Agricultural Research in N. H. 31 



Chemicals showing marked synergistic action were phenyl cellosolve, 

 cellosolve salicylate, phenyl salicylate, butyl carbitol acetate, 2-ethyl hexan- 

 diol, and six of the high molecular weight phthalates. Within the series of 

 salicylates tested, the order of synergistic activity showed direct increase in 

 molecular weight of the compounds. The higher the molecular weight the 

 greater the synergistic activity. Phenyl salicylate and cellosolve salicylate 

 showed greater synergism than did Sesame oil, but were somewhat inferior 

 to piperonyl cyclohexanone. 



It is planned to investigate synergists further with the possibility of in- 

 creased toxicity of pyrethrum rotenone and Lethane. As opportunity offers 

 it is also planned to investigate possible synergists for DDT and bezene hex- 

 achloride. 



In co-operation with the Crop Protection Institute, benzene hexachloride 

 has been investigated to determine its toxicity against various insects. In 

 preliminary tests benzene hexachloride gave promising results in the control 

 of bark beetles attacking freshly-cut pine logs. This work is of considerable 

 interest in view of the present threat of the Dutch elm disease, which is trans- 

 mitted by a bark beetle and which might conceivably be susceptible to in- 

 sccticidal applications, thus reducing the chances for spread of this important 

 disease. 



A dust containing one per cent of the gamma isomer of benzene hexa- 

 chloride proved ineffective in an attempt to control a heavy infestation of 

 the eye-spotted bud moth of apple. The application was made after many of 

 the budworms were already tightly enclosed in rolled leaves. 



During the past year an improved method of applying dusts in the lab- 

 oratory was developed in co-operation with the Crop Protection Institute. 

 The method involves the use of a partial vacuum in obtaining a very uniform 

 deposit of dust on potted plants, or insects in a bell jar. Dust deposits ap- 

 plied by this method appear to be remarkably uniform, and the method has 

 already found favor with other laboratories engaged in research of the in- 

 secticides or fungicides. Plans are underway to attempt to secure this same 

 kjnd of uniform deposit when liquid spray applications are used. 



During the year, apparatus has been devised for investigating the use 

 of flourescent materials in photographing spray deposits as a means of ob- 

 taining more accurate appraisal of new insecticides and fungicides applied 

 under field conditions. 



J. G. CoNKLiN, W. C. O'Kane, R. L. Blickle, W. J. Morse 



Insect Record 



Scouting of birch stands in Coos County was carried on in 1946, to de- 

 termine to what extent the bronze birch borer was causing damage. The in- 

 sect was found to be present in outbreak form, particularly in the Pittsburg 

 area. Some stands of considerable size were found to be as high as 90 per 

 cent infested with the borer; although mortality is not yet serious, it is be- 

 lieved that prompt salvage of infested trees will be necessary if much of the 

 yellow birch in the area is to be saved. 



Light trap larval and adult biting collections of mosquitoes were made 

 during the summer of 1946. A total of seven genera and 29 species were 

 taken. The most common species in point of numbers were Mansonia per- 



