Abstract
We made an experiment on the penetration through soil of insecticides making injurious insects of turfgrasses, especially white grubs, an object of pest control.
1) When we made the second-stage grubs an object, both of MEP and EPN were effective from soil surface to a depth of 4cm, but not effective below a depth of 4cm. When we made the third-stage grubs an object, they were effective from soil surface to a depth of only 2cm. But we addedpenetration adjuvants of anion system, the mortality of insects a little increased in the soil layer from a depth of 2cm. to 4cm. We think this is because the penetration adjuvants let the systemic action increase below a depth of 2cm.
2) When we measured the amount of the insecticides in soil by the gaschromatograph, in spite of the high volume spray of 4lit/m2, the active ingredient remained in the soil layer from soil surface to a depth of 2cm. In sand soil, 97% of the all amount of the detected insecticides remained from soil surface to a depth of 2cm. In Kuroboku soil, 99% remained there. The concentration of the insecticides was less than 2ppm. in the soil layer from a depth of 2cm. to 4cm. By 1 lit, spray, which is a practical application rate, 99.9% remained from soil surface to a depth of 2cm.
When we make such injurious insects in soil as white grubs an object of pest control, it is important how deep we can make insecticides penetrate through soil. We are now studying penetration adjuvants and the suitable time for the application of insecticides.
