24 LN2 ' .1. REPORTS OF DEPARTMENT OF AGRICULTURE, 1939 
-wvii.v 
An intensive survey was conducted during the summer of 1938 in 
New Hampshire, Vermont, and New York to determine the status of 
the European spruce sawfly. In cooperation with State agencies all 
the principal spruce areas in these three Si ed. Gen- 
erally speaking, the survey showed that the -piu ' was present 
wherever inspections were made, bul onli avy infesta- 
tion were found. Two of these wen- in southern New Hampsl 
one in central Vermont, and one in southern Vermont In 1937 
heavy infestations were Located in northern M e and reports from 
that State in 1938 indicated an increase. 
In cooperation with the Society for the Protection of New Hamp- 
shire Forests between 5 and 6 million cocoon p irasites Mi 
fuscipenms (Zett.)) were reared in 1938. Coloi opean 
parasite were liberated at every locality in New Hampshire, Ver- 
mont, and New York where sufficient larvae were found to indicate 
the possibility of successful establishment of the parasite. In Maine 
Large aumbers were also reared and liberated by State agencies. 
Eleven species of sawfly parasites were received in small numbers 
from the Canadian Government. About half these were liberated in 
heavy sawfly infestation-: the remainder were held for experimental 
work in laboratory rearing. Small numbers of i des of larval 
parasites and one cocoon parasite were successfully reared, but none 
of the species appears particularly adapted for large-scale propa- 
gation. 
In the spring of 1039 an intensive study of the -a wily and the 
factors influencing its abundance was undertaken. Permanent 
sample plots were established throughout the Northi eti rmine 
the effects of defoliation on different species of spruce, the difFen 
in life history of the insect under varying climatic conditions, and the 
fluctuation in population from generation to generation. 
INSECTS IN RELATION TO THE DUTCH ELM DISEAS1 
Collections of adults of the bark beetles Scolytus multii 
Marsh, and Hylwgopinus rufipes (Eich.) that were attracted to 
felled elm trees have been made uniformly from six points in New 
Jersey during L936, L937, and 1938. These bark beetles were cultured 
to ascertain the percentage carrying the Dutch elm disease fungus 
istometta ulmi (Schwarz) Buisman). The records are given 
in table 5. 
d that 
carrii d tin Dutch < Im 
. Itistriatus 
cull to 
ulmi 
rj log 
■omclla 

- 
Per 
■ **J 
3.3 
