147 



P.onlciiiix Mini nicotine sulphate sooinod to result in improved vino vigor 

 and yield where no funiious leaf diseases were present. This is hard to 

 explain excejit njion tlu" hasis of the partial leaf-hopper control secured 

 or the posslhle stimulation of the plant hy the copper. 



I'^ungous disease.s of the foliage were of no importance in the Indiana crop* 

 this year. T>ate hllght was not rei»orted. Early hlight caused hy Mtcniarid 

 .sdlinii was found in INIarion and Pdackford counties in June and in Clark 

 and Si. J(ise])h counties in Octoher, hut was evidently of no econonnc ini- 

 porlaiice. 



Fnsariuni wilt was, however, the cause of serious losses in tiie late croj) 

 and was hy Car the nu)st inijiortant fungous disease of Indiana potatoes. 

 The percenta.ue of yellowing or dead plants or shoots to he noted late in the 

 season was very high in many fields in the northern part of the state. The 

 ili>ease seemed to he especially destructive near Valparaiso. The vascular 

 discoloration in the hase of the main stem and in the stolons was pro- 

 nounced. Tuhers from diseased plants usually showed vascular discolor- 

 ation at the stem end frequently accompanied hy a rotted area externally 

 visihle as a sunken, wrinkled region about the stem end. The effect of wilt 

 (in the amount of yield is not known, but tubers showing the incipient stem 

 end rot do not endure storage. Whether or not this disease as it occurs 

 in Indiana, is primarily due to soil or to seed infestation is not know^n. 

 There was undoubtedly a high incidence of infection due to soil infestation 

 hut in addition there was striking evidence of seed carriage of disease 

 in tields planted with seed from dilTerent sources as observed by Gregory. 

 For example, in a field near Valparaiso, seed from Wisconsin showed less 

 than 1% of wilt August 13th,, field run Indiana seed, 25% wilt, and Indiana 

 seed selected for freedom from Fusarium infection, only 5% wilt. 



There was also in many fields a great abundance of localized root lesions 

 in connection with which the relative importance of Rhizoctonia and Fusar- 

 ium as causative factors has not yet been determined. Unmistakable Rhiz- 

 octonia cankers with the cracked brown tissue were of frequent occurrence 

 on the lower stem and with these were associated similar root lesions. Lat- 

 (>ral roots were found entirely cut off hy these lesions and in severe cases 

 the root system was sevei-ely reduced. In Lake County this type of root 

 trouble was very bad and apparently resulted in an uneven stand, (\ises 

 of a red discoloration of the rootlets suggesting Fusarium attack were also 

 frequently found. 



Black leg caused by Bacillus phi/fopJithoriis was found by Gregory in a 

 small percentage of plants in one field near Indianaiwlis. 



Among the tuber diseases, in addition to the Fusarium stem end rot 

 associated with wilt, common scab, black scurf, and russet scab were of 

 inqiortance. Common scab caused by Acfinonii/ccs scahicft was very severe 

 in the heavier soils, hut was successfully controlled by seed disinfection. 

 In a test field in Dekalb county, ;")!)% of the tubers grown from untreated 

 Seed were scabby, as compared with 5 to ll^/r from treated seed. Black scurf 

 caused by Rhizoctonia solaiii is of very general occurrence. A fairly 

 successful control of this disease was also secured by the mercury bichloride 



