GIPSY MOTH WORK IN NEW ENGLAND, 21 



Service, has been appointed to take charge of the investigations along 

 this line. The table given under the "food-plant experiments" indi- 

 cates in a general way the degree of susceptibility to moth attack of 

 some of our more common forest trees. Certain species, however, 

 are of little commercial value, and it is desired to discourage their 

 growth, as well as those that are particularly susceptible to gipsy- 

 moth attack. In the case of valuable species that are susceptible to 

 attack and for the growth of which a large portion of the infested region 

 is favorable, the only step which can be taken is to determine whether 

 or not they can be sufficiently protected from serious damage by 

 associating with the less susceptible species in small proportions. Of 

 course, the presence of these species may jeopardize the safety of the 

 associated species which would otherwise be immune. However, 

 before abandoning these species careful experiments will be made to 

 determine whether there are associations with which they can join with 

 safety. 



The chief, fact that reduces the liability of certain species of trees, 

 particularly conifers, to gipsy-moth attack is that the very young cater- 

 pillars do not feed upon them. Therefore, if there are present no trees 

 or undergrowth upon which the young caterpillars will feed and thereby 

 develop to a size which enables them to attack conifers or similarly 

 susceptible species, they will not be attacked. Thus it appears that 

 certain species can be grown pure or in exclusive association and be 

 free from gipsy-moth attack. Any system of forest management 

 should endeavor to produce in a given area only trees of commercial 

 value, and the foregoing lists (pp. 14-15) indicate the most suitable 

 species for selection. 



In converting a given stand of timber into one which shall be im- 

 mune from gipsy-moth attack, the different classes of trees should be 

 considered for removal in the following order: 



(1) Trees of naturally low commercial value and susceptible to 

 gipsy-moth attack. 



(2) Trees of low commercial value on account of growing in un- 

 favorable situations and susceptible to gipsy-moth attack. 



(3) Trees of commercial value, favorably situated, and subject to 

 gipsy-moth attack. 



(4) Trees of naturally low commercial value, but not liable to 

 gipsy-moth attack if properly associated. 



(5) Trees of low commercial value on account of growing in un- 

 favorable situations and not liable to gipsy-moth attack. 



(6) Trees of commercial value favorably situated and not liable 

 to gipsy-moth attack. 



Silvicultural conditions in the woods of the infested region are very 

 poor. Through repeated fires and heavy and inconsiderate cutting, 

 the growth of weed trees has been greatly favored and the growth of 



