The Coolidge examiner., 1939-03-30
Notes On
Plant Protection
By DR.. ]. G. Brown

PerlOdlclty in Plants:
Plants, like certain animals, ex-
hibit both diurnal and annual
periodic activity. Certain activities
progress during the day and are dis
continued at night; vegetative
growth in one season alternates
with reproduction in another sea-
son. Irregularity in periodic rhythm
may be mistaken for the effect Of
disease.
Occasionally one or more branches
of the cottonwood tree may awaken
to the catkin stage in spring some
days ahead of the other branches;
similar irregularity in rhythm may
be noticed in the blooming of
peach, apple, and other kinds of
trees. Disease if present, is only
incidental.
Even in moist, tropical countries
where temperature remains favor
able for growth throughout the
year, I have seen fruit on one maih
branch of the mango (Manglfera
indica) tree before the other large
branches had visibly commenced
their Towering. Thus not only may
an entire tree show an alienation
of vegetative growth in stem, roots,
and leaves with period of flower
ing and fruiting, but also its in
dividual parts such as branches may
each have its own periodic rhythm
Foot-Rot in Wheat:
Wheat seedlings are susceptible
to foot-rot which may be caused by
several fungi. Among these fungi
are species of Helminthosporium,
Alternaria. Macrosporium and Fusa-
rum. The infected plants plants
are rotted near the soil line, so
that they are easily pulled from the
ground. Accompanying this symp-
tom NAV also be leaf-spots. The
spots are usually elongated length
wise of the leaf; thy vary in color
from very pale yellow or white to
brown or black depending upon the
fungus concerned. Spores that cause
foot-rot are often carried into the
field on the seed.
busting seed wheat with copper
carbonate or organic mercurials IS
an inexpensive control for some
types of foot-rot as we'll as for
sinking smut, but after the dieases
appear in the field little or nothing
can be done to help the crop.
Foot-rot specimens have reached
us from an infected field Of 100
acres In the Salt River Valley.
Date Flower Blight:
Care should be taken in pollinat-
ing date palms in order to prevent
the introduction of flower-cluster
blight. A blight of the flowers may
be caused by a Species of Fusar-
ium, as shown by work done in TINS
department. A paper on the blight
has been published and few re-
prints are now available to those
Flower Seeds as Carriers:
Flower seeds as well as seeds
of crop plants can carry plant
disease germs, therefore, a safe
guard they should be disinfected.
Seeds of China aster are reported
to carry an elterneria causing seedi-
ing blight; Estrytis cincres or gray
mold fungus; Fuserium conglu-
tinane variety callistephi, wilt
fungus; Plasmopara harbarum, an
other seeding-blight fungus, and
Septoria callistaphi and Aschochyta
asteris, which causes leaf blight.
Seeds of stock carry a bacterlum
causing a disease of the plant, and
also the Phoma of blackleg. Seeds
of Sweet William carry the rust
fungus of pinks. Sunflower seeds
carry the watery brown-rot fungus
and a downy-millow fungus. So it
goes with sweet peas, violet, ard
other ornamentals. The process OF
busting and dipping seed will not
destroy parasites inside the seed,
but external disinfection will help
to produce better flowers and will
often prevent soil infestation.
civil SERVICE EXAMINATION