1891.] Entomology. 67 
treated trees of the Wild Goose variety had dropped all their fruit, as 
had the untreated trees of the same kind. Another treated tree of a 
yellow variety was loaded with plums, of which only fifteen per cent. 
were stung, and those not badly. The fourth tree treated was a purple 
variety, and had not less than seventy-five per cent. of its fruit badly 
stung.” 
Professor Cook wisely refrains from drawing any conclusions from 
an experiment of such doubtful value. It is extremely probable that 
the Curculio had nothing to do with the dropping of the fruit on the 
Wild Goose trees, as this variety nearly always drops its fruit just after 
it sets, on account of the lack of fertilization of the ovule. The two re- 
maining trees about offset each other, one having seventy-five per cent. of 
wormy fruit, and the other eighty-five per cent. ofsound plums. The trees 
were sprayed but once, and a period of more than three months ap- 
parently elapsed during which no observations were made upon them. | 
In 1888 Professor Cook repeated the experiment, apparently on a 
slightly larger scale. An unrecorded number of cherry trees and three 
plum trees were sprayed with London purple, one pound to roo gallons 
of water, June 6th, 12th, and zoth. The sprayed fruit of both kinds 
matured with little or no Curculio injury, while ‘‘ cherry and apple 
trees near by not sprayed suffered seriously.’’ The author gives the 
following conclusions : 1 
“From these experiments, and those of former years, I conclude 
that while one application will not save our plums and cherries, and 
prevent apples from being stung, two or three applications may be of 
. Signal advantage.” 
The experiments were repeated in 1889 ‘‘ with no success. All the 
trees were severely attacked and all the plums lost.” Nothing is said 
Concerning cherries. Professor Cook thinks he is ‘‘ warranted in the 
following conclusions ; ” 11 
“‘ The arsenites will protect against the Plum Curculio if they can be 
kept on the tree or fruit. But in case of frequent rains the jarring 
method will not only be cheaper but much more effective.”’ 
Finally, in 1890 Professor Cook issued as Bulletin No. 66 of the 
_ Michigan Agricultural College, an article entitled ‘‘ Fighting the 
Plum Curculio,” in which spraying is entirely repudiated, and “‘ the 
old reliable method ” of jarring is fallen back upon as “ the surest, 
Cheapest, and best method to banish the Curculio and save our plums.” 
As before, no details of experiments justifying such an entomological 
" Bull. No. 39, Mich. Agr. College, p. 9. 
11 Proc. Tenth Meeting Soc. Prom. Agr. Science, 1889, p. 28. 
