Question
Mandarin Tree
I have a mandarin tree that is infected with a whitish substance more likely it is a fungus, accumulated on the fruit itself as well as some of the leaves which got dark spots as well, previously the tree had a lack of iron which was treated succesfully with chelated iron.
Then I sprayed the tree recently with a mixture of copper oxychloride & white oil but I didn't get good result still the fungus is persisting.
Any advice, to help me.
Regards,
Maurice - NSW-Australia.
AnswerHi Maurice,
It looks like you have two problems with the mandarin plant. The black substance on the leaves is most likely sooty mold. It is a type of fungus that lives on honeydew which is a sticky substance produced by some insects. I suspect that the white stuff in your photo is evidence of an insect. The section of your picture with the white stuff was a bit blurry, so I could not determine the exact type but I suspect spittle bugs and/or aphids.
You mentioned that you treated with 2 products without results. The copper product provides control of fungal and bacterial spots, but not insects so it is not surprising that you did not achieve control. I'm not sure what the white oil you used was. I am guessing some type of horticultural oil which is not that effective for spittle bugs because they hide in the spittle (white stuff).
The best treatment is to use a strong stream of water to wash the affected plant parts. You may need to use your fingers to help loosen the sooty mold and spittle. If you see new white areas develop, then you should repeat treatment. If desired, you could treat the plant with horticultural oil after you have washed it. This will help control any nymphs that are difficult to see. Once the insect problem is controlled, the sooty mold will no longer have anything to feed on and will disappear.
Good Luck,
Jen
