Carl said:
>Dear All: A friend showed up the other day with a small Rosemary plant
>in a Bonsai pot (Mallsai?). It was a gift to her, and she needed help,
>since she saw a few branches that did not look well.
>I suspect that the plant has powdery mildew( using a magnifying
>glass). I removed as much of the growth as possible, but I wondered if
>there was some sort of home-type spray that might help. I did a Google
>search, and read where a spray of milk in a water solution would help.
>Any suggestions?
> I am keeping the tree isolated from my collection and would like to
>help cure the little plant if it is possible.
First of all, the powdery mildew on rosemary is unlikely to spread to
any of your other bonsai unless you have something in the mint family.
Powdery mildews are very host-specific. Second, all the plant needs is
better air circulation; when it's put outside in spring the problem
will be solved. Home recipes for powdery mildew control are not as
good as real control measures, and milk will only work if it's sour,
and that's not going to be welcome in your house. Baking soda will
work if you get a formulated version intended to be used as a
fungicide, but it won't hurt anything to play around with the household
version. A highly refined mineral oil will control the mildew, but may
be phytotoxic to the rosemary; test it out first. A summer oil should
do it. Lime-sulfur will control the problem, but shouldn't be used at
high temperatures (over 80 F); in your house at room temperature there
should be no problem.
Nina
