February 2015. A mango in Malawi was seen with white patches on the leaves and the sender asked what they might be (Photo left, top & below).
The images were sent to Jane O’Sullivan, University of Queensland, who said she suspected herbicide injury. That might be easy enough to rule out, if there hasn’t been any used. If nutritional, the most likely fit for the symptoms is manganese deficiency, although I’m not familiar at all with mango. It’s mainly on young leaves, and mostly involves interveinal tissue collapse. The paleness of the surrounding crop would be consistent.
I came across zinc deficiency in cassava in northern Malawi, and the virologist who showed it to me said the symptom was quite common and had been baffling them. In the same area, I found boron deficiency on sweetpotato. Basically, it was an alkaline soil, and most micronutrients were consequently low, but the symptoms depended which nutrient a crop was most sensitive to. Maybe for mango, it’s manganese. It seems to be for kava, for instance.
Later, in May 2015, a photo was sent by the Editor, which showed similar symptoms (photo right, top). This was said to be caused by thrips.