CERCOSPORA. 513 



Cercospora. 



Conidia elongated and slender, olive-green, and septate. !My- 

 celium greenish. 



"Distinguished Ity the vermiform septate conidia" (Massee). 



Cercospora circumscissa Sacc.^ This is a parasite which 

 occurs on cultivated almond, peach, and nectarine, as well as 

 on wild Primus serotina in the United States. The leaves are 

 attacked while still young, and exhibit by reflected light a 

 yellowish spot with a dark centre. The conidia arise on the 

 spots as dark-green clusters, thereafter the diseased tissue shrinks, 

 becomes detached, and falls out, leaving " shot-holes " not 

 unlike those produced by species of Phyllostida. Defoliation 

 may occur in severe cases of attack. As a result of the 

 injury to the foliage, the new wood does not mature well, 

 and second growth may take place during the same season ; 

 shoots of this kind will probably dry up during winter. The 

 fungus may also directly kill the tissue of twigs as far as the 

 cambium. The fruit is never attacked directly, but may be 

 seriously affected through the injury to leaves or twigs. 



In order to minimize the disease, it is recommended to burn 

 all fallen foliage, and to turn the earth thoroughly below infected 

 trees. Pierce obtained a crown of very healthy foliage on almond- 

 trees treated with (1) ammoniacal solution of eojiper carltonate, 

 and (2) modified eau celeste. 



C. persicae Sacc. On leaves of peach. (U.S. America.) 



C. acerina Hartig- appears on brown spots on the cotyledons, 

 young leaves, and stalks of young plants of Acer. The conidia 

 are grey, pluricellular, and slightly curved (Fig. .j14). The 

 mycelium inhabits the intercellular spaces of the parts attacked, 

 and forms resting sclerotia in the tissues of dead leaves. 



C. viticola (Ces.).^ This fungus is found in Europe and the 

 United States on Vitis vinifcra and V. Lahriisca. It causes 

 spots on the leaves, and from these arise close columns of 

 septate conidiophores which give off thick pluricellular conidia. 



C. beticola Sacc.^ inflicts considerable injury on cultivated 



1 Pierce, Joun^al of Myrolor/t/, vii., p. 6fi and p. 232. 

 '^R. Hartig, Uvtermrhunijcn ajw d. forstbotan. Inatiliit, i., Municli. 

 =^ Description and treatment in New York Agric. Exper. Station Report for 

 1890, p. 324. 



^Thiimen, Die Behimpfuvq d. Pihkraid-heitcn tniatrer Kitllurtfeirdchae, 1886. 

 2k 



