DISEASES AND INSECTS 299 



curing period. This will prevent moisture from being deposited 

 on the walls. As the air warms, it expands and takes up moisture. 

 When it cools, it contracts and gives up its moisture. This makes 

 it important to get the moisture-laden air out of the house by 

 ventilation. When the potatoes are thoroughly dried or cured, 

 the temperature should be gradually reduced to 55 F. and kept 

 as near that point as possible during the remainder of the storage 

 period. If the temperature goes below 48 F., a fire should be made 

 and the temperature raised to 55 F. When the temperature goes 

 above 60 F., the house should be opened in the cool of the day, 

 to lower the temperature to 54 or 55 F., and then closed. In mild 

 weather the ventilators in the roof may be partly open all the time, 

 but they should be closed in cloudy or cold weather. 



Methods of Heating a Storage House. A small house can 

 be heated with a sheet-iron stove that will burn knots and other 

 pieces of wood. Coal stoves may be used if preferred, but air-tight 

 wood stoves will serve the purpose. It requires a longer time to 

 get up heat with a coal stove than with a wood stove, and this is one 

 disadvantage in using coal. Often all that is necessary to raise 

 the temperature a few degrees is to start a little wood fire. In a 

 commercial storage house a hot-air heater or a hot-water boiler, 

 with pipes around the walls, would be preferable to a stove, but 

 a house that will hold as many as 10,000 to 25,000 bushels of 

 sweet potatoes may be heated with good stoves. The location of 

 the stoves in the house depends on the size of the house and the 

 direction of the cold winds. Ordinarily, where one stove is used, 

 it is placed near the centre of the house, but if the cold wind strikes 

 one end the stove should be in that end. Some storage houses have 

 a small stove in each end, and this is the best arrangement for a 

 long house. Others have a stove in one end, with the pipe entering 

 the chimney at the other end. Considerable open space should be 

 left around the stove to prevent the potatoes from being injured 

 by excessive heat. 



By giving close attention to opening and closing the house, very 

 little artificial heat will be needed in the lower South after the 

 curing period. 



Diseases and Insects. The sweet potato is quite free from 

 injurious diseases and insects. The most destructive disease is 



