130 SEVENTEENTH REPORT. 



The disease so far as a hasty survey of the literature is con- 

 cerned has never been described, although a number of bacterial 

 diseases of lettuce have been worked with.. No doubt the similarity 

 of the signs of this disease to the Eosette has caused this oversight. 

 The disease is however distinct and for it I propose the name, The 

 Stunting Disease of Lettuce. Further work is under way upon this 

 disease. 



The constancy of the appearance of disea.sed plants throughout 

 an entire setting, indicates a seed-bed source for the disorder. 

 Moreover the per cent of loss varies greatly, at one time be- 

 ing as high as 90 per cent while the next year the loss was from 

 5 to 10 per cent in the same bed. If we assume for this disease, an 

 immunity in older plants as has been mentioned for celery, we have 

 a plausible explanation for the conditions outlined. Where healthy 

 seedlings are set out in spots where the Stunting Disease has 

 killed the plant, these plants reach maturity. 



As has been said the loss from vear to vear seems to varv with 

 the comparative health of the seedlings. The health of the seedlings 

 is associated with the newness of the soil in the seed beds, but even 

 with fresh soil the disease has api>eared. Considering the crude- 

 ness, so far as sanitary precautions with which this renewal takes 

 place in the ordinary greenhouse, there is still plentv of oppor- 

 tunity for a quick reinfestation. This is especially augmented by 

 the fact that the laborers who transplant the seedlings from the 

 first seed-bed commonlv work alternatelv in the growing beds and 

 in the propagating houses. Sterilization of the soil has been tried, 

 but here again the failure to make the clean-up absolute, has made 

 conclusion impossible as to the efficacy of this measure. Where 

 one seed bed has been sterilized, it frequently hai»i)ens that the 

 first transplanting will take place to an old bed which has pre- 

 viously borne diseased seedlings, and vice versa. From failure to 

 realize the infectious nature of the trouble, and from the failure to 

 prevent a quick reinfection, steam sterilization, which would prob- 

 ably be an effective control measure has fallen into disrepute. 



So far, the disease has been found in Grand Kapids and Ann 

 Arbor greenhouses. The outbreak in Ann Arbor was in soil that 

 had never Ik'cu usimI for greenhouse i)urposes, and the disease was 

 fir.st noticed in a bed jjlanted with seedlings bought in New York. 

 This points to a rather widespread distribution of the disease. 



Its seriousness may be seen from the following counts made in 

 squares of a hundred i)lants, lying adjacent in a bed, 6%. 3%, 3%, 

 4%, 3%, 6%, 3%, 6%, 3%, 3%, 7%, and 5%. The margin in lettuce 

 growing between cost of production and selling price" is sometimes 



