally Drury looks ahead.

Follow us on:
  • Facebook
  • LinkedIn
  • Twitter
  • Google +
Horticulture Jobs
More Horticulture Jobs

Pest & Disease Tracker bulletin 

The latest pest and disease alerts, how to treat them, plus EAMU updates, sent direct to your inbox.

Sign up here

Professor Geoffrey Dixon

GreenGene International chair Geoff Dixon on the business of fresh produce production

Read Professor Geoffrey Dixon