Plant-Diseases and Insects. 



119 



are two distinct potato-blights in the country, both of which 

 also cause the tubers to rot. One is a true fungous disease 

 (due to Phytophthora infest arts'), and the other is bacterial. 

 The former is the old or true potato-rot. The relative fre- 

 quency of these two diseases throughout the country has not 

 been determined, but it is certain that much of the injury to 

 potatoes is due to the little-known bacterial disease. For- 

 tunately, the ammoniacal carbonate of copper and Bordeaux rot at °" 

 mixture are specific preventives of the old or true potato-rot, 

 if applied early and persistently. In Europe many experi- 

 ments have been made to determine the best means of keep- 

 ing the disease in check. An extended experiment was con- 

 ducted in Belgium and Holland in 1890 by E. Thienpont, the 

 results of which were published this year.* An abstract of 

 the investigation is here given : 



' ' More than forty men carried on experiments in treating po- 

 tato-foliage with the Bordeaux mixture as a protection against 

 the potato-rot. Ninety-five experiments were made, and the 

 plants were necessarily grown under widely different condi- 

 tions. The land upon which the potatoes were grown was of 

 all kinds, from sand to heavy clay. About forty varieties of 

 potatoes were grown, some of which were very early and 

 others late. The only fungicide used was the Bordeaux mix- 

 ture, and this was made with varying amounts of the sul- 

 phate of copper. Most of the planters made two applica- 

 tions only ; but some made only one, and others three. 



" Among these experiments there are only six in which no 

 difference between the treated and untreated plats could be 

 seen. No reason for this can be given, as there is a differ- 

 ence in the varieties grown, strength of mixture, number of fotin°~ 

 applications, etc. But in other cases, apparently the same Europe, 

 conditions gave excellent results. There were six plats which 

 gave unsatisfactory results ; 49 in which the gain was highly 

 profitable, and 34 in which complete success was reported. 

 These 95 results are on the whole conclusive ; but if all ele- 

 ments of error should be removed, such as imperfectly made 

 fungicides, wrong times and methods of application, etc., the 

 final result would probably show an astonishing degree of 

 success. The author fully realizes the difficulty of drawing 



*Le Traitement de la Maladie de la Pomme de Terre. Brussels. 



