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This will be the last industry scouting report for the season. The main questions pest-wise for post harvest are:
We now know that scale crawlers are currently active, and if you’ve got a block with historically bad scale, we discussed the post harvest control options (https://berryworldnz.wordpress.com/2025/01/28/post-harvest-sprays-for-blackcurrants/)
As for spider mites, in the blocks I’ve looked at, the level of predators seems pretty good. But in the monitored blocks, that ratio isn’t looking so high.
I’m afraid making an informed decision on the necessity of a post-harvest miticide will entail looking at each block, as we don’t think a single block on a farm is a fair representation. Also, the leaf damage seen at this time of year is largely historical (leaves with spider mite bronzing don’t re-green), and the visual damage doesn’t represent what’s currently crawling around under the leaves. So get out the 10x lenses, and remember what a predator mite looks like!
The blackcurrant industry doesn’t have a specific guideline about how many predatory mites are enough to control the spider mites. However, I was talking to a blueberry crop scout who, informally, has found that if she’s seeing 3-4 predators on a leaf that is 80% covered in spider mites, those predators are going to win.