Screening of Herbicides for Rice Seedling Safety and Echinochloa colona Management under Australian Conditions

Abstract

Different herbicides are currently required for sustainable weed management in aerobic rice. Three pot experiments were conducted using different herbicides to evaluate rice safety and for the control of Echinochloa colona, a major weed of aerobic rice. Among the pre-emergence (PRE) herbicides, it was found that pendimethalin (594 g ai ha−1) and flumioxazin (60 g ai ha−1) were relatively safe herbicides for rice and provided 100% control of E. colona. All other PRE herbicides, such as atrazine, cinmethylin, clomazone, dimethenamid-P, isoxaflutole, metribuzin, prosulfocarb + S-metolachlor, pyroxasulfone, trifluralin, and S-metolachlor reduced the biomass of rice compared with the non-treated control. Dose-response studies revealed that flumioxazin and pendimethalin even at low doses (30 g ai ha−1 for flumioxazin and 294 g ai ha−1 for pendimethalin) provided excellent control (>95%) of E. colona. Post-emergence (POST) application of paraquat (360 g ai ha−1) at the time of rice emergence caused toxicity in the crop, but also provided excellent control of E. colona. When applied just after crop emergence (11 days after sowing), Pendimethalin was found to be safe for rice (2% mortality) and reduced the biomass of E. colona by 88% compared with the non-treated control. It is quite possible that the rice variety Reiziq used in this study may have a tolerance to flumioxazin, which needs further investigation involving more rice varieties. This study suggests that flumioxazin can be used as an alternative to pendimethalin for the sustainable management of E. colona in aerobic rice.

Responses of rice genotypes to foliar-applied metribuzin

“…At 176 g ha −1 metribuzin, the biomass of short-grain genotype 'RES223' was significantly reduced, by 88% of the untreated control. Researchers in Australia found that rates of metribuzin as low as 36 g ha −1 were required to reduce the negative effect on rice biomass (Mahajan and Chauhan 2022), so the results of the present study concur with this conclusion. Long-grain genotypes 'RES8', 'CL271', and 'RES19' produced the least biomass reduction, at 10%, 8%, and 4% of the untreated control, respectively.…”

“…The same study found no correlation between rice injury from metribuzin and yield reduction, dry weight reduction, maturity delays, or seed germination (Lawrence et al 2021). Mahajan and Chauhan (2022) evaluated metribuzin at rates 72 and 144 g ai ha –1 and were able to reduce jungle rice [ Echinochloa colona (L.) Link] biomass by 70% and 100%, respectively, compared to the untreated control.…”

A new series of acylhydrazones derived from metribuzin with modulated herbicidal activity

“…Similarly, other authors have observed that the increase in metribuzin application rates (from 72 to 144 g ai ha −1 ) led to the highest decrease in biomass of Echinochloa spp, from 70 to 100 %, respectively [ 55 ]. In the particular case of A15 formulations (acylhydrazone 15 ), regardless of the application rate (A15–90 and A15-180), a reduction in biomass formation (3.48 g mean value) relative to control (4.60 g) was observed, although without significant differences (p > 0.05) between them.…”