256 



SCIENTIFIC AGRICULTURE 



i:tL'i. 



The Stayiiiaii does not e(iual its parent the Wiuesap 

 iu color, although in the South end of the Okanagan it 

 colors well and makes quite an attractive apple when 

 packed, and is in gocd demand on the market. 



The tree comes into bearing young and is a reliable 

 crojiper. Due to the limited plantings of this variety, 

 sufficient i-ecords were not received on yields to obtain 

 a good average. 



Gravenstein. — More attention is being paid to the 

 Gravenstein in the Summerland and Pentieton sections, 

 and although no yield records were obtained it vvould 

 appear that the Gravenstein may become one of the 

 leading Fall apples in the sections above mentioned and 

 possibly in the Osoyoos country as well. 



Due to its high quality, the Gravenstein is in good 

 demand on the market, and will generally bring a com- 

 liaratively high price. The planting of this variety will 

 be limited for some time until it is more thoroughly 

 tested out. 



Jonathan.— This is one of the leading varieties now- 

 grown in the Okanagan. It is better suited for the 

 Southern end of the valley and fntrre plantings will be 



chiefly confined to the Osoyoos and Similkameen dis- 

 tricts, and there only as a filler. The Jonathan has not 

 proven a vei-y hardy tree and is subject to Winter in- 

 .iury except in favored localities. This variety is w-ell 

 received on the market. 



Wagener. — As shown in tables 3 and 4, the Wagener is 

 not a heavy yielder; this of cour.se is to be expected as 

 the Wagener is a small growing tree. 



The tree is not jiarticularly hardy and during extreme 

 ccld weather it is subject to winter injury, but fortun- 

 ately appears to be able to make a quick recovery. In 

 favored locations the Wagener does well, but future 

 plantings will be limited as it can only be considered as 

 a filler and is not a strongly favf)red apple on the mar- 

 ket. 



Yellow Newton. 



Tlie market demand for the Newton is generally 

 good especially in the Old Country, but this variety 

 has not proven a heavy yielder as will be noted in 

 Tables 3 and 4. and is not recommended for future 

 planting. 



Experiments in the Control of Rhizoctonia or 



Black Scurf of Potatoes 



By J. E. HOWITT. 

 Professor of Botany, O.A.C., Guelph. 



Rhizoctonia or Black Scurf is very frequently met 

 with in Ontario and in seasons of excessive rain-fall 

 often results in a noticeable reduction of the crop. 

 Tubers are frequently seen with what appear to be 

 lumps of hardened soil adhering to them. These when 

 wet are black in color and they vary in size from 

 mere specks to one-quarter of an inch in diameter. 

 Sometimes they are very numerous and so noticeable 

 as to render " the tubers unsightly, and hence, not 

 readily saleable. These little black lumps are known 

 as selerotia and consist of compact masses of resting 

 fungus threads (mycelium.) The flesh of the potato 

 beneath is not injured to any extent by them. If, how- 

 ever, tubers with these little black lumps adhering to 

 them are planted, the fungus may spread to developing 

 sprouts and kill them before they get above the ground, 

 this being one cause of misses in the rows. Later in 

 the season several other symptoms may develop. Young 

 shoots may wither and die and if these are pulled up 

 and examined, there w-ill be found at the base of the 

 stem browni, dead, areas often, encircling it. Some- 

 times at the base of the stem of affected plants a clus- 

 ter of small tubers may be found and frequently small 

 greenish potatoes are seen on the stem above the 

 ground. Such aerial tvibers are very characteristic of 

 the disease, but may result from other causes, such as 

 injury to the stem by cultivation. 



The chief means by which the fungus is spread is 

 through planting potatoes with selerotia adhering to 

 them. The same fungus attacks many cultivated plants 

 besides potatoes and frequently causes the damping-off 

 of seedlings. 



Since the fungus lives on so many different plants 

 and appears to be native to many soils it is impossible 



to "starve it out" b,v a rotation of crops and there has 

 been very great difficulty in the past in preventing this 

 disease. Experiments have been conducted here at the 

 Ontario Agricultural College for the past two years 

 with the ol)jcct of determining if the amount of Black 

 Scurf or Rhizoctonia can be reduced by selecting seed 

 tubers free from the characteristic little black lumps, 

 or selerotia, and what strength of corrosive subl^iate 

 and what time of immersion gives the best control of 

 this disease. 



The results for 1920 are very striking. They may be 

 summarized as follows: Selecting tuber.s free from 

 selerotia and planting them without any treatment was 

 found to reduce the amount of badly disfigured tubers 

 from 98-9 to 82 per cent. Immersing seed potatoes 

 covered with selerotia in corrosive sublimate solution, 

 one part by weight to 2,000 of water for two hours re- 

 duced the disfigured tubers to 21 per cent. Immersing 

 similar seed in corrosive sublimate, strength 1-1000 for 

 two hours reduced the disfigured tubers to 14 per cent ; 

 corrosive sublimate 1-2000 for three hours reduced the 

 disfigured tubers to 16 per cent ; corrosive sublimate 

 1-1200 for one hour reduced the disfigured tubers to 

 18-8 per cent; and cori'osive sublimate l-i'iOO for two 

 hours gave perfect control, there being no badly dis- 

 figured tubers obtained from seed which was treated 

 with corrosive sublimate of this strength. 



The results of two years experiments show very 

 clearly the effectiveness of corrosive sublimate in the 

 control of this disease. These experiments are being 

 continued with the object of detei-mining what strength 

 of solution to recommend to tiie farmers of (Ontario in 

 order that they can prevent this disease effectively, 

 with the least labor, and the least cost. 



