Transcript Introduction

Cogongrass:
Biology and Impacts
Greg MacDonald
University of Florida
Introduction
• Native to southeast Asia
• Infests nearly 500 million acres worldwide
• Found on every continent
– Except Antarctica
– Tropical and subtropical areas, limited spread
to northern temperate regions
• Considered to be one of the worst weeds
Introduction to U.S.
• First appearance
– Grand Bay, Alabama
– Escape from crate packing in 1912
• Intentional introduction
– Mississippi as a possible forage in 1921
– Florida introduction 1930s and 1940s
• However, little economic (forage) benefit
Cogongrass infestation in the
southeastern United States
points of introduction
Adaptation
• Highly adapted to poor soils
– Ability to survive low nitrogen, phosophorus
– Prefers low pH soils with low organic matter
• Extremely drought tolerant through
specialized rhizome features
• Unique photosynthetic mechanism
– C4 photosynthesis
– Adapted to low light environments (<5% sun)
Pyrogenic
• Fire-based species
• Accumulates excess leaves for fire
• Burns hotter (15-20 C) than normal
understory fires
• Eliminates trees, shrubs, other forbs –
maintains dominance
Cogongrass Biology
– Grows in loose to
compact bunches,
containing several
leaves
– Leaves arise from
a central area
along a rhizome
– Originate directly
from ground level
Leaves
– 1-4 feet in
length, ½ to ¾
inch wide
– Prominent, offcenter, white
mid-rib
– Margins are
finely serrated,
accumulate
silicates
Seed Production
• Predominately in
the spring
• Long, fluffy-white
seedheads
• Mowing, burning
or fertilization
may induce
seedhead
formation
Seeds
– Extremely small
– Attached to a plume of
long hairs
– May be carried long
distances by wind or
humans
– Over 3000 produced
per plant
– Relatively short lived,
< 1 year
Rhizomes
• Comprise over 60%
of total biomass
• 40 tons per acre
• Penetrate soil to a
depth of 4 feet, but
most found in the top
6 to 10 inches
Rhizomes
• Rapid
regenerative
capacity
• Central core to
resist breakage
and drought
tolerance
• Scale leaves
surround each
bud
Rhizomes
• Multiple buds per
rhizome section
• Apical dominance
maintains dormancy
• Evidence of additional
dormancy
mechanisms
Allelopathy
• Rhizomes exude
substances that
retard the growth of
other plants
• Increasing
cogongrass density
excludes other
vegetation
Varieties of Cogongrass?
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Var. major
Var. europa
Var. africana
Var. condensata
Var. latifolia
Imperata brasiliensis – Brazilian satintail
var. ‘Rubra’
• Red variety of
cogongrass
• Sold widely in
the ornamental
trade
• Red Baron,
Japanese Blood
Grass
‘Rubra’
• Will revert to the
normal green biotype
• Conflicting reports on
aggressiveness
• Appears to be coldtolerant
• Genetically related to
I. brasiliensis??