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 hand methods such as already have been mentioned is 

 entirely impracticable unless 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 will 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 owners 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. Unfortunately the difficulty of treating 

 the woodlands in the infested area of New England is considerably 

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

 variety of species in mixture. 



Experiments have shown that coniferous trees are not injured by 

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

 is such that the trees can be thinned to a stand of conifers no hand 

 suppressive measures are necessary in order to prevent injury by this 

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

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



If mixtures containing a large percentage of deciduous trees are to 

 be protected 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 

 thinning can be adopted so that tree species will be 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 unfortunately the infested region abounds in large areas 

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

 means aside from hand treatment which will prevent serious injury 

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

 sprout growth the amount of damage sustained is not always so 

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

 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 caterpillars 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 



