1891.] JESSAYS. 51 



Mildew. 



As mildew is the greatest obstacle to the growth of good 

 lettuce and occasions the greatest loss to market gardeners, it 

 becomes the grower to study most carefully all the conditions 

 liable to produce it, for here, if anywhere, the old adage proves 

 true, that " an ounce of prevention is worth a pound of cure.'''' 



Our Hatch Experiment Station at Amherst has already ren- 

 dered much aid in determining and publishing some of the condi- 

 tions by which this disease may be brought on. But I do not 

 think that they have yet determined all those conditions. Be- 

 sides, there are several other diseases that appear to be distinct 

 from mildew, wiiich often accompany it — sometimes preceding, 

 and sometimes following it — that are quite as destructive as the 

 genuine mildew. These diseases, if they really are distinct from 

 mildew, do not seem to be described in the bulletins issued by 

 the Experiment Station. 



The conditions which produce mildew, as given by the Experi- 

 ment Station Bulletin, are five, viz. : 



(1.) Too high temperature at night, say 45° to 50°. 



(2.) Want of proper plant food in the soil. 



(3.) Too much moisture in the soil. 



(4.) Sudden and extreme changes in the temperature when the 

 plants have been growing rapidly and are soft and tender. 



(5.) The same temperature both day and night. 



All these conditions, I think, are correct as far as they go. 

 But there is one other condition not mentioned in their bulletins 

 that I am quite sure produces a disease that often accompanies 

 the mildew, and may be a result of mildew, unless it is a distinct 

 disease. The disease is black rot in the head of the lettuce just 

 before it is ready for market, that resembles what is called 

 "scorching" of the head, but is, I think, diflferent from it. Too 

 great dryness in the soil, when the lettuce is nearly headed, will 

 cause this phase of the disease. 



The rotting off of the trunk of the lettuce junt beneath the 

 head, when almost mature — and sometimes so suddenly as to 

 leave the head loose before it has wilted — is another disease that 

 sometimes accompanies the mildew, and may be a result of it, or 

 it may be distinct disease. Too great moisture, occasioned by 



