16 CIRCULAR 4 64, U. S. DEPARTMENT OF AGRICULTURE 



Since 1911 annual examinations have been made at observation 

 points scattered over the infested area to determine the intensity of 

 the infestation and the percentage of eggs, larvae, and pupae killed 

 by introduced natural enemies. These points were located in York 

 County in southwestern Maine; in Strafford, Merrimac, Hillsboro, 

 and Rockingham Counties in southeastern New Hampshire; and in 

 Essex, Middlesex, Worcester, Norfolk, and Plymouth Counties in 

 eastern Massachusetts. The results indicated a rapid building up 

 of the natural enemies, with an increasing percentage of the eggs, ij 

 larvae, and pupae being destroyed, until 1923. In the meantime the 

 intensity of the gypsy moth infestation, which had already reached 

 a high level in 1912, remained high until 1921, when it declined 

 rapidly until 1924. Since then there have been fluctuations in both 

 the intensity of the infestation and the percentage of moths destroyed, 

 but since the natural enemies have become thoroughly established 

 the infestation has not reached the high level attained in the earlier 

 years in some portions of the area. To evaluate correctly the benefit 

 derived from parasites and natural enemies, other factors, including 

 climatic conditions, must be taken into consideration. Without 

 doubt, however, these beneficial insects have played a useful role 

 with other control agencies in decreasing damage by this pest. 



CONTROL METHODS 

 GENERAL METHODS 



A number of standard methods are in use for controlling the gypsy 

 moth. They may be applied singly or in combination, depending on 

 the tree growth, the density of infestation, and other local conditions. 

 The essential information concerning each method is given in the 

 following paragraphs, but each owner or operator should select the 

 procedure that will give the best results when applied to his particular 

 problem. 



USE OF GYPSY MOTH CREOSOTE 



The application of gypsy moth creosote with a brush will destroy 

 egg clusters without removing them from the trees or objects on which 

 they are deposited. This work can be done between the first of 

 August and the time of hatching in the spring, which is about the 

 first of May. Treatment can be given most satisfactorily when there 

 is no snow on the ground. 



Gypsy moth creosote is on sale in the infested area and is a low- 

 grade coal-tar creosote which has been impregnated with sufficient 

 coal-tar pitch to discolor the egg masses and thus indicate those that 

 have been treated. A satisfactory grade can be bought in quantity 

 under the following specifications: 



Specific gravity 0.990-1.025 at 15.5° C. 



Tar acids 10 to 15 percent. 



Coal-tar hydrocarbons 80 to 85 percent. 



Water, not more than 2 percent. 



Flashpoint 70°-75° C. 



No separation of naphthalene at 0° C. - 

 Initial boiling point, 170°-180° C; 95 percent over at 

 285°-295° C. 



In addition, not less than 6.5 percent nor more than 8.5 percent by 

 weight of coal-tar pitch shall be added to the creosote furnished under 



