A NATIONAL PLAN FOR AMERICAN FORESTRY 725 



kills a high percentage of the natural reproduction and of the young 

 trees set out in plantations, making it an unsafe practice to do any 

 planting in the vicinity of cutting. After the seedling white pines 

 become well established and until they are 25 years old the planta- 

 tions and natural stands are subject to severe damage by the white- 

 pine weevil, unless proper precautionary measures are taken. The 

 commercial value of thousands of acres of northern white-pine plan- 

 tations has been destroyed by this insect, definitely indicating that it 

 is unprofitable to attempt to grow this pine on unsuitable soil or under 

 conditions where some measure of protection is not assured. 



It must be clearly understood that these figures for losses include 

 normal as well as unusual drain in the forests. For example, surveys 

 in the ponderosa pine type of California and Oregon tabulate all trees 

 killed by bark beetles. Normally on the best sites but few trees die 

 each year from this cause, say, 30-40 M feet board measure per 

 section, while on poorer sites 50-100 M feet board measure may not 

 be an unusual loss. In lodgepole stands normal losses are practically 

 negligible so that any marked losses indicate abnormal conditions. 

 The same applies to outbreaks of defoliators. They either cause 

 little loss or widespread destruction. 



The financial success of certain forest industries such as turpen- 

 tining of the southern pines may hinge on the attack of insects. 

 Improper methods of chipping result in the attack of a flatheaded 

 wood borer which completely honeycombs the heartwood, lessening 

 the tree's life as a turpentine producer and causing it to break off. 

 Enormous losses have occurred from this source. 



Forest plantations are particularly subject to the destructive 

 activities of insects, chiefly because plantations usually consist of 

 large blocks of a single species of tree. Then again many plantations 

 are set put on soils that are not suitable for the species of trees used. 

 Losses in northern white pine plantations in the Northeast and de- 

 struction of black-locust stands by the locust borer have, in a great 

 measure, discouraged the planting of these valuable trees. There 

 is a need for more knowledge and forethought in the setting out of 

 forest plantations. 



Insect-killed forests are a potential danger because of the existing 

 fire menace. When extensive outbreaks of insects develop in forest 

 types composed chiefly of one species of tree a high percentage of the 

 stand may be destroyed. These standing dead trees go down in the 

 course of a few years making an almost impenetrable tangle of logs 

 and tops. Under proper conditions a flash of lightning may set off 

 the mass resulting in a widespread conflagration almost impossible to 

 fight. Past experience has shown that epidemics of the mountain 

 pine beetle in lodgepole pine have been followed by fires more often 

 than not. 



The old snags of insect-killed trees scattered throughout our 

 mature forests, which average for some areas as many as 10 per acre, 

 stand for many years and greatly increase the cost, difficulty, and 

 danger in fire control. Snag felling is required in many sales of 

 national-forest timber, and many private operators have already 

 adopted this regulation. The increased cost of control of fires which 

 have spread from burning snags within fire lines would alone justify 

 insect control even at a high cost. 



