Endozoochorous seed dispersal potential of five dominant southern weeds

Authors: SINGH, AKASHDEEP - Auburn University; SMITH, BRANDON - Auburn University; RUSSELL, DAVID - Auburn University; Price, Andrew; MCELROY, SCOTT - Auburn University; MAITY, ANIRUDDHA - Auburn University

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cattle grazing on weed-mixed forage biomass may potentially spread weed seeds, leading to plant invasions across pasture lands. Understanding the possibility and intensity of this spread is crucial for developing effective weed control methods in grazed areas. This research evaluated the seed germination and survival of five dominant weed species in the southern USA: Palmer amaranth, yellow foxtail, johnsongrass, field bindweed and pitted morningglory after incubation in bovine digestive fluid for seven time periods (0, 4, 8, 12, 24, 48, and 72 h). The findings revealed differences in seed survival and germination among all weed species, with tall morningglory reaching zero germination only after 24 h of incubation whereas Palmer amaranth and johnsongrass exhibiting up to 3% germination even after 96 h of incubation. The small seed size, hard and impermeable seed coat of Palmer amaranth and Johnsongrass made them highly resistant, whereas morning glory seeds were highly susceptible to rumen fluid, likely due to their seed coat becoming easily permeable and ruptured. This suggests that cattle grazing can selectively affect weed seed distribution and invasiveness in grazed grasslands and rangelands, including that for the designated invasive and noxious weed species. The results offer opportunities for devising customized feeding and grazing practice combined with timely removal of weeds in grazeable lands at pre-flowering stage for effective containment of some difficult-to-control weed species.

Technical Abstract: Cattle grazing on weed-mixed forage biomass may potentially spread weed seeds, leading to plant invasions across pasture lands. Understanding the possibility and intensity of this spread is crucial for developing effective weed control methods in grazed areas. This research aimed an in-vitro experiment to evaluate the seed germination and survival of five dominant weed species in the southern USA [Palmer amaranth (Amaranthus palmeri), yellow foxtail (Setaria pumila), johnsongrass (Sorghum halpense), field bindweed (Convolvulus arvensis) and pitted morningglory (Ipomoea lacunosa)] after incubation in bovine digestive fluid for seven time periods (0, 4, 8, 12, 24, 48, and 72 h). Furthermore, a full Tilley and Terry procedure was applied to an eighth sample after 48 h of incubation by stopping fermentation, simulating complete abomasum digestion. The findings revealed differences in seed survival and germination among all weed species, with tall morningglory reaching zero germination only after 24 h of incubation whereas Palmer amaranth and johnsongrass exhibiting upto 3% germination even after 96 h of incubation. The small seed size, hard and impermeable seed coat of Palmer amaranth and Johnsongrass made them highly resistant, whereas morning glory seeds were highly susceptible to rumen fluid, likely due to their seed coat becoming easily permeable and ruptured. This suggests that cattle grazing can selectively affect weed seed distribution and invasiveness in grazed grasslands and rangelands, including that for the designated invasive and noxious weed species. As grazing is a significant component in animal husbandry, a major economic sector in the south, our research provides important insights into the potential role of grazing as a dispersal mechanism for some of the troublesome arable weeds in the USA. The results offer opportunities for devising customized feeding and grazing practice combined with timely removal of weeds in grazeable lands at pre-flowering stage for effective containment of some difficult-to-control weed species.