24 Eighteenth Report State Entomologist of Minnesota — 1920 



disulphide in elevator boots showed that when seven pounds of carbon 

 di sulphide was used to one thousand feet of space most of the mites 

 were killed, but wherever they were in cracks or under several inches 

 of feed some of them survived. 



Several commercial s})rays used were effective when actual contact 

 was made with the mites. Mites completely covered with crude oil for 

 twenty-four hours were still living. An emulsion of from 15 to 20 

 per cent crude carbolic oil held in suspension bv a 0.1 per cent soap 

 solution was found to be a very efficient contact insecticide and was 

 used as a spray in corners, on floors, under elevator boots, and in 

 freight cars. The odor of this spray is objectionable but if it does not 

 come in contact with the flour or feed it does not seem to impart a 

 permanent odor to the material. 



Temperature was found to be very eft'ective for the control of 

 the mites. Tn laboratory experiments it was found that it was possible 

 to kill them by raising the temperature from 20 degrees to 48 degrees C. 

 in five minutes. At the end of the experiment one per cent of the mites 

 survived, but twenty-four hours later all were dead. When the tem- 

 perature was raised to 80 degrees there were absolutely no survivals 

 for even the shortest time. 



In conclusion, it would seem that mites are now so generally dis- 

 tributed in commerce that it is almost impossible for any establishment 

 to escape infestation if it is taking an active part in the interchange of 

 milled products. The method of preventing a general outbreak of these 

 pests would seem to be to keep the place perfectly clean, permitting 

 no accumulations of flour and other material. 



I'he storage of large quantities of flour, feed, or other susceptible 

 material should be undertaken only in clean dry places and then only 

 when the moisture content of the material is below 11 per cent. 



Mills or warehouses which are known to be infested should be 

 thoroly cleaned and all the refuse burned. If it is possible to heat the 

 building to a temperature of at least 120 degrees F. for several hours, 

 this is the best method of eliminating the mites. If the place is not 

 tight enough for heating, the floor and all cracks should be sprayed 

 with a 15 or 20 per cent carbolic oil emulsion. 



Literature Cited 



BeaUic. J. M. 



1918--Preliininary report on samples of flour submitted for bacteriological 

 examination by Professor Newstead,, Roj'al Society, Reports of the 

 grain Pests (War) Committee No. 2. London, 1918. 



