Pests and Diseases 189 



abundant, control methods are necessary. One method 

 of control is by plowing three or four furrows with the 

 vertical edge facing the direction from which the army is 

 approaching and dragging a log down these furrows to 

 make a loose dust mulch. If the dust is warm, many of 

 the insects perish by suffocation when they fall into this 

 dust, but it is better to drag the pole down the furrow 

 often during the invasion in order to kill as many as pos- 

 sible. If the attack is severe, it is often a good policy to 

 spray the furrows with kerosene emulsion in case there is 

 not sufficient time to do the dragging. The best method 

 of control consists in applying a heavy dose of lead ar- 

 senate to the crop around the edge of the field. Poisoned 

 bran mash is often effective in preventing a severe attack. 

 By fall-plowing fields in which worms were numerous in 

 late summer, many of the hibernating larvae are destroyed. 



The fall army-worm (Laphygma frugiperda S. and A.). 



This species is rather similar to the above insect, but 

 its destructive period is usually later in the summer. In 

 appearance it is very similar to the beet army-worm and 

 is distinguished from it by the number of dots on its 

 segments. It does not develop the army instinct so readily 

 as the common army-worm and is not ordinarily so de- 

 structive. It feeds on a wide variety of crops. Arsenical 

 sprays are frequently successful in controlling this pest. 

 Often on large fields, such as alfalfa stubble before the 

 beet field is reached, many of the worms are crushed by 

 running a heavy roller over the field. Plowing and 

 disking, together with cultivation, kill many of the over- 

 wintering forms. 



