Drift retardant technology has now repeatedly been shown to give a valuable boost with Revus applications, particularly under high risk trials situations, reports Syngenta Technical Manager, Michael Tait.
Eurofins trials in Derbyshire last year, on irrigated crops that were inoculated with blight, and known to have the aggressive EU36_A2 genotype present, showed the addition of Crusade with Revus made the intrinsic activity of the mix the best on test for season-long control.
“It showed that Revus is inherently active on all blight genotypes present, including EU36_A2. Importantly, the research has also confirmed that, for the second season, the addition of a drift retardant maximised the level of blight control in the trial,” he reported.
Mandipropamid consistently performed as the most effective fungicide active against the spectrum of blight isolates in the trials. As a measure of the further reduction in the incidence of blight from the inclusion of Crusade with Revus, the area under a progression curve of disease infection was more than 15 percentage points lower at the end of the season, compared to Revus alone. Syngenta research into the use of drift retardants with Revus indicated that with Crusade more spray was held in the spray canopy, with fewer small droplets off target, which resulted in Revus being able to perform at its best.
Mr Tait added that whilst the trial had been inoculated with Pink 6_A1; Blue 13_A2 and Green 37_A2, subsequent analysis by James Hutton Institute showed that EU36_A2, which infected naturally, was the dominant late blight genotype in infected plots.
Furthermore, Mr Tait highlighted that the benefit of using Crusade as a drift retardant with Revus had been seen in field application trials using both standard Syngenta Potato Nozzles and 90% Drift Reduction Technology (DRT) nozzles which are in development.
“We have been really encouraged by the trial results using 90% DRT,” he said. “90% DRT nozzles offer significant practical advantages for operators applying blight sprays, especially to minimise the effects of wind gusts and assure even distribution of protection on leaves.
“Droplets from the DRT nozzles also appear to better penetrate into the crop canopy, to target lower leaves and stems,” he pointed out. The Eurofins trials used a farm sprayer to replicate field conditions as closely as possible.
Mr Tait cited Syngenta nozzle lab studies that had shown the addition of Crusade with Revus resulted in a more consistent droplet spectrum when applied through 90% DRT nozzles. Laser analysis revealed it reduced the number of both the largest coarse droplets and the finest drift susceptible droplets – to deliver a greater proportion in the optimum size droplets for controlled leaf targeting and retention.
“Blight control was maximised with the addition of Crusade with both standard Potato Nozzle and the 90% DRT nozzles, compared to Revus alone,” he advised. “The best result was application of the mix using a water volume of 200 l/ha.”
With blight infection at 82% in untreated plots by mid-August, applications of Revus with the Syngenta Potato Nozzle and 90% drift reduction nozzles had protected the adjacent plots at just 3% infection. Where Revus + Crusade had been used with the Potato Nozzle the infection rate was less than 1.5%, and just 0.75% with the mix using 90% DRT nozzles.
“Getting the best performance out of Revus will be essential for blight control this season, and maintaining efficacy for the future through good stewardship,” advocated Mr Tait. “Alternating fungicide modes of action in the programme and utilising Revus in mixture with other blight products is best practice to maintain the efficacy of all chemistry groups.”