Abstract
Laboratory experiments were conducted to determine the efficacy of an established attractant (methylmyristate) and feeding stimulants (starch, maltose, and sucrose), and the iesecticidal activity of boric acid as the constituents of baits for cockroach control. Starch (25 to 70%) and soluble starch (10 to 25%) were used as the basic constituents of the baits. The experiments were done at a constant temperature of 25±1℃. The results with the German conckroach were as follows. 1) When administered orally, boric acid showed no chemical repellency against the insects. 2) A single-day exposure of the insects to baits containing boric acid was enough to kill most of them, though the fed amount of boric acid was slowly effective. In a continuous exposure of the insects to the baits, 6.6mg of boric acid taken by 30 female adults could kill them all within a month, and the more the intake of boric acid was the shorter the duration necessary for killing the insects. Thus it is likely that all or at least most of the insects respond to their food every night. 3) When the water solutions were delivered from the needle of a syringe directly on to the mouthparts of young adults, (LD)_<50> values of about 150μg of boric acid per male insect and 200μg per female were expected. In this case mortality did not increase from the 11th day after the application. 4) The addition of methylmyristate to the bait clearly increased the amount of bait ingested by the insects at the optimum dose from 0.02 to 0.2%. The insects preferred the maltose-containing bait much more than the sucrose-contatining one especially at the higher concentrations of 10 and 15%. 5) Mortality by the bait with 0.5% lindane or fenitrothion in addition to 20% boric acid initially increased at a much more rapid rate than those without these insecticides, but especially with fenitrothion complete mortality resulted Afferward. 6) A wide distribution of the bait was more effectual for rapid control of the insect populations even in small test containers, and the baits were effective for controlling the insects even when there was a greater amount of another food which the insects could feed freely.
