REPORT OF THE SOCIETY 103 



(f) Hollow heart. 



This condition occuis as a result of the too rapid growth of the tubers. 

 Some varieties, such as the Rural New Yorker, when grown in rich soil, fre- 

 quentl}' develop hollow heart. The tissues surrounding the irregular space 

 in the heart of the tuber are brown and lined with a corky laj^er. The trouble 

 is not serious from a pathological point of view. 



(g) Arsenical injury 



This is not serious when ordinary precautions are observed. Arsenic 

 oxide is the base of any arsenical spray used in controlling chewing insects 

 and its use alone would cause severe burning to the foliage. It is therefore 

 necessary to use it in a combined form such as Paris green, lead arsenate, 

 calcium arsenate, etc. The arsenate is better used in combination with 

 Bordeaux, so that sufficient lime is present to prevent burning of the foliage. 

 Burning occurs where insects have made injuries and in the axils and margins 

 of leaves where the insecticide is likely to be held in quantity. The use of a 

 finer spray from high pressure nozzles will usually prevent such accumulations 

 of material on the plant. 



General considerations in control 



1. Control of potato diseases bj' the grower involves as a first essential 

 that the grower know the diseases which have to be controlled. Every grower 

 of potatoes on a large scale ought to familiarize himself with symptoms and 

 with the major points in the life history of the causal organism if such exists. 

 To do the right thing at the correct time necessitates accurate knowledge. 

 Information can always be obtained from Macdonald College in Quebec, 

 from the Ontario Agricultural College in Ontario, from other agricultural 

 colleges throughout the Dominion and also from Provincial and Dominion 

 Departments of Agriculture. No grower need lack technical help to-day in 

 this respect. 



2. Next to a knowledge of the diseases to be controlled and how to control 

 them, the most important point is to know thoroughly the variety or varieties 

 most suitable for the locality and the market. It is best to grow only one or 

 two varieties and to know these so that "off varieties'' can easily be detected 

 and rogued from the seed plot. Grow a seed plot every A'ear ant\ select hills 

 for freedom from disease and for yield and type. In arranging the seed plot 

 choose clean land, prepare it well, practise deep plowing and rotation with 

 legumes and cultivate the potatoes thoroughl3\ 



3. As to the seed tubers themselves the selection of thoroughly clean, 

 sound tubers is a prime requisite. Too many growers still plant scab, black 



