46 SECOND REPORT ON ECONOMIC BIOLOGY. 



PREVENTIVE AND REMEDIAL MEASURES. 



The bushes should be sprayed early in the season with cupram 

 made as follows : 



To one pint of strong ammonia add four quarts of water. Care 

 should be taken to avoid the fumes. In this ammonia liquor suspend 

 by a copper wire, two ounces, by weight, of carbonate of copper 

 wrapped up in copper gauze. Allow this to remain over-night. When 

 required for spraying add another tw T enty-five gallons of w r ater. 



After the fruit has been gathered, the bushes should be sprayed 

 with Bordeaux mixture, and wherever possible the fallen leaves should 

 be burned. 



ROOT AND STEM ROT. 



Rhiooctonia violacea (Tul.). 



In June last a serious outbreak of this disease on upwards of 

 ninety acres of potatoes was inspected in Staffordshire. 



The disease is due to a fungus that appears under a variety of 

 forms and names and attacks a great variety of plants, such, for 

 instance, as potatoes, asparagus, beet, bean, carrot, cabbage, cauli- 

 flower, clover, lettuce, lucerne, mangels, radish, pea, tomato, and a 

 variety of bulbous plants and weeds. It does not attack cereals. 



" The mycelium behaves in a slightly different manner," writes 

 Massee, 1 " and presents a modified appearance when growing on 

 different hosts, hence several different species of Rhizoctonia (all 

 sterile) have been proposed, but infection experiments have proved 

 the soundness of Tulasne's conclusions that all belonged to one and 

 the same species." 



The fungus lives in the soil, but so far as is known at present it 

 never fruits. It is spread and propagated by the formation of little 

 concentrated masses of mycelium ; these may be very small and 

 attached to the surface of the tuber, or they may be as large as a pea 

 and remain in the soil, free from the roots, and serve as centres of 

 future infection. 



In some cases little injury is done to the potatoes, in others, the 

 stems and tubers rot and very serious losses ensue. 



1 Diseases of Cultivated Plants, 1910, p. 236. 



