Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1916-01-11
Arseuate Of Lead for Apple scab.

Arsenate of lead is widely used upol
apple trees as an insecticide for chewin,
insects. Somewhat unexpectedly, II
connection with some sraying expert
ments at Highmoor Farm, the patholo
gist OF the Maine Agricultural Expert
ment Station secured evidence indicat
ing that it also apparently possesses con
siderable value as fuugicide In prevent
ing apple scab. Since that time, def
| mite experiments with arsenate of lead
the results of which have been reported
from time to time, have been carried OF
in connection with other spraying expert
ments at the farm. The object has beer
to determine the value of this apparent
discovery, il any, and more especially tC
see If the use Of arseDate OF lead as
fungicide as we'll sSan insecticide would
suggest any notifications or improve
ments of existing spraying methods.
The data for 1915 have now been com.
pleted and tabulated.
The combined results of experiments
covering four successive years show
quite conclusively that this well-knowu
insecticide has considerable fungicidal
value as preventive of apple scab. The
paste arsenate of lead was used In the
earlier experiments, but recently the dry
or powdered form has been substituted,
one pound of the latter being equal to
about two pounds of the former. Many
orchardists use about the equivalent of
one and one-half pounds of the powder
three pounds of the pastel to each 80
gallons of summer strength lime-sulphur
in the combined spray. In the High
moor experiments, no trouble has been
experienced in controlling chewing in
sects with one pound of the powder in 90
gallons of lime-sulphur. In these ex-
periments, where srsenate Of lead has
been applied alone for scab, no attempt
has been made to use 1t stronger than
two pounds of the powder to 30 gallons
of water.
Seasonal conditions have been such
that scab did not develop sufficiently
to give every year as rigorous test as
might be desired. However, in 1913
nearly 80 percent of the apples on the
unsprayed plot were scabby. Almost
perfect control was obtained where the
plot was sprayed three times with two
pounds of dry srsenate Of lead in so gal
ions of water; in fact, 1t was slightly
better here than on an adjoining plot
SPRAYED with summer strength lime
sulphur to which one-half this amount
of the same poison had been added to 30
gallons. Moreover, one pound OF dry
arsenate of lead alone in 80 gallons Of
water reduced the amount of scab from
80 to less than 16 percent.
While scab was common and destruc-
tive in some parts of Maine in the sum-
mer of 1915, it was not especially severe
on the unsprayed plot at Highmoor.
Lime-sulphur containing one pound of
dry arsenate OF lead In so gallons gave q
fraction of one percent better scab con-
troll than did double the amount of the
poison applied alone In an equal amount
of water. On account of russeting, only
about 90 percent of the apples ben
Davis Variety were merchantable where
the combined lime-sulphur and arsenate
of lead was applied. In contrast with
this, because of freedom from russeting,
the larger amount of arsenate OF lead
used alone gave over 81 percent of the
same grade of fruit.
The high efficiency of arsenate OF lead
in scsb control suggested the following
possible modification of summer spray
ing practice. Use strong fungicide
combined with the smaller amount OF
arsenate of lead when the blossom buds
are showing pink. For all later applica-
tious, depend entirely upon arsenate OF
lead, using at least two pounds of the
powder or four pounds of the paste to
each so gallons Of water. Work along
this line has been going on for two sea-
sons.
The crop on plots sprayed in this man
ner has in each case been very free from
scab, but on account of the fact that
during both seasons omission of the first
on adjoining plots sprayed
with the ordinary combined lime-sulphur
aud arsenate of lead spray has led to no
increase in scab, 1t has been impossible
to draw definite conclusions regarding
the chief object in view. However, all
the evidence obtained tends to confirm
the results secured where arsenate OF
lead was used alone throughout the sea-
son and in previous years.
Lime sulphur 20 percent stronger than
standard summer dilution has so far
proven to be the most satisfactory for
the stronger fnngicidal application
when the blossom buds are showing
pink. Bordeaux mixture, 8 $50 formu-
la, even when applied at this time when
the leaves had just begun to unfold was
undoubtedly responsible for . certain
amount of unexpected foliage injury
which developed later. 1t should be re-
membered in this connection that the
Ben Davis was used in these expert
ments, a variety particularly susceptible
to spray iDjury.-Chas. D. Woods.
a .,.a oo,. .cd R;.Ia 4 oorn to EARN