Chris Cooper and Rob Saunders, vine specialists in the Hutchinsons Horticultural Team, discuss what has been going on the world of UK grown Wine Grapes.
On 22nd November at the picturesque Denbies Wine Estate, Surrey, reminded growers if they are going to apply the herbicide Kerb 400 (propyzamide) now is the best time as soil temperatures are low enough (it has to be applied between October and end of January), but also heralded the start of the inaugural WineGB Technical Conference, attended by growers representing over 50% of the UK planted area of wine grapes and organised by WineGB Viticultural Working Group (VWG).
After the introductions by Stephen Skelton, Chairman of the VWG, Dr Mark Lukac, Professor of Ecosystem Science at Reading University, was the first speaker with an intriguing paper entitled “Fungi in the vineyard – but not the ones you think!” He explained how mycorrhiza fungi may influence vineyard terroir; how good soil conditions encourage these fungi and how they add resilience to vines when under environmental stress. A question from the floor was asked about the effects of foliar fungicides or ground applied herbicides on mycorrhiza, Dr. Lukac dismissed any effects from conventional approved herbicides but was unsure about fungicides. Rob explains logically effects of fungicides on soil dwelling fungi will be a function of dilution and persistence. The idea of foliar spraying is to maximise interception onto the target and limit run-off and drift so the proportion of dilute spray hitting the soil will be limited. Persistence of fungicides is measured in half-life –the time it takes for half the material to break down- as examples Teldor (fenhexamid) has a half-life of 1.16 days, Scala (pyrimethanil) is 29.5 days, copper oxychloride has a half-life of 10000 days.
Chris commented that with limited herbicide choice for the weed-free strip below vines, growers were looking at products such as Pelargonic Acid. Although approved, being a mild acid may have a cumulative effect in the soil, our intention is to trial this in 2019.
Rob’s view is that of significance for mycorrhiza is vegetative cover. These fungi rely on plants for their carbon so herbicides and/or cultivation would be expected to have the greatest effects, albeit indirectly. Cultivation is the most deleterious activity for mycorrhiza. So when controlling weeds in the under-vine area by cultivation, keep it shallow. Rob says he likes to see a grass or herbage sward covering tractor alleyways where vines roots will have spread in an established vineyard.
The conference was a huge success, in the technical topics debated and catching up with and meeting growers and managers. Further topics will be discussed in future months.