New blight fungicide shows strong protection

Cambridgeshire potato growers had the first opportunity to see the performance of a new Syngenta blight fungicide, mandipropamid, at the company's Whittlesford trials site last week (24th August). The pre-registration trials, inoculated with blight and heavily irrigated to create incredibly high disease pressure, have seen the new chemistry provide very high levels of blight control compared to current industry standards.

Syngenta Potato Manager, Alison Pawson, reports straight mandipropamid, applied at the full proposed rate every seven to 10 days since plants met down the rows, has held blight infection down to just 3% of the leaf area. Mandipropamid applied in conjunction with Shirlan is performing the best of all treatments - with 2% infection assessed this week. Foliage on untreated plots has been wiped out by disease, with widespread stem lesions developing.

"The performance of mandipropamid, in the face of such intense blight pressure has looked very impressive, with further reports of excellent control in other independent trials in the UK and Holland," according to Mrs Pawson. The company hopes that it will achieve registration in time for the 2008 season.

The change in weather during August has significantly increased blight risk and spray intervals must now be tightened up according to Mrs Pawson. "It is important that growers also get protection on the stems and ridge top with a blight zoospore active fungicide at the earliest opportunity. With the severe blight pressure, we would advise they use Shirlan at the higher 0.4 l/ha rate, to minimise the risk of infection spreading to the tubers," she advocates.