4 SOME INSECTS INJURIOUS TO TRUCK CROPS. 
present, but at a very low figure, eggs being seen on only 3 to 4 per 
cent of the larva?. Harpaline ground-beetles were abundant and 
Lebia grandis Hentz was undoubtedly a factor in keeping down the 
great increase of the potato beetle. 
REMEDIES. 
With regard to remedies, a considerable number of experiments 
was performed with a view to discovering the cheapest and most 
effective insecticide for controlling the potato beetle. Several plats, 
consisting of one-tenth of an acre each, were prepared for testing the 
effects of the poisons on the plants and on the larvae. An insight 
into the methods of research by which the results were obtained may 
be of value to the investigator, and a somewhat detailed account of 
the experiments with insecticides is given. 
EXPERIMENTS WITH INSECTICIDES. 
A plat of about 1| acres was selected early in the season and planted 
to potatoes, a single variety being used. The plat was divided into 
rows of such a length as to contain one-fortieth of an acre, four of these 
rows constituting a test plat of one-tenth of an acre. The plat was 
allowed to become thoroughly infested by beetles and larvae in several 
stages. The various plats were then numbered and treated with the 
different insecticides. The fertilizer treatment was the same in all 
cases, and as the ground on which the potatoes were planted was 
new, the yield could not have been affected by a residue of fertilizer 
remaining in the soil from the previous year. The poisons were 
applied with a knapsack sprayer. 
Experiment No. 1 . — One-half pound white arsenic and 2 pounds sal 
soda were boiled together in one-half gallon of water until dissolved. 
The mixture was used in the proportion of 1 pound of arsenic to 50 
gallons of water, with the addition of 6 pounds of lime per 50 gallons 
of solution, and was applied about 10 a. m. 
Twenty-four hours after spraying, the plat was examined and no 
living beetles or larvae could be found. At this time no damage to the 
foliage was apparent as a result of the arsenic, but two days later the 
potatoes showed extensive burning and scalding. The foliage was 
almost entirely killed by this application, and some time was required 
for the plants' recovery. 
Arsenic in this form is a very cheap insecticide but, on account of 
its effect on the plants, could not be used, although extremely 
effective in destroying the leaf-feeding insects. 
Experiment No. 2. — Commercial arsenate of lead was applied with 
Bordeaux mixture. Five pounds arsenate of lead paste with 4 pounds 
of copper sulphate and 6 pounds fresh lime were used in 50 gallons of 
water. The day was bright and clear with a southwest wind and a 
temperature of 85° F. 
