SEVENTEENTH ANNUAL YEAR BOOK— PART X 577 



The cherry mildew {PJwdospliaera Oxyacnnthae) was common though 

 less injurious than the season previous. The same may be said for the 

 lilac mildew {Microsphacra alni). It is interesting to note that this 

 fungus seldom occurs on the Persian lilac. 



The rose mildew {Sphaerotheca pannosa) was common only on Crimson 

 Rambler. Very little of the gooseberry mildew was observed. 



The corn disease (Fusarhim vioniliforme) . From one to two per cent 

 of the ears of corn were affected by the fungus. It was observed in a 

 few cases on the roots. However, none of the plants were broken as was 

 previously observed. It is probable that different seasons influence the 

 development o!f this facultative parasite. Attention should be called to 

 an oversight in our paper on Fusarium on corn to which Dr. C. W. Car- 

 penter has called my attention. Professor Sheldon describes this species 

 in the Report of the Nebraska Experiment Station for 1904 with figures 

 showing the moniliform microconidia. 



Cucumber wilt (Bacillus tracheipMUis^) appeared in a cucumber patch 

 in Ames in 1916. It was observed in a commercial greenhouse in Council 

 Bluffs in 191.5. It was also observed this year in Muscatine by Dr. I. E. 

 Melhus. 



Lettuce mildew {Bremia lactucae) was abundant in commercial green- 

 houses in Nevada and Des Moines, according to Dr. I. E. Melhus. It was 

 not observed on lettuce in the garden. 



Downy mildew {Sclerospora gravmiicola) was found in a few places 

 on nearly mature plants. Not as abundant as in 1915. 



Blister fungus of the White pine did not occur either on cultivated or 

 mature white pine on the currant in Ames or in any other part of the 

 state. 



Rust of gooseberries, (Acc«ZM(m grossulariae) was abundant on wild 

 species of gooseberries in the vicinity of sedges (Carex). 



Downy mildew of the grape (Plasmopara Yiticola) was widely scat- 

 tered but not abundant. The powdery mildew [Vncijiula necator) was 

 also widely scattered, but not serious. Qf the diseases on forest trees the 

 leaf spot of the Ohio Buckeye, Phyllosticta Paviae, was observed in Boone 

 and Story counties, though not as abundant as in 1915. The oak blight, 

 Gloeosporium, was not common. In 1915 it was severe on the white oak. 

 The sycamore blight was not common. The black walnut blight {Marsonia 

 jnglanclis) which frequently causes the leaves to fall during the late 

 summer was not uncommon this year but did not cause the early defolia- 

 tion of the tree, as in some years. 



The spot on hickory was fairly common. 



The black knot of the plum (PloiorigMia mortosa) not observed on 

 the cultivated American plum, though occasionally on the wild plum of 

 the same species. It was more frequent on the choke cherry. It is 

 common on plants around the lakes of northern Iowa. 



Enlarged plum (Exoascus communis) was noticed in a few cases on 

 the Miner plum. The plum pocket (J57. pruni) was reported from Han- 

 cock county on the cultivated plum by Dr. Melhus. 

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