The blight fungicide Percos (ametoctradin and dimethomorph) from BASF is one of the few blight fungicides which has a label recommendation for reducing tuber blight. Percos also has the benefit of being from a unique class of chemistry. Ametoctradin is a complex III inhibitors (pyrimidylamines) with a totally different mode of action to all other complex III inhibitors in the market.
Ametoctradin is an excellent complementary partner for other actives; helping bring out the best in both active substances when partnered. It inhibits 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 eg Qol inhibitors or strobilurins (famoxadone and fenamidone) and Qil inhibitors (cyazofamid and amisulbrom).
Ametoctradin is different and is 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 and is not cross resistant with other fungicides,“ says Paul Goddard, potato specialist for BASF.
Mr Goddard explains that Percos is one of the few potato blight fungicides that has tuber blight reduction on its approved label. “This indicates 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.“
“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 programe this season,“ he says.