Enemies and Diseases.
The gladiolus has almost no enemies, and the same may be said of
diseases. The bulb has a very unpleasant taste, and is somewhat
poisonous. It is not eaten by mice or grubs. The black aster beetle is
fond of the flowers, and is quite a pest when very abundant. These
insects have a preference among colors, and attack the red flowers
first, especially a scarlet sort named Bertha. They will single out the
spikes of this variety in a field of mixed colors, and devour the very
buds as soon as the red comes in sight. They are especially troublesome
when the weather is hot and dry, as they can then fly readily. When it
is cool and damp, if jarred from the spikes they fall to the ground, and
are slow in regaining their places. The grower of flowers, either
amateur or commercial, finds in these insects an enemy hard to contend
with, but the grower of bulbs pays no attention to them, as they do him
no harm.
In regard to diseases, bulbs sometimes become scabby, but this seems
rather an accident than a disease. It is apparently due to conditions,
and is not perpetuated by heredity. Perfectly sound bulbs may produce
scabby ones, and vice versa. If healthy bulbs are planted in a place
that is too wet, or that is subject to frequent overflow, or if they
come in contact with barnyard manure in the ground, or if the foliage is
seriously injured in the growing season, the product is liable to be
scabby. Some years ago I had a field of gladioli, one end of which
proved to be a runway for dogs, and the plants that came in their way
were broken, or partly broken. As a consequence, many of the bulbs in
that part of the field were scabby, but these planted in a different
place, produced smooth ones the next season. If bulbs are taken up and
cured immediately after the tops have been injured, by wind or
otherwise, they will be sound and in good condition for the next year,
even though not half grown; but to be deprived of their foliage, or a
large portion of it, while the roots remain undisturbed, appears to
destroy the balance, and cause bad results.
In some localities the gladiolus is affected by rust, which turns the
tips of the leaves brown in the growing season. If this is a disease,
the remedy does not seem to have been discovered, but in numerous
instances careful observation will show that it is due to local causes.
The foliage is sensitive to atmospheric conditions, and cannot be
successfully grown where it is subject to poisonous gases. Smoke from a
pottery carried over the bed by prevailing winds is almost sure to be
fatal. Salt is thrown into the kilns to glaze the ware, and the
chlorine set free is deadly to many plants. Even smoke from factories is
more or less injurious, and many cases of rust can be traced to some
such source.
Taken all in all, the gladiolus is one of the most reliable of crops.
(See Note.)
Note:--There are three well defined diseases affecting gladiolus
bulbs during growth and in storage, soft rot, hard rot, and scab.
There is no cure for the two former, but they may be controlled by
discarding all affected bulbs and planting in fresh soil free from
animal manures. Scab may be greatly reduced by soaking all diseased
or suspected bulbs, after removing the outer coatings, for twenty
minutes in a solution of bichloride of mercury, fifteen grains to
each gallon of water, or for same time in solution of formalin, one
pint to thirty gallons of water.