The three herbicides are all selective herbicides of post-seedling internal absorption type. Bispyribac-sodium belongs to pyrimidine salicylic acid herbicide, penoxsulam is triazole and pyrimidine sulfonamide herbicide, metamifop is aromatic phenoxaloxalamide ester herbicide.

    Penoxsulam is mainly effective against juvenile barnyard grass, but has no effect against resistant barnyard grass (such as weeds, weeds, etc.). Bispyribac-sodium is effective against barnyard grass, bispyribac-sodium (red mixed root) and rice plum dioxalium, and had certain protective effect against some broadleaf grass (polygonum hydropiper l.). Metamifop is effective for barnyard grass, horse tang and ox tendon grass, especially for resistant weeds. Both dioxalether and penoxsulam had no effect on occulum, but metamifop had some effect on occulum.

   When used timely and properly, penoxsulam can achieve more than 90% dead grass effect. The dosage of bispyribac-sodium can reach more than 95%. Metamifop only has obvious effect on the part above the node, and can achieve 99% of the weeding effect, but it has no obvious effect on the growth point and root. Metamifop plots still have a lot of weeds after the rice is harvested.

   The death time of penoxsulam weeds was 3 ~ 5 days under normal temperature. Bispyribac-sodium 7 ~ 10 days, but the temperature is lower than 20oC, the death time of weeds will take about 15 days. It takes 15 days for the weeds to die.

    Therefore, penoxsulam is suitable for use before two leaves of rice at low temperature. Bispyribac-sodium suitable for normal temperature, rice after one leaf. Metamifop is suitable for fire repair after resistant barnyard grass or penoxsulam is not well prevented.