SPRAYING WITH ARSENICALS. 181 
method after a second year’s trial, and as in this case, so also with regard to pear blight, 
I first put forth my theory of the latter in the Fruit Recorder, as being among the papers 
with the largest circulation and as most likely to meet with the largest results and atten- 
tion; and in November, 1877, when I classified pear blight as a zymotic disease and 
suggested an investigation upon this theory it was apparently at once taken up by 
Prof. Burrill and continued by other professors of microbotany, and to-day the 
bacterian theory of pear blight has become an established fact and the prevention or 
modification of the disease may be looked upon with a degree of certainty at no distant 
day. Now for some one to step forward and supplant the first stepping-stone to the 
proper study of pear blight as it appeared in the Recorder of 1877. 
In the spring of 1885, Dr. Riley, in an address before the Missis- 
sippi Valley Horticultural Society, at New Orlenas, La., discussing 
the feeding habits of the beetles, urged experimentation with arseni- 
cals in this direction, as promising fair results—not, however, in the 
very nature of the case as satisfactory as in the case of the codling 
moth. 
During the summer of the same year Dr. S. A. Forbes began ex- 
periments in Illinois in the control of the codling moth and apple 
and plum curculio, reporting the results in the Prairie Farmer of 
December 19, 1885, and also in the Transactions of the Illinois State 
Horticultural Society for that year, which appeared from the press 
the following year. Paris green and London purple were tried on 
apple. Paris green was used at the rate of three-fourths ounce to 
21 gallons of water (equaling approximately 1 pound to 50 gallons), 
the metallic arsenic present being 15.4 per cent. Two trees were 
sprayed eight times during the season, the first applications being 
made on June 9 and 13, respectively. Two trees of the same variety 
of apple were left unsprayed for purposes of comparison. 
In regard to the effect of the treatment of the curculio, Prof. 
Forbes says: , 
Of the 1,975 apples from these two poisoned trees which were examined for the 
curculio injury, 542, or 27.3 per cent, bore the brand of the insect’s beak, while of the 
1,172 obtained from the check trees, 602, or 57.3 per cent, had been so injured, the 
ratio of apples punctured by the curculio on the poisoned trees being half as many 
times on the trees that had not been sprayed. A careful inspection of our tables 
showed that this was a fact apparent throughout the season. Considering the picked 
apples only the results are somewhat more favorable, and if the fallen apples are also 
taken into count, the percentage of those damaged by the curculios on the check trees 
being 76.5 and upon those sprayed with Paris green 34.4 per cent. 
During the summer of 1886 Prof. Forbes continued his experiments 
with arsenicals in the control of the codling moth, particularly com- 
paring Paris green and white arsenic, noting also the effect of the 
treatments on the curculio. 
These experiments by Prof. Forbes seem to be the first careful 
ones made to determine the value of arsenicals in curculio control. 
In an earlier part of his article Prof. Forbes notes that Paris green 
had been very generally recommended. 
