Mar. 19,1917 
Dissemination of Angular Leafspot of Cotton 
465 
caged in the greenhouse, with cheesecloth stretched over wooden frames. 
Into one of these cages were placed 50 jassids caught in the early morn¬ 
ing while the dew was on the plants; into another, 75 jassids caught 
about 9 a. m., after the dew had evaporated. Two cages were used as 
umnoculated controls, while the plant in the fifth cage was sprayed 
with a water suspension of a 6-day-old 1 per cent saccharose agar slant 
culture of Bacterium malvacearum. After the insects had been upon 
the plants for 18 days in one instance and 14 days in the other and after 
the inoculated control had developed for 11 days the cages were opened 
and observations made. The results are given in Table II. 
Table II. —Results of a greenhouse experiment to determine the agency of insects in the 
dissemination of angular leafspot 
Test. 
Number of 
leaves not 
infected. 
Number of leaves 
infected. 
Jassids caught in dew (18 days). 
58 
58 
132 
124 
99 
I (1 spot?). 
0 
Control. 
Jassids caught dry (14 days). 
0 
Control. 
0 
Inoculated control. 
22 (871 Spots). 
While the data are not conclusive as to the activities of these insects 
the conclusion that they have a very slight effect, if any at all, is sup¬ 
ported by the later developments in the same patch used for seed- 
infection studies and described above. 
Shortly after September 1 this field was chopped to a close stand and 
the plants allowed to develop. There was considerable angular leaf- 
spot present upon the plants in the adjoining fields, and an excellent 
opportunity was presented for the insects to demonstrate their influ¬ 
ence upon the spread of the disease, since the growing plants were at a 
favorably susceptible age. A careful examination was made of this 
field on October 2, particularly of those plots lying next to the older 
cotton. Table III shows the amount of disease present, the data being 
presented in rows per plot. Those of the first five plots were parallel 
to the rows of the adjacent cotton field, the seventh row being slightly 
over 21 feet away, while the remaining plots were bordering the cotton 
on another side of the triangle, with the rows running toward the other 
field, so that no idea of distance can be had. The numbers of the plots 
are identical with those in Table II, which facilitates comparison. 
