Field-Evolved Sulfoxaflor Resistance of Three Wheat Aphid Species in China

Abstract

Sulfoxaflor belongs to a new class of insecticides which are effective against many sap-feeding pests. Sitobion miscanthi, Rhopalosiphum padi, and Metopolophium dirhodum are the predominant pests coexisting on wheat plants. It is unknown whether these aphid species have developed resistance to sulfoxaflor. Here, the susceptibilities of three wheat aphid species from different regions of China to sulfoxaflor were evaluated. The results showed that two S. miscanthi, one R. padi, and two M. dirhodum field populations were highly resistant to sulfoxaflor. Additionally, 13 S. miscanthi, 9 R. padi, and 4 M. dirhodum field populations were moderately resistant to sulfoxaflor. Analysis of differences in toxicity showed that the susceptibility levels of R. padi in 9 of 20 regions, M. dirhodum in 5 of 9 regions, and M. dirhodum in 3 of 9 regions to sulfoxaflor were greater than those of S. miscanthi, S. miscanthi, and R. padi in the same regions, respectively. Thus, each wheat aphid species has field populations that are highly sulfoxaflor resistant. The R. padi and M. dirhodum populations were more susceptible to sulfoxaflor than those of S. miscanthi. These findings provide new insights into insecticide resistance development and rational sulfoxaflor use.

1. Introduction

Sulfoxaflor, which belongs to a new class of insecticides (sulfoximines), is highly effective in controlling many kinds of sap-feeding pests [1,2,3]. Sulfoximines are unique among commercial insecticides in that they contain sulfoximine functional groups [2]. The target sites of sulfoxaflor are nicotinic acetylcholine receptors in the insect nervous system. The poisoned insects show abnormal excitement levels and then become paralyzed, resulting in death [1]. However, the chemical and biochemical properties of sulfoxaflor differ from those of other insecticides that target nicotinic acetylcholine receptors, including spinosyns, neonicotinoids, and nereistoxin analogs [3]. Therefore, sulfoxaflor has been selected for commercial development and may be useful for controlling many pests that have developed resistance to neonicotinoids and other insecticides [2,4,5,6]. In 2014, sulfoxaflor was registered in China as an important new option for controlling wheat aphids. To the best of our knowledge, this novel insecticide has not been used continuously over a prolonged period to control wheat aphids in most areas of China [7]. Furthermore, there are no reports of sulfoxaflor resistance in wheat aphids.

Sitobion miscanthi, Rhopalosiphum padi (Linnaeus), and Metopolophium dirhodum (Walker) are the major aphids (Hemiptera: Aphididae) that infest cereal crops. Both S. miscanthi and R. padi have been detected in all wheat fields in China [8,9]. In contrast, M. dirhodum is mainly distributed at high altitudes and in the northwestern regions of China [7]. These three wheat aphid species usually coexist on growing wheat plants. They can severely damage crops by feeding on plants or by acting as vectors for a variety of plant pathogenic viruses [10]. Global crop losses due to aphid infestations are estimated to be in the hundreds of millions of dollars per year [11]. In China, 10–15 million hectares are infested with cereal aphids, resulting in 10% yield losses annually [9,12,13]. In 2020, the National Agro-Tech Extension and Service Center of China released a report describing a 55.9% year-by-year increase in wheat aphid infestations.

Previous monitoring results revealed that most wheat aphid populations are still sensitive or exhibit low but gradually increasing resistance to various insecticides [14,15]. Recent studies confirmed that S. miscanthi, R. padi, and M. dirhodum field populations have developed resistance to many insecticides, including neonicotinoids (thiamethoxam and imidacloprid), pyrethroids (bifenthrin and beta-cypermethrin), macrolides (avermectin), and organophosphates (chlorpyrifos and omethoate) [7,8]. Regarding sulfoxaflor resistance, various Nilaparvata lugens and Aphis gossypii field populations with low resistance levels have been identified [16,17].

It is unknown whether wheat aphids have developed resistance to sulfoxaflor. Here, we evaluated the susceptibility of S. miscanthi, R. padi, and M. dirhodum field populations to sulfoxaflor. Specifically, a standard leaf-dipping bioassay was conducted to assess the sulfoxaflor resistance of 24 S. miscanthi, 24 R. padi, and 10 M. dirhodum field populations collected from different regions in China in 2019 and 2021. Additionally, the differences in the toxicity levels of sulfoxaflor between two wheat aphid species in the same area were calculated. The study results provide new insights into the mechanisms mediating the development of insecticide resistance as well as valuable information regarding the rational use of sulfoxaflor.

2. Materials and Methods

2.1. Insects and Insecticides

In 2019 and 2021, S. miscanthi, R. padi, and M. dirhodum field populations were collected from different wheat-producing areas in China (Figure 1, Table S1). The populations in each area were collected from at least three sites, with intervals of more than 10 km between sites. Sulfoxaflor (96%) was supplied by Hubei Kangbaotai Fine Chemicals Co., Ltd. (Wuhan, Hubei Province, China).

2.2. Bioassays

The toxicity of sulfoxaflor to aphids was determined using a leaf-based insecticide bioassay method [18]. The insecticide was prepared as a 1% stock solution using acetone. It was then diluted in water (containing 0.1% Tween-80) to produce five working solutions with different concentrations. Water (supplemented with 0.1% Tween-80) was used as the control solution. Wheat leaves containing apterous aphids were dipped in the working (or control) solution for 3–5 s and then placed in a Petri dish with a layer of wet filter paper on the bottom. The Petri dish was placed in an incubator at 20 ± 1 °C with a 16 h light/8 h dark photoperiod and 60–80% relative humidity. At least 30 aphids were treated at each concentration, with three replicates. Mortality was determined using a stereomicroscope after 24 h. Aphids were considered dead if they were unable to move after being touched with an anatomical needle.

2.3. Data Analysis

The slopes, 95% confidence limits, and median lethal concentrations (LC₅₀) were calculated using PoloPlus 2.00 (LeOra Software Inc., Petaluma, CA, USA). The relative resistance ratio (RLR) was calculated on the basis of the LC₅₀ for the most susceptible field population. Resistance levels were classified as follows: 5 < RLR ≤ 10 (low resistance); 10 < RLR ≤ 100 (moderate resistance); and RLR > 100 (high resistance).

The differences in sulfoxaflor toxicity levels between wheat aphid species (i.e., S. miscanthi and R. padi, S. miscanthi and M. dirhodum, and R. padi and M. dirhodum) in the same region were assessed by the 95% confidence intervals of median lethal concentrations ratio [LCR₅₀ (95%CIs)] [19] using PoloPlus 2.0. The LCR₅₀ (95%CIs) > 1 indicated that the latter species was more susceptible to sulfoxaflor than the former species. The LCR₅₀ (95%CIs) < 1 indicated that the latter species was less susceptible to sulfoxaflor than the former species. The inclusion of 1 in the LCR₅₀ (95%CIs) indicated that the susceptibility levels of the two species to sulfoxaflor were not significantly different.

3. Results

3.1. Susceptibility of S. miscanthi Field Populations to Sulfoxaflor

An examination of the susceptibility levels of 24 S. miscanthi field populations to sulfoxaflor (Table 1) identified HBL-2019 as the most susceptible field population (LC₅₀ = 2.28 mg/L; i.e., baseline value). The YNK-2019 and YNK-2021 field populations were highly resistant to sulfoxaflor (RLRs of 194.32 and 110.84, respectively). In total, 13 field populations (SXL-2019, SXY-2019, SXY-2021, HBX-2021, SDJ-2019, AHH-2019, IMH-2019, QHX-2019, HNZ-2019, XJK-2019, GZG-2021, HNX-2019, and NXY-2019) were moderately resistant to sulfoxaflor (RLRs of 10.27–56.18), whereas six field populations (GZG-2019, TJ-2019, SDQ-2019, HNX-2021, HBL-2021, and QHX-2021) exhibited low resistance to sulfoxaflor (RLRs of 5.52–9.75). Only three field populations (HBX-2019, AHH-2021, and HBL-2019) were not significantly resistant to sulfoxaflor (RLRs < 5).

3.2. Susceptibility of R. padi Field Populations to Sulfoxaflor

An analysis of the susceptibility levels of 24 R. padi field populations to sulfoxaflor (Table 2) revealed that JSY-2019 was the most susceptible field population (LC₅₀ = 2.53 mg/L; i.e., baseline value). In contrast, HNX-2021 was highly resistant to sulfoxaflor (RLR of 113.93). Nine field populations (IMH-2019, SDJ-2019, HBX-2021, XJK-2019, SXY-2019, QHX-2021, AHH-2021, AHH-2019, and GZG-2021) were moderately resistant to sulfoxaflor (RLRs of 10.39–40.98), whereas seven field populations (SXL-2019, SCM-2019, SXL-2021, TJ-2019, QHX-2019, SXY-2021, and HNZ-2019) exhibited low resistance to sulfoxaflor (RLRs of 5.02–9.38). Seven field populations (YNK-2019, HBL-2021, NXY-2019, XJI-2021, GZG-2019, HBX-2019, and JSY-2019) were not significantly resistant to sulfoxaflor (RLRs < 5).

3.3. Susceptibility of M. dirhodum Field Populations to Sulfoxaflor

An evaluation of the susceptibility levels of 10 M. dirhodum field populations to sulfoxaflor (Table 3) indicated that XJK-2019 was the most susceptible field population (LC₅₀ = 1.22 mg/L; i.e., baseline value). The XJI-2021 and SXL-2019 field populations were highly resistant to sulfoxaflor (RLRs of 206.26 and 101.45, respectively). Four field populations (SXY-2021, HBL-2019, SXY-2019, and NXY-2019) were moderately resistant to sulfoxaflor (RLRs of 11.89–68.74), whereas two field populations (GZG-2019 and QHX-2019) exhibited low resistance to sulfoxaflor (RLRs of 7.48 and 6.59, respectively). Two field populations (GZG-2021 and XJK-2019) were not significantly resistant to sulfoxaflor (RLRs < 5).

3.4. Differences in the Toxicity of Sulfoxaflor among Various Wheat Aphid Field Populations

Sitobion miscanthi and R. padi, S. miscanthi and M. dirhodum, and R. padi and M. dirhodum field populations simultaneously collected from 20, 9, and 9 regions, respectively, (Table S1) were used to assess the differences in sulfoxaflor toxicity between wheat aphid species. The analyzed differences in the toxicity levels of sulfoxaflor among various wheat aphid field populations, along with LCR₅₀ (95%CIs) values, are shown in Table S2. The susceptibility levels of S. miscanthi in 5 of 20 regions, S. miscanthi in 3 of 9 regions, and R. padi in 3 of 9 regions to sulfoxaflor were not significantly different compared with those of R. padi, M. dirhodum, and M. dirhodum in the same regions, respectively (Table 4). However, R. padi in 9 of 20 regions, M. dirhodum in 5 of 9 regions, and M. dirhodum in 3 of 9 regions were more susceptible to sulfoxaflor than S. miscanthi, S. miscanthi, and R. padi in the same regions, respectively (Table 4). In addition, R. padi in 6 of 20 regions, M. dirhodum in 1 of 9 regions, and M. dirhodum in 3 of 9 regions were less susceptible to sulfoxaflor than S. miscanthi, S. miscanthi, and R. padi in the same regions, respectively (Table 4). In summary, the R. padi and M. dirhodum field populations were more susceptible to sulfoxaflor than the S. miscanthi field populations.

4. Discussion

Pest control strategies primarily rely on the application of chemical insecticides. During the past 20 years, pesticides, such as pyrethroids, neonicotinoids, and organophosphates, have been widely used to control wheat aphids in the field [20]. However, wheat aphid field populations have become resistant owing to the extensive use of insecticides [8]. Insecticide resistance is increasingly becoming a problem that affects the sustainable production of important agricultural crops worldwide.

Sulfoxaflor is a new highly effective insecticide that has no known cross-resistance with other insecticides [2]. Accordingly, it can be used as a substitute for other pesticides in insecticide resistance management programs [2]. However, we detected two S. miscanthi, one R. padi, and two M. dirhodum field populations highly resistant to sulfoxaflor. Additionally, 13 S. miscanthi, 9 R. padi, and 4 M. dirhodum field populations were moderately resistant to sulfoxaflor. Another six S. miscanthi, seven R. padi, and two M. dirhodum field populations exhibited low-level resistance to sulfoxaflor. Earlier studies revealed the low-level sulfoxaflor resistance of N. lugens and A. gossypii field populations [16,17]. These sulfoxaflor-resistance findings present new challenges for the effective use of sulfoxaflor, with implications for the commercial value of this insecticide.

The high sulfoxaflor resistance of wheat aphid field populations may not be the result of long-term sulfoxaflor applications because, to the best of our knowledge, imidacloprid and omethoate were used to control wheat aphids in the YNK, HNX, and SXL regions, from 2013 to 2018. This sulfoxaflor resistance of wheat aphids may be related to unknown mechanisms of cross-resistance to imidacloprid or omethoate. Furthermore, insecticides were not applied on the XJI wheat fields. Thus, there may be other ways in which insects develop insecticide resistance. The ‘pre-adaptation hypothesis’ suggests that generalist herbivores are exposed to a greater variety of chemicals during evolution than specialists and that their ability to transport, isolate, and detoxify these compounds may have pre-adapted them to ‘novel’ xenobiotics (e.g., insecticides) [21]. Multiple studies have shown that endosymbiont bacteria influence host resistance to insecticides [22,23,24]. Hence, the biological mechanisms underlying the development of insecticide resistance and host plant adaptations during evolution may be the same [25]. Aphids are generalist herbivores and migratory insects. Whether the observed high-level sulfoxaflor resistance of wheat aphid field populations are related to cross-resistance, endosymbiont bacteria, the pre-adaptation hypothesis, or the migration of resistance genes remains to be determined. Nevertheless, the findings of this study provide new insights into how insects develop resistance to insecticides.

Insecticides can alter species interactions and competition. The resulting changes to the community structure may be favorable for potential secondary pest outbreaks [26]. Sitobion miscanthi, R. padi, and M. dirhodum feed on many of the same crops, including wheat, oats, and barley [12]. The diverse susceptibility levels of different wheat aphid species co-existing on wheat plants to the same insecticide are important factors to consider when developing effective chemical-based methods for controlling aphids. In a recent study on different aphid species collected in the same area, R. padi populations were more sensitive to imidacloprid, beta-cypermethrin, thiamethoxam, chlorpyrifos, and omethoate than Sitobion avenae populations, and S. avenae populations were more sensitive to avermectin and bifenthrin than R. padi populations [8]. In our study, R. padi and M. dirhodum were more susceptible to sulfoxaflor than S. miscanthi. These results suggest that the toxicity of the same insecticide to different wheat aphid species in a given region may vary. This difference will affect the efficacy of sulfoxaflor for controlling aphids in wheat fields.

The present study analyzed the field-evolved resistance of three wheat aphid species (S. miscanthi, R. padi, and M. dirhodum) to sulfoxaflor in various regions of China. The data presented may be relevant to the continued monitoring of wheat aphid insecticide resistance, with important implications for wheat production. Insecticide resistance risk assessments are critical for maintaining the efficacy of pest control measures. Therefore, wheat aphid resistance levels to insecticides in some regions must be carefully monitored. To extend the utility of sulfoxaflor, rotating applications of insecticides having different mechanisms on the basis of resistance monitoring results may be an effective strategy for preventing or delaying the development of wheat aphids resistant to sulfoxaflor.

Author Contributions

Conceptualization, X.Z. and L.W.; Methodology, X.L. (Xinan Li); Software, X.T.; Formal Analysis, X.L. (Xinan Li), H.G. and E.L.; Investigation, C.W., Q.L., S.Z. and X.T.; Writing—Original Draft Preparation, X.L. (Xinan Li); Writing—Review and Editing, Y.Z., X.L. (Xiangrui Li), X.Z. and L.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the China Agriculture Research System of MOF and MARA (CARS-3), the National Natural Science Foundation of China (Award number: 31772163), SINOGRAIN II (CHN-17/0019): Technological Innovation to Support Environmentally-Friendly, Food Production and Food Safety Under a Changing Climate Opportunities and Challenges for Norway-China Cooperation, Tianshan Young Talents (2019Q051), Research and Integrated Demonstration of Green Yielding and Quality Enhancement Technologies for Major Grain Crops in Xinjiang(2021B02002).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Most of the recorded data are provided in the tables.

Acknowledgments

We thank Liwen Bianji for editing the English text of a draft of this manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figure and Tables

Figure 1. Wheat aphid sampling regions in China. The sampling regions included Xining, Qinghai (QHX); Shizuishan, Ningxia Hui Autonomous Region (NXS); Hailar, Inner Mongolia Autonomous Region (IMH); Yangling, Shanxi (SXY); Linfen, Shanxi (SXL); Xiangyang, Hubei (HBX); Yangzhou, Jiangsu (JSY); Hefei, Anhui (AHH); Xinxiang, Henan (HNX); Zhumadian, Henan (HNZ); Qingdao, Shandong (SDQ); Jining, Shandong (SDJ); Kashgar Prefecture, Xinjiang Uygur Autonomous Region (XJK); Ili Kazak Autonomous Prefecture, Xinjiang Uygur Autonomous Region (XJI); Langfang, Hebei (HBL); Tianjin (TJ); Mianyang, Sichuan (SCM); Kunming, Yunnan (YNK); and Guiyang, Guizhou (GZG).

Table 1

Toxicity of sulfoxaflor to Sitobion miscanthi field populations.

No.	Code	N a	Slope ± SE b	LC50 c	95%CL d	χ2	RLR e
1	YNK-2019	574	0.49 ± 0.09	443.05	192.13–1717.55	1.26	194.32
2	YNK-2021	664	0.88 ± 0.08	252.72	179.64–355.16	0.48	110.84
3	SXL-2019	451	0.64 ± 0.08	128.10	76.02–235.77	1.52	56.18
4	SXY-2019	582	0.64 ± 0.07	81.76	25.75–289.65	5.82	35.86
5	SXY-2021	866	1.39 ± 0.09	75.81	38.34–149.07	8.91	33.25
6	HBX-2021	831	0.96 ± 0.07	60.94	46.31–79.29	1.61	26.73
7	SDJ-2019	664	1.28 ± 0.15	58.51	44.71–80.62	1.16	25.66
8	AHH-2019	607	0.79 ± 0.08	57.49	12.71–158.36	7.92	25.21
9	IMH-2019	634	0.77 ± 0.07	52.17	16.18–139.50	7.07	22.88
10	QHX-2019	595	0.82 ± 0.08	44.33	16.97–112.30	5.74	19.44
11	HNZ-2019	418	0.90 ± 0.10	37.34	10.95–140.16	7.02	16.38
12	XJK-2019	759	0.81 ± 0.08	32.27	21.07–46.93	1.29	14.15
13	GZG-2021	648	0.90 ± 0.07	29.18	8.93–66.24	7.39	12.8
14	HNX-2019	454	0.84 ± 0.09	28.83	18.85–43.35	2.42	12.64
15	NXY-2019	535	0.76 ± 0.08	23.42	15.13–34.78	2.27	10.27
16	GZG-2019	466	0.81 ± 0.08	22.24	11.27–42.62	3.43	9.75
17	TJ-2019	496	0.68 ± 0.09	16.40	9.2–26.70	1.19	7.19
18	SDQ-2019	552	0.69 ± 0.08	16.38	9.57–26.64	0.87	7.18
19	HNX-2021	805	0.66 ± 0.06	15.44	8.36–24.86	1.07	6.77
20	HBL-2021	555	0.84 ± 0.08	12.91	8.73–18.67	0.94	5.66
21	QHX-2021	700	1.11 ± 0.08	12.59	7.21–21.72	4.62	5.52
22	HBX-2019	575	0.56 ± 0.06	10.91	4.34–23.28	3.04	4.79
23	AHH-2021	797	0.62 ± 0.06	10.73	3.58–22.28	3.10	4.71
24	HBL-2019	332	0.53 ± 0.12	2.28	0.37–5.65	1.54	1

^a number of tested aphids. ^b standard error. ^c concentrations (mg/L) resulting in 50% dead or affected after 24 h. ^d 95% confidence limit of median lethal concentrations. ^e relative resistance ratio; 5 < RLR ≤ 10 (low resistance), 10 < RLR ≤ 100 (moderate resistance), and RLR > 100 (high resistance).

Table 2

Toxicity of sulfoxaflor to Rhopalosiphum padi field populations.

No.	Code	N a	Slope ± SE b	LC50 c	95%CL d	χ2	RLR e
1	HNX-2021	881	0.82 ± 0.06	288.24	164.09–506.74	4.28	113.93
2	IMH-2019	927	0.63 ± 0.06	103.68	44.12–315.22	5.88	40.98
3	SDJ-2019	854	0.82 ± 0.10	99.45	68.87–155.84	1.64	39.31
4	HBX-2021	964	0.54 ± 0.05	94.56	61.90–153.76	1.58	37.38
5	XJK-2019	662	0.86 ± 0.08	93.98	64.19–138.55	0.75	37.15
6	SXY-2019	732	0.60 ± 0.07	75.04	46.29–121.92	1.76	29.66
7	QHX-2021	890	1.40 ± 0.11	50.99	21.63–93.13	8.64	20.15
8	AHH-2021	670	1.28 ± 0.10	34.42	27.64–47.00	2.53	13.61
9	AHH-2019	754	0.87 ± 0.07	30.31	15.02–54.19	4.11	11.98
10	GZG-2021	807	1.054 ± 0.08	26.30	18.79–35.17	2.66	10.39
11	SXL-2019	666	0.65 ± 0.07	23.74	7.35–54.52	4.12	9.38
12	SCM-2019	656	0.75 ± 0.07	20.34	13.25–30.21	2.66	8.04
13	SXL-2021	935	1.62 ± 0.12	16.93	13.85–20.32	1.20	6.69
14	TJ-2019	629	0.74 ± 0.07	15.50	6.45–30.54	3.50	6.13
15	QHX-2019	676	0.62 ± 0.07	15.13	9.02–23.45	2.05	5.98
16	SXY-2021	820	1.13 ± 0.08	12.97	6.45–22.90	6.14	5.13
17	HNZ-2019	909	0.90 ± 0.06	12.69	4.26–30.11	10.35	5.02
18	YNK-2019	654	0.77 ± 0.07	12.22	5.07–25.24	4.99	4.83
19	HBL-2021	727	0.95 ± 0.08	9.86	6.51–14.03	1.71	3.9
20	NXY-2019	579	1.15 ± 0.11	6.74	4.60–9.20	1.26	2.66
21	XJI-2021	639	1.23 ± 0.12	4.98	3.31–6.91	0.36	1.97
22	GZG-2019	587	0.76 ± 0.08	4.22	0.57–11.52	6.48	1.67
23	HBX-2019	590	0.79 ± 0.09	3.75	1.91–6.19	1.08	1.48
24	JSY-2019	688	0.39 ± 0.07	2.53	0.44–6.83	0.07	1

^a number of tested aphids. ^b standard error. ^c concentrations (mg/L) resulting in 50% dead or affected after 24 h. ^d 95% confidence limit of median lethal concentrations. ^e relative resistance ratio; 5 < RLR ≤ 10 (low resistance), 10 < RLR ≤ 100 (moderate resistance), and RLR > 100 (high resistance).

Table 3

Toxicity of sulfoxaflor to Metopolophium dirhodum field populations.

No.	Code	N a	Slope ± SE b	LC50 c	95%CL d	χ2	RLR e
1	XJI-2021	652	0.60 ± 0.08	251.64	73.00–251.44	1.03	206.26
2	SXL-2019	663	0.60 ± 0.08	123.77	146.00–502.84	1.03	101.45
3	SXY-2021	594	0.74 ± 0.07	83.86	38.28–183.91	3.90	68.74
4	HBL-2019	864	1.36 ± 0.16	25.12	13.39–42.01	4.41	20.59
5	SXY-2019	685	0.51 ± 0.06	15.72	8.02–27.11	2.18	12.89
6	NXY-2019	696	0.88 ± 0.07	14.51	10.06–20.33	1.60	11.89
7	GZG-2019	586	0.78 ± 0.08	9.12	2.69–1.22	10.4	7.48
8	QHX-2019	493	0.70 ± 0.10	8.04	4.45–12.92	1.78	6.59
9	GZG-2021	751	1.05 ± 0.23	1.28	0.14–3.18	0.09	1.05
10	XJK-2019	579	0.44 ± 0.06	1.22	0.08–4.92	4.31	1

^a number of tested aphids. ^b standard error. ^c concentrations (mg/L) resulting in 50% dead or affected after 24 h. ^d 95% confidence limit of median lethal concentrations. ^e relative resistance ratio; 5 < RLR ≤ 10 (low resistance), 10 < RLR ≤ 100 (moderate resistance), and RLR > 100 (high resistance).

Table 4

The differences in sulfoxaflor toxicity between wheat aphid species.

Species	N a	ns b	+ c	− d
S. miscanthi/R. padi	20	5	9	6
S. miscanthi/M. dirhodum	9	3	5	1
R. padi/M. dirhodum	9	3	3	3

^a number of total field populations. ^b number of field populations showing no differences in sulfoxaflor toxicity between wheat aphid species. ^c number of field populations in which the latter species was more susceptible to sulfoxaflor than the former species. ^d number of field populations in which the latter species was less susceptible to sulfoxaflor than the former species.

Supplementary Materials

The following are available online at https://www.mdpi.com/article/10.3390/agronomy11112325/s1, Table S1: Wheat aphid sampling sites and collection dates. Table S2: Differences in the toxicity of sulfoxaflor among various wheat aphid field populations.

References

1. Zhu, Y.; Loso, M.R.; Watson, G.B.; Sparks, T.C.; Rogers, R.B.; Huang, J.X.; Gerwick, B.C.; Babcock, J.M.; Kelley, D.; Hegde, V.B. et al. Discovery and characterization of sulfoxaflor, a novel insecticide targeting sap-feeding pests. J. Agric. Food Chem.; 2011; 59, pp. 2950-2957. [DOI: https://dx.doi.org/10.1021/jf102765x] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/21105655]

2. Babcock, J.M.; Gerwick, C.B.; Huang, J.X.; Loso, M.R.; Nakamura, G.; Nolting, S.P.; Rogers, R.B.; Sparks, T.C.; Thomas, J.; Watson, G.B. et al. Biological characterization of sulfoxaflor, a novel insecticide. Pest Manag. Sci.; 2011; 67, pp. 328-334. [DOI: https://dx.doi.org/10.1002/ps.2069] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/21308958]

3. Sparks, T.C.; Watson, G.B.; Loso, M.R.; Geng, C.; Babcock, J.M.; Thomas, J.D. Sulfoxaflor and the sulfoximine insecticides: Chemistry, mode of action and basis for efficacy on resistant insects. Pestic. Biochem. Physiol.; 2013; 107, pp. 1-7. [DOI: https://dx.doi.org/10.1016/j.pestbp.2013.05.014] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/25149228]

4. Sparks, T.C.; DeBoer, G.J.; Wang, N.X.; Hasler, J.M.; Loso, M.R.; Watson, G.B. Differential metabolism of sulfoximine and neonicotinoid insecticides by Drosophila melanogaster monooxygenase CYP6G1. Pestic. Biochem. Physiol.; 2012; 103, pp. 159-165. [DOI: https://dx.doi.org/10.1016/j.pestbp.2012.05.006]

5. Gore, J.; Cook, D.; Catchot, A.; Leonard, B.R.; Stewart, S.D.; Lorenz, G.; Kerns, D. Cotton aphid (Heteroptera: Aphididae) susceptibility to commercial and experimental insecticides in the southern United States. J. Econ. Entomol.; 2013; 106, pp. 1430-1439. [DOI: https://dx.doi.org/10.1603/EC13116] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/23865211]

6. Longhurst, C.; Babcock, J.M.; Denholm, I.; Gorman, K.; Thomas, J.D.; Sparks, T.C. Cross-resistance relationships of the sulfoximine insecticide sulfoxaflor with neonicotinoids and other insecticides in the whiteflies Bemisia tabaci and Trialeurodes vaporariorum. Pest Manag. Sci.; 2013; 69, pp. 809-813. [DOI: https://dx.doi.org/10.1002/ps.3439] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/23203347]

7. Gong, P.; Li, X.; Wang, C.; Zhu, S.; Li, Q.; Zhang, Y.; Li, X.; Li, G.; Liu, E.; Gao, H. et al. The Sensitivity of Field Populations of Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) to Seven Insecticides in Northern China. Agronomy; 2021; 11, 1556. [DOI: https://dx.doi.org/10.3390/agronomy11081556]

8. Gong, P.; Li, X.; Gao, H.; Wang, C.; Li, M.; Zhang, Y.; Li, X.; Liu, E.; Zhu, X. Field evolved resistance to pyrethroids, neonicotinoids, organophosphates and macrolides in Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) from China. Chemosphere; 2021; 269, 128747. [DOI: https://dx.doi.org/10.1016/j.chemosphere.2020.128747] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33172670]

9. Lu, Y.; Gao, X. Multiple mechanisms responsible for differential susceptibilities of Sitobion avenae (Fabricius) and Rhopalosiphum padi (Linnaeus) to pirimicarb. Bull. Entomol. Res.; 2009; 99, pp. 611-617. [DOI: https://dx.doi.org/10.1017/S0007485309006725]

10. Lu, Y.H.; He, Y.P.; Gao, X.W. Comparative studies on acetylcholinesterase characteristics between the aphids, Sitobion avenae and Rhopalosiphum padi. J. Insect Sci.; 2013; 13, pp. 1-9. [DOI: https://dx.doi.org/10.1673/031.013.0901] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/23879406]

11. Yan, T.; Chen, H.; Sun, Y.; Yu, X.; Xia, L. RNA Interference of the Ecdysone Receptor Genes EcR and USP in Grain Aphid (Sitobion avenae F.) Affects Its Survival and Fecundity upon Feeding on Wheat Plants. Int. J. Mol. Sci.; 2016; 17, 2098. [DOI: https://dx.doi.org/10.3390/ijms17122098]

12. Xiao, D.; Yang, T.; Desneux, N.; Han, P.; Gao, X. Assessment of Sublethal and Transgenerational Effects of Pirimicarb on the Wheat Aphids Rhopalosiphum padi and Sitobion avenae. PLoS ONE; 2015; 10, e0128936. [DOI: https://dx.doi.org/10.1371/journal.pone.0128936]

13. Hu, X.S.; Liu, Y.J.; Wang, Y.H.; Wang, Z.; Yu, X.L.; Wang, B.; Zhang, G.S.; Liu, X.F.; Hu, Z.Q.; Zhao, H.Y. et al. Resistance of wheat accessions to the English grain aphid Sitobion avenae. PLoS ONE; 2016; 11, e0156158. [DOI: https://dx.doi.org/10.1371/journal.pone.0156158] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/27249206]

14. Zuo, Y.; Wang, K.; Zhang, M.; Peng, X.; Piñero, J.C.; Chen, M. Regional Susceptibilities of Rhopalosiphum padi(Hemiptera: Aphididae) to Ten Insecticides. Fla. Entomol.; 2016; 99, pp. 269-275. [DOI: https://dx.doi.org/10.1653/024.099.0217]

15. Zhang, L.; Lu, H.; Guo, K.; Yao, S.; Cui, F. Insecticide resistance status and detoxification enzymes of wheat aphids Sitobion avenae and Rhopalosiphum padi. Sci. China Life Sci.; 2017; 60, pp. 927-930. [DOI: https://dx.doi.org/10.1007/s11427-017-9105-x] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/28755297]

16. Liao, X.; Mao, K.; Ali, E.; Zhang, X.; Wan, H.; Li, J. Temporal variability and resistance correlation of sulfoxaflor susceptibility among Chinese populations of the brown planthopper Nilaparvata lugens (Stål). Crop Protect.; 2017; 102, pp. 141-146. [DOI: https://dx.doi.org/10.1016/j.cropro.2017.08.024]

17. Ma, K.; Tang, Q.; Xia, J.; Lv, N.; Gao, X. Fitness costs of sulfoxaflor resistance in the cotton aphid, Aphis gossypii Glover. Pestic. Biochem. Physiol.; 2019; 158, pp. 40-46. [DOI: https://dx.doi.org/10.1016/j.pestbp.2019.04.009] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31378359]

18. Gong, P.; Chen, D.; Wang, C.; Li, M.; Li, X.; Zhang, Y.; Li, X.; Zhu, X. Susceptibility of Four Species of Aphids in Wheat to Seven Insecticides and Its Relationship to Detoxifying Enzymes. Front. Physiol.; 2020; 11, 623612. [DOI: https://dx.doi.org/10.3389/fphys.2020.623612] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33536942]

19. Wheeler, M.W.; Park, R.M.; Bailey, A.J. Comparing median lethal concentration values using confidence interval overlap or ratio tests. Environ. Toxic. Chem.; 2006; 25, pp. 1441-1444. [DOI: https://dx.doi.org/10.1897/05-320R.1] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/16704080]

20. Deng, J. The Detection and Midgut Intracellular Location of Rickettsia Symbiont in the Camellia Aphid (Aphis aurantii). Appl. Ecol. Environ. Res.; 2019; 17, pp. 12203-12212. [DOI: https://dx.doi.org/10.15666/aeer/1705_1220312212]

21. Rosenheim, J.A.; Johnson, M.W.; Mau, R.F.L.; Welter, S.C.; Tabashnik, B.E. Biochemical Peradaptations, Founder Events, and the Evolution of Resistance in Arthropods. J. Econ. Entomol.; 1996; 89, pp. 263-273. [DOI: https://dx.doi.org/10.1093/jee/89.2.263]

22. Li, Q.; Sun, J.; Qin, Y.; Fan, J.; Zhang, Y.; Tan, X.; Hou, M.; Chen, J. Reduced insecticide susceptibility of the wheat aphid Sitobion miscanthi after infection by the secondary bacterial symbiont Hamiltonella defensa. Pest Manag. Sci.; 2021; 77, pp. 1936-1944. [DOI: https://dx.doi.org/10.1002/ps.6221] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33300163]

23. Cai, T.; Zhang, Y.; Liu, Y.; Deng, X.; He, S.; Li, J.; Wan, H. Wolbachia enhances expression of NlCYP4CE1 in Nilaparvata lugens in response to imidacloprid stress. Insect Sci.; 2021; 28, pp. 355-362. [DOI: https://dx.doi.org/10.1111/1744-7917.12834]

24. Zhang, Y.; Cai, T.; Ren, Z.; Liu, Y.; Yuan, M.; Cai, Y.; Yu, C.; Shu, R.; He, S.; Li, J. et al. Decline in symbiont-dependent host detoxification metabolism contributes to increased insecticide susceptibility of insects under high temperature. ISME. J.; 2021; [DOI: https://dx.doi.org/10.1038/s41396-021-01046-1] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/34188180]

25. Dermauw, W.; Pym, A.; Bass, C.; Van Leeuwen, T.; Feyereisen, R. Does host plant adaptation lead to pesticide resistance in generalist herbivores?. Curr. Opin. Insect Sci.; 2018; 26, pp. 25-33. [DOI: https://dx.doi.org/10.1016/j.cois.2018.01.001] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/29764657]

26. Mohammed, A.; Desneux, N.; Monticelli, L.S.; Fan, Y.; Shi, X.; Guedes, R.N.C.; Gao, X. Potential for insecticide-mediated shift in ecological dominance between two competing aphid species. Chemosphere; 2019; 226, pp. 651-658. [DOI: https://dx.doi.org/10.1016/j.chemosphere.2019.03.114]