WISCONSIN HORTICULTURE 
April, 1918 
1 18 
FIG. 2— EARLY CLEAN CULTIVATION PROTECTED THIS TREE 
'The development of leaf spot was checked by turning under the dead leaves in early 
spring before the fungus in them could discharge its spor“s. Early clean cultivation 
strongly reenforces snraying, but will not take its place. (Photographed duly 27, 1916.) 
will satisfactorily control leaf spot. 
In these experiments, however, lime- 
sulphur without arsenate of lead gave 
distinctly less satisfactory results than 
when the arsenate was added. 
The time and number of treatments. 
Bordeaux mixture (4-4-50, that is, 4 
lbs. copper sulphate and 4 lbs. stone 
lime in 50 gals., in 1916 and 3-3-50 
in 1917) and lime-sulphur (1-40, that 
is, 1. gal. 33° B. — 1.2946 sp. gr — 
commercial concentrate in 40 gals.), 
both with arsenate of lead, were ap- 
plied, approximately as follows: (1) 
when the blossom buds showed white, 
just before blooming, (2) soon after 
the petals fell, (3) about two weeks 
later, and ( 4 ) just after the fruit was 
harvested. On trees which received 
all four treatments, the disease was 
controlled excellently. Where the 
treatment before the blossoms open- 
ed was omitted, the control was as 
satisfactory as that which resulted 
from the full four treatments. When 
the second or third treatment was 
omitted, the control was not satisfac- 
tory and much foliage was lost. 
Where the last treatment was omitted, 
the result was practically as good as 
where it was applied. Both in 1916 
and 1917, two treatments applied (1) 
soon after the petals fell and (2) 
about two weeks later, gave excellent 
commercial control. In some cases 
it may be advisable to make the ap- 
plication after picking the fruit, but 
ordinarily these two treatments, 
thoroughly applied and reenforced by 
thorough early clean cultivation, will 
be sufficient. They will not be suf- 
lcient if the work is not well done. 
The timing of the first of these 
treatments is a very important practi- 
cal matter. The greatest efficiency 
results when this spray is delayed as 
long as safety permits, because this 
ensures the covering of the greatest 
practicable amount of the rapidly in- 
creasing leaf surface. However, if 
the application is too long delayed. 
the disease will not be controlled. Our 
experiments show that in such sea- 
sons as those of 1915, 1916, and 1917, 
in all of which leaf spot was very 
severe, the first treatment may be 
made with safety at any time during 
the week after most of the petals have 
fallen. Where thorough sanitation 
is practiced and no important source 
of infection is near, this period may 
be slightly extended. Within these 
limits, the timing of the first treat- 
ment should be determined by the 
individual grower to meet his local 
conditions. In the larger orchards 
where spraying equipment is used at 
its full capacity, it may be necessary 
to work through the entire range of 
the safety period. The smaller orch- 
ardist who may wish to increase the 
effectiveness of his spray by a slight 
delay after the falling of the petals 
must take into account the possibili- 
ties of further delay by unfavorable 
weather conditions. In case unusually 
warm weather occurs during or im- 
mediately following the blooming per- 
iod. the first treatment should be ap- 
plied as soon as practicable after 
most of the petals are off. 
The concentration of the spray. In 
1916 and 1917 plats were sprayed 
comparatively with Bordeaux mixture, 
4-4-50, 3-3-50, 2-2-50, and 1-1-50, and 
lime-sulphur, 1-30, 1-40, and 1-50. In 
each case arsenate of lead (powder, 
% to 1 lb. in 50 gals.) was added to 
the fungicide. 
Bordeaux mixture 3-3-50 and 2-2-50 
FIG. 3— LACK OF EARLY CLEAN CULTIVATION ALLOWED LEAF SPOT TO 
DEVELOP 
This tree received no early clean cultivation. Otherwise it was treated as the tree 
shown in Figure 2, which was in the same orchard. Compare. (Photographed July 
27, 1916.) 
