Ladysmith news-budget. [volume] (Ladysmith, Rusk County, Wis.) 1907-1927, 1913-04-11
THE CONTROL OF PEA BLIGHT
Special Bulletin of the Wisconsin
Agricultural Experiment Station


from business men as Well as farm
ers. The pea is a highly specialized d
plant, which, under favorable condi-
tions, develops very rapidly. This
rapid development renders the crop
very tender and likely to be injured
by adverse conditions, such as lack
blight.
The Investigations carried on by
the Department of Plant Pathology of
the Wisconsin College of Agriculture
during the past three seasons indi-
cate that the destructive diseases
known collectively as Pea Blight have
been most important in determining
the success or failure Of the pea
crop Weather conditions have a
marked influence on the extent of
the disease, but our observations and
experiments show conclusively that
blight is primarily caused by fungus
attacks
The fungus causing pea blight may
be present in the seed, where it pro-
duces brownish spots on the seed
coats, or grows inside the cotyledons,
where it cannot be readily disting-
uished On the growing plant the dis
ease makes itself known by the pres
ence of a rot which attacks the
| 4l oly
or brown color. If the plant survives
! this first attack, the stem is so
weakened by the girdling action of
the fungus that it willis quickly when
! hot weather comes. With magnify
/ ing glass, it is possible to see on
the diseased stems small pustules
which are filled with spores or
germs
These spores carry the blight from
plant to plant and from field to field.
When one of them lodges on leaf or
pod and there is any moisture pres
ent, it grows at once into the tis-
sue and causes a brown blotch or
spot, depending on the kind of fung-
us in question. These blight spots on
the pods are very important since
the fungus grows through the pod in
to the young seed beneath and re-
mains alive ready to cause troub-
lie when planted next spring. These
spots on the pod are definite in out
! line and in latter stages have pus-
| tules in the center. 1t is important
to distinguish the blight spots from
similar brown spots caused by hail
injury The hail spots are usually not
as dark brown in color, are indef-
mite in outline, and do not have the
spore- bearing pustules in the center.
In the latter part of the season,
| the blight fungus undergOes re-
markable change on the dead stray
or volunteer vines The oVerWinter-
| ing stage is produced which permits
| the fungus to remain in the pea
rubbish and be ready to cause dis
ease the next year.
| 1t is seen, therefore, that infect
ed seed, pea straw, and volunteer
vines from diseased fields from dan
gerous sources of infection for new
| fields No single specific control
measure can suffice to eliminate all
these conditions. The practical con-
troll of pea blight is rather to be
! brought about by a combination of
several measures, including seed
selection, spraying as possible rem
edial measure deserving further trial
and careful attention to details of
cultivation and crop rotation.
1t is evident that We must use
seed from fields that had no bli ght
the previous year Since pea straw
carried the disease, We should be
extremely careful to avoid using pea
straw, or manure carrying pea straw
on fields that are to grow peas this
season.
The practice followed in many
places of putting the vines in a silo
directly from the viner Is good one
since the spores are unable to with
stand the ensiling process, and the
silage forms a valuable feed for
sheep and cattle. The fact that pea
straw and other rubbish carry the
disease from year to year leads us to
the most important method of blight
control, that of crop rotation. Pea
blight cannot live on corn or grain
plants, hence a good rotation con-
sists of peas, corn, grain and grass.
This prevents an accumulation Of
diseased pea refuse in the soil and
permits the young plants from
healthy seed to germinate without
injury from the blight fungi.