20 NINETEENTH REPORT STATE ENTOMOLOGIST OF MINNESOTA—IQ22 
always found infested, sometimes heavily infested, and it is beyond 
question that a large proportion of the turpentine beetles in Itasca 
Park breed in them. Examination of a series of stumps cut in the 
winter of 1921-22 showed an average of 1.6 tunnels per stump for 
White pine and 13.5 for Norway pine. Summer-cut stumps of Nor- 
way pine averaged 6.8 tunnels. Brood was reared successfully from 
the majority of these tunnels. 
In connection with the 1921-22 improvement cutting, an experi- 
ment was carried on to determine the effect upon insect infestation of 
barking and scorching stumps. One set was barked down to the ground 
line; one set was scorched by burning either slash or dry wood over the 
stump; and a third set, kept as a check, was untreated. The results 
of this experiment are shown in Table ITI. 
TABLE III. INFESTATION OF NORWAY PINE STUMPS 
No. of new tunnels per stump 
Time cut Treatment Maximum Minimum Average 
Winter Untreated 27 O Tees 
Summer Untreated ASU 0 6.8 
Winter Barked when cut 34 te) 127i 
Winter Burned when cut 6 O PS 
The barking and burning operations were both carried out care- 
fully and a much better job was done than could be expected under 
ordinary woods conditions. Owing to the frozen condition of the 
ground it was impossible to bark below the surface of the litter. As 
the beetles tend to concentrate in the lower portions of a stump and 
frequently enter below the litter, barking did not have any material 
effect upon the number attacking the stumps. Therefore, if barking 
is to be effective, it should be done during the summer following 
logging. Thoro barking could be cheaply accomplished at that time 
and the broods of beetles in the stumps completely destroyed. Even 
winter burning did not entirely prevent infestation. However, the 
number of beetles per stump was very materially reduced by the treat-— 
ment. It was found that burning must be thoroly done to be effective. 
Little good resulted when the slash was piled over the stump and 
burned. It was necessary to get a good fire all around the stump with 
dry material and then pile on the slash a little at a time, keeping the 
fire against all parts of the stump. Slash burned over a stump did little 
but scorch the upper parts. The cost of barking was not excessive, being 
