There are over 100 species of Spike Rush which can sometimes be difficult to differentiate from other species of lake weeds. In general, Spike Rush are small but can grow several feet out of the water. Spike Rush are perennial plants and are often confused with the smaller species of rushes, grasses, or sedges. Slender Spike Rush typically will grow completely underwater and appear as a submerged plant.
Spike Rush can grow in shallow water or moist soils and grow from rhizomes. Stems are unbranched with sheaths around the base but can be round, square, or flattened depending on the species. All Spike Rushes have small fruiting spikes at the tips of the stem.
Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many aquatic invertebrates. Ducks, geese, muskrats, and nutria all eat portions of Spike Rushes, from seeds, to rhizomes and tubers.
Mechanical/Physical Control Options
Spike Rush can be cut and the rhizomes can be dug up but physical control is difficult because it can reestablish from seeds or the remaining rhizomes.
Biological Control Options
There is no known biological control for Spike Rush, although goats are known to forage on many types of emergent vegetation.
Chemical Control Options
The active ingredients that have been successful in treating Spike Rush include; diquat (Harvester Liquid), fluridone (Sonar Q Granular and Fluridone Liquid) and glyphosate (Aqua Neat Liquid, Shore-Klear Liquid).
Harvester is a liquid diquat formulation that has been effective on Spike Rush. It is a contact herbicide. Contact herbicides act quickly and kill all plants cells that they contact. A non-ionic surfactant such as Cygnet Plus Liquid will have to be added to the Harvester Liquid solution for good results.
Sonar Q Granular and Fluridone Liquid are fluridone compounds and come in both liquid and granular formulations and though not labeled for control of Spike Rush, have also been effective on Spike Rush. These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides, but unlike the contact herbicides will completely kill the root system of the rush.
Shore-Klear Liquid and Aqua Neat Liquid are both glyphosate products that work great on the rush or any type of weeds growing in and around water and have half or more foliage out of the water. We recommend mixing with Cygnet Plus surfactant and spraying directly onto the foliage on a calm, sunny morning.
One potential problem with any chemical control method is the chance of oxygen depletion after the treatment caused by the decomposition of the dead plant material. Oxygen depletions can kill fish in the pond. If the pond is heavily infested with weeds it may be possible (depending on the herbicide chosen) to treat the pond in sections and let each section decompose for about two weeks before treating another section. If you plan to treat the entire body of water we recommend aeration, particularly at night, for several days after the herbicide treatment. This will help prevent oxygen depletion and ensure sufficient oxygen for fish.
Spike Rush can be propagated by transplanting whole plants with rhizomes into shallow water areas during the winter or early spring.
Spike Rush is a variety of sedge. Stems unbranched, many gas canals in cross section; leaf blades none, just sheaths at the base of the stem; inflorescence a single spikelet, on stem tips, no bracts; spikelets of various sizes, overlapping scales, few-to-many flowers.
external resources: tamu.edu & ufl.edu
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