Hi, I have a pink grapefruit plant that I grew from a seed around 12 years ago. This spring I have noticed a yellowing and brown mottling occurring in the leaves but, try as I might, I am not able to properly diagnose it. I'm not particularly green-fingered and this plant is my pride and joy. I was hoping somebody on here could help me diagnose the issue. I am hoping it isn't citrus canker, and was thinking it may be citrus blackspot?
It certainly looks like a fungus of some kind, although not blackspot to me. Doing a google search of "citrus black spot leaf" images, they look quite different since yours look mostly brown instead of black. My guess would be a bad case of greasy spot, though it does not look exactly right for that either, though pretty close... for most of these fungal issues a copper based fungicide seems to be the recommended treatment... here are a few of links that may be useful: Fact Sheet: Greasy spot | Citrus Diseases Citrus Fungus Issues | Potted Citrus Trees Greasy Spot Severity Rating Scale | KeyPlex Plant Nutrition
Yes! That looks to be the case! And the description matches perfectly the symptoms, with yellowing on top and brown blisters to the underside, and the majority of leaves affected were at the outermost points of the plant, so they experienced higher rainfall and temperature variations. Thank you very much, I really appreciate your help! Copper based fungicide on the way.
