Rottboellia cochinchinensis
itchgrass, pricklegrass, guinea fowl grass
Here is a real nasty emerging
weed which I have noticed popping up all along the KwaZulu-Natal north coast.
Watch out for it eradicate as soon as it is discovered before it gets out of
hand.
A quick search on the internet
turned up the following information about Rottboellia cochinchinensis
Rottboellia cochinchinensis
Distribution
A native of Indo-China, which has
naturalised throughout the tropics of Asia, in north-eastern Australia and the
savannah zones of Africa including South Africa.
Rottboellia cochinchinensis has
been introduced throughout the Caribbean, Tropical America and the southeastern
and central United States. Although it may occur under a variety of moisture,
light and soil conditions, at a wide range of altitudes, Rottboellia
cochinchinensis is most commonly found on sunny, disturbed sites with high
rainfall or irrigation in subtropical and tropical climates.
Distinguishing Characteristics
Rottboellia cochinchinensis is an
erect, annual grass that can grow to 3m high. Stilt roots often develop at the
base of the stem. Plants produce abundant side shoots and grow into large
clumps. The leaf sheath and the lower portion of the leaf blade are usually
covered with stiff hairs that have a small swelling (tubercle) at the base.
These hairs break off on contact,
penetrating and irritating the skin. The leaf blades, which measure 150mm to
500mm inches long and up to 25mm wide, typically have broad white midribs and
scabrous (rough to the touch) margins.
The ligule is a membranous,
ciliate flap, to 3mm long. The slender, cylindrical, unbranched inflorescence
is segmented. Each heteromorphic segment consists of two types of
spikelets: a sessile (stalkless),
fertile spikelet that is embedded in the axis of the inflorescence and a
pedicellate (stalked), often sterile spikelet with the pedicel fused to the
internode of the inflorescence axis. The spikelets are awnless, narrowly ovate
to triangular in shape, and somewhat flattened.
At maturity, the seedhead breaks
into segments, with the paired spikelets attached. A small, cylindrical
gland-like projection, known as an elaiosome, is located at the base of each
segment. Rich in lipids and proteins, the elaiosome attracts ants that help to
disperse the seed.
Environmental and Economic impact
Rottboellia cochinchinensis is an
invasive aggressive weed under various ecological conditions, in at least 18
crops in 44 countries. It is estimated that more than 3.5 million ha of
cropping lands are infested with Rottboellia cochinchinensis in Central America
and the Caribbean
Rottboellia cochinchinensisis a
serious weed of cotton in Zambia and Zimbabwe and a moderate weed of cotton in
Ethiopia, Mozambique, Sudan, Uganda and Venezuela; a serious weed which effects
on crop yield,
It competes for soil nutrients,
water and light, resulting in reduced crop yields, and also hosts insect pests
and diseases that affect graminaceous crops.
Under optimal conditions,
Rottboellia cochinchinensis plants may begin producing seed six to seven weeks
from emergence and continue to produce seed throughout the growing season. A
single plant can yield between 2,000 and 16,000 seeds.
Recent research (Meksawat and
Pornprom 2010) has shown that Rottboellia cochinchinensis is allelopathic
releasing contains chemicals that inhibit the germination and growth of nearby
plants.
The irritating hairs on the leaf
sheaths discourage foraging by livestock and wild herbivores.
Rottboellia cochinchinensisis a
problem to labourers, as the needle-like hairs on the leaf sheaths break off in
the skin and can cause painful infections.
Michael Hickman
Landscape Design and Rehabilitation Specialist
www.ecoman.co.za
michael@ecoman.co.za
20.03.16
