Journal of Agricultural Research 
Vol. XXIV, No. 6 
510 
third day; Plate i, B on the fourth day; Plate i, C on the fifth day; 
Plate I, D at the end of a week; Plate i, E in about 10 days, and Plate 
I, F in 3 or 4 weeks. 
If the leaf is not entirely killed, as was usually the case in these experi¬ 
ments, the injury is worse at the margin and in roundish spots of all 
sizes in the interior. If there are abrasions through the epidermis, these 
become centers of discolored areas. In most of these spots, however, 
there is no visible mechanical injury, nor do they correspond to depres¬ 
sions in the leaf where the spray mixture collected in greater abundance. 
The degree of injtiry was measured by the proportions of injured 
to uninjured surface. In the case of the apple, if more than half of 
the leaf is killed it usually drops prematurely. The position of the 
injured area varies this rule somewhat. Injury near the midrib or near 
or on the petiole is more likely to cause dropping than if on the margin, 
especially toward the tip. Not all plants are equally inclined to shed 
their leaves. The bean, for example, will do so much more readily than 
the apple, while the tomato retains them more tenaciously. 
For the purpose of comparing results for tabular data, etc., a condensed 
method of expressing the degree of injury is highly desirable. For this 
purpose the terms, very slight, slight, moderate, bad, very bad, partly 
defoliated, and defoliated were adopted. As applied to individual 
leaves the following definitions apply to the records in this paper: 
Very slight= the least amount of injury that is easily seen. 
Slight = a few small spots up to one-eighth of the area of the leaf 
killed. 
Moderate=one-eighth to one-fourth of the area killed. ' 
Bad = one-fourth to one-third of the area killed. 
Very bad=one-third to nearly all of the area killed. 
As applied to the sprayed plants or branches as a whole the following 
definitions served as a guide: 
Very slight=a few small spots on a small proportion of the leaves; 
no le^ seriously injured. 
Slights about one-eighth to one-fourth of the leaves showing 
spots, but few, if any, of them seriously injured. 
Moderate == about one-third of the leaves more or less injured. 
Most of the leaves showing only small spots, but a few of them 
may be injured to the degree classed as “bad.” In the defini¬ 
tions given above for individual leaves we have applied this 
term to the most serious injury that can be done without com¬ 
mercial injury to most crops. 
Bad = approximately half the leaves injured, most of them only 
slightly, but some in “moderate” degree. This we have con¬ 
sidered to be just enough injury to class as of commercial 
importance to most crops. 
Very bad = most of the leaves more or less injured, some of them 
nearly killed. 
Partly defoliated = a portion, but not all of the leaves entirely 
killed or so badly injured that they dropped off before the 
notes were taken. The leaves of some kinds of plants when all 
or nearly all the tissue is killed, will drop off. The leaves of 
other plants, as tomato, still cling after death, but for uniformity 
we class as defoliation a killing of the leaves whether they 
actually drop off or not. 
Defoliated = practically all the leaves are killed. 
