April, '16] DAVIS: WHITE GRUB INVESTIGATIONS 279 



The last is the species referred to by Dr. Forbes as Viviana sp. on 

 p. 475 of bulletin 116 of the Illinois Agricultural Experiment Station. 



Miscellaneous Enemies. — ^Spiders are quite predatory on beetles 

 often catching them in their webs but not infrequently actually cap- 

 turing the beetle as it feeds at night. Mites are very troublesome 

 in cages where they attack grubs and occasionally we find them suf- 

 ficiently numerous on grubs in the field to cause their death. 



Animals such as skunks and opossums are well-known enemies of 

 grubs and do their share towards holding them in check, while many 

 birds, and especially crows and blackbirds, are equally well known for 

 their fondness for white grubs. 



Diseases. — Four types of grub diseases are known, these being of 

 fungus, bacterial, protozoan and nematode origin, respectively. 

 Among the fungus diseases the best known are the Cordyceps because 

 of the peculiar growth which they cause. The green muscardine 

 fungus (Metarrhizium anisoplice) is almost equally well known as an 

 insect fungus disease and although it seems to have been successfully 

 used artificially for the control of some insects, it has never proven 

 satisfactory nor even given an indication of proving satisfactory 

 against white grubs. 



Of the several recognized bacterial diseases none have shown any 

 indication of proving effective in the control of the white grub. 



We have observed two outbreaks of a protozoan disease of white 

 grubs which has apparently effectively controlled the grub in certain 

 localities. It was first observed at Hoopeston, Illinois, by Mr. W. P. 

 Flint and the writer (Oct. 1912) and later (Oct. 1915) by the writer at 

 Belvidere, Illinois. In both cases the diseased grubs came to the 

 surface or to near the surface of the ground where they died. 



At Lancaster, Wisconsin, we found a number of fields in 1915 which 

 were apparently cleared or at least practically cleared of grubs by a 

 nematode "disease," an affection which seemed to be assisted greatly 

 by the wet season. 



Methods of Control 



Utilizing Farm Animals. — Hogs have been employed as a means 

 of clearing fields of white grubs for many years and where they can 

 conveniently be turned into an infested field this is the surest and 

 quickest method that may be employed. When the infested field is 

 being plowed, if before the grubs have gone deep into the ground or 

 after the grubs have returned to near the surface in the spring, hogs 

 should be allowed the run of the field. Likewise chickens and turkeys 

 should be trained to follow the plow, harrow, and cultivator in fields 

 located near the farm buildings. We have known of fifteen-acre 



