Abstract
To evaluate the effectiveness of chemicals on the acaroid mites, two methods were devised and the effects of several miticides were tested. Ring method : A glass ring 9mm in diameter and 10mm in height was fixed with paste closely on a slide glass on which a piece of filter paper and black blotting paper labeled. In the ring, insecticidal suspension was dropped, and then about 100 mites were released. A cover glass was fixed on the ring with glycerine gelly. After 24 hours or 48 hours, the death rate of the mites was recorded. Petri-dish method : To test the contact effects of miticides, 300 to 500 mites were released on a piece of filter paper soaked with 2 cc of various dilutions of emulsion for 15 minutes. Then, the mites were transfered to anothor petri-dish, which was covered tightly by plastic sheat to prevent the escape of the mites. To test the fumigating effects of chemicals, a piece of filter paper treated by the chemical was hung by a string in deep petri-dish of 6cm in height and 8.5cm in diameter. This was designed to avoid the direct contact of the chemicals with the mites. After 24 hours, the results were recorded. The screening tests of 12 chemicals as the miticides on the acaroid mites, Tyrophagus dimidiatus, were carried out by the petri-dish method. The order of miticidal effect evaluated by the method was as follows; dieldrin>endrin>heptachlor>adrin>lindane, malathion, DDT>chlordane>diazinon>DN. The effects of o-dichlorobenzene and DDT were much lower than the above chemicals. Lindane was proved to be effective to the mites as the fumigant at room temperature (20℃) and as the contact poison, and was recommended in the practical use.
