Indiana Plant Diseases, 1921 179 



(jorn. — HofFer reported a loss of about 10 per cent in the corn 

 crop due to root, stalk and ear rots. He has given a very concise ex- 

 planation of the present understanding of the root and ear rot problem 

 in a current bulletin of the federal Plant Disease Survey (26) in which 

 he shows that the Fusarium root rot is not a specific parasitic trouble 

 comparable to cabbage yellows and tomato wilt but is more or less 

 dependent on predisposition of the plant to infection by certain soil 

 conditions. Ear infection is local and not the result of systemic in- 

 fection of the plant and seed infection or infestation is important mainly 

 in connection with the vigor of the seedlings and has little direct rela- 

 tion to the occurrence of root rot later. Ear rots due to Fusarium, 

 Penicillium and Diplodia were particularly destructive this year because 

 of the wet fall and the widespread injury by the corn ear worm. Hoffer 

 reported that Diplodia ear rot occurred on as high as 75 per cent of 

 the ears in certain fields. Smut (Ustilago zeae) was generally prevalent, 

 especially on sweet corn, but, according to Hoifer, was not as abundant 

 as in 1920 owing to the drouth during the early growing season. One 

 lesion of Physoderma zeae-niai/dis was fovmd by Trost at Lafayette on 

 Early Evergreen sweet corn. 



Cowpeas. — The spot disease of cowpeas previously reported as due 

 to a Phyllosticta occurred at Lafayette and has been found to be bac- 

 terial in nature. Reddish brown spots on the leaves, stems and pods 

 and constriction of the pods are produced. The disease is seed-borne 

 and in its effect on the pods causes considerable loss in the yield of 

 seed. Leaf-spot caused by Cercospora c.ruenta occurred in the experi- 

 mental plot mentioned above and also was noted in Knox County. It 

 became severe enough to kill the leaves in some cases. A powdery mil- 

 dew became very severe in the fall on cowpeas in the greenhouse. 

 Large brown blotches were produced on the leaves and hypccotyls and 

 the plants were defoliated and killed outright. The attack on cowpeas 

 was much more severe than on adjacent rows of lima beans. Perithecia 

 were not found and whether or not this is Microsphae,ra enphorbiae 

 recorded by Fawcett (13) on cowpeas is not known. 



Cucumbers.— Wilt caused by Bacillus tracheiphilus was the most 

 important disease in the pickle, market garden and greenhouse crops. 

 Gregory reports wilt destructive to the fall crop in greenhouses at Terre 

 Haute. Observation of numerous fields in the vicinity of Plymouth on 

 August 2 showed a loss of three to ten per cent in stand due to wilt. 

 The disease was also found in Marion and Tippecanoe counties and was 

 reported from Allen, Fountain and Fulton counties. Row planting or 

 the hill system with numerous plants in each hill and postponement of 

 final thinning until the peak of the wilt epiphytotic has passed are sug- 

 gested as palliatives for this disease. Bacterial wilt has been dis- 

 cussed in more detail in connection with cantaloupes. 



Mosaic seemed to be less prevalent than usual this year. In the 

 pickle crop near Plymouth, it was noted only on scattered plants on 

 August 2 and seemed to be of late inception. It was noted as early as 

 .July 12 near Indianapolis and was severe by September 7. It was very 

 severe in a field near Hammond on August 31 and was noted near 



