478 Bulletin No. 116. [August, 



tion of leaves of trees and shrubs in spring not infrequently cause 

 the death of those preferred by them for food, and the grubs are 

 particularly destructive in towns to the turf of lawns, in nurseries to 

 young evergreens, in the fruit plantations to strawberry vines, and 

 on the general farm to grass and corn. 



The injury by grubs is due, in all cases, to the destruction of the 

 roots of the plants infested and the consequent weakening or actual 

 killing of the plant. The tiature and extent of the injury to com is 

 well illustrated by observations made by one of my assistants, Mr. 

 Kelly, in a field near Ludlow, in Champaign county, about ten acres 

 of which were almost completely destroyed. By digging up to a 

 depth of twenty inches, and searching all the soil belonging to each 

 of sixty hills of com — an area, that is, three and a half feet square 

 for each hill — ^it was found that this badly injured area contained 

 an average of 3,460 grubs to the hundred hills, or more than 34 to 

 the hill, — a total of about three hundred pounds of grubs to the acre 

 of corn. The plants varied in height from two inches to six feet, 

 and .the total number o,f ears borne by two thousand hills was 786, 

 all small ears or nubbins. 



Prevention and Remedy. 



The subject of preventive and remedial measures was somewhat 

 fully treated in my Seventh Report (pp. 127-137), and there is 

 nothing important to add to that discussion at the present time be- 

 yond a statement of the results of an experiment with pigs as a 

 means of clearing the grubs out of an infested field. This experi- 

 ment was made in the field above referred to, near Ludlow, 111., ten 

 acres of the worst injured part being surrounded with a temporary 

 fence, and one hundred pigs averaging seventy-five pounds each, 

 together with eight large sows, being turned into the inclosure Sep- 

 tember 23. 



By October 13 the pigs had rooted over ihe whole surface of 

 the ten-acre lot, going, in some places, to a depth of ten or twelve 

 inches. An area equivalent to twenty corn hills was now examined 

 to a depth of twenty inches, with the result that an average of 4.8 

 grubs per hill were found, as compared with 34.6 per hill at the 

 beginning of the experiment — a benefit of 86 per cent, in twenty 

 days. The grubs found in the field at this time were usually eight 

 inches or more below the surface. 



The pigs were in this inclosure until October 20, when they were 

 removed to another badly injured part of the field, and a final ex- 

 ammation of the plot was made. In an area equal to ten hills of 



