cent w. p.) ; both materials gave satisfactory control for a period of one 

 month following a single application. ]\Ialathion has a distinct advantage 

 over Parathion for the average grower, inasmuch as it is much safer to 

 handle and will give very good results in controlling other important apple 

 insects, as well as mites. 



An attempt was made to control horse flies and horn flies on dairy 

 cattle. Two materials were used for this purpose : Sulfoxide- Pyrexcel wet- 

 table powder and Sulfoxide-Pyrexcel emulsion. Under field conditions it 

 was found that both materials protected the animals from horse flies for 

 three days. The species of horse flies involved were Tebaniis typhus and 

 Tebanus lasiopthalmns. Both of the insecticides used gave protection to 

 cows from horn flies for nine days during the period when untreated ani- 

 mals were more or less continuously heavily infested. 



Control of horse flies in the University Livestock Barn was attempted 

 by the use of Malathion sugar baits. It was found that the sugar bait method 

 was effective in reducing fly populations satisfactorily, providing the baits 

 were replenished every three days during the season when flies were par- 

 ticularly troublesome. 



Fly breeding in manure was controlled effectively by the application 

 of Malathion sprays at intervals of four days. 



J. G. CoNKLiN, R. L. Blickle, W. T- Morse 



Factors Affecting the Action of Acaricides 



An attempt was made to determine whether the two-spotted mite, 

 reared under different humidity conditions, would exhibit any difference in 

 susceptibility to acaricides. Acaricide tests were run on six different mite 

 populations which had been reared under constant humidity conditions of 

 10 percent, 28 percent, 44 percent, 60 percent, 75 percent, and 80 percent, 

 respectively, and under temperature conditions ranging between 75° F. 

 and 80° F. It was observed that mites reared at humidities between 10 per- 

 cent and 50 percent developed faster and in greater numbers than did those 

 at the higher humidities of 75 percent and 80 percent. In these tests there 

 were no significant differences in susceptibility to the acaricides under the 

 6 different humidities. 



R. L. Blickle, W. J. Morse 



Forestry 



Soil-Yield Relationships of White Pine in Southern New Hampshire 



Since 1952 data has been taken on Z7 white pine sample plots. The 

 mensurational characteristics of the forest and the properties of the soil 

 have been recorded for each plot. 



A preliminary set of site-index-curves for white pine has been pre- 

 pared. Various regressions with their correlation coefficients have been cal- 

 culated and it was found that a strong correlation exists between certain 

 soil properties and site-index. As more plots are established in the coming 

 year, it is believed that stronger correlations will be found. 



B. HuscH, W. Lyford 

 28 



