Abstract
In the course of developing Benzylthiolcarbamate herbicide, B-3356: S- (2-chlorobenzyl) N, N-diethyl-thiolcarbamate was found to have wide selectivity between germinating weeds and turf. B-3356 inhi-bited the germination and the growth of weeds as well as the sister compound B-3015: S- (4-chlorobe-nzyl) N, N-diethylthiolcarbamate (Bethiocarb), however, did not change the leaf color to red when sprayed on Manilagrass (Zoysia matrella Merr) . Results of the experiment to study the herbicidal effectiveness and the applicability to turf are summarized as follows;
(1) Susceptible weed species to B-3356 were: Digitaria adscendens, Poa annua, Alopecurus aegualis, Cerastium holostesides, anb Commelina communis. Amaranthus virrdis, Polygonum longisetum, and Erigeron annuus were succeeding. Rumex japonicus (seedling), Vicia angustifolia, and Kummerovia striata were tolerant.
Combination of B-3356 with CAT at the ratio of 5: 1 expanded the weed spectrum and the range of application time.
(2) Relationship between chemical structure and phytotoxicity to Zoysia matrella are; A series of compound with chlorine atom on the 2-position of the benzyl ring did not cause any phytotoxicity on turf leaf, but the non-substituted or 4-substituted ones inhibited the chlorophyll biosynthesis and caused the formation of red pigment in the turf leaf under sunlight.
(3) Herbicidal effects was best with the spray volume of 150cc/m2 and 300cc/m2, succeeded with 600cc/m2 and less effective with 75cc/m2. Phytotoxicity decreased with the increase of spray volume.
(4) Field trial in the established Zoysia matrella turf showed that B-3356 was effective against Panicum crus-galli, Digitaria adscendens and Polygonum nodosum by the pre-emergence application at the dosage 0.6g a, i, /m2, but not sufficient by the early post-emergence application at dosage 0.75g a, i, /m2. Combination of CAT at the ratio of 5: 1 resulted in good control even at 0.5g a, i, /m2 in total dosage. Phytotoxicity to turf was not obserbed in any plot of the experiment.
(5) Phytotoxicity of B-3356 by application just after transplanting at the dosage of 1.25g a, i, /m2 was not observed on Zoysia matrella, but in case of Cynodon dactylon (Tifton-328), slight growth inhibition was observed.
In conclusion, B-3356 is a promissing pre-emergence or early post-emergence herbicide in turf. The Combination of CAT with B-3356 enable the expansion of weed spectrum and the range of application time.
