WORK ON Till-: WIllTK I’lNK I’.USTKR ROST IN MINNESOTA 
9 
two to six years, or possilily loiij^er, hence, its occurrence in an}' state is 
no retiection u])on the work of ins])ection officials or plant jiatholo.ii^ists. 
The bodies producing- teliospores looking like tiny threads less than 
one-riuarter inch long, grow in clusters on the underside of the leaf and 
are easily visible with a lense. A tree attacked by these spores after a 
time exhibits a swelling of the bark at the diseased portion, generally 
losing its natural green color. \Try early in the spring, and fretjuently 
at other seasons a clear liquid exudes in drops from this discolored 
bark. This liquid contains microscopic spores known as “pycnospores,” 
the function of which is not readily understood. The appearance of 
these drops generally precede the appearance of the blisters. 
After the peridermium spores are discharged from the blisters on 
the pines, said blisters remain as open cavities and the bark in the vicin- 
ity dies, exhibiting later a cracked and discolored appearance and show- 
ing evidence of a cancerous growth. The region about the blister may 
in fact exhibit “canker” of some sort during the period of s])ore dis- 
charge or before. This was clearly evident in the case of our first find- 
ing in Nursery B. If the tree is not killed immediately by the attack, 
and a large tree may not be, it may give off spores every year there- 
after to infect currants and gooseberries in the vicinity. It is not 
known that spores live over winter on currant and gooseberry ; so 
far most of the evidence would indicate the contrary. It has been 
generally supposed that if all currants and gooseberries within a 
radius of 1,500 feet from an infested j)ine or pines were destroyed, 
the danger of the infection spreading would be eliminated, but this 
year’s observations indicate that this is possibly an unsafe assertion. 
The life history of this parasitic fungus has been given very 
briefly, but we believe sufficient data have been presented to make it 
clear what a difficult problem is before us, if we wish to eradicate it in 
Minnesota, and how impossible the solution of this problem is unless 
neighboring states offer efficient co-operation for their own protection, 
as well as for the protection of this state. 
WORK DURING THE SUMMER AND AUTUMN OF 1916. 
Immediately upon the discovery of the rust in the two nurseries 
above referred to, the State Entomologist, by the authority invested in 
his office, imposed a quarantine forbidding the sale and shipment of 
any five-leaf pines, currants and gooseberries from either of the above 
nurseries until the rust had been eradicated therefrom. Acting upon 
the advice of the Division of Plant Pathology of the Experiment Sta- 
tion and the Entomologist, owners of these nurseries voluntarily de- 
stroyed all pines known by them or suspected by them to be infected. 
