The challenges in managing potato blight have always been the main focus on in-season fungicide programmes for Scottish potato growers.
As a mobile and aggressive pathogen, it has readily adapted itself to new varieties over the years and we’ve been used to seeing it shift and slide. But in recent seasons the emergence of particularly worrying strains has been a feature and last season’s data confirms that the rise of three different issues in the new blight strains being commonly detected.
Firstly there are strains that are more aggressive (ie bigger and faster lesions), then there are strains that can overcome established varietal resistances and, finally, there are new strains which are harder to control and carry reduced sensitivity to fungicides.
This means that blight programmes for 2019 will require different approaches to previous seasons and the need to mix and alternate fungicides to make it harder for new strains to survive is much greater than previously.
The two strains of most concern to the industry are the so called 36_A2 strain which is highly aggressive and the 37_A2 strain, which has reduced sensitivity to fluazinam – both have increased frequency in population testing.
Other strains of great concern are the 13_A2 and 41_A2 strains, which are able to overcome many of the varietal resistance genes present in commercial potato varieties.