FOREST ENEMIES 183 



ling numbers. Again insects and fungi may be brought in from 

 foreign countries some of the most destructive enemies our 

 forests have known were introduced in this way. The chestnut 

 blight probably came from China, the Japanese beetle from 

 Japan. 



With insects, as with forest fires, prevention is better than 

 suppression and the goal of the forester is to prevent their out- 

 breaks. This they can help bring about by care of the forest 

 during all woods operations. Forest sanitation it might be 

 called. It consists in keeping the forest in such vigorous, healthy 

 condition that insects can not breed in great quantities. Burn- 

 ing the brush after logging, cutting out the unhealthy and 

 diseased trees of the forest while lumbering or thinning is 

 carried on, keeping the forest itself, in a natural state and keep- 

 ing natural forests all these help prevent outbreaks of insect 

 pests. 



When the forester speaks of a natural forest, he means a 

 forest where the kinds of trees are the same as those that natur- 

 ally grow there. Natural forests are, as a rule, safest from insect 

 attack they are the climax forest of a region, the ultimate sur- 

 vival of a species or combination of species that can best endure 

 on that particular soil and in that particular locality. 



Man-made forests that differ too widely from natural forests 

 are likely to be dangerous experiments. In a region where 

 white pine naturally occurs in mixtures with hardwoods such 

 as oak and maple, it would be hazardous to set out a planta- 

 tion of pure white pine alone. Insect attack is always worse in 

 a forest composed solely of one species since conditions there 

 are ideal, for the feeding and breeding of the natural enemies 

 of that species. 



