Mealy bugs

Uli Urban
Sun, 08 Feb 2009 10:51:00 PST
Dear Linda,

You do not tell if you have mealy bugs on the aerial parts of the plants
or mealy bugs on the roots of the plants or both.  There are two kinds
of mealy bugs, one living above ground on the plants preferring dense
angular foliage like the heart of Clivias or Hippeastrums or Aloes but
also spreading to less dense parts of the plants causing the typical
cotton wool that protects the insect. This cotton wool is not cotton at
all but a fatty substance that is impermeable to water and to water
based sprays.
With root mealy bug you will find the same kind of cotton wolly
structures (not as thick as on aerial parts) and whitish insects visible
with the naked eye on the roots of the plants below the surface of the
soil. When unpotting they often leave a whitish mark on the inside wall
of the pot.
Being fat in the broader sense this "cotton wool" can be destroyed by
alcohol or soap but the plant has to take that treatment. I have done
the following in the past: sprayed the plant thoroughly with 70%
industrial spirit with some detergent in it (this is used here to clean
glass) waited some time and then washed everything off with tepid water.
And then I treated with Imidacloprid (Provado), as Dell mentioned.
Reducing the number of insects first seemed necessary in the given
cases...... but it will also work without using alcohol first. This can
only be done to the aerial variant of mealy bugs.
Imidacloprid is systemic and will also work in places where you cannot
spray it and it works against the more difficult to eradicate root mealy
bugs as well. I find root mealy bugs far more dangerous as they often
spread unnoticed. Only on repotting the damage becomes visible. On the
other hand I wonder how much the plants suffer from them as I remember
having unpotted seemingly healthy plants with totally infected
rootballs, Pelargoniums seem to attract this pest particularly.
Capillary matting, soaking one pot after the other in the same bucket,
overcrowded greenhouses help spreading this pest as well as re-used pots
without washing them (I now do that...)
I think I managed to keep my new greenhouse clean of that pest because
EVERY pot was soaked in Provado before it was allowed in. Some surprises
happened though but these were dealt with immediately including their


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