1921.] 



The Control of Onion Smtt. 



449 



In addition to the above trial, 21 varieties of onions and 11 

 varieties of leeks were tested. 



All varieties which have been tried, both of onions and leeks, 

 have proved to be susceptible, thouf]jh the latter were much less 

 so than the former. It is a curious fact that at Wylam-on-Tyne 

 leeks have always proved to be only slightly susceptible to smut, 

 whereas at Crookliam-on-Tweed the contrary is asserted to be the 

 case. Until the above trials were laid down it seemed iikely 

 that this marked resistance of leeks to smut at Wylam was con- 

 nected with the fact that at this centre, leeks have been gi'own 

 for seed (known as Wylam seed^ for many years ; in this way an 

 resistant variety might hav^ been produced by unconscious 

 selection. The result of the trials, however, appears to have 

 negatived this view, and renders it extremely difficult to account 

 for the difference in susceptibility of leeks at the two centres. 



White Lisbon " Onion (the variety used throughout these 

 experiments), though extremely susceptible, is so rapid a grower, 

 that, given good growing weather, it probably suffers less than 

 any other variety. In bad seasons, however, the entire crop 

 may be lost, e.g., in one case the normal exjiedation ums a crop 

 of fcv thousand hnrjchcs of five plants each — the actual crop 

 pulled iras 200 plants. 



Formaldehyde Experiment. — On 31st July, 1920, a trial 

 was laid down by the Ministry of xlgriculture and Fisheries at 

 Wylam, under the charge of the District Inspector. The object 

 was to test the value of the formaldehyde treatment which has 

 proved of considerable efficacy in the United States. 



A quarter of an acre of affected land was sown with White 

 Lisbon seed by means of a Planet Junior drill, and a solution 

 of formaldehyde (one pint to sixteen gallons of water) was applied 

 immediately after to the open drill by means of an ordinary 

 watering can with a fine rose. Three and a quarter pints of the 

 solution were used, costing 17s. lOd. The drills were covered, 

 but wet weather setting in prevented rolling. Anotlier poi-tion 

 of the plot (50 sq. yd.) was sown in the same way, but without 

 forma Idehyde treatment . 



The ground was inspected 6 weeks later. On the untreated 

 portion 95 per cent, of the plants were affected with smut, very 

 few showing signs of being able to recover. On the treated 

 portion careful countings showed that 20 per cent, of the plants 

 were infected, or had been infected. Some were apparently 

 dying, but others appeared to be recovering. The treated portion-. 



E 



