- Reed canarygrass (Phalaris arundinacea L.) is a desirable pasture
grass on wet areas in the Northern United States and Southern Canada,
but it is a serious and troublesome ditchbank weed in the Pacific Northwest
and Rocky Mountain States. The purpose of this study was to learn
more about the development, growth habits, and control of reed canarygrass
on irrigation ditchbanks.
Ninety-seven percent or more of the seed of this species germinated
ediately after harvest under favorable conditions. Seeds stored in
damp sand at constant temperatures of 1 and 23C for periods of time up
to one year did not germinate until they were subjected to alternating
temperatures of 20 and 30C.
The first rhizome development on reed canarygrass seedlings grown
in the greenhouse was observed 26 days after emergence. Within 16 weeks
after emergence, the plants were in bloom and had 48 short rhizomes
(6.5 cm maximum) per plant.
In the field, 88 percent or more of the emergent: shoots on
established plants originated from rhizome or tiller buds located in
the upper 5 cm of soil. Some shoots developed from buds located at
depths up to 20 cm, but none arose from a greater depth.
Several vegetative characteristics of reed canarygrass plants
collected from six irrigation projects in four states differed widely
when grown in a garden at Prosser, Washington. The plant height, seed
weights, panicle length, leaf length, leaf width, number of stems per
plant, stem diameter, and the rate of spread by rhizomes were statistically
different at the 5% level of probability. Large differences in the
color and posture of the leaves were also observed. Plants collected
near Huntley, Montana, were the most vigorous.
Total available carbohydrates in the roots and rhizomes of
established reed canarygrass were not affected by single applications
of 2,2,dichloropropionic acid (dalapon) at 22 kg/ha, 3-amino-s-triazoleammonium
thiocyanate (amitrole-T) at 4.5 kg/ha, or 1,1i-dimethy1-4,4'-
bipyridinium ion (paraquat) at 1.1 kg/ha until 2 months after treatments
were applied in May. By October, single applications of dalapon and
amitrole-T and five repeated applications of paraquat reduced the
carbohydrates 24, 28, and 50 percent, respectively. Two additional
treatments of dalapon or amitrole-T or five additional treatments of
paraquat in the second year of the study did not reduce the carbohydrate
levels below those present during the first year.
Dalapon and trichloroacetic acid (TCA), applied to the soil or to
the senescent foliage in November at rates from 22 to 88 kg/ha, provided
good to excellent temporary control of reed canarygrass without denuding
ditchbanks. Redtop (Avostis alba L.) and reed canarygrass seedlings
developed on the treated areas the following summer and reed canarygrass retained the dominant position unless the seedlings and plants that
escaped the fall treatment were controlled with post-emergence applications
of dalapon or amitrole-T. When the latter plants were controlled, redtop
developed from natural or artificial seeding of the ditchbank and became
the dominant species.
Maximum residue levels of TCA in irrigation water ranged from 104
to 225 ppb following fall applications of TCA at 82 kg/ha to both banks
of three irrigation laterals that ranged from 4 to 14.5 kilometers long.
Average residue levels at the downstream ends of the laterals during the
first four hours that water flowed through them in the spring ranged from
34 to 47 ppb. Eight hours after the initial flow of water through
laterals 4, 8.4, and 14.5 kilometers long, residue levels were less
than 1 ppb in the two shortest laterals and only 2.7 ppb in the longest
lateral. No residues were detectable in the water from any of the
laterals after 48 hours.