Lalam, scientifically known as Imperata cylindrica, is a perennial rhizomatous grass native to tropical and subtropical regions of Asia, Africa, and Southern Europe. It has spread globally, including the Southeastern United States, and is considered one of the world’s most invasive weeds due to its aggressive growth.
Identifying Lalam (Cogon Grass)
Lalam can grow up to 6 feet (2 meters) tall, forming dense stands. Its leaves are upright, narrow, and often have finely toothed or serrated margins. A distinguishing feature is a prominent white midrib that is notably off-center, closer to one leaf edge than the other.
Below ground, Lalam develops an extensive network of sharp-tipped, white rhizomes, which are underground stems. These rhizomes can penetrate deep into the soil. Lalam reproduces both through these rhizomes and by producing fluffy, white, plume-like seed heads. A single plant can yield numerous wind-dispersed seeds, contributing to its rapid spread. This grass is also known by other common names such as Cogongrass, Lalang, or Speargrass.
Why Lalam is a Problem
Lalam poses significant threats to natural ecosystems by outcompeting native vegetation. It forms dense monocultures that reduce biodiversity and displace local plants. This grass also releases allelopathic chemicals into the soil, which suppress the growth of other plant species.
Lalam infestations can severely reduce crop yields in agricultural settings. Lalam is also a severe fire hazard. Its dry, dense foliage ignites quickly and burns at exceptionally high temperatures, leading to more frequent and intense wildfires that can damage native plants and structures.
Lalam’s extensive rhizome system makes it difficult to eradicate. These underground stems store energy, allowing rapid regrowth even after above-ground parts are removed. This resilience, coupled with prolific seed production and wind dispersal, contributes to its persistent nature and ability to quickly re-establish.
Controlling Lalam (Cogon Grass)
Controlling Lalam requires a persistent and integrated approach. Preventing its establishment is key. This includes thoroughly cleaning equipment and vehicles to avoid spreading Lalam seeds or rhizome fragments. Early detection and prompt action on new infestations are also important.
Physical control methods can help manage Lalam, though complete eradication is difficult. Manual removal is challenging due to its extensive rhizome network; any left-behind fragments can sprout new plants. Repeated tillage can help exhaust the plant’s energy reserves by bringing rhizomes to the surface. However, tillage can also spread rhizome fragments if equipment is not cleaned properly. Prescribed burning can remove above-ground biomass, but it is ineffective for eradication and can promote Lalam’s spread by clearing ground for seed germination and stimulating rhizome regrowth.
Chemical control often involves specific herbicides like glyphosate and imazapyr, which are absorbed by the plant and translocated to the rhizomes. Glyphosate is a non-selective herbicide with no soil residual activity, making it a safer option around desirable plants, though it requires repeated applications. Imazapyr is more effective and provides longer residual control, but it is also non-selective and can injure or kill nearby desirable vegetation due to its soil persistence.
For optimal results, herbicide applications are often needed multiple times over several years, particularly in late summer or fall. Combining different methods, such as burning or tilling followed by herbicide application, can enhance control by promoting new growth more susceptible to herbicides. An integrated management plan combining prevention, physical methods, and chemical treatments offers the most sustainable path to Lalam control.