Diseases of Plants

Abstract

DR. G. H. PETHYBRIDGE, economic botanist to the Department of Agriculture and Technical Instruction for Ireland, has recently published two papers, of considerable scientific as well as economic interest, on species of the genus Phytophthora, and the diseases which these fungi cause in the potato. In the first paper (Sci. Proc. Royal Dublin Soc., vol. xiii., No. 35) he describes the rotting of potato tubers by a species of Phytophthora having a method of sexual reproduction hitherto undescribed, and gives in the introductory portion of the paper a useful summary of the literature dealing with the chief forms of rot previously known to occur in the potato tuber. The new form of rot (“pink rot”) is caused by the new fungus Phytophthora erythroseptica, the most peculiar feature of which is the fact that the oogonium rudiment enters the antheridium at or near its base, the female organ then growing up through the male and out at the top, expanding there to form the oogonium proper in which the oosphere develops. The “pink rot” disease is prevalent in the west of Ireland, and the losses caused by it, which are considerable, and in some cases being greater than those due to P. infestans, are greatest in crops grown continuously on the same land (infection taking place from the soil), and can be avoided by a proper rotation; it is probably transmitted to some extent by oospores which adhere to the seed tubers.