Mobility of diflubenzuron in two types of forest soils

Abstract

Abstract Diflubenzuron (DFB) [l‐(4‐chlorophenyl)‐3‐(2,6‐diflurobenzoyl) urea] and its two formulatons, Dimilin® WP‐25 and Dimilin® SC‐48, were applLed separately at 17.23, 51.69 and 155.07 μg of active ingredient (A.I.) (corresponding to 70, 210 and 630 g A.I./ha) to the top layers of columns (30 x 5.6 cm i.d.) packed with either sandy or clay loam forest soils. Water (1.251 L) equivalent to 50.8 cm of precipitation was allowed to leach through each column. After leaching, the columns were divided into 5 unequal segments aud the DFB residues in soils were extracted and analyzed by high performance liquid chromatography (HPLC). Mobility of DFB was low and did not increase with dosage. At a deposit rate equivalent to 70 g A.I./ha, nearly all the residues were found within 2.5 cm of the top of the column. Mobility of DFB did not increase with dosage. Even at 630 g A.I./ha, only about 9% of the technical DFB, 7% of Dimilin SC‐48 and 4% of Dimilin WP‐25 moved below the 2.5 cm level in sandy loam. Mobility of DFB In clay loam was lower than in sandy loam. No residues were found below the 10 cm level or in the leachates in either soil type at all dosage levels. In addition to soil type, mobility of DFB was also influenced by the additives present in the formulation with technical DFB > Dimilin SC‐48 > Dimilin WP‐25.