INSECT ENERHES — PACKARD 329 



procedures, no added expense to the farmer is involved in obtaining 

 the added protection from insects Avhich they afford. 



MECHANICAL CONTROL MEASUItES 



The mechanical devices used for the control of insects attacking 

 cereal crops are confined mostly to the ordinary farm tools, which, 

 however, rather than having any direct effect on the insects themselves, 

 are chiefly effective indirectly through their use in cultural procedures 

 and cropping systems. Plowing and disking do, of course, kill a 

 considerable proportion of certain soft-bodied insects, such as the 

 white grubs, cutworms, earworms, and rootworms, particularly if done 

 at a time when they are changing from the worm to the adult beetle 

 or moth stage in their underground pupal cells. The indirect effect 

 of plowing under corn residues containing corn borers and soil con- 

 taining grasshopper eggs to prevent their emergence has already been 

 mentioned. In these cases, however, the benefits are derived mainly 

 from the burial of the insects rather than from the mechanical action 

 of the plowing. In general, the direct mechanical effect of the ordi- 

 nary soil-working tools is of minor importance in the control of the 

 insects injuring cereal crops. 



The rotary plow should perhaps be mentioned as an exception to 

 this statement. This machine has a power-driven horizontal cylinder 

 bearing a series of blades somewhat like a lawn mower. It not only 

 turns over the soil but chops it finely, together with any insects, such 

 as white grubs, it may contain and has been reported to be very effec- 

 tive against soil-infesting insects. Because of the high cost of opera- 

 tion and the impracticability of using it in stony ground, however, it 

 has not come into general use. 



With the exception of equipment for the application of insecticides, 

 the development of special mechanical devices for the direct control 

 of insects has been very limited. In this field the development of ma- 

 chinery for the destruction of European corn borers has been most 

 thoroughly investigated. As a result of intensive cooperative work 

 by agricultural engineers and entomologists several useful forms of 

 equipment have been devised or adapted for corn-borer control. These 

 include low-cutting attachments for corn binders and harvesters, 

 hand cutting hoes and stalk shavers (pi. 7) for use in low-cutting of 

 corn to be shocked by hand or corn stalks to be plowed under, shred- 

 ding and chopping attachments for mechanical corn pickers, sta- 

 tionary busker-shredders, silage cutters and field silage harvesters, 

 and stationary fodder cutters and grinders. Although little of this 

 machinery has yet come into general use, with the increase of the borer 

 in the main Corn Belt it may be used extensively after the war, when 

 materials essential in its manufacture are available. 



