Maria Luna and Mark Bornfeld wrote:
>> My holly bush is totally infested with something I cannot identify. The
> underside of almost every leaf has multiple white silky deposits of
> consistent shape and size: about 1 centimeter long, 3 millimeters wide
> and ½ millimeter thick. Some of the plaques have a black spot at one
> end. Although it has not caused a large proportion of the leaves to be
> damaged, some are dropping off, completely brown (I don't know if the
> leaf damage is related to the white stuff).
>> Any ideas as to what may be the problem and how to eradicate it?
I'm not sure and have never had this infestation on my holly, but
consider scale. These insects have sucking parts and are white and about
the size you describe. They do attach themselves to the undersides of
the leaves. Holly leaves are pretty tough, so these guys must be
Control is difficult. One possibility might be physical removal, with
insecticidal soap. However, the size and shape of holly leaves would
discourage me. A systemic insecticide should work, but be careful,
these are pretty poisonous. One I have used upon occasion is Isotox.
I suggest you get a gardening book and look up scale insects. Be aware,
there are many varieties, so the pictures may not look exactly like
yours. The book should have instructions for control.
A lesser possibility is mealybugs. These are usually greenhouse pests
and can't take cold weather. They also attach to the undersides of
leaves and are white, but the description usually includes the cottony
material with which they enclose themselves. Since you didn't mention
that, and you certainly would, then I rule out mealy bugs.
St. Louis MO