Agricultural Research in New Hampshire 3 1 



It was found that cows with a long-standing, chronic streptococcal 

 mastitis are most difficult to cure and further information is necessary 

 before final recommendations for treatment with penicillin can be made. 

 Studies are now being conducted to determine whether one injection of 

 300,000 or 400,000 units of penicillin will cure this type of mastitis in- 

 fection. 



L. W. Slanetz, F. E. Allen 



ENTOMOLOGY 



Penetration and Toxicity of Contact Insecticides 



Early in 1945, the discover}' was made in the laboratory of the De- 

 partment of Entomology that the chemical compound hexachlorcyclo- 

 hexane possesses unusual properties as a contact insecticide. This dis- 

 covery took place just before receipt of a British reprint describing this 

 compound and noting its remarkable toxicity against insects. 



The compound is related to many others which have a ring structure 

 and which carry chlorine atoms in various positions. A series of com- 

 pounds of this general description had been under study in the depart- 

 ment. Several gave promise. But a simple benzene ring so treated as 

 to break the double bonds and to carry one hydrogen and one chlorine 

 atom on each carbon atom proved to be extraordinarily potent. This is 

 the compound which properly is designated as hexachlorclohexane but 

 which has received considerable publicity in the course of the year under 

 the name benzene hexachloride. 



Intensive work was started immediately on this compound. It was 

 found that a household spray kerosene will dissolve considerable of the 

 gamma isomer which is the active phase of the compound. Thorough 

 investigations proved that as little as 0.05 per cent of the gamma isomer, 

 when incorporated in a household spray kerosene, will bring about com- 

 plete kill of houseflies sprayed on the toximeter in the entomology labora- 

 tory. The addition of a small percentage of pyrethrum extract, or suita- 

 ble thiocyanate, produced a material giving quick paralysis of flies as well 

 as complete kill. 



Studies proved that several familiar organic solvents, such as xylene 

 and cychlohexanone, will dissolve substantial percentages of the com- 

 pound. By suitable choice of solvents the active isomer can be secured 

 in important amounts. 



Further investigations were directed toward reduction or elimination 

 of the unpleasant musty odor of the compound. Expedients were de- 

 vised for reduction of the odor, but this problem has not yet been fully 

 solved. 



^Meanwhile, the presence of an unpleasant odor is of no importance 

 in the use of the compound for control of many destructive insects, such 

 as grasshoppers, chinch bugs, leaf-eating beetles, and others. Applica- 

 tion on fruits such as apples was omitted until the compound could be 

 rendered free of odor. But it was found that applications on various 

 vegetables, such as tomatoes, cabbage, onions, and turnips, would not 

 bring about unpleasant flavor. 



