13S0 DISEASES OF \'ARIOUS CROPS 



the fruit. The tissue of the rind then softens and shrinks, the pulp becom- 

 ing black and gelatinous. 



The writer was able to isolate and cultivate the pathogenic agent. It 

 consists of a species as yet unidentified, belonging to the genus Diplodia ; 

 the diagnosis was confirmed by the entirely positix^e results of a series of 

 artificial inoculations. 



The fungus has separate or adjacent pycnidia, which may or may not 

 be covered with a network of hyphae from 180 to 250 [x in diameter ; the 

 spores are oval, 24-30 X 10-14 V-' brownish-black and segmented. In the 

 matter extracted from artificially inoculated melons the presence of para- 

 physes was not observed ; the latter developed on cultivating the fungus 

 on cylinders of potato. 



In the United States the principal crops attacked by Diplodia are the 

 sweet potato, Citrus fruits, maize and the cotton tree. As, in the South, cot- 

 ton fields, sweet potato and melon fields are not separated from each other, 

 it was of interest from the economic point of view to ascertain whether a 

 .species of Diplodia found on the one host is capable of development on an- 

 other also. Experiments in this direction yielded positive results : a cul- 

 ture of D. t liber icola E. et E., inoculated into healthy melons produced 

 a series of symptoms identical with those described above. 



1037 - Sclerotinia libertiana, a Disease of Citrus and Other Plants Cultivated 

 in California. — Smith O. Clayton, in Pliytopatholoi,y, Vol. 6, No. 3, pp. 268-278. Fig. 5, 

 Baltimore, Md., 1916. 



The citrus disease known under the name of " white mould" or " cot- 

 tony rot " is very frequent in California, in storage places of citrus fruits 

 during the period January to March. Besides the fruits of the lemon tree, 

 it also attacks the small branches of orange trees and lemon trees 

 in the plantation, and likemse, but more rarely, the flowers of the lemon 

 tree. The pathogenic agent is supposed to be Sclerotinia Libertiana Fuckel. 

 The pathological changes observed on the fruits is characterised externalh- 

 by an abundant white growth of mycelium of cottony appearance, and inter- 

 nally by a progressive softening which converts the tissues into a soft mass. 

 The disease spreads rapidly, and all the lemons contained in one case are 

 soon infested, and form a dangerous centre of infection in the store house. 

 The bark of the small branches of the plants growing in the open air or 

 under glass becomes ashy in colour and fibrous in consistency, and gum ex- 

 udes plentifully all around the infected plant. 5c/. Libertiana can likewise 

 develop in the flowers, where excellent conditions are available in the thick 

 mass of the petals at the beginning of flowering. 



This fungus not only attacks Citrus spp. but also the flowers of the apri- 

 cot, the small branches of the alligator pear tree {Persea gratissiiiui), cucum- 

 ber, tomatoes, vetches, lettuce, nettles, egg-plants, etc. 



The practice prevailing in California of sowing vetches in citrus planta- 

 tions mu.st have contributed greatly to the spread of the disease. 



It is also easy to produce artificial infection of the disease on lemons in 

 a wet environment, by means of applications or inoculations of mycelium, 

 sclerotia, spores or fragments of apothecia of the fungus. In this respect 



