Abstract

Owning low LAI index and long seasonal plant, make Fennel plant a poor competitor against weed especially in early season, therefore, protection from weed is essential for successful cropping. Since conventional hand and mechanical weed controls are not economically effective, the use of other weed control methods, such as chemical control, is necessary. Field experiment was carried out in 2012 to evaluate of pendimethalin as a pre-emergence herbicide for weed control in fennel. In this experiment the efficacy of different rates of pendimethalin (0, 660, 990, and 1320 g a.i. ha-1) for selective control of grass and broadleaf weed species, were evaluated. Amaranthus retroflexus, A. blitoides, Chenopodium album and Convolvulus arvensis were the dominant broadleaf weed and Echinochloa crus-galli and Setaria viridis were dominant grass in all plots. Results showed that weed biomass significantly affected by herbicide rate and increasing herbicide dose generally improved both grass and broad leaf controls. However, Grass weeds were more susceptible to given rate of the herbicide compared with broad leaf weeds. For example the rate of 990 g a.i. ha-1 reduced broadleaf weed biomass by 57% , while application of the same rate of herbicide controlled 91% of grass weed. Application of herbicide at the rate of 1320 g a.i. ha-1 provided excellent control (>94%) of total grass weeds, however, this rate provided moderate control (<81%) of broadleaf weeds. Results from this research suggested that, greater rate of 1320 g a.i.ha-1 is required to maintain effective control of broad leaf in fennel, while, in area which grass weed are dominant weeds in fennel fields, the rate of 990 g a.i. ha-1 could be sufficient to effective control of grass.