132 INJURIOUS INSECTS 



or spring, usually prevents the worms from originating 

 in such meadow or field. Such burning destroys the 

 previous year's stalks and blades, and, as a consequence of 

 what we have already stated, the nidi which the female 

 moth prefers. Burning as a preventive, however, hi^es 

 much of its practical importance unless it is pursued 

 annually, because of the irregularity in the appearance of 

 the Worm in injurious numbers. Judicious ditching, 

 i. e., a ditch with the side toward the field to be protected 

 perpendicular or sloping under, will protect a field from 

 invasion from some other infested region when the worms 

 are marching. When they are collected in the ditch 

 they may be destroyed either by covering them with 

 earth that is pressed upon them, by burning straw over 

 them or by pouring a little coal oil in the ditch. A 

 single plow furrow, six or eight inches deep and kept 

 friable by dragging brush in it, has also been known to 

 head them off. 



From experiments which we have made we are satisfied 

 that where fence-lumber can be easily obtained it may be 

 Qsed to advantage as a substitute for the ditch or trench, 

 by being secured on edge and then smeared with kerosene 

 or coal tar, the latter being more particularly useful 

 along the upper edge. By means of laths and a few 

 nails the boards may be so secured that they will slightly 

 slope away from the field to be protected. Such a 

 barrier will prove effectual where the worms are not too 

 persistent or numerous. Where they are excessively 

 abundant they will need to be watched and occasionally 

 dosed with kerosene to prevent their piling up even with 

 the top of the board and thus bridging the barrier. Tlie 

 lumber is not injured for other purposes subsequently. 

 In the invasion of Long Island in 1880, but two methods 

 were found successful in checking the march of the Army 

 Worm. Trenches were made by plowing, and in these were 

 distributed freshly cut Eed-top grass, a favorite food with 



