Studies on applications of soil insecticides for controlling turfgrass infesting scarabaeid grubs I

Relationship between the depth of soil and insecticidal action

Abstract

Generally, turfgrass infesting scarabaeid grubs are very difficult to control. In this paper, a simple and exact experimental method was conducted to select effective chemicals for control of them.
The results obtained were as follows.
1. On the relationship between thickness of soil layer and the effect of insecticides against 3rd-instar larvae of cupreous chafer, a extreme decline in mortality was observed in every plots of each insecticide applied to the soil layer more than 5cm. Daiazinon 5G, however, showed high mortality compared with fenthion 5 G and isofenphos 5G in 10cm plots because of its high vapor pressure.
2. By combined application insecticides and Aqua-GRO, a penetration adjuvant, insecticidal action was improved in 10cm plots. Especially, diazinon 5G, isofenphos 5G, chlorpyriphos 40EC and fenitrothion 50EC showed high level of mortarity, respectively. Besides, on residual activities in soils treated for 2 weeks, lower 5 cm soils from combined application plots showed high level of motalities, but, those from nonAqua-GRO-treated plots did not. According to these results, it seems that Aqua-GRO improved the penetration of insecticides into the soil.
3. On the effect of Aqua-GRO to the water retention, the soil with Aqua-GRO mainta fined more water than non-treated soil, and the upward movement of soil moisture owing to the vaporization was suppressed to a certain extent for 2 days after the treatment. It seems that the effect of the penetration adjuvant like this is important for the penetration of insecticides into the soil.
4. It seems that combination of insecticides and penetration adjuvants is very effective on utilization of existing insecticides and control of soil insects.