Potato growers and advisors cannot afford to be complacent about controlling potato blight, nor about the need to manage the risk of fungicide resistance, warns Dow AgroSciences.
"Potato blight is a devastating disease which requires a robust and planned approach to its effective control. It also appears to becoming more aggressive. Blight is a disease that has a very short infection cycle and therefore can yield a prolific number of generations in any one season. This leads to the need for frequent fungicide use and thus increases the likelihood of resistance. Products with multi-site activity such as mancozeb (as in Dithane NT and Electis) are at low risk to resistance. No resistance to mancozeb has been detected even after thirty-plus years of use. Working on six distinct metabolic sites within the fungus, mancozeb's multi-site activity is important for resistance management and explains why this active ingredient is still incorporated into nearly two-thirds of all blight fungicides used in the UK, including some of the most recently launched products," says Andy Leader, Principal Biologist for Dow AgroSciences.
"Other low risk products include those with a unique mode of action, such as zoxium, one of the actives in Electis. Zoxium works by disrupting microtubules and inhibiting nuclear division, thereby stopping the spore germ tube from penetrating the plant and also inhibiting the production of zoospores, which are the cause of tuber blight. It also has no known resistance and it will control all known blight races and strains, including phenylamide resistant strains. Electis also contains mancozeb which is the active ingredient of Dithane NT adding to its strength in an anti- resistance management programme." MORE………
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"Fungicide resistance is a persistent worry for growers and advisors, whether it is in potatoes or cereals, and measures to minimise this problem should be implemented when planning an effective disease programme. General advice is to alternate fungicide groups within a programme, to use multi-site products more frequently and to integrate products with more than one active ingredient throughout the programme," advises Andy.
"Starting at the stable canopy stage, Electis performs very well in a programme, alternating with complementary fungicides with different modes of action such as cyazofamid (Ranman TP), fluazinam (Shirlan) and cymoxanil and mancozeb (Curzate). In three years of BPC trials, the Belchim/Dow manufacturers' programme, consisting of two treatments of mefenoxam and fluazinam (Epok), followed by Electis alternating with cyazofamid up until desiccation gave the best control of foliar and tuber blight and resulted in excellent yields. In a similar programme in 2005 but with fluazinam plus cymoxanil instead of cyazofamid, this was one of the higher performing programmes that produced the highest marketable yield. Best used from stable canopy onwards right through to early canopy senescence, Electis acts as the backbone to any blight programme. Its use is a sound approach to ensure that foliar and tuber blight are well controlled, that marketable yields are enhanced and that the risk of resistance is minimised," says Mr. Leader.
Electis contains 8.3% w/w zoxium and 66.7%w/w mancozeb, formulated as a WDG. Applied from stable canopy onwards, 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) and is marketed by Dow AgroSciences.
