THE MOSAIC DISEASE OF CUCURBITS. 63 
tions made by the writer from plants outside the Cucurbitacese have 
given negative results, but the large number of wild plants which 
show various types of chlorotic diseases makes the problem one which 
will require much inoculation work before final conclusions are 
justified. 
CONTROL MEASURES. 
All efforts to control the mosaic of cucurbits have dealt with 
cucumbers in the field and have been along three lines: (1) The 
removal of diseased plants as soon as they are detected, (2) the 
control of insects which spread the disease, and (3) the breeding of 
a cucumber which would be resistant to the mosaic disease. 
SANITARY MEASURES. 
The tests of sanitary measures were made during the season of 
1916, a considerable acreage of land being available for this pur- 
pose at Plymouth, Ind., Madison, Wis., and Big Rapids, Mich. The 
absence of the disease from all but one field at Big Eapids limited 
the work to a single plat of about one-third of an acre, where aphids 
from mosaic experiments escaped by accident and furnished a 
severe infection. The disease appeared in the outside row of the 
plat on July 28, the aphids being by that time well disseminated 
on the rows closely adjoining. All plants in this row were pulled 
and burned where they lay, the remainder of the field was sprayed 
with nicotine sulphate, and from that date to the end of the season 
plants in the plat were inspected daily and all those suspected of 
mosaic were removed and destroyed. Once started, however, the 
disease continued to increase, and by August 25 the number of 
plants had been reduced about 50 per cent. The removal of dis- 
eased vines after they had become intertwined with healthy plants 
resulted in contact infection of those adjacent and served to increase 
rather than diminish the disease. 
The work at Madison, Wis., was under the direction of Dr. M. W. 
Gardner during 1916 and included a large acreage of cucumbers. 
The disease developed rapidly after its first appearance, due prob- 
ably to the presence of an abnormal number of cucumber insects, 
and attempts at removing all mosaic plants soon become hopeless, 
many fields being practically ruined by August 9. Similar results 
were secured in the experiments at Plymouth, Ind., which were 
conducted by Dr. George A. Osner. 
The fact that diseased plants are a source of infection before 
definite symptoms appear, which had not been proved at that time, 
adds to the difficulty of control by sanitary measures. While the 
eradication method is theoretically sound, the practical conditions in 
the field are such that, except for use early in the season and in 
the case of slight infections in isolated fields, this method affords 
little hope of success in stopping the progress of the disease. 
