April, ’24] 
FROST & CRAIGHEAD: APPLE LEAF-HOPPER CONTROL 
263 
During the summer of 1923, many orchardists suffered serious losses 
through the spotting of the fruit by the liquid discharged by the hoppers. 
The spotting was so abundant in some orchards as to seriously mar the 
quality of the fruit. Rains during the latter part of the summer 
washed these spots forming sooty streaks and ruining the appearance of 
a large percentage of the fruit. 
A new and serious type of injury was also noted on the fruit. The 
nymphs puncture the fruit with their beaks. Later in the season these 
punctures crack open giving the fruit a mottled or russeted appearance. 
This type of injury was particularly noticeable on york imperial, stay- 
man winesap, grimes golden and pound apples. On the stay man the 
scars were usually triangular in shape probably having their origin in the 
lenticles. On the vorks the scars were rod shaped often resembling a 
fruit injured by rubbing against a limb. 
Control Measures 
During the past season, some preliminary control measures were 
taken. Nicotine dusts were applied during the month of June with 
encouraging results. The dusting was done on fhe twelfth and four¬ 
teenth of June. This was a trifle too late as nearly one third of the 
nymphs had transformed to adults. A dust two weeks earlier would 
have yielded better results. The afternoon was selected for the work.. 
At that time the air was warm and dry and there was little wind. It 
was found necessary to select ideal conditions for the dusting work. 
Under these conditions a high percentage of control was affected. 
When the air currents were strong it was found impossible to maintain an 
atmosphere of nicotine dust about the tree long enough to give satis¬ 
factory results. The work was done with one of the latest types of 
dusting machines. Two types of dust were used; a 2% nicotine 
sulphate dust with hydrated lime as a carrier and free nicotine dusts 
with clay as a carrier. The percentage of both nymphs and adults 
killed by the nicotine dusts ran exceedingly high. 
In making the test, counts were made of the numbers of leaf-hoppers-, 
per leaf before and after dusting. These counts were taken from the 
inside as well as the outside of the tree and from the lower as well as the 
upper surface of the leaves. The first counts were made in the morning, 
the dusting was done shortly after noon and the second leaf-hopper- 
counts were made a few hours after dusting. 
Immediately after dusting a tree, the leaf-hoppers commenced to fall" 
to the ground. In badly infested orchards they sounded like rain as 
