LETTUCE ROT. 105 



down the aphis. It can easily be kept out of the houses 

 by fumigating twice a week with tobacco, and probably 

 with the rose leaf extract of tobacco. Do not wait until 

 the insect appears. Begin fumigating as soon as the plants 

 are first pricked off", and continue until within two or 

 three weeks of harvest, or longer if necessary. 



The rot often ruins crops of lettuce. The outer leaves 

 decay, often quickly, and fall flat upon the ground, leav- 

 ing the central core of the plant standing. Fig. 35 is a 

 fair sample of a plant collapsed by rot. I once lost an 



35. Lettuce plant collapsed by the rot. 



entire crop by this disorder. The plants were about two- 

 thirds grown and in good condition. The house was 

 rather over-piped for lettuce, and we kept it cool by care- 

 ful attention to ventilation. It became necessary to be 

 absent three days in midwinter. Careful instructions 

 were given a workman concerning the management of 

 the house, but he kept it too close and too wet, and at 

 the end of the three days the crop was past recovery. 



This lettuce rot is due to a fungus (Botrylis vulgaris) 

 which lives upon decaying matter on the soil, but when 

 the house is kept too warm and damp, and the lettuce 

 becomes flabby, it invades the plant and causes irrepara- 

 ble ruin. There is no remedy, but if the soil is sandy 

 and "sweet" and the house properly managed as to 

 moisture and temperature, and top dressings of manure 



