EXPERIMENT STATION WORK WITH INSECTICIDES. 277 



In Minnesota " elaborate experhneiits along this line have been car- 

 ried out. In this work carbon bisulphid was thoroughly tested. It 

 was found that the insect in all its stages could be destroyed by spray- 

 ing with carbon bisulphid. Ai)parently, however, it was not practical 

 to kill the eggs by fuuiigation with carbon bisulphid, and it was, 

 therefore, necessary to repeat the process after about ten days in order 

 to kill the larva? which hatch from the eggs which were not destroyed 

 during the first fumigation. All stages of the pest except the eggs 

 are killed by exposure for forty-two hours to carbon bisulphid at the 

 rate of 1 part to 10,000 parts of atmosphere. A greater strength of 

 the gas is necessary to destroy the pest in the center of tight sacks. 

 The freezing process of destroying the Mediterranean flour moth is 

 not practical. The insect in all its stages is destroyed by exposure 

 for six and one-half days to a temperature of of 3 to 5° F., but in 

 all elevators and mills there are many protected corners and cracks 

 in which this temperature might not be reached, and where conse- 

 quently a number of the insects would be left to reinfest the milling 

 products. The use of carbon bisulphid, however, is not always effec- 

 tive against the Mediterranean flour moth. Kecent experiments at 

 the Minnesota Station show that hydrocyanic-acid gas may be used 

 with more effective results. In one case a large mill was fumigated 

 by this means, using a ton of cyanid and 14 tons of sulphuric acid.' 



COIIN BILLBXJGS. 



Throughout the corn belt the corn billbng {SpheiwpJiorus par- 

 vvhis) is one of the important enemies of this crop. Recently the 

 Illinois Station '^ has developed a practical remedy for controlling 

 this pest. It was observed that the insect was most injurious Avhen 

 corn was planted on ground which had previously been in timothy 

 and had been plowed shortly before planting to corn. If such ground 

 is plowed in the fall, the amount of injury from billbugs is very 

 slight. It appears, therefore, that most of the injury from corn 

 billbugs may be prevented by early fall plowing. 



THE CORN ROOT-APHIS. 



The corn root-aphis is another serious enemy of corn. At the 

 Illinois Station '' an effective and practical remedy was recently de- 

 veloped. It was found that the early cultivation of soil in which 

 corn is to l)e i)lanted greatly reduced the number of nests of ants 

 which care for the corn root-aphis and consequently reduced the 

 danger of the pest. In one instance disking three times and harrow- 



o Minnesota Sta. P.nl. SS. ftlUinois Stn. P.ul. 104, pp. O.I-IOl. 



'• Illinois Sta. Pul. 104. PI., loii-iu::. 



