Napropamide and Oryzalin Effect on Simazine Tolerance of Four Ornamental Species

Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] applied with simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] reduced by 47 to 82% the severity of simazine symptoms on California privet (Ligustrum ovalifoliumHassk.), staghorn sumac (Rhus typhinaL.), and ‘Moonlight’ broom (CytisusXpraecoxBean). Oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) had a similar but smaller effect (40% reduction) when applied with simazine on broom in a field experiment and an effect equal to napropamide with simazine on privet in a greenhouse experiment. Both napropamide and oryzalin prevented some of the growth reduction from simazine on privet, broom, and ‘Baltic’ ivy (Hedera helixL. ‘Baltica’) in field experiments. In the greenhouse study with privet, napropamide prevented much of the growth-reducing effects of simazine on both shoots and roots of privet. Oryzalin appeared to have a similar effect.