Abstract
The physiological activities of streptothricin antibiotics were investigated, taking racemomycin-D as a representative of the group. It was found that racemomycin-D has insecticidal activity, fish-toxicity and inhibitory activity on plant growth. Firstly, racemomycin-D showed a weak but broad-spectrum insecticidal activity against the adults of Blattella germanica, Musca domestica, Nilaparvata lugens, Laodelphax striatella, and Plutella xylostella. A rather strong insecticidal effect on Culex pipiens molestus larvae was found, with mortalities of 90% and 15% at 10 ppm and 2 ppm, respectively. Though racemomycin-D showed no insecticidal effect against the larvae of Spodoptera litura, it showed inhibitory activity on feeding at a concentration of 300 ppm. Secondly, racemomycin-D was toxic to all the fish species examined, i. e., Misgurnus anguillicaudatus, Carassius auratus, and Oriziae latipes. Among these, racemomycin-D showed particularly strong toxicity against C. auratus with a TLm of 3.7 ppm (after 48 hr). Thirdly, racemomycin-D showed strong inhibitory activity on the growth of Brassica campestris L. subsp. Napus Hook fil et Anders var. nippo-okifera, Arctium Lappa L., Petrocelium sativum, and Raphanus sativus L. var. acanthiformis at a concentration of 500 ppm (with an inhibitory ratio of 0.1, relative to 1.0 for the control group).
