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Fight Against Blight update - September 2018

19 September 2018

By Dr David Cooke, James Hutton Institute

Having experienced one of the driest seasons since the Fight Against Blight began - clearly the weather has had a major impact. 

After some early appearances on discard piles in Kent in mid-April, we have received very few recorded outbreaks compared to previous years.

This has allowed us the time to genotype the samples as they arrived in the lab, and we now have genotype data for 24 positive outbreaks.

The data indicates a similar pattern to last year with the new lineages 37_A2 and 36_A2 in Kent and, more recently, in Shropshire.

There have been no findings of these genotypes beyond their 2017 range but the hot, dry weather will have been a major factor in limiting pathogen movement.

There are only two confirmed outbreaks from Lincolnshire, to date, so there remains a possibility that it is present but not yet sampled.

All sampled outbreaks from Wales, South West England and Lincolnshire have been of genotype 6_A1 (and in one case 13_A2).

As the weather begins to deteriorate the risk of late blight will increase and even low levels of inoculum can quickly amplify and generate high disease pressure in the absence of full fungicide protection. 

I think most advisors are recommending caution when using fluazinam or just dropping it from their tuber blight management programme. 

Any late foliar or stem disease obviously increases the risk of tuber infection before or during harvest and growers should be reminded of the importance of effective haulm kill to prevent blight spread.

Although the range of 37_A2 does not appear to have expanded I would stress that the sampling level is low and we cannot rule out its wider presence and emphasise the importance of late season blight management.

Advice on late blight management can be found here

You can see a recorded version of this update by clicking play below.

 

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