44 



BULLETIN 891, U. S. DEPARTMENT OF AGRICULTURE. 



used only between beds of growing crops like lettuce, beets, parsley, 

 turnips, celery, or in uncultivated fields. The method of procedure 

 is to use boards 6 to 8 inches wide and of any length desired. These 

 are placed in the ground in the form of a steep V, having the top 

 edges of the board about half an inch below the surface of the 

 ground. The boards can be made to overlap as shown in Plate X. 



The only precaution 

 necessary is to block 

 out any cracks or 

 open places where the 

 larvae are likely to 

 escape. At each end 

 of the trough a keg 

 or bucket is sunk into 

 the ground and the 

 larvae that fall in the 

 trough usually crawl 

 along the bottom and 

 fall into the keg. 



A trough con- 

 structed through the 

 length of a field 

 serves as a barrier, 

 and grubs coming 

 from either side of 

 the trough are unable 

 to pass without fall- 

 ing in. They are un- 

 able to crawl up the 

 steep sides of the 

 troughs; moreover, 

 they seem to prefer 

 to crawl along the 

 bottom, with the re- 

 sult that they eventu- 

 ally fall into the kegs. 

 One of the large 

 troughs thus con- 

 structed captured between 3,000 and 4,000 grubs in a single night. 

 Estimates were made of the number of grubs captured on a 2-acre 

 field containing 12 troughs, each 200 feet long, and within the short 

 period of three weeks more than two 50-gallon barrels of grubs were 

 trapped. Since there are approximately 400 grubs to each quart, 

 and 200 quarts to a 50-gallon barrel, the number of grubs in a barrel 

 would be 80,000, or about 160,000 grubs captured from a. 2-acre field, 

 (Fig. 7.) 



Fig. 7. — Barrel of grubs of green June beetle, estimated 

 to contain 75,000 to 100,000, caught by trapping with 

 troughs and flowerpots. 



