Blight fungicides need top class rainfastness

UK - May 25, 2006

Successful potato blight control relies on applying a robust programme of blight fungicides at appropriate spray intervals from emergence right through to harvest.  In order to ensure good protection of the canopy, blight products must be rainfast and weather proof, especially when the weather is showery or the crop is irrigated, says Dow AgroSciences.

"Farmers need blight fungicides that can make the most of any spray days available and allows them to keep to their planned spray intervals.  They need fungicides that give flexibility to be applied during showery conditions and to fit into their irrigation regimes.  They also need to be absolutely confident that when they apply a product, it is not washed off.  Based on zoxium and mancozeb, Electis has been proven in the laboratory and in the field to be one of the most rainfast of blight fungicides available," reports Andy Leader, Principal Biologist for Dow AgroSciences.

According to Andy, the rainfastness of Electis is mainly due to the lipophilic nature of zoxium.  "With low water solubility and high affinity for leaf wax, the fungicide penetrates the potato leaf surface and moves rapidly into the waxy layers of the leaf, becoming rainfast within one hour and becoming highly resilient to wash off.  Glasshouse studies where the equivalent of 100 mm of rain was applied showed no decline in blight activity from zoxium, compared to when no rain occurred."

Further trials in France, where blight infection was monitored each day following 40 mm of field irrigation, showed that even after seven days, Electis showed only 7% blight infection compared to fluazinam with 81% infection and the untreated with 100% infection.

"Field trials in the UK at AgriSearch reinforced this result.  In these trials 25 mm of irrigation water was applied 6 hours after the fungicide was applied, treated leaf samples were taken, artificially inoculated with blight pathogen and incubated over a period of time.  The Electis treatments showed a trace of blight after one day, 1% blight infection after three days, 5% after five days and only 7% after seven days, compared to 3% infection after one day, 12% after three days, 17% after five days and 18% after seven days for fluazinam.  The untreated showed 68% infection at the final assessment under these highly intense experimental conditions," says Mr Leader.

"Electis is a strong protectant fungicide that is best used from stable canopy onwards.  In five years of successful commercial usage, it has shown excellent activity on both foliar and tuber blight and has been categorised as one of the top foliar blight fungicides as well as one of the best protectants by a panel of independent European industry experts.  British Potato Council blight trials show that that it is highly effective against both foliar and tuber blight.  Its high efficacy combined with one hour's rainfast makes it an essential team player in any blight programme, with the flexibility to suit irrigation regimes or to use in showery weather," concludes Andy.