394 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Citrus Canker in South Africa. By Ethel M. Doidge {Dep. Agr. U. S. Africa, 

 20, 1916, pp. 3-8 ; 8 plates). — A bulletin for Citrus-growers pointing out the 

 serious disease of canker, and its importance to the Citrus industry. 



Recognized in Florida as late as July 191 2 as a serious pest imported from 

 Japan. 



Spraying tests were a complete failure in U.S.A., and fire was resorted to — 

 tree, grass, and soil underneath tree being completely charred by a naming 

 spray. 



Imported into S. Africa on Grape Fruit in 1905 from Florida, and spread 

 rapidly through the imported tree orchwd in the wet summer of 1908-9. All 

 diseased fruit and wood burnt, and every tree sprayed five times with ammoniacal 

 solution of copper carbonate, but this did not arrest it. In January 1910 the trees 

 were pruned and prunings burnt, and Bordeaux mixture 4-4-50 was used three 

 times, which checked the disease, and the trees free until 1916, when a few Grape 

 Fruit were slightly marked with canker, which affects the leaves, twigs, larger 

 branches, and fruit. Spraying with Bordeaux mixture is recommended, except 

 where badly infected nursery stock is attacked, and then burning is the best 

 remedy. — G. F. W. 



Citrus Canker, Susceptibility and Resistance of Various Species of Citrus to. 



By Geo. L. Peltier (Jour. Agr. Res. vol. xiv. No. 9, August 1918; pp. 337-358, 

 4 plates). — Many plants, including the more important wild relatives, species, 

 varieties, and hybrids of citrus, were inoculated with Pseudomonas citri in order 

 to test what was their degree of susceptibility and resistance to Citrus canker. 

 The conditions were such that the maximum amount of infection was possible, 

 and included high temperature, much humidity, and a rapid and vigorous 

 growing plant. It was found that Poncitrus, Fortunella, Eremo citrus, Citrus, 

 and Microcitrus were susceptible, though plants of the genera Fortunella, 

 Eremocitrus, and Microcitrus show some resistance to the canker. Citrus nobilis, 

 with its many varieties and types, the Kansu orange, and possibly C. mitis, show 

 resistance to the disease, but all are nevertheless susceptible to it. Of the hybrids 

 the citrangequat and the citranguma remained free from the canker in 

 these tests, while the citrandrins, limequats, and tangelos showed some 

 resistance. The citranges, with the possible exceptions of Willits, cicitranges, 

 citrumelos, and limelos, are all extremely susceptible to the disease. 



The relative susceptibility and resistance of the plants were judged by the 

 number, size, and character of the spots on the leaves. — A. B. 



Citrus Canker, Susceptibility of Rutaceous Plants to. By H. A. Lee (U.S.A. 

 Jour. Agr. Res. xv. No. 12, Dec. 1918 ; pp. 661-666; 4 plates). — Inoculation 

 tests with Pseudomonas Citri upon twenty-four species of Rutaceae show that 

 nineteen of these are more or less susceptible. The canker is therefore by no 

 means restricted to the genus Citrus, but has many hosts amongst the Rutaceae. 



Severinia buxifolia, Aegle Marmelos, Balsamo citrus gabonensis are immune 

 to Citrus canker. Chalcas (Murray a) exotica, Atalantia disticha and Fortunella 

 (Citrus) japonica are strongly resistant to the canker, but Claucena lansium, 

 Feronia limonia, Feroniella lucida, Chaetospermum glutinosa, Hesperethusa 

 crenulata, Paramignya longipedunculata, Citropsis Schweinfurthii, Atalantia 

 citrioides, and others produce positive results when inoculated with Pseudo- 

 monas citri. 



Chaetospermum glutinosa show naturally occurring infections of the Citrus 

 canker, and in the Philippines its susceptibility is much greater than that of 

 the sweet orange (Citrus sinensis). The occurrence of natural cankers on these 

 trees suggests that this species may have been an original wild host from 

 which Citrus canker has spread to cultivated species. — A . B. 



Citrus Fertilization Experiments. By C. F. Kinman (U.S.A. Dep. Asr., Porto 

 Rico Exp. Stn., Bull. 18, May 1915 ; plates). — No available records of manurial 

 experiments existed either in Porto Rico or in American orchards. An arbitrary 

 formula had therefore to be chosen for the standard mixture, and results checked 

 by varying the number and proportions of the ingredients in neighbouring plots. 

 The original basic formula was : 



0-775 lb. phosphoric acid, 

 o*666 lb. nitrogen, 

 0-516 lb. potash, 



per tree annually. 



This was afterwards modified. 



The basic formula for the application since given allows 1 if lb. a tree yearly 



