AS WELL as having one of the few label recommendations for tuber blight, BASF's fungicide, Percos, also has the benefit of being from a unique class of chemistry.

Containing ametoctradin and dimethomorph, they are complex III inhibitors (pyrimidylamines) with a totally different mode of action to all other complex III inhibitors in the market.

Ametoctradin is a good partner for other actives, working with them to bring out the best in both when partnered propertly, said BASF.

It works by inhibiting mitochondrial respiration to provide effective protectant activity by preventing spore germination, plus a direct and indirect effect on zoospores, stopping them being released, or preventing movement for those already present.

Within this group of respiratory complex III inhibitors, there are a number of sub groups where the target site of activity has already been confirmed, for instance Qol inhibitors, or strobilurins (famoxadone and fenamidone) and Qil inhibitors (cyazofamid and amisulbrom).

Ametoctradin is different, classified as a QoSi inhibitor, binding to the stigmatellin subsite within the respiratory complex III. What is important is that ametoctradin is the first and only active ingredient in this classification that is not cross resistant with other fungicides," said Paul Goddard, a potato specialist for BASF.

He explained that Percos is one of the few approved fungicides with tuber blight reduction on its approval label. This indicated how important it is to include Percos in any blight prevention programme. Shirlan (fluazinam) also has a claim to protect against tuber blight on its label, but with the emergence of the fluazinam insensitive blight strain 37_A2 across the UK, its use needs to be given very careful thought," he argued.

Growers understand that they need to start their tuber blight programme as early as tuber initiation (within four weeks of emergence) as this is when the causal agent of tuber blight, motile zoospores, start forming on the leaf in sporangia. They fall down into the soil and can infect tubers via lenticels or wounds.

"Percos is a vital part of any programme due to its unique activity on tuber blight brought about by the active ametoctradin as well as its unique mode of action and no cross resistance to most other fungicides.

"The effect of ametoctradin on zoospore production and motility means it can be used any time from tuber initiation through to end of senescence. So we are advising growers to make the most of ametoctradin in any programme this season, he added.

Continue reading here:
Tuber blight: New class of chemistry helps in the fight - The Scottish Farmer