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Flaming, Glyphosate, Hot Foam and Nonanoic Acid for Weed Control: A Comparison

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Synthetic herbicides are commonly used in weed management, however, 70 years of use has led to weed resistance and environmental concerns. These problems have led scientists to consider alternative methods of weed management in order to reduce the inputs and impacts of synthetic herbicides. The aim of this experiment was to test the level of weed control using four weeding methods: glyphosate applied at an ultra-low volume, the organic herbicide nonanoic acid, flaming, and hot foam. The results showed that weed control was effective only when flaming and hot foam were applied (99% and 100% weed control, respectively). Nonanoic acid at a dose of 11 kg a.i. ha−1 diluted in 400 L of water did not control developed plants of Cyperus esculentus (L.), Convolvulus arvensis (L.) and Poa annua (L.). Glyphosate at a dose of 1080 g a.i. ha−1 (pure product) only controlled P. annua (L.), but had no effect on C. esculentus (L.) and C. arvensis (L.). After the aboveground tissues of weeds had died, regrowth began earlier after flaming compared to hot foam. There was no regrowth of P. annua (L.) only after using hot foam and glyphosate. Hot foam was generally better at damaging the meristems of the weeds. In one of the two experiment sites, significantly more time was needed after the hot foam to recover 10% and 50% of the ground compared to flaming. The time needed to recover 90% of the ground was on average 26–27 days for flaming and hot foam, which is the time that is assumed to be required before repeating the application. A total of 29 days after the treatments, weeds were smaller after flaming, glyphosate and hot foam compared to nonanoic acid and the control, where they had more time to grow.
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Agronomy 2020, 10, 129; doi:10.3390/agronomy10010129 www.mdpi.com/journal/agronomy
Article
Flaming, Glyphosate, Hot Foam and Nonanoic Acid
for Weed Control: A Comparison
Luisa Martelloni *, Christian Frasconi, Mino Sportelli, Marco Fontanelli, Michele Raffaelli
and Andrea Peruzzi
Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy;
christian.frasconi@unipi.it (C.F.); mino.sportelli@phd.unipi.it (M.S.); marco.fontanelli@unipi.it (M.F.);
michele.raffaelli@unipi.it (M.R.); andrea.peruzzi@unipi.it (A.P.)
* Correspondence: lmartelloni@agr.unipi.it (L.M); Tel.: +39-050-2218966
Received: 18 December 2019; Accepted: 11 January 2020; Published: 15 January 2020
Abstract: Synthetic herbicides are commonly used in weed management, however, 70 years of use
has led to weed resistance and environmental concerns. These problems have led scientists to
consider alternative methods of weed management in order to reduce the inputs and impacts of
synthetic herbicides. The aim of this experiment was to test the level of weed control using four
weeding methods: glyphosate applied at an ultra-low volume, the organic herbicide nonanoic acid,
flaming, and hot foam. The results showed that weed control was effective only when flaming and
hot foam were applied (99% and 100% weed control, respectively). Nonanoic acid at a dose of 11 kg
a.i. ha1 diluted in 400 L of water did not control developed plants of Cyperus esculentus (L.),
Convolvulus arvensis (L.) and Poa annua (L.). Glyphosate at a dose of 1080 g a.i. ha1 (pure product)
only controlled P. annua (L.), but had no effect on C. esculentus (L.) and C. arvensis (L.). After the
aboveground tissues of weeds had died, regrowth began earlier after flaming compared to hot foam.
There was no regrowth of P. annua (L.) only after using hot foam and glyphosate. Hot foam was
generally better at damaging the meristems of the weeds. In one of the two experiment sites,
significantly more time was needed after the hot foam to recover 10% and 50% of the ground
compared to flaming. The time needed to recover 90% of the ground was on average 2627 days for
flaming and hot foam, which is the time that is assumed to be required before repeating the
application. A total of 29 days after the treatments, weeds were smaller after flaming, glyphosate
and hot foam compared to nonanoic acid and the control, where they had more time to grow.
Keywords: alternative methods; herbicide; organic; pelargonic acid; thermal tools; ultra-low
volume
1. Introduction
Synthetic herbicides are commonly used in weed management, however, after 70 years of use,
this has led to weed resistance [3,4] and environmental concerns [5]. These problems have stimulated
scientists into investigating alternatives and integrated systems of weed management to reduce the
inputs and impacts of synthetic herbicides [5].
One method of reducing the environmental impact of chemically synthesized herbicides is to
use ultra-low volume (ULV) spraying, i.e., rates of less than 5 L ha1 [6]. Rotary atomizers distribute
large quantities of small droplets efficiently, enabling a less active ingredient to be applied compared
to conventional water-based methods using emulsifiable concentrate formulations [7,8]. Glyphosate
applied in low water volumes means that lower doses of herbicides can be used on more sensitive
weed species, but it also improves the herbicide activity on weed species that are difficult to control
[9].
Agronomy 2020, 10, 129 2 of 15
Alternative methods to the use of chemical-synthesis herbicides are alternative organic
herbicides and thermal weed control [5,10,11]. Nonanoic acid (also called pelargonic acid) is a contact,
non-selective, non-translocating, post-emergence non-synthetic herbicide [10,12]. It is a fatty acid,
which kills plants by destroying the cell membranes, leading to rapid desiccation of plant tissues, and
providing non-residual weed control [10,12]. Thermal weed control involves heat being transferred
to plant material (leaves, stems, flowers, propagules, etc.) to destroy cell structures, and leads to the
denaturation of proteins [11,13,14]. Flaming is the primary heat source for weed control in agriculture
and on hard surfaces in urban areas [11,1518]. Hot foam is an evolution of the hot water weed control
method, modified by the addition of biodegradable foaming agents, and was first patented in 1995
[14,19]. Hot foam weed control is a non-toxic technique and is applicable to numerous weed species
[5].
When a method of weed control is applied, in addition to its effectiveness, it is important to also
evaluate the weed regrowth after the above-ground tissues of weeds have died [20]. In fact, most
thermal methods affect the above-ground portion of the plants, however, some weeds (i.e., perennial
weeds) may regrow from their below-ground components and thus a repeated application of the
thermal control is required [5,21,22].
Hot foam has been used to control weeds in cotton fields [22], but the application of this high-
energy demand weed control method (due to the high thermal capacity of water [23]) is more realistic
in urban area contexts (e.g., on pavements) [24]. The growth of weeds on road pavements is different
from that in a field, because the characteristics of the pavements affect the weed growth (i.e., fewer
appear on frequently used roads with small joints than in infrequently used pavements with medium
or wide joints) [24,25]. In Sweden hot foam was used to control weeds along railways [14]. Flaming
can be used successfully for controlling weeds in both agricultural and urban area context
[15,16,26,27].
The aim of this experiment was to test the weed control effect of different weeding methods:
glyphosate applied at an ultra-low volume, organic herbicide nonanoic acid, flaming, and hot foam.
Weed regrowth after the death of the vegetative weed tissues and weed dry biomass 29 days after
treatment application were also evaluated.
2. Material and Methods
2.1. Experimental Set up, Design and Treatment
A two-site experiment was conducted at the experimental farm of the University of Pisa (Pisa,
Italy) (43°4033.1′ N 10°18′41.2′ E). The study was replicated twice at each site. The two sites (sites I
and II) differed in terms of weed population composition typology.
At site I, the major weeds was Cyperus esculentus (L.), Convolvulus arvensis (L.) and Poa annua (L.),
each accounting for 25% of the weed population. Other weeds randomly present in the field were
Anagallis arvensis (L.), Avena fatua (L.), Cirsium arvense (L.), Conyza canadensis (L.), Eleusine indica (L.),
Inula viscosa (L.), Lolium rigidum (Gaud.), Picris echioides (L.), Plantago major (L.), Silene vulgaris
(Moench), Sonchus oleraceus (L.), Stellaria media (L.), Tordylium apulum (L.), Trifolium repens (L.), and
Veronica persica (L.), with an overall total of 25% of the weed population. The majority of C. esculentus
(L.) were at the 6-tiller visible growth stage, P. annua (L.) was at the inflorescence emergence
(inflorescence fully emerged) growth stage, and C. arvensis (L.) was at the 8–9 true-leaf growth stage
[28]. At site II, the major weed was C. esculentus (L.), which accounted for 90% of the weed population.
Other weeds randomly present in the field were A. arvensis (L.), C. canadensis (L.), C. arvensis (L.),
Erodium cicutarium (L.), Euphorbia prostrata (Aiton), P. echioides (L.), P. major (L.), S. oleraceus (L.), T.
repens (L.), and V. persica (L.), with an overall total of 10% of the weed population. C. esculentus (L.)
was at the 6-tiller visible growth stage [28].
Weed species and percentages of single species in the total weed population were identified
based on visual estimates. The sites were uncultivated (i.e., meadows under orchards) and the weeds
had been managed periodically with mowing before the experiments were carried out. The soil was
loam in both sites.
Agronomy 2020, 10, 129 3 of 15
Glyphosate (360.00 g L1 of active ingredient) was applied pure (i.e., without diluting in water).
The product used was GLIFENE HP (Diachem S.p.A., Caravaggio, Italy), which contained glyphosate
as isopropylamine (IPA) salt and surfactants. The product was applied with an ultra-low volume
sprayer (MANKAR-P 3050 Flex, Mantis ULV®, Geesthacht, Germany) (Figure 1b) at a dose of 3 L
ha1 (i.e., 1080 g a.i. ha1). The machine was equipped with a segment rotation atomizer, which
produces small droplets with a uniform size of about 150 μm [29]. Flaming was applied manually
with a prototype of a back-pack flaming machine developed at the University of Pisa [15] (Figure 1a).
The dose was 150 kg ha1 of liquefied petroleum gas (LPG) based on previous experiments where this
dose was found to be effective in controlling developed weeds [16,17]. The burner was 0.3 m wide
and operated at 6 cm above the ground. Hot foam was applied using a Foamstream® MW Series
(Weedingtech Ltd., London, UK) [30]. The solution used (Foamstream V4) was a 100% blend of plant
oils and sugar (e.g., alkyl polyglucoside surfactants) [31]. The emission class is equivalent to a Euro 5
[32]. The machine flow rate was 0.2 L s1 (96% water and 4% Foamstream V4) and the dose applied
was 8.33 kg m2. The manufacturer advised that Foamstream V4 percentage in the total flow rate
could be varied between 0.5% and 5% depending on the client’s application. This dose was based on
a previous experiment where it provided the highest weed control effect and the slowest weed
regrowth [20]. The hot foam distribution tool was 0.3 m wide and operated at 5 mm above the ground
(Figure 1c). Pure nonanoic acid (Beloukha, Novamont, Novara, Italy) was applied using a sprayer
(Acuspray, Techneat engineering ltd, Ely, Cambridgeshire, UK) (Figure 1d) at a dose of 16 L ha1 (i.e.,
11 kg a.i. ha1) diluted in 400 L of water.
Figure 1. Machines used in the experiments for weed control: (a) prototype back-pack flaming
machine; (b) ultra low volume sprayer (MANKAR-P 3050 Flex, Mantis ULV®, Geesthacht, Germany)
used for glyphosate application; (c) hot foam distribution tool (Weedingtech Ltd., London, UK); (d)
sprayer (Acuspray, Techneat engineering ltd, Ely, Cambridgeshire, UK) used for nonanoic acid
distribution.
Agronomy 2020, 10, 129 4 of 15
Treatments were applied on 14 May 2019 (repetition I) and on 02 July 2019 (repetition II) in both
sites. Cumulative rainfalls were 93, 4, 94 mm in May, June and July, respectively, and the average
temperatures were 15, 23, 25 °C in May, June, and July, respectively.
The experimental design was a randomized block design with four blocks. The five treatments
(control, flaming, glyphosate, hot foam, and nonanoic acid) were applied in each block for a total of
20 plots per site. Plots were 2 m long and 0.3 m wide. Plots were 0.3 m wide based on the width of
the hot foam application tool and flaming burner. A space of 2.5 m between the plots has been left in
order to avoid drift effect due to the use of the herbicides.
2.2. Data Collection
Measurements of ground covered by the total population of weeds were used to estimate weed
control (i.e., from treatments application to death of weeds above-ground tissues) and weed regrowth
(i.e., from death of weeds above-ground tissues to 27 days after the treatment application). These
measurements were estimated from digital images using IMAGING Crop Response Analyser [33].
The digital images, one for each plot, were taken from an area of 0.075 m2 (30 cm × 25 cm) at the center
of each plot (with the same geographical coordinates). Photographs of the weed cover for evaluating
the weed control were taken 1 day before, and 1 and 2 days after treatments. Weed cover photographs
for the evaluation of the weed regrowth were taken 3, 7, 10, 17 and 27 days after treatments. The
distance between the weeds and the camera was constant (i.e., 30 cm from the ground), and high
contrast was prevented by using an umbrella. The brightness of the digital images was equalized
before analysis. The digital image analysis was as described in Rasmussen et al. [34], which,
summarizing, counted the percentage of green pixels on the whole pixels of the photograph. The
green weed biomass was collected 29 days after treatment at the center of each plot (i.e., 0.075 m2
area) by cutting the weeds at ground level. Cut plants were dried at 105 °C to a constant weight. The
dry weight was then converted into g m2.
2.3. Statistical Analysis
Data normality was assessed using the ShapiroWilk test. Other tests consisted of the Student’s
t-test to verify that the mean error was not significantly different from zero, the Breusch-Pagan test
for homoscedasticity, and the DurbinWatson test for autocorrelation.
The weed control in each site was modeled in a linear mixed model using the R software [35]
extension package ‘lmerTest’ (tests in linear mixed effects models) [36]. A logit transformation of
weed cover data was performed. The treatment, evaluation date and repetition of the experiment
were fixed factors. Correlated random intercepts and slopes were fitted between blocks and fixed
factors. Weed regrowth was modeled in a full model as above, however, a comparison between the
full models and the reduced models (without the logit transformation and no random factors)
resulted in p-values equal to 1 and higher Akaike information criterion (AIC) and Bayesian
information criterion (BIC) (AIC = 705.02 and BIC = 875.57 of the full model vs AIC = 303.55 and BIC
= 230.45 of the reduced model, at site I; and AIC = 533.03 and BIC = 703.58 of the full model vs AIC
= 458.79 and BIC = 385.70 of the reduced model, at site II), therefore the reduced models were used.
The weed dry biomass was modeled in a mixed model where the treatment, site, and repetition were
the fixed factors. Correlated random intercepts and slopes were fitted between blocks and fixed
factors. An analysis of variance was performed for each model. The extension package ‘ggplot2’
(elegant graphics for data analysis) [37] was used to plot all the graphs.
The comparisons between pairs of estimated values were computed by estimating the 95%
confidence interval of the difference between the values (Equation (1)):
 (difference)=()± 1.96+ , (1)
where (x1) is the mean of the first value, (x2) is the mean of the second value, (SEx1) is the standard
error of (x1), and (SEx2) is the standard error of (x2) . If the resulting 95% confidence interval (CI) of
Agronomy 2020, 10, 129 5 of 15
the difference between values did not cross the value 0, the null hypothesis that the compared values
were not different was rejected.
3. Results
3.1. Weed Control
The p-values resulting from the analysis of variance are reported in Table 1. At site I, weed
control was influenced by the treatment, evaluation date, and interaction between the two. At site II
the interaction between the treatment, evaluation date, and repetition of the experiment were also
significant. Tables 2 and 3 report the weed control least squares means and standard errors of weed
cover percentage logit transformed one day before, and one and two days after treatments at sites I
and II, respectively. The inverse transformed values and 95% confidence intervals are plotted in
Figures 2 and 3, for site I and II, respectively.
Table 1. Weed control type III analysis of variance with Satterthwaites method resulting from the
linear mixed model where the treatments (control, flaming, glyphosate, hot foam, and nonanoic acid),
evaluation date (one day before, and one and two days after the treatments) and repetition of the
experiment (I and II) were used as fixed factors at sites I and II, respectively. Significant p-values are
shown in italics.
Site I
Site II
p-Value
p-Value
Treatment
<0.001
<0.001
Date
<0.001
<0.001
Repetition
0.161
0.134
Treatment: Date
<0.001
<0.001
Treatment: repetition
0.588
0.112
Date: repetition
0.896
0.160
Treatment: date: repetition
0.865
0.037
Table 2. Weed control least squares means and standard errors (SE) of weed cover percentage logit
transformed as affected by the different treatments, repetition of the experiment, and evaluation date
(one day before, and one and two days after treatments) at site I.
Treatment
Logit [Weed Cover (%)] (±SE)
1 DBT
1 DAT
2 DAT
Control
1.55 (0.365)
1.72 (0.399)
1.07 (0.365)
Flaming
1.18 (0.400)
4.53 (0.381)
5.16 (0.399)
Glyphosate
1.55 (0.415)
0.85 (0.375)
1.11 (0.397)
Hot foam
1.97 (0.476)
6.98 (0.507)
7.07 (0.466)
Nonanoic acid
1.84 (0.430)
1.31 (0.451)
1.18 (0.417)
Control
1.11 (0.409)
1.40 (0.483)
0.97 (0.426)
Flaming
0.89 (0.468)
5.04 (0.494)
5.15 (0.482)
Glyphosate
1.29 (0.367)
0.82 (0.378)
0.52 (0.366)
Hot foam
1.50 (0.437)
8.34 (0.511)
7.73 (0.442)
Nonanoic acid
1.50 (0.406)
1.00 (0.473)
0.26 (0.410)
1 DBT, 1 DAT, and 2 DAT: one day before, and one and two days after the treatments, respectively.
Agronomy 2020, 10, 129 6 of 15
Figure 2. Weed control bar graph of back-transformed means (Table 2) and the 95% confidence
interval as affected by the treatments (control, flaming, glyphosate, hot foam and nonanoic acid),
repetition (I and II) and evaluation date at site I; 1 DBT, 1 DAT and 2 DAT: one day before, and one
and two days after the treatment, respectively.
Table 3. Weed control least squares means and SE of weed cover percentage logit transformed as
affected by the different treatments, repetition of the experiment, and evaluation date (one day before,
and one and two days after treatments) at site II.
Treatment
logit [Weed Cover (%)] (±SE)
1 DBT
1 DAT
2 DAT
Control
0.50 (0.175)
0.53 (0.234)
0.64 (0.197)
Flaming
1.19 (0.240)
5.70 (0.218)
4.59 (0.262)
Glyphosate
0.90 (0.298)
1.36 (0.207)
1.36 (0.316)
Hot foam
1.07 (0.264)
5.48 (0.351)
5.37 (0.270)
Nonanoic acid
0.89 (0.226)
0.18 (0.172)
0.28 (0.229)
Control
0.54 (0.183)
0.64 (0.252)
0.75 (0.177)
Flaming
0.49 (0.208)
5.82 (0.198)
4.17 (0.209)
Glyphosate
0.59 (0.280)
0.98 (0.194)
0.99 (0.280)
Hot foam
1.25 (0.271)
6.30 (0.364)
5.41 (0.257)
Nonanoic acid
0.38 (0.240)
0.18 (0.204)
0.04 (0.220)
1 DBT, 1 DAT, and 2 DAT: one day before, and one and two days after the treatments, respectively.
Agronomy 2020, 10, 129 7 of 15
Figure 3. Weed control bar graph of back-transformed means (Table 3) and the 95% confidence
interval as affected by the treatments (control, flaming, glyphosate, hot foam and nonanoic acid),
repetition (I and II) and evaluation date at site II; 1 DBT, 1 DAT and 2 DAT: one day before, and one
and two days after the treatment, respectively.
In both sites and repetitions of the experiment, only the flaming and hot foam treatments were
able to control weeds and showed a significant reduction in weed cover one and two days after
treatments compared with one day before their application. On the other hand, after the nonanoic
acid and glyphosate applications, there was no weed cover reduction (Figures 2 and 3, Tables 2 and
3).
In the two repetitions at site I, one and two days after the application of flaming, weed cover
was statistically similar and was on average 0.7%. Also after hot foam application, there were no
statistical differences the weed cover in the two repetitions, both one and two days after the
treatments, which on average was 0% (Figure 2, Table 2). At site II, weed cover one day after flaming
was similar in the two experiment replications (on average 0.3%), and significantly lower compared
with two days after its application in both replications, which was on average 1.3%. This thus
suggests that there was an early start of the regrowth already two days after the treatment
application. Weed cover after hot foam was similar between one and two days after the treatment
application in both replications, which was on average 0.4% (Figure 3, Table 3).
Weed cover estimated one and two days after the application of treatments was statistically
lower in plots where hot foam was applied compared with the flamed plots in both repetitions of site
I. At site II, in both repetitions, weed cover one day after the treatments was similar between flaming
and hot foam, whereas two days after treatments, weed cover after hot foam was significantly lower
than after flaming (Figures 2 and 3, Tables 2 and 3).
3.2. Weed Regrowth
At site I, the weed composition observed 27 days after the application of the treatments showed
a shift in the plots (both repetitions) where glyphosate and hot foam were applied compared to that
observed before the start of the experiment. In these plots P. annua (L.) was no longer present,
whereas it was still observed in the plots where the other treatments had been applied. At site II, an
increase in C. arvensis (L.) was observed, which represented 30% of the final weed population (27
days after treatments) in all the treated plots and the control. In both sites and repetitions, regrowth
was observed starting from the meristems, and the weed coverage was not due to a new weed
infestation from seeds.
Agronomy 2020, 10, 129 8 of 15
The p-values from the analysis of variance are reported in Table 4, and the coefficients of the
regressions in Table 5. The regression lines with all the points and 95% confidence interval bands of
percentage weed cover as affected by the treatments (control, flaming, glyphosate, hot foam and
nonanoic acid), the repetitions (I and II) and the evaluation dates (3, 7, 10, 13, 17 and 27 days after the
treatments) for both sites are shown in Figure 4. At site I, weed cover regrowth was affected by the
treatments, evaluation date, and their interaction, whereas at site II, the interaction between
treatments, evaluation date and the repetition was also significant (Table 4).
Table 4. Weed regrowth analysis of variance resulting from the linear model, where weed coverage
was affected by the treatments (control, flaming, glyphosate, hot foam, and nonanoic acid), the
evaluation date (3, 7, 10, 13, 17 and 27 days after the treatments) and the repetition of the experiment
(I and II) were used as factors. Significant p-values are shown in italics.
p-Values
Site I
Site II
Treatment
<0.001
<0.001
Date
<0.001
<0.001
Repetition
0.447
0.492
Treatment: Date
<0.001
<0.001
Treatment: repetition
0.834
0.476
Date: repetition
0.494
0.056
Treatment: date: repetition
0.914
0.019
Table 5. Multiple linear regression coefficients used to estimate the percentage weed cover per day of
interest for each treatment, repetition, and site using the linear equations. Linear regressions lines are
plotted in Figure 5.
Regression Coefficient (±SE)
Site I
Site II
Intercept
0.760 (0.049)
0.686 (0.035)
Glyphosate
0.091 (0.069)
0.064 (0.050)
Flaming
0.835 (0.069)
0.675 (0.050)
Hot foam
0.879 (0.069)
0.739 (0.050)
Nonanoic acid
0.002 (0.069)
0.055 (0.050)
Evaluation date
0.008 (0.003)
0.011 (0.002)
Repetition II
0.033 (0.069)
0.087 (0.050)
Glyphosate: evaluation date
0.014 (0.005)
0.006 (0.003)
Flaming: evaluation date
0.030 (0.005)
0.021 (0.003)
Hot foam: evaluation date
0.031 (0.005)
0.017 (0.003)
Nonanoic acid: evaluation date
0.000 (0.005)
0.002 (0.003)
Glyphosate: repetition II
0.109 (0.098)
0.091 (0.071)
Flaming: repetition II
0.040 (0.098)
0.142 (0.071)
Hot foam: repetition II
0.070 (0.098)
0.195 (0.071)
Nonanoic acid: repetition II
0.098 (0.098)
0.150 (0.071)
Evaluation date: repetition II
0.001 (0.005)
0.005 (0.003)
Glyphosate: evaluation date: repetition II
0.005 (0.007)
0.005 (0.005)
Flaming: evaluation date: repetition II
0.002 (0.007)
0.010 (0.005)
Hot foam: evaluation date: repetition II
0.002 (0.007)
0.016 (0.005)
Nonanoic acid: evaluation date: repetition II
0.005 (0.007)
0.007 (0.005)
Agronomy 2020, 10, 129 9 of 15
Figure 4. Regression lines with all the points and 95% confidence interval bands of percentage weed
cover as affected by the treatments (control, flaming, glyphosate, hot foam and nonanoic acid), the
repetition (I,II) and the evaluation date (time) in the two sites. (Site I) residual standard error = 0.123;
multiple R-squared = 0.859; adjusted R-squared = 0.846. (Site II) residual standard error = 0.089;
multiple R-squared = 0.916; adjusted R-squared = 0.909.
In both sites and repetitions, except for glyphosate at Site I, the weeds grew again. Glyphosate
at site I followed a different trend, showing a slight weed cover decrease of 15% (±7%) 27 days after
the application of the treatment in repetition I, whereas in repetition II, the weed cover did not
increase and remained statistically similar for 27 days (Figure 4).
At site I, the application of treatments showed three response trends. Glyphosate followed the
trend described above. Hot foam and flaming started with a weed cover of 0% and 1%, respectively,
and reached a similar average of 9094% (± 5%) after 27 days (i.e., regrowth). Nonanoic acid and the
control started with an average weed cover of 7381% (± 4%) and reached 98100% (± 5%) after 27
days. Flaming after 27 days was also similar to the control and nonanoic acid, whereas the hot foam
was significantly lower (Figure 4).
At site II, after hot foam and flaming, weed cover regrew from 0% (hot foam) and 711% ± 3%
(flaming). After the other two treatments, the weeds did not die and continued to grow, starting with
a weed cover percentage of 61–79% 3%). The hot foam in repetition I showed the lowest significant
weed coverage after 27 days (71% ± 4%). In repetition I, weed cover after flaming treatment reached
88% (±4%) after 27 days. This was similar to flaming in repetition II (95% ± 4%), hot foam in repetition
II (90% ± 4%), glyphosate (89% and 90% ± 4%, respectively for Replication I and II) and the control in
repetition II (95% ± 4%). However, it was different from nonanoic acid (98% and 99% ± 4% for
repetitions I and II) and the control in repetition I (99% ± 4%), respectively. The other treatments
showed similar results to each other (Figure 4).
The time (days) estimated to reach 10%, 50% and 90% weed cover regrowth, is reported in Table
6. The time to reach 10% and 50% weed cover regrowth was only biologically significant for the
flaming and hot foam because, in the control, glyphosate and nonanoic acid plot weeds did not die
and weed cover was already above 10% and 50%, respectively (Figure 4).
In both sites and repetitions, weeds re-covered 10% of the ground in a similar average time of
four days after flaming, and in a similar average time of six days after hot foam. At site I, there were
no statistical differences between flaming and hot foam in re-covering 10% of the ground after
treatment. The times estimated after flaming at site II were, instead, statistically lower than that
estimated after hot foam treatments, which reached 10% weed cover about three days later (Table 6,
Figure 4).
Agronomy 2020, 10, 129 10 of 15
Table 6. Estimated time (days) to reach 10%, 50% and 90% weed cover regrowth (ET10, ET50, and ET90,
respectively) as affected by the different treatments (control, flaming, glyphosate, hot foam, and
nonanoic acid), the repetition (I and II) and the evaluation date in the two sites. The linear regression
lines are plotted in Figure 4.
Treatment
Estimated Time (Days) (±SE) for Weed Cover Percentage Regrowth
Repetition I
Repetition II
Site I
ET
10
(±SE)
ET
50
(±SE)
ET
90
(±SE)
ET
10
(±SE)
ET
50
(±SE)
ET
90
(±SE)
Control
NA
NA
17.6 (±3.69)
NA
NA
15.8 (±4.00)
Flaming
4.7 (±0.97)
15.3 (±0.70)
26.0 (±1.32)
4.8 (±0.96)
15.3 (±0.70)
25.9 (±1.30)
Glyphosate
NA
NA
NA
NA
NA
NA
Hot foam
5.7 (±0.89)
16.0 (±0.70)
26.4 (±1.31)
6.6 (±0.83)
16.8 (0.73)
27.1 (±1.35)
Nonanoic acid
NA
NA
17.3 (±3.55)
NA
NA
16.7 (±2.28)
Site II
ET
10
(±SE)
ET
50
(±SE)
ET
90
(±SE)
ET
10
(±SE)
ET
50
(±SE)
ET
90
(±SE)
Control
NA
NA
19.2 (±2.12)
NA
NA
19.8 (±3.79)
Flaming
2.8 (±0.93)
15.3 (±0.60)
27.8 (±1.24)
3.9 (±0.75)
14.7 (±0.51)
25.6 (±0.95)
Glyphosate
NA
NA
28.0 (±7.48)
NA
NA
26.8 (±6.52)
Hot foam
5.4 (±0.89)
19.3 (±1.85)
33.7 (±1.85)
6.7 (±0.59)
16.8 (±0.52)
27.0 (±0.97)
Nonanoic acid
NA
NA
20.7 (±2.01)
NA
NA
21.2 (±1.71)
NA: not available (i.e., the estimation had no biological meaning).
A total of 50% weed cover regrowth was reached after flaming in a similar average time of 16
days in the two repetitions and in both sites. Also after the hot foam, there were no statistical
differences between repetitions and sites, and 50% weed cover was reached after an average time of
17 days. At site I, again, there were no statistical differences between flaming and hot foam in re-
covering 50% of the ground after treatment, whereas at site II, 50% weed cover after hot foam was
reached three days later than the time needed after flaming (Table 6, Figure 4).
A total of 90% weed cover regrowth (or natural growth where weeds were not dead) was
reached after all the treatments, except for glyphosate at site I. After an average of 18 days from the
start of the experiment, the control reached 90% of the ground covered by weeds in the two
repetitions and in both sites. The nonanoic acid plots reached it after an average time (average
between repetitions and sites which were similar) of 19 days. The control and nonanoic acid times
were statistically similar. A total amount of 90% weed cover was reached in an average time (average
between similar values of replicates and sites) of 26 days after flaming. After the hot foam, repetition
I of site II showed a significantly higher time (average of 34 days) to reach 90% weed cover regrowth
compared to repetition II of site II and repetitions I and II of site I, which showed a similar average
time of 27 days. At site II, the resulting high standard errors due to the high variability in the plots
after the glyphosate application averaged 27 days, which was similar to the times estimated for all
the other treatments to reach 90% weed cover. At site I, the time to reach 90% weed cover after flaming
was significantly higher compared with the control (+8 days) and nonanoic acid (+9 days), and similar
to that of hot foam. At site II, the time after flaming was similar to that of the control and hot foam in
repetition II, higher than nonanoic acid (+4 days) and lower (−8 days) than hot foam in repetition I.
At site I, after the hot foam, the significant time delay to reach 90% weed cover compared with the
control and nonanoic acid was 9 days and 1011 days, in repetition I and II, respectively. At site II,
the significant delay after hot foam in repetition I compared to the control and nonanoic acid was 14
days and 13 days, respectively. On the other hand, after the hot foam in repetition II, the time was
similar to the control and higher (+6 days) than the nonanoic acid (Table 6, Figure 4).
3.3. Weed Dry Biomass
Weed dry biomass collected 29 days after treatment application was influenced by the treatment
and the interaction between treatment and site (p-values < 0.001, respectively). The other factors and
Agronomy 2020, 10, 129 11 of 15
interactions were not significant. Least squares means and 95% confidence intervals for each
treatment, repetition and site are plotted in Figure 5.
Figure 5. Weed dry biomass bar graph and 95% confidence interval as affected by the treatments
(control, flaming, glyphosate, hot foam and nonanoic acid), repetition and evaluation date at sites I
and II, respectively.
At site I, the weed dry biomass in both repetitions of the control and nonanoic acid plots were
similar and significantly higher compared with both the repetitions of glyphosate, flaming and hot
foam, whereas the dry biomass was similar (Figure 5).
At site II, the weed dry biomass in both repetitions of the control was similar to that estimated
in both repetitions of nonanoic acid and higher compared with both repetitions of flaming,
glyphosate and hot foam. Both repetitions of hot foam were significantly lower than both repetitions
of nonanoic acid, whereas both repetitions of flaming and glyphosate were significantly lower only
than repetition I of nonanoic acid. Both repetitions of glyphosate and repetition II of flaming were
similar, whereas repetition I of flaming was lower than repetition II of nonanoic acid. Weed dry
biomass in both repetitions of glyphosate was similar to those of flaming and hot foam in repetition
I, whereas glyphosate in repetition I was significantly higher than hot foam in repetition II. Weed dry
biomass in both repetitions of flaming was similar to those of hot foam.
4. Discussion
Weed control was effective only when flaming and hot foam were applied. Hot foam was the
most effective method, leading to 100% weed control one and two days after the treatment in both
sites and replications. At site I, flaming was statistically a little less effective than hot foam, but in any
case, provided 99% of weed control. At site II, also flaming led to 100% weed control, but this effect
lasted only one day (Figures 2 and 3).
Although the effectiveness of a herbicide should increase if the droplet size is reduced (i.e., an
increase in droplet number obtained with ultra-low volume applications increases the likelihood of
impacting the weed leaf surface) [6], a dose of 1080 g a.i. glyphosate per ha1 was probably not high
enough to control C. esculentus (L.) and C. arvensis (L.), whereas this dose was effective against P.
Agronomy 2020, 10, 129 12 of 15
annua (L.). This effect of glyphosate on P. annua (L.) was visible in the photographs taken 13 days
after the treatments, which showed the delayed death of this weed species. In Figure 5, the decrease
in the total weed cover in repetition I of glyphosate was due to the death of P. annua (L.). This decrease
was not significant in repetition II (where the weed cover was similar to that three days after
treatment). This was probably because the simultaneous growth of C. esculentus (L.) and C. arvensis
(L.) minimized the reduction in the total weed population coverage due to the death of P. annua (L.).
Because only P. annua (L.) died, and the total weed population coverage was never lower that an
average of 50%, the weed control due to the use of glyphosate cannot be considered effective in this
experiment.
Nonanoic acid was not effective in controlling weeds probably because the species in these
experiments were too developed for the herbicide to have an effect. Previous research reported that
nonanoic acid needs to be applied to very young or small plants for acceptable weed control [38], and
repeated applications are suggested [10]. Rowley et al. [39] obtained a moderate reduction in weed
coverage, density, and dry biomass compared to the untreated control, but the dose of nonanoic acid
used (39 L a.i. ha1) was above that indicated on the product label. Other authors [40] found a
reduction in Microstegium vimineum (Trin.) coverage compared to the untreated control when
pelargonic acid was applied at 11.8 kg a.i. ha1, 5% volume.
The regrowth of weeds after the death of the aboveground vegetative tissues is an important
indicator to validate the effectiveness of a weed control technique. In fact, it determines how many
times a weeding method needs to be applied during a weed management program. Given that a
technique should kill the weeds after being applied, the time weeds take to regrow and cover the
ground again is an indicator of how many times the technique needs to be repeated in the annual
management of weeds. This management depends on whether the weeds grow in urban areas or
agricultural fields, with crops that may vary in sensitivity to competition from weeds.
Weed regrowth started earlier after flaming than after hot foam, in fact, at site II, just two days
after the flaming application, the weed cover was higher than one day after. Three days after flaming,
the weed cover estimated at site II was already 711% 3%), whereas in the hot foam plots, the weed
cover was still 0%. At site I, 27 days after treatments, the weed cover after hot foam was still
significantly lower than the control and nonanoic acid. However, in the flaming plots, the weed cover
was similar to hot foam, but also to the control and nonanoic acid, thus suggesting greater damage
of the hot foam to the weeds’ meristems. This was more evident in the repetition I at site II, where
the weed cover after 27 days from the hot foam application was still significantly lower than the other
treatments (Figure 4). At site II, the delay of time needed after hot foam to recover 10% and 50% of
the ground compared to flaming was also significant, and this delay was still significant in repetition
I to re-cover 90% (Table 6). P. annua (L.) did not regrow after hot foam, suggesting that the meristems
of this species were severely damaged, which flaming did not achieve.
The time needed to recover 90% of the ground was on average 26–27 days for flaming and hot
foam. The time of 34 days was estimated only for hot foam in repetition I of site II (Table 6). A time
of 2627 days was estimated to be the time after which a new weed control application was needed
for a real infested field during high weed season (i.e., May, June, July in Italy). For glyphosate and
nonanoic acid, the time needed to reach 90% weed coverage of the ground was less relevant because
in these plots there was no weed control. The dose of 1080 g glyphosate per ha1 had no effect on the
growth of C. esculentus (L.) and C. arvensis (L.), which continued their natural growth, whereas P.
annua (L.) died and was not able to regrow. In the nonanoic acid and control plots, the growth
observed naturally occurred in 27 days (i.e., weeds did not die).
Twenty-nine days after the treatment application, the weed dry biomass was similar when
flaming and hot foam were applied. This suggests that the weed cover in repetition I at site II was
lower, but was made up of larger weeds. Also the lowest weed coverage after glyphosate at site I was
made up of the largest weeds, in fact, the weed dry biomass was similar to flaming and hot foam. At
site I, in the control and nonanoic acid plots, weed dry biomass was always higher than flaming,
glyphosate and hot foam, suggesting that during their growth these weeds, in addition to expanding
laterally, had time to grow in size. At site II, the differences in weed dry biomass were less marked
Agronomy 2020, 10, 129 13 of 15
than at site I, suggesting a more homogeneous weed growth, but in any case the control had more
time to grow in size.
5. Conclusions
Weed control was effective only when flaming and hot foam were applied, providing
respectively 99% and 100% of weed control two days after the treatments. Nonanoic acid at a dose of
11 kg a.i. ha1 diluted in 5 L of water was not effective at controlling the developed plants of C.
esculentus (L.), C. arvensis (L.) and P. annua (L.). Glyphosate at a dose of 1080 g a.i. ha1 without water
dilution only controlled P. annua (L.), but had no effect on C, esculentus (L.) and C. arvensis (L.).
Flaming and hot foam controlled these three major species of the weed population effectively
together with the other weeds that were observed in the field experiments.
Weed regrowth started sooner after flaming that after hot foam. P. annua (L.) did not regrow
only after the hot foam and glyphosate application, and there was generally more damage to the
weeds’ meristems after hot foam. At site II, a significant time delay was needed after hot foam to
recover 10% and 50% of the ground compared to flaming. The time needed to recover 90% of the
ground was on average 2627 days for flaming and hot foam. This time of 2627 days was estimated
to be the time after which a new weed control application was needed after flaming and hot foam for
a real infested field during the high weed growth season (e.g., May, June, July in Italy). After 29 days
from treatment application, weeds were smaller in size when flaming, glyphosate and hot foam were
applied compared with nonanoic acid and the control. From a practical standpoint, hot foam and
flaming applications could be repeated once a month in spring and beginning of summer, and less
frequently when the weeds growth is slower. Flaming can also be used to control weeds after the
emergence/transplant of heat-tolerant crops, whereas hot foam is recommended applied in bands of
soil before high-income crop transplant and/or for controlling weeds under vineyard rows, in order
to reduce heat production costs compared to the application of the whole ground surface.
Author Contributions: conceptualization, L.M., C.F., M.S., M.F., M.R. and A.P.; methodology, L.M., C.F., M.S.;
validation, L.M., C.F., M.S., M.F., M.R. and A.P.; investigation, L.M., C.F., M.S., M.F., M.R. and A.P.; resources,
L.M., C.F., M.S., M.F., M.R. and A.P.; data collection, L.M., C.F., and M.S.; data analysis, L.M.; writingoriginal
draft preparation, L.M.; writing—review and editing, L.M.; visualization, L.M., C.F., M.S., M.F., M.R. and A.P.;
supervision, L.M., C.F., M.S., M.F., M.R. and A.P.; project administration, L.M., C.F., M.F., and A.P. All authors
have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Acknowledgments: This study was self-financed by the Department of Agriculture, Food and Environment of
the University of Pisa (Pisa, Italy). The authors would like to thank Cosmin User, Franck Balducchi and Edward
Cutler from Weedingtech Ltd. who provided the hot foam machine and technical support; Lorenzo Greci and
Romano Zurrida from the Department of Agriculture, Food and Environment of University of Pisa for their
technical support.
Conflicts of Interest: The authors declare no conflict of interest.
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© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
... • Chemical (herbicides, also known as plant protection products; PPPs) (De Cauwer et al. 2013, Rask et al. 2013, EMR 2015b, Bristol City Council 2017, Hanson et al. 2006, Kempenaar & Saft 2006, SKL 2006, Kempenaar et al. 2007, Rask & Kristoffersen 2007, Neal & Senesac 2018, APSE 2019a, APSE 2019b, APSE 2020, Martelloni et al. 2020, APSE 2021, Corbett pers comm. 2021 ...
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Innovative approaches in weed management, namely harvest weed seed control (HWSC), weed-tolerant cultivars, and foam weed control, address the challenges posed by herbicide-resistant weeds and promote sustainable weed management. Firstly, HWSC offers a promising avenue for reducing weed populations and preserving the efficacy of herbicides. Methods such as chaff carts, chaff tramlining and chaff lining, narrow windrow burning, harrington seed destructor, and bale direct systems facilitate the collection and destruction of weed seeds at harvest. It disrupts the weed life cycle by destroying weed seeds before they return to the soil. Chaff tramlining and chaff lining, and narrow windrow burning are widely practiced in Australia and the USA due to their efficiency and economic feasibility. In contrast, bale direct systems and chaff carts may gain traction in developing countries where straw serves as livestock fodder. Secondly, weed-tolerant cultivars offer natural and sustainable weed control by leveraging rapid early growth, efficient canopy development, and allelo-chemicals to inhibit germination and suppress weed growth. However, these approaches pose challenges, including environmental specificity, trade-offs with crop yield, soil fertility, genetic diversity concerns, allelopathic effects, varietal selection challenges, and long-term stability. Thirdly, foam weed control enhances herbicide adhesion, reduces drift, and improves coverage. Mixing foam with hot water ensures efficient heat transfer to targeted plant tissues without dissipation into the atmosphere. However, its efficiency depends on factors such as the choice of foaming agent, foam concentration, foam persistence, water quality, application equipment, environmental conditions, weed species, growth stage, and application rate.
... Many endeavors are underway to replace synthetic herbicides and find appropriate products, tools, or management techniques that effectively control weeds in turfgrasses and urban environments. Currently, the most effective weed removal methods in turfgrasses or urban hard surfaces involve localized applications of nonselective biological products (i.e., acetic acid) [5] or thermal treatments [6], however, adequate efficacy has yet to be achieved. Robotic machines that can autonomously detect and remove weeds show great promise for more sustainable weed control in turfgrasses [7][8][9]. ...
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The advancement of computer vision technology has allowed for the easy detection of weeds and other stressors in turfgrasses and agriculture. This study aimed to evaluate the feasibility of single shot object detectors for weed detection in lawns, which represents a difficult task. In this study, four different YOLO (You Only Look Once) object detectors version, along with all their various scales, were trained on a public ‘Weeds’ dataset with 4203 digital images of weeds growing in lawns with a total of 11,385 annotations and tested for weed detection in turfgrasses. Different weed species were considered as one class (‘Weeds’). Trained models were tested on the test subset of the ‘Weeds’ dataset and three additional test datasets. Precision (P), recall (R), and mean average precision (mAP_0.5 and mAP_0.5:0.95) were used to evaluate the different model scales. YOLOv8l obtained the overall highest performance in the ‘Weeds’ test subset resulting in a P (0.9476), mAP_0.5 (0.9795), and mAP_0.5:0.95 (0.8123), while best R was obtained from YOLOv5m (0.9663). Despite YOLOv8l high performances, the outcomes obtained on the additional test datasets have underscored the necessity for further enhancements to address the challenges impeding accurate weed detection.
... In field application efficacy of pelargonic acid varied among the field trials. Overall, it was incomplete, confirming what was observed in the greenhouse experiment and what was already reported in previous field experiments conducted on spontaneous weed flora [27,29,33]. The botanical composition of weed flora can significantly affect the efficacy of pelargonic acid, and remarkable inter-specific sensitivity differences have been largely described [22,23]. ...
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Pelargonic acid is the most successful natural herbicide and can contribute to reducing synthetic herbicides, but information on its efficacy is contrasting. Given its high cost, a reduction of the rate could facilitate the spread of the use of this herbicide. Two greenhouse and three field experiments were conducted to evaluate the herbicidal efficacy of different doses of pelargonic acid on several weeds (Abutilon theophrasti, Alopecurus myosuroides, Conyza sumatrensis, Lolium rigidum, Persicaria maculosa, Setaria pumila, Solanum nigrum). Results show that the efficacy of pelargonic acid is partial both in the greenhouse and field since the sensitivity of weed species is very variable, yet significant weed biomass reduction was observed in field application. Grass weeds, in particular A. myosuroides and L. rigidum, were less sensitive to pelargonic acid, with reduced and transient symptoms even at the highest doses. A large difference in sensitivity was also observed between dicots weeds, with P. oleracea, P. maculosa and A. theophrasti being less sensitive than C. sumatrensis and S. nigrum. The efficacy of pelargonic acid in field conditions depends on the botanical composition of weed flora and environmental conditions. Hot and dry conditions can promote leaf traits that decrease weed sensitivity by reducing herbicide penetration inside leaves. Despite its high cost, pelargonic acid can be a useful tool in an integrated multi-tactic strategy for sustainable weed management, while its use as a stand-alone tactic is less recommendable.
... Under these conditions, the presence of poles and stumps force to the use of an obstacleskipping system which reduces the effectiveness of weed removal and application speed [13][14][15]. Unlike mechanical methods, thermal weeding is characterized by higher treatment effectiveness and speed of application comparable to those of chemical weeding [16], adding to this the advantage of not increasing the risk of selection of resistant species and to be practicable in organic farming [17,18]. ...
Article
The Sustainable Development Goals constitute a series of shared targets aimed at achieving a better and more sustainable future for all. To date, urban and rural environments need to have several management practices reviewed in order to meet the above-mentioned goals. In the agricultural sector, weeds are the principal cause of crop yield reduction and an effort is required to abandon chemical herbicides, increasingly disincentivized by the European Union and agricultural regulations. This work applies research to innovative thermal methods for weed control in specialized crop (e.g. vineyards or orchards), investigating the energy dosage needed when hot-air weeding technology is used. Through a table-top experimental setup, a series of empirical equations are defined to correlate the effectiveness and working area of the hot air technology to the main governing parameters of the thermal weeding: temperature and residence time of the heat source (air). The equations highlight different ways in which it is possible to energetically optimize this technology: primary energy savings of 2.8 times can be obtained if the weeding effectiveness is reduced from 90 to 80%, while, maintaining the same effectiveness, it is possible to increase the residence time and to work at low air temperatures (150–200 °C) avoiding the risk of fire that often hinder the spread of thermal weeding practices.
... Further explanations are provided in 4.3. In any case, our results agree with those of Martelloni et al. [23] , who also suggested that hot foam should be recognized as a potential alternative to glyphosate weed control option. These authors also found that hot foam is a much more effective method of weed control than pelargonic acid, an observation that was common in all four site-experimental runs in the current study. ...
Article
Hot foam applications represent a new, smart concept in the field of thermal weed control. The aim of this study was to evaluate the efficacy of hot foam and other weed control methods in two olive groves in southern Greece (Pyrgos and Kalamata). The experiment was laid out in a randomized complete block design (RCBD) with six treatments and three replicates. Treatments were applied in the areas between trees, in the row and included mowing with a disc–flail mower, mulching with pruning residues (2.65 kg m–2), glyphosate (at 1,440 g a.e. ha–1), hot foam (13.33 L m–2), pelargonic acid (at 1,088 g a.i. ha–1; twice), and an untreated control. Two experimental runs were conducted at each site using the same treatment list. Malva parviflora L. and Sinapis arvensis L. were the predominant weeds in Pyrgos, while Urtica urens L., Galium aparine L., and Parietaria officinalis L. dominated in Kalamata. Site–experimental runs and treatments significantly affected NDVI and weed biomass (P–Value ≤ 0.001). Hot foam reduced weed biomass by up to 81, 88, 90, and 96% compared to mulching, mowing, pelargonic acid, and the untreated control, respectively. This treatment also reduced M. parviflora biomass by 75–88 and 92–93% compared to mowing and pelargonic acid, respectively, in Pyrgos and P. officinalis biomass by more than 80% in Kalamata compared to the above treatments. In all site–experimental runs, hot foam and glyphosate resulted in the lowest NDVI and weed biomass. The overall performance of hot foam was comparable to glyphosate, suggesting that this method is an environmentally friendly and effective, alternative method to control weeds in olive groves. Further research is required to optimize the use of hot foam for weed control in more perennial crops and under different soil and climatic conditions.
... However, this practice is not allowed due to a European directive and country legislation that specifically ban the use of herbicides on sports surfaces [22]. As a substitute for chemical desiccation of weeds, several methods relying on heat transfer to plants, referred to as "thermal weeding", have been subject to experimentation by various authors in numerous contexts and play an important role in organic agriculture [23][24][25][26]. Thermal weed control may be performed through several methods [27] whose effects are comparable to non-selective chemical treatments. ...
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In transition areas, cool season turfgrasses are overseeded in autumn to maintain the high quality of dormant warm season turfgrasses, while in spring several agronomic methods (scalping, coring, topdressing, verticutting, irrigation, and targeted fertilization) or chemical desiccation are adopted to remove the cool season turfgrasses from the stand. To reduce chemical applications, several methods of “thermal weeding” have been experimented with, but little is known about these methods in zoysiagrass (Zoysia spp. Willd) spring transition. A study was conducted at the University of Pisa, Italy, on Manila grass (Zoysia matrella (L.) Merr., cv “Diamond”) (Zm) overseeded with perennial ryegrass (Lolium perenne L.) (Lp) with the aim of comparing different methods of cool season grass suppression (scalping and hot foam) and different application rates of nitrogen. To assess treatment effect, green cover, turf quality, turf color, shoot density, and some vegetation indices (GLI, DGCI and NDVI) were determined. An average green cover of at least 90% was obtained on all plots seven weeks after the treatments. While scalping had minor effects on turf appearance and on polystand composition, hot foam had a stronger effect on turf color, green cover, and turf quality in the weeks following application. Once it had recovered from the hot foam treatments, the turf had a greater number of Zm shoots and a relevant reduction of Lp shoots. The hot foam was very effective in suppressing Lp while maintaining Zm recovery capacity.
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Laser weeding is one of the promising weed control methods for weed management in organic agriculture. However, the complex field environments lead to low weed detection accuracy, which makes it difficult to meet the requirements of high-precision laser weed control. To overcome this challenge and facilitate precise weeding by laser weeding robots in complex fields, this study suggests the use of a dual-mode image fusion algorithm of visible light and infrared light based on machine vision. This innovative technology, introducing infrared information based on visible light images, enhances weed detection accuracy and resilience to environmental factors. The introduction of the Swin-transformer module and Slim-neck module enables the creation of a brand new weed detection model allied with the YOLOv8 model, applicable for weed meristem detection. According to the experimental results, for fusion images with a resolution of 640*640, the dual-scale fusion of RGB and NIR images on the improved network has an average accuracy (mAP) of 96.0% and a detection accuracy of 94.0%, respectively. This study builds a laser weeding robot with a mobile platform, a weed recognition module and a laser polarization transmitter module. The ROS system is utilized to effectively detect weeds and determine their geometric center position after the weed detection model is successfully installed on the robot platform. The laser vibrator demonstrates accurate deflection to the weed growth position during the weed detection and laser illumination experiment. The results show that the accuracy of weed detection has reached 82.1%, and the efficiency of laser weeding has reached 72.3%. These results prove the feasibility of the laser weeding method proposed in this study. However, the fusion strategy of these two kinds of images still has great room for improvement in terms of detection accuracy and efficiency. In the future, multiple modal information can be used to improve the identification efficiency of weeds in the field.
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Brazil, a global frontrunner in pesticide consumption and sales, particularly glyphosate, appears to be at odds with other countries that increasingly ban these products in their territories. This study gathers the values of Acceptable Daily Intake and Maximum Residue Limits (MRL) in the European Union for dozens of substances and subsequently contrasts them with the corresponding benchmarks upheld in Brazil concerning its predominant crops. Furthermore, this study delves into the toxicity levels and the potential health ramifications of glyphosate on humans through the ingestion of food containing its residues. The findings from this research underscore a notable surge in glyphosate and pesticide sales and usage within Brazil over the past decade. In stark contrast to its European counterparts, Brazil not only sanctioned the sale and application of 474 new pesticides in 2019, but extended the authorization for glyphosate sales while downgrading its toxicity classification. Finally, this review not only uncovers disparities among research outcomes but also addresses the complexities of replacing glyphosate and introduces environmentally friendlier alternatives that have been subject to evaluation in the existing literature.
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Alternative weed control technology has developed rapidly in recent years in order to ensure sustainable agriculture. In our study, a comparison was made between the results obtained by destructing certain weeds in cotton fields using hot foam method with the results of spraying, hoeing, and control variables. Stoneville-468 cotton was cultivated in a field of approximately 2 decares. Weeds in cotton field were determined to be couch grass (Cynodon daktylon), and licorice (Glycyrrhiza glabra). As a result, licorice destruction rate was determined to be 94, 3%, 84.1% and 82.5% for hoeing, spraying, and hot foam methods, respectively. However, couch grass destruction rate was 95.1% for hoeing and foam methods, while it was 94.5% for spraying method. Furthermore, LSD test was applied and the differences between the averages of spraying and hot foaming were determined to be 0.32 and 0.272. And in terms of their effect on cotton yield, hoeing ranked the first place with 0.4 kg cotton yield per a field of 1 m 2 , and was followed by spraying method with 0.36 kg, and hot foam method with 0.35 kg; while the control method was determined to be the last with 0.09 kg yield. As a result, these close values indicate that hot foam method can be an alternative for spraying method.
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Thermal weed control technology plays an important role in managing weeds in synthetic herbicide-free systems, particularly in organic agriculture. The use of hot foam represents an evolution of the hot water weed control thermal method, modified by the addition of biodegradable foaming agents. The aim of this study was to test the weeding effect of different five hot foam doses, in two sites of different weed composition fields [i.e., Festuca arundinacea (Schreb.), Taraxacum officinale (Weber) and Plantago lanceolata (L.)], by evaluating the devitalisation of weeds, their regrowth, the weed dry biomass at the end of the experiment and the temperature of hot foam as affected by different foam doses. The results showed that the effect of the hot foam doses differed with the different infested weed species experiments. In the Festuca arundinacea (Schreb.) infested field, all doses from 3.33 L m−2 to 8.33 L m−2 led to a 100% weed cover devitalisation and a lower weed dry biomass compared to the dose of 1.67 L m−2, whereas the weed regrowth was similar when all doses were applied. In the Taraxacum officinale (Weber) and Plantago lanceolata (L.) infested fields, doses from 5.00 L m−2 to 8.33 L m−2 in site I and from 3.33 L m−2 to 8.33 L m−2 in site II led to 100% of weed cover devitalisation. The highest doses of 6.67 L m−2 and 8.33 L m−2 led to a slower weed regrowth and a lower weed dry biomass compared to the other doses. The time needed for weeds to again cover 50%, after the 100% devitalisation, was, on average, one month when all doses were applied in the Festuca arundinacea (Schreb.) infested field, whereas in the Taraxacum officinale (Weber) and Plantago lanceolata (L.) fields, this delay was estimated only when doses of 6.67 L m−2 and 8.33 L m−2 were used in site I and a dose of 8.33 L m−2 in site II. Thus, in the Festuca arundinacea (Schreb.) field experiments hot foam doses from 3.33 L m−2 to 8.33 L m−2 were effective in controlling weeds, and the use of the lowest dose (i.e., 3.33 L m−2) is recommended. However, for Taraxacum officinale (Weber) and Plantago lanceolata (L.) the highest doses are recommended (i.e., 6.67 L m−2 and 8.33 L m−2), as these led to 100% weed devitalisation, slower regrowth, and lower weed dry biomass than other doses. A delay in the regrowth of weeds by 30 days can lead to the hypothesis that the future application of hot foam as a desiccant in no-till field bands, before the transplant of high-income vegetable crops, will provide a competitive advantage against weeds.
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Suckering is the process of removing the suckers that grapevine trunks put out in the spring. Suckering by hand is costly and time consuming and requires constant bending down, getting up and making repetitive motions. The mechanical removal of suckers with rotating scourges can damage the vine plants. Chemical suckering is a limiting factor for wine grape growers interested in sustainable and/or organic agriculture. The aim of this research was to test flaming as an alternative method to vine suckering. A three-year experiment was conducted on a 10-year-old Sangiovese vine (775 Paulsen rootstock). The treatments consisted of flame suckering at different phenological stages, hand-suckering and a no-suckered control. Data on the number of suckers, grape yield components, and grape composition were collected and analysed. The results showed that flaming significantly reduced the initial number of suckers. This effect on the suckers was highest when the main productive shoots of the vines were at the 18-19 BBCH growth stage. Flame-suckering did not affect grape yield components and grape composition. Future studies could investigate the simultaneous use of flaming for both suckering and weed control.
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Intra-row weed control in organic or low-input cropping systems is more difficult than in conventional agriculture. The various mechanical and thermal devices available for intra-row weed control are reported in this review. Low-tech mechanical devices such as cultivators, finger-weeders, brush weeders, and torsionweeders tend to be used in low density crops, while spring-tine harrows are mainly applied in narrow-row high-density crops. Flame weeding can be used for both narrow and wide-row sown crops, provided that the crop is heat-tolerant. Robotic weeders are the most recent addition to agricultural engineering, and only a few are available on the market. Nowadays, robotic weeders are not yet used in small and medium sized farms. In Europe, highincome niche crops are often cultivated in small farms and farmers cannot invest in high-tech solutions. Irrespectively of the choice of low- or high-tech machines, there are several weeders that can be used to reduce the use of herbicides, making of them a judicious use, or decide to avoid them.
Book
This book presents the most up-to-date and comprehensive guide to the current and potential future state of weed science and research. Weeds have a huge effect on the world by reducing crop yield and quality, delaying or interfering with harvesting, interfering with animal feeding (including poisoning), reducing animal health and preventing water flow. They are common across the world and cost billions of dollars' worth of crop losses year on year, as well as billions of dollars in the annual expense of controlling them. An understanding of weeds is vital to their proper management and control, without which the reduction in crop yields that they would cause could lead to mass starvation across the globe. Topics covered include weed biology and ecology, control of weeds and particular issues faced in their control. Authored and edited by internationally renowned scientists in the field all of whom are actively involved in European Weed Research Society working groups, this succinct overview covers all the relevant aspects of the science of weeds. Weed Research: Expanding Horizons is the perfect resource for botanists, horticultural scientists, agronomists, weed scientists, plant protection specialists and agrochemical company personnel.
Chapter
Herbicides have made significant contributions to modern agriculture by offering exceptional weed management in crops and also facilitate no-till crop production to conserve soil and moisture. However, repeated field application of herbicides with the same mode of action has resulted in the selection of herbicide-resistant weeds. Mechanisms which confer resistance to herbicides can broadly be categorized into two types: (a) non-target site resistance (NTSR) and (b) target site resistance (TSR) (discussed in greater detail elsewhere in this book). Briefly, NTSR mechanisms include reduced herbicide uptake/translocation, and/or enhanced herbicide detoxification, decreased rates of herbicide activation, or sequestration of the herbicide (Devine and Eberlein 1997). On the other hand, TSR, essentially involves any alteration in the herbicide target site, such as mutations in target gene affecting herbicide binding kinetics (Powles and Yu 2010) or as more recently reported in glyphosate-resistant weeds, amplification of target gene (Sammons and Gaines 2014).