rex: dutch elm disease eradication 
63 
Accordingly, we attempted to analyse all the available data pertaining 
to the work of the season of 1938 hoping that we might unearth some 
definite plausible reason for the sudden increase in the number of Dutch 
elm infected trees. 
During the fall of 1936 this project became deluged with a considerable 
number of W. P. A. workers, many of whom were of questionable accept¬ 
ability. However, an attempt was made to make the best of this situa¬ 
tion. Furthermore, an examination of some research data pertaining 
to tree injection work led to the adoption of a procedure, known as 
“silviciding” which should serve as a short cut to our goal. The purpose 
of the silviciding operation, which is the introduction of chemicals into a 
tree for the purpose of killing it, was to eliminate both from the stand¬ 
point of further scouting and from the standpoint of beetle multiplication, 
trees located in swampy areas or difficult mountainous terrain. This 
object was certainly commendable and judicious. Accordingly, during 
the fall of 1936 and the spring of 1937 approximately 600,000 trees 
located principally in swamps and mountainous areas were chemically 
treated for the purpose of eliminating them from the Dutch elm disease 
eradication program. Unfortunately the employed procedure was not 
100 per cent effective in the killing of the trees so treated. Many of the 
trees treated served as suitable habitats for bark beetle multiplication 
and it was predicted that we should expect an increase in the number of 
Graphium trees in 1938. 
About two weeks after the scouting season of 1938 had been under 
way reports from the various county offices reporting to our Bloomfield 
office, indicated that many confirmed Graphium trees occurred in close 
proximity to previously silvicided areas. This information immediately 
led to investigation as to the probable part played by these silvicided 
areas in the Graphium increase for 1938. Accordingly, a questionnaire 
carrying several requests for information was distributed to the field men 
soliciting information pertinent to the occurrence of Graphium trees in 
these areas. We attempted to ascertain the number of Graphium trees 
occurring within a one-mile wide band around each of the clean-cut 
silvicided areas. We also ascertained the number of Graphium trees 
occurring within the limits of D. T. silvicided areas. Of the total num¬ 
ber of 16,000 Graphium trees for the State of New Jersey in 1938 ap¬ 
proximately 10,500 occurred within the areas delimited above. An 
interpretation of these data will reasonably permit the conclusion that 
the bark beetles emanating from the silvicided areas to trees in the 
