250 



SCIENTIFIC AGRICULTURE. 



April, 192: 



.seed potatoes absolutely free from disease 

 the following standards have been set for 

 a crop to measure up to at each inspection 

 for 1922. These standards have l)een 

 drawn up I)y J. W. Eastliam, Provincial 

 Plant Patliologist, and the writer: — 

 A. Field Inspection. 



(a) First inspection (early summer (w 

 bloom-time). Foreign (impurities): Not 

 moi-e than 5 per cent allowed. Curly 

 dwarf, Leaf roll, IMosaic: Not more than 

 5 per cent of the coml)ined diseases allow- 

 ed. 



Wilt : Not more than 3 i)er cent allowed. 



Black leg : Not more than 2 per cent 

 allowed. At this inspection the presence 

 of rhizoctonia and early blight, also the 

 degree of severity of attack by these di- 

 seases is noted by the insjiector. 



(b) Second field inspection (late sum- 

 mer). 



Foreign (impurities) : Not more than 2 

 l^er (?ent allowed. 



Leaf roll, Curly Dwarf, Mosaic: Not 

 more than 2 per cent of the coml)iiuHl 

 diseases allowed. 



At this inspection the presence of late 

 blight and rhizoctonia, also the degree of 

 severity of attack by these diseases, is 

 again noted by the inspector. 



h"o(jueiv(j must be carried on throughout 

 the growing season by the grower. 

 B. Tuber Inspection. 



Rhizoctonia: Not more than 10 per cent 

 of sVujht rhizoctonia and not more than 3 

 per cent of severe rhizoctonia allowed and 

 no scurf spot larger than 1-8 inch in dia- 

 meter. 



O(rcasioii<il spots constitiitc sliglit. rhi- 

 zoctonia. 



Stem end discolouration: Not more 

 tlian 3 per cent allowed. 



Late blight or dry rots: Not more tlian 

 2 ])cr cciil allowed. 



Powdery scab: No severe powdery seal) 

 ali<»wcd. Not more than 1 per cent slight 

 ]iowdei-y scab allowed. Occasional spots 

 const it ulc slight powdery scab. 



Common scab: No severe common scab 

 allowed. Not more than 5 per cent of 

 tubers with slight common scab allowed. 



By severe common scab is meant infec- 

 tions (a) (covering more than 5 per cent 

 of surface of tuber: (b) taking the form 

 of cavities. 



Net necrosis: Not more than .5 per cent 

 allowed. ,, 



Internal brown-spot: Not more than 3 j 

 per cent allowed. 



Silver Scurf : Not more than .5 per cent 

 allowed. 



For the combined diseases, late blight or 

 dry rots, stem end discolouration and 

 rhizoctonia (severe) not more than 2 per 

 cent allowed. 



Foi- the combined diseases, late blight or 

 dry rots, stem end discolouration, rhizoc- 

 tonia (severe), net necrosis, internal brown 

 spot, and silver scurf, not more than 5 

 per cent allowed. 



For the combined diseases, late blight or 

 dry rots, stem-end discolouration, rhizoc- 

 tonia (slight), and common scab (slight), 

 not more than 7 per cent allowed. 



For the combined diseases, late blight and 

 dry rots, stem-end rot or discolouration, 

 rhizoctonia (slight), common scab 

 (slight), net encrosis , internal l)rown spot 

 and silver scurf, not more than 10 per 

 cent allowed. 



Grading and Tagging. 



Growers whose crop passes the above 

 inspections are required to grade their 

 seed to conform with desirable commercial 

 grades. No potatoes smaller than 3 

 ounces or larger than 12 ounces are allow- 

 ed Avlicre one grade of seed is being put 

 up. Where two grades of seed are being 

 made, the one to siupply those who re- 

 quire small whole seed for planting, po- 

 tatoes weighing 2 ounces are allowed in.i 

 the small wliole seed class. 



Crops which conform to the above re-' 

 gulations may l)e sold as certified seed.* 

 A tag is issued by the inspector for eaeh[ 

 sack of potatoes the grower has to dis-fe 

 pose of. This tag bears the name and ad-l 

 dress of grower, variety, size of seed, and| 

 (late of final inspection. It is attached jj 

 and sealed to each sack by tlie inspector 

 at shipping time. 



Some Results from Inspections made 



in 1921. ' 



The following table is a list of the 

 varieties, source of seed, and number ofg 

 Fields inspected in each district in 1921. 

 Also the average j^crcentage of two very 

 inq)ortant i)otato disease.% namely, Leaf 

 Koll and Mosaic, together with the aver- 

 age percentage of impurities: — 



