Re: black soot on lemon leaves

K1MIZE@aol.com wrote:
> 
> Barbara:
> 
> I have the same problem on a Washington Navel Orange.  I believe it is a
> sooty mold (actually a fungus?) that is associated with the presence of
> honeydew secreted by scale insects.  I think if you look closely, you will
> find scale insects lining small branches and the central veins of some
> leaves..  The sooty mold will spread to areas that don't have the insects,
> but in my experience, it is always associated with either aphis or scale
> insects.  Some control of the insects can be had by repeated spraying with a
> light horticultural oil.  The sooty mold would probably require a fungicide.

 Hi Kurt   
Scales or some other sucking insect are my guess too. Sooty mould is not
a disease only a symptom. It is due to a very lowly mould which feeds on
the sugary exudate of any sort of sucking insect.  The leaves look
awful, but if you wet them thoroughly you can just wipe the soot off and
the leaves will be found clean green and undamaged under the covering. 

This mould can turn up on any plant any time and always indicates some
"sucker" dropping honeydew. Very occasionally, however, the culprits may
not actually  be on the mouldy plant itself, but on another hanging over
it.

There is no need at all to treat it, as soon as you get rid of the
scales or whatever insect is providing the honeydew it will stop
spreading and soon die of starvation. if only a few leaves are involved
one can easily rub it off, provided the leaf is wet. Alternatively, if
it gets dead and dried it will eventually flake off by itself. It won't
really harm the leaves, just makes them look unsightly. (Well, I suppose
if a lot were thickly covered it might interfere with their
energy-collecting activities).

"Get rid of the scale and the mould will take care of itself" could be
your motto.

Moira 


Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand. (on the "Ring of Fire" in the SW Pacific).
Lat. 41:16S Long. 174:58E. Climate: Mediterranean/Temperate
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