Effects of Various Environmental Conditions on the Growth of Amaranthus Patulus Bertol

agronomy

Article Effects of Various Environmental Conditions on the Growth of Amaranthus patulus Bertol. and Changes of Herbicide Efﬁcacy Caused by Increasing Temperatures

Hyun-Hwa Park 1, Do-Jin Lee 2 and Yong-In Kuk 1,*

1 Department of Bio-Oriental Medicine Resources, Sunchon National University, Suncheon 57922, Korea; [email protected] 2 Department of Agricultural Education, Sunchon National University, Suncheon 57922, Korea; [email protected] * Correspondence: [email protected]

Abstract: Understanding the effects of climate change on weed growth and herbicide activity is important for optimizing herbicide applications for effective weed control in the future. Therefore, this study examined how climate change affects the growth of Amaranthus patulus and the efficacy of soil and foliar herbicides at different temperatures. Although the control values for A. patulus differed between herbicides and temperature, the control values increased with increasing time after the herbicide treatments. Under growth conditions in which the temperature remained constant, the efficacy of soil-applied herbicides, ethalfluralin, metolachlor, linuron, and alachlor, on A. patulus was highest when the weeds were grown at high temperature. In particular, 100% control values of A. patulus were achieved in response to metolachlor treatments at the total recommended dosage in growth chambers at 35 ◦C. The efficacy of foliar herbicides, glufosinate-ammonium, bentazone, Citation: Park, H.-H.; Lee, D.-J.; Kuk, and mecoprop, on A. patulus was also highest when the plant was grown at high temperature, Y.-I. Effects of Various Environmental except for glyphosate isopropylamine, which had similar efficacy rates regardless of the temperature. Conditions on the Growth of A. patulus was 100% controlled in response to glufosinate-ammonium, bentazone, and mecoprop Amaranthus patulus Bertol. and at the recommended dosages in growth chambers at 30 and 35 ◦C. Under growth conditions in Changes of Herbicide Efficacy Caused by Increasing Temperatures. which the temperature changed from day to night, the efficacy of soil-applied herbicides, alachlor Agronomy 2021, 11, 1773. https:// and linuron, on A. patulus was highest when the weeds were grown at high temperature. On the doi.org/10.3390/agronomy11091773 other hand, the efficacy of the soil-applied herbicides metolachlor and linuron on A. patulus was similar regardless of the temperature. The efficacy of foliar herbicides, glyphosate isopropylamine, Academic Editor: David Clements glufosinate-ammonium, bentazone, and mecoprop, on A. patulus was highest when the weeds were grown at high temperature. Although herbicide efficacy varied depending on whether the weeds Received: 19 August 2021 were grown at constant or alternating temperatures, herbicide efficacy was generally highest when Accepted: 2 September 2021 the temperature was high. Published: 3 September 2021 Keywords: Amaranthus patulus; climate change; herbicide; temperature; weed Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Among the many consequences of climate change, rising temperatures [1] and altered precipitation patterns are having the most significant impact on agriculture because of their ability to increase the probability of summer droughts [2–4]. In addition to these direct Copyright: © 2021 by the authors. consequences of climate change, indirect consequences are expected to affect sustainability Licensee MDPI, Basel, Switzerland. and food security [5]. In many ways, weather extremes associated with climate change are This article is an open access article distributed under the terms and a very serious concern for crop management. conditions of the Creative Commons The impact of climate change on weedy vegetation may be manifested in the form of Attribution (CC BY) license (https:// geographic range expansion (migration or introduction to new areas), alterations in the creativecommons.org/licenses/by/ species life cycles, and population dynamics [6]. Increasing CO2, temperature, and water or 4.0/). nutrient availability may allow new weeds to become more problematic or existing weeds

Agronomy 2021, 11, 1773. https://doi.org/10.3390/agronomy11091773 https://www.mdpi.com/journal/agronomy Agronomy 2021, 11, 1773 2 of 16

to expand their geographical locations [7]. Weeds respond quickly to resource changes and are more likely to adapt and flourish in various habitats owing to their greater genetic diversity and physiological plasticity than crops [8]. Increasing atmospheric temperatures could promote the growth of some weeds in warm-season crops cultures. A 3 ◦C rise in the average temperature enhanced biomass and leaf area of itch grass (Rottboelliia cochinchinensis) by 88% and 68%, respectively [9]. An increase in temperature due to global warming might trigger weed migration. Milder and wetter winters would tend to increase the survival of winter annual weeds. In contrast, thermophile summer annuals will grow more profusely in areas with warmer summers under prolonged growing seasons, enabling them to grow further north [10,11]. Herbicides have become the major tools for weed management because of their simplicity in use, great efficacy, and, more importantly, reduced control costs by saving labor and time [12]. The successful use of herbicides depends on environmental conditions before, during, and after herbicide application. The environment influences the growth and physiology of plants, as well as herbicide activity and the interaction between plant and herbicide. Therefore, understanding how environmental conditions affect herbicide performance is important for realizing the impact of climate change on herbicide efficacy. Environmental factors, such as light, CO2, temperature, soil moisture, relative humidity, rainfall, and wind can affect herbicide efficacy directly by altering the penetration and translocation of herbicides within the plant or indirectly by changing the growth and physiological characteristics of the plant. While foliar herbicides are influenced by many environmental factors, soil-applied herbicides are influenced mainly by soil moisture and temperature [8]. Temperature can affect herbicide performance directly through its effects on the rate of herbicide diffusion, viscosity of cuticle waxes, and physicochemical properties of spray solutions [13]. New and effective herbicides may be needed if new weeds are introduced into a non- native area. A. patulus is a troublesome exotic weed of upland crops. Understanding the effects of climate change on weed growth and herbicide activity is important for optimizing herbicide applications for effective weed control in the future [8]. Temperature has both direct and indirect effects on herbicide efficacy. However, the underlying mechanisms responsible for varying rates of herbicide efficacy at different temperatures is poorly understood and needs investigation for a better management of weeds. Therefore, this study examined how climate change and different temperature conditions affect the growth of Amaranthus patulus and the efficacy of soil and foliar herbicides.

2. Materials and Methods 2.1. Plant Materials Seeds of A. patulus were collected from a ﬁeld used for corn production at one of Sunchon National University’s research farms in South Korea in the fall of 2020. The seeds were refrigerated at 4 ◦C until use.

2.2. Environmental Conditions for Growth of A. patulus Fifteen seeds of A. patulus were planted in small trays (18 × 13 × 9.5 cm3) with a commercial potting mixture (Sunghwa CO. Bosung, Chonnam, South Korea). The trays were placed in growth chambers (Multi-room Incubator, VS-1203PFC-LN, Vision Bionex, Buchon, South Korea) at different temperatures (15, 20, 25, and 30 ◦C). For the CO2 study, CO2 chambers (HB-303DH-0, Hanbaek Scientific Co. Buchon, Gyeonggido, South Korea) were set to 400 or 700 ppm, and a temperature of 25 ◦C was maintained throughout the experiment. Other growth chamber conditions were 60% relative humidity, 14/10 day/night photoperiod, and 100 µmol m−2 s−1 light intensity. For seeding depths and shading degree experiments, the experiment was conducted outdoors with windbreaks. The seeds were planted at depths of 0, 0.5, 1, 2, 3, 5, and 7 cm in loam-filled small trays (18 × 13 × 9.5 cm3). Seeds that had been planted at a depth of 0.5 cm in loam-filled small trays (18 × 13 × 9.5 cm3) were used for the shading degree experiments. Agronomy 2021, 11, 1773 3 of 16

After seeding, a light-shielding polyethylene ﬁlm (Morpho Inc., Dasan, Gyeongnam, South Korea) was installed to reduce natural light exposure by 20, 35, 50, 75, and 90%. The control was exposed to full natural light. During the experiment, the temperature was 28 ± 2 ◦C/18 ± 2 ◦C at day/night. There was no rainfall, and proper soil moisture was maintained. The germination rates were measured 3, 4, 5, 6, 9, 10, 11, 12, 16, and 17 days after seeding, whereas plant height, leaf area, and shoot fresh weight were measured 17 days after seeding. Leaf area was measured by an LI-3100 area meter (LI-COR, Inc., Lincoln, NE, USA).

2.3. Herbicide Efficacy in A. patulus Grown in a Growth Chamber at Different Temperatures Five seeds of A. patulus were planted at a depth of 1 cm in a loam-filled plastic cup (150 mL) and placed in a growth chamber at 25 ◦C (Multi-room Incubator, VS-1203PFC-LN, Vision Bionex, Buchon, South Korea). The other growth chamber conditions were 70% relative humidity, 14/10 h of photoperiod (day/night), 100 µmol m−2 s−1 light intensity. Soil-applied herbicides, i.e., ethalfluralin, metolachlor, linuron, and alachlor, were applied three days after sowing. The herbicides were applied using a hand sprayer, as shown in Table1. The treated plots were placed in the growth chamber at 25, 30, and 35 ◦C. The other growth chamber conditions were the same as above. Them 1, 5,10, and 15 days after treatment, injury ratings were determined, based on a composite visual estimation of growth inhibition, bleaching, and necrosis using a scale ranging from 0 (no effect) to 100 (completely dead). For visual estimation, the herbicides were applied at their respective recommended dosage.

Table 1. Active ingredients used in this study.

Application Dosage Spray Volume Herbicide/Active Ingredient Mode of Action Formulation Method (g ai/ha) (L/ha) Ethalﬂuralin 35.0% SRGI EC Soil (3 DAWS) 525, 1050 1000 Metolachlor 40.0% SSGI EC Soil (3 DAWS) 600, 1200 1000 Linuron 50.0% PI WP Soil (3 DAWS) 375, 750 150 Alachlor 43.7% SSGI EC Soil (3 DAWS) 435, 870 1000 Glyphosate isopropylamine 41.0% AASI L Foliar (14 DAWS) 615, 1230 800 Bentazone 40.0% PI L Foliar (14 DAWS) 600, 1200 1000 Mecoprop 50.0% AI L Foliar (14 DAWS) 1250, 2500 1500 Glufosinate ammonium 18.0% NM L Foliar (14 DAWS) 270, 540 1000 SRGI: seedling root growth inhibitor; SSGI: seedling shoot growth inhibitor; PI: photosynthesis inhibitor; AASI: amino acid synthesis inhibitor; AH: auxin inhibitor; NM: nitrogen metabolism; EC: Emulsiﬁable concentrates; WP: Wettable powder; L: Liquid; DAS: Days after weed seeding.

The shoot fresh weight was also measured 15 days after treatment. The control values were calculated by the shoot fresh weight compared to the untreated control. For control values, the herbicides were applied at half and full recommended dosages. In cases where the foliar herbicides bentazone, glufosinate-ammonium, glyphosate- isopropylamine, and mecoprop were applied, ﬁve seeds of A. patulus were planted at a depth of 1 cm in a loam-ﬁlled plastic cup (150 mL and placed in a growth chamber at 25 ◦C (Multi-room Incubator, VS-1203PFC-LN, Vision Bionex, Buchon, South Korea). Then, 14 days after sowing (3–4 leaf stage), the foliar herbicides were applied, and the plots were placed in the growth chamber at 25, 30, and 35 ◦C. The other procedures were the same as those mentioned in the soil application experiment.

2.4. Herbicide Efficacy in A. patulus under Greenhouse Conditions at Different Temperatures Fifteen seeds of A. patulus were planted in loam-filled small trays (18 × 13 × 9.5 cm3) and placed under greenhouse conditions at a daily average temperature of 24 ◦C. The greenhouse was kept, on average, at 60% relative humidity, with a photoperiod of 14/10 h (day/night) and a light intensity of 500 µmol m−2 s−1. Three days after seeding, soil- applied herbicides, i.e., ethalfluralin, metolachlor, linuron, and alachlor, were applied. The Agronomy 2021, 11, 1773 4 of 17

14 days after sowing (3–4 leaf stage), the foliar herbicides were applied, and the plots were placed in the growth chamber at 25, 30, and 35 °C. The other procedures were the same as those mentioned in the soil application experiment.

2.4. Herbicide Efficacy in A. patulus under Greenhouse Conditions at Different Temperatures Fifteen seeds of A. patulus were planted in loam-filled small trays (18 × 13 × 9.5 cm) and placed under greenhouse conditions at a daily average temperature of 24 °C. The greenhouse was kept, on average, at 60% relative humidity, with a photoperiod of 14/10 h (day/night) and a light intensity of 500 μmol m−2 s−1. Three days after seeding, soil-ap- Agronomy 2021, 11, 1773 plied herbicides, i.e., ethalfluralin, metolachlor, linuron, and alachlor, were applied.4 of The 16 herbicides were applied using a hand sprayer, as shown Table 1. The average temperature of each greenhouse during the experimental period (14 days) was 24, 26, and 28 °C (Figure 1). The average temperature and relative humidity during the experimental period were herbicides were applied using a hand sprayer, as shown Table1. The average temperature calculated using a data logger (SK-L200TH, SATO, Tokyo, Japan). Then, 1, 5,10, and 15 of each greenhouse during the experimental period (14 days) was 24, 26, and 28 ◦C days after treatment, the injury ratings were determined, based on a composite visual es- (Figure1) . The average temperature and relative humidity during the experimental period timation of growth inhibition, bleaching, and necrosis using a scale of 0 (no effect) to 100 were calculated using a data logger (SK-L200TH, SATO, Tokyo, Japan). Then, 1, 5,10, and 15(complete days after death). treatment, The shoo the injuryt fresh ratingsweight werewas measured determined, 15 days based after on atreatment. composite The visual con- estimationtrol values of were growth calculated inhibition, based bleaching, on the shoot and fresh necrosis weight using of aplants scale ofused 0 (no as effect)untreated to 100control. (complete death). The shoot fresh weight was measured 15 days after treatment. The control values were calculated based on the shoot fresh weight of plants used as untreated control.

◦ ◦ ◦ Figure 1. 1.Daily Daily average average temperature temperature (A, 24 (A,C; 24 B, 26°C; C;B, C,26 28 °C;C) C, on 28 days °C) afteron days herbicide after treatments herbicide in treatments the greenhouse. in the greenhouse. In tests using the foliar herbicides bentazone, glufosinate-ammonium, glyphosate isopropylamine, and mecoprop, 15 seeds of A. patulus were planted in loam-ﬁlled small In tests using the foliar herbicides bentazone, glufosinate-ammonium, glyphosate trays (18 × 13 × 9.5 cm3). Table1 presents herbicide components. The trays were placed isopropylamine, and mecoprop, 15 seeds of A. patulus were planted in loam-filled small in a greenhouse at an average temperature of 25 ◦C before the applications. Seven days trays (18 × 13 × 9.5 cm). Table 1 presents herbicide components. The trays were placed in after seeding, six plants per tray were maintained. Foliar herbicides were applied 14 days a greenhouse at an average temperature of 25 °C before the applications. Seven days after after seeding (3–4 leaf stage), and the treated plants were placed in greenhouses at average temperatures of 24, 26, and 28 ◦C during the treatment period. Other procedures were the same as those mentioned above.

2.5. Statistical Analysis All experiments were carried out with three replicates. The data were analyzed using the analysis of variance (ANOVA) procedure in the Statistical Analysis Systems software. The means were separated using a Duncan’s multiple range test (p = 0.05).

3. Results and Discussion 3.1. Environmental Conditions for Growth of A. patulus The highest germination rates of A. patulus (62–91%) were observed when seeds were planted at depths of 0, 0.5, and 1 cm (Table2). At depths of 2, 3, 5, and 7 cm, the germination Agronomy 2021, 11, 1773 5 of 16

rates were lower (14–43%). The plant height and leaf area were significantly higher when the seeds were planted at 0.5, 1, 2, and 3 cm than at 0, 5, and 7 cm. When the seeds were planted at depths of 0, 0.5, 1, 2, and 3 cm, the resulting plants had significantly more leaves than the plants from seeds planted at depths of 5 and 7 cm. The shoot fresh weight was highest when the seeds were planted at depths of 2 cm. In addition, the shoot fresh weight of the plants planted at depths of 0.5, 1, and 2 cm was significantly higher than that of plants planted at 0, 5, and 7 cm. Most weeds germinated well and fast in shallow soil [14–16].

Table 2. Germination rate and growth of A. patulus 10 days after seeding, grown from seeds planted at different depths in ﬁeld conditions.

Seeding Depth Germination Rate Plant Height Leaf Number Leaf Area Shoot Fresh Weight (cm) (%) (cm) (No./Plant) (mm2) (mg/plant) 0.0 71.4 ab 1.47 b 5.67 a 0.81 b 80 c 0.5 90.5 a 5.47 a 8.00 a 11.19 a 560 b 1.0 61.9 bc 4.40 a 7.67 a 15.01 a 490 b 2.0 42.9 cd 4.03 a 7.00 a 11.41 a 530 b 3.0 19.0 de 4.87 a 8.00 a 15.27 a 780 a 5.0 19.0 de 0.97 b 3.00 b 0.22 b 30 c 7.0 14.3 e 0.63 b 2.67 b 3.68 b 20 c Means within a column followed by the same superscripts are not signiﬁcantly different at the 5% level according to Duncan’s Multiple Range Test.

Compared to the control without shade, A. patulus seeds germinated at a higher rate under 20% shade (Table3). The germination rates were reduced by increasing the shade level. This result means A. patulus seeds are capable of germinating under a variety of light conditions. Furthermore, plant height, leaf number, and shoot fresh weight of plants grown under 0, 20, and 35% shade were signiﬁcantly greater than those of plants grown under 50, 75, and 90% shade. On the other hand, the leaf area was similar, regardless of the shade conditions.

Table 3. Germination rate and growth of A. patulus 10 days after seeding, grown from seeds planted at different shading degrees in ﬁeld conditions.

Shade Germination Rate Plant Height Leaf Number Leaf Area Shoot Fresh Weight (%) (%) (cm) (No./plant) (mm2) (mg/Plant) 0 66.7 b 3.80 bc 7.33 a 7.08 ab 340 a 20 95.2 a 4.80 ab 7.67 a 9.80 a 380 a 35 42.9 c 6.20 a 6.67 a 7.07 ab 460 a 50 33.3 c 2.65 cd 4.33 b 1.63 b 60 b 75 19.0 d 0.93 de 2.67 b 0.02 b 0 b 90 4.8 e 0.00 e 0.00 c 0.00 b 0 b Means within a column followed by the same superscripts are not signiﬁcantly different at the 5% level according to Duncan’s Multiple Range Test.

Shade affected stem elongation. Generally, the plant height increased with an increasing amount of shade provided. In this study, the plant height increased with increasing shade levels from 0 to 35% but decreased at higher shade levels of 50—90%. On the other hand, in another study, the plant height of Adenophora triphylla var. japonica increased with increasing shade levels [17]. Furthermore, the plant height of Sicyos angulatus under 60% shade conditions was three times higher than under non-shade conditions [18]. The ideal temperatures for germination of A. patulus were between 25 ◦C and 30 ◦C (Figure2). This temperature range produced the highest levels of germination (77–80%). Furthermore, plant height, shoot fresh weight, leaf number, and leaf area were higher at 25 ◦C and 30 ◦C than at 15 and 20 ◦C (Figure3). In lower temperature conditions at 15 ◦C, A. patulus seeds had germination rates of 23%. This result means that A. patulus seeds Agronomy 2021, 11, 1773 6 of 16

have viability potential under bad environmental conditions. In different CO2 conditions, germination of A. patulus was not significantly different in CO2 chambers between 400 and 800 ppm (Figure4). Plant height and leaf area were also not significantly different in 400 and 700 ppm CO2 chambers (Figure5). However, shoot fresh weight and leaf number were higher at 400 ppm CO2 than 800 ppm. In brief, C3 plants physiologically benefited from rising the CO2 levels more than C4 plants such as A. patulus [7]. In another study, spurred anoda (Anoda cristata) and velvetleaf (Abutilon theophrasti) produced more dry matter at 32/23 ◦C day/night temperature than at 26/17 ◦C day/night temperature, indicating that a higher temperature was more favorable for their growth [19]. In a study of the effects of temperature on the growth and competitiveness of soybean (Glycine max), smooth pigweed (A. hybridus), and common cocklebur (Xanthium strumar- ium), each 3 ◦C increment in day/night temperature from 26/17 to 32/23 ◦C increased growth [20]. Guo and Al-Khatib [21] reported that the seedling growth rates of redroot pigweed (A. retroflexus), palmer amaranth (A. palmeri), and common water hemp (A. rudis) increased at high temperatures, suggesting that the amount of time for POST herbicide applications to be most effective (when the seedlings are younger) decreases at high temperatures. Lee [22] suggested that increased temperature had a more significant effect on plant phenological development than elevated CO2. Increasing the temperature by 4 ◦C advanced the emergence time of Chenopodium album and Setaria viridis by 26 and 35 days, respectively, and the corresponding flowering time by 50 and 31.5 days. Increased temperatures strongly affected biomass accumulation by annual grass species during their reproductive phase compared to the vegetative phase. Such effects were more pronounced in C3 than C4 plant species. In addition to these effects, temperature also affects the rate of water absorption and movement, which affects the rate of leaf development, cuticle Agronomy 2021, 11, 1773 7 of 17 thickness, and stomatal number and their aperture, thereby indirectly affecting herbicide selectivity and efficacy [23–25].

100 15∩ 20∩ 80 25∩ 30∩ a a a a a a a a a 60 a a a b a 40 a a b b a b b c b 20 b c b b Germination rate (%) rate Germination c c 0 c b d b b b c b b b b 0 3 4 5 6 9 10 11 12 16 17 Days after seeding (DAS)

FigureFigure 2. 2.Germination Germination rate rate (%) (%) of ofA. A. patulus patulusgrown grown at at different different temperatures temperatures in in growth growth chambers. chambers. Means Means within within a a ﬁgure figure followedfollowed by by the the same same letters letters are are not not signiﬁcantly significantly different different at at the the 5% 5% level level according according to to Duncan’s Duncan’s Multiple Multiple Range Range Test. Test.

4 0.35 a a a 0.30 ) 3 2 0.25 0.20 2 b 0.15 ab b 1 0.10 Leaf Leaf area (mm Plant (cm) height 0.05 b b 0 0.00 a a 25 b 3 b 20 c 2 15 b 10 (mg/plant) b 1 5

Shoot fresh Shoot weight c

Leafnumber (no./plant) 0 0 15 20 25 30 15 20 25 30 Temperature (∩ ) Figure 3. Plant height, leaf number, leaf area, and shoot fresh weight of A. patulus grown at different temperatures in growth chambers. The parameters were measured 17 days after seeding. Means within bars followed by the same letters are not significantly different at the 5% level according to Duncan’s Multiple Range Test.

Agronomy 2021, 11, 1773 7 of 17

Figure 2. GerminationAgronomy rate2021 (%, )11 of, 1773 A. patulus grown at different temperatures in growth chambers. Means within a figure 7 of 16 followed by the same letters are not significantly different at the 5% level according to Duncan’s Multiple Range Test.

4 0.35 a a a 0.30 ) 3 2 0.25 0.20 2 b 0.15 ab b 1 0.10 Leaf Leaf area (mm Plant (cm) height 0.05 b b 0 0.00 a a 25 b 3 b 20 c 2 15 b 10 (mg/plant) b 1 5

Shoot fresh Shoot weight c

Leafnumber (no./plant) 0 0 15 20 25 30 15 20 25 30 Temperature (∩ )

FigureFigure 3. Plant 3. height, Plant leafheight, number, leaf leaf number, area, and leaf shoot area, fresh and weight shoot of A.fresh patulus weightgrown of at A. different patulus temperatures grown at different in growth Agronomychambers.temperatures 2021, 11 The, 1773 parameters in growth were measured chamber 17s. days The after parameters seeding. Means were withinmeasured bars followed 17 days by after the same seeding. letters Means are not8 of 17 signiﬁcantlywithin different bars foll atowed the 5% by level the according same letters to Duncan’s are not Multiple significantly Range Test. different at the 5% level according to Duncan’s Multiple Range Test.

FigureFigure 4. 4.Germination Germination rate rate (%) (%) of ofA. A. patulus patulusgrown grown under under 400 400 or or 700 700 ppm ppm CO CO22 inin growthgrowth chambers.chambers. Means within a a figure ﬁgure followedfollowed by by the the same same letters letters are are not not signiﬁcantly significantly different different at at the the 5% 5% level level according according to to Duncan’s Duncan’s Multiple Multiple RangeRange Test.Test.

4 0.35 a a a 0.30 ) 3 2 0.25 0.20 2 b 0.15 ab b 1 0.10 Leaf Leaf area (mm Plant (cm) height 0.05 b b 0 0.00 a a 25 b 3 b 20 c 2 15 b 10 (mg/plant) b 1 5

Shoot fresh Shoot weight c

Leafnumber (no./plant) 0 0 15 20 25 30 15 20 25 30 Temperature (∩ ) Figure 5. Plant height, leaf number, leaf area, and shoot fresh weight of A. patulus grown under 400 or 700 ppm CO2 in growth chambers. The parameters were measured 17 days after seeding. Means within bars followed by the same letters are not significantly different at the 5% level according to Duncan’s Multiple Range Test.

Agronomy 2021, 11, x FOR PEER REVIEW 8 of 17

2 FigureAgronomy 4. Germination2021, 11, 1773 rate (%) of A. patulus grown under 400 or 700 ppm CO in growth chambers. Means within8 of 16a figure followed by the same letters are not significantly different at the 5% level according to Duncan’s Multiple Range Test.

5 10 a a )

4 a 2 8

3 a 6

2 4 Leaf area (mm

Plant height (cm) 1 2

0 0 a a 6 200 b 150 b 4 100 2 (mg/plant) 50 Shoot fresh weight

Leaf number (no./plant) 0 0 CO 400 ppm CO2 700 ppm CO2 400 ppm CO 700 ppm 2 2

Figure 5. PlantFigure height, 5. Plantleaf height,number, leaf leaf number, area, leaf and area, shoot and shootfresh fresh weight weight of of A.A. patulus patulus grown grown under under 400 or400 700 or ppm 700 CO ppm2 in CO2 in growth chambers. The parametersgrowth chambers. were The meas parametersured 17 were days measured after seeding. 17 days afterMeans seeding. within Means bars within followed bars followedby the same by the letters same letters are not significantly different at the are5% not level signiﬁcantly according different to Duncan’s at the 5% Multiple level according Range to Duncan’sTest. Multiple Range Test.

3.2. Herbicide Efﬁcacy in A. patulus Grown in a Growth Chamber at Different Temperatures

The efficacy of an herbicide on weeds depends largely on its interaction with the atmosphere, soil, and the soil–atmosphere interface [8]. Several environmental factors, such as temperature, moisture, relative humidity, and solar radiation, influence a plant’s physiologic status and susceptibility to herbicides. Among these factors, temperature can have significant effects on plant growth and herbicide performance. Therefore, understanding the effects of climate change on weed growth and herbicide activity is essential for optimizing herbicide applications for effective weed control in the future [8]. For all soil-applied herbicides tested, the efficacy in A. patulus increased with time (Figure6). After ethalfluralin, metolachlor, linuron, and alachlor treatments, A. patulus was kept in the growth chambers at 25, 30, and 35 ◦C, where weeds showed increasing damage rates. Herbicide efficacy was checked 1, 5, 10, and 15 days after treatment. The alachlor and ethalfluralin efficacy rates in A. patulus were low and did not vary regardless of the temperature. On the other hand, the metolachlor and linuron efficacy rates in A. patulus were high, particularly 15 days after treatment and when the weeds were in growth chambers at 35 ◦C. Agronomy 2021, 11, 1773 9 of 17

3.2. Herbicide Efficacy in A. patulus Grown in a Growth Chamber at Different Temperatures The efficacy of an herbicide on weeds depends largely on its interaction with the atmosphere, soil, and the soil–atmosphere interface [8]. Several environmental factors, such as temperature, moisture, relative humidity, and solar radiation, influence a plant’s physiologic status and susceptibility to herbicides. Among these factors, temperature can have significant effects on plant growth and herbicide performance. Therefore, understanding the effects of climate change on weed growth and herbicide activity is essential for optimizing herbicide applications for effective weed control in the future [8]. For all soil-applied herbicides tested, the efficacy in A. patulus increased with time (Figure 6). After ethalfluralin, metolachlor, linuron, and alachlor treatments, A. patulus was kept in the growth chambers at 25, 30, and 35 °C, where weeds showed increasing damage rates. Herbicide efficacy was checked 1, 5, 10, and 15 days after treatment. The alachlor and ethalfluralin efficacy rates in A. patulus were low and did not vary regardless of the temperature. On the other hand, the metolachlor and linuron efficacy rates in A. patulus were high, particularly 15 days after treatment and when the weeds were in Agronomy 2021, 11, 1773 9 of 16 growth chambers at 35 °C.

120 A B 100

0 120 C D 25℃ 30℃ 100 35℃

Visual rate (0-100; 100, complete death) complete (0-100; 100, rate Visual 40

1 5 10 15 1 5 10 15 Days after treatment FigureFigure 6. Visual 6. Visual rate rate (0– (0–100,100, 100, 100, complete complete death) death) of of A.A. patulus patulus in response response to to soil-applied soil-applied herbicides herbicides (A (A. alachlor;. alachlor;B .B meto-. metolachlor;lachlor; C C. ethalﬂuralin;. ethalfluralin;D D. linuron). linuron) at at each each recommendation recommendation rate rate under under different different temperatures temperatures of of growth growth chamber. chamber.

TheThe control control values values were were low low when when alachlor alachlor treatments treatments at 50% at 50% and and100% 100% of the of therec- rec- ommendedommended dosage dosage were were applied applied to A. to patulusA. patulus (Figure(Figure 7). 7Conversely,). Conversely, despite despite having having low low overaoverallll control control values, values, the theexperiments experiments with with the thehighest highest control control values values were were those those where where A. patulusA. patulus waswas kept kept in a in growth a growth chamber chamber at 30 at °C 30. ◦WhenC. When metolachlor metolachlor was was applied applied at half at half the therecommended recommended dosage, dosage, the thecontrol control values values declined declined as growth as growth chamber chamber temperatures temperatures increased. On the other hand, the control values increased with increasing temperature in the growth chambers when metolachlor was applied at its full recommended dosage. The 100% control values of A. patulus were achieved in response to metolachlor treatments at the full recommended dosage in growth chambers at 35 ◦C. The application of ethalfluralin to weeds in growth chambers at the temperature of 35 ◦C also produced the highest control values. At half the recommended dosage, the ethalfluralin control values increased significantly with increasing temperature in the growth chambers. Similarly, the control values after linuron applications at the half and full recommended dosages increased significantly with increasing growth chamber temperature. Agronomy 2021, 11, 1773 10 of 17

increased. On the other hand, the control values increased with increasing temperature in the growth chambers when metolachlor was applied at its full recommended dosage. The 100% control values of A. patulus were achieved in response to metolachlor treatments at the full recommended dosage in growth chambers at 35 °C. The application of ethalfluralin to weeds in growth chambers at the temperature of 35 °C also produced the highest control values. At half the recommended dosage, the ethalfluralin control values increased significantly with increasing temperature in the growth chambers. Similarly, the

Agronomy 2021, 11, 1773 control values after linuron applications at the half and full recommended dosages10 of 16in- creased significantly with increasing growth chamber temperature.

100 A B a

80 b c

60 d a a e f 40 b

c c 20

d 0 C D 100 HOR RR

80 a Control value (%)

a b 60

b b c c d 40 c

20 f d 0 25 30 35 25 30 35 Temperature (℃)

FigureFigure 7. 7.Control Control value value (%) (%) of ofA. A. patulus patulusin in response response to to soil-applied soil-applied herbicides herbicides ( A(A.. alachlor; alachlor;B B.. metolachlor; metolachlor;C C.. ethalfluralin; ethalfluralin; D. linuron) at different growth chamber temperatures. HOR: Half of the recommended rate; RR: Recommended rate. D. linuron) at different growth chamber temperatures. HOR: Half of the recommended rate; RR: Recommended rate. Means Means within bars followed by the same letters are not significantly different at the 5% level according to Duncan’s Mul- within bars followed by the same letters are not significantly different at the 5% level according to Duncan’s Multiple Range tiple Range Test. Error bars represent SE. Test. Error bars represent SE. As in the case of soil-applied herbicides, foliar herbicides, such as bentazone, As in the case of soil-applied herbicides, foliar herbicides, such as bentazone, glufosinate- glufosinate-ammonium, glyphosate isopropylamine, and mecoprop, also had visual dam- ammonium, glyphosate isopropylamine, and mecoprop, also had visual damage ratings thatage increasedratings that with increased time when with they time were when applied they were to A. applied patulus togrown A. patulus in growth grown chambers in growth atchambers temperatures at temperatures of 25, 30, and of 3525,◦ 30,C (Figure and 358 ).°C The (Figure glyphosate 8). The isopropylamineglyphosate isopropylamine efficacy in controllingefficacy in A.controlling patulus, basedA. patulus on visual, based rating, on visual was rating, low and was did low not and vary did regardless not vary regard- of the temperature.less of the temperature. The efficacy The of glufosinate-ammoniumefficacy of glufosinate-ammonium and bentazone and generallybentazone increased generally withincreased increasing with temperature. increasing temperature. On the other On hand, the the other visual hand, ratings, the visual while ratings, high in bothwhile cases, high werein both similar cases, when were the similar herbicides when the were herbicides applied towere weeds applied growing to weeds in growth growing chambers in growth at 30 and 35 ◦C, 10 and 15 days after treatment. The efficacy of mecoprop was highest when it was applied to weeds grown in 35 ◦C growth chambers, 10 and 15 days after treatment.

Agronomy 2021, 11, 1773 11 of 17

chambers at 30 and 35 °C, 10 and 15 days after treatment. The efficacy of mecoprop was Agronomy 2021, 11, 1773 highest when it was applied to weeds grown in 35 °C growth chambers, 10 and 1115 of days 16 after treatment.

120 A B 100

0 120 C D 25℃ 30℃ 100 35℃

60 Visual rate--100; 100, comple 100,comple rate--100; death) Visual

1 5 10 15 1 5 10 15

Days after treatment FigureFigure 8. 8Visual. Visual rate rate (0–100, (0–100 100,, 100, complete complete death) death) of A. of patulus A. patulusin response in response to foliar to foliar herbicides herbicides (A. glyphosate (A. glyphosate isopropylamine; isopropyla- B.mine; glufosinate-ammonium; B. glufosinate-ammonium;C. bentazone; C. bentazone;D. mecoprop) D. mecoprop) at each at recommendation each recommendation rate under rate differentunder different temperatures temperatures in a in a growth chamber. growth chamber.

WhenWhen the the control control values values of of foliar foliar herbicides herbicides were were measured, measured, the the glyphosate glyphosate isopropy- isoprop- lamineylamine treatments treatments were were the leastthe least effective effective at controlling at controllingA. patulus A. patulus(Figure (Figure9). Furthermore, 9). Further- themore, control the valuescontrol of values the glyphosate of the glyphosate isopropylamine isopropylamine treatments treatments did not differ did not regardless differ re- ofgardless the temperature of the temperature conditions. conditions. The control The values control of A. patulusvalues ofin responseA. patulus to in glufosinate- response to ammonium,glufosinate bentazone,-ammonium, and bentazone, mecoprop and at the mecoprop recommended at the recommende dosages (andd to dosages bentazone (and at to halfbentazone the recommended at half the dosage)recommended were highest dosage) when were the highest herbicides when were the herbicides applied to were weeds ap- growingplied to in weeds growth growing chambers in atgrowth 30 and chambers 35 ◦C. Nevertheless, at 30 and 35 the °C control. Nevertheless, values of A.the patulus control invalues response of A. to patulus glufosinate-ammonium in response to glufosinate and mecoprop-ammonium at half and the recommendedmecoprop at half dosages the rec- increasedommended significantly dosages increased with increasing significantly growth with chamber increasing temperature. growth Inchamber particular, temperature.A. patu- lusInwas particular, 100% controlled A. patulus in responsewas 100% to glufosinate-ammonium, controlled in response bentazone, to glufosinate and-ammonium, mecoprop, atbentazone, the recommended and mecoprop, dosages at inthe growth recommended chambers dosages at 30 and in growth 35 ◦C. Inchamber a previouss at 30 study, and 35 Raphanus°C. In a raphanistrum previous study,L. grown Raphanus in controlled raphanistrum environmental L. grown in chambers controlled with environmental night/day temperatureschambers with of 5/10,night/day 15/20, temperatures and 20/25 ◦ Cof was5/10, poorly 15/20, controlledand 20/25 °C using was 1200 poorly g ai controlled ha−1 of glufosinateusing 1200 at g cooler ai ha−1 temperatures of glufosinate (5/10 at cooler◦C). By temperatures comparison, (5/10 100% °C mortality). By comparison, was achieved 100% when the temperatures were 15/20 and 20/25 ◦C at the same dosage [26]. This suggests that the atmospheric temperature can enhance the efficacy of glufosinate. On the other hand, Anderson et al. [27] reported that relative humidity had the most significant effect on the phytotoxic action of glufosinate-ammonium. The uptake of bentazone was highest for velvetleaf plants grown at high temperatures and with high moisture contents compared with plants grown at high temperatures and in drought stress conditions. This suggests Agronomy 2021, 11, 1773 12 of 17

mortality was achieved when the temperatures were 15/20 and 20/25 °C at the same dosage [26]. This suggests that the atmospheric temperature can enhance the efficacy of glufosinate. On the other hand, Anderson et al. [27] reported that relative humidity had the most significant effect on the phytotoxic action of glufosinate-ammonium. The uptake of bentazone was highest for velvetleaf plants grown at high temperatures and with high Agronomy 2021, 11, 1773 moisture contents compared with plants grown at high temperatures and in drought12 of 16 stress conditions. This suggests that plant epicuticular wax increased under drought stress conditions, which could have affected the absorption of bentazone [28]. Although this thatstudy plant examined epicuticular how different wax increased temperature under droughtconditions stress affe conditions,ct the efficacy which of herbicides could have in affectedA. patulus, the all absorption experiments of bentazone were carried [28 out]. Although at constant this levels study of examinedrelative humidity. how different There- temperaturefore, future studies conditions will affect be needed the efficacy to confirm of herbicides the effects in ofA. relative patulus, humidityall experiments on herbicide were carriedefficacy. out at constant levels of relative humidity. Therefore, future studies will be needed to confirm the effects of relative humidity on herbicide efficacy.

100 A B a a

80 b c c

60 a a d 40 b c d d 20

0 C a a D a a 100 HOR RR b b

Control value (%) Control value 80 c

d 60 c c e d

0 25 30 35 25 30 35 Temperature (℃)

Figure 9. Control value (%) of A. patulus in response to foliar herbicides (A. glyphosate isopropylamine; B. glufosinate- Figure 9. Control value (%) of A. patulus in response to foliar herbicides (A. glyphosate isopropylamine; B. glufosinate- ammonium; C. bentazone; D. mecoprop) t different temperatures in a growth chamber. HOR: Half of the recommended ammonium; C. bentazone; D. mecoprop) t different temperatures in a growth chamber. HOR: Half of the recommended rate; RR: Recommended rate. Means within bars followed by the same letters are not significantly different at the 5% level rate; RR: Recommended rate. Means within bars followed by the same letters are not significantly different at the 5% level accordingaccording to to Duncan’s Duncan’s Multiple Multiple Range Range Test. Test. Error Error bars bars represent represent SE. SE. 3.3. Herbicide Efficacy in A. patulus Grown in Greenhouse Conditions at Different Temperatures 3.3. Herbicide Efficacy in A. patulus Grown in Greenhouse Conditions at Different Temperatures In studies in greenhouse conditions, the temperature varied from day to night and is In studies in greenhouse conditions, the temperature varied from day to night and is here presented as average temperature. The control values of A. patulus were measured here presented as average temperature. The control values of A. patulus were measured after treatments with the soil-applied herbicides ethalfluralin, metolachlor, linuron, and after treatments with the soil-applied herbicides ethalfluralin, metolachlor, linuron, and alachlor under greenhouse conditions at different average temperatures (24, 26, and 28 ◦C) alachlor under greenhouse conditions at different average temperatures (24, 26, and 28 during herbicide treatment (Figure 10). When alachlor was applied at its recommended dosage, the control values were the same, regardless of the average temperature. On the other hand, when alachlor was applied at half its recommended dosage, the control

values were highest when the weeds grew in greenhouses at an average temperature of 28 ◦C. The control values were similar when metolachlor or linuron was applied at the half and full recommended dosages, regardless of the average temperature. The control values of metolachlor were 100% at both 50% and 100% of the recommended dosage. When ethalﬂuralin was applied at 50% and 100% of the recommended dosage, Agronomy 2021, 11, 1773 13 of 17

°C) during herbicide treatment (Figure 10). When alachlor was applied at its recommended dosage, the control values were the same, regardless of the average temperature. On the other hand, when alachlor was applied at half its recommended dosage, the control values were highest when the weeds grew in greenhouses at an average temperature of 28 °C. The control values were similar when metolachlor or linuron was applied at the half and full recommended dosages, regardless of the average temperature. The control Agronomy 2021, 11, 1773 values of metolachlor were 100% at both 50% and 100% of the recommended13 of 16 dosage. When ethalfluralin was applied at 50% and 100% of the recommended dosage, the control values increased with increasing average greenhouse temperature. Although not the same herbicidethe control as those values tested increased this with study, increasing flumiclorac average showed greenhouse higher temperature. activity on Although C. album (sevenfold)not the and same A. retroflexus herbicide as (threefold) those tested as this the study, temperature ﬂumiclorac increased showed higherfrom 10 activity °C to on40 °C [29]. C. album (sevenfold) and A. retroﬂexus (threefold) as the temperature increased from 10 ◦C Thisto suggests 40 ◦C[29 ].that This increased suggests that temperatures increased temperatures may increase may herbicide increase herbicide uptake, uptake, translocation, andtranslocation, effectiveness. and effectiveness.

Figure Figure10. Control 10. Control value value (%) (%)of A. of A.patulus patulus inin response to to soil-applied soil-appli herbicidesed herbicides (A. alachlor; (A. alachlor;B. metolachlor; B. metolachlor;C. ethalﬂuralin; C. ethalfluralin; DD. .linuron) linuron) atat different different average average temperatures temperatures in greenhouses. in greenhouses. HOR: Half HOR: of the Half recommended of the recommended rate; RR: Recommended rate; RR: Recom- mendedrate. rate. Means Means within within bars followedbars followed by the sameby the letters same are letters not signiﬁcantly are not significantly different at the differen 5% levelt accordingat the 5% to level Duncan’s according to Duncan’sMultiple Multiple Range Range Test. ErrorTest. barsError represent bars represent SE. SE.

ControlControl values values of of A.A. patulus patulus werewere also also measured measured afterafter treatmentstreatments with with the the foliar foliar herb- herbicides glyphosate isopropylamine, glufosinate-ammonium, bentazone, and mecoprop icidesunder glyphosate the same greenhouseisopropylamine, conditions glufosinate (Figure 11-).ammonium, When glyphosate bentazone, isopropylamine and mecoprop and under glufosinate-ammoniumthe same greenhouse were conditions applied at (Figure 50% and 11). 100% When of the glyphosate recommended isopropylamine dosages, the and glufosinatecontrol values-ammonium increased were with applied increasing at average 50% and greenhouse 100% of temperature.the recommended On the otherdosages, the controlhand, values at half itsincreased recommended with dosage,increasing the controlaverage values greenhouse of glufosinate-ammonium temperature. On were the other ◦ ◦ hand,higher at half at 26 its and recommended 28 C than at 24 dosage,C. Similarly, the control when bentazone values of or glufosinate mecoprop was-ammonium applied were higherat its at full 26 recommendedand 28 °C than dosages, at 24 °C the. Similarly, control values when increased bentazone with or increasing mecoprop average was applied greenhouse temperatures. Similar to the studies with glufosinate-ammonium, the control at itsvalues full wererecommended higher at 26 dosage and 28s◦,C the than control at 24 ◦ Cvalues when increased bentazone orwith mecoprop increasing were average greenhouseapplied at temperatures. half their recommended Similar dosages.to the studies with glufosinate-ammonium, the control

Agronomy 2021, 11, 1773 14 of 17

values were higher at 26 and 28 °C than at 24 °C when bentazone or mecoprop were ap- Agronomy 2021, 11, 1773 14 of 16 plied at half their recommended dosages.

100 A B a b

a 80 c b

c d 60 e d e 40

f 20 f

0 C D a a HOR RR b b 80

Control value (%) Controlvalue c

c c c 60 d d e

d 40

0 24 26 28 24 26 28 Average temperature (℃) of treatment period

FigureFigure 11. 11.Control Control value value (%) (%) of ofA. A. patulus patulusin in response response to to foliar foliar herbicides herbicides (A (A. glyphosate. glyphosate isopropylamine; isopropylamine;B B. glufosinate-. glufosinate- ammonium; C. bentazone; D. mecoprop) at different average temperatures in greenhouses. HOR: Half of the recom- ammonium; C. bentazone; D. mecoprop) at different average temperatures in greenhouses. HOR: Half of the recommended mended rate; RR: Recommended rate. Means within bars followed by the same letters are not significantly different at the rate; RR: Recommended rate. Means within bars followed by the same letters are not significantly different at the 5% level 5% level according to Duncan’s Multiple Range Test. Error bars represent SE. according to Duncan’s Multiple Range Test. Error bars represent SE. Previous studies with glufosinate indicate that its efficacy depends on various envi- Previous studies with glufosinate indicate that its efficacy depends on various environmental conditions, the treated weed species, and application rates [30]. Temperature, ronmental conditions, the treated weed species, and application rates [30]. Temperature, inin particular, particular, appears appears to to affect affect the the efficacy efficacy of of glufosinate. glufosinate. Anderson Anderson et et al. al. [ 27[27]] reported reported thatthat temperature temperature has has a a considerable considerable effect effect on on the the activity activity of of glufosinate glufosinate in in barley barley (Hordeum (Hordeum vulgarevulgareL.) L.) and and in in green green foxtail foxtail [Setaria [Setaria viridis viridis(L.) (L.) Beauv.]. Beauv.] An. An increased increased temperature temperature was was foundfound to to improve improve the the efficacy efficacy of of some some amino amino acid acid inhibitors; inhibitors; for for example, example, the the efficacy efficacy of of glyphosateglyphosate was was significantly significantly higher higher when when common common ragweed ragweed (Ambrosia (Ambrosia artemisiifolia artemisiifolia) was) was treatedtreated between between noon noon and and 18:00 18:00 p.m. p.m. [ 31[31].]. As As the the temperature temperature increased, increased the, the cuticle cuticle and and plasmaplasma membrane membrane fluidity fluidity increased increased in in the the leaves, leaves, resulting resulting in in improved improved herbicide herbicide uptake uptake andand translocation translocation in Desmodiumin Desmodium tortuosum tortuosum(Sw.) DC.,(Sw.) a C3 DC., weed a C3 [32 , weed33]. Similarly, [32,33]. Roundup Similarly, ReadyRoundup Soybean Ready translocated Soybean translocated more 14C-glyphosate more 14C- toglyphosate the meristematic to the meristematic tissues at 35 tissues◦C than at at35 15 °C◦C, than indicating at 15 °C, potentially indicating p increasedotentially glyphosate increased glyphosate injury at higher injury temperatures at higher tempera- [34]. Antures increase [34]. An in the increase temperature in the temperature increased three-fold increased the three efficacy-fold of the mesotrione efficacy of in mesotrioneXanthium strumariumin Xanthiumand strumariumAbutilon theophrastiiand Abutilon[32 theophrastii]. Although [32]. high Although temperatures high tendtemperatures to accelerate tend theto absorptionaccelerate the and absorption translocation and of translocation most foliar herbicides, of most foliar in some herbicides, cases, highin some temperatures cases, high also may induce a rapid metabolism, which subsequently reduces herbicide activity in target plants [32,35]. Furthermore, other environmental factors, such as precipitation, wind, soil moisture, and atmospheric humidity, also influence the application of pesticides and

Agronomy 2021, 11, 1773 15 of 16

their effectiveness [36,37]. This study suggests that environmental factors associated with the “greenhouse effect” may affect pesticide injury of crops and other non-target organisms.

4. Conclusions This study examined how climate change affects the growth of A. patulus and the efficacy of soil-applied and foliar herbicides under different environmental conditions. Germination and growth of A. patulus was higher at 25 ◦C and 30 ◦C than at 15 and 20 ◦C. In different CO2 conditions, germination and growth of A. patulus was not significantly different between growth chambers with 400 and 700 ppm of CO2. Germination and growth of A. patulus plants planted at depths of 0.5, 1, and 2 cm were significantly greater than those of plants planted at 0, 5, and 7 cm. In addition, germination and growth of A. patulus plants grown under 0, 20, and 35% shade conditions were significantly greater than those of plants grown under 50, 75, and 90% shade conditions. Under growth conditions in which temperature remained constant, the efficacy of the soil-applied herbicides ethalfluralin, metolachlor, linuron, and alachlor in A. patulus was highest when the weeds were grown at high temperature. The efficacy of the foliar herbicides glufosinate-ammonium, bentazone, and mecoprop in A. patulus was also highest when the plant was grown at high temperature; in contrast, glyphosate isopropylamine showed similar efficacy regardless of the temperature. Under growth conditions in which the temperature changed from day to night, the efficacy of the soil-applied herbicides alachlor and linuron in A. patulus was highest when the weeds were grown at high temperature. On the other hand, the efficacy of the soil-applied herbicides metolachlor and linuron in A. patulus did not differ regardless of the temperature. The efficacy of the foliar herbicides glyphosate isopropylamine, glufosinate-ammonium, bentazone, and mecoprop in A. patulus was highest when the weeds were grown at high temperature. Although the herbicide efficacy varied depending on whether the weeds were grown at constant or alternating temperatures, herbicide efficacy was generally highest when the temperature was high.

Author Contributions: Data curation, H.-H.P., writing, review, and editing, D.-J.L. and Y.-I.K. All authors have read and agreed to the published version of the manuscript. Funding: This work was carried out with the support of “Cooperative Research Program for Agricul- ture Science & Technology Development (Project No. PJ014835)” Rural Development Administration, Republic of Korea. Data Availability Statement: Not applicable. Acknowledgments: The authors acknowledge the help of Hee Kwon Kim, Byung Joon Jeong, Hyo Jin Lee, Se Ji Jang, Min Hee Park and Ok Gi Lee in plant cultivation. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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