CONTROL OP GIPSY MOTH BY FOREST MANAGEMENT. 



19 



the gipsy moth," the percentage of white oaks has been selected as a 

 basis of comparison for the six stands now under consideration. 



The percentage of white oaks present gives a natural and definite 

 basis of comparison which has a direct bearing upon both manage- 

 ment and moth control. 



With the exception of tamarack, there are no conifers among Class 

 I. trees (favored food of the caterpillar) . As there is no tamarack on 

 any of the lots now under consideration, the retention of conifers is 

 an important factor in moth control in these stands. In any stand 

 the leading species — that occurring in the greatest number — requires 

 careful consideration both as a food plant and as a forest tree if 

 success is to be expected. The presence in large numbers of young 

 growth of species desirable from both viewpoints is also important. 

 This brief statement by no means includes all factors which must 

 be considered, but the suggestions given below are based upon them 

 and upon markets as controlling factors in management. For con- 

 venience of reference four of the important factors are summarized 

 in the form of a table which follows : 



Some controlling factors in management. 



Stand at- 



White 

 oak. 



'onifers. 



Leading species. 



Number 

 of gipsy- 

 moth egg 

 clusters 

 per acre 

 in 1913. 



Dover, Mass 



Exeter, N. H 



Wareham, Mass 



Medfield, Mass 



Amesbury, Mass 



North Berwick, Me. 



Per cent. 

 38 

 30 

 21 

 10 

 5 



Per cent. 

 3 

 4 

 16 



Red oak 



do 



Scarlet oak . . 



Chestnut 



White pine. 

 Beech 



Per cent. 

 45 

 31 

 54 

 52 

 28 

 45 



15,000 



949 



12 



4,374 



550 



1 



TREES WHICH CONTROL. 



From the list of 150 food plants of the gipsy moth, published in 

 Bulletin 250, there were selected and considered in Part I all native 

 or naturalized trees which might be found in woods in the infested 

 region. Seventy-five species are included, and the list is given on 

 pages 8-10. 



When sufficiently numerous in a stand these would be leading spe- 

 cies, as that term has been defined above, and by that fact alone they 

 might become controlling factors in management, but many trees 1 

 in the list occur so infrequently or are so small that their presence or 

 absence in a stand would have no controlling effect upon the form 

 of management to be practiced. 



Of the whole 75 species only 18 have silvical characteristics which, 

 apart from any considerations of commercial value or of moth con- 



1 See Appendix, p. 51, 



