394 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
The results of the liquid spraying experiments with the twigs (Table 
I) show that one or more larvae were able to penetrate any of the coat¬ 
ings put on the new peach shoots and safely reach the center of the 
treated twig. None of the arsenical sprays employed stopped the 
larvae from entering. In a few instances some of the younger larvae 
seemed to be repelled by the poisoned material. 
The results of the dusting experiments (Table II) show a very small 
percentage of kill. With the exception of Paris green, two or more 
larvae in each set of tests entered the thoroughly dusted twigs. Paris 
green and magnesium arsenate showed the greatest percentage of kill, 
but these substances by themselves will injure peach foliage. ' Helle¬ 
bore, pyrethrum, tobacco lime and lime-sulfur dusts were also tried. 
None of these were effective except pyrethrum. This substance 
seemed to have a repellent effect. The larvae were not killed by the 
pyrethrum, but most of them refused to enter the twigs coated with 
this dust. 
Table III shows the response of larvae of known size to lead arsenate 
mixtures (lime and sulfur) when used in liquid and dust forms. The 
poison was thoroughly applied to immature peaches. A very small 
percentage of the 2-4 mm. and 5-6 mm. larvae, but none of the 7-9 
mm. larvae, were killed by the lead arsenate when it was applied in 
liquid form at the rate of 2 to 4 pounds to 50 gallons of water with the 
addition of casein-lime, 2 pounds to 50 gallons, acting as a spreader. 
All larvae smaller than 4 mm. were killed when placed on fruit 
coated with a fine dust of lead arsenate, 1 part and hydrated lime, 5 
parts or lead arsenate, 1 part and finely ground sulfur, 1 part. Of the 
two mixtures the lead arsenate and sulfur mixture was more effective 
with the larger larvae for it killed over 80 per cent of the 5-6 mm. 
larvae and 30 per cent of the 7-9 mm. larvae while the lead arsenate and 
lime dust only killed 60 per cent of the 5-6 mm. larvae and 2 per 
cent of the 7-9 mm. larvae. Finely divided hydrated lime by itself 
killed 40 per cent of the 2-4 mm. larvae and over 35 per cent of the 
5-6 mm. larvae, but none of the 7-9 mm. larvae. This substance does 
not act as a stomach poison, but the lime seems to make it difficult for 
the small larvae to crawl over a coated surface. The fine dust-like 
particles of lime catch on the ventral aspect of the body and also cling 
to the fine setae scattered over the various segments. This probably 
causes the thin skin of the larva to become very dry. Many of the 
larvae on the dusted fruit seemed to gradually decrease in size and 
shrivel before they died. 
The coating of dust on the fruit in the above experiments was prob¬ 
ably somewhat heavier than what might be found on the average fruit 
when dusted under orchard conditions. The results of the above dust- 
