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Blight Fungicides must be rainfast, says Interfarm

Rainfastness is a vital feature of a blight fungicide according to the results of a survey of potato growers and advisors, conducted by FoodFen company Interfarm UK Ltd. Just under half of farmers reported that they wanted efficacy, first and foremost, but around 40% said that rainfastness was the next most important feature.

"Farmers clearly want a product that is absorbed onto and into the plant quickly and will resist removal by irrigation or by rainfall. Based on zoxium and mancozeb, Electis has been proven in the laboratory and in the field to be one of the most rainfast of all blight fungicides. It is rainfast within one hour, making it an important product to fit into irrigation programmes or in showery periods when the risk of blight is at its highest." comments Dr. David Stormonth, Technical Manager for Interfarm, who market the blight fungicide, Electis.

Zoxium has a high affinity to the leaf wax, making it very lipophilic. It also rapidly penetrates the waxy cuticle layers and then into the leaf so it becomes highly weatherproof. Glasshouse studies in which 100 mm of rain was applied showed no decline in blight activity from zoxium compared to when no rain occurred. This was not the case for fluazinam that declined from 87% with no rain to 66% after rain. Another set of trials in France, where the percentage blight infection was monitored each day following 40 mm of field irrigation, showed that even after 7 days the Electis treatment was showing only 7% infection compared to fluazinam with 81% and the untreated 100% infection after the same time period. The same work proved that Electis became rainfast within one hour.

Electis contains 8.3% w/w zoxium and 66.7% w/w mancozeb, formulated as a WDG. It is recommended on all varieties of potatoes at spray intervals of 7 to 14 days. It has a dose rate of 1.8 kg/ha in 200-600 litres of water per hectare. It has a maximum number of treatments of 10 per crop and a harvest interval of 7 days. It is packed in a 3-hectare pack (5.4 kg).