10 Aug., 1917.] Damage by Insects tn Grain in Store. 495 



We have paid visits of inspection to the Darling TIarbor Wheat 

 Sheds, and to the Wheat Stacks at White Bay and Enfield. 



At our request, Mr. Guthrie, Chemist to the Department of Agricul- 

 ture of ]Nre\v South Wales, has determined the moisture content of 

 samples obtained on these visits. 



The prcsont report deals only with the Grain-Weevils (Calandra 

 granaria and C. oryzae), since these are the only insects attacking 

 stored grain whose destiuctive effects are serious enough to demand 

 special measures. 



The Development of Weevil in Wheat and the Increase in 

 Number of Weevils. 



The wheat when bagged in the fiaddock has no weevil in i*.. It 

 must come in contact with weevils after that before it becomes infeste'd. 

 This may happen in many ways. (1) Placing the grain in old bags 

 which have been weevil infested, or in store sheds or granaries where 

 there are weevil. (2) Weevils flying from grain stores, feed houses, 

 &c., and working their way into the bags and sacks. (3) Using material 

 in the construction of the foundations or the protection of the wheat 

 stacks, wood, sleepers, old bagging, &c. (4) Bringing bags of weevil 

 infested wheat in contact with or stacking near the sound wheat. There 

 must be a female weevil to lay her eggs in a grain of wheat before that 

 grain, of wheat is weevil infested. 



To the naked eye the grains may appear perfectly soimd, as the 

 minute hole into which the egg is inserted the grain does not show. It 

 is when the egg has developed through the maggot, pupa, and perfect 

 insect, and the latter has gnawed a bole through the side of the wheat 

 grain, that the damage to the grain is evident. Not only do the weevils 

 live and breed through their life cycle in the grains of wheat, but the 

 perfect male and female weevils feed upon grain themselves, so that the 

 damage is increasing all the time. 



The life history from the egg to the adult beetle varies from 19 to 

 22 days in a warm suitable temperature. In three months 40 weevils 

 multiplied themselves CO times, and counted out 3,056 weevils. 



Destruction of Weevils by Means of Poisonous Oases and 



by Drying. 



The various methods of treatment by poisonous gases which have 

 been tried either on an experimental or a large scale for the destruction 

 of insect pests in grain, are not applicable to bagged grain, save at a 

 prohibitive cost. 



Fumigation with Carbon Bisulphide. 



One thousand bushels of grain require 10 lbs. of carbon bisulphide, 

 and require to be enclosed for 24 hours, with a temperature of 70 and 

 not under 60. In badly infested wheat a second fumigation is required 

 to get rid of the eggs and weevil inside grain about three weeks later. 

 The cost of bisulphide is 7d. per lb., war rate. 



Fumigation with Hydrocyanic Gas. 



Experimented with this gas under similar conditions and tempera- 

 ture, and proved it to be not satisfactory, even with 48 hours. 



