Influence of herbicides on germination and quality of Palmer amaranth (Amaranthus palmeri) seed

Abstract

Lab and greenhouse studies were conducted to evaluate the effects of chemical treatments applied to Palmer amaranth seeds or gynoecious plants retaining seeds on seed germination and quality. Treatments applied to physiologically mature Palmer amaranth seed included acifluorfen, dicamba, ethephon, flumioxazin, fomesafen, halosulfuron, linuron, metribuzin, oryzalin, pendimethalin, pyroxasulfone, S-metolachlor, saflufenacil, trifluralin, and 2,4-D plus crop oil concentrate applied at 1 and 2× the suggested use rates from the manufacturer. Germination was reduced by 20% from 2,4-D, 15% from dicamba, and 13% from halosulfuron and pyroxasulfone. Dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D decreased the average seedling length by at least 50%. Due to the observed effect of dicamba, ethephon, halosulfuron, oryzalin, trifluralin, and 2,4-D, these treatments were applied to gynoecious Palmer amaranth inflorescence at the 2× registered application rates to evaluate their effects on progeny seed. Dicamba decreased seed germination by 24%, whereas all other treatments were similar to the control. Crush tests showed seed viability was greater than 95%; thus, dicamba did not have a strong effect on seed viability. No treatments applied to Palmer amaranth inflorescence affected average seedling length; therefore, chemical treatments did not affect the quality of seeds that germinated.

Previous crop and herbicide timing application effects on weed population growth rate

“…However, the magnitude of the contribution to the seedbank depends on the time of weed emergence relative to the crop (Bosnic & Swanton, 1997). To reduce the number of viable weed seeds that enter the seedbank and population growth rates, late‐season applications at flowering or fruit setting demonstrated potential to reduce seedbank size (Bennett & Shaw, 2000; Isaacs et al., 1989; Moore et al., 2021; Taylor & Oliver, 1997).…”