796 
or summer, and making their burrows in 
some diseased tree deposit eggs which 
later hatch out into small white grubs. 
These are the larvae and remain in that 
stage through the summer and winter 
transforming to pupae and adults in the 
spring. The burrow, instead of being a 
series of short tunnels, is one large cavity 
with sides parallel and about the width 
of the full grown beetle. The sides ex- 
tend straight up and down and the eggs 
are indiscriminately deposited in a single 
mass. It is believed that this insect at- 
tacks only unhealthy trees. 
Shot Hole Borer or the Pear Blight 
Beetle 
Xyleborus dispar Fabricus 
H. F. WILSON 
There is no evidence that shot hole 
borers attack healthy trees in the North- 
west under ordinary conditions. 
Contrary to all reports from Europe 
and other parts of the United States there 
appears to be but one brood in this sec- 
tion. 
Classification 
The Scolytidae or engraver beetles, con- 
stitute a large and important group of 
Fig. 1. Heart Rot Fungus (Schizophyllum sp.) 
in Cherry, Issuing Through Burrows of 
(Xyleborus dispar). 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
beetles, many of which are very destruc- 
tive to forest trees. From an economic 
standpoint the members of this family 
may be divided into two general groups, 
those attacking healthy living plants and 
those attacking plants in a more or less 
sickly or dying condition. Observations 
made in the Northwest by the writer in- 
dicate that Xyleborus dispar is distinct- 
ly a member of the second group. 
History 
The widespread distribution of this in- 
sect in Europe would indicate its being 
native to that country. We can only 
theorize on the time and means of im- 
portation into the United States, but the 
time must have been several years prior 
to 1816. About this time the insect was 
attracting some attention in Europe and 
has continued to receive more or less at- 
tention by different writers up to the pres- 
ent date. 
Distribution 
This insect is found in nearly all parts 
of Europe and England and is gradually 
spreading into certain sections of Canada 
and the United States. 
Occurrence in the Northwest 
The first reported injury in the North- 
west which was in Clarke county, Wash- 
ington, came in 1901, where a grower 
thought that a great many prune trees 
were being killed by the beetles. At the 
same time-the beetles were working in 
Oregon near the city of Portland. In 
looking over the many inquiries which 
have been received during the past ten 
years it is interesting to note the gradual 
spread of the insect up the Willamette 
valley until now it is at Junction city, a 
distance of 125 miles south of Portland. 
At the present time the distribution ex- 
tends through the lower part of the val- 
ley on both sides of the river as far as 
the foot hills. The infested territory is 
increasing quite rapidly and the borers 
will in time undoubtedly spread over the 
entire western part of Washington and 
Oregon. From Portland to Salem, Ore., a 
distance of 53 miles, they are very abun- 
dant across the entire valley, and few dy- 
ing trees escape their attack. 
