Chris Cooper and Rob Saunders, vine specialists in the Hutchinsons Horticultural Team, discuss what has been going on in the world of UK grown wine grapes.
22 November saw the inaugural WineGB Technical Conference, which was held at Denbies, and attended by growers representing more than 50% of the UK planted area of wine grapes.
Dr Mark Lukac, Professor of Ecosystem Science at Reading University, kicked off proceedings 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 asked about the effects of foliar fungicides or herbicides on mycorrhiza; Dr. Lukac dismissed any effects from conventional approved herbicides but speculated that fungicides may have an impact. Rob reflected that logically, effects of fungicides on soil dwelling fungi will be a function of both dilution and persistence. Dilution in this sense would be the ratio of active ingredient relative to the amount of soil - typically in the region of 750 grams of active added to 160 tonnes - the weight of the top centimetre of soil covering 1ha of ground. Persistence of fungicides is measured in half-Iife – this is 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, Option (cymoxanil) 3.5 days. The stand out material in terms of persistence is copper oxychloride with a much greater half-life than other fungicides, at 10,000 days.
Bob said that of significance for mycorrhiza is vegetative cover. These fungi rely on plants for their carbon so anything that removes them would be expected to have significant effects, albeit indirectly. Cultivation is likely to be the most deleterious activity when it comes to mycorrhize, many of which have a ﬁlamentous structure so are susceptible to mechanical damage. If you are controlling weeds in the under-vine area by cultivation, keep it shallow.
Chris commented that with limited herbicide choice for the strip below vines growers were by necessity looking at products such as Pelargonic Acid and Acetic Acid, which will be undergoing trials in 2019. More immediately the colder winter months are the time to apply Kerb, which will control a range of grass and broadleaves, and must be applied by 31 January.
The conference was a huge success, not only in the technical topics debated but in catching up with and meeting so many growers and managers. Further topics will be discussed in future months.