Reminder: Blackcurrant Leafspot timing is upon us

~Geoff Langford

In recent years we have been a bit concerned that applications targeting leafspot control have been being applied later than is desirable for best effect.

Back in March, I unearthed the classic paper by Mulholland and Beresford from 1989 and this is worth repeating now.  This paper covered leafspot spore trapping in multiple sites and I quote direct from the paper:  “Ascospore release always began in late August or early September and declined to an undetectable level by mid November.”  They further state “Fungicide protection should be maintained from the time leaves emerge until the grape stage of flower development.” 

The focus needs to be on varieties that we know are especially susceptible to leafspot like Magnus, Murchison and Blackadder.  The beauty of controlling the initial infection is that if you can achieve that, it means that the fungus does not cycle within the plant and create carry-over to next season.   

I am often surprised at how quickly plant development happens at this time of year and I have selections already in flower so it is easy to get caught out with the speed of development. 

The right timing for leaf spot sprays is between green tip and tight grape, as seen below.

Chemical options are Thiram, Amistar and Topas, but we are also looking at adding Proline that will hopefully be confirmed next week.

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