Vinegar Herbicide
Title: Evaluation of acetic acid based herbicides for use in broad-spectrum
turfgrass and weed control
Project Leader: David Chinery, Cooperative Extension Educator, Cornell Cooperative
Extension of Rensselaer County, 61 State Street, Troy, NY 12180
Cooperator: Dr. Leslie Weston, Associate Professor, Department of Horticulture,
Cornell University, Ithaca, NY
Type of grant:
Conventional pesticides
Project location(s):
Nationally
Abstract:
This project evaluated the broad-spectrum herbicidal activity of two new
acetic acid type herbicides, three treatments of commercially-available acetic
acid, one herbicidal soap (pelargonic acid) and one commercial herbicide used
in a turfgrass or landscape renovation situation.
Background and justification:
A variety of federal, state and local legislation (either proposed or recently
enacted) mandates the reduction or elimination of chemical pesticide use in
turfgrass management. Commercial landscapers, turfgrass managers, sports field
managers, and golf course superintendents are therefore more interested in
low-toxicity or "organic" products than ever before. Professionals
and homeowners constantly ask Cooperative Extension Educators about alternatives
to pesticides for turfgrass management. A specific interest is in alternatives
for the broad-spectrum herbicides, such as glyphosate (sold as "RoundUp" or
other trade names). Broad-spectrum herbicides are used in a variety of turfgrass
and landscape renovation projects, such as the removal of an existing turfgrass
area to install new sod or seed, the removal of turfgrass for other landscaping
projects, or general weed management in paved and graveled areas. While a new
lawn or garden bed can be managed without pesticides, a broad-spectrum herbicide
is generally needed to create a new bed or lawn, since the other alternatives
(i.e., stripping the existing sod with a sod cutter, rototilling the existing
sod into the soil, etc.) are often not practical or desirable.
Recently, a great deal of interest has been expressed in the use of acetic
acid (vinegar) as a broad-spectrum herbicide. While many anecdotal reports
of success with vinegar have been published in the popular press and on the
internet, research to substantiate these claims is limited. A keyword search
on Michigan State's Turfgrass Information Center, a vast database of turfgrass
abstracts, produced only five matches for acetic acid, none of which detailed
its use as a herbicide. At least two acetic acid-based herbicides were commercially
available for the 2001 growing season. Numerous other "recipes" for
acetic acid herbicides exist using store-bought vinegar (which contains about
5% acetic acid). This project addressed the lack of data by evaluating the
broad-spectrum herbicidal activity of two new acetic acid type herbicides,
one herbicidal soap (containing pelargonic acid), three treatments of commercially
available acetic acid, and a traditional herbicide.
Objectives:
- Observe and document the initial damage done
to turfgrass species and lawn weed species by two new acetic acid type herbicides,
one herbicidal soap (containing pelargonic acid), three treatments of commercially-available
vinegar, and a traditional herbicide.
- Observe and document the long-term
control (with some use of repeated applications) of turfgrass
species and lawn weed species by two new acetic acid type herbicides, one
herbicidal soap (containing pelargonic acid), three treatments of commercially-available
vinegar, and a traditional herbicide.
Procedures:
- The treatments, manufacturers, and treatment schedules are in Table 1
below.
Table 1
| Treatment Number | Treatment name and active
ingredient | Manufacturer | Treatment schedule |
1 | Nature's Glory Weed and Grass Killer (25%
acetic acid) | Monterey Lawn and Garden Products | Sprayed once at 0 days |
2 | Nature's Glory Weed and Grass Killer (25%
acetic acid) | See above | Sprayed 3 times (at 0, 7, and 14 days) or
as per label directions |
3 | BurnOut Weed and Grass Killer (25% acetic
acid) | St. Gabriel Laboratories | Sprayed once at 0 days |
4 | BurnOut Weed and Grass Killer (25% acetic
acid) | See above | Sprayed 3 times (at 0, 7, and 14 days) or
as per label directions |
5 | Scythe (57% pelargonic acid, 3% related
fatty acids) | Mycogen, Inc. | Sprayed once at 0 days |
6 | Scythe (57% pelargonic acid, 3% related
fatty acids) | See above | Sprayed 3 times (at 0, 7, and 14 days) or
as per label directions |
7 | 5% acetic acid | Mallinckrodt, Inc. | Sprayed once at 0 days |
8 | 5% acetic acid | See above | Sprayed 3 times (at 0, 7, and 14 days) |
9 | 10% acetic acid | See above | Sprayed once at 0 days |
10 | 10% acetic acid | See above | Sprayed 3 times (at 0, 7, and 14 days) |
11 | 20% acetic acid | See above | Sprayed once at 0 days |
12 | 20% acetic acid | See above | Sprayed 3 times (at 0,7, and 14 days) |
13 | RoundUp (glyphosate) | Monsanto, Inc. | Sprayed once at 0 days |
14 | Check | | |
The study was to be conducted at the City of Troy Golf Course on unirrigated
rough areas. However, the Capital District experienced prolonged dry weather
starting in May, and turfgrass went into an early dormant period. Thus, the
starting date for the study was delayed in the anticipation that rain would
soon fall and turf would initiate growth. When this did not happen, the study
was conducted in August on a partially irrigated lawn at the project leader's
property in Castleton, NY.
Applications for each product were made either once (at 0 days) or three
times (at 0, 7 and 14 days), except for glyphosate, which was applied only
once. Each treated plot measured 3 ft. by 3 ft. Plots were arranged randomly
within the block. Each treatment was replicated three times. Weed populations
varied somewhat among the replicates (see Table 2). All treatments were evaluated
at 6, 24, and 72 hours and one week after each application, then periodically
thereafter. A 0 - 100% visual rating scale was used, with 0 appearing like
the check plots (no injury) and 100% appearing as total injury. Visual symptoms
of injury (i.e., twisted foliage, discoloration, necrosis, etc.) were noted
for each plant species. Weed populations varied among the replicates, as described
in Table 2. Since prolonged warm fall weather encouraged plant growth, observations
were continued until October 31.
Table 2. Weed populations for three replicate plots
Rep. Number | Weed Population |
1 | 70% quackgrass (Elytrigia repens),
20% crabgrass (Digitaria sanguinalis), 10% ground ivy (Glechoma
hederacea), |
2 | 90% ground ivy, 5% dandelion (Taraxacum
officinale), 5% violet (Viola sp.) |
3 | 60% plantain (Plantago major),
20% Kentucky bluegrass (Poa pratensis), 10% dandelion, 10% ground
ivy |
Results and discussion:*
Since the results for each set of replicate plots were so different, data
for each of the three replicates is shown individually in the following tables.
INTITAL DAMAGE
All acetic acid treatments caused discoloration and damage (control) to the
plots by the 6 hours post treatment observation. Initial damage for all weed
species was a dramatic discoloration and necrosis, with foliage quickly becoming
blackened and water-soaked. No twisting or yellowing was seen for any treatment
or species. Initial control was rated at 90 to 100% for all of the treatments
containing acetic acid, except for the 5% treatments, where for the Rep. 2
plots damage was rated at 70 to 85%. Ground ivy was therefore seen to be initially
slightly more resistant to the lower concentration of acetic acid. By the 24
hours after treatment observation, however, the control in the Rep. 2 plots
had increased to 95% (Tables 3 and 4). By the 72 hours after treatment observation,
control in all plots with an acetic acid product was 95 to 100% (data not presented).
PLOTS SPRAYED WITH ONE APPLICATION (1x PLOTS)
Data for plots sprayed with one application are presented in Table 3. Nature's
Glory and BurnOut performed in a similar manner, giving an average control
for all replicates well above 90% after 24 hours and at two weeks. At five
weeks, good control was still seen except for one Rep. 3 plot where aggressive
Kentucky bluegrass re-grew. At nine weeks and beyond, control was significant
only in Rep. 2 plots (with ground ivy). The 20% acetic acid performed slightly
better than the commercial products, maintaining an average control of 92.7%
at five weeks, and 76% at nine weeks. The 5% acetic acid treatment showed good
control in Rep. 1 for less than two weeks, and for less than five weeks in
Rep. 3, making it much less favorable than the treatments of higher concentration.
Scythe showed good weed suppression for less than five weeks in Reps. 1 and
3, with good control seen for 13 weeks in Replicate 2. Glyphosate, as expected,
provided 90% or better control from two weeks to 13 weeks.
Table 3. Percent control for selected dates for plots sprayed with one application
(1x plots)
| | Treatment | Rep. | 24 Hours | 2 Weeks | 5 Weeks | 9 Weeks | 13 Weeks |
| Nature's Glory | 1 | 1 | 100 | 90.0 | 80.0 | 15.0 | 10.0 |
| | | 2 | 90 | 99.0 | 95.0 | 90.0 | 90.0 |
| | | 3 | 98 | 95.0 | 85.0 | 40.0 | 30.0 |
| | | average | 96.0 | 94.7 | 86.7 | 48.3 | 43.3 |
| | | | | | | | |
| BurnOut | 3 | 1 | 100 | 98.0 | 90.0 | 60.0 | 20.0 |
| | | 2 | 95 | 100.0 | 95.0 | 85.0 | 80.0 |
| | | 3 | 95 | 95.0 | 60.0 | 15.0 | 10.0 |
| | | average | 96.7 | 97.7 | 81.7 | 53.3 | 36.7 |
| | | | | | | | |
| Scythe | 5 | 1 | 100 | 90.0 | 50.0 | 10.0 | 10.0 |
| | | 2 | 98 | 99.0 | 95.0 | 80.0 | 80.0 |
| | | 3 | 98 | 90.0 | 40.0 | 10.0 | 5.0 |
| | | average | 98.7 | 93.0 | 61.7 | 33.3 | 31.7 |
| | | | | | | | |
| 5% Acetic Acid | 7 | 1 | 100 | 40.0 | 5.0 | 5.0 | 5.0 |
| | | 2 | 85 | 99.0 | 95.0 | 85.0 | 85.0 |
| | | 3 | 95 | 85.0 | 40.0 | 10.0 | 10.0 |
| | | average | 93.3 | 74.7 | 46.7 | 33.3 | 33.3 |
| | | | | | | | |
| 20% Acetic Acid | 11 | 1 | 100 | 90.0 | 85.0 | 50.0 | 30.0 |
| | | 2 | 95 | 100.0 | 98.0 | 98.0 | 98.0 |
| | | 3 | 100 | 98.0 | 95.0 | 80.0 | 70.0 |
| | | average | 98.3 | 96.0 | 92.7 | 76.0 | 66.0 |
| | | | | | | | |
| Glyphosate | 13 | 1 | 90 | 100.0 | 100.0 | 95.0 | 90.0 |
| | | 2 | 0 | 98.0 | 100.0 | 100.0 | 100.0 |
| | | 3 | 70 | 95.0 | 98.0 | 95.0 | 95.0 |
| | | average | 53.3 | 97.7 | 99.3 | 96.7 | 95.0 |
PLOTS SPRAYED WITH THREE APPLICATIONS (3x PLOTS)
Data for plots sprayed with three applications are presented in Table 4.
Nature's Glory and BurnOut again performed in a similar manner, showing control
at 90% or above for at least five weeks. By nine weeks, Kentucky bluegrass
and quackgrass began to re-grow, and average control slipped to just above
80%. After 13 weeks, good control (90% or above) was seen only in the Replicate
2 plots on ground ivy. The 20% acetic acid treatments again showed slightly
better control than the commercial products, with an average control of better
than 90% maintained to nine weeks, and average of 81% after 13 weeks. The reason
for this slightly better performance is unknown. The 5% acetic acid treatment
showed surprisingly good control of 90% or better to five weeks, but proved
much less effective at nine and 13 weeks. Scythe showed 90% or better control
at the five week observation, but re-growth was significant thereafter, with
only 20% and 40% control in the Rep. 1 and 3 plots, respectively, by the nine
week observation.
Table 4. Percent control for selected dates for plots sprayed with three
applications (3x plots)
| | Treatment | Rep. | 24 Hours | 2 Weeks | 5 Weeks | 9 Weeks | 13 Weeks |
| Nature's Glory | 2 | 1 | 100 | 98.0 | 95.0 | 70.0 | 20.0 |
| | | 2 | 90 | 100.0 | 100.0 | 98.0 | 90.0 |
| | | 3 | 100 | 100.0 | 98.0 | 75.0 | 50.0 |
| | | average | 96.7 | 99.3 | 97.7 | 81.0 | 53.3 |
| | | | | | | | |
| BurnOut | 4 | 1 | 100 | 98.0 | 90.0 | 60.0 | 20.0 |
| | | 2 | 90 | 100.0 | 100.0 | 98.0 | 95.0 |
| | | 3 | 100 | 100.0 | 100.0 | 95.0 | 80.0 |
| | | average | 96.7 | 99.3 | 96.7 | 84.3 | 65.0 |
| | | | | | | | |
| Scythe | 6 | 1 | 100 | 98.0 | 98.0 | 20.0 | 5.0 |
| | | 2 | 98 | 100.0 | 98.0 | 95.0 | 92.0 |
| | | 3 | 98 | 98.0 | 90.0 | 40.0 | 40.0 |
| | | average | 98.7 | 98.7 | 95.3 | 51.7 | 45.7 |
| | | | | | | | |
| 5% Acetic Acid | 8 | 1 | 100 | 98.0 | 90.0 | 25.0 | 10.0 |
| | | 2 | 70 | 100.0 | 100.0 | 98.0 | 98.0 |
| | | 3 | 100 | 98.0 | 95.0 | 70.0 | 60.0 |
| | | average | 90.0 | 98.7 | 95.0 | 64.3 | 56.0 |
| | | | | | | | |
| 20% Acetic Acid | 12 | 1 | 100 | 98.0 | 98.0 | 85.0 | 60.0 |
| | | 2 | 95 | 100.0 | 100.0 | 98.0 | 98.0 |
| | | 3 | 100 | 100.0 | 98.0 | 92.0 | 85.0 |
| | | average | 98.3 | 99.3 | 98.7 | 91.7 | 81.0 |
| | | | | | | | |
| Glyphosate | 13 | 1 | 90 | 100.0 | 100.0 | 95.0 | 90.0 |
| | | 2 | 0 | 98.0 | 100.0 | 100.0 | 100.0 |
| | | 3 | 70 | 95.0 | 98.0 | 95.0 | 95.0 |
| | | average | 53.3 | 97.7 | 99.3 | 96.7 | 95.0 |
OBSERVATIONS OF INDIVIDUAL WEED SPECIES
Crabgrass and broadleaf plantain
All treatments of acetic acid provided excellent control of crabgrass and
broadleaf plantain, two annual weeds, with virtually no re-growth of these
species during the thirteen weeks. No new seedlings of these species were observed.
If this experiment was conducted earlier in the growing season, or under less
droughty conditions, it is not known whether re-growth or new seedling germination
would have occurred.
Ground ivy
Ground ivy appears to be very susceptible to acetic acid (Rep 2 data in Tables
3 and 4). Virtually all treatments provided excellent initial and long-lasting
control of this usually difficult-to-manage species. Control with acetic acid
in the Rep. 2 plots was still 80% or better for the 1x plots and 90% or better
for the 3x plots. Pelargonic acid also performed well on ground ivy (80% control
in the 1x plots and 92% control in the 3x plots after 13 weeks) as did glyphosate
(100% control after thirteen weeks).
Quackgrass and Kentucky bluegrass
Although all of the acetic acid treatments did a good job of initially controlling
quackgrass, it re-grew by the 9 week observation date for many treatments,
and by thirteen weeks, the percentage of quackgrass for many treatments increased
beyond what was initially seen in the plots (Table 5). In most cases, the increases
were less for the 3x plots than the 1x plots. One acetic acid treatment (20%
acetic acid in the 3x plots) saw a dramatic decrease in quackgrass, however.
Why this happened is unclear and the use of this type of treatment on quackgrass,
bluegrass and other perennial, rhizomatous grasses should be investigated further.
Table 5. Percentage change in quackgrass and Kentucky bluegrass after 13
weeks
| Treatment | Rep. | % change in quackgrass | % change in Kentucky bluegrass |
| Nature's Glory (1x) | 1 | 20 | |
| | 3 | | 36 |
| Nature's Glory (3x) | 1 | 6 | |
| | 3 | | 30 |
| BurnOut (1x) | 1 | -2 | |
| | 3 | | 7 |
| BurnOut (3x) | 1 | 10 | |
| | 3 | | -2 |
| Scythe (1x) | 1 | 20 | |
| | 3 | | 37 |
| Scythe (3x) | 1 | 15.5 | |
| | 3 | | 28 |
| 5% acetic acid (1x) | 1 | 25 | |
| | 3 | | 61 |
| 5% acetic acid (3x) | 1 | 15.5 | |
| | 3 | | 20 |
| 20% acetic acid (1x) | 1 | 0 | |
| | 3 | | 4 |
| 20% acetic acid (3x) | 1 | -40 | |
| | 3 | | -6.5 |
| Glyphosate | 1 | -64 | |
| | 3 | | -17.5 |
Herbicide costs
Cost per liter of some of the products used in this study as well as the
cost to treat a 1,000 square foot area is in Table 6. Costs shown are for products
purchased locally in the Troy, NY, area. The commercial acetic acid herbicide
shown is more than three times more costly on a square foot basis than glyphosate,
and almost three times more costly than pelargonic acid. Acetic acid can be
used at the 5% rate at an attractive price, but its effectiveness is limited.
If 20 % acetic acid or a commercial formulation must be sprayed three times
to achieve effective control of most species, the cost per square foot increases
accordingly.
Table 6. Retail cost per liter and cost of treating 1,000 square feet for
selected herbicides
Product Name | Retail cost per liter | Cost of treating 1,000 square feet |
Nature's Glory Weed and Grass Killer (acetic
acid) | $6.27 | $38.87 |
Scythe (pelargonic acid) | $9.95 | $19.90 |
17.4 M acetic acid (used at 5% concentration) | $10.28 | $10.28 |
17.4 M acetic acid (used at 20% concentration) | $10.28 | $41.12 |
RoundUp (glyphosate) | $51.85 | $12.34 |
Future research
This study showed that acetic acid is useful herbicide. Acetic acid at 5%
concentration (as would be found on the supermarket shelf) provided only short-term
control of most perennial weeds, but did effectively control crabgrass and
plantain. Three applications of acetic acid were seen to be much more effective
than one application in most cases. Pesticide applicators following the advice
of various gardening media who suggest vinegar as an herbicide should be aware
that repeated applications may be necessary. The highest concentration of acetic
acid (20%) gave better control than lower concentrations. Commercial formulations
and the 20% acetic acid treatment provided better control than pelargonic acid
in most cases in this study. Glyphosate was the most effective herbicide, continuing
to show excellent control of virtually all weed species at week thirteen. Acetic
acid is quite costly compared to pelargonic acid or glyphosate, especially
when three applications are needed to achieve good control. However, some pesticide
applicators may opt to use acetic acid despite higher costs if legislation
encourages the use of non-traditional pesticides, and acetic acid is seen as
an environmentally-friendly alternative. Possible ways to improve the performance
of acetic acid and thereby reduce cost per square foot should be examined.
Although the plots where this study was conducted were irrigated, overall droughty
conditions during the summer of 2001 may have influenced herbicide performance
, making it desirable to repeat this work under conditions of "normal" rainfall
and earlier in the year. Plots with more consistent weed species populations
would also allow a meaningful statistical analysis to be generated.
* To simplify this report data for the 10% acetic acid and check treatments
have been omitted.
Thanks to: St. Gabriel Laboratories, Gainesville, VA, for donating "BurnOut" herbicide
and to Mr. Bill Town, Cornell Cooperative Extension of Rensselaer County
Master Gardener for donating acetic acid.
AA: acetic acid IPM report