Abstract/Contents: | In Japan, weeds grow vigorously during the warm and humid summer, so that turfgrass would be rapidly replaced by weeds in the absence of adequate weed control. Due to thatch layers and traffic most rainwater cannot permeate into the soil. This unusual draining system will affect the movement of applied herbicides. The major weeds in turf fields, especially golf areas, are shown in Table 1. In this Table there are 18 families and 61 species and the dominant species are Gramineae, Cyperaceae and Compositae. Temperature and soil water content mainly determine the weed species and their life cycles. Under low temperature conditions Chenopodium album, Polygonum sp., Stellaria media, Commelia communis and Setaria viridis are dominant, and under medium to high temperature conditions Amaranthus viridis, Portulaca oleracea and Eleusine indica. Since low tempeature [temperature] or low soil moisture prolong the duration of weed emergence, applied herbicides often give poor results. Low temperatures (5-10 degrees Celsius), high temperatures (40 degrees Celsius), and light (except under low oxygen conditions) breaks the seed dormancy of Digitaria ciliaris. The optimum temperature seems to be 30 degrees Celsius. Weed seeds germinate principally only in the upper 3 cm of soil, whereas in turf fields, germination is mainly in the thatch layer. Accordingly, where Polygonum sp. are the main weeds or where moisture is low, most soil treatment herbicides show poor weed control. In these cases, it is important to apply foliar treatment-type herbicides or use highly water soluble soil treatment-type herbicides. Mowing height of turfgrass affects the light intensity in turf, emergence and growth of weeds, weed species, and the efficiency of applied herbicides. A table lists herbicides used in turfgrass (Zoysia type) in Japan. Herbicides effective against gramineous weeds: asulam, orsobencarb, chlorphthalim, napropamide, propyzamide, benefin, pendimethalin, nitralin, benslide, butamiphos, and amiprophos. Herbicides effective against broadleaf weeds: triclopyr and dicamba. Herbicides effective against gramineous and broadleaf weeds: simazine, atrazine, isourone, and oxadiazon. Herbicides effective against cyperus weeds include dymrone and methyldymrone. Contact herbicides against gramineous weeds include asulam, propanil, and DSMA. Contact herbicides effective against broadleaf weeds: 2,4-D, MCP, triclopyr, MCPP, ioxynil, and bromoxynil. Contact herbicides effective against cyperus weeds: NC-311 and SL-940. In general, herbicides are used four times, namely, in early spring, spring, autumn and in the dormant season (in winter). In the dormant season, glyphosate is used against annual bluegrass. |