208 Report of the Botanist of thh 



in Western New York, and in 1900 it probably did about the 

 usual amount of damage. Plantations with 10 per et. of rusty 

 plants were frequent; and occasionally plantations were found 

 in which 25 per ct. or more of the plants were rusty. We 

 have often noticed in Western New York, as in the Hudson Val- 

 ley, that rusty plants bear fewer prickles. In Chautauqua 

 County the parasitic fungus Tuherculina persicina, was common 

 on raspberry rust as well as on blackberry rust. Where the 

 parasite was present the affected plants were less conspicuous, 

 the leaves being purplish instead of bright yellow. 



In September the teleuto form was frequently observed. 

 Powdery Mildew {Oidium ruborum Rabenh.). — In several local- 

 ities we observed, during May and June, a powdery mildew on 

 the foliage of black raspberries. In every case it was confined 

 to plants infested by rust, CcBoma nitens, never occurring on 

 healthy plants. It occupies both sides of the leaves. No peri- 

 thecia were found. It is probably referable to Oidium ruborum 

 Rabenh. The same mildew has been found on blackberries. 

 (See page 185.) 



Cane Blight {Coniothi/riuin sp.).— This is the cane blight de- 

 scribed in Bulletin 167, pages 305-307. It has been found to be 

 common in the raspberry plantations of Western New York as 

 well as in the Hudson Valley. At Peruville it injured a crop of 

 Cuthberts to the extent of about 50 per ct. On black varieties 

 it often begins its attack in the dead stub which results from 

 heading back the plants by cutting after they have become large 

 and woody. From this point the disease works its way down- 

 ward killing successively the lateral branches. 



It has now been proven by inoculation experiments with pure 

 cultures that the Sphoeropsideous fungus found in such abun- 

 dance on the diseased canes is really the cause of the disease. 

 (See Plate XXVII.) The fungus properly belongs to the genus 

 Coniothi/rium rather than to PJioma as stated in Bulletin 167. 

 As a rule, the spores are decidedly brownish. 



We have also learned to recognize the disease on the young 

 canes. In August and September new canes of red raspberry 



