What disease is this
Iam in Uganda and my orchard has been attacked by the disease as per photos attached. What disease is this and can it be treated. What medicine is recommended.
Experts in my area have advised me to cut all the trees as it a virus that cannot be treated. I have over 500 trees.
Outside United States
This is a pretty serious situation, so I reached out to the University of Florida's Dr. Megan Dewdney, Associate Professor of Plant Pathology and Extension Specialist at the Citrus Research and Education Center (CREC) in Lake Alfred. This is her response:
"Thank you for your message. Happily, I think I know the disease causing these symptoms on these fruit and leaves from Uganda despite not spending any time there. The symptoms are from a fungus, not a virus, called Pseudocercospora angolensis. It was formerly called Phaeoramularia angolensis. It is a very aggressive fungal disease and will require some form of chemical control if he is not required to destroy his trees by his government. I am not sure if the disease is under some form of a control program from the government which may be the case if this is a recent outbreak of a new disease for them. Removing affected trees has been recommended in other African countries to better control the disease. I do not want to get into the middle of a dispute between a grower and his government not knowing the full situation and laws. There are fungicides recommended but I do not know what is available in his region and what he may be able to afford. It would be better if he could find someone in Africa that could give him some advice that would be more applicable to his situation. What is certain is that he must take some form of management action or he will not be profitable in the future."
For more information on Pseudocercospora angolensis, read this diagnostic fact sheet from the US Department of Agriculture.
We both hope that you find a solution!
Thank you so much. Fortunately there is no dispute with the goverment about cutting down the orchard or not. They would allso be hapoy to know the cure. Atleast give me the names of the appropruate fungicide to use.
The fact sheet I linked to actually goes into great detail about chemical control. An excerpt directly quoted from the fact sheet:
"The most effective fungicides tested on fruit and leaf spot of citrus in Cameroon were copper oxide and benomyl (Menyonga, 1971; Rey et al., 1988). Others found to be effective were mancozeb, tridemorph, triadimenol, captafol and propiconazole (Rey et al., 1988) Applications of mancozeb in the rainy season were not effective in Zimbabwe (Pretorius and Holtz, 2008)."
But it goes even further in detail. It's a very useful publication.