Blister Spot or Herbicide?

Ask an ExpertCategory: QuestionsBlister Spot or Herbicide?
Matt McMahon asked 5 years ago

Heya folks,
Just found this in a line of Rosy Glow…we’re thinking it may be herbicide damage, though the colour on the fruit and the extent of the damage suggests the fruit was not low hanging, and has an unusual pattern for a weedspray unit. On consulting the APD Compendium, it looks a bit like Blister Spot…has anyone seen anything like this before?

1 Answers
Dennis Payne Staff answered 5 years ago

Hi Matt,
Thanks for your question, we have asked our team of experts and their responses are below.

Expert 1 & 2; To me it is not herbicide damage because the fruit does not have the distinctive damage caused by herbicide where it is bleached around the damaged area.
I am not familiar with Blister spot as I have not come across it. Because of the necrotic areas in the centre of the spots I would tend to think it is fungal in origin. Physical damage would have more discolouration around the spot edges.
Based on your description the problem could also be Lenticel breakdown. This problem has been increasing lately. There are a lot of different perspectives on the causes, but it is certainly exacerbated by hot weather followed by rainfall close to harvest. Attached is an article that I initially prepared when we first started seeing the problem. It may help.

Expert 3: I agree this could be Lenticel Breakdown. A couple years ago I had a grower with similar lenticel marking coming out of cold storage. Fruit went in fine but coming out with similar spotting.
Attached is an article I found out of Washington State.

Expert 4: I have seen this before. I call it a skin necrosis. You see it very seldom, mostly seen on fruit that was harvested late. Sometimes it’s called sunburn necrosis. It’s usually caused by heat generated in fruit by direct sunlight: if the temperature reaches 50℃ for 10 minutes.