Corky Scah of Potatoes. 



The Corn Production Acts (Ptepeal) Bill proposes that the 

 amount payable in respect of this year's crops of wheat and oats 

 shall be 1*3 and X'4 per acre, respectively, and that payment 

 shall be made on 1st January, 1922, or about four months earlier 

 than would be possible if the Corn Production Acts remained in 

 force. 



* * * , * * * 



The Ministry has noted with regret the large number of cases 

 where seed potatoes affected with Corky Scab {Spongospora 



„ , _ , , suhterranea) have been sold for planting. 

 Corky Scab of , . ' • • • • V 



Potatoes ^ answer to various mquiries has con- 

 .sidered the renewal of the Corky Scab 

 Order which was suspended during the War. The whole 

 position has been examined, but in view of the following facts 

 the Ministry feels that it is at present undesirable to revive the 

 Order. 



(1) The risk of large new areas becoming infected appears 

 to be slight. From the Plant Disease Survey organised by the 

 Ministry it is clear that Corky Scab may in certain seasons 

 occur in almost every county. Whilst, therefore, it is alwa^'s in- 

 advisable to plant diseased seed, there are no large tracts of 

 country, at present clean, which would become infected if such 

 seed were used. 



(2) The intensity of the disease appears to be largely 

 matter of seasonal conditions. The Survey shows that during 

 1020 Corky Scab was very much more prevalent than usual, 

 and in many of the northern counties it occurred in a par- 

 ticularly severe form. [NEany soils which in normal years give 

 a clean crop, produced last season tubers badly affected with 

 Corky Scab. On the other hand, badly diseased seed may some- 

 times be planted and an entirely clean crop result. Although 

 it has not been proved by actual experiment, it appears 

 likely that the conditions leading to severe attacks are a cool 

 soil-temperature and a plentiful supply of soil-m( isture 

 during the growing season. Excess of lime also is well known 

 to accentuate attack. 



(3) There is great difficulty in the administration of the 

 Corky Seal) Order. The disease is not always easy to recognise 

 with certainty, even by experts. Tn inspecting consignments of 

 seed, slight infections would be easily overlooked, and, owing to 

 the similarity of mild cases to attacks of Conimon or Brown 

 Scab, examination with the microscope is often necessary. 

 This would entail an increase in the number of inspectors and 

 inxolve extra expense. a 2 



