566 INSECTS AFFECTING VEGETATION 



suits elsewhere, indicating that spores were not introduced by the 

 seed, whilst the manure employed started no infection elsewhere. 

 This indicates prolonged vitality on the part of the fungus, which 

 would render starving out a very tedious process. 



It is quite clear, however, that the black scab disease threatens 

 to inflict such serious injury on the potato crop as to warrant the 

 Board of Agriculture taking official action. The disease is viewed 

 with alarm by both the scientific and the practical man, and yet no 

 steps are being taken to deal with this pest which, if it is allowed to 

 spread through the country and to reach Ireland, will cause losses of 

 hundreds of thousands of pounds. 



Borthwick (1907), referring to an outbreak in Scotland, said 

 that the whole crop was damaged to the extent that they could not be 

 used. They were quite useless, the early varieties being, if anything, 

 worse than the late, especially the early kidneys. The disease was 

 first noticed when the new potatoes began to form. It first appeared 

 on the stems as a greenish-looking canker, which attacked the tubers 

 as they grew and soon made them a mass of corruption. 



All infected potatoes should be boiled or burned. No part of 

 any lot containing diseased potatoes should be used for seed pur- 

 poses. If the disease is found on growing potatoes, heroic measures 

 should be taken to eradicate the trouble by burning the entire lot 

 and planting no more potatoes on that field for six or seven years. 

 (B. P. I. Cir. 52.) 



TOMATO DISEASES. 



Leaf Blight of Tomato. Leaf blight (Septoria) is frequently 

 seen on field crops of tomatoes, but we have not noticed it on crops 

 grown under glass. The trouble has occasionally been observed in 

 this state on greenhouse tomatoes. For field crops spraying has been 

 recommended. In the greenhouse the remedy is more simple, since 

 the disease, according to our observation, results from too much 

 crowding, and is of rare occurrence here. 



A similar spot is often found on chrysanthemums. On both 

 tomatoes and chrysanthemums the disease is confined to the lower 

 shaded leaves of closely planted crops, and it has never been observed 

 by us on individual plants of chrysanthemums grown in pots or 

 where light and air have access to the foliage. In the fall and win- 

 ter, when the light is poor, the lower leaves of crowded plants often 

 deteriorate and show signs of prematurity; consequently becoming 

 more susceptible to disease. To prevent this trouble the crop should 

 not be planted too closely, and the foliage should receive more air 

 and sunlight. On too closely planted tomato plants the lower leaves 

 may be removed, and if diseased, destroyed. The pruning of the 

 lower leaves is not harmful and lets in more light and air where it is 

 needed. (Mass. Bui. 138.) 



Damping Off. This disease rarely occurs, excepting in the 

 seedbed. It manifests itself by the plants falling over, and looking 

 very much as if they had been gnawed off by some insect. These 

 apparently gnawed-off areas occur at different points in the seedbeds, 

 and the fungus which causes the trouble spreads out from these 



