50 BULLETIN 879, IT. S. DEPARTMENT OE AGRICULTURE. 
Hamilton, Midi., 1916.— The same plat was used in 1916 and 30 
cages set out on July 10, covering 60 plants. The uncaged plants 
became affected early in the season and on August 22 each of them 
showed the disease in severe form. The caged vines had grown so 
rapidlv that it was necessary to remove the cages at this time, and it 
was found that all had remained healthy. 
Big Bapids, Mich., 1916. — A test similar to that at Hamilton was 
conducted at Big Kapids, Mich., on a quarter-acre plat that had 
been badly diseased the previous year. Thirty-five cages were put 
down on June 20, five on June 29, and five on July 7. However, the 
disease was not severe in the uncaged portions of the field, and only 
10 per cent of the plants were found to have mosaic at the end of the 
season, so that the results were not as conclusive as in the other tests. 
All caged plants remained healthy throughout the season. 
Madison, Wis., 1917. — In 1917 the work was transferred to Madi- 
son, Wis, and the experiment was repeated on a f-acre plat where all 
plants had mosaic in 1916. 
The cages in this case were set out on June 26, as soon as the seeds 
germinated, 18 cages being used, covering 36 plants. Beetles were 
present in the field in great numbers after July 10, and a few 
appeared in some of the cages after a heavy rain which had washed 
the earth away from the edges of the cages. The plants in these 
cages were removed on July 9 and new seed planted. The cages 
were watched carefully; no more insects appeared until August 18, 
when beetles were found working in nearly every cage, but as there 
seemed to be no means of entry from the outside it was suggested 
by entomologists who were consulted that they were from the second 
brood and had emerged from the soil. No effort was made to 
remove them, and the cages were left until September 13. The 
uncaged plants had been very badly infected with mosaic early in 
the season, 25 per cent of the plants developing the disease within 
five days after July 19, when the first cases of mosaic were found. 
By September 13, when all the uncaged plants had been infected 
for some time and the vines were much stunted, the caged plants 
still appeared perfectly healthy and normal with the exception of 
injuries from the beetles noted above. (PL IX, B.) 
During the same season an additional test was earned on in a small 
garden belonging to the department of plant pathology. Here 12 
cages were used to cover 24 vines which were transplanted from the 
greenhouse early in June. Fifty additional plants were transplanted 
near by and 100 more were grown from seed, both lots being left 
uncaged. All the uncaged vines became diseased by August 20, and 
when the cages were removed on August 29 all the caged plants 
proved perfectly normal and healthy. 
