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Echinochloa species control in maize (Zea mays L.) with sulfonylurea herbicides applied alone and in mixtures with broadleaf herbicides
Crop Protection 34 (2012) 70e75
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Echinochloa species control in maize (Zea mays L.) with sulfonylurea herbicides applied alone and in mixtures with broadleaf herbicides Christos A. Damalas a, *, Anastasios S. Lithourgidis b, Ilias G. Eleftherohorinos c a
Department of Agricultural Development, Democritus University of Thrace, 682 00 Orestiada, Greece Department of Agronomy, University Farm, Aristotle University of Thessaloniki, 570 01 Thermi, Greece c Laboratory of Agronomy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 September 2011 Received in revised form 25 November 2011 Accepted 29 November 2011
Experiments were conducted to assess the control of Echinochloa oryzoides and Echinochloa phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron applied alone or simultaneously with selected broadleaf herbicides (i.e. dicamba, MCPA, sulcotrione, and mesotrione) used in maize. In pot experiments, rimsulfuron (at 12.5 g ai/ha), nicosulfuron (at 40 g ai/ha), and foramsulfuron (at 45 g ai/ha) applied at the three- to four-leaf growth stage provided on average 88, 94, and 82% control of E. oryzoides and 81, 88, and 76% control of E. phyllopogon, respectively. The average control provided by rimsulfuron, nicosulfuron, and foramsulfuron at the four- to five-leaf growth stage was 76, 81, and 71% of E. oryzoides and 66, 82, and 62% of E. phyllopogon, respectively. Greatest control of both species at any growth stage was observed with nicosulfuron followed by the highest dose of rimsulfuron or the highest dose of foramsulfuron. Co-application of dicamba or MCPA with each sulfonylurea herbicide provided lower control of both grasses at any growth stage than the sulfonylurea alone. The addition of sulcotrione to the mixtures improved the efficacy of rimsulfuron and foramsulfuron on both species at any growth stage, whereas mesotrione did not affect the efficacy of the sulfonylureas on E. oryzoides and E. phyllopogon in most of the cases. Field experiments with the same herbicide treatments applied at the late growth stage of the two species (beginning of tillering) showed the same behavior to that observed in the pot studies regarding the efficacy of the mixtures in most of the cases, but the reduced efficacy of the treatments pointed out the necessity of the timely application of all sulfonylurea herbicides for effective control of both species. All herbicide treatments resulted in grain yield equal to that of the weed-free control without any visible symptoms of toxicity or stunted growth on maize plants. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Echinochloa oryzoides Echinochloa phyllopogon (¼ E. oryzicola) Foramsulfuron Nicosulfuron Rimsulfuron
1. Introduction The genus Echinochloa includes about 50 species that are widespread in both tropical and temperate regions of the world in dry or water-flooded soils (Michael, 1983). Some of these species are considered to be among the most troublesome weeds in rice paddy fields (Ferrero et al., 2002), whereas others are common weeds in summer crops such as maize, cotton, soybeans, tobacco, and sugarbeets. Most species of the genus Echinochloa show a remarkable variability in several morphological and physiological features. For example, Echinochloa plants may have erect or prostrate bearing and also the panicles can be almost erect or nodding in variable degree with open pyramidal or closed columnar shape
* Corresponding author. Tel.: þ30 25520 41116; fax: þ30 25520 41191. E-mail address: [email protected] (C.A. Damalas). 0261-2194/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.11.024
varying largely in colour from deep purple to pale green (Damalas et al., 2008). There is also variability in some physiological features such as the growth rate and the time of panicle emergence which promotes the adaptability of these species to different environments (Damalas et al., 2008). Susceptibility to herbicides can vary among genotypes (Espeby et al., 2011) and the differential response of weed species to herbicide applications has important implications for weed management. Increase of species that are difficult to control with herbicides often causes great concerns to farmers. Knowledge of the response to herbicides is important for the development of effective control strategies, particularly for Echinochloa species. The presence of mixed populations of these species in a field can cause difficulties in the successful chemical control because of differences in plant traits, including germination rate, tillering ability, growth rate, and also sensitivity to herbicides (Damalas et al., 2008). Thus, information on the susceptibility of various Echinochloa species to
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herbicides coupled with knowledge of the presence and population structure in the field is essential for the implementation of appropriate weed control measures in certain crops or rotations, where different herbicides are usually registered. Furthermore, knowledge of the response to herbicides may provide useful information for understanding shifts of the relative abundance of the Echinochloa weed species or populations. Although Echinochloa oryzoides (Ard.) Fritsch and Echinochloa phyllopogon (Stapf.) Koss (¼ Echinochloa oryzicola Vasing.) are mostly weeds of rice fields, they can also occur in maize fields, particularly where maize follows rice in rotation. It is worth mentioning that 80% of the rice area in the past in Greece was in rotation with maize, sugarbeets, or cotton (Ntanos, 1998). In the recent years, although only 25% of the rice in Greece is grown in rotation, these spring crops usually follow rice in rotation (I.G. Eleftherohorinos, unpublished data). Similarly, in California 30% of the rice area is grown in rotation with winter cereals, maize, cotton, sugarbeets, safflower, and vegetable crops, depending on soil and other land conditions (Hill et al., 2008). In this case, control of these grasses in maize can be a problem. Weed control in maize is of great importance because can reduce weed competition and thus minimize yield losses, protect silage feed quality, restrict weed seed production (by not allowing weeds to set seed in the field) and thus reduce contribution to the weed seedbank for the following crops. Rimsulfuron, nicosulfuron, and foramsulfuron are members of the sulfonylurea family that are used for postemergence control of grass weeds and some broadleaf weeds in maize (Prostko et al., 2006; Torma et al., 2006; Nurse et al., 2007). These herbicides act through inhibition of the enzyme acetolactate synthase also known as acetohydroxy acid synthase (ALS or AHAS; EC 4.1.3.18), which catalyzes key reactions in the biosynthesis of basic branched-chain amino acids that are essential components of the growth process in plant cell division such as valine, leucine, and isoleucine (Zhou et al., 2007). These sulfonylurea herbicides are registered for the control of grasses in maize in Greece, including Echinochloa crus-galli, whereas there is no mention on the label about the control of E. oryzoides and E. phyllopogon. The activity of rimsulfuron, nicosulfuron, and foramsulfuron has not been evaluated for the control of E. oryzoides and E. phyllopogon, though these species can be a problem when maize follows rice. From this perspective, it would be interesting to see how these grasses respond to common herbicides of maize when applied alone or in combinations. Mixtures of two or more herbicides are a common practice for broadening spectrum of weed control and also for reducing application costs (Damalas, 2004). Thus, the objective of this research was a) to evaluate the control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron applied alone and b) to evaluate the efficacy of the mixtures of these sulfonylurea herbicides with broadleaf herbicides used in maize. 2. Materials and methods 2.1. General procedures Seeds of E. oryzoides and E. phyllopogon were collected by hand from mature plants growing in rice fields of the rural area of Thessaloniki in northern Greece. Seeds were collected at the time of natural dispersal and only seeds that fell off carefully shaken plants were used. Distinction of the two Echinochloa species was based mainly on traits such as the morphology of the inflorescence according to Carretero (1981) and also the time of flowering in rice fields. Nonetheless, the classification of Echinochloa species is difficult because of the existence of numerous intergrading polymorphic complexes with many subspecies and varieties which
71
often lack conspicuous identification characters. After collection, seeds were dried in the greenhouse, air-cleaned to remove non-viable seeds and waste materials, and stored in plastic bags at 5e6 C (in a refrigerator) until the initiation of the experiments. 2.2. Pot experiments Seeds of E. oryzoides and E. phyllopogon were planted in May 2007 and 2008 in 2-L plastic pots (13.5 cm diameter by 15.5 cm height) filled with a soil mixture (soil and sand 2:1 v/v). The physicochemical characteristics of the soil used in the experiments were clay 32%, silt 56%, sand 12% (silty clay loam), organic matter 1.6%, CaCO3 7.4%, pH (1:1 H2O) 7.6 and cation exchange capacity 27.7 meq/100 g. Pots were placed outdoors and watered once daily throughout the experiments by irrigating to soil saturation. One week after seedling emergence, plants were thinned to 20 per pot, where necessary, to obtain a uniform plant population in all pots. Plants grew normally throughout the studies without experiencing any particular environmental stress conditions. Weather in the period of the pot experiments for 2007 was: mean air temperature 28.4 C, mean relative humidity 53.6%, and total precipitation 9.2 mm, whereas the respective values for 2008 were 26.5 C, 54.5%, and 43.4 mm. Two experiments were conducted in pots. In the first pot experiment, rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at three application doses, i.e. 12.5, 15, and 17.5 g ai/ha for rimsulfuron, 40, 50, and 60 g ai/ha for nicosulfuron, and 45, 52, and 59 g ai/ha for foramsulfuron when the two species were at the three- to four-leaf and at the four- to five-leaf growth stages. In the second experiment, rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at 12.5, 40, and 45 g ai/ha, respectively, and in mixture with dicamba at 288 g ai/ha, MCPA at 600 g ai/ha, sulcotrione at 450 g ai/ha, or mesotrione at 75 g ai/ha at the three- to four-leaf and at the four- to five-leaf growth stages. The formulations of the sulfonylurea herbicides were: water dispersible granules (WG) for rimsulfuron, suspension concentrate (SC) for nicosulfuron, and oil dispersion (OD) with a safener (isoxadifenethyl at 2.25% w/v) for foramsulfuron. The specific formulations are the only commercially available for these active ingredients in Greece. Application doses were based on the recommended doses of the label of each product for maize. In both experiments, all treatments of rimsulfuron were applied with the addition of a nonionic surfactant (90% isodecyl alcohol ethoxylate) at 0.1% (v/v) according to the label. All the other herbicides did not require the addition of an adjuvant at application. A non-treated control was included for each growth stage in both experiments for comparisons. The experiments were arranged in a completely randomized design with four replications (pots) for each treatment. Herbicide treatments were applied with a propane-pressurized hand-held field plot sprayer at 250 kPa pressure using 300 L/ha of water. Both experiments were repeated in time (two growing seasons) following the same procedure. Environmental conditions during applications were similar in both study periods. Each Echinochloa species was evaluated by determining fresh weight of surviving plants at 45 days after herbicide treatments. Completely desiccated plants were not included in the measurements. Fresh weight data were expressed as a percent reduction from the non-treated control (fresh weight suppression over the non-treated control) and subjected to analysis of variance (ANOVA) separately for each species and each growth stage. In particular, for the first experiment a 3 by 3 factorial approach (3 sulfonylureas by 3 application doses) was used and for the second experiment a 3 by 5 factorial approach (3 sulfonylureas by 5 mixture treatments) was used. Before the ANOVA, the fresh weight data were log-transformed to stabilize variance. Transformation did not affect mean separation and data interpretation; thus, the original means
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are presented. Differences of treatment means were compared at 5% level of significance using Fisher’s protected LSD test. 2.3. Field experiments One field experiment was conducted in 2007 and repeated in 2008 at the University Farm of Thessaloniki in northern Greece. The physicochemical characteristics of the soil were clay 32%, silt 56%, sand 12%, organic matter 1.6%, CaCO3 7.4%, pH (1:1 H2O) 7.6 and CEC 27.7 milliequivalents/100 g. Pioneer Costanza F1 hybrid maize was sown in 80-cm rows at 62,500 seeds/ha in late May in both experiments. Nitrogen (N) and phosphorus at 200 and 100 kg/ha, respectively, were incorporated before sowing and 150 kg/ha of N was applied 40 d later. A randomized complete block design with three replicates was used for each experiment. Plot size was 2.4 by 5.0 m and blocks were separated by a 2-m alley. The experiment was established on an area infested with E. oryzoides and E. phyllopogon which occurred from a seedbank that had been established for studies conducted with these species in previous years in the same area (Damalas et al., 2008). The population densities of E. oryzoides ranged from 8 to 22 plants per m2 with an average 14.8 plants (SE ¼ 0.48) for 2007 and from 6 to 18 plants per m2 with an average 11.2 plants (SE ¼ 0.51) for 2008. The population densities of E. phyllopogon ranged from 4 to 16 plants per m2 with an average 8.6 plants (SE ¼ 0.38) for 2007 and from 4 to 12 plants per m2 with an average 7.8 plants (SE ¼ 0.31) for 2008. The experimental area was also infested with several broadleaf weeds (e.g. Portulaca oleracea, Amaranthus retroflexus, Datura stramonium) and grasses (e.g. rhizome Sorghum halepense, E. crus-galli, and Setaria spp.) most of which were unevenly distributed in the field in patches of varying size and density. However, all these weeds were manually removed from the plots before the herbicide applications because their uneven distribution and the different growth stages would not allow an adequate and objective evaluation of the herbicide efficacy on these species. Rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at 12.5, 40, and 45 g ai/ha, respectively, and in mixture with dicamba at 288 g ai/ha, MCPA at 600 g ai/ha, sulcotrione at 450 g ai/ha, or mesotrione at 75 g ai/ha. The sulfonylurea herbicides were applied in the same formulations with those used in the pot experiments. Application doses were based on the recommended doses of the label of each product for maize. At the time of application, maize was at the five- to six-leaf growth stage, most E. oryzoides plants had 1e2 tillers formed (4e5 leaves) and most E. phyllopogon plants were at the beginning of tillering (3e4 leaves). This stage was selected with the purpose of assessing the efficacy of the sulfonylureas and the mixture treatments at the late growth stage assessed in the pot experiments and because this is the common practice followed by the farmers. A non-treated (weedy-infested with the two Echinochloa species only) and a weed-free control treatments were also included in the experiments. All rimsulfuron treatments were applied with the addition of a nonionic surfactant (90% isodecyl alcohol ethoxylate) at 0.1% (v/v) according to the label. All the other herbicides did not require the addition of an adjuvant at application. Herbicide treatments were applied with a propane-pressurized hand-held field plot sprayer at 250 kPa pressure using 300 L/ha of water. Maize was irrigated regularly throughout the growing seasons with a waterreel self-traveling sprinkler system. Other cultural practices during the growing season were the usual for the area. Echinochloa species control was evaluated by counting remaining healthy stems at 45 d after herbicide treatments. Stems with extensive chlorosis were considered dead. Control assessments were carried out on the 0.8- by 5.0-m area covered by the two central rows of the crop. Weed control data were expressed as
Table 1 Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron as affected by application rate (pot experiments). Treatment
Rate (g ai/ha)
Fresh weight reductiona E. oryzoides 2007
Growth stage 3e4 leaves Rimsulfuron 12.5 Rimsulfuron 15.0 Rimsulfuron 17.5 Nicosulfuron 40.0 Nicosulfuron 50.0 Nicosulfuron 60.0 Foramsulfuron 45.0 Foramsulfuron 52.0 Foramsulfuron 59.0 Growth stage 4e5 leaves Rimsulfuron 12.5 Rimsulfuron 15.0 Rimsulfuron 17.5 Nicosulfuron 40.0 Nicosulfuron 50.0 Nicosulfuron 60.0 Foramsulfuron 45.0 Foramsulfuron 52.0 Foramsulfuron 59.0
E. phyllopogon 2008
2007
2008
91 93 100 96 100 100 84 90 94
c bc a ab a a d c bc
85 87 96 92 100 100 80 86 90
d cd a b a a e d bc
83 88 94 89 96 100 76 83 89
de cd abc bcd ab a e de bcd
79 84 90 87 92 96 76 83 87
de cd b bc ab a e cd bc
78 82 90 83 98 100 73 81 89
de cd b c a a e cd b
74 78 86 79 93 96 69 77 85
cd c b c a a d c b
68 75 83 84 88 94 63 73 82
cd c b b ab a d c b
64 70 79 80 84 89 61 69 78
e d bc bc ab a e d c
a Different letters within each column in each growth stage indicate statistically significant differences at P ¼ 0.05.
Table 2 Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron as affected by partner broadleaf herbicide (pot experiments). Treatmenta
Rate (g ai/ha)
Fresh weight reductionb E. oryzoides 2007
Growth stage 3e4 leaves Rimsulfuron 12.5 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Nicosulfuron 40 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Foramsulfuron 45 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Growth stage 4e5 leaves Rimsulfuron 12.5 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Nicosulfuron 40 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Foramsulfuron 45 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75
E. phyllopogon 2008
2007
2008
91 80 81 98 92 96 92 94 100 97 84 69 54 98 86
de g g ab cd abc cd bcd a ab fg h i ab ef
85 76 77 94 87 92 87 90 96 93 80 63 50 94 82
e h gh ab de bc de cd a abc fg i j ab ef
83 70 73 89 84 89 83 86 92 91 76 56 44 90 82
de g fg abc cd abc d bcd a a ef h i ab de
79 68 71 85 80 87 80 82 88 87 76 60 40 86 78
cde f f ab bcde a bcde abcd a a ef g h ab de
78 66 68 84 80 83 78 79 87 84 73 55 41 85 75
cde g fg ab bcd abc cde bcde a ab ef h i ab de
74 62 63 80 76 79 74 75 81 79 69 51 36 81 70
cde g fg ab abcd abc cde bcde a abc ef h i a de
68 54 55 77 69 84 78 79 87 85 63 44 29 74 68
ef g g d ef ab cd bcd a ab f h i de ef
64 49 51 72 64 80 74 76 83 81 61 40 24 70 64
de f f bc de ab bc abc a ab e g h cd de
a The plus sign in parenthesis denotes a mixture with the respective sulfonylurea herbicide. b Different letters within each column in each growth stage indicate statistically significant differences at P ¼ 0.05.
C.A. Damalas et al. / Crop Protection 34 (2012) 70e75
a percent reduction from the non-treated control (stem suppression over the non-treated control). Furthermore, maize injury was visually evaluated on the two central rows of each plot. At the end of the growing season, all grained ears in the two central rows of each plot were hand harvested and machine shelled for the determination of grain yield. Grain yield was expressed as kg per ha. All data (weed control and grain yield) were subjected to ANOVA by using two-way ANOVA separately for each growing season with 17 treatments (3 sulfonylureas by 5 mixtures plus the weed-free and the non-treated control treatments) replicated three times. Before the ANOVA, weed data were square root- transformed, whereas grain yield data did not need transformation. Transformation of weed control data did not affect mean separation and interpretation; thus, the original means are presented. Differences of treatment means were compared at the 5% level of significance using Fisher’s protected LSD test. 3. Results 3.1. Pot experiments In the first pot experiment, the highest control of both E. oryzoides and E. phyllopogon at the early growth stage was achieved with nicosulfuron or with the highest dose of rimsulfuron (Table 1). Foramsulfuron at the lowest dose consistently provided the lowest control of E. oryzoides, whereas the lowest control of E. phyllopogon was observed with the lowest dose of foramsulfuron
73
or the lowest dose of rimsulfuron. At the late growth stage, although the control of both species decreased, still nicosulfuron showed the highest efficacy among the three sulfonylurea herbicides, whereas the maximum control of both species with rimsulfuron or foramsulfuron was achieved only by the highest dose of these sulfonylurea herbicides. In the second pot experiment, addition of dicamba or MCPA to the mixture reduced the efficacy of rimsulfuron and foramsulfuron on both species at the early growth stage, while the efficacy of nicosulfuron was affected less and only in the mixture with dicamba (Table 2). At the late growth stage, the reduced control with the mixtures of dicamba or MCPA was more evident for rimsulfuron and foramsulfuron compared with the early growth stage. On the contrary, addition of sulcotrione to the mixture increased the efficacy of rimsulfuron and foramsulfuron on both species compared with each sulfonylurea herbicide alone irrespective of growth stage. Mesotrione in mixture with each sulfonylurea herbicide did not affect the control of either species compared with the single application of each sulfonylurea herbicide at both growth stages. 3.2. Field experiments None of the herbicide treatments produced any visible symptoms of toxicity or stunted growth in maize plants. Nicosulfuron provided the highest control of both species in both years compared with rimsulfuron and foramsulfuron (Table 3). In both
Table 3 Control of E. oryzoides and E. phyllopogon and grain yield of maize with rimsulfuron, nicosulfuron, and foramsulfuron as affected by partner broadleaf herbicide (field experiments). Treatmenta
Rate (g ai/ha)
Stem number reductionb (beginning of tillering) E. oryzoides
2007 Rimsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Nicosulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Foramsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Non-treated control Weed-free control 2008 Rimsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Nicosulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Foramsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Non-treated control Weed-free control a b
Grain yieldb (kg/ha)
E. phyllopogon
12.5 (þ) 288 (þ) 600 (þ) 450 (þ) 75 40 (þ) 288 (þ) 600 (þ) 450 (þ) 75 45 (þ) 288 (þ) 600 (þ) 450 (þ) 75 e e
68 58 56 82 74 82 75 77 86 82 64 42 30 82 65 0 100
ef g g bc de bc d cd b bc f h i bc f j a
61 42 44 81 72 80 72 75 83 78 52 30 25 68 61 0 100
f h h bc de bc de cde b bcd g i i ef f j a
12,604 13,365 13,333 13,542 12,917 13,281 13,573 13,469 13,562 13,386 12,240 12,219 12,188 12,136 12,292 5677 13,594
a a a a a a a a a a a a a a a b a
12.5 (þ) 288 (þ) 600 (þ) 450 (þ) 75 40 (þ) 288 (þ) 600 (þ) 450 (þ) 75 45 (þ) 288 (þ) 600 (þ) 450 (þ) 75 e e
63 46 50 73 69 79 67 71 79 75 54 38 21 67 63 0 100
de fg f bc cd b cd bcd b bc ef g h cd de j a
45 33 34 65 66 73 61 67 68 67 45 22 11 58 55 0 100
f g g bcd bcd b cde bcd bc bcd f h i de e j a
11,771 12,417 12,396 12,344 12,031 12,292 12,469 12,521 12,531 11,615 11,406 11,115 10,885 11,562 11,459 5261 12,552
a a a a a a a a a a a a a a a b a
The plus sign in parenthesis denotes a mixture with the respective sulfonylurea herbicide. Different letters within each column in each growing season indicate statistically significant differences at P ¼ 0.05.
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years, the efficacy of rimsulfuron and foramsulfuron on both species was reduced when these herbicides were applied in mixture with dicamba or MCPA. The efficacy of nicosulfuron in these mixtures was affected less than the efficacy of rimsulfuron or foramsulfuron and only in mixture with dicamba. In both years, addition of sulcotrione to the mixture improved the efficacy of rimsulfuron and foramsulfuron on both species compared with the efficacy of each sulfonylurea herbicide alone. Mesotrione did not have any significant effect on the efficacy of the sulfonylurea herbicides as compared with the efficacy of each sulfonylurea herbicide alone or slightly improved the efficacy of rimsulfuron or foramsulfuron on E. phyllopogon. In all cases, grain yield was more than double of that of the non-treated control and equal to that of the weed-free control (Table 3). 4. Discussion Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron in this study varied depending on species and growth stage at application. Both species were effectively controlled with the sulfonylurea herbicides tested when these herbicides were applied preferably at an early growth stage. The greatest control of E. oryzoides and E. phyllopogon at any growth stage was observed with nicosulfuron followed by the highest dose of rimsulfuron or the highest dose of foramsulfuron. The sulfonylurea herbicides tested in this study varied considerably in terms of efficacy on E. oryzoides and E. phyllopogon. Similarly, in a recent study with other target species, Hennigh and Al-Khatib (2010) reported that E. crus-galli was the most susceptible species to rimsulfuron and nicosulfuron, whereas Digitaria sanguinalis was the least susceptible species three weeks after treatment, confirming that the activity of these herbicides (rimsulfuron and nicosulfuron) depends on weed species. Regarding foramsulfuron, previous research reported that effective weed control in maize can be achieved with about half of the recommended dose of foramsulfuron without a loss in yield (Kir and Dogan, 2009). However, satisfactory control of E. oryzoides and E. phyllopogon was achieved in our study only with increased application doses of foramsulfuron when applied preferably at an early growth stage. Similar results, but with different weed species, were reported by Baghestani et al. (2007) who found that foramsulfuron was not so effective on E. crus-galli and other grasses when applied at reduced doses. Evidently, the efficacy of foramsulfuron is strongly influenced by the sensitivity of each weed species and the herbicide doses required for 90% control of different weed species varied between 25 and 86 g ai ha1 (Nurse et al., 2007). Previous research on the control of S. halepense in maize showed that rimsulfuron applied in mixture with dicamba gave 17% lower control of S. halepense than of rimsulfuron alone (Damalas and Eleftherohorinos, 2001), which is in accordance with the results of our study regarding E. oryzoides and E. phyllopogon. Another research also showed that the co-application of mesotrione with the sulfonylurea herbicides rimsulfuron, nicosulfuron, and foramsulfuron had no adverse effects on the control of D. sanguinalis or Abutilon theophrasti in a controlled environment, but decreased the efficacy of these herbicides on Setaria viridis, Setaria glauca, and Sorghum bicolor in the field experiments (Schuster et al., 2007, 2008). In our study, the addition of mesotrione did not have any significant effect on the efficacy of the sulfonylurea herbicides on E. oryzoides and E. phyllopogon compared with the efficacy of each sulfonylurea herbicide applied alone. Similarly, no antagonistic interactions were observed in tank mixtures of foramsulfuron with either topramezone or mesotrione for the control of D. sanguinalis, E. crus-galli, S. glauca, and S. viridis var. major (Kaastra et al., 2008).
Also, mixtures of nicosulfuron with mesotrione did not show any decrease in annual grass control in maize (Skrzypczak et al., 2011). However, nicosulfuron plus rimsulfuron in mixture with certain broadleaf herbicides resulted in poorer control of E. crus-galli, S. viridis, and Setaria faberi than the single application of nicosulfuron plus rimsulfuron (Hennigh et al., 2010). The equal grain yield of the herbicide treatments to that of the weed-free control showed that in spite of the differences in the efficacy of the treatments, the suppression of weeds shortly after herbicide application allowed maize plants to grow rapidly without suffering severe competition. Weeds that were unaffected or recovered from the herbicide treatments (i.e. plants of E. oryzoides and E. phyllopogon) did not influence grain yield at harvest. Also, it seems that the relatively slow growth rate of E. oryzoides and E. phyllopogon (Damalas et al., 2008) as compared with maize plants is a disadvantage of these species when grown in maize, which grows rapidly under optimal conditions. The decreasing trend of grain yield in the treatments of foramsulfuron in 2008, particularly when applied with dicamba or MCPA, could be attributed to the low levels of control of both E. oryzoides and E. phyllopogon in these treatments, but overall the differences were not significant. Overall, data of this study indicated that E. oryzoides and E. phyllopogon can be effectively controlled in maize with single applications of the sulfonylurea herbicides rimsulfuron, nicosulfuron, or foramsulfuron. The greatest control of both grasses was observed with nicosulfuron followed in efficacy by the highest dose of rimsulfuron or the highest dose of foramsulfuron when applied preferably at an early growth stage. However, co-application of dicamba or MCPA with each sulfonylurea herbicide gave lower control of both species at any growth stage than each sulfonylurea herbicide alone. On the contrary, co-application of sulcotrione improved the efficacy of rimsulfuron and foramsulfuron on both species at any growth stage, whereas in most of the cases mesotrione did not affect significantly the efficacy of the sulfonylurea herbicides on E. oryzoides and E. phyllopogon as compared with the single applications.
References Baghestani, M.A., Zand, E., Soufizadeh, S., Eskandari, A., PourAzar, R., Veysi, M., Nassirzadeh, N., 2007. Efficacy evaluation of some dual purpose herbicides to control weeds in maize (Zea mays L.). Crop Prot. 26, 936e942. Carretero, J.L., 1981. El género Echinochloa Beauv. en el suroeste de Europa. An. Jard. Bot. Madrid 38, 91e108. Damalas, C.A., 2004. Herbicide tank mixtures: common interactions. Int. J. Agr. Biol. 6, 209e212. Damalas, C.A., Eleftherohorinos, I.G., 2001. Dicamba and atrazine antagonism on sulfonylurea herbicides used for johnsongrass (Sorghum halepense) control in maize (Zea mays). Weed Technol. 15, 62e67. Damalas, C.A., Dhima, K.V., Eleftherohorinos, I.G., 2008. Morphological and physiological variation among species of the genus Echinochloa in northern Greece. Weed Sci. 56, 416e423. Espeby, L.A., Fogelfors, H., Milberg, P., 2011. Susceptibility variation to new and established herbicides: examples of inter-population sensitivity of grass weeds. Crop Prot. 30, 429e435. Ferrero, A., Tabacchi, M., Vidotto, F., 2002. Italian rice field weeds and their control. In: Hill, J.E., Hardy, B. (Eds.), Proceedings of the 2nd Temperate Rice Conference, 13e17 June 1999, Sacramento, CA, USA, pp. 535e544. Hennigh, D.S., Al-Khatib, K., 2010. Response of barnyardgrass (Echinochloa crusgalli), green foxtail (Setaria virdis), longspine sandbur (Cenchrus longispinus), and large crabgrass (Digitaria sanguinalis) to nicosulfuron and rimsulfuron. Weed Sci. 58, 189e194. Hennigh, D.S., Al-Khatib, K., Tuinstra, M.R., 2010. Postemergence weed control in acetolactate synthase-resistant grain sorghum. Weed Technol. 24, 219e225. Hill, J.E., Roberts, S.R., Brandon, D.M., Scardaci, S.C., Williams, J.F., Mutters, R.G., 2008. Rotation Crops, Secondary Income from Rice Land, Alternative Rice Cropping Systems, No-till or Drill-seeded Rice. Rice Research and Information Program. University of California Cooperative and Extension (UCCE) Rice Project. http:// www.plantsciences.ucdavis.edu/uccerice/rice_production/rotation_crops.htm.
C.A. Damalas et al. / Crop Protection 34 (2012) 70e75 Kaastra, A.C., Swanton, C.J., Tardif, F.J., Sikkema, P.H., 2008. Two-way performance interactions among r-hydroxyphenylpyruvate dioxygenase- and acetolactate synthase-inhibiting herbicides. Weed Sci. 56, 841e851. Kir, K., Dogan, M.N., 2009. Weed control in maize (Zea mays L.) with effective minimum rates of foramsulfuron. Turk. J. Agr. For. 33, 601e610. Michael, P.W., 1983. Taxonomy and distribution of Echinochloa species with a special reference to their occurrence as weeds of rice. In: Proceedings of the Conference on Weed Control in Rice, 31 Auguste4 September 1981, Los Baños, Laguna, Philippines, pp. 291e306. Ntanos, D., 1998. Strategies for rice production and research in Greece. Cah. Opt. Medit. 50, 115e122. Nurse, R.E., Hamill, A.S., Swanton, C.J., Tardif, F.J., Sikkema, P.H., 2007. Weed control and yield response to foramsulfuron in maize. Weed Technol. 21, 453e458.
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Prostko, E.P., Grey, T.L., Davis, J.W., 2006. Texas panicum (Panicum texanum) control in irrigated field maize (Zea mays) with foramsulfuron, glyphosate, nicosulfuron, and pendimethalin. Weed Technol. 20, 961e964. Schuster, C.L., Al-Khatib, K., Dille, J.A., 2007. Mechanism of antagonism of mesotrione on sulfonylurea herbicides. Weed Sci. 55, 429e434. Schuster, C.L., Al-Khatib, K., Dille, J.A., 2008. Efficacy of sulfonylurea herbicides when tank mixed with mesotrione. Weed Technol. 22, 222e230. Skrzypczak, G.A., Sobiech, L., Waniorek, W., 2011. Evaluation of the efficacy of mesotrione plus nicosulfuron with additives as tank mixtures used for weed control in maize (Zea mays L.). J. Plant Prot. Res. 51, 300e305. Torma, M., Kazinczi, G., Hódi, L., 2006. Postemergence herbicide treatments in maize against difficult to control weeds in Hungary. J. Plant Dis. Prot. 20, 781e786. Zhou, Q., Liu, W., Zhang, Y., Liu, K.K., 2007. Action mechanisms of acetolactate synthase-inhibiting herbicides. Pestic. Biochem. Physiol. 89, 89e96.
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Echinochloa species control in maize (Zea mays L.) with sulfonylurea herbicides applied alone and in mixtures with broadleaf herbicides Christos A. Damalas a, *, Anastasios S. Lithourgidis b, Ilias G. Eleftherohorinos c a
Department of Agricultural Development, Democritus University of Thrace, 682 00 Orestiada, Greece Department of Agronomy, University Farm, Aristotle University of Thessaloniki, 570 01 Thermi, Greece c Laboratory of Agronomy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 11 September 2011 Received in revised form 25 November 2011 Accepted 29 November 2011
Experiments were conducted to assess the control of Echinochloa oryzoides and Echinochloa phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron applied alone or simultaneously with selected broadleaf herbicides (i.e. dicamba, MCPA, sulcotrione, and mesotrione) used in maize. In pot experiments, rimsulfuron (at 12.5 g ai/ha), nicosulfuron (at 40 g ai/ha), and foramsulfuron (at 45 g ai/ha) applied at the three- to four-leaf growth stage provided on average 88, 94, and 82% control of E. oryzoides and 81, 88, and 76% control of E. phyllopogon, respectively. The average control provided by rimsulfuron, nicosulfuron, and foramsulfuron at the four- to five-leaf growth stage was 76, 81, and 71% of E. oryzoides and 66, 82, and 62% of E. phyllopogon, respectively. Greatest control of both species at any growth stage was observed with nicosulfuron followed by the highest dose of rimsulfuron or the highest dose of foramsulfuron. Co-application of dicamba or MCPA with each sulfonylurea herbicide provided lower control of both grasses at any growth stage than the sulfonylurea alone. The addition of sulcotrione to the mixtures improved the efficacy of rimsulfuron and foramsulfuron on both species at any growth stage, whereas mesotrione did not affect the efficacy of the sulfonylureas on E. oryzoides and E. phyllopogon in most of the cases. Field experiments with the same herbicide treatments applied at the late growth stage of the two species (beginning of tillering) showed the same behavior to that observed in the pot studies regarding the efficacy of the mixtures in most of the cases, but the reduced efficacy of the treatments pointed out the necessity of the timely application of all sulfonylurea herbicides for effective control of both species. All herbicide treatments resulted in grain yield equal to that of the weed-free control without any visible symptoms of toxicity or stunted growth on maize plants. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Echinochloa oryzoides Echinochloa phyllopogon (¼ E. oryzicola) Foramsulfuron Nicosulfuron Rimsulfuron
1. Introduction The genus Echinochloa includes about 50 species that are widespread in both tropical and temperate regions of the world in dry or water-flooded soils (Michael, 1983). Some of these species are considered to be among the most troublesome weeds in rice paddy fields (Ferrero et al., 2002), whereas others are common weeds in summer crops such as maize, cotton, soybeans, tobacco, and sugarbeets. Most species of the genus Echinochloa show a remarkable variability in several morphological and physiological features. For example, Echinochloa plants may have erect or prostrate bearing and also the panicles can be almost erect or nodding in variable degree with open pyramidal or closed columnar shape
* Corresponding author. Tel.: þ30 25520 41116; fax: þ30 25520 41191. E-mail address: [email protected] (C.A. Damalas). 0261-2194/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.11.024
varying largely in colour from deep purple to pale green (Damalas et al., 2008). There is also variability in some physiological features such as the growth rate and the time of panicle emergence which promotes the adaptability of these species to different environments (Damalas et al., 2008). Susceptibility to herbicides can vary among genotypes (Espeby et al., 2011) and the differential response of weed species to herbicide applications has important implications for weed management. Increase of species that are difficult to control with herbicides often causes great concerns to farmers. Knowledge of the response to herbicides is important for the development of effective control strategies, particularly for Echinochloa species. The presence of mixed populations of these species in a field can cause difficulties in the successful chemical control because of differences in plant traits, including germination rate, tillering ability, growth rate, and also sensitivity to herbicides (Damalas et al., 2008). Thus, information on the susceptibility of various Echinochloa species to
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herbicides coupled with knowledge of the presence and population structure in the field is essential for the implementation of appropriate weed control measures in certain crops or rotations, where different herbicides are usually registered. Furthermore, knowledge of the response to herbicides may provide useful information for understanding shifts of the relative abundance of the Echinochloa weed species or populations. Although Echinochloa oryzoides (Ard.) Fritsch and Echinochloa phyllopogon (Stapf.) Koss (¼ Echinochloa oryzicola Vasing.) are mostly weeds of rice fields, they can also occur in maize fields, particularly where maize follows rice in rotation. It is worth mentioning that 80% of the rice area in the past in Greece was in rotation with maize, sugarbeets, or cotton (Ntanos, 1998). In the recent years, although only 25% of the rice in Greece is grown in rotation, these spring crops usually follow rice in rotation (I.G. Eleftherohorinos, unpublished data). Similarly, in California 30% of the rice area is grown in rotation with winter cereals, maize, cotton, sugarbeets, safflower, and vegetable crops, depending on soil and other land conditions (Hill et al., 2008). In this case, control of these grasses in maize can be a problem. Weed control in maize is of great importance because can reduce weed competition and thus minimize yield losses, protect silage feed quality, restrict weed seed production (by not allowing weeds to set seed in the field) and thus reduce contribution to the weed seedbank for the following crops. Rimsulfuron, nicosulfuron, and foramsulfuron are members of the sulfonylurea family that are used for postemergence control of grass weeds and some broadleaf weeds in maize (Prostko et al., 2006; Torma et al., 2006; Nurse et al., 2007). These herbicides act through inhibition of the enzyme acetolactate synthase also known as acetohydroxy acid synthase (ALS or AHAS; EC 4.1.3.18), which catalyzes key reactions in the biosynthesis of basic branched-chain amino acids that are essential components of the growth process in plant cell division such as valine, leucine, and isoleucine (Zhou et al., 2007). These sulfonylurea herbicides are registered for the control of grasses in maize in Greece, including Echinochloa crus-galli, whereas there is no mention on the label about the control of E. oryzoides and E. phyllopogon. The activity of rimsulfuron, nicosulfuron, and foramsulfuron has not been evaluated for the control of E. oryzoides and E. phyllopogon, though these species can be a problem when maize follows rice. From this perspective, it would be interesting to see how these grasses respond to common herbicides of maize when applied alone or in combinations. Mixtures of two or more herbicides are a common practice for broadening spectrum of weed control and also for reducing application costs (Damalas, 2004). Thus, the objective of this research was a) to evaluate the control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron applied alone and b) to evaluate the efficacy of the mixtures of these sulfonylurea herbicides with broadleaf herbicides used in maize. 2. Materials and methods 2.1. General procedures Seeds of E. oryzoides and E. phyllopogon were collected by hand from mature plants growing in rice fields of the rural area of Thessaloniki in northern Greece. Seeds were collected at the time of natural dispersal and only seeds that fell off carefully shaken plants were used. Distinction of the two Echinochloa species was based mainly on traits such as the morphology of the inflorescence according to Carretero (1981) and also the time of flowering in rice fields. Nonetheless, the classification of Echinochloa species is difficult because of the existence of numerous intergrading polymorphic complexes with many subspecies and varieties which
71
often lack conspicuous identification characters. After collection, seeds were dried in the greenhouse, air-cleaned to remove non-viable seeds and waste materials, and stored in plastic bags at 5e6 C (in a refrigerator) until the initiation of the experiments. 2.2. Pot experiments Seeds of E. oryzoides and E. phyllopogon were planted in May 2007 and 2008 in 2-L plastic pots (13.5 cm diameter by 15.5 cm height) filled with a soil mixture (soil and sand 2:1 v/v). The physicochemical characteristics of the soil used in the experiments were clay 32%, silt 56%, sand 12% (silty clay loam), organic matter 1.6%, CaCO3 7.4%, pH (1:1 H2O) 7.6 and cation exchange capacity 27.7 meq/100 g. Pots were placed outdoors and watered once daily throughout the experiments by irrigating to soil saturation. One week after seedling emergence, plants were thinned to 20 per pot, where necessary, to obtain a uniform plant population in all pots. Plants grew normally throughout the studies without experiencing any particular environmental stress conditions. Weather in the period of the pot experiments for 2007 was: mean air temperature 28.4 C, mean relative humidity 53.6%, and total precipitation 9.2 mm, whereas the respective values for 2008 were 26.5 C, 54.5%, and 43.4 mm. Two experiments were conducted in pots. In the first pot experiment, rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at three application doses, i.e. 12.5, 15, and 17.5 g ai/ha for rimsulfuron, 40, 50, and 60 g ai/ha for nicosulfuron, and 45, 52, and 59 g ai/ha for foramsulfuron when the two species were at the three- to four-leaf and at the four- to five-leaf growth stages. In the second experiment, rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at 12.5, 40, and 45 g ai/ha, respectively, and in mixture with dicamba at 288 g ai/ha, MCPA at 600 g ai/ha, sulcotrione at 450 g ai/ha, or mesotrione at 75 g ai/ha at the three- to four-leaf and at the four- to five-leaf growth stages. The formulations of the sulfonylurea herbicides were: water dispersible granules (WG) for rimsulfuron, suspension concentrate (SC) for nicosulfuron, and oil dispersion (OD) with a safener (isoxadifenethyl at 2.25% w/v) for foramsulfuron. The specific formulations are the only commercially available for these active ingredients in Greece. Application doses were based on the recommended doses of the label of each product for maize. In both experiments, all treatments of rimsulfuron were applied with the addition of a nonionic surfactant (90% isodecyl alcohol ethoxylate) at 0.1% (v/v) according to the label. All the other herbicides did not require the addition of an adjuvant at application. A non-treated control was included for each growth stage in both experiments for comparisons. The experiments were arranged in a completely randomized design with four replications (pots) for each treatment. Herbicide treatments were applied with a propane-pressurized hand-held field plot sprayer at 250 kPa pressure using 300 L/ha of water. Both experiments were repeated in time (two growing seasons) following the same procedure. Environmental conditions during applications were similar in both study periods. Each Echinochloa species was evaluated by determining fresh weight of surviving plants at 45 days after herbicide treatments. Completely desiccated plants were not included in the measurements. Fresh weight data were expressed as a percent reduction from the non-treated control (fresh weight suppression over the non-treated control) and subjected to analysis of variance (ANOVA) separately for each species and each growth stage. In particular, for the first experiment a 3 by 3 factorial approach (3 sulfonylureas by 3 application doses) was used and for the second experiment a 3 by 5 factorial approach (3 sulfonylureas by 5 mixture treatments) was used. Before the ANOVA, the fresh weight data were log-transformed to stabilize variance. Transformation did not affect mean separation and data interpretation; thus, the original means
72
C.A. Damalas et al. / Crop Protection 34 (2012) 70e75
are presented. Differences of treatment means were compared at 5% level of significance using Fisher’s protected LSD test. 2.3. Field experiments One field experiment was conducted in 2007 and repeated in 2008 at the University Farm of Thessaloniki in northern Greece. The physicochemical characteristics of the soil were clay 32%, silt 56%, sand 12%, organic matter 1.6%, CaCO3 7.4%, pH (1:1 H2O) 7.6 and CEC 27.7 milliequivalents/100 g. Pioneer Costanza F1 hybrid maize was sown in 80-cm rows at 62,500 seeds/ha in late May in both experiments. Nitrogen (N) and phosphorus at 200 and 100 kg/ha, respectively, were incorporated before sowing and 150 kg/ha of N was applied 40 d later. A randomized complete block design with three replicates was used for each experiment. Plot size was 2.4 by 5.0 m and blocks were separated by a 2-m alley. The experiment was established on an area infested with E. oryzoides and E. phyllopogon which occurred from a seedbank that had been established for studies conducted with these species in previous years in the same area (Damalas et al., 2008). The population densities of E. oryzoides ranged from 8 to 22 plants per m2 with an average 14.8 plants (SE ¼ 0.48) for 2007 and from 6 to 18 plants per m2 with an average 11.2 plants (SE ¼ 0.51) for 2008. The population densities of E. phyllopogon ranged from 4 to 16 plants per m2 with an average 8.6 plants (SE ¼ 0.38) for 2007 and from 4 to 12 plants per m2 with an average 7.8 plants (SE ¼ 0.31) for 2008. The experimental area was also infested with several broadleaf weeds (e.g. Portulaca oleracea, Amaranthus retroflexus, Datura stramonium) and grasses (e.g. rhizome Sorghum halepense, E. crus-galli, and Setaria spp.) most of which were unevenly distributed in the field in patches of varying size and density. However, all these weeds were manually removed from the plots before the herbicide applications because their uneven distribution and the different growth stages would not allow an adequate and objective evaluation of the herbicide efficacy on these species. Rimsulfuron, nicosulfuron, and foramsulfuron were applied alone at 12.5, 40, and 45 g ai/ha, respectively, and in mixture with dicamba at 288 g ai/ha, MCPA at 600 g ai/ha, sulcotrione at 450 g ai/ha, or mesotrione at 75 g ai/ha. The sulfonylurea herbicides were applied in the same formulations with those used in the pot experiments. Application doses were based on the recommended doses of the label of each product for maize. At the time of application, maize was at the five- to six-leaf growth stage, most E. oryzoides plants had 1e2 tillers formed (4e5 leaves) and most E. phyllopogon plants were at the beginning of tillering (3e4 leaves). This stage was selected with the purpose of assessing the efficacy of the sulfonylureas and the mixture treatments at the late growth stage assessed in the pot experiments and because this is the common practice followed by the farmers. A non-treated (weedy-infested with the two Echinochloa species only) and a weed-free control treatments were also included in the experiments. All rimsulfuron treatments were applied with the addition of a nonionic surfactant (90% isodecyl alcohol ethoxylate) at 0.1% (v/v) according to the label. All the other herbicides did not require the addition of an adjuvant at application. Herbicide treatments were applied with a propane-pressurized hand-held field plot sprayer at 250 kPa pressure using 300 L/ha of water. Maize was irrigated regularly throughout the growing seasons with a waterreel self-traveling sprinkler system. Other cultural practices during the growing season were the usual for the area. Echinochloa species control was evaluated by counting remaining healthy stems at 45 d after herbicide treatments. Stems with extensive chlorosis were considered dead. Control assessments were carried out on the 0.8- by 5.0-m area covered by the two central rows of the crop. Weed control data were expressed as
Table 1 Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron as affected by application rate (pot experiments). Treatment
Rate (g ai/ha)
Fresh weight reductiona E. oryzoides 2007
Growth stage 3e4 leaves Rimsulfuron 12.5 Rimsulfuron 15.0 Rimsulfuron 17.5 Nicosulfuron 40.0 Nicosulfuron 50.0 Nicosulfuron 60.0 Foramsulfuron 45.0 Foramsulfuron 52.0 Foramsulfuron 59.0 Growth stage 4e5 leaves Rimsulfuron 12.5 Rimsulfuron 15.0 Rimsulfuron 17.5 Nicosulfuron 40.0 Nicosulfuron 50.0 Nicosulfuron 60.0 Foramsulfuron 45.0 Foramsulfuron 52.0 Foramsulfuron 59.0
E. phyllopogon 2008
2007
2008
91 93 100 96 100 100 84 90 94
c bc a ab a a d c bc
85 87 96 92 100 100 80 86 90
d cd a b a a e d bc
83 88 94 89 96 100 76 83 89
de cd abc bcd ab a e de bcd
79 84 90 87 92 96 76 83 87
de cd b bc ab a e cd bc
78 82 90 83 98 100 73 81 89
de cd b c a a e cd b
74 78 86 79 93 96 69 77 85
cd c b c a a d c b
68 75 83 84 88 94 63 73 82
cd c b b ab a d c b
64 70 79 80 84 89 61 69 78
e d bc bc ab a e d c
a Different letters within each column in each growth stage indicate statistically significant differences at P ¼ 0.05.
Table 2 Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron as affected by partner broadleaf herbicide (pot experiments). Treatmenta
Rate (g ai/ha)
Fresh weight reductionb E. oryzoides 2007
Growth stage 3e4 leaves Rimsulfuron 12.5 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Nicosulfuron 40 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Foramsulfuron 45 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Growth stage 4e5 leaves Rimsulfuron 12.5 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Nicosulfuron 40 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75 Foramsulfuron 45 (þ) dicamba (þ) 288 (þ) MCPA (þ) 600 (þ) sulcotrione (þ) 450 (þ) mesotrione (þ) 75
E. phyllopogon 2008
2007
2008
91 80 81 98 92 96 92 94 100 97 84 69 54 98 86
de g g ab cd abc cd bcd a ab fg h i ab ef
85 76 77 94 87 92 87 90 96 93 80 63 50 94 82
e h gh ab de bc de cd a abc fg i j ab ef
83 70 73 89 84 89 83 86 92 91 76 56 44 90 82
de g fg abc cd abc d bcd a a ef h i ab de
79 68 71 85 80 87 80 82 88 87 76 60 40 86 78
cde f f ab bcde a bcde abcd a a ef g h ab de
78 66 68 84 80 83 78 79 87 84 73 55 41 85 75
cde g fg ab bcd abc cde bcde a ab ef h i ab de
74 62 63 80 76 79 74 75 81 79 69 51 36 81 70
cde g fg ab abcd abc cde bcde a abc ef h i a de
68 54 55 77 69 84 78 79 87 85 63 44 29 74 68
ef g g d ef ab cd bcd a ab f h i de ef
64 49 51 72 64 80 74 76 83 81 61 40 24 70 64
de f f bc de ab bc abc a ab e g h cd de
a The plus sign in parenthesis denotes a mixture with the respective sulfonylurea herbicide. b Different letters within each column in each growth stage indicate statistically significant differences at P ¼ 0.05.
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a percent reduction from the non-treated control (stem suppression over the non-treated control). Furthermore, maize injury was visually evaluated on the two central rows of each plot. At the end of the growing season, all grained ears in the two central rows of each plot were hand harvested and machine shelled for the determination of grain yield. Grain yield was expressed as kg per ha. All data (weed control and grain yield) were subjected to ANOVA by using two-way ANOVA separately for each growing season with 17 treatments (3 sulfonylureas by 5 mixtures plus the weed-free and the non-treated control treatments) replicated three times. Before the ANOVA, weed data were square root- transformed, whereas grain yield data did not need transformation. Transformation of weed control data did not affect mean separation and interpretation; thus, the original means are presented. Differences of treatment means were compared at the 5% level of significance using Fisher’s protected LSD test. 3. Results 3.1. Pot experiments In the first pot experiment, the highest control of both E. oryzoides and E. phyllopogon at the early growth stage was achieved with nicosulfuron or with the highest dose of rimsulfuron (Table 1). Foramsulfuron at the lowest dose consistently provided the lowest control of E. oryzoides, whereas the lowest control of E. phyllopogon was observed with the lowest dose of foramsulfuron
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or the lowest dose of rimsulfuron. At the late growth stage, although the control of both species decreased, still nicosulfuron showed the highest efficacy among the three sulfonylurea herbicides, whereas the maximum control of both species with rimsulfuron or foramsulfuron was achieved only by the highest dose of these sulfonylurea herbicides. In the second pot experiment, addition of dicamba or MCPA to the mixture reduced the efficacy of rimsulfuron and foramsulfuron on both species at the early growth stage, while the efficacy of nicosulfuron was affected less and only in the mixture with dicamba (Table 2). At the late growth stage, the reduced control with the mixtures of dicamba or MCPA was more evident for rimsulfuron and foramsulfuron compared with the early growth stage. On the contrary, addition of sulcotrione to the mixture increased the efficacy of rimsulfuron and foramsulfuron on both species compared with each sulfonylurea herbicide alone irrespective of growth stage. Mesotrione in mixture with each sulfonylurea herbicide did not affect the control of either species compared with the single application of each sulfonylurea herbicide at both growth stages. 3.2. Field experiments None of the herbicide treatments produced any visible symptoms of toxicity or stunted growth in maize plants. Nicosulfuron provided the highest control of both species in both years compared with rimsulfuron and foramsulfuron (Table 3). In both
Table 3 Control of E. oryzoides and E. phyllopogon and grain yield of maize with rimsulfuron, nicosulfuron, and foramsulfuron as affected by partner broadleaf herbicide (field experiments). Treatmenta
Rate (g ai/ha)
Stem number reductionb (beginning of tillering) E. oryzoides
2007 Rimsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Nicosulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Foramsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Non-treated control Weed-free control 2008 Rimsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Nicosulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Foramsulfuron (þ) dicamba (þ) MCPA (þ) sulcotrione (þ) mesotrione Non-treated control Weed-free control a b
Grain yieldb (kg/ha)
E. phyllopogon
12.5 (þ) 288 (þ) 600 (þ) 450 (þ) 75 40 (þ) 288 (þ) 600 (þ) 450 (þ) 75 45 (þ) 288 (þ) 600 (þ) 450 (þ) 75 e e
68 58 56 82 74 82 75 77 86 82 64 42 30 82 65 0 100
ef g g bc de bc d cd b bc f h i bc f j a
61 42 44 81 72 80 72 75 83 78 52 30 25 68 61 0 100
f h h bc de bc de cde b bcd g i i ef f j a
12,604 13,365 13,333 13,542 12,917 13,281 13,573 13,469 13,562 13,386 12,240 12,219 12,188 12,136 12,292 5677 13,594
a a a a a a a a a a a a a a a b a
12.5 (þ) 288 (þ) 600 (þ) 450 (þ) 75 40 (þ) 288 (þ) 600 (þ) 450 (þ) 75 45 (þ) 288 (þ) 600 (þ) 450 (þ) 75 e e
63 46 50 73 69 79 67 71 79 75 54 38 21 67 63 0 100
de fg f bc cd b cd bcd b bc ef g h cd de j a
45 33 34 65 66 73 61 67 68 67 45 22 11 58 55 0 100
f g g bcd bcd b cde bcd bc bcd f h i de e j a
11,771 12,417 12,396 12,344 12,031 12,292 12,469 12,521 12,531 11,615 11,406 11,115 10,885 11,562 11,459 5261 12,552
a a a a a a a a a a a a a a a b a
The plus sign in parenthesis denotes a mixture with the respective sulfonylurea herbicide. Different letters within each column in each growing season indicate statistically significant differences at P ¼ 0.05.
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C.A. Damalas et al. / Crop Protection 34 (2012) 70e75
years, the efficacy of rimsulfuron and foramsulfuron on both species was reduced when these herbicides were applied in mixture with dicamba or MCPA. The efficacy of nicosulfuron in these mixtures was affected less than the efficacy of rimsulfuron or foramsulfuron and only in mixture with dicamba. In both years, addition of sulcotrione to the mixture improved the efficacy of rimsulfuron and foramsulfuron on both species compared with the efficacy of each sulfonylurea herbicide alone. Mesotrione did not have any significant effect on the efficacy of the sulfonylurea herbicides as compared with the efficacy of each sulfonylurea herbicide alone or slightly improved the efficacy of rimsulfuron or foramsulfuron on E. phyllopogon. In all cases, grain yield was more than double of that of the non-treated control and equal to that of the weed-free control (Table 3). 4. Discussion Control of E. oryzoides and E. phyllopogon with rimsulfuron, nicosulfuron, and foramsulfuron in this study varied depending on species and growth stage at application. Both species were effectively controlled with the sulfonylurea herbicides tested when these herbicides were applied preferably at an early growth stage. The greatest control of E. oryzoides and E. phyllopogon at any growth stage was observed with nicosulfuron followed by the highest dose of rimsulfuron or the highest dose of foramsulfuron. The sulfonylurea herbicides tested in this study varied considerably in terms of efficacy on E. oryzoides and E. phyllopogon. Similarly, in a recent study with other target species, Hennigh and Al-Khatib (2010) reported that E. crus-galli was the most susceptible species to rimsulfuron and nicosulfuron, whereas Digitaria sanguinalis was the least susceptible species three weeks after treatment, confirming that the activity of these herbicides (rimsulfuron and nicosulfuron) depends on weed species. Regarding foramsulfuron, previous research reported that effective weed control in maize can be achieved with about half of the recommended dose of foramsulfuron without a loss in yield (Kir and Dogan, 2009). However, satisfactory control of E. oryzoides and E. phyllopogon was achieved in our study only with increased application doses of foramsulfuron when applied preferably at an early growth stage. Similar results, but with different weed species, were reported by Baghestani et al. (2007) who found that foramsulfuron was not so effective on E. crus-galli and other grasses when applied at reduced doses. Evidently, the efficacy of foramsulfuron is strongly influenced by the sensitivity of each weed species and the herbicide doses required for 90% control of different weed species varied between 25 and 86 g ai ha1 (Nurse et al., 2007). Previous research on the control of S. halepense in maize showed that rimsulfuron applied in mixture with dicamba gave 17% lower control of S. halepense than of rimsulfuron alone (Damalas and Eleftherohorinos, 2001), which is in accordance with the results of our study regarding E. oryzoides and E. phyllopogon. Another research also showed that the co-application of mesotrione with the sulfonylurea herbicides rimsulfuron, nicosulfuron, and foramsulfuron had no adverse effects on the control of D. sanguinalis or Abutilon theophrasti in a controlled environment, but decreased the efficacy of these herbicides on Setaria viridis, Setaria glauca, and Sorghum bicolor in the field experiments (Schuster et al., 2007, 2008). In our study, the addition of mesotrione did not have any significant effect on the efficacy of the sulfonylurea herbicides on E. oryzoides and E. phyllopogon compared with the efficacy of each sulfonylurea herbicide applied alone. Similarly, no antagonistic interactions were observed in tank mixtures of foramsulfuron with either topramezone or mesotrione for the control of D. sanguinalis, E. crus-galli, S. glauca, and S. viridis var. major (Kaastra et al., 2008).
Also, mixtures of nicosulfuron with mesotrione did not show any decrease in annual grass control in maize (Skrzypczak et al., 2011). However, nicosulfuron plus rimsulfuron in mixture with certain broadleaf herbicides resulted in poorer control of E. crus-galli, S. viridis, and Setaria faberi than the single application of nicosulfuron plus rimsulfuron (Hennigh et al., 2010). The equal grain yield of the herbicide treatments to that of the weed-free control showed that in spite of the differences in the efficacy of the treatments, the suppression of weeds shortly after herbicide application allowed maize plants to grow rapidly without suffering severe competition. Weeds that were unaffected or recovered from the herbicide treatments (i.e. plants of E. oryzoides and E. phyllopogon) did not influence grain yield at harvest. Also, it seems that the relatively slow growth rate of E. oryzoides and E. phyllopogon (Damalas et al., 2008) as compared with maize plants is a disadvantage of these species when grown in maize, which grows rapidly under optimal conditions. The decreasing trend of grain yield in the treatments of foramsulfuron in 2008, particularly when applied with dicamba or MCPA, could be attributed to the low levels of control of both E. oryzoides and E. phyllopogon in these treatments, but overall the differences were not significant. Overall, data of this study indicated that E. oryzoides and E. phyllopogon can be effectively controlled in maize with single applications of the sulfonylurea herbicides rimsulfuron, nicosulfuron, or foramsulfuron. The greatest control of both grasses was observed with nicosulfuron followed in efficacy by the highest dose of rimsulfuron or the highest dose of foramsulfuron when applied preferably at an early growth stage. However, co-application of dicamba or MCPA with each sulfonylurea herbicide gave lower control of both species at any growth stage than each sulfonylurea herbicide alone. On the contrary, co-application of sulcotrione improved the efficacy of rimsulfuron and foramsulfuron on both species at any growth stage, whereas in most of the cases mesotrione did not affect significantly the efficacy of the sulfonylurea herbicides on E. oryzoides and E. phyllopogon as compared with the single applications.
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