22 farmers' bulletin 845. 



METHODS OF CONTROLLING THE GIPSY MOTH IN WOODLAND. 



Satisfactory control of the gipsy moth in woodland by the em- 

 ployment of liand methods such as akoady have been mentioned is 

 entirely impracticable miless the tree growth is particularly valued 

 for purposes other than lumber. If the woodland is situated near a 

 large city and occupies space that is likely to be utilized in a few 

 years for building lots, considerable money may be expended to ad- 

 vantage in protecting the trees, as these wiU make the property much 

 more valuable when the land is subdivided. Limited areas of wood- 

 land on private estates may be of sufficient value to the o^vners to 

 justify a considerable expenditure for moth destruction. In all cases, 

 however, the species of trees involved should be studied carefully be- 

 fore a plan of work is adopted in order that the expense may be 

 reduced as much as possible. Unfortmiately the difficulty of treating 

 the woodlands in the infested area of New England is considerably 

 increased by the fact tliat they are for the most part composed of a 

 variety of species in mixture. 



Experiments have show^l that coniferous trees are not injured byj 

 the gipsy moth if grown in isolated pure stands, and if the growth' 

 is such that the trees can be thuined to a stand of conif ere no hand 

 suppressive measures are necessary in order to prevent injury by this 

 msect, (See fig. 13.) Such lots will also be immune from attack by 

 the brown-tail moth, as the larva? of this insect do not feed on conifers. 

 • If mixtures containing a large percentage of deciduous trees are to 

 be protc^cted from moth injury, it is very necessary that the species 

 involved should be considered carefully before a decision is reached as 

 to the best methods of treatment. Sometimes practical methods of 

 thimiing can be adopted so that tree species will bo left that are only 

 slightly subject to injury by these insects. A limited number of 

 experiments have shown that mixtures of chestnut, pine, red maple, 

 ash, and hickory, regardless of the proportion of each species, are 

 seldom injured by the gipsy moth. 



In woodlands the oaks are the most favored food plant of this 

 insect, and unfortmiately the infested region abomids in large areas 

 where these species predominate. At present there seems to be no 

 means aside from hand treatment which wiU prevent serious injury 

 to oak woodland, but as a large part of such land consists of poor 

 sprout growth the amomit of <lamago sustained is not alwa3^s so 

 great as it might at first appear. The greatest injury likely to bo 

 caused in such areas where oaks and gray birch abound is the dying 

 of small seedlings of pine or other valuable species which have been 

 denuded by the caterpifiars after the oaks and birches have been 

 defoliated. This leaves the prospective woodland in a much worse 

 condition than it was before the defoliation took place and reduce 



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