22, 6 Lee: A Disease of Orange Fruits 609 



G. foliicolum but as work that may be of assistance to a later 

 investigator. 



The Japanese fungus on mandarin and Unshiu oranges. — The 

 Japanese disease in the field has been confined entirely to fruits 

 of the Wase Unshiu variety and no cases were observed upon 

 other species such as the sweet orange, Citrus sinensis; the 

 lemon, Citrus limonia; the pummelo, Citrus maxima; or the 

 sour orange, Citrus aurantium. Trees of the five other recog- 

 nized varieties of the Unshiu orange commercially grown in 

 Japan in many cases were observed in the same orchards, side 

 by side with trees of the Wase variety; nevertheless, none of 

 the Wase rot was ever observed upon such other varieties. The 

 Wase Unshiu variety is an early-bearing variety; in fact, a 

 translation of the Japanese word Wase is early. Fruits of the 

 Wase variety mature during the summer heat of early September, 

 while the other varieties mature in late October, November, or 

 even December when the temperature is 30 to 40° F. lower. 



Inoculations made in the field upon immature fruits of the 

 Zairai, Ikeda, and Ikiriki varieties resulted entirely negatively 

 in early October, while identical inoculations upon the Wase 

 variety resulted positively. Later inoculations were made upon 

 mature Zairai fruits removed from the trees and held in an 

 incubator at 26 to 28° C. These resulted positively in two out of 

 ten cases in the first test and in one out of ten cases in the second 

 series. Inoculations upon fruits of the Ikiriki Unshiu orange 

 under the same conditions resulted in one positive case from a 

 total of ten fruits, and in the second series in seven cases from 

 a total of ten fruits. It seems reasonable to conclude from this, 

 therefore, that the lower temperatures at the time of maturing 

 of the Ikiriki and Zairai Unshiu varieties limit the disease on 

 these varieties, and that the occurrence of the disease in the 

 field on the Wase variety alone is not a host restriction but 

 a temperature limitation. 



A series of inoculations upon Wase Unshiu fruits as compared 

 with inoculations upon Batangas (Philippine) mandarin oranges, 

 resulted in 65 per cent positive cases from twenty Wase Unshiu 

 orange fruits and 55 per cent positive cases from twenty Batan- 

 gas mandarin orange fruits. The Batangas mandarin orange a 

 form of C. nobilis var. deliciosa, was therefore readily susceptible 

 to this disease; apparently then the Japanese fungus is capable 

 of infecting mature fruits of either the Unshiu or the mandarin 

 oranges if temperature conditions are favorable. 



