Potato late blight fungicide Zorvec Enicade + Gachinko (oxathiapiprolin + amisulbrom) has shown good results in its first commercial season, although blight incidence has been lower than usual, due to the dry weather.
At a recent conference held by Corteva, which developed Zorvec, Dr Ruairidh Bain gave an update on potato late blight trials conducted this season (2018) at SRUC in Ayr, a coastal location in Scotland. Zorvec Enicade + Gachinko was compared with Infinito (fluopicolide + propamocarb) and an untreated control.
Dr Bain says: “For the trials we were lucky with the weather. Inoculation with 13_A2 was after the worst of the hot, dry weather. Higher than average temperatures at times meant very considerable sporulation early in the growing season and there were long periods of high relative humidity, and average rainfall.”
Zorvec plus Gachinko offered very good protection of new growth and its EuroBlight rating of two-and-a-half plusses was verified, says Dr Bain. “We observed consistently very good control of foliar blight by the commercial product Zorvec Enicade + Gachinko, under a more severe challenge than in 2017. Infinito at 7-day intervals was not as effective as Zorvec Enicade + Gachinko applied every 10 days. A Zorvec coformulation was as equally effective as the Gachinko tank mix.”
Although the trials had not concluded in early September, Dr Bain did not anticipate that advice on application of the product would change much. “It is to use during the rapid canopy development phase, at 10-day intervals, reducing to seven under high pressure conditions. An approval for up to four applications per crop allows for some additional use later on when disease pressure is high, but not as an eradicant.”
Following Zorvec’s first season of commercial use in the UK in 2018, Corteva field technical manager Craig Chisholm says in many parts of the UK blight incidence ‘hasn’t been the highest, but we’ve had some good learnings’.
“It was the hottest, driest summer in living memory and people went to longer intervals. There were fewer applications, 9-10 rather than 14 and greater reliance on protective chemistry. Where blight struck, results with Zorvec were impressive.”
Zorvec is a new mode of action said to be highly active across the blight life cycle, offering preventative and curative activity. It is anti-sporulant, controls stem blight, protects new growth and can be applied at 10-day intervals, which can help growers to manage labour resource at key times of demand, according to Mr Chisholm.
With growing concern about fungicide resistance, protecting new actives is important, agree scientists.
Dr Bain says: “The industry is now taking resistance management much more seriously. Fluazinam was classified by FRAC as low risk and therefore the development of resistance in the UK has worried a lot of people.”
Dr Huub Schepers of Wageningen University, The Netherlands, says the available evidence suggests that alternating with a fungicide that has a different mode of action does not alter selection for the high risk fungicide if the number of applications of the latter remains constant with, or without alternation.
“A vast majority of the evidence shows that adding a mixing partner to a high resistance fungicide reduces the selection for fungicide resistance.”
Concerning fungicide resistance management, Dr Ruairidh Bain adds: “Not all aspects of resistance management are a legal requirement but they are desirable. If we lose an active and it is not replaced, blight control becomes more difficult.”
Source: Corteva technical director Bernard Straebler