WiREWORMS. 81 



POISONED DOUGH. 



*In our experiments in 1888, poisoned sweetened dongli was 

 used with some success to attract and destroy the click-beetles. 

 ( See Bulletin No. 3, Nov. 1888, p. 38). As the wireworms in 

 our breeding cages readily came to the surface to eat wheat scat- 

 tered thereon, it was thought that many might be attracted by 

 sweetened dough placed on the surface. 



A few experiments soon made it evident that the wireworms 

 could not be thus attracted to the poisoned dough. 



BISULPHIDE OF CARBON. 



This substance has been quite extensively used against certain 

 subterranean insects. Our experiments showed that it would 

 kill wireworms when poured into a hole near infested plants ; 

 but as it had to be nsed at the rate of about 150 gallons per acre, 

 its cost would be excessive. 



{!)) Siihstances that act also as Fertilisers. 



There are several substances now in common use as fertilizers 

 which possess some insecticidal properties. Dealere in the potash 

 fertilizers, especially kainit and muriate of potash, claim that the 

 ravages of wireworms are effectually checked by the use of their 

 fertilizers. In 1890 and 1891 we carried on a large series of ex- 

 periments with salt, kainit, muriate of potash, lime, chloride of 

 lime, and gas-lime to determine whether they might be effectually 

 used against wireworms. 



SALT. 



Many farmers assert that salt either destroys wireworms, drives 

 them deeper into the soil beyond the roots, or renders the soil so 

 obnoxious that the worms leave. 



1. Will salt hill wireworms f From a large series of experi- 

 ments we found that to destroy wireworms, salt must be used at 

 the rate of about eight tons to the acre, or over one per cent, of 

 the soil to a depth of four inches must be salt. This amount 

 wotild be very destructive to vegetation. 



2. Will salt drive wireworms deeper into the soil f — In 1891 we 

 thoroughly tested this supposed action of salt upon wireworms by 



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