Einfluss unterschiedlicher Formulierungen auf die Stabilität und insektizide Wirkungen von Pyrethroiden im Boden.

Persistence of four pyrethroid insecticides cypermethrin, deltamethrin, fenvalerate and permethrin was investigated in a standardized soil test under laboratory conditions before and after formulation. Degradation of unformulated active ingredients (a.i.) took place within t 1 2 = 21 d (cypermethrin), 88 d (fenvalerate), 110 d (deltamethrin) and 126 d (permethrin), respectively. Formulation of cypermethrin with the aid of inorganic adsorbents like fractosil, silica gel and sea-sand had no influence on degradation rates. In comparison with it persistence of cypermethrin increased considerably after formulating with sawdust of different origin (t 1 2: pine-wood 30 d, beech 52 d and oak 110 d). Formulation by oak dust significantly increased persistence of all a.i. tested (t 1 2 = 110-475 d). Adsorption of pentachlorophenol or 4-hydroxy-benzoic acid onto pine-wood formulations showed stabilizing effects on cypermethrin indicating that unprotected (unformulated) a.i. were decomposed primarily by soil microorganisms. Sawdust formulations of deltamethrin and cypermethrin significantly inhibited the hatching rate of Phorbia brassicae Bouch e ́ at C ≤ 500 μg a.i./plant compared with 50 000 μg chlorfenvinfos/plant