Cenchrus echinatus L.

Cenchrus echinatus L.
Cenchrus echinatus commonly known as burr grass is an annual
grass that is native of tropical America. It has widely colonised
tropical and temperate zones worldwide. Though it is typically
associated with dry, sandy habitats it can also grow in moist areas,
where it may be long-lived and reach a much larger size.
Burr grass is recognisable by the burrs it produces; the panicle
when ripe consists of up to 50 spiny burrs that can stick to
clothing, wool, and fur, and farm and agricultural machinery
making it easily dispersible. Burrs can float on water and are
easily dispersed through flowing water.
Burr grass was first detected on Laysan Island in 1961 (Laysan
is part of the Hawaiian Islands National Wildlife Refuge). At its
height of infestation it covered 30% of the vegetated areas of the
island (63.6 ha). It displaced the native bunchgrass (Eragrostis
variabilis), thus threatening the survival of two endemic birds,
the ‘Critically Endangered (CR)’ Laysan duck (Anas laysanensis)
and the ‘Vulnerable (VU)’ Laysan finch (Telespiza cantans). E.
variabilis is an important nesting location for both of these birds
species, and also plays a major role in nesting for most of the
ground-nesting and burrowing seabirds on the island.
A successful management plan was carried out to eradicate burr
grass on Laysan Island, beginning in 1991. After trialling many
Photo credit: Forest & Kim Starr
techniques (heat application, herbicides, mechanical techniques
and salt water application), it was found that using a combination
of herbicide application (glyphosphate) followed by mechanical
control (hand pulling) was the most effective method for burr grass
control whilst creating the least impact on the wildlife present.
Sites were monitored every 6 weeks for three years after the last
burr grass plant was found, and every 16 weeks thereafter. By 1999
it was rare on the island, with the rate of finding new plants on a
previously cleared plot reduced from as many as 95 plants per hour
(in 1994) down to 0.043 plants per hour (Flint & Rehkemper 2002).
References:
Flint E., Rehkemper C. (2002) Control and eradication of the introduced grass, Cenchrus echinatus,
at Laysan Island, Central Pacific Ocean. In: C.R. Veitch, M.N. Clout (eds) Turning the Tide: The
Eradication of Invasive Species. Proceedings of the Internation Conference on Eradication of
Island Invasives. Pp 110.
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