128 SEVENTEENTH REPORT. 



While the apothecial stage has not been produced from these sclero- 

 tia it is very likely that this Sclerotima is the common Sclerotiiiia 

 libertiana Fckl. which Keddick* has found to attack celery, pro- 

 ducing similar effects. 



As the disease gradually advanced on the stalks a reddening be- 

 came evident. It is likely that the trouble called "Red I^ot" by the 

 growers is this same disease. 



The history of the disease indicated that it occurred to a slight 

 extent in a portion of a field Avhich had received manure Avhich had 

 contained refuse from a grocery- store. In view of the connnon 

 occurrence of this fungus on vegetables the introduction of 

 the fungus into the marsh, in this manner is very probable. 

 The marsh had been under cultivation only a very few years and 

 had grown nothing but celery and onions. Since the first appear- 

 ance of the disease the spread has become more extensive and now 

 large areas show rotted bunches in the trenches. 



LETTUCE DISEASES. 



Lettuce grown in the field in Michigan is subject to but few 

 serious diseases. Head lettuce frequently shows a high percentage 

 of loss as it grows in the field due to the attack of BaciUus caroto- 

 vorus. 



lettuce grown under glass is injured to a much greater extent by 

 diseases. Two leaf diseases, Downy Mildew and Leaf Anthracnose 

 (due to Marssonia jiei-forans E. & E.) are coimnon. Of these, Bremia 

 is by far the more widespread. As a control measure for Bremia 

 some growers are painting the steam pipes with commercial Lime 

 Sulphur. The leaf anthracnose due to Marssonia is restricted in its 

 spread, but with improper watering may greatly damage a crop. It 

 has been found in Grand Rapids, Port Huron and Ann Arbor. 



In a few green houses where the soil was kept excessively wet the 

 gray mould i^clcrotinia fuckeliana (De By.) Fckl. was common on 

 the lower leaves. I^ettuce drop caused by Sclerotinia lihertiana 

 Fckl. was found in one greenhouse upon from 2 to 7 ])er cent of 

 the plants. This greenhouse had been erected but a year and the 

 a]>])earance of the disease to such an extent in the first year's crop 

 is out of the ordinary. The greenhouse however was erected on an 

 old garden spot and to this no doubt the great prevalence of the 

 disease may be attributed. 



A disease which corresponds very closely with the Black Rot of 

 Lettuce described bv Raiusevt in r.M)4 but for wliich no causal 



♦Redfllok. D. Plivtopatholosv .S : ITO.. 1014. 



vU.inis(\v. II. .T. Wis. St!i. U.'port. I'.xU : 2T!»-2SS. 2 li^'s. 



