Importance of Rainfastness in blight products

UK - May 02, 2005

The recent DEFRA survey on climate change showed that, along with twice as many summer days with a temperature above 25°C, the UK is being subjected to more heavy downpours of rain.  Many potato growers would agree with this when looking back on last years' weather pattern and the heavy rainfall experienced in many parts of the country.  This could explain why rainfastness is considered to be such an important feature of any blight fungicide, says Dow AgroSciences.

"Farmers want a blight fungicide that makes the most of the spray days available and so allows them to keep to tighter spray intervals.  They need fungicides that give flexibility to be applied in showery conditions and to fit into irrigation regimes.  In a recent market survey, growers and advisors rated Electis from Dow AgroSciences and Ranman TP from Belchim Crop Protection as the most rainfast blight fungicides.  Based on zoxium and the multi-sited mancozeb, Electis has been proven both in the laboratory and in the field to be one of the most rainfast of all blight fungicides available," reports Andy Leader, Principal Biologist for Dow AgroSciences.

Zoxium is very lipophilic, which means that it has low water solubility and high affinity for leaf wax.  It penetrates the leaf surface and then moves rapidly into the waxy layers of the leaf, becoming rainfast within one hour and highly resilient to wash off.  Glasshouse studies in which 100 mm of rain was applied showed no decline in blight activity from zoxium, compared to when no rain occurred.  Field trials in France, where the percentage blight infection was monitored each day following 40 mm of field irrigation, showed that even after seven days, Electis showed only 7% infection compared to fluazinam with 81% infection and the untreated with 100% infection.

"Trials last year 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 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.  Being rainfast within one hour makes Electis an important team player in any blight programme, with the flexibility to suit irrigation regimes or to use in showery weather," says Mr Leader.

"Electis is a strong protectant fungicide that is best used from mid-season onwards, during full canopy and into the early canopy senescence phase.  It shows 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 in Rosemaund and Auchincruive over the last two years have also shown Electis to be highly effective against both foliar and tuber blight.  It is an essential team player to incorporate into a cost-effective blight control programme," concludes Andy.