89 
THE COTTONY MAPLE SCALE: AN UNUSUAL OUTBREAK, AND 
EXPERIMENTS WITH INSECTICIDES. 
By S. ARTHUR JCHNSON, Fort Collins, Colo. 
Contrary to general experience the cottony maple scale (Pulvinaria 
énnumerabilis Rathv.) has done serious injury in Denver for several 
vears past and gives promise of renewed ravages during the coming 
summer. The scale is widely distributed over the city on the soft 
maple (Acer saccharinum) shade trees in the parks and streets. In 
a number of localities the permanent injury has been severe. ‘Two 
winters ago the time of one man was employed for.two weeks cutting 
out and removing the dead limbs from a park covering one block. 
In this same park last winter the under surfaces of many limbs on the 
soft maples and black locusts (7ebsnia pseudacacia) were literally 
coated with the scale. Here the Colorado Agricultural College, in 
conjunction with the superintendent of parks, conducted a number of 
experiments for the purpose of discovering an effective winter treat- 
ment. So far as the writer is aware very little therough work has 
been done in this hne. 
The advantages of a winter treatment are indicated both by the 
condition of the trees and by the life history of the insect. The 1m- 
mense numbers of the pest would make it necessary to spray thor- 
oughly both surfaces of the leaves in summer, which is a_prac- 
tical impossibility with trees of dense foliage which are often 30 
or more feet in height. Moreover, it would seem that the life 
history of the insect would necessitate more than one application of 
the spray. Doctor Howard,¢ in giving the jife history, says: 
The young hatch early in summer, usually in the month of June, but occasion- 
ally at least as early as May 22. ‘The hatching period usually extends on into 
le 
early July, but may last until August. * * * In the course of a month they 
undergo a molt and begin to secrete a certain amount of wax from the dorsal 
surface of the body. 
It thus appears quite possible that some of the first-hatched insects 
may molt and become protected with scales before the last cf the 
eggs have hatched. Professor Gillette ° has expressed the opinion that 
after the wax is formed sprays of greater strength will be necessary. 
The leaves of the soft maple appear to be quite sensitive to the greater 
strengths of contact imsecticides. 
EXPERIMENTS WITH INSECTICIDES. 
Shortly after I came to this station a quantity of badly infested 
maple twigs were received from Colorado Springs. At that time, 
under the direction of Professor Gillette, J made a number of experi- 
Eiken Sin Ole nite wOas. oepts, Acric pp. «16: 
6 Bul. 47, Colo. Exp. Sta., p. 33. 
