Rob Saunders is a member of the WineGB viticulture working group, an agronomist with Hutchinsons and a board member of AHDB Horticulture. SWD was less of a problem for UK vine growers in comparison with 2017, but Rob wanted to update vineyard managers on current findings, future implications and control strategies for this relative newcomer to the UK.
In a survey of vine growers, 60 per cent admitted that they would not be able to identify SWD. Rob was keen to give growers the tools to get control of the pest, beginning with all the resources on the AHDB website, including a very helpful video. He warned that female SWD, which can lay eggs in unripe fruit, unlike any other fruit fly species, can lay up to 300 eggs in a lifetime. SWD like humidity and the middle of the canopy is the best area to look for them, by testing fruit for eggs and larvae. The combination of hope and denial by vine growers, even though there had been a lot of warnings, was obviously a poor strategy as the early harvest in 2017 caught many out. SWD egg-laying is suppressed at temperatures over 30C, so 2018 wasn't so bad as 2017, but the survey showed that 40% of growers had applied Tracer. Damage by the fly allows botrytis and sour rot to gain entry. Research in Bordeaux has shown that if SWD was controlled there was less sour rot. Multiple approaches to control, from crop hygiene to monitoring and early trapping around the edge of vineyards, are the only answer, targeting the fly all-year-round.