64 I'RKVENTIVE AND COMBATIVE MEASURES. 



plant- pathology may Ite carried out, while at the fjaine time the 

 cultivator could have advice with regard to the nature of any 

 disease and its treatment. Another system for the supjjly of 

 information is to be found in collections of specimens of plant- 

 diseases arranged for easy reference in places accessible to the 

 public. 



State supervision over crops under cultivation is also desirable 

 with a view to collect and distribute information concerning 

 prevalent crop-diseases. The same agency could also arrange 

 and, if need be, enforce a general and simultaneous treatment of 

 widespread epidemics, where proved methods were known and 

 advisaljle. Such regulations for supervising and combating a 

 plant-disease are already universally applied against the Phyl- 

 loxera. Similarly in Germany and other countries official 

 notice is annually given for extermination of mistletoe ( Viscum 

 album) on fruit-trees, and in Prussia the combating of Gnomonia 

 erythrostoma is carried out by order of the police authorities. 

 The tar-ringing of trees as a preventive against attacks of pine 

 moth {Gastropacha ^^mi), is regularly enforced everywhere in 

 forest-countries, and with the best result. In a similar manner, 

 in most countries, this and other forest pests are supervised by 

 the penal code, and combated with success. 



By arrangements of this kind it is possible to keep certain 

 diseases completely in check. Thus, as a result of regular in- 

 spection and the timely use of tar-rings, a dangerous outbreak of 

 pine moth is well-nigh impossible. Again, the universal steriliza- 

 tion of the seed-T5©T«;^ of cereals before sowing has done much to 

 exterminate smut-diseases. In the case of the Dodder-disease, 

 much can be done for its prevention by the careful purification 

 of clover seed. 



We shall consider tlie methods for combating parasitic fungi 

 under the following heads : 



I. Methods for extermination and removal of the parasitic 

 fungi alone. 



(1) Killing of fungi attached to seed through sterilization by 

 '^ means of hot water or copper steep-mixtures. 



(2) Combating leaf- frequenting fungi by dusting or spraying 

 l^ with mixtures containing sulphur or copper. 



(3) Excision and extermination of the sporophores of Polyporeae 

 ^}^ and Agaricini on orchard or garden trees. 



