Feb. i, i9« Onion Smudge 719 



the former and eventually causing a softening of the latter. In bulbs 

 inoculated in moist chambers the fungus progresses fairly rapidly, caus- 

 ing softening and lamination of the walls and the gradual collapse of the 

 cell. The stroma involves the subcuticular wall at first and later the 

 underlying cells, but the cuticle remains unbroken until the acervulus is 

 formed. The process of invasion under storage conditions is essentially 

 the same but much slower. 



(17) The fungus overwinters as stromata in infected scales. 



(18) Infection occurs at or above io° C, but progress is very slow 

 below 20 ; the optimum is about 26 . 



(19) Conidia are produced abundantly under moist conditions and at 

 temperatures between 20 and 30 C. They are disseminated chiefly by 

 meteoric water, especially spattering rain. 



(20) The disease develops most rapidly in the field when the mean soil 

 temperature range lies between 20 and 30 C. and is accompanied by 

 abundant rainfall. Extremely hot, dry weather in July checks progress. 

 Presence of moisture favors the progress of the disease during the curing 

 period, whereas artificial drying of sets immediately following harvest 

 checks it. 



(21) Smudge tends to promote premature sprouting and increases 

 shrinkage of sets in storage. The disease may spread from bulb to bulb 

 in the crate under very moist conditions, but in proper storage this factor 

 is negligible. 



(22) The important measures of control are protection of the har- 

 vested crop from rain, rapid and thorough curing, and provision of well- 

 ventilated storage at about 33 to 36 F. 



LITERATURE CITED 



(1) Allescher, Andreas. 



1898-1901. fungi imperfecti . . . 1016 p. Leipzig. (Rabenhorst, L. Kryp- 

 togamen-Flora von Deutschland, Oesterreich und der Schweiz. Aufl. 

 2, Bd. i, Abt. 6.) 



(2) Atkinson, G. F. 



1897. some fungi from Alabama . . . Bui. Cornell Univ. (Sci.), v. 3, no. 1, 

 50 p. Bibliography, p. 2. 



(3) Bennett, J. L. 



1888. PLANTS OF RHODE ISLAND, BEING AN ENUMERATION OF PLANTS GROWING 

 WITHOUT CULTIVATION IN THE STATE OF RHODE ISLAND. 128 p. 



Providence, R. I. 



(4) Berkeley, M. J. 



1851. [a new onion disease.] In Gard. Chron., 1851, no. 38, p. 595, 2 rig. 

 (5) 



1874. notices OF north American fungi. In Grevillea, v. 3, no. 25, p. 1-17. 

 Continued article. 

 (6) Blackman, V. H., and Welsford, E. J. 



1916. STUDIES IN THE PHYSIOLOGY OF PARASITISM. II. INFECTION BY BO- 



trytis cinEREa. In Ann. Bot., v. 30, no. 119, p. 389-398, 2 fig., pi. 

 10. Literature cited, p. 397. 



