70 FIELD WOKK AGAINST GIPSY AND BROWN-TAIL MOTHS. 



If spraying could be relied on to control the gipsy moth, the prob- 

 lem would be greatly simplified, but unfortunately it is impossible to 

 destroy all the caterpillars by spraying, and it is usually necessary to 

 supplement the work either with burlap or tanglefoot, and to creosote 

 all of the egg clusters that can be located during the winter. The 

 cost of these methods is difficult to determine, as there is much varia- 

 tion in expense owing to the character of the infestation, the size 

 of trees, and the locality in which the work is to be done. In gen- 

 eral it may be said that woodland can be pruned, egg clusters creo- 

 soted, and brush cut and burned for $25 to $30 an acre; tanglefoot 

 applied and tended for the season for $5 to $6; sprayed for $2 to $10; 

 creosoted the following winter for $5, and should be kept free from 

 injury by the gipsy moth for $2 an acre for each year thereafter. 



VALUE OF NATURAL ENEMIES IN CONTROLLING GIPSY AND 

 BROWN-TAIL MOTHS. 



The influence exerted by native birds and insect enemies of the gipsy 

 and brown-tail moths in this country has already been mentioned. 

 As soon as the work was resumed by the State of Massachusetts, 

 it was found that in some sections of the territory infested by the 

 brown-tail moth large numbers of caterpillars were dying from a 

 fungous disease. The matter was investigated by assistants em- 

 ployed by Mr. Kirkland in 1906, and specimens of the disease- 

 bearing caterpillars were referred to Dr. Geo. E. Stone, botanist of 

 the Massachusetts agricultural college, who stated that the cause of 

 the death of the caterpillars was a fungus known as Empusa aulicae, 

 Reichardt. This disease destroyed millions of caterpillars during 

 the spring and early summer of 1906, and it has been found quite 

 frequently since that time in Massachusetts, New Hampshire, and 

 Maine. It works on both small caterpillars in the webs and the 

 larger ones which feed during the early summer. This has assisted 

 in checking the increase of the insect, especially in the sections of 

 Massachusetts where it first became seriously injurious. The devel- 

 opment of this fungus is influenced largely by weather conditions 

 and during some years it has not greatly reduced the number of 

 caterpillars. 



During the past two or three years large numbers of caterpillars 

 of the gipsy moth have died from a disease which is popularly known 

 as the "wilt" or caterpillar cholera. This has been prevalent par- 

 ticularly in badly infested areas, especially in woodland, where 

 many of the trees have been nearly defoliated. It seems to develop 

 more rapidly on caterpillars which have not had sufficient nourish- 

 ment, although in some places it was present where a considerable 

 amount of foliage remained. The caterpillars attacked by this 

 trouble become sluggish and soon die, the inside of the body becoming 



