Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
MINISTRY OF INDUSTRY COMMERCE
AGRICULTURE & FISHERIES
Research & Development Division
Project Report
Comparing the Effectiveness of
Weed Slayer™ Organic Herbicide
against Two Conventional Broad
Spectrum Herbicides Commonly
Used in Jamaica
Prepared by: Sherry-Ann Brown,
Senior Plant Protection Officer
Entomology Laboratory, Plant Protection Unit
Collaborators: Natural Bio Organics Solution Limited, St. Thomas
Reviewed by: Sheldon Elliott
Senior Research Director, Plant Protection Unit
Date: February 5, 2020
Introduction
Weeds are a common problem encountered in the production of agricultural crops. They are
defined to be native or introduced species that have a perceived negative ecological or
economic effect on natural or agricultural systems (Booth, Murphy and Swanton 2013). They
possess properties such as a rapid growth rate and high reproductive capacity that make them
strong competitors for cultivated crops. Weeds pose several threats such as reduction in crop
yields by competing with cultivated crops for space, light, nutrients and water, acting as hosts
for crop pest and diseases as well as interfering with field access and harvesting. As a result
of these negative impacts, it is necessary to control weeds in agricultural fields. One of the
most common practices for weed control in Jamaica and worldwide is the application of
synthetic herbicides. Two of the most commonly utilized active ingredients (a.i.) are
Glyphosate and Paraquat.
Glyphosate is a popular non-selective, broadband herbicide used on the market. It has many
uses from no-tillage cropping systems to precision agriculture (Brevis-Acuña 2004). After
foliar application, it is absorbed by the foliage and translocated throughout stems, leaves and
roots of the entire plant, finally accumulating preferentially in young growing tissues. The
herbicidal effect is based on inhibition of the shikimate pathway enzyme 5-
enolpyruvylshikimic acid-3-phosphate synthase (EPSPS), involved in the biosynthesis of
aromatic amino acids and phenolic compounds (Tesfamariam et al. 2009). Despite its
usefulness studies have shown where the potential of glyphosate to have possible negative
effects on human health. In 2015 the International Agency for Cancer Research (IARC)
classified Glyphosate as “probably carcinogenic to humans” (IARC 2016).
Paraquat’s popularity is related to its quick and non-selective action to kill green plant tissue
upon contact. Additionally, some studies proved that this compound is one of the few
herbicides capable of controlling the growth of weeds that became resistant as a result of
over-use of non-selective glyphosate herbicides (Santos et al. 2013). Paraquat is a bi-
quaternary ammonium salt that is normally synthesized in the form of the dichloride salt
[1,2], it has defoliating and desiccating properties. Its mode of action is based on the
inhibition of Photosystem I, by interfering with intracellular transfer of electrons in
photosynthesis. Half-lives of 16 months and up to 13 years have been reported for paraquat
adsorbed to soil under laboratory and field conditions, respectively (Grillo et al. 2014). It is a
dopaminergic neurotoxin implicated in selective striatal damage and degeneration of the
nigrostriatal dopaminergic pathway, leading to pathogenesis of neurodegenerative diseases
with behavioural abnormalities and loss of motor functions. Several epidemiological and case
control studies revealed that paraquat exposure has a strong correlation with an increased
incidence and development of Parkinson’s disease (Dhaouadi and Adhoum 2009).
While both paraquat and glyphosate has been proven as effective broad spectrum herbicides,
their possible negative impacts on human health necessitates the need for more
environmentally friendly and safer weed control methods including the use of organic
chemicals. Eugenol a natural compound extracted from the leaves, flower buds and stems of
the clove tree is reported to possess herbicidal activity towards a wide range of weed species.
Eugenol has little or no residual activity is considered environmentally safe. Eugenol damage
leaves by increasing cell membrane permeability, which caused membrane damage resulting
in significant leaf injury (Cutler, Tworkoski, and Cutler 2002). It was suggested that eugenol
may cause disruption of mitotic activity by microtubule disorganization or alteration of cell
wall biosynthesis (Amri et al. 2013). Under laboratory conditions, this compound produced
significant reduction in root and shoot lengths of both grass and broadleaf weeds (Ahuja et al.
2014). Vaid et al. (2010) also reported reduced root and shoot lengths of weed species treated
with eugenol as well as reduced weed seed germination. Based on these studied eugenol
appears to be a suitable alternative to synthetic herbicides in managing weed populations in
cultivated crops.
The objective of this study was to compare the effectiveness of the organic herbicide Weed
Slayer ( a.i. Eugenol) with two conventional herbicides (a.i. Paraquat and Glyphosate) for its
broad spectrum herbicidal activity under local conditions.
Methodology
A site was selected at the Bodles Research Station, St. Catherine and sixteen plots, each 4 x 4
m2
laid out using a completely randomized design. The layout consisted of four treatments of
glyphosate, four paraquat, four eugenol and four untreated controls. Eugenol is the a.i. in
Weed Slayer, the organic herbicide being evaluated.
Table 1: Plot layout of herbicide trial
Glyphosate
Eugenol
Eugenol
Paraquat
Control
Control
Glyphosate
Control
Glyphosate
Paraquat
Paraquat
Glyphosate
Eugenol
Control
Paraquat
Eugenol
An initial weed assessment was conducted prior to the application treatments.Using a 1 m2
quadrant the weed density per m2 was determined in each plot. Ten plants were randomly
selected and the number of leaves present on each counted. Treatments were applied to the
plots two days later using a backpack sprayer with a fan nozzle at the manufacturer’s
recommended rates.
Post-treatment weed assessments were carried out once weekly as described above for five
consecutive weeks after herbicides applications. Data collected was analysed using Statistical
Software for Social Sciences (SPSS) version 20.
Results
Weed assessment activities showed the presence of both monocotyledon and dicotyledon
weed species in the trial plots providing different weed types on which broad spectrum
herbicide activity could be tested. The most common species present were Commelina diffusa
(water grass), Sorghum halepense (Johnson grass), Sida acuta (broom weed), Tridax sp.
(button weed) and Parthenum hysterophorus (white top).
Average length and number of leaves on dicotyledon species were 10.6 cm and 9.75 leaves
respectively while average length and number of leaves on monocotyledon species were
11.16 cm and 9.5 leaves, respectively.
There were no significant differences in the total number or monocots, dicots or total weed
species density in the different treatment plots before herbicide application.
Figure 1, mean number of weed species in plots prior to herbicide treatments. Means
followed by the same letter are not significantly different at P ≤ 0.05.
At weeks one and two post herbicide application, all treated plots showed reduction in the
total weed density/m2. While total weed density decreased further in glyphosate and eugenol
treatments at three weeks post treatment, there was an increase in the paraquat treatment
when compared to two weeks after treatment. At four weeks post treatment, total weed
density decreased further in glyphosate treatment while there was an increase in both eugenol
and paraquat treatments when compared to three weeks post treatment. At five weeks post
treatment total weed density increased in all treatments when compared to four weeks.
Similar trends were observed for mean monocot and dicot species densities over the period
with the exception of the glyphosate treatment which showed an increase in the dicot species
at three weeks post treatment when compared to two weeks post treatment. This increase
continued up five weeks post treatment.
Figure 2: Mean total weed density/m2 of herbicide treated plots before and after treatment.
Statistical analyses showed that at week 1 post-treatment there was significant difference (p =
0.000) in total weed density/m2 between the untreated control and all the treated plots when
compared. There was also a significant reduction in the total weed densities of the eugenol
treated as well as the paraquat treated plots (p = 0.008 & 0.000 respectively) when compared
to the week before treatment. Glyphosate treatment showed no significant difference in the
total weed densities before and at one week post treatment (p = 0.114). The paraquat
treatment showed greatest reduction in total weed density after one week. Glyphosate first
showed significant reduction in total weed density at three weeks post herbicide treatment (p
= 0.045). Significant reduction in total weed species density was maintained in all treatments
up to four weeks post treatment. At five weeks post treatment there was a significant increase
in total weed species density (p > 0.05) in all treatments inclusive of the untreated control
when compared to previous weeks.
Mean Total Weed species Density for Individual Herbicide
Treatments over Five Weeks
Figure 3 Change in total weed density/m2 for each treatment over five weeks. The same
letters above the bars indicates no significant difference in the mean total weed species
density for LSD test where P ≤ 0.05.
All herbicide treatments showed significant reduction in the mean dicot density/m2 from one
to four weeks post treatment when compared to the control (p = 0.000). However; there was
no significant reduction (p > 0.05) in the total dicot density/m2 in the neither the eugenol nor
glyphosate treated plots over the trial period when compared to the before treatment densities.
Despite this, both eugenol and glyphosate showed significant reduction (p = 0.013 & 0.000
respectively) in the density/m2
of broomweed species one of the most dominant dicots in the
plot from as early as week one. Significant reduction was maintained up to four weeks post
treatment. Paraquat showed significant reduction in total dicot density/m2 from as early one
week post treatment. Paraquat also showed significant reduction in broomweed species
density from at one week post treatment. Total dicot density/m2 increased significantly (p =
0.000) in all treatments at five weeks post treatment when compared to four weeks post
treatment.
Mean Total Dicot Species Density for Individual Herbicide
Treatments over Five Weeks
Figure 4 Change in total dicot density/m2 for each treatment over five weeks. The same
letters above the bars indicates no significant difference in the mean dicot density for LSD
test where P ≤ 0.05.
Table 2: Mean total Sida acuta (broomweed) density/m2
for each treatment before and after
herbicide applications.
Time Treatment
Control Eugenol Glyphosate Paraquat
Before treatment 25.75 a
30.25 a
32.25 a
14.00 a
1 week post treatment 30.75 a
8.00 b
4.00 b
1.00 b
2 weeks post treatment 38.75 a
3.75 b
0.50 b
0.00 b
3 weeks post treatment 33.00 a
2.50 b
1.00 b
0.75 b
4 weeks post treatment 45.50 a
4.50 b
1.00 b
0.50 b
5 weeks post treatment 44.75 a
19.50 ab
13.50 b
16.25 a
The same letters indicates no significant difference in the mean total Sida acuta density
within treatment for LSD test where P ≤ 0.05.
All herbicide treatments showed significant reduction in the mean monocot density/m2 from
one to four weeks post treatment when compared to the control (p = 0.000). Both eugenol and
glyphosate showed significant reduction (p = 0.05 & p = 0.038 respectively) in total monocot
species density/m2 at three weeks post treatment when compared to before treatment density.
Glyphosate showed further significant reduction (p = 0.022) at four weeks post treatment.
Paraquat showed significant reduction from as early as week one (p = 0.000). This was
maintained up to four weeks post treatment. Eugenol showed significant reduction in water
grass species at two and three weeks post treatment (p = 0.027 & 0.034) respectively when
compared to before treatment while glyphosate showed significant reduction at three and four
weeks post treatment (P = 0.013 & 0.008 respectively). Paraquat showed significant
reduction in water grass at from one week post treatment. This significant reduction was
maintained up to four weeks post treatment.
Mean Total Monocot Species Density for Individual Herbicide
Treatments over Five Weeks
Figure 5 Change in total monocot density/m2 for each treatment over five weeks. The same
letters above the bars indicates no significant difference in the mean monocot density for
LSD test where P ≤ 0.05.
Table 3: Mean total Commelina diffusa (water grass) density/m2
for each treatment before and
after herbicide applications.
Time Treatment
Control Eugenol Glyphosate Paraquat
Before treatment 19.00 a
14.75 a
16.50 a
21.00 a
1 week post treatment 15.00 a
7.75 ab
16.25 a
0.75 b
2 weeks post treatment 14.50 a
3.50 b
11.75 ab
1.50 b
3 weeks post treatment 18.00 a
4.00 b
8.00 b
1.00 b
4 weeks post treatment 14.50 a
7.50 ab
7.25 b
2.25 b
5 weeks post treatment 15.75 a
14.00 a
10.50 ab
15.75 a
The same letters indicates no significant difference in the mean total Commelina diffusa
density within treatment for LSD test where P ≤ 0.05.
Comparison of treatments over the period showed significant difference in total weed
density/m2 between paraquat and eugenol at as well as between paraquat and glyphosate at
one week post treatment ( p = 0.04. & 0.025 respectively) while there was no significant
difference between glyphosate and eugenol (p = 0.806). Significant differences also existed in
the total monocot species/m2 between the paraquat and eugenol treatments and between the
paraquat and glyphosate treatments (p = 0.028 & 0.001 respectively) while no significant
difference existed between eugenol and glyphosate treatments (p = 0.068). There was no
significant difference in the total dicot species among the three herbicide treatment (p > 0.05)
for the duration of the trial. At two weeks post treatment there was no longer a significant
difference in total weed species/m2
among the different herbicide treatments (p > 0.05).
Significant difference was maintained for total monocot species between paraquat and
glyphosate treatments (p = 0.001) but not between paraquat and eugenol treatments (p =
0.151). There was however no significant difference between eugenol and glyphosate
treatments. At three weeks post treatment there was no significant difference among the
herbicide treatments for total weed species density/m2 or total monocot density/m
2 (p > 0.05).
This was maintained for the remainder of the trial.
Figure 6 Mean total weed species/m2
before and after herbicide treatments. For each week,
same letters above the bars indicates no significant difference in the mean weed density for
LSD test where P ≤ 0.05.
Figure 7 Mean total dicot species/m2 before and after herbicide treatments. For each week,
same letters above the bars indicates no significant difference in the mean weed density for
LSD test where P ≤ 0.05.
Figure 8. Mean total monocot species/m2 before and after herbicide treatments. For each
week, same letters above the bars indicates no significant difference in the mean weed
density for LSD test where P ≤ 0.05.
Discussion
Significant difference between total weed species density as well as total monocots and dicots
density in all treatments when compared to the control showed that all treatments were
effective at reducing the weeds present in the trial plots.
Eugenol (Weed Slayer) showed significant reduction in total weed density as early as one
week post treatment. This coincides with the label information stating that results can be seen
in less than a week but may take 10 to 14 days. While the reduction produced in total dicot
density was not significant when compared to before treatment, significant reduction in
broomweed species density, the most dominant dicot in the plots showed that the product is
effective against some dicot species. Significant reduction in total monocot species at three
weeks post treatment indicates that Weed Slayer does possess some level of broad spectrum
activity as advertised.
Comparison of eugenol with paraquat treatments showed that while both treatments produced
significant reduction in the total weed density in treated plots at one week post treatment
when compared to before treatment densities, this reduction was significantly different
between the treatments. Weed density was greater reduced in paraquat treatment than in the
eugenol treatment. However, at week two there was no longer a significant difference
between the treatments implying that while both treatments are effective at reducing total
weed species density, paraquat is a faster acting active ingredient. The two herbicides
produce significant reduction against broomweed species; however, paraquat also produced
significant reduction against total dicot species while eugenol did not, thus indicating that
paraquat is more effective against a wider range of dicot species than eugenol.
Comparing eugenol to glyphosate showed that while eugenol produced a significant
reduction in the total weed species density at one week post treatment when compare to the
before treatment density and glyphosate did not, the difference in the reduction between the
two treatments was not significant. This lack of significant difference between both
treatments was maintained throughout the trial for the total weeds, total dicot densities while
it existed four out of five weeks for the total monocot density. These results indicate
similarities between the treatments. While paraquat shows greatest reduction in weed species
density as early as week one and two post treatment, the greatest reduction is observed in
eugenol and glyphosate treatments at weeks four and five. Glyphosate is a systemic herbicide
therefore, based on the similar behaviour of eugenol it would also appear that eugenol is also
a systemic herbicide.
The surge in weed density in all treatments at week five is due to increase rainfall leading up
to that time. The first three weeks saw the area experiencing mostly dry conditions so weed
growth was poor during that period.
In conclusion, eugenol (Weed Slayer) demonstrates systemic activity and showed significant
reduction in total weed density up to four weeks after treatment under local conditions. It
produced results similar to glyphosate treatment, showing effectiveness against both dicot
and monocot species.
References
Ahuja, Nitina, Daizy R. Batish, Harminder Pal Singh and Ravinder K. Kohli. (2014).
“Herbicidal activity of eugenol towards some grassy and broad-leaf weeds.” Journal of
Pest Science. Doi: 10.1007/s10340-014-0570-x.
Amri, Ismail, Lamia Hamrouni, Mohsen Hanana, and Bassem Jamoussi. 2013. “Reviews on
Phytotoxic Effects of Essential Oils and Their Individual Components: News Approach
for Weeds Management.” International Journal of Applied Biology and Pharmaceutical
Technology 4 (1): 96–114. www.ijabpt.com.
Booth, B.D., Murphy, S.D., Swanton, C.J. 2003.Weed ecology in natural and agricultural
systems. Wallingford Oxon, UK: CABI Publishing
Brevis-Acuña, Juan Carlos. 2004. Assessing Spraying Performance and Weed Control Using
a Precision Weed Control System with Image-Vision. University of California, Davis.
Cutler, S, Thomas Tworkoski, and H Cutler. 2002. “The Synthesis and Biological Evaluation
of Eugenol Derivatives as Potential Herbicidal Agents.” In Plant Growth Regulator
Society of America Meeting.
Dhaouadi, Anissa, and Nafaâ Adhoum. 2009. “Degradation of Paraquat Herbicide by
Electrochemical Advanced Oxidation Methods.” Journal of Electroanalytical Chemistry.
https://doi.org/10.1016/j.jelechem.2009.09.027.
Grillo, Renato, Anderson E.S. Pereira, Caroline S. Nishisaka, Renata De Lima, Kathleen
Oehlke, Ralf Greiner, and Leonardo F. Fraceto. 2014. “Chitosan/Tripolyphosphate
Nanoparticles Loaded with Paraquat Herbicide: An Environmentally Safer Alternative
for Weed Control.” Journal of Hazardous Materials.
https://doi.org/10.1016/j.jhazmat.2014.05.079.
International Agency for Cancer Research. 2016. “Q&A on Glyphosate.” Accessed
September 16, 2019. https://www.iarc.fr/wp-
content/uploads/2018/11/QA_Glyphosate.pdf
Santos, Mónica S F, Gabriela Schaule, A Alves, and Luis M Madeira. 2013. “Adsorption of
Paraquat Herbicide on Deposits from Drinking Water Networks.”
https://doi.org/10.1016/j.cej.2013.06.008.
Tesfamariam, Tsehaye, S Bott, I Cakmak, V Römheld, and G Neumann. 2009. “Glyphosate
in the Rhizosphere-Role of Waiting Times and Different Glyphosate Binding Forms in
Soils for Phytotoxicity to Non-Target Plants.” European Journal of Agronomy 31 (3):
126–32. https://doi.org/10.1016/j.eja.2009.03.007.
Vaid, S., Daizy R. Batish, H.P. Singh and R. K. Kohli. (2010). “Phytotoxic Effects of
Eugenol towards Two Weed Species.” The Bioscan 5(3): 339-341.