Chemical Control of Pondweed (Potamogeton nodosus) and Barnyardgrass (Echinochloa crus-galli) in Paddy Fields

Pondweed is a waterlogging habitat weed of paddy fields margin which has recently invaded rice fields. Because barnyardgrass is the most abundant and important weed of paddy fields in Iran, hence adopting any program for pondweed chemical control should involve barnyardgrass control as well. Therefore, two separate trials were carried out to evaluate the efficiency of selective rice herbicides for managing both pondweed and barnyardgrass. In this experiment the treatments included applying thiobencarb (2500 g.ai.ha-1), butachlor (1800 g.ai.ha-1), oxadiargyl (105 g.ai.ha-1), pretilachlor (1000 g.ai.ha-1), bensulfuron-methyl (45 g.ai.ha-1), cinosulforun (45 g.ai.ha-1) and metsulfuronmethyl (10 g.ai.ha-1). In the first trial, each herbicide was applied separately. In the second trial herbicides were mized. Results showed that thiobencarb, butachlor and pretilachlor were effective on barnyardgrass control (≤95%) but had no effect on pondweed. Oxadiargyl was more effective on barnyardgrass (75-90%) than pondweed (35-45%). Sulfonylurea herbicides showed very good efficacy on pondweed control (≤95%) while low effect on barnyardgrass (≥35%). The second experiment was carried out in order to investigate the mixture compatibility of the two groups of herbicides with different weed control spectrum. Data of the second trial confirmed the results of the first trial and revealed that mixing the recommended dose of herbicides controlled both weeds by 95%.