July 15, 1920 Relative Susceptibility to Citrus-Canker 341 



SUSCEPTIBILITY OF NONRUTACEOUS PLANTS 



Melia azedarach L., China berry, in field, 1919. 



Inoculations were attempted on this plant in the field for the reason that it is the 

 native host of the Citrus white fly. Needle prick and spray inoculations in the field 

 under the most favorable conditions for the development of canker were negative. 



Lee and Merrill (5) have reported successful inoculations of the stem and petioles 

 of Lansium domesticum with Pseudomonas citri. This plant belongs to the same 

 family as the China berry. 



SUSCEPTIBILITY OF WILD RELATIVES OF THE GENUS CITRUS 



RUTACEOUS PLANTS NOT CLOSELY RELATED TO THE GENUS CITRUS 



Xanthoxylum sp. (CPB 11269, seedling), III.' 



So far no canker spots have been found on the plants. 

 Casimiroa edulis Lav. and Lex. White sapote (CPB 7923, seedlings), I, 11,2 -^ field, 



1919.^ 



At the October, 1918, readings a few nontypical spots were observed on several of 

 the young leaves of the plant in experiment I. They occurred only at the woimds 

 and scratches, no spots being found on the xmbroken surface of the leaves. New 

 spots have appeared from time to time, but in all cases they have occurred at wounds 

 and remained unruptured. The spots (PI. 57) are small (about 0.5 mm. in diameter), 

 light colored, slightly raised, compact, and unruptiu-ed. They do not have an oily 

 outline. No yellow zone is present. No positive infections were obtained in the field. 



As there are three varieties of the white sapote being grown in California and Florida 

 for its fruit, it is of interest to note that it can be successfully inoculated imder green- 

 house conditions, although it does show considerable resistance to citrus-canker. 

 Glycosmis pentaphylla DC. (CPB 2905, seedlings), II, 111,2 in field, 1918. 



This is one of the few relatives tested which has, so far, remained immime to canker 

 in both the greenhouse and field. 

 Claucena lansium Skeels. Wampi (CPB 7936, seedlings), 1, 11,2 i„ fi^jfj^ j^^^ ^^^ ^^^g^ 



A few small, nontypical, oily spots appeared on the leaves of the plants in both 

 experiments. The spots are typical of those found on the wild relatives. Repeated 

 inoculations in the field gave negative results. 

 Chalcas exotica Millsp. {Murraea exotica L.)- Orange jessamine (CPB 797SA, 



seedlings), I, II, in field, 1917 and 1918. 



Diuing July, 1918, a few nontypical spots were observed on the young leaves of the 

 plants in experiment II. 



The spots resemble those on Casimiroa edulis in general appearance, except that 

 they are somewhat larger and of a more oily character. A few new spots have devel- 

 oped since that time. The plants are only very weakly positive, and the period of 

 incubation is rather long. The spots in all cases were at wounds and imruptured. 

 In no case were positive results obtained in the field in spite of repeated inoculations. 



RUTACEOUS PLANTS BELONGING TO TRIBE CITREAE 



SuBTKiBE Aegunau (Hardshell Fruits) 



Aegle marmelos Correa. Bael fruit (CPB 7983, seedlings), ly II, in field, 1918. 

 Diu-ing the summer months these plants made a splendid growth and produced an 

 abundance of new foliage. At the July, 1918, reading several small spots typical of 



' Roman numerals refer to the number of the inoculation experiment in the greenhouse. 

 ' Included in experiments of March 21, 1918. 

 ' Date of planting in the isolation field. 



