THE PEAR LEAF-WORM. 91 
WASHINGTON EXPERIMENTS. 
In Washington State, where the pear thrips is not to be considered, 
lead arsenate would appear to be the only logical insecticide to 
be used against the pear leaf-worm. It is less expensive than extract. 
of tobacco sprays, and easier to mix than oil sprays; besides, the — 
lead arsenate can serve a double purpose—that of controlling this 
worm and, at thesame time, thecodling moth. The first application of 
lead arsenate for the control of the latter is made when the petals of 
the pear blossom drop, and at this time the larve of the sawfly have 
reached the second instar. The injury done previous to this is 
negligible; it is only during the last two instars that the larve cause 
serious injury to the foliage. 
Mr. Zimmerman, in whose orchard the worst infestation occurred, 
used lead arsenate at the rate of 4 pounds to 100 gallons of water 
against the pear leaf-worm with excellent results, both in 1914 and in 
1915. The first year there was a very severe infestation of larvee 
and the application was made May 16, at the same time that the first 
codling-moth spray was applied to apples; this was too late for the 
pears, as the larvee already had devoured as much as a third of many 
of the leaves. However, it saved most of the trees from a severe 
defoliation, as is shown in Plate II, which pictures a tree of which 
the left half was sprayed while the right half was left unsprayed, the 
photograph having been taken on May 21, 5 days after the trees were 
sprayed. The difference was very marked. No definite count was 
made, but on the sprayed trees scarcely any living larve could 
be found, while many hmp and blackened remains were hanging 
from the partially eaten leaves. In the unsprayed portion of the 
tree just mentioned, which served as a check, larvee were numerous, 
and large numbers of them were dropping to the ground to spin their 
cocoons. 
In 1915 the infestation was not so severe, owing to the control 
measures of the year before. The orchard was sprayed on May 6, 
earlier than in 1914. Lead arsenate was used at the same strength 
as before, that is, 4 pounds to 100 gallons of water. This applica- 
tion effectually checked the ravages of the larve, and the trees suffered. 
very little injury. 
In 1915 a small experiment was performed with nicotine sul- 
phate, 40 per cent concentration. Infested twigs were placed in 
water andsprayed witha hand pump. April 27 a twig with 10 second- 
instar larvee was sprayed with the nicotine sulphate at the rate of 
1 to 1,200, with the addition of a little fish-oil soap. On April 28 
the twig was examined and all the larve found dead. , The larvee 
on a check twig were still alive. On this date a similar twig was 
sprayed in the same way, except that the nicotine sulphate was 
