Can Serenade help cabbage growers sing?

By Andy Richardson, Allium and Brassica Centre, October 2018

Rovral WG (iprodione) was approved as a post-harvest drench for long-term stored cabbage for over 30 years.  This fungicide effectively controlled Botrytis, which in untreated crops can lead to dehydration and trimming losses of over 60%.  The loss of this approval in June 2018 was a major blow to storage cabbage growers.

As part of SCEPTREplus, a trial looking at possible replacements for Rovral was commissioned last autumn and these trials were undertaken in a commercial cabbage store at the Allium & Brassica Centre, based in Kirton, Lincolnshire.

Cabbage was harvested and treated in early December 2017.  The trial tested five conventional fungicides and three biopesticides and compared them against a plain water and Rovral WG control.  All applications were made as they would be commercially, by spraying the products over the cabbage in the equivalent water rate of 20L per tonne.   After treatment, bins were held at 8-10°C for 2 days to allow them to drain and for the bio-pesticides to colonise the cabbage heads.  Bins were then placed in a commercial refrigerated store and held at 0.5-1°C until removal for assessment in mid-June 2018.

After removal from store, samples were given a visual disease score as well as being assessed for weight loss (due to dehydration), trimming loss and unmarketability of heads due to significant disease infection. There were positive efficacy effects for post trimming andmarketable weight with three of the conventional fungicides, all of which gave a significantly higher percentage of marketable yield than the water control.

Looking at the number of marketable heads, the same three products, plus Serenade ASO, had significantly more marketable heads than the water control.

All six conventional fungicides (including the formerly approved standard, Rovral WG) gave a clear visual and significant improvement on Botrytis compared to the water control.

Out of the three biological products tested, only Serenade ASO appeared to give any control.  Following its successful performance, an application was made for an Extension of Authorisation for Minor Use (EAMU) for Serenade ASO, which was granted for use as a post-harvest drench. For the full authorisation, click here.