INSECTS, FUNGI, PLANT DISEASES, ETC. 167 



has destroyed the vitality of the cells. The attack begins 

 with a small spot, which gradually enlarges until most of 

 the leaf surface is involved, and, unless the disease is 

 checked, the entire plant is so injured its power to pro- 

 duce tubers is destroyed. 



The remedy for this disease is Bordeaux mixture 

 sprayed on the plants just after they are six inches high, 

 and continued at intervals of tw r o weeks until June 1st. 



Oedema. Leaf curl of the tomato. The disease is mani- 

 fested by the rolling up of the leaves exposing the under 

 surfaces. The veins are very much swollen, and the 

 leaves become more or less brittle. The illustration of 

 this disease is copied from Bulletin 53 of the Cornell 

 Station by Professor G. F. Atkinson. The attack is made 

 on the older leaves first, and the plant dies from the base 

 upwards. 



Experience has shown that the disease is caused fre- 

 quently by an excess of water in the soil, or by a too 

 liberal use of ammoniacal fertilizers, so that irrigation 

 will help to retard the disease and judicious application 

 of fertilizers will prevent too vigorous growth of soft 

 tissue, which seems to be subject to the disease. 



Oospora scabies. Potato scab. A delicate white mold 

 first makes its appearance on the surface of the potato 

 (Irish), and the scab is developed by the tissues of the 

 tuber, at the point of attack, forming a layer of cork as 

 a protection against the fungus parasite. As the potato 

 grows this diseased place begins to crack and becomes 

 roughened. Very soon the entire hill of tubers becomes 

 infected. 



The remedy is preventive rather than curative. A 

 large per cent, of organic matter in the soil seems to en- 

 courage the development of the disease, and where lime 

 and stable manure are used in large quantities there is 

 danger of having this parasite on the crop. Scabby 



