90 



species, those most affected l^eino; mentioned first in the list and those 

 least affected last: Soft or silver-leafed maple (Aeer dasycarpiim), 

 box elder {Acer ner/undo), linden (Tilia), Virginia creeper {Ampe- 

 lopsis qin/iqucfolia), bittersweet {CelaMnis scandens) , sumac (Rhus), 

 grape (Vitis), and willow (Salix). The summer food plants 

 observed have been S pirn a Van Houtteii^ S. argiita, and S. p7-iini- 

 folia; Philadelphns grdndiforus and P. coronarbi,^ : Cornus masoda. 

 C. siberica^ (J. stolonf'fera, and C. paniculafa; Rihcs aurevm and R. 

 sanguineum; Hydrangea; Rudbeckia; Syinphoricarpus racemosus 

 and S. vvlgaris; Syringa. several varieties; Viburnum, several varie- 

 ties. I have not found it upon eitlier the sugar maple {Acer sacchar't- 

 niiiii) or the Noi'way majDle (.1. plat(tnoide^) , even where these trees 

 were surrounded by the soft maples, except in such small numbers as 

 to be very inconspicuous. 



The work of sj^raying began the middle of July and continued 

 until September 1. The work was done under my constujit super- 

 vision by some senior students of the Michigan Agricultural College. 

 Two outfits on wheels with hand pumps were used, these being the 

 most c(mvenient in getting around from tree to tree. Both the 

 vermorel and bordeaux nozzles were used. Tlie trees sprayed were 

 mostly quite large, requiring a GO-foot hose to reach the top. The 

 operators wore fireman's oiled suits and liegan the spraying at the 

 top l)y climbing the tree, finishing at the bottom limbs. The work 

 was thoroughly done, so far as possible every leaf being covered. 



A\Tien I first took hold of this work I had expected to kill the in- 

 sects readily " with a weak kerosene emulsion." All the entomolo- 

 gists said this was the remedy, and my own fourteen years" experience 

 in practical spraying work told me the same thing. I began with an 

 S per cent kerosene enndsion, which was increased within a few days 

 to 10 i^er cent, then to l-!i, and finally to 15 per cent. Practically 

 none of the insects were killed with either the S or 10 per cent emul- 

 sions. An examination at Professor Forbes's office of leaves sprayed 

 with 12| per cent, some days after, showed that something over 50 

 per cent were killed, but the death of some of these was doubtless 

 from natural causes. The 15 per cent emulsion killed the greater 

 portion of the Pulvinaria. l)ut as this strength took practically all 

 the leaves off" the box elders, all from the lindens, and fully one-half 

 from the maples, the remedy was at least equal to the disease. A 10 

 per cent emulsion is all that can with safety be applied to tlie linden 

 or box elder, while a 124 per cent is all that can safely be applied to 

 the maple. 



In this connection some experience in the making of the emulsion 

 may be of interest. With 2,500 large trees to spray, scattered over a 

 large territory, the matter of making the emulsion was of consider- 

 able importance. But, as '* necessity is the mother of invention," it 



