Aerial Galls of the Mesquite

Abstract

During Work upon a plant disease survey in the vicinity of San Antonio, Texas,l my attention was called to the frequent occurrence of galls upon the twigs and branches oif the mesquite (Prosopis glandulosa Torr.). following quotation is from the publication dealing with the survey mentioned: The large limbs and smaller branches of the mesquite sometimes show abnormal enlargements which are frequently globular or sometimes elongated and sometimes greatly exceed the diameter of the branch on which they are produced. (Plate XV, figs. 2 and 3.) Specimens have been obtained ranging from I to 8 or IO inches in diameter. gall is produced by an abnormal growth of the wood, and cross sections of galls always show small brown specks where the wood cells are more or less disintegrated. are distributed throughout the entire woody region. These galls are not of insect origin, and cultural work attempted has as yet failed to connect either bacteria or fungi with the disease, although both have been obtained. crown-gall organism, Bacterium tumefaciens Erw. Sm. & Townsend was strongly suspected of being the cause of the galls, but at the time of writing the bulletin referred to the authors had obtained no direct evidence of such causal relation. No opportunity was afforded for detailed work on this subject, but Dr. Erwin F. Smith, of the Bureau of Plant Industry, very kindly furnished some cultures of B. tumefaciens which were used with the class in plant pathology in making some inoculations on the mesquite. inoculations were all made on a large tree growing under natural conditions on the campus of the University of Texas. A