"ENTOMOLOGY. 969 



completely after being allowed to ,«tand for more than 2 days. A winter treatment 

 was given to plums, pears, and eherries. Tlie trees were sprayed December 22-24, 

 during an average temperature of 39° and accompanied with clou<ly weather. The 

 weather during the following week was also cloudy. In the same orchard a spring 

 application was given April 18, at a temperature of 52°, with cloudy weather during 

 the following week. Some of the trees were given both the winter and spring treat- 

 ment, on December 24 and April 18. The winter treatment injured none of the plum 

 trees when the 25 per cent emulsion was'used, but all the trees were injured or killed 

 l)y 40 per cent mixture. Old trees were more seriously affected than younger trees. 

 Pears and cherries were uninjured. Plums were even more seriously injured by the 

 spring treatment, but the ]iears and cherries were unaffected, even by the (JOjiercent 

 mixture. A combination of winter and spring treatment caused more damage to the 

 trees than either single application. The spring treatment proved to l>e less injurious 

 than the winter treatment, while l)oth treatments together proved fatal with all 

 mixtures above 25 per cent. 



In experiments to determine the effect of crude petroleum upon hibernating scales 

 a number of pear trees were sprayed October 23, with a temperature of 64° ; the week 

 following the application was clear. Other pear trees were treated in winter and spring. 

 The trees were rather badly infested with the scale. In these experiments it was 

 found that a 25 per cent enmlsion could not be depended upon to kill dormant scales, 

 while a 40 percent mixture gave satisfactory results. Xo injury was observed on any 

 of the trees which were sprayed once, although some were much weakened by the 

 scale. Trees w'hich were sprayed twice with a 60 per cent solution or with undiluted 

 petroleum were killed or seriously damaged in every case. 



Experiments were undertaken in spraying large apple trees to determine the effi- 

 ciency of crude petroleum applications upon large trees. Applications were made on 

 some of the trees in winter, and on others in the spring. The 25 per cent mixture 

 had no effect on the scales and some live scales were found on trees sprayed with a 

 40 per cent mixtiare. This was probably due to the practical impossibility of com- 

 pletely covering large trees. Experiments on peach, pear, and apple trees which 

 were given a winter treatment showed that the scale was not killed by 25 per cent 

 mixture, while the 40 per cent mixture was effectual. Peach trees were somewhat 

 injured by a 25 per cent mixture. From these experiments it is concluded that 

 peach and plum trees are more sensitive to crude petroleum than apple, cherry, or 

 pear trees, and that a 25 per cent mixture of crude petroleum can not be depended 

 ujion to kill hibernating scales. 



A plum orchard was treated in the spring, partly with a resin wash and partly 

 with so-called government whitewash. The trees were sprayed April 12, with an 

 atmospheric temperature of 47°. Neither treatment had any effect on the scale. 



Fumigation experiments with ]n/(Jror;/(tnic-acid gas (pp. 188-210). — Experiments were 

 conducted to determine the effect of the gas on healthy buds and the strength of gas 

 required to destroy hibernating scales. Buds were fumigated in box fumigators and 

 the amount of cyanid used varied from 0.18 to 0.3 gm. per cubic foot of space. Apple 

 ])uds were not appreciably affected by the treatment. Cherry and pear buds suffered 

 a slight injury from the gas. Peach buds were considerably injured when 0.3 gm. of 

 i-yanid per cubic- foot was used. Plum buds were practically unaffected. In exjieri- 

 ments to determine the effect of gas upon the scale, pear, peach, and plum trees were 

 fumigated. In these experiments it was found that fumigation with gas at a strength 

 less than 0.3 gm. of cyanid per cubic foot of space had no effect on scales when 

 applied in the winter. In the spring the gas was much more effective, killing the 

 scales when 0.18 gm. of cyanid per cubic foot of space was used. In the authors' 

 opinion the principal advantage of fumigation over other treatment is iu thorough- 

 ness, but that it is expensive if used upon large trees. 



Notes are given on other insecticides, including whale-oil soap and crude petroleum 



