Effects of Methylated Soybean Oil Adjuvant on Fomesafen Efficacy to Weeds

Han Yu-jun, Fu Jiu-cai, Wang Qian-yu, and Tao Bo*, and Mao Zi-jun

1Heilongjiang Academy of Agricultural Sciences Postdoctoral Programme, Harbin 150086, China; Northeast Forestry University Postdoctoral Programme, Harbin 150040, China

2College of Agriculture, Northeast Agricultural University, Harbin 150030, China

3Jiamusi Branch, Heilongjiang Academy of Agricultural Sciences, Jiamusi 154007, Heilongjiang, China

4Northeast Forestry University Postdoctoral Programme, Harbin 150040, China

Effects of Methylated Soybean Oil Adjuvant on Fomesafen Efficacy to Weeds

Han Yu-jun1,2, Fu Jiu-cai3, Wang Qian-yu3, and Tao Bo2*, and Mao Zi-jun4

1Heilongjiang Academy of Agricultural Sciences Postdoctoral Programme, Harbin 150086, China; Northeast Forestry University Postdoctoral Programme, Harbin 150040, China

2College of Agriculture, Northeast Agricultural University, Harbin 150030, China

3Jiamusi Branch, Heilongjiang Academy of Agricultural Sciences, Jiamusi 154007, Heilongjiang, China

4Northeast Forestry University Postdoctoral Programme, Harbin 150040, China

Tank-mix adjuvant has the potential to improve the weed control efficacy of post-emergence herbicides. In order to study the synergistic effect of adjuvant, the effects of different rates of fomesafen alone or applied methylated soybean oil adjuvant (MSO) were sprayed on redroot pigweed, abutilon and black nightshade under greenhouse condition. The results showed that fomesafen had different performance on the three weeds, and MSO adjuvant could effectively increase the control. The nightshade control was lower than other two weeds with all the fomesafen doses from 131.25 to 506.25 ga.i. • hm-2with or without adjuvant. The control of abutilon was between the black nightshade and the redroot pigweed, and had better control at 375 ga.i. • hm-2with adjuvant or 506.25 ga.i. • hm-2alone or with adjuvant respectively. The results indicated that mixing adjuvant with fomesafen improved the control on weeds, especially at the low rate. Black nightshade was more difficult to control. The redroot pigweed had the most susceptibility to fomesafen alone or with adjuvant.

fomesafen, methylated soybean oil adjuvant (MSO), weed control, synergistic effect

Introduction

Soybean is one of the most important crops in China, especially in Heilongjiang Province with crop cultivated over 4.5 million hectares (Zhang, 2012). The most negative factor for soybean production is weed competition (Zhao et al., 2010). Amaranthus retroflexus, Xanthium strumarium, Solanium nigrum and Abutilon theophrasti are the common broadleaf weeds in soybean field with heavy hazard. Most of the pre-emergence and post-emergence herbicides are applied to control weed growth and manage weed shift, such as metribuzin, bentazon and fomesafen. Some herbicides usually have worse weed control, or cause crop injury and yield loss applied in the condition of worse weather or at incorrect application time (Lu and Xu, 2006; Fu, 2011).

Fomesafen, one of the diphenylether herbicide, is a post-emergence herbicide with high selectivity and high herbicidal activity at low application rate, specifically used for the early post-emergence controlof broadleaf weeds in soybean and bean (Santos et al., 2006), and is the most extensive applied herbicide in soybean around China (Duan et al., 2010; Zuo, 2011). But in the recent year, fomesafen usually caused crop injury, reduced plant weight of corn, wheat and rapeseed, as fomesafen had longer residual period and higher applied rate (Wang et al., 2013).

Adjuvant can increase herbicide activity, reduce herbicide dosage and modify environment damage. Lu et al. (2004) reported adjuvants could reduce the surface tension of herbicide solution and contact angle between the droplet and leaf, increase the maximum leaf retention of the dilution, dry duration, adjust the viscosity of herbicide solution, thereby improve the herbicide performance and effectively control weed (Zhang and Zhang, 2011; Han et al., 2012; Liu and Zhang, 2013). Ramsdale and Messersmith (2001) and Lu et al. (2004) reported that mixing adjuvants with fomesafen increased weed control. But, not all adjuvants have synergistic effects to all the herbicides, they had specificity for some herbicides. Singh (2005) reported that adjuvant usage improved the efficacy of fomesafen more than it did with bentazon on weeds, such as velvetleaf, ragweed and nightshade. Abouziena et al. (2009) found in his trial that induce or kinetic adjuvant had more synergistic effects than ammonium sulfate for benzaton.

The aims of this research were to examine the performance of fomesafen alone with different doses on different weeds and investigate the synergistic effects of methylated soybean oil (MSO) adjuvant on fomesafen herbicidal activity.

Materials and Methods

Greenhouse trials were initiated in 2012 at Xiangfang Experiment and Practice Base, Northeast Agricultural University, Harbin, China. The soil at the experiment site was black soil with 2.9% organic matter and pH 6.9. The soil was collected from a 0-15 cm depth from a field with no herbicide application.

Weed seeds of three selected broadleaf weed species: redroot pigweed (Amaranthus retroflexus L.), black nightshade (Solanium nigrum L.), and abutilon (Abutilon theophrasti Medic.) were collected from Harbin Soybean Fields. Weed seeds were planted in pots of 5.0 L capacity and 30 cm height. After emergence, every pot was kept 10 seedlings of uniform and healthy growth. Weed seedlings were grown in the greenhouse under average day/night temperature 26℃/ 17℃, under natural daylight conditions, and watered daily.

Fomesafen were sprayed at the five-leaf stage using a KNAPSACK Hydraulic Sprayer delivering 225 L • hm-2(15 L • 667 m-2) using Teejet 80015 flat fan nozzles. Treatments consisted of fomesafen (Beijixing, commercial product, Libennonghua) doses at 131.25, 262.5, 375 and 506.25 ga.i. • hm-2(the typical use rate of 375 ga.i. • hm-2) alone, and tank-mixing with the Jingfuwa (a methylated soybean oil adjuvant) at 0.1% (v/v). A non-treated check was included in each trial representing the zero dose.

Visual observations on mortality were recorded for 14 days and 21 days after treatment (DAT). The scale used for percent injury ranged from 0 (no visible injury) to 100% (complete death). Experiments were designed in randomized complete block with four replications and were repeated in time under similar conditions. All the data were subjected to analyze the variance (Duncan) using DPS statistical software.

Results

Redroot pigweed

Fomesafen applied at the lowest rate (131.25 ga.i. • hm-2) alone provided 53.3% and 56.0% stem control and 59.3% fresh weight control of redroot pigweed for 14 DAT and 21 DAT, after addition of MSO in the tankmixture, the control was 64.3%, 68.3% and 71.0%, increased by 11%-12.3%. Fomesafen applied at low rate (262.5 ga.i. • hm-2) alone provided 66.7% and 71.7% stem control and 75.3% fresh weight control of redroot pigweed for 14 DAT and 21 DAT with adjuvant, after addition of MSO in the tank-mixture,the control was 86.7%, 88.3% and 88.7%, increased by 15.4%-20.0%. Fomesafen applied at rate (375 and 506.25 ga.i. • hm-2) alone provided at least 83.3% and 93.3% control of redroot pigweed for 14 DAT, addition of MSO in tank-mixture with the rate of fomesafen (375 and 506.25 ga.i. • hm-2) improved redroot pigweed control by16.7% (from 83.3% to 100%) and provided complete foliar death for 14 DAT (Table 1).

Table 1 Efficacy control of fomesafen with MSO adjuvant on redroot pigweed

MSO adjuvant had the synergistic effect to fomesafen, especially at the low rate. Mixing MSO with fomesafen significantly surpassed fomesafen applied alone. Fomesafen at 131.25 ga.i. • hm-2with MSO adjuvant controlled redroot pigweed equal to fomesafen at 262.5 ga.i. • hm-2. Similarly, fomesafen at 262.5 ga.i. • hm-2with MSO adjuvant controlled redroot pigweed equal to fomesafen at 375 ga.i. • hm-2and fomesafen at 375 ga.i. • hm-2with MSO adjuvant provided complete foliar death.

The results suggested that redroot pigweed was easily controlled with fomesafen applied at low rate with adjuvant or more 375 ga.i. • hm-2alone. Han et al. (2012) found that MSO adjuvant increased the maximum leaf retention of herbicide on weeds.

Abutilon

The control of fomesafen on abutilon was lower compared to the redroot pigweed with or without any adjuvant. The control was no more than 86.3% with all the fomesafen treatments (131.25-506.25 ga.i. • hm-2) alone recorded in Table 2.

Similarly, mixing MSO with fomesafen increased abutilon control. Fomesafen applied at the lowest rate (131.25 ga.i. • hm-2) alone provided 48.7%, and 53.3% stem control and 54.3% fresh weight control of abutilon for 14 DAT and 21 DAT. Addition of MSO in mixture of the lowest rate (131.25 ga.i. • hm-2) provided 62.0%, 65.7% stem control and 65.0% fresh weight control of abutilon for 14 DAT and 21 DAT, increased by 10.7%-13.3%. Fomesafen applied at rates (262.5, 375 and 506.25 ga.i. • hm-2) mixing with MSO adjuvant increased the control by 8.3%-11.0%, 12.7%-14.4% and 4.7%-5%, respectively.

The result in Table 2 suggested that fomesafen applied at rate of 506.25 ga.i. • hm-2alone and mixing with adjuvant, or at rate 375 ga.i. • hm-2mixing with adjuvant had better control of abutilon. Fomesafen applied at rate less than 262.5 ga.i. • hm-2could not have good control of the abutilon, regardless of adjuvant. Those indicated that the best abutilon control needed high fomesafen dose of more than 506.25 ga.i. • hm-2,or 375 ga.i. • hm-2mixing with adjuvant.

Black nightshade

Compared to the redroot pigweed and abutilon, the control of fomesafen on black nightshade was the lowest. Black nightshade control (＜75.7%) was recorded with all the fomesafen treatments (131.25-506.25 ga.i. • hm-2) alone in Table 3. Although mixing with MSO had effectively increased the fomesafen control of the black nightshade, and fomesafen applied at rate less than 375 ga.i. • hm-2with MSO adjuvant exhibited poor control of the black nightshade. Percent weed control below 80% was generally considered unacceptable (Nurse et al., 2008). Fomesafen applied at rate (506.25 ga.i. • hm-2) alone provided no more than 75.7% control of the black nightshade for 21 DAT. However, the rate (506.25 ga.i. • hm-2) applied with adjuvant control on black nightshade did not exceed 84.0%. This result suggested that black nightshade was most hard to control among the three weeds.

Table 2 Efficacy control of fomesafen with MSO adjuvant on abutilon

Table 3 Efficacy control of fomesafen with MSO adjuvant on black nightshade

Discussion

Chemical herbicide control is largely adopted for weed management around the world. Not all the herbicides have effective control to all the weeds, every weed has its susceptive herbicide. Fomesafen is a postemergence herbicide with high herbicidal activity,used for controlling broadleaf weeds in some broadleaf crops, such as soybean and peanut. Fomesafen had better control on redroot pigweed than abutilon and black nightshade in our present trial, indicating that redroot pigweed was the relatively susceptive weed to fomesafen, and black nightshade was hard to control with fomesafen. Similar results were recorded in other researches. Fomesafen applied at 200 ga.i. • hm-2provided poor control of the abutilon, cockerbur and Ahenopodium album, fomesafen applied at 300 ga.i. • hm-2only provided no more than 60% control of the abutilon, cockerbur and Chenopodium album (Gao et al., 2006). Mesotrione had the better control of the abutilon than redroot pigweed. Bentazon had better control of the cocklebur than black nightshade, strangler-vine and velvetleaf, and black nightshade was a smooth leaf surface weed that contained a high percentage of waxes hard to control with bentazon (Abouziena et al., 2009) .

Most herbicides always had worse control. Ways to increase herbicide activity for effective control of the weeds are very important, especially at lower rate. Adjuvant can increase herbicidal activity and modify environmental fate and solution characteristic. Adjuvant can reduce surface tension, decrease contact angle, reduce dry duration and augment leaf retention, therefore increase the herbicide control and decrease herbicide applied doses (Lu et al., 2004; Zhang and Zhang, 2011; Liu et al., 2013). Methylated soybean oil (MSO) adjuvant is one of the effective adjuvant with better synergistic effects to herbicide control of the weeds. As reported that MSO significantly increased sulcotrione activity by reduced contact angle and dry duration (Wang et al., 2003; Lu et al., 2004). MSO of SYP-G75 increased nicosulfuron, sethoxydim and fomesafen control of the abutilon, cockerbar (Gao et al., 2006). Quad7 and Scoil had the significant synergistic effects to nicosulfuron and fomesafen (Zhao et al., 2008; Han et al., 2012). Adjuvant was considered that improved uptake and translocation might contribute to lower herbicide activity.

Conclusions

The results suggested that adjuvant effectively increased herbicide control and had differences among weeds. Mixing MSO adjuvant with fomesafen generally enhanced the weed control. Redroot pigweed was more easily controlled with fomesafen at lower dose plus adjuvant than abutilon and black nightshade. Among the weeds, black nightshade with smooth leaf surface of the high waxes was hard to control with fomesafen, which needed higher dose or in combination with adjuvant to achieve the effective control. Addition of adjuvant could reduce the fomesafen dose in the practice application.

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TQ645; S482.4

A

1006-8104(2014)-03-0017-06

Received 18 March 2014

Supported by the Postdoctoral Grant of Heilongjiang Academy of Agricultural Sciences (LRB10-2446); the Doctoral Foundation of Northeast Agricultural University (2010RCB16); the Science and Technology Project of Heilongjiang Education Committee (12521034)

HanYu-jun (1981-), male, Ph. D, vice researcher, engaged in the research of herbicide applied technology. E-mail: hanyj920@163.com

* Corresponding author. Tao Bo, Ph. D, professor, engaged in the research of herbicide action principle and applied technology. E-mail: botaol@163. com.