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Christine K.
Hayes, Charles H. Gilliam, Gary J. Keever, John W. Olive, and
D. Joseph Eakes
Liriope is a herbaceous perennial commonly propagated
by division. A current nursery practice (Flowerwood Nursery,
Loxley, Alabama) is to delay herbicide application until 2 to
4 weeks after division. While these newly divided liners are
in the nursery, weed infestation commonly occurs, resulting in
the need for extensive hand weeding before preemergence herbicides
are applied. Delayed application of preemergence herbicides is
based on concerns that root suppression will occur with use of
dinitroaniline (DNA) herbicides and that foliar injury will result
following applications of non-DNA herbicides. The primary mode
of action of DNA herbicides is through root suppression, but
these herbicides have a low solubility, reducing their movement
in the root zone.
Most of the preemergence herbicides used in nursery and landscape
crop production are DNA herbicides or contain a DNA component.
The objective of our study was to evaluate several preemergent
herbicides for injury and root growth suppression of Liriope
muscari ‘Big Blue’ immediately after division and
potting.
METHODS
On April 22, 1997 ‘Big Blue’ liriope was divided, and
single bibs were planted in Lerio 3.25 inch SR 325 pots at the
Paterson Greenhouse Complex, Auburn, Alabama. Shoots were not
cut back and roots were pruned to 3 inches. Bibs were potted
in a pinebark:sand (6:1 by volume) medium amended per cubic yard
with 10 pounds 18-6-12 Osmocote (Scotts Co.), 5 pounds dolomitic
lime, and 1.5 pounds Micromax (Scotts Co.).
On April 24, 1997, 2 days after division, herbicides were applied
(herbicides and rates are found in Table 1). Following treatment,
containers were placed on a gravel bed in full sun and irrigated
as needed with overhead irrigation. Experiment 2 was similar
to experiment 1 with the following exceptions: liriope was divided
on July 1, 1997 and treated on July 3, 1997.
RESULTS
EXPERIMENT 1. In experiment 1, root ratings of plants treated
with granular-applied preemergent herbicide were similar to those
of non-treated controls at both 60 and 90 DAT with the exception
of plants treated with Regal Kade at 90 DAT which exhibited a
slightly lower root rating than control plants (Table 1). Liriope
treated with Surflan or Surflan + Gallery exhibited suppressed
root ratings at both 60 and 90 DAT when compared to non-treated
controls. At both 60 and 90 DAT liriope treated with Gallery
alone had similar root ratings to non-treated liriope, indicating
root growth inhibition was caused by Surflan. When evaluating
new shoot number (bibs), Surflan-treated plants had the lowest
number of new shoots at 60 and 90 DAT, with 34% and 33% fewer
shoots, respectively, than non-treated control plants. Plants
treated with Predict exhibited bleached foliage at 30, 60, and
90 DAT with some bleaching on new growth at 90 DAT. Plants treated
with Regal O-O had a higher foliar rating at 30 DAT, but not
60 or 90 DAT, than did control plants.
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Table 1. Root Rating,
Foliar Rating, and Bib Number per Container of Newly Divided
Liriope Treated with 15 Preemergent Herbicides, Experiment 1 |
|
|
Rate |
Root rating1 |
Foliar rating2 |
Bib number |
|
Herbicide |
lb ai/A |
60 DAT3 |
90 DAT |
30 DAT |
60 DAT |
90 DAT |
60 DAT |
90 DAT |
|
Ronstar 2G AG |
4.0 |
1.8 |
3.0 |
2.1 |
1.8 |
1.5 |
2.9 |
4.5 |
|
Regal O-O |
3.0 |
1.9 |
3.1 |
2.4 |
1.9 |
1.5 |
2.3 |
4.0 |
|
OH-2 3G |
3.0 |
2.0 |
3.4 |
2.3 |
1.8 |
1.4 |
2.5 |
4.7 |
|
Kade G |
1.0 |
1.9 |
2.9 |
1.7 |
1.9 |
1.6 |
2.6 |
4.5 |
|
Snapshot 2.5 TG |
4.0 |
2.0 |
3.8 |
1.9 |
1.8 |
1.5 |
2.7 |
4.6 |
|
Pendulum 2G |
3.0 |
2.2 |
3.6 |
1.9 |
1.5 |
1.3 |
3.3 |
5.6 |
|
Star II |
2.4 |
2.0 |
3.3 |
2.0 |
1.9 |
1.4 |
2.2 |
4.8 |
|
Factor 65 WDG |
1.0 |
1.8 |
3.1 |
2.0 |
1.7 |
1.4 |
2.4 |
4.4 |
|
Pen. 60 WDG |
3.0 |
1.8 |
3.3 |
1.8 |
1.7 |
1.5 |
2.5 |
4.5 |
|
Surflan 4AS |
3.0 |
1.3 |
2.3 |
1.7 |
1.5 |
1.8 |
1.9 |
3.2 |
|
Predict |
3.0 |
1.6 |
3.1 |
2.6 |
2.7 |
2.3 |
2.9 |
4.3 |
|
Gallery |
1.0 |
1.8 |
3.2 |
1.8 |
1.9 |
1.5 |
2.2 |
4.9 |
|
Image |
0.5 |
1.7 |
3.3 |
2.0 |
1.8 |
1.8 |
2.8 |
5.2 |
|
Surflan + Gallery |
3.0 + 1.0 |
1.3 |
2.6 |
2.0 |
2.0 |
1.5 |
2.0 |
3.8 |
|
Ronstar 2G |
4.0 |
2.0 |
3.8 |
2.1 |
1.7 |
1.6 |
3.2 |
4.9 |
|
Control |
|
1.9 |
3.5 |
1.9 |
1.7 |
1.25 |
2.9 |
4.8 |
1 Root rating
scale of 1-5 based on percent root coverage at the substrate-container
interface where 1=0% root coverage, 2=25% root coverage, 3=50%
root coverage, 4=75% root coverage, and 5=100% root coverage.
2 Foliar rating based on a scale of 1-5 where 1=no
injury, 3=moderate injury, and 5=dead plant.
3 DAT = days after treatment. |
AT 90 DAT, plants treated with Surflan, Image,
or Predict had greater phytotoxicity ratings than untreated control
plants. Injury to plants treated with Image or Predict was characterized
by bleached spots or bands on the old and new foliage.
EXPERIMENT 2. Data from experiment 2 generally agreed with that
of experiment 1 in that granular herbicides had root ratings
similar to non-treated control plants (Table 2). Plants treated
with Regal O-O at 90 DAT were the only plants treated with granular
herbicides to exhibit root ratings slightly lower than non-treated
control plants. Again, plants treated with Surflan or Surflan
+ Gallery had lower root ratings than non-treated control plants
at 30, 60, and 90 DAT. Image-treated plants had lower root ratings
at 30 and 90 DAT than non-treated control plants.
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Table
2. Root Rating and Foliar Rating of Newly Divided Liriope Treated
with 15 Preemergent Herbicides, Experiment 2 |
|
|
Rate |
Root rating 1 |
Foliar rating 2 |
|
Herbicide |
kg ai/ha |
30 DAT3 |
60 DAT |
90 DAT |
30 DAT |
60 DAT |
90 DAT |
|
Ronstar 2G AG |
4.0 |
1.5 |
3.1 |
3.7 |
1.5 |
1.3 |
1.7 |
|
Regal O-O |
3.0 |
1.5 |
2.8 |
3.2 |
1.9 |
1.8 |
2.8 |
|
OH-2 3G |
3.0 |
1.5 |
3.3 |
4.0 |
1.8 |
1.8 |
2.3 |
|
Kade G |
1.0 |
1.5 |
2.6 |
3.6 |
1.8 |
1.3 |
1.8 |
|
Snapshot 2.5 TG |
4.0 |
1.6 |
3.3 |
3.7 |
1.6 |
1.4 |
1.4 |
|
Pendulum 2G |
3.0 |
1.5 |
3.2 |
3.8 |
1.5 |
1.2 |
1.8 |
|
Star II |
2.4 |
1.5 |
3.1 |
3.8 |
1.5 |
1.6 |
1.8 |
|
Factor 65 WDG |
1.0 |
1.6 |
3.2 |
3.8 |
1.3 |
1.2 |
1.6 |
|
Pendulum 60 WDG |
3.0 |
1.5 |
3.5 |
4.0 |
1.7 |
1.3 |
1.5 |
|
Surflan 4AS |
3.0 |
1.3 |
2.0 |
3.2 |
1.6 |
1.4 |
1.7 |
|
Predict |
3.0 |
1.4 |
3.3 |
3.8 |
2.3 |
1.6 |
1.8 |
|
Gallery |
1.0 |
1.5 |
3.3 |
4.0 |
1.6 |
1.2 |
1.5 |
|
Image |
0.5 |
1.2 |
2.9 |
3.1 |
1.8 |
1.3 |
1.7 |
|
Surflan + Gallery |
3.0 + 1.0 |
1.2 |
1.9 |
2.6 |
1.5 |
1.3 |
1.3 |
|
Ronstar 2G |
4.0 |
1.5 |
3.2 |
3.7 |
1.6 |
1.3 |
1.7 |
|
Control |
|
1.4 |
3.2 |
4.1 |
1.3 |
1.2 |
1.3 |
1 Root rating
scale of 1-5 based on percent root coverage at the substrate-container
interface where 1 = 0% root coverage, 2 = 25% root coverage,
3 = 50% root coverage, 4 = 75% root coverage, and 5 = 100% root
coverage.
2 Foliar rating based on a scale of 1-5 where 1 =
no injury, 3 = moderate injury, and 5 = dead plant.
3 DAT = days after treatment. |
Phytotoxicity ratings were generally higher
in experiment 2 than in experiment 1. Plants in the second study
were in a softer stage of growth when divided, possibly accounting
for more injury from herbicides. Also, higher temperatures in
July compared to April may have contributed to greater injury.
As in experiment 1, Predict-treated plants exhibited bands of
bleached foliage and had higher phytotoxicity ratings than control
plants at 30 and 90 DAT. Regal O-O and OH-2, which both contain
oxyfluorfen, caused foliar damage later in the study (60 and
90 DAT).
Results of these tests showed root or shoot growth of ‘Big
Blue’ liriope was not affected by most granular herbicides
when they were applied immediately after division. Surflan consistently
suppressed root growth, while Predict-treated plants exhibited
bleached foliage on old and new growth. All other spray-applied
herbicides were safe when applied immediately after division
to ‘Big Blue’ liriope.
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