Potato blight is the most devastating disease of potatoes. It causes damage through destruction of the haulm, adversely reducing yield and quality, and through tuber blight which affects marketable yield, quality and storing ability. As blight can be so potentially damaging and can devastate a crop within days, growers need to use a robust programme of fungicides applied at appropriate spray intervals, starting before the disease is established right through to harvest.
The inclusion of the protectant fungicide, Electis (zoxium and mancozeb) in any blight control programme appears to add to the overall effectiveness of blight control as well as to the final marketable yield, says Andy Leader, Potato Specialist for Dow AgroSciences.
"Electis helps to increase yields and profits, by the effective prevention of leaf, stem and tuber blight. In trials it has shown to contribute to equal or better yields than many other existing blight products and programmes. In a 2006 BPC/SAC trial, an Electis based programme resulted in the top yield. The eleven spray programme with a seven day interval consisting of one Dithane (mancozeb) spray, two Epok (fluazinam + metalayxl-m), one Curzate (cymoxanil + mancozeb), two Electis (zoxium + mancozeb), two Ranman (cyazofamid), a further Electis and two Infinito (fluopicolide + propamocarb) sprays gave a final blight-free yield of 42.32 tonnes per hectare. Compare this to the woeful 13.4 tonnes/hectare in the untreated and you realise how important it is to maintain a strong programme throughout the crops' life," says Andy.
Looking at other approaches, in the same trials a programme of three Tattoo (propamocarb + mancozeb) followed by seven Shirlan (fluazinam) sprays gave 31.66 t/ha and a programme of three Tattoo followed by seven Valbon (benthiavalicarb + mancozeb) with Zinzan resulted in 32.32 t/ha.
Andy points out that the Electis-based programme gave over 10 tonnes per hectare more than these other two programmes. "With potatoes at an average price of £160/tonne, this makes a significant difference in the level of returns."
"The average cost of a potato blight programme which includes top class foliar and tuber blight protection is around £150/ha, a cost incidentally that has remained broadly similar for at least the past three years. This is equivalent to about 2% of the crop's value, (assuming a 42 t/ha crop at £160/tonne). The risk of inadequate blight control in potatoes is too high a risk to take, especially in crops destined for pre-pack or baking markets. Growers need to make sure that they use a robust and effective blight control programme throughout the life of the crop," reminds Andy.
According to Andy, Electis is a strong protectant fungicide, best used from stable canopy onwards when tubers are initiated. "It is highly effective against foliar, stem and tuber blight and rates at least on a par or better than any newly introduced or traditional blight fungicide in terms of performance. It is a highly suitable product to integrate into any blight programme. Its results are consistent and programmes containing Electis appear to perform better."
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-ha pack (5.4 kg).
