BLACKBERRY DISEASES 163 
infected, show little external indication of disease. It has been 
observed that affected plants are freer from prickles than normal 
plants. Healthy and diseased canes may be found in the same 
stool. All affected canes should be destroyed. The same dis- 
ease also occurs on raspberries (see fuller discussion, page 399). 
DovusLe-BLossom 
Caused by Fusarium Rubi Winter 
This is primarily a disease of the dewberry, although the cul- 
tivated blackberry is affected. The trouble occurs to some ex- 
tent on the high-bush blackberry. Among the dewberries the 
Lucretia and Rathbone are notably susceptible, while the Black 
Diamond and other varieties are less liable to attack. 
Double-blossom is most common in the Delaware-Maryland 
peninsula. It has been observed, however, in Illinois, Tennessee, 
Texas, New Jersey, North Carolina and Alabama. The first 
record of the disease comes from Illinois about 1885, although 
the important writings on the subject of double-blossom are 
recent. 
The history of the disease shows that it does not vary in 
abundance in a given region from year to year. But, as would 
be expected, it continues to increase in severity until affected 
plants are worthless. If diseased plants are allowed to go un- 
treated, their life is shortened by two or more years. In the 
Delaware-Maryland peninsula double-blossom has been so se- - 
vere on Lucretias that half of the growers have discontinued 
dewberry culture. 
Symptoms. 
Evidences of double-blossom appear early in the spring just 
as the leaf-buds are opening. The trouble may be detected 
previous to this by the enlargement of the diseased buds. When 
affected leaf-buds open there is produced, in place of normal 
leaves and shoots, a witches’-broom. This abnormal develop- 
