INSECT ENEMIES OF EASTERN FORESTS 49 
all the infestation over a considerable area. In the East the mixed 
character of the stands and the consequent more spotted distribution 
of the susceptible host trees make it possible to handle smaller units 
more successfully than in the western forests. As far as possible, 
control units should be bounded by natural barriers, such as high 
ridges, open valleys, or broad strips of timber of a different type. 
SPOTTING 
The first step In connection with any control project is to locate and 
mark every infested tree requiring treatment. Good spotting is ab- 
solutely essential to the success of the control work and must be carried 
out by competent entomologists or men trained particularly for this 
purpose. Ordinarily the laborers of a control unit cannot be relied 
on to find and mark all the trees needing attention. 
BARK BEETLE CONTROL METHODS 
Methods of bark beetle control must take into consideration the di- 
verse habits of the insect species, the types of trees affected, and the 
topography and other conditions of the area. Since most of the de- 
structive bark beetles confine their attacks to a few species of trees, 
control can be carried out by treating only the affected host trees. 
Methods satisfactorily used with one beetle in one location may not 
be applicable to another insect or to the same species under other con- 
ditions. For example, with species that breed under the bark, it is 
only necessary to remove the bark, whereas in dealing with those that 
pupate and transform within the bark proper, it is necessary to de- 
stroy the bark in order to kill the broods. 
Logging or Utilization of Infested Timber 
It is becoming more and more practical in recent years to salvage 
infested trees because of the opening up of forested areas with pass- 
able roads. Salvaging has been especially useful in woodlots or in 
regions where the timber stands are broken. In two outbreaks (1931, 
1936) in Virginia it was used effectively. Salvaging serves the dual 
purpose of destroying the bark beetles and utilizing for lumber or fuel 
the material that otherwise would be of no value within a short time. 
Frequently it can be carried out with a profit to the operator. Where 
a millpond or similar facilities are at hand, storing the infested logs 
in water for several weeks is very effective and simple. It is also in- 
expensive. 
Solar-Heat Method 
The solar-heat, or “sun-curing,” method is particularly applicable 
to the control of bark beetles that attack thin-barked trees of small 
diameter, such as second-growth shortleaf pine, especially trees grow- 
ing in open stands and in areas where the burning method is objec- 
tionable. With this method, trees are felled in a north-and-south 
direction parallel to one another. They are completely limbed and 
the brush is cleared away, so that the logs will receive direct sunlight. 
After a few days exposure with clear skies and with air temperatures 
