Jan. io, 1914 
Some Diseases of Pecans 
335 
roughened and darker in color and the interior tissues are then more or 
less distorted and hardened. Often the interior assumes a distinctly 
woody texture, and a roughened bark develops over the surface to form 
the “hard-gall” type. With the development of roots from the tumor 
tissue the “ hairy-root ” type appears, but this form has not been ob¬ 
served on the pecan. 
EXPERIMENTS WITH THE CROWN-GAEE ORGANISM 
Soft galls from the Mississippi nursery (December, 1909) were left for 
five minutes in a solution of corrosive sublimate (1 *.500) and washed in 
sterile distilled water. Small pieces of the abnormal tissue were then 
removed under aseptic conditions from points just under the surface and 
near the edge of the galls, and beef-agar cultures started by the ordinary 
poured-plate method. In from three to eight days the circular and some¬ 
what opalescent colonies of the organism appeared, but were much more 
abundant in cultures started from the extreme base of the young soft galls 
near the juncture between the diseased and healthy tissues. Transfers 
were made to beef-agar slant tubes, and with one of the strains thus 
obtained the following inoculation tests were made. 
Experiment No. i (December, 1910).—Six table beets were inoculated by needle 
punctures from young beef-agar cultures of the bacteria, while a like number of beets 
were punctured with sterile needles and held as checks. 
After five weeks, examination of the inoculated beets showed the development of 
typical galls, 3 to 10 mm. in diameter, at most of the needle punctures, while the 
checks showed no signs of infection. 
Experiment No. 2 (Jan. 12, 1911).— Four potted pecan seedlings were inoculated 
by scalpel punctures at the crown from 4-day-old beef-agar cultures, and the soil was 
replaced around the base of the tree to preserve the moist condition. Four other 
seedlings were treated in the same manner, except that no bacteria were introduced. 
The trees were all dormant at this time and remained in this condition until the 
latter part of March, when, with the exception of one of the inoculated trees which 
died from other causes, all pushed out their foliage in the normal manner. 
Examination in June showed a tumor several millimeters in diameter at the crown 
of one of the inoculated trees and an apparently incipient infection on a second. All 
the other trees had completely healed over, so that the location of the punctures 
could scarcely be made out. On September 12, eight months after inoculation, 
well-developed galls were found at the crown of two out of the three remaining 
inoculated trees. The check trees, together with 59 other pecan seedlings in the 
same greenhouse, showed no indications of the disease. 
Since these brief studies with the parasitic organism were carried out 
merely to indicate the connection of this disease of the pecan with the 
well-known crown-gall, no further inoculation and cultural tests were 
made. However, cultures of the bacterium were submitted to Dr. 
Erwin F. Smith, of the Bureau of Plant Industry, who obtained similar 
results in inoculation experiments and further verified the identity of 
the organism with Bacterium tumefaciens Sm. and Town., the cause of 
crown-gall of plants. 
