156 BIOLOGICAL PROBLEMS 



it prevailed earlier and to a more serious extent in 

 these counties. 



Many questions have been asked as to whether, if 

 the disease be a disease of middle age, we cannot 

 evade blight by a choice of suitable varieties, or 

 adopt some ruse such as late planting or planting 

 early varieties only in districts where blight is late, 

 and thus tiding the plant over the probable time of 

 fungal activity; or, again, whether certain methods of 

 manuring, certain soils, &c., render the plant less 

 liable to attack. The experience of the last seventy 

 years has shown that a suitable land, a happy sequence 

 of weather conditions, correct manurial treatment, and 

 good cultivation ameliorate but cannot prevent the 

 pestilence; it may be because we can rarely hope to 

 obtain ideal conditions. Spraying has been adopted 

 for these very reasons. The State requires immense 

 supplies, and to meet the demand potatoes must be 

 grown wherever possible. Since, however, we aim at 

 economy of effort, everything good husbandry can 

 do should be done to reduce the risk of disease. In 

 1845 considerable attention was given to the con- 

 ditions of weather, soil, soil treatment, and suscepti- 

 bility of varieties in relation to the murrain, and very 

 numerous and valuable observations were made. To- 

 day, possessing, as we do, a more accurate knowledge 

 of Phytophthora infest ans^ and equipped with an effi- 

 cient weapon, we should make an effort to settle some 

 of the problems which baffle the grower and react in 

 the end prejudicially on the practice and purpose of 

 spraying. 



These various factors could be analysed by con- 

 ducting numerous trials on farms and allotments, 

 especially in those counties where disease is usually 

 severe, and by tests in experimental gardens, where 

 the more technical questions could be studied. 



