Spear grass is a serious weed problem, especially for farmers. It retards growth of other plants, spreading aggressively by means of seeds and underground rhizomes. It's also dangerous to dogs, since it can work its way through the dog's fur into the skin, causing an abscess. It can also penetrate the dog's ears or pierce the skin between its toes. Because spear grass spreads underground, it can be difficult to eradicate.
Apply a weed killer meant for grass. Weed killers can damage the environment. Glyphosate is less harmful than some other weed killers because it breaks down rapidly in the soil. It can kill spear grass through direct contact with the leaves, which can kill the entire plant including the rhizomes, if applied correctly. It is less effective during dry seasons. Saturate the leaves and other above-ground plant parts. The weeds will absorb the week killer and carry it to the roots.
Hand weed couch grass whenever you see it, especially before seeds appear. Loosen the soil with a garden fork and pull out spear grass rhizomes by hand, trying to avoid breaking them up as each little piece can sprout into a new plant. Allow young plants to dry completely in the sun, to kill the entire plant, before putting them into your compost pile. If the weeds already have seeds, don't put them in your compost pile at all. Burn them if it is allowed in your area, or discard them in the trash.
Cover a garden with overlapping sheets of woven propylene. Plant the area with aggressive useful plants such as pumpkins, sweet potatoes and other spreading plants, inserting the young plants through holes in the propylene.
Rototill or plow the land every two weeks throughout the growing season, to kill spear grass and other aggressive weeds in a vacant field. The parts of the plant that are exposed to sunlight will be killed. The parts that get buried deeply by the process can't sprout. The next year, sow wild flowers or a beneficial weed such as mucuna pruriens or other legumes to crowd out any leftover spear grass plants.