The blight fungicide Percos (ametoctradin and dimethomorph) from BASF offers two unique benefits to potato growers. Firstly ametoctradin (or Initium) is from a unique class of complex III inhibitors (pyrimidylamines) with a totally different mode of action to all other complex III inhibitors in the market.
Secondly, Initium has shown to be an excellent complementary partner for other actives; it helps bring out the best in both active substances when partnered.
Initium inhibits mitochondrial respiration to provide effective protectant activity by preventing spore germination. 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). Initium is different and is classified as a QoSi inhibitor, binding to the stigmatellin subsite within the respiratory complex III.
“What is important is that Initium 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.
Paul explains that more importantly Percos is one of the very few potato blight fungicides that has tuber blight reduction on its approved label.
“Very few blight fungicides have tuber blight on their label and 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 in the UK, its use needs to be given careful thought. You will only see fluazinam not working if you have used the active; for me it is not worth the risk on a crop worth several thousands of pounds per hectare.“
“When you take a close look at the labels of other blight fungicides, few are registered for tuber blight. On the label for Infinito (fluopicolide and propamocarb) from Bayer CropScience for example it says it will protect tubers from the risk of late blight infection after harvest and reduce tuber blight incidence when used as part of a full blight potato programe. Ranman Top (cyazofamid) from Belchim claims tuber blight protection, but warns about not relying on it in place of end of season products approved with specific claims for control of tuber blight. Electis (zoxamide and mancozeb) from Gowan has a useful effect as zoxamide works on zoospores in a different way to most other fungicides and so can be used to reduce the loading of zoospores early on. The new Zorvec Enicade from Corteva has been anxiously waited for but its label has no mention of tuber blight but positions it at rapid growth onwards.“ says Paul.
“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 casual agent of tuber blight, zoospores, can start to be formed. Percos needs to be 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 senescence. So we are advising growers to make the most of Initium this year.“