A team of scientists at the University of Florida, Corteva Agriscience and Syngenta Crop Protection recently published a meta-analysis using data from 25 field trails conducted in Florida from 2005 to 2021. The analysis showed that Captan applications significantly improved marketable yields and reduced Botrytis fruit rot (Fig. 1) and anthracnose fruit rot incidence. They showed that weekly captan applications would return the investment spent on the fungicide application during low, medium and high strawberry pricing periods. So, although captan has been around for many decades (that’s the “old” part), it’s still effective (that the “gold” part). One of the reasons captan is still effective lies in its mode of action. Captan is considered to have a “multi-site” mode of action, meaning that it attacks the target fungus in several ways. This makes the risk of resistance development very low.

That’s Florida. What about California? This year, we had our best Botrytis fruit rot (BFR) trial in 10 years. BFR incidence in our non-treated plots was at 38%! It takes a year with high BFR levels to separate out the effective from ineffective treatments. We included two formulations of captan (Captan Gold and Captan 80WDG). With both formulations, BFR was at 22% or a 42% reduction compared to the non-treated. That’s an impressive result and it took a high disease year to show it. When disease levels are less than 5%, we do not see the same level of performance.

The other multi-site fungicide that showed good efficacy was thiram. In thiram-treated plots, there was an average of 15.5% BFR which is a 59% reduction over the non-treated; another impressive result from a multi-site mode of action fungicide.

In both cases (captan and thiram), we have old fungicides with multi-site modes of action with good efficacy against BRF.