50 FUNGOID PESTS OF CULTIVATED PLANTS. 



Although the powdery mildew (Microsphceria Ehrenbergii) has been 

 found on Honeysuckle leaves on the Continent, we have no record of it in 

 Britain. 



PESTS OF COMPOSITE PLANTS. 



It seerns rather remarkable that so large an order of plants as the 

 Composites, containing many garden flowers, should be so conspicuously 

 free from the atttacks of fungoid parasites. Who shall explain wherefore 

 Puccinia Helianthi (Schum.), which is so universal in North America on 

 Sunflower and Jerusalem Artichoke, has never made its appearance in 

 this country, although it has been reported in Europe ? Why are Dahlias 

 so impervious to attack, and a host of smaller annuals, Asters, Coreopsis, 

 Marguerites, and the plebeian Marigold, go almost free ? Even the 

 cultivated Cineraria, which is popular enough in all conscience, has never 

 received a check in this country, although it has been threatened abroad. 



CHKYSANTHEMUM LEAF-SPOT. 



It will be well to be guarded against the occurrence of leaf -spot on 

 Chrysanthemums, as some three or four exotic species are already known. 



The purple spot (Phyllosticta Chrysanthemi), with small simple 

 sporules (4-5 X 2|-3 p), has up to the present been found only in 

 Canada. 



The ringed brown spot (Septoria Chrysanthemi), with long thread- 

 like sporules (55-65 p. long), has apparently been confined to Italy. This 

 is the most essential to be watched of all, since it is European. 



The black spot (Cylindrosporium Chrysanthemi) is very destructive 

 in Canada, and has large, sooty, indefinite spots, with f usoid conidia 

 (50-100 x 3-4f /i). When the leaves are attacked they soon turn yellow 

 and shrivel, and the flower buds do not expand. 



Mass. PL Dis. 292. 



CHRYSANTHEMUM OIDIUM. 

 Oidium Chrysanthemi (Rabh.), PL III. fig. 58. 



This effused white mould is found on the leaves of Chrysanthemum, 

 but fortunately it has not hitherto been sufficiently common to cause alarm. 



The thin white mealy patches are without definite form, and consist 

 of a creeping mycelium from which the fertile threads arise. These are 

 at first just like simple threads, with cross divisions, separating them into 

 joints ; but at length the upper joint enlarges and becomes elliptical, and 

 when mature falls away as a conidium or sporule, capable of germination, 

 to be followed by the next joint and the next, and so on in succession until 

 a large number of conidia are produced and thrown off, as in other species 

 of Oidium. The conidia are rather large (40-50 x 20-25 p) as compared 

 with other species. 



It may be assumed that such remedies as are successful with Oidium 

 Tuckeri on the vine would be applicable here, and of these the application 

 of sulphur is most to be commended. 



The above-named mould appeared in this country for the first time 

 in 1884, and is known also in France and Germany. 



Sacc. Syll iv. 199 ; Gard. Chron. Nov. 29, 1884, fig. 118; Ib. 1901, 

 p. 351. 



