OVERWINTERING OF THE CITRUS-CANKER ORGANISM 
IN THE BARK TISSUE OF HARDY CITRUS HYBRIDS 1 
COOPERATIVE INVESTIGATIONS BETWEEN THE DEPARTMENT OF PLANT PATH¬ 
OLOGY, ALABAMA AGRICULTURAL EXPERIMENT STATION, AND THE OFFICE OF 
CROP PHYSIOLOGY AND BREEDING INVESTIGATIONS, BUREAU OF PLANT INDUS¬ 
TRY, UNITED STATES DEPARTMENT OF AGRICULTURE 
By GEORGE L. PELTIER, Plant Pathologist , Alabama Agricultural Experiment Station t 
and David C. Neal, Pathologisty Bureau of Plant Industry, United States Department 
of Agriculture 
During the course of our field inoculation experiments conducted in 
southern Alabama in the fall of 1917 to determine the resistance and 
susceptibility to Citrus-canker of some of the wild relatives, Citrus 
fruits, and the more common hybrids of the genus Citrus, a most inter¬ 
esting feature has recently developed in connection with the ability of 
the organism to survive the winter in the outer bark tissue of some of 
these plants. 
All the plants were set in the isolation field in July, 1917, extreme 
precautions surrounding the experiments being maintained. By the 
middle of September they had made a rapid growth and were at that 
time in fine shape for inoculation. 
Included in a series of inoculations made on September 16, 1917, 
were the hybrids Rusk citrange (CPB 795 6A), 2 Savage citrange (CPB 
7961), and citrandarin (CPB 40175A), and two plants each of Poncirus 
trifoliata, grapefruit ( Citrus grandis), and Satsuma orange (1 Citrus nobilis 
var. unshiu. In making the inoculations 100 cc. of a 48-hour culture of 
Pseudomonas citri in beef bouillon were thoroughly sprayed on each plant 
by means of an atomizer. 
Although repeated observations were made during October and Novem¬ 
ber of the plants enumerated above, only P. trifoliata and grapefruit 
showed any evidence of canker infection, and this only occurred to a slight 
extent on the foliage. It was thought that absence of infection on the 
Rusk and Savage citranges, as well as on the citrandarin and other 
plants, could be in part accounted for by the unfavorable temperature 
prevailing at the time the inoculations were made. This view was also 
somewhat strengthened by the fact that the more susceptible plants, 
such as grapefruit and P. trifoliata revealed only a minimum amount of 
infection two months after making the inoculations. With such unfa¬ 
vorable temperatures prevailing because of the lateness of the season 
no positive results were obtained with the hybrids, particularly with the 
citranges and citrandarins. 
1 Published with the approval of the Director of the Alabama Agricultural Experiment Station. 
* CPB—Crop Physiology and Breeding Investigations. 
Journal of Agricultural Research, 
Washington, D. C., 
PC 
Vol. XIV, No. ix 
Sept. 9,1918 
Key No. Ala.-< 
(S 2 3> 
