GENERAL CONDITIONS 



75 



butt and more or less damaged by insects and fungi as a resixlt. 

 Amongst the hardwoods, however, loss from insects and fungi is 

 not serious, probably because there are few pure stands. With 

 pine, on the other hand, which occurs in pure groups, insect 

 damage is frequently very serious, usually after the tree has been 

 weakened by fire. For example, in 1896-1892 the southern pine 

 beetle, Dendroctonus frontalis, killed practically aU the mature 

 shortleaf pine and pitch pine in an area extending from North 

 Carolina to southern Pennsylvania and aggregating over 75,000 

 square miles.^ Fortunately chestnut blight is the only serious 

 fungus enemy as yet reported from any of the three types altho 

 there are many species which will attack trees which have been 

 weakened by fire. 



The growth of individual trees in diameter and height is usually 

 very rapid as the following figures show: 



But in spite of the rapid growth of single trees the yield per acre 

 per annimi is not high because the trees do not stand close to- 

 gether. Generally speaking the density per acre is one-half to 

 one-third of that in the types previously considered. This is due 

 to the lack of available moisture. Both the runoff and the flyoff 

 are rapid and hence there is not as much available foir tree growth 

 as in the cooler northeast. The low average yields per acre in 

 virgin stands have already been referred to and the jdeld figures 

 available tell the same story, large trees individually but few per 

 acre. 



1 See reports by Dr. A. D. Hopkins, XJ. S. Bxureau of Entomology. 



