10 
COLORADO EXPERIMENT STATION. 
itself, and the “gummy” peach is the result. Projecting bits or 
masses of exuded gum appear on the surface, and from their appear¬ 
ance and impaired keeping qualities they are rendered unfit for mar¬ 
ket. Some peaches containing larvae of the twig-borer find their 
way into boxes to be marketed on account of having the borer deep 
in the peach or within the pit without external signs of habitation. 
Such fruit, however, is first to soften and decay, and should be ex¬ 
cluded, if possible. 
Control —At Grand Junction last spring I received many inquir¬ 
ies from peach growers as to the best measures of twig-borer control. 
So far as published accounts were available, contact insecticides, 
such as kerosene emulsion or lime and sulfur wash, were the ones 
considered most effective. The previous spring Mr. Frank Berger, 
of Palisade, and a few other growers of that place, had used arse¬ 
nate of lead as a spring spraying, instead of the lime and sulfur 
wash ordinarily used, and reported no injury from twig-borer follow¬ 
ing. As none of these orchards had portions left with no spray, I 
could not determine for certainty whether the favorable results re¬ 
ported by these orchardists was due to the effectiveness of the spray 
or to the lack of original infestation by the twig-borer. 
To determine this it seemed necessary to prove the value of the 
arsenical spray by an experiment carried on in an orchard where a 
considrable portion was left untreated, which was done in the five- 
year-old peach orchard of ninety-two trees belonging to Mr. S. L. 
Carson, at Palisade, where a portion was sprayed with arsenate of 
lead, another with the lime and sulfur wash, and a third part left 
with no spray. The arsenate of lead was used at the rate of 5 pounds 
of the paste to 50 gallons of water. The lime and sulfur wash 
was used at the rate of 15 pounds lump lime and 15 pounds flowers 
of sulfur per 50 gallons of water, the two ingredients being boiled 
together in a small amount of water for forty-five minutes, then 
diluted with enough cold water to make fifty gallons of spray. The 
spraying was done with a hand pump and sprayed trees thoroughly 
coated over all bark and twig surface. The two sprays, as applied, 
were of about equal cost—each a trifle over 1 cent per gallon, exclu¬ 
sive of cost of preparation. The arsenate of lead spray was far less 
inconvenient, and was quicker in preparation, and was also more 
pleasant to prepare and apply. 
The spraying was done on April 14, at which time the majority 
of the blossom buds showed their pink tips, but as a rule were un¬ 
opened, with the essential parts of the blossom still concealed by the 
folded petals of the flower. Some varieties, however, in each plat 
were farther advanced and some with as many as 87 per cent of the 
blossoms open. 
The comparative insecticidal values of the two sprays were ap¬ 
parent through the season from the number of injured twigs per 
tree, and also from the number of gummy peaches per tree occur¬ 
ring upon each plat. 
