Rainfastness of 5 Fungicides on the Leaf Surface of Hot Pepper

In order to elucidate the relationship between the rainfastness of fungicides and their water solubilities, the fungicide residues on the leaf surface of hot pepper was assessed and compared after the drop-wise applications of fungicide solutions on leaf surface followed by artificial raining. As the raining was progressed after application of aqueous acetone solution of fungicides, the residue levels of fungicides were drop rapid at the early stage of raining, but the decreasing rates of residue level were slowed down thereafter. The initial rainfastness was reversely proportional to the water solubilities of the fungicides. Whole amount of dimethomorph residue, which water solubility is 18 mg/L, was washed off by 2.5 mm of raining. Although WP formulations of fungicides showed remarkable decreases of rainfastness compared to the aqueous acetone formulations, the fungicides having low water solubility showed better rainfastness. Chlorothalonil and mepanipyrim suspension concentrates was better in rainfastness than their WP formulation, and the rainfastness of mepanipyrim suspension was reversely proportional to the median diameter of suspension particles in the range of 1 to 4 ${\mu}m$. In brief, the rainfastness of 5 fungicides tested on the pepper leaf was, in the early stage of raining, closely related to water solubility. But, as the raining is progressed, the effect of the unknown factor, which is related with the particle size of fungicides, becomes serious.

고추잎 표면에서 5종 살균제의 내우성

살균제 농약의 고추잎 표면에서의 내우성과 수용해 도와의 관계를 구명하기 위하여 수용해도가 다른 5종의 농약 수용액 혹은 농약 현탁액을 고추잎 표면에 점적처리하고 인공강우한 후 고추잎 표면의 농약 잔류율을 상호 비교하였다. 고추잎에 아세톤 수용액으로 점적처리된 살균제 농약은 인공강우량이 증가함에 따라 고추 잎 표면 잔류율이 급속히 감소하다가 점차 둔화되었으며, 인공강우 초기의 내우성은 농약의 수용해도에 반비례하였다. 수용해도가 18mg/L인 dimethomorph는 2.5mm의 강우에도 유효성분 모두가 소실되었다. 수화제 현탁액은 아세톤 수용액보다 내우성이 현저히 작았지만 수용해도가 작은 농약이 역시 내우성이 큰 것으로 나타났다. 평균입경이 작은 chlorothalonil과 mepanipyrim 액상수화제가 수화제보다 내우성이 컸으며, mepanipyrim 현탁액의 내우성은 입경과 반비례 관계를 나타내었다. 따라서 시험한 5 종의 살균제 농약의 고추 및 표면 내우성은 강우 초기에는 농약의 수용해도와 깊이 연관되어 있으며 후기로 갈수록 농약의 입경과 관계되는 미지 요인이 작용하는 것으로 밝혀졌다.