DISEASES OF PLANTS. 549 



The simplest means of prevention is first disinfection, and second the main- 

 tenance of absolute dryness in the grains, which requires exclusion of insects 

 therefi'om and frequent heating. 



Rust of fruit trees, A. Desmoulins {Prog. Agr. et yu. {Ed. VEst-Centre), 

 S6 {1915), No. 11, pp. 253-255). — Giving results of recent observations and tests 

 on Coryneum rust of peach, apricot, and cherry in the Rhone Valley, the author 

 describes a treatment with Bordeaux mixture rendered adhesive by the addi- 

 tion of molasses (1 kg. per hectoliter). This is said to have proved effective 

 and practical. 



Influence of atmospheric conditions on the appearance of downy mildew, 

 J. Capus {Prog. Agr. et Vit. {Ed. VEst-Centre), 36 {1915), Xo. 9, pp. 19S-200).— 

 The author gives the results of observations covering several years on the rela- 

 tions between atmospheric conditions and the two early developmental phases 

 of downy mildew. 



Infection (penetration of the tissues by the germinative tubes from zoospores) 

 occurs only following precipitation, which may be as small as 1 mm. Contami- 

 nation (passing out of the stage within which copper fungicides can destroy the 

 fungus) may follow infection immediately, or it may be delayed for several 

 days by unfavorable conditions, such as cold, or by precipitation, which appears 

 to prolong the period during which spraying is effective. The primary invasion 

 or attack is that which first appears in spring (originating in overwintered 

 material), while secondary outbreaks are due to conidia formed as the result 

 of primary or later outbreaks. 



It is found to be an unsafe practice to spray early and then await the ap- 

 pearance of the mildew on the newly developed (and hence unsprayed) leaves, 

 to make a second application. In case of both primary and secondary outbreak, 

 the treatment becomes ineffective within a day or two after a rain. 



Oidium of oak and grape, L. Ravaz {Prog. Agr. et Vit. {Ed. VEst-Centre), 86 

 {1915), No. If, pp. 86-89). — Giving a brief resume of some observations on 

 Oidium of oak and of grape by Pantanelli, the author directs attention to some 

 preferences and habits noted in regard to portions attacked as regards age of 

 parts exposed, structure, cell content, turgescence, and nutrition. 



Report of the plant pathologist, G. L. Fawcett {Porto Rico Sta. Rpt. 1914, 

 pp. 27-30). — ^An outline is given of work in progress, which included testing 

 various forms of Bordeaux mixture and some studies on diseases of coffee, 

 cacao, and citrus trees. 



The experiments with fungicides show that homemade Bordeaux mixture, if 

 properly prepared, is cheaper and as eflBcient as any of the proprietary forms 

 tested. 



Among the coffee diseases reported upon, experiments were carried on to 

 test the relative resistance of different varieties of coffee to the fungi StUbeUa 

 flavida and PeUicularia koleroga. Some difference in susceptibility to these 

 fungi was noticed on the part of diffei'ent varieties, although complete resistance 

 was not observed. 



Notes are given of a new fungus disease of cacao, which is believed to be due to 

 a species of Corticium which has not yet been definitely determined. In addition 

 to occurring on cacao, the fungus also attacks and kills coffee tree branches 

 and has been found parasitic on grapefruit branches, although in the latter 

 case it is thought to have been associated with the presence of a wild vine grow- 

 ing over the tree. Attention is called to the fact that Phtjtophthora faberi, the 

 cause of black rot in the pods of cacao, has never been found in Porto Rico, but 

 that Spicaria {Fusariiim) colorans has been iso ated from diseased tissues. 



The author briefly calls attention to the bla k rot of citrus fruits due to 

 Diplodia natalensis. 



