11 Nov.. 1918.] Weevil Pest of Grain. 697 



A detailed account of an experiment carried out at Birkenhead, 

 South Australia, on a stack of 8,500 bags of very weevily wheat, was 

 submitted. It was found possible to maintain an amount of from 

 10 per cent, to 15 per cent, of carbon dioxide continuously. Gas was 

 generated by passing air over a bed of hot coke in a furnace, the object 

 being to get as near as possible to a mixture containing 80 per cent, of 

 nitrogen and 20 per cent, of carbon dioxide with no free oxygen. The 

 purpose was to displace all the oxygen in the enclosure to render the 

 oxygen contents too low a percentage to support life. The experiment 

 was highly successful. No live weevils were found in any part of the 

 stack, but millions of dead weevils were seen. It thus appears that 

 weevils can be destroyed without handling the wheat. Though it is 

 impossible to make the malthoid enclosure absolutely airtight, the con- 

 tinuous passing in of nitrogen and carbon dioxide makes up for this, 

 and enables an asphyxiating atmosphere to be maintained. 



As regards the future, Dr. Hargreaves stated that he would be 

 pleased to co-operate with any bodies form,ed to undertake research 

 in other States, and to supply them with all information as to his 

 experiments. In reply to a question he stated that larvse and pupse, 

 as well as adult weevils, were killed by the process, but it was too early 

 to state whether the eggs were also destroyed. If not, it .would be 

 necessary to repeat the process a few weeks later, when the eggs had 

 developed. 



Mr. Lea pointed out that the experiments demonstrated two things: 

 Covering the stacks with malthoid was an absolute preventive, since 

 flying insects and mice could not penetrate it. Any insects already 

 in the stack are destroyed by fumigation, and thus the safe storage of 

 the wheat is assured. 



Mr. WiNTERBOTTOM cmphasizcd the importance of the results 

 achieved, and stated that the data obtained by the Department of 

 Chemistry ought to be published. He had been giving his whole time 

 to weevil work for the past fifteen months. It was important to adopt 

 preventive measures for new wheat; this should begin on the farm. 

 The danger arising from the mixing of a few bags of old wheat by 

 farmers with the new season's crop should be strongly emphasized, and 

 farmers required to deliver all their wheat in the one season, so that 

 it could be kept separate. One of the main' difficulties was that infec- 

 tion took place in country sheds. The grain on the floors of the sheds 

 — where these were of earth — contained weevil. The pest sometimes 

 appeared to be absent for a long while, and might break out after nine 

 months. He thought research was required as to the reason for this — 

 probably atmospheric conditions were responsible; 24 inches of earth 

 had been removed from the floors of some sheds, and yet weevils 

 were still emerging. Rats and mice carried grain containing weevils 

 down to the bottom of their holes, and it was impracticall}^ impossible 

 to remove weevil from those floors. Impervious floors of lime concrete 

 should be adopted in all sheds as essential; the superstructure was com- 

 paratively easily cleaned. Gutters placed round stacks were very 

 efficient weevil traps, but did not check the flying Rhizopertha. Old 

 dunnage was another source of infection, but it was found that immer- 

 sion in boiling water containing 1 per cent, of bluestone was fairly 



