422 Diseases of Economic Plants 



DAISY 



Crown-gall (Pseudomonas) does but slight injury. 



DRAC^NA 



Leaf-Spot (Phyllosticta maculicola Hal.). — This may be 

 recognized as small, brown, somewhat angular spots on the 

 leaves, each spot siu'rounded by a rather wide yellow border. 

 Minute pycnidia are present. 



FERNS 



Blight (Phyllosticta pteridis Hal.). — The tender growing 

 tips of ferns are subject to blight, and blighted spots may also 

 occur lower upon the leaf. The brown dead tips and leaf 

 spots bear minute pycnidia. Blighted parts should be cut 

 away and burned and the remaining foliage sprayed with 

 Bordeaux mixture. The disease is strictly local, and close 

 attention will stop its spread, even after it has considerable 

 foothold. Numerous other fungi are recorded on various 

 species of ferns, chiefly causing leaf-spots. 



Prothallium-blight (Completoria coniplens Lohde). — Upon 

 sporelings (prothallia of Aspidium and Pteris) this disease is 

 first shown by a yellow or yellow-brown color, as seen in 

 mass. Under a hand lens the abnormal color is seen as spots, 

 varying from green to yellowish-brown and later to black. 

 In later stages disintegration of the affected cells gives the 

 prothallia a ragged appearance. 



GERANIUM (Pelargonium) 



Gray-mold (Botrytis sp.). — Frequently this mold appears 

 on old blossoms, thence spreads to buds and even to leaves. 

 Proper sanitation, destruction of all refuse, and attention to 

 ventilation usually prevents this mold. 



Bacterial leaf-spot (Pseudomonas erodii Lew.). — The 

 spots are watery, brown when old. The affected leaves fall. 



