Neonicotinoid pesticide applications affect pollinator abundance and visitation, leading to implications for sunflower production (Helianthus annuus L.)

Abstract

Pesticides are considered a risk to pollinators; however, little is known about the possible effects of their injudicious use on pollinators, including the ecosystem services provided to crops and wildflowers. Recently, great attention has been paid to the effects of neonicotinoids pesticides on pollinators and their potential role in harming the health of bees all over the world. Sunflowers, being self-incompatible plants, rely on insects, primarily bees, for effective cross-pollination and successful seed-set. Ensuring the presence of sufficient pollinators in the field is crucial for facilitating pollen movement between flowers and promoting optimal seed development. However, the reliance on insect-mediated cross-pollination also makes sunflowers susceptible to pest attacks, which can negatively impact seed production. To mitigate these potential threats and achieve increased seed yields, careful consideration is given to the judicious use of pesticides. Striking the right balance between providing adequate pollinators and implementing appropriate pest management strategies is vital for maximizing sunflower crop productivity. To reveal such potential impacts of neonicotinoid insecticides, we undergo the current study that aimed to estimate flower visitation and pollination in a sunflower crop by applying three neonicotinoid insecticides i.e. imidacloprid, clothianidin, and thiamethoxam, including the control group for two years i.e. 2020, and 2021. In all experimental plots, we quantified floral visitors for fourteen days at three different times (8 am, 12 pm, and 5 pm). Floral visitors were divided into three groups, Apis bees, Non-Apis bees, and butterflies. After the maturation period, the achenes from each capitulum were separated and brought for weight. We discovered that this study confirmed the adverse effect of neonicotinoids pesticides on sunflower production.

Our research revealed that the use of imidacloprid, clothianidin, and thiamethoxam had a negative impact on the visitation of Apis bees, with reductions of 19%, 18.5%, and 23% respectively, as compared to the control group during the year 2020. Furthermore, these pesticides also caused a decrease in the visitation of Non-Apis bees by 15%, 15%, and 17% respectively. The visitation of butterflies was also affected, with reductions of 17.4%, 14.6%, and 15.8% for imidacloprid, clothianidin, and thiamethoxam respectively. Based on our research conducted in the year 2021, the use of imidacloprid, clothianidin, and thiamethoxam caused a reduction of 22.5%, 24%, and 25.5% respectively in the visitation of Apis bees, as compared to the control group. Similarly, non-Apis bees experienced a decrease in visitation by 19.5%, 23.5%, and 25% respectively for imidacloprid, clothianidin, and thiamethoxam, compared to the control group. The visitation of butterflies was also affected, with reductions of 18.2%, 22.2%, and 26% respectively for imidacloprid, clothianidin, and thiamethoxam, compared to the control group. Our findings suggest that the use of these pesticides affected the diversity of floral visitors and contributed to a decline in the number of fruit during the year 2020 and 2021.

Moreover, the abundance of floral visitors, the mass of fruits, and the quantity of oil in the seeds were significantly lower after treatment with neonicotinoid pesticides, thus evidencing its negative effect on sunflower productivity.

Keywords:

• Sunflower
• Abundance
• Pollinators
• Neonicotinoids
• Pesticide toxicity
• Productivity

Public Interest Statement

Our research sheds light on the potential impacts of neonicotinoid pesticides, commonly used in agriculture, on the pollination process and productivity of sunflower crops. Sunflowers heavily rely on pollinators, such as bees and butterflies, for successful flower visitation and fruit production. Through comprehensive field studies, we found that the use of neonicotinoid pesticides—specifically imidacloprid, clothianidin, and thiamethoxam—resulted in a significant reduction in the visitation of both Apis and non-Apis bees, as well as butterflies.

The negative effects were observed in terms of decreased flower visitation, lower fruit mass, and reduced oil quantity in sunflower seeds. These findings raise concerns about the potential harm inflicted on pollinator populations and the subsequent impact on crop productivity. Our research emphasizes the need for responsible pesticide use and highlights the importance of protecting pollinators for the overall health and sustainability of agricultural ecosystems.

1. Introduction

Pollination is a vital ecological function that not only fascinates humans but also plays a crucial role in the survival of the Earth’s terrestrial ecosystems. Without pollinators, humanity would not be able to survive. Fundamentally, all of the world’s seed plants rely on pollination. According to a study, nearly 75% of the world’s major crop species need pollinators for fruit and seed production (Klein et al., 2007). Bees, with their variability and population abundance, are particularly beneficial for crop production (Garibaldi et al., 2013). Honeybees are considered as one of the most popular pollinators among all insect pollinators, and most effective crop visitor globally (Garantonakis et al., 2016; Hung et al., 2018). However, the significance of other insect pollinators should not be underestimated. These insects play a crucial role in enhancing and stabilizing crop pollination, relying on these plants for their pollen and nectar supply (Mallinger et al., 2019; Rader et al., 2016). Among the key groups of other insect pollinators are butterflies, moths, some flies, and beetles (Jacques et al., 2017). In fact, out of 124 crops worldwide, 87 of the major crops used for human consumption depend entirely on insect pollination (Williams, 1994). The contribution of wild bees is also of significant importance to a wide range of crop ecosystems (Greenleaf & Kremen, 2006; Kremen et al., 2002; Morandin & Winston, 2005). Many farmers in various countries purchase pollinators such as honeybees, bumblebees, and others to pollinate their crops (Dag et al., 2006; Free, 1993; McGregor, 1976; Olmstead & Wooten, 1987). According to estimates by Losey and Vaughn (2006), wild pollination services in the United States contribute around $3 billion per year. Globally, approximately 73% of cultivated crops depend on pollination, with bees accounting for 56.5%, flies for 19%, bats for 6.5%, beetles for 5%, birds for 4%, and butterflies and moths for 4% (Shaheen et al., 2017). There are over 25,000 distinct bee species, varying in size and habit, that play a crucial role in pollinating different plants and crops.

Sunflowers are often visited by Apis bee pollinators, with Apis mellifera being the most effective at pollinating sunflowers (Kumar & Singh, 2005; Nderitu et al., 2008). Insects, particularly bees, play a vital role in enhancing the yield of sunflowers through pollination. Studies reveal that Apis sp. contribute significantly, accounting for 88.85% of the relative abundance of sunflower’s capitula insect visitors (Jadhav et al., 2011). Honeybees, in particular, are essential for achieving maximum sunflower seed production (Oz et al., 2009; Tan et al., 2002). In Pakistan, the production of edible oil involves the cultivation of both conventional and non-conventional oilseed crops. Among the conventional oilseed crops are cotton, mustard, rapeseed, sesame, and groundnuts, which have been traditionally cultivated for this purpose. In contrast, sunflowers, safflowers, and soybeans are considered non-conventional crops, introduced during the green revolution that commenced in the 1960s (Badar, 2000). Sunflowers (Helianthus annuus L.), belonging to the Asteraceae family, are an important oilseed crop, ranking fourth in production. The crop is primarily grown for seed production, with spring and summer being the most suitable growing seasons in Pakistan (Shah et al., 2013). Pakistan produced 141 million tons of sunflower seeds in 2021–2022, yielding 54 million tons of oil on a cultivation area of 253,000 acres. In contrast, in 2018–19, Pakistan imported around 2.754 million tons of edible oil valued at Rs. 662.6 billion (US$ 3.68 billion) (Pakistan Economic Survey, 2021–22; Pakistan Oilseed Development Board (PODB); Pakistan Bureau of Statistics).

The relationship between pollinator abundance and richness indicates that a higher number of pollinators leads to increased number of seeds (Steffan-Dewenter, 2003), while a shortage of pollinators can result in a significant reduction in fruit and seed production (Partap, 2001). The global decline in pollinator abundance and diversity has been attributed to human-induced climate and habitat changes, leading to a decrease in the biodiversity of many pollinator families (Biesmeijer et al., 2006).

The use of pesticides can be detrimental to the ecosystem, particularly for beneficial species (Damalas, 2009; Damalas & Eleftherohorinos, 2011), and can cause water and soil pollution in crop areas, affecting beekeeping and pollinators due to the depletion of agrochemicals (Botías et al., 2016; Desneux et al., 2007; Goulson & Kleijn, 2013; Henry et al., 2012; Sanchez-Bayo, 2014; Schaafsma et al., 2015). Neonicotinoid pesticides are a group of pesticides that have received public attention because of their potential role in honey bee colony loss (Jensen, 2015; Van der Sluijs et al., 2013). These chemicals are neurotoxins that are structurally similar to nicotine (Tomizawa & Casida, 2005; Tomizawa et al., 2000) and are agonists of the nicotinic acetylcholine receptor (nAChR) in insects. Therefore, exposure or oral administration of lethal concentrations of these pesticides can cause infinite action potentials, paralysis of insect neurons and ultimately lead to insect death (Belzunces et al., 2012). The lethal and sublethal effects of neonicotinoid pesticides on individual bees and populations have been observed in laboratory and field experiments (Ladurner et al., 2005; Mommaerts et al., 2010; Pettis et al., 2013; Whitehorn et al., 2012). As sunflowers heavily depend on pollinators for seed production, this study aimed to investigate the impact of neonicotinoid pesticides on the richness and abundance of floral visitors and its consequent effects on sunflower productivity.

2. Materials and Methods

The experimental field of the Department of Agriculture and Agribusiness Management, University of Karachi (24°56’45.9“N 67°07’16.8“E), was selected as the location for the study. The experiment was conducted during 2020 and 2021 in a sunflower crop using a Randomized Complete Block Design (RCBD) to ensure accurate and unbiased results (Supplementary Figure S1). For our plantation, we chose Hysun-33 (Advanta Seeds), a commercially available sunflower variety. This hybrid variety is ideal as it has medium maturity, high oil content, medium height, and excellent lodging resistance. Hysun-33 is versatile, with wider adaptability, heat and drought tolerance, and produces excellent grain filling and weight. It can be sown in both spring and autumn seasons, making it a convenient choice for farmers. We spaced each row 70 cm apart, while the distance between each plant was 45 cm. Once the seedlings had developed, we thinned them out to ensure that each plot had an appropriate average plant population in order to prevent any run-off. To ensure the experiment was conducted under optimal conditions, all recommended agronomic practices were carried out during the study. The experimental area was divided into plots, each covering a 40 square meter area (10 meters long x 4 meters wide) with a 2-meter buffer. The study was comprised of four treatments, each of which was replicated three times.

The recommended doses of neonicotinoid insecticides i.e., imidacloprid @ 2.47 g/L, clothianidin @ 24.7 g/L, and thiamethoxam @ 19.76 g/L (Supplementary Table S1) were applied before and during the inflorescence at the interval of 15 days. Control treatment was rendered without the use of insecticides, however other physical and mechanical control methods were practiced.

We conducted insecticide application using a handheld sprayer equipped with a pressure chamber, with a capacity of 3.5 liters. The water utilized in the sprayer had a pH level ranging from 6.9 to 7.3. To ensure that the insecticide was only applied to the intended areas, we scheduled our applications before 7 am or after 5 pm on days with low wind speeds. This helped prevent the product from drifting to the control plot.

We conducted regular inspections of each experimental plot, carefully observing and recording data on each plant. Our focus was on monitoring any insect infestations, which we eradicated manually by capturing and removing the insects. We also noted the number of plants affected in our data files. We made observations at three different times − 8 am, 12 noon, and 5 pm—simultaneously in all experimental plots for 14 days. During this time, we identified and registered the visitors to the flowers. To do this, we selected 10 inflorescences and devoted a total of 20 minutes of effort per plot. Each inflorescence was observed for 2 minutes. We categorized floral visitors into three groups; Apis bees, Non-Apis bees, and Butterflies.

Following the maturation period, the capitulums were collected and removed from the stem and left in their experimental plots to be dried. From each capitulum, the achenes were separated and taken to weight.

3. Data analysis

The collected data were administered to statistical analysis through analysis of variance by using SPSS Version 16.0. One-way ANOVA was conducted to compare the effects of three different neonicotinoid insecticides: imidacloprid, clothianidin and thiamethoxam at recommended doses on the sunflower crop to observe the changes on abundance of pollinators’ floral visitation.

Significant differences among various treatment means were tested with Tukeys’ HSD test using 5% significant level along with multiple comparison. For the assessment of homogeneity of variances, we used the levene’s test.

4. Results

4.1. Abundance of floral visitors during 2020

During the year 2020, a total of 7667 visits were observed in the control plots. However, among the treated plots, 3082 visits occurred in the imidacloprid treated plots, 2881 visits were in clothianidin treated plots, and 3489 visits were in thiamethoxam treated plots. The highest number of visits in the control plots were presented by Apis mellifera, followed by Apis florea and Xylocopa sarawakensis, as shown in Table 1.

Table 1. The table presents the (mean and SD) of the percentage of different floral visitor groups (Apis bees, non-Apis bees, and butterflies) observed on sunflower crops during the flowering period in 2020, both on treated and untreated crops

Group	Taxa/Insect Name	Imidacloprid	Clothianidin	Thiamethoxam	Control
Apis Bees	Apis mellifera	9.03 ± 4.42^c	8.75 ± 3.35^c	12.63 ± 6.61^c	18.0 ± 8.57^d
	Apis florea	7.54 ± 4.36^b	7.06 ± 3.90^b	7.34 ± 3.58^b	14.70 ± 7.28^c
Non-Apis Bees	Xylocopa violacea	1.58 ± 1.06^a	1.93 ± 1.28^a	2.39 ± 1.89^a	7.05 ± 4.43^b
	Xylocopa sarawakensis	2.51 ± 2.55^a	1.91 ± 1.63^a	2.31 ± 1.94^a	7.56 ± 3.46^b
Butterflies	Danaus chrysippus	1.44 ± 1.42^a	1.55 ± 1.46^a	1.35 ± 1.18^a	3.94 ± 2.80^a
	Eurema blanda	1.56 ± 1.24^a	0.62 ± 0.91^a	1.59 ± 2.89^a	3.55 ± 1.72^a
	Colotis etrida	1.25 ± 0.92^a	1.12 ± 0.98^a	1.38 ± 1.06^a	3.76 ± 1.65^a
	Colotis danae	1.00 ± 1.19^a	0.72 ± 0.80^a	0.82 ± 0.88^a	3.08 ± 1.91^a
	Colias alpheraky	0.99 ± 1.09^a	0.86 ± 0.90^a	0.66 ± 1.03^a	4.33 ± 3.42^a

Within a column, the means pursued by the same letter are not significantly different (Tukey’s HSD test, α = 0.05).

For the imidacloprid application, an analysis of variance was conducted to investigate its effect on pollinator visitation. The results indicated a significant effect, with F (8, 342) = 61.587 and P < 0.001. A post hoc Tukey test was performed, which revealed a significant difference (p < 0.05) between the Apis bees’ group and non-apis bees. Similarly, for the clothianidin treatment, an analysis of variance was conducted, which also showed a significant effect on pollinator visitation, with F (8, 342) = 84.545 and P < 0.001. A post hoc Tukey test indicated a significant difference (p < 0.05) between Apis mellifera bees and Apis florea bees, while these two were statistically different from other non-apis pollinators with p > 0.05. Lastly, for the thiamethoxam application, an analysis of variance was performed, revealing a significant effect on floral visitor visitation, with F (8, 342) = 73.507 and P < 0.001. A post hoc Tukey test showed a significant difference (p < 0.05) between Apis mellifera bees and Apis florea bees, while these two were statistically different from other non-apis pollinators with p > 0.05, as shown in Figure 1(a) and Table 2 & 3.

Figure 1. Floral visitor abundance in sunflower crops treated with neonicotinoids and without pesticide (Control).

Table 2. The table presents the (mean and SD) of the percentage of different floral visitor groups (Apis bees, non-Apis bees, and butterflies) observed on sunflower crops during the flowering period in 2021, both on treated and untreated crops

Group	Taxa/Insect Name	Imidacloprid	Clothianidin	Thiamethoxam	Control
Apis Bees	Apis mellifera	11.8 ± 6.6^b	12.8 ± 7.2^c	13.6 ± 7.9^c	15.5 ± 9.11^c
	Apis florea	9.5 ± 6.5^b	9.9 ± 6.6^b	10.2 ± 6.6^b	11.7 ± 9.1^b
Non-Apis Bees	Xylocopa violacea	2.2 ± 1.7^a	2.5 ± 1.9^a	2.6 ± 2.0^a	3.0 ± 2.2^a
	Xylocopa sarawakensis	0.80 ± 0.8^a	0.99 ± 1.0^a	1.0 ± 1.1^a	1.5 ± 1.5^a
Butterflies	Danaus chrysippus	0.49 ± 0.51^a	0.57 ± 0.56^a	0.67 ± 0.56^a	0.88 ± 0.62^a
	Eurema blanda	0.52 ± 0.46^a	0.62 ± 0.58^a	0.69 ± 0.62^a	0.84 ± 0.69^a
	Colotis etrida	0.36 ± 0.33^a	0.49 ± 0.43^a	0.58 ± 0.51^a	0.67 ± 0.57^a
	Colotis danae	0.21 ± 0.24^a	0.30 ± 0.34^a	0.36 ± 0.41^a	0.51 ± 0.54^a
	Colias alpheraky	0.14 ± 0.18^a	0.15 ± 0.21^a	0.17 ± 0.27^a	0.26 ± 0.35^a

Within a column, the means pursued by the same letter are not significantly different (Tukey’s HSD test, α = 0.05).

Table 3. Abundance and richness of Apis, non-Apis and butterflies in sunflower crops treated with neonicotinoids and without neonicotinoids (Year 2020)

Group	Taxa/Insect Name	Without Pesticides (WOP)Control		Imidacloprid			Clothianidin			Thiamethoxam
		Total	Percent	Total	Percent	Percent Decrease	Total	Percent	Percent Decrease	Total	Percent	Percent Decrease
Apis Bees	Apis mellifera	2111	27.5%	1033	33.52%	51.07%	997	34.6%	52.77%	1448	41.5%	31.41%
	Apis florea	1720	22.4%	875	28.39%	49.13%	825	28.6%	52.03%	850	24.4%	50.58%
Non-Apis Bees	Xylocopa Violacea	817	10.7%	189	6.13%	76.87%	226	7.8%	7234%	268	7.7%	67.20%
	Xylocopa Sarawakensis	879	11.5%	276	8.96%	68.60%	226	7.8%	74.29%	268	7.7%	69.51%
Butterflies	Danaus chrysippus	452	5.9%	168	5.45%	62.83%	178	6.2%	60.62%	156	4.5%	65.49%
	Eurema blanda	405	5.3%	174	5.65%	57.04%	135	4.7%	66.67%	177	5.1%	56.30%
	Colotis etrida	432	5.6%	142	4.61%	67.13%	117	4.1%	72.92%	157	4.5%	63.66%
	Colotis danae	357	4.7%	113	3.67%	68.35%	84	2.9%	76.47%	95	2.7%	73.39%
	Colias alpheraky	494	6.4%	112	3.63%	77.33%	93	3.2%	81.17%	70	2.0%	85.83%
	Total	7667	100%	3082	100%	-	2881	100%	-	3489	100%	-

Notably, the analysis of variance in the control plots also indicated a significant effect on pollinator visitation, with F _{(8, 342)} = 55.008 and P < 0.001, as shown in Figure 1(a) and Tables 2 & 1. A multiple comparison test revealed that Apis mellifera bees differed significantly (p < .05) from Apis florea bees. Similarly, both of these were statistically different from other non-Apis pollinators with p > 0.05. Overall, these findings suggest that all three neonicotinoids have a considerable impact on pollinator visitation.

5. Abundance of floral visitors during 2021

During the year 2021, a total of 4019 visits were observed in the control plots alone, with Apis mellifera recording the highest number of visits, followed by Apis florea and Xylocopa violacea, as shown in Table 3. When looking at the treated plots, there were 3047 visits in imidacloprid plots, 3311 in clothianidin plots, and 3508 in thiamethoxam plots.

The analysis conducted on the impact of imidacloprid application on pollinator visitation revealed a significant effect (F _{(8, 333)} = 75.805, P < 0.001) as compared to the control group. The post-hoc Tukey test further showed that the Apis bees’ group differed significantly (p < 0.05) from non-Apis bees. Similarly, the clothianidin treatment also showed a significant effect on pollinator visitation (F _{(8, 333)} = 75.671, P < 0.001), with a significant difference (p < 0.05) observed in the Apis mellifera bees’ visitation as compared to Apis florea. In the case of thiamethoxam application, a significant effect on floral visitor visitation was also observed (F _{(8, 333)} = 74.951, P < 0.001), with Apis mellifera bees differing significantly (p < 0.05) from Apis florea bees. Both these groups were also statistically different from other non-Apis pollinators with p > 0.05, as shown in Figure 1(b) and Tables 4 & 3.

Table 4. Abundance and richness of Apis, non-Apis and butterflies in sunflower crops treated with neonicotinoids and without neonicotinoids (Year 2021)

Groups	Taxa/Insect Name	Without Pesticides (WOP)Control		Imidacloprid			Clothianidin			Thiamethoxam
		Total	Percent	Total	Percent	Percent Decrease	Total	Percent	Percent Decrease	Total	Percent	Percent Decrease
Apis Bees	Apis mellifera	1762	43.84%	1384	45.42%	12.40%	1504	45.42%	7.79%	1600	45.61%	4.61%
	Apis florea	1375	34.21%	1123	36.85%	8.27%	1159	35%	6.52%	1201	34.23%	4.96%
Non-Apis Bees	Xylocopa Violacea	353	8.78%	252	8.27%	3.31%	293	8.84%	1.81%	303	8.63%	1.42%
	Xylocopa Sarawakensis	171	4.25%	92	3.01%	2.59%	113	3.41%	1.75%	123	3.50%	1.36%
Butterflies	Danaus chrysippus	101	2.51%	56	1.83%	1.47%	66	2%	1.05%	77	2.19%	0.68%
	Eurema blanda	91	2.26%	57	1.87%	1.11%	67	2.02%	0.72%	75	2.13%	0.45%
	Colotis etrida	77	1.91%	42	1.37%	1.14%	56	1.69%	0.63%	67	1.90%	0.28%
	Colotis danae	59	1.46%	25	0.82%	1.11%	35	1.05%	0.72%	42	1.19%	0.48%
	Colias alpheraky	30	0.74%	16	0.52%	0.45%	18	0.54%	0.36%	20	0.57%	0.28%
	Total	4019	100%	3047	100%	-	3311	100%	-	3508	100%	-

Within a column, the means pursued by the same letter are not significantly different (Tukey’s HSD test, α = 0.05).

In the control group, there was also a significant effect on pollinator visitation (F _{(8, 333)} = 70.146, P < 0.001), with Apis mellifera bees differing significantly (p < .05) from Apis florea. Similarly, these two groups were also statistically different from other non-Apis pollinators with p > 0.05, as shown in Figure 1(b) and Tables 4 & 3. Overall, all three neonicotinoids have a considerable impact on pollinator visitation, leading to a reduction in the population of pollinators in the year 2021 as compared to 2020.

6. Comparison of Yield

We observed significant differences in the yield (during 2020) between the neonicotinoids treated and control groups F _{(3, 8)} = 1.39, P < 0.001 (5.72 kg/plot). The average yield was approximately (M = 1.34, SD = 46.3; 4.16 kg/plot), (M = 1.21, SD = 58.4; 4.85 kg/plot) and (M = 1.17, SD = 99.0; 4.69 kg/plot), higher in control group as compared to imidacloprid, clothianidin and thiamethoxam respectively, as shown in Figure 2.

Figure 2. The average yield (kg/plot) of crops treated with neonicotinoids (imidacloprid, clothianidin, and thiamethoxam) compared to the control group in 2020 and 2021. The graph shows a significant difference in yield between the treated and control groups in both years, with the control group consistently yielding higher.

Similarly, we also observed significant differences in the yield (during 2021) between the neonicotinoids treated and control groups F _{(3, 8)} = 3.04, P < 0.001 (4.55 kg/plot). The average yield was approximately (M = 7.3, SD = 71.0; 2.92 kg/plot), (M = 8.0, SD = 129.1; 3.20 kg/plot) and (M = 8.2, SD = 101.1; 3.30 kg/plot) higher in control group as compared to imidacloprid, clothianidin and thiamethoxam respectively as shown in Figure 2. We detected the presence of parrots in the later stages of the experimental plots (in both years) and they affected the crop in the morning and evening time.

7. Discussion

The use of the neonicotinoids in the sunflower crop stimulates a decline in pollinator’s visitation which adversely affects the productivity of this crop. There have been several studies that have shown that pesticides have a detrimental influence on bee decline. Like carbamate group, which act directly in the bee’s nervous system, and impair their communicating ability, primarily by sharing information about the origins of community resources (Freitas & Pinheiro, 2010; Godfray et al., 2014). They often disrupt bees’ navigational memory and contribute to disorientation, stopping them from re-establishing their nesting sites (Bortolotti et al., 2003; Desneux et al., 2007).

In this study, we examined three neonicotinoids with nearly identical modes of action, as affirmed by prior investigation (Nauen et al., 2003). Notably, earlier research indicated that thiamethoxam negatively affected honeybees’ capabilities (Henry et al., 2012), whereas its impact on bumblebees’ colony origin was observed to be inconsequential by others (Elston et al., 2013). The effect of insecticides on pollinator enrichment and visitation can also be linked to repellence alertness, which can be impacted by both the neonicotinoid active component and additional chemicals found in commercial formulations of such insecticide products on insects. Bees are also not foraged by the use of certain kinds of insecticides and fungicides in flowers (Nigg et al., 1991; Solomon & Hooker, 1989).

Sometimes bees may recognize a given odour and associate it with lethal properties and dismiss the unrewarding, independent fragrance of flowers (Wright et al., 2010). In addition, some pesticides have lasting residual effects, likely remaining for several days in the eco-system (Pinheiro & Freitas, 2010). In another study, it is also indicated that a different reaction to a pesticide intake by bee species, likely due to differences in feed activity or body size (Freitas & Pinheiro, 2012).

Among the most common species observed in the inflorescences of the sunflower, only Apis mellifera and Apis florea were significantly impaired by the neonicotinoid treatment. Many experiments have also shown that the foraging success of Apis mellifera is disrupted by sublethal neonicotinoid doses. The neuro-active insecticides harm bees as well as reduce the number of workers that return to the hive (Henry et al., 2012). Researchers also found that the resistance of some chemical pesticides can also be attributed to the size of the body in comparison to some butterfly species. For instance, mostly smaller insect species are also vulnerable to neuro-active insecticides (Valdovinos-Nu~nez et al., 2009). A higher yield of sunflower crops was experienced with the abundance of pollinators (Aytekin & Agatay, 2008; Kreitlow et al., 2014). Our research reveals that the reduction in the visitor abundance during sunflower inflorescences caused by the application of these three neonicotinoids and hence in lower production than the control group. Moreover, using neonicotinoid insecticides like imidacloprid, clothianidin, and thiamethoxam can impact the behavior of pollinators specially bees. This means that the insects visit the flowers less often.

Pesticide damage has also been observed in other crops in the effects on pollination facilities and production. As in commercial apple orchards, fruit abortions are reported which leads the less fruit seed and production. Colonies exposed to a neonicotinoid pesticide provided lower visit rates to apple trees in the orchard and collected very less pollen often. More prominently, these colonies exposed to pesticides produced apples with less seeds, demonstrating a reduced services of pollination by the bees. These results show that exposure to pesticides may not only compromise the ability of bees to provide pollination services, but with important implications for both sustainable delivery and stable crop yields and working of natural ecosystems (Stanley et al., 2015), and the very same was reported in melon crops (Da Silva et al., 2015). Our results also suggest that the provision of reduced pollination services is not due to the induced changes by pesticides in the behavior of individuals bees, but most likely due to colony-level impacts.

Still, pesticides use is common for agricultural pest control, especially in monocultures, despite of their negative effects (Spadotto et al., 2004). However, if possible, pesticide use should be made rationally and its effect should be minimized, especially on pollinators and their natural enemies (Goulson & Kleijn, 2013). It is good practice to avoid the use of broad-spectrum pesticides with minimal application rates and to prevent them with an environmentally sustainable approach, such as biological control, should be preferred because they do not harm pollinators’ services and decrease the number of pests without impacting crop production (Pinheiro & Freitas, 2010).

In addition, it is important to rationalize the importance for native pollinators of natural areas and their ability to protect plant diversity and native forest on both sides of farm croppings, more rational and sustainable approaches to pest control (De Marko & Coelho, 2004). These areas serve as refuges and breeding sites for pollinators, promoting the development of bee diversity in crops (Chacoff & Aizen, 2005)., If ecologically and economically significant pollinator populations are to be maintained, then the suitability of any future use of neonicotinoids on flowering crops must be examined and further work is required to shed light on their impacts. Especially in relation to sunflower crops, it has been identified that the increase in pollinator diversity contributes to an increase in pollination services (Carvalheiro et al., 2011; Degrandi-Hoffman & Watkins, 2000), with bees up to five times more capable of increasing pollination services (Greenleaf & Kremen, 2006).

Based on the recent findings, the use of neonicotinoids in sunflower crops has been associated with a decrease in pollinator visitation, which can have detrimental effects on crop productivity (Goulson et al., 2015). Neonicotinoids, along with other pesticide classes, can exert negative impacts on bees, impairing their communication, navigation, and memory (Rundlöf et al., 2015; Pisa et al., 2015). Additionally, certain pesticides can persist in the environment for extended periods, leading to lasting residual effects that can persist for several days (Staveley et al., 2014). The foraging success of honeybees can be disrupted by sublethal doses of neonicotinoids, resulting in a reduction in the number of workers returning to the hive (Henry et al., 2012). Moreover, pesticide exposure not only compromises the ability of bees to provide pollination services but also poses significant implications for sustainable delivery and stable crop yields (Garibaldi et al., 2013; Klein et al., 2007). In recent study, Ke et al. (2023) highlighted the detrimental effects of neonicotinoids on Honeybees, leading to reduced olfactory perception, foraging success and impaired memory. Additionally, Stuligross et al. (2023) reported that neonicotinoid exposure negatively impacted the foraging success and nesting recognition of solitary bees, ultimately affecting pollination and population. These findings further underscore the urgent need to reevaluate the use of neonicotinoids in agricultural practices to safeguard pollinator populations and enhance crop productivity sustainably.

To mitigate these adverse effects, it is crucial to minimize pesticide use whenever possible and instead adopt more environmentally sustainable approaches, such as biological control (Desneux et al., 2007). Furthermore, safeguarding natural areas and preserving their capacity to function as refuges and breeding sites for pollinators is essential for promoting bee diversity within crops (Ricketts et al., 2008). By incorporating these strategies, we can enhance the ecological balance of agricultural systems and ensure the long-term sustainability of pollination services.

8. Conclusion

In Conclusion, this study indicates the harmful impact of pesticides on sunflower production by neonicotinoids. The use of imidacloprid, clothianidin, and thiamethoxam influenced floral visitors’ prosperity and led to a decrease in fruit quantity. This research has confirmed that decreased pollinators have foraged on the crop treated with neonicotinoids. Thus, our study emphasizes the importance of considering the potential impacts on pollinator biodiversity when making decisions regarding the use of imidacloprid, clothianidin, and thiamethoxam on sunflower crops. The evidence suggests that a cautious and judicious approach to pesticide application is necessary to strike a balance between pest management and the conservation of pollinators, ensuring the resilience and productivity of agricultural systems.

Author contributions

MSS conceived and designed the experiments, collected the bees, and analyzed the data. MFA contributed the materials, review the article, MAJ conducted the experiments and AS helped in data analysis and review the article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/23311932.2023.2258773

Additional information

Funding

The author(s) received no specific funding for this work.

Notes on contributors

Muhammad Shoaib Saleem

Muhammad Shoaib Saleem I am an experienced Research Scientist and Entomologist, currently holding the position of entomologist at the Department of Plant Protection (DPP), Government of Pakistan. Within my role, I actively participate in diverse areas such as planning, plant quarantine, locust expertise, and pesticide registration processes. With a strong academic background and completing PhD in Plant Protection, specializing in the impact of pesticides on the health, behavior, and ecology of pollinators, specifically focusing on honeybees and integrated pest management of vegetable insect pests, I possess a comprehensive understanding of entomological research and its practical implications. My research activities extend beyond the confines of academia as I actively engage in broader projects and issues pertaining to sustainable pest management strategies, pesticide risk assessment, and the conservation of pollinator populations. The research discussed in this paper aligns with my overarching objective of contributing to evidence-based decision-making processes, promoting the development of environmentally friendly agricultural practices, and ensuring the long-term sustainability of crop production.