April, '21] 



headlee: dusting for insect control 



219 



of the dust for control of curculio is certainly true under the average 

 New Jersey experience, not only on apple, but also to a less extent on 

 peach. 



If the rainfall is, as it seems to be, a limiting factor in the effectiveness 

 of dust applications as they are at present made, and if distribution of 

 rainfall is such as to minimize the effect of dust applications by washing 

 them from the tree, the writer thinks it entirely fair to conclude that 

 the dust applications for control of curculio and codling moth are not 

 as certain to give good results even in territories of low rainfall (for even 

 in such areas the distribution may in any year wash off the dust at 

 critical times )as are liquid sprays. 



Speaking from the standpoint of peach growing in New Jersey, the 

 writer wishes to say that he regards the sulfo-arsenical lime dusts as 

 nearly equivalent to the self-boiled lime sulfur arsenate of lead liquid 

 sprays, but that in dealing with apple growing he regards the sulfo- 

 arsenical dusts as not comparable in efficiency with the liquid sprays and 

 that he can recommend them only as an adjunct where for any reason 

 the liquid spray cannot be applied. 



During the season just passed certain data on the effect of nicotine 

 carr>ang substances upon apple leaf hopper and apple plant lice have been 

 collected with a view to seeing whether dust applications could not be 

 used for the control of these insects. The following table will serve 

 to show the effect of a 90-10 sulfo-arsenical dust impregnated in one 

 case with .5 of one per cent, nicotine, in another case with 1 per cent, 

 nicotine and still another case with 3 per cent, nicotine as compared with 

 a commercial lime sulfur (1 to 40) liquid spray, to which nicotine has 

 been added at the rate of ^ of a pint to 50 gallons. 



Examination of the following table on leaf hopper results shows that 

 the 90-10 dust impregnated with 1 per cent, nicotine is as effective as 

 that charged with 3 per cent, and only a little more than one-half as 

 effective as the liquid treatment. 



Date 



6-8-20 



Block 



Row 



2 

 2 

 1 

 .3 



2 



2 



Checks 



Xo. cf Leaves 



1 ,000 

 1.000 

 1.000 

 1,000 

 1,000 

 1,000 

 1,000 



No. of 

 Hoppers 



1.5 



7 



7 



32 



76 



4 



108 



Killing Agent 



Nicotine 5 percent, applied 



" 1% 



" 3% 



" 3% possible floating 

 Owner's treatment 

 Nicotine K pts. to 50 gallons 

 None 



From Demonstration Blocks at Maple Shade 



The following table will serve to show the comparative effects of a 

 90-10 sulfo-arsenical dust impregnated with .5 of one per cent, nicotine; 



