BRASSICA crop growers are being urged to make use of a new rapid test for the main clubroot pathogen in their soils.

Costing about £100 and with a two-week turnaround, the rapid molecular test offered by PGRO for the detection and quantification of the clubroot pathogen, plasmodiophora brassicae, in the soil can be used as a 'risk assessment' tool for ingoing crops and rotation management.

Roger Vickers, PGRO’s chief executive said: “The test is proving invaluable to close rotation intensive vegetable producers as well as to growers of oilseed rape – which is the most commonly grown brassica crop in the UK.

“Clubroot infection can cause significant, or even complete, crop losses when infection is severe and is exacerbated by close rotations. The pathogen responsible can persist in soils for at least 15 years, so cannot be managed practically by extending rotations.

“Varietal resistance remains the most effective method of clubroot control. However, the resistance source is not effective against all pathotypes and resistance breaking strains have become more prevalent."

Dr Lea Herold, PGRO's plant pathologist, said that the test, which was launched last summer, determined the number of pathogen resting spores per gram of soil. “These spores germinate in the presence of host plants, leading to infection if surrounding conditions are favourable for disease development.

"The higher the numbers of spores per gram of soil, the higher the risk of disease development. Growers receive a risk indicator for their soil, with the level of risk defined on a 1-3 scale (slight, moderate or severe) according to infection levels identified as set out by the AHDB Horticulture Project."

To use the test, growers should send a soil sample in a sealed plastic bag marked ‘Brassica clubroot test’ to PGRO Lab, Great North Road, Thornhaugh, Peterborough, Cambridgeshire PE8 6HJ.

The sample should be 1kg of soil sampled from 5cm-25cm depth of soil and representative of whole field and be sent with full field reference and grower contact details.

Sampling strategy:

* If a specific issue is occurring in a restricted area then samples might be collected from that area alone.

* If an entire site is to be assessed then a sample representative of the entire site should be collated.

* Soil should be taken from the rhizosphere (the root zone). This means discarding the top 5cm of soil and sampling to a depth of 25cm.

* A random or grid sampling strategy should be adopted using a sampling auger, trowel or spade, but remember sample contamination can occur if equipment is not cleaned thoroughly between sites.