Agricultural Research l\ Xk\\' Hampshire 41 



in the department's research have been tested in aerosols and one of them 

 looks promising, since it can be incorporated in liquefied Freon without 

 added solvent, and since it gives high mortality of the test insects at rela- 

 tively low concentrations. 



During the summer of 1944. DDT, in the form of sprays and dusts, 

 was used in a number of plots for the control of potato insects. General- 

 ly speaking, DDT dust gave more satisfactory' control of potato insects 

 than did the DDT spra\'. The spray applications appeared to be about 

 as effective as standard calcium arsenate applications. (In the DDT 

 sprays the material used was Gesarol AK 20 at the rate two pounds per 

 100 gallons of water.) 



A dust containing 3 per cent DDT gave especially good results 

 against potato flea beetles, and Colorado potato beetles. In some plots 

 the dust gave an increase in yield of 63 bushels per acre over that obtained 

 in plots sprayed with calcium arsenate at the rate of six pounds to each 

 100 pounds of Bordeaux mixture. 



In the control of potato aphids, DDT appeared to act quite slowlv. 

 It could not be depended upon to reduce a very heavy population of 

 aphids within any reasonable period of time However, it is anticipated 

 that aphid control in potato fields might be accomplished if applications 

 were begun early in the season and were repeated several times, so as to 

 prevent the initial buildup of aphid population. It is planned to continue 

 this sort of experimental work during the forthcoming season. 



W. C. O'Kane, J. G. CoxKLiN. L. C. Glover, W. J. Morse 



Penetration and Toxicity of Ovicides 



In order to determine the effect of the addition of DDT to dilute oil 

 sprays in the control of European red mite on apple. DDT in the form of 

 Gesarol AK 20 was combined with Niagara No. 6 dormant oil in delayed 

 dormant apphcations at the Horticultural Farm orchard. Three plots 

 were used in the experiment. Plot No. 1 received a standard application 

 of 3 per cent oil, only. Plot No. 2 received an application of three gal- 

 lons of oil plus two pounds of AK 20 per 100 gallons. Plot No. 3 received 

 one gallon of oil plus two pounds of AK 20 per 100 gallons. Complete 

 control of the European red mite was obtained in all three plots, while 

 near-by trees, unsprayed, showed severe damage by the red mite. The 

 degree of control obtained is attributed to the fact that red mite eggs 

 were just beginning to hatch at the time the sprays were applied, and 

 were paricularly susceptable to oils of low concentration. Although the 

 DDT did not decrease the toxicity of the oil spra\s, it did not add great- 

 ly to the toxicity of the oil. 



W C. O'KaXE, J. G. COXKLTN 



Insect Record 



In the summer of 1944, an outbreak of the lesser migratory grass- 

 hopper caused serious damage to hay and grain crops in the Merrimack 

 Valley. Injury was accentuated by drouth conditions and resulted in a 

 total loss of crops in some instances. 



