Rural School Leaflet 917 



but shallow later so as to prevent injury to the roots of the plants. The 

 weeder is a valuable tool to kill weeds in the row. It must be used before 

 they get a start. 



The original potato plant, when wild, blossomed before the tubers set. 

 Now under cultivation both processes overlap. This usually comes in 

 a period of hot weather and at a time when late blight is m_ost active, 

 and is the danger period in the life of the potato. If many roots are cut, 

 the crop receives a shock from which it never fully recovers and it is 

 prevented from making the yield that it might make. The whole profit 

 on a crop may be lost by late hilling in dry weather. 



Potatoes are subject to the attacks of several enemies, the worst of 

 which is the late blight and rot. This disease is carried through the winter 

 in the tuber and passes into the soil after planting. 



When the soil is wet the spores pass from the seeds to the surface of 

 the soil and come in contact with the leaves, in which they produce the 

 disease. In damp, muggy weather the entire crop may be killed in a 

 few days. The spores later fall from the leaves to the ground and, if the 

 soil is very wet, may attack and rot the tubers. Dry weather checks 

 the progress of the disease. Spraying with bordeaux m.ixture, made of 

 sulfate of copper, lime, and water, is almost always profitable. The 

 copper in the bordeaux kills the blight germs when they touch the 

 leaf that is covered with it. The spray should be applied early in order 

 to be on the leaf ahead of the blight. 



The time to spray is just before a rain if possible. The blight spreads 

 only in wet weather. The growth of the plant constantly forks new leaves. 

 The first rainstorm is the time these most need protection. 



We never know what season blight will come. The gain from spraying 

 in one year when blight occurs will pay for several years' spraying. Spray- 

 ing with bordeaux mixture seems to have a tonic effect on the potato even 

 when no blight is present. It also reduces the damage from several of 

 the less important potato diseases. 



Potatoes are subject to the attacks of several insect pests. Probably 

 the one that does the most damage is the black flea-beetle, which pierces 

 many small round holes in the leaves. It does not eat poisons but bor- 

 deaux helps reduce the damage. The common potato bug is best killed 

 with paris green or arsenate of lead. When the bordeaux also is used, 

 the paris green cannot bum the leaves, sticks better, and is spread more 

 evenly on the leaves, so that much less is needed. 



Hand sprayers are used for small areas, barrel pumps and horse-power 

 sprayers for the larger areas. In all cases the plants should be well covered 

 at each spraying. The higher the pressure, the finer the spray and the 

 better the results. 



