The Double-Edged Sword: Local Perspectives on the Spread, Impact, Management, and Uses of the Invasive Chromolaena odorata in Southern Nigeria

Abstract

In Nigeria, Chromolaena odorata poses significant threats to agriculture by disrupting ecosystem structure and function, thereby altering ecosystem services. However, our understanding of its impact, potential uses, and control measures, particularly from the perspective of local communities who interact directly with the plant, presents opportunities for a balanced approach to sustainable management. The aim of this study was to document the knowledge and perceptions of the introduction and spread of C. odorata, its ethnopharmacological applications, and its effects on crops, livestock, and wildlife, as well as discuss control strategies. Using participatory rural appraisal techniques, we administered semi-structured questionnaires to 150 respondents across six villages in Edo State, Nigeria. The findings reveal that C. odorata is a well-recognized invasive species that has been present for several decades and is commonly referred to by its local name, “Awolowo weed”. Although many respondents were unsure of the reasons behind its introduction, most were familiar with its mode of dispersal. A significant proportion of respondents view the weed as a serious threat to agriculture and a major hindrance to human movement by foot to and from their farmlands where C odorata is dominant. However, many also reported its relative ease of management. Interestingly, 92.7% acknowledged the medicinal value of C. odorata, citing its use in treating fever, wounds, and stomach aches, while 84% reported its ability to enhance soil fertility. Most respondents did not perceive the plant as harmful to livestock or wildlife. Though many believe that the plant has continued to spread, 83.8% oppose its complete eradication. Instead, they highlighted Elephant grass (Pennisetum purpureum Schumach) as a more problematic weed that requires immediate intervention. In summary, exploring the local benefits of C. odorata highlights the importance of leveraging local knowledge and practices to develop a robust, integrated approach for its sustainable long-term management.

1. Introduction

Throughout history, humans have facilitated the spread of plants across different regions due to migration, trade, and globalization. These plant distributions can be either intentional—where plant species with desired traits are introduced for cultivation in a new region—or accidental, where unwanted plants or weeds are transported along with other goods during trans-Atlantic or trans-Saharan trade. Upon arriving in a new environment, alien plants first establish self-sustaining populations, also referred to as naturalization. Some of these naturalized plants remain confined to their introduced habitats without spreading or causing harm to native species. However, others spread rapidly, expanding into new areas and reaching population levels that outcompete indigenous plant species. These species are then termed “invasive alien species” (IASs) [1]. Several hypotheses suggest that IASs thrive in their new environments because they are free from the constraints they faced in their native regions, such as natural enemies or competitors. As a result, the resources that would have been used to combat these pressures are redirected toward developing novel survival mechanisms, allowing these invasive plants to outcompete native species and disrupt ecosystem functions [2].

Invasive alien species not only affect biodiversity and ecosystem function but also have significant impacts on human livelihoods. A plethora of studies emphasize the importance of documenting the perspectives of rural communities that are directly affected by invasives [3]. Livelihoods in rural areas, which are often tied to crop and livestock farming, are directly influenced by invasive species and understanding how invasive plants impact these livelihoods is crucial for making informed management decisions and preventing conflicts, particularly in cases where local communities have found ways to benefit from these invasive alien plant species [4]. Although the term “invasive alien species” generally conveys negative connotations, research has shown that people’s perceptions of the negative, positive, or nuanced impact of these species on their livelihood vary, depending on their interactions with the plants over time.

Numerous studies have documented the detrimental effects of invasive plants on agricultural sustainability. For instance, Parthenium hysterophorus L. has been found to harm crops and livestock in Pakistan [5], while Mikania micrantha Kunth reduced forest resources essential for livelihoods in Nepal [6]. In East Africa, Lantana camara L. diminished forage availability and crop yields, while its control costs pose a threat to food security [7]. These negative impacts of invasive species on livelihoods have prompted government efforts to minimize their spread. For example, South Africa implemented national-scale eradication programs, such as “Working for Water”, aimed at eliminating invasive species like Acacia, Eucalyptus, Prosopis, and Pinus. However, these efforts, costing over USD 450 million, have been met with varying degrees of success [8]. Conversely, not all interactions with invasive species are negative. For example, a study by van Wilgen et al. [9] revealed that local communities reported both positive and negative impacts of Vernonanthura polyanthes (Spreng.) based on how they had used the plant over time. Similarly, some people who used Acacia dealbata for fuel or construction materials viewed it positively. At the same time, crop farmers whose land had been invaded by the species perceived it negatively [10]. Despite L. camara’s adverse effects on biodiversity, it has been used as a wood substitute when other resources were scarce [11]. These examples highlight the importance of understanding the perspectives of rural communities that directly interact with invasive species, especially when management measures and governmental policies are to be implemented.

Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) is a weed that was accidentally introduced to Nigeria in 1937 [12] and has since posed a serious threat to ecosystem integrity. It disrupts vegetation structure, composition, and flora–fauna interactions, leading to biodiversity loss [13]. The weed’s invasive success is attributed to its high reproductive rate, rapid growth, allelopathic properties, and resilience in diverse ecological zones [14,15]. When in high abundance, C. odorata forms dense thickets along forest edges and fallow lands, suppressing native vegetation and increasing the risk of wildfires [16]. Studies in southern Nigeria demonstrated that the high density of C. odorata reduces the species diversity of native plant species [17], while similar findings have been reported in Nepal’s forest ecosystems [18]. Given the detrimental effects of C. odorata on ecosystems, it is critical to examine how it impacts human livelihoods, especially in rural areas where people depend on land resources for survival.

Chromolaena odorata has plagued farming communities for decades, causing significant harm to farmers’ livelihoods. Its aggressive spread across plantations, farmlands, and fallow areas has directly impacted human well-being in these regions. In addition to the costs of controlling the weed, its tendency to fuel wildfires and reduce crop yields poses further challenges. Studies in East Africa and West Timor revealed that C. odorata infested grazing lands, resulting in significant losses for livestock and crop farmers [19,20]. Despite these negative impacts, some local communities have found ways to benefit from the weed. For instance, it has been reported to improve soil fertility and possess ethnopharmacological benefits [15,21,22,23]. Understanding the perspectives of local dwellers who interact directly with C. odorata is crucial, as their insights can provide valuable information about both the positive and negative effects of the weed.

In southern Nigeria, research on C. odorata has primarily focused on its impact on native plant density, its ethnomedicinal and agricultural uses, and its potential for biogas production, as well as efforts to identify biological control agents and their applications in classical biocontrol [15,24,25,26,27]. However, there is a need for comprehensive information regarding the effects of C. odorata on people’s livelihoods. Some of the positive and negative impacts of the weed on both biodiversity and livelihoods have been reviewed [15], but the conclusions thereof were largely anecdotal and require further empirical investigation to provide clearer insights and propose ecosystem-friendly management strategies.

This study utilized participatory rural appraisal techniques to assess local perceptions of C. odorata and its effects on rural communities’ livelihoods. The primary objective was to explore the weed’s impact on crop and livestock production, wildlife, and the health conditions of the local inhabitants while also evaluating how local communities have harnessed the plant for their benefit. Additionally, this paper examines the strategies employed by the inhabitants to manage C. odorata in the region.

2. Materials and Methods

2.1. Study Area

This study was carried out from April 2023 to January 2024 across six villages within Edo State, Nigeria (Figure 1). The selected villages were Ekosodin, Iguosagie, and Ogua, located in Ovia Northeast Local Government Area (LGA), and Ahor, Iguovbiobo, and Urokuosa, situated in Uhunmwonde LGA. The six villages were selected based on the C. odorata distribution in Edo State, Nigeria [15]. Edo State is located within the rainforest zone (6.6342° N, 5.9304° E) of Nigeria’s southern region and is characterized by a tropical wet and dry or savanna climate. The state experiences an average annual temperature of approximately 28.78 °C (83.8°F) and receives an average annual rainfall of about 183.49 mm (7.22 inches). Rainfall is prevalent throughout the year, with approximately 266 rainy days in a year. The state’s elevation is roughly 239.16 m (784.65 feet) above sea level. The primary land use practices in the study area are crop farming and livestock rearing. The region is rich in rainforest vegetation endowed with an abundance of trees, shrubs, and grasses. Over 190 species of trees have been documented in the forest reserves within the state [28]. The soils in the study area are classified as Typic Kandiudults and they originate from the Benin rock formation, which is underlain by limestone. They are predominantly composed of lateritic clay sand, which is characterized by a reddish-brown coloration [29]. Most of the inhabitants in these villages cultivate crops such as cassava, cocoa, oil palm, yam, and maize, while several households also rear livestock (such as goats, sheep and chickens) within their homesteads. In addition, there is evidence of nomadic activities of cattle herds transiting and grazing through the region in no specific patterns [30].

2.2. Data Collection

Data on the knowledge, perception, and impact of Chromolaena odorata (C. odorata; Figure 2) on the livelihoods of rural inhabitants were gathered using semi-structured questionnaires. The study systematically collected information on the following key aspects:

• Socio-demographic characteristics of respondents;
• Local knowledge and perception of the introduction and spread of C. odorata;
• Perceived benefits and negative impacts of C. odorata;
• Control measures for C. odorata employed by the respondents.

A total of 150 randomly selected individuals, residing in areas with a documented high density of C. odorata [15], were interviewed. However, the interviews were preceded by a pilot study that involved 20 participants from a different village that were excluded in the current number of respondents (i.e., the 150 individuals). The responses from the 20 pilot study participants helped refine the questionnaires before the large-scale study commenced, following documented recommendations and perspectives [31]. We determined a sample size of 150 using Cochran’s formula for finite populations, as the surveyed villages have limited populations [see 31 for rationale]. This sample size was chosen to balance feasibility with the need for broad and diverse representation among respondents.

Data collection was conducted in the field by trained field assistants who utilized participatory rural appraisal (PRA) techniques [32]. These techniques ensured inclusive participation, allowing respondents who had no formal education to contribute their knowledge. Data were collected through oral communication and visual aids, such as showing respondents harvested C. odorata plants so they could have a proper understanding of the subject before commenting. Field assistants visited respondents in their homes to conduct interviews and record responses. The oldest member of the household was interviewed, and questions were posed in English, as well as in native and pidgin languages, to ensure that respondents fully understood the questions and could provide accurate answers in designated spaces.

2.3. The List of All Questions Contained in the Questionnaire

• DEMOGRAPHICS

• Sex: Male [ ]  Female [ ]
• Age: 18–30 years [ ] 31–40 years [ ] >40 years [ ]
• Highest level of education: Primary [ ] Secondary [ ] Tertiary [ ] No formal education [ ]
• Household size: <5 [ ] 6–10 [ ] >10 [ ]
• Occupation: Crop Farmer [ ] Livestock farmer [ ] Trader [ ] Combination of two or more [ ] Other, specify_____
• Do you own livestock: Yes [ ] No [ ]
• Type of livestock: Goats [ ] Sheep [ ] Cattle [ ] Pigs [ ] Combination of two or more [ ] Other [ ] None [ ]
• Do you have a farmland: Yes [ ] No [ ]
• If yes, what is the size? 1 hectare [ ] 2 hectares [ ] 3 hectares [ ] >3 hectares [ ]
• What crops do you grow? Cocoa [ ] Cassava [ ] Oil palm [ ] Maize [ ] Combination of two or more [ ] None [ ] Others, specify____________

• LOCAL KNOWLEDGE AND PERCEPTION OF INTRODUCTION AND SPREAD OF C. odorata

11.

Do you know C. odorata? Yes [ ] No [ ]

12.

What is the native name of C. odorata? __________________

13.

When did C. odorata arrive this community? Last year [ ] 6–10 years ago [ ] 11–20 years ago [ ] >20 years ago [ ] Don’t know [ ]

14.

Why was C. odorata introduced? Ornamental [ ] Weed [ ] Hedge crop [ ] Don’t know [ ]

15.

How is C. odorata spread? Humans [ ] Animals [ ] Naturally (wind or water) [ ] Combination of human, animals and natural [ ] Don’t know [ ]

• BENEFITS OF C. odorata

16.

Is C. odorata beneficial? Yes [ ] No [ ] Don’t know [ ]

17.

Do you feed your animals with C. odorata leaves? Yes [ ] No [ ] Don’t know [ ]

18.

Does C. odorata increase soil fertility? Yes [ ] No [ ] Don’t know [ ]

19.

Does C. odorata help in wound healing? Yes [ ] No [ ] Don’t know [ ]

20.

Do you use C. odorata to treat fever? Yes [ ] No [ ] Don’t know [ ]

21.

How do you use it to treat fever?_______________________________________

22.

Are there other benefits? If yes, specify _______________________________

23.

If given the option of orthodox medicine and C. odorata, which will you go for and why?___________________________________________________

• NEGATIVE IMPACT OF C. odorata

24.

Does C. odorata decrease useful grasses of animals? Yes [ ] No [ ] Don’t know [ ]

25.

Does C. odorata reduce grazing land for your animals? Yes [ ] No [ ] Don’t know [ ]

26.

Does C. odorata affect other shrubs? Yes [ ] No [ ] Don’t know [ ]

27.

Does C. odorata decrease wildlife? Yes [ ] No [ ] Don’t know [ ]

28.

Does C. odorata obstruct movement? Yes [ ] No [ ] Don’t know [ ]

29.

Does C. odorata decrease availability of useful plants? Yes [ ] No [ ] Don’t know [ ]

30.

Does C. odorata reduce crop yield? Yes [ ] No [ ] Don’t know [ ]

31.

Do your animals eat C. odorata leaves? Yes [ ] No [ ] Don’t know [ ]

32.

Does C. odorata cause sickness in animals? Yes [ ] No [ ] Don’t know [ ]

33.

How many of your animals died from eating C. odorata? None [ ] 1–5 [ ] 6–10 [ ] >11 [ ]

• CONTROL OF C. odorata

34.

How do you control C. odorata? Slashing [ ] Burning [ ] Herbicide [ ] Uprooting [ ] Combination of two or more, specify_______________

35.

Do you have injuries during slashing? Yes [ ] No [ ] Don’t know [ ]

36.

Is C. odorata difficult to control? Yes [ ] No [ ] Don’t know [ ]

37.

Is the spread of C. odorata increasing? Yes [ ] No [ ] Don’t know [ ]

38.

Do you think C. odorata should be eradicated? Yes [ ] No [ ] Don’t know [ ]

39.

What other weed is problematic in this area?

3. Results

3.1. Socio-Demographic Characteristics of the Respondents in the Study Area

Among the 150 respondents interviewed, 99 were male and 51 were female. The majority of respondents (63.3%) were over 40 years old, with household sizes ranging from 6 to 10 members. The educational levels of respondents varied, with 28.2% having completed primary education, 39.6% having completed secondary (high) school, 18.1% having attained tertiary (college) education, and 14.1% having no formal education (Figure 3).

Crop farming was the predominant occupation, with 50.7% of respondents engaged in this activity (Figure 3). C. odorata is commonly found in rural areas, where agriculture is the predominant livelihood. As a result, the high proportion of farmers (53.3%) among respondents reflects the demographic composition of the study area rather than a sampling bias toward agricultural perspectives. This distribution aligns with the occupational structure of rural communities, where farming is the primary economic activity. Of the 50.7% of crop farmers, 31.3% primarily grew cassava, while 35.4% of the farmers cultivated more than one type of crop. Farmland sizes varied, with 34.7% of respondents (52 individuals) owning farmlands greater than 3 hectares. Additionally, 55.8% of respondents owned livestock, with goats being the most commonly reared livestock, accounting for 26.6% of the total (Figure 4).

3.2. Local Knowledge and Perception of the Introduction and Spread of C. odorata

Out of the 150 respondents interviewed, 149 (99.3%) were familiar with the weed Chromolaena odorata (C. odorata). Some of the respondents even pointed directly at the weed during the interviews, indicating its prevalence, particularly in farm areas. They commonly referred to it as the “fertilizer plant.” The most widespread native name for the weed was “Awolowo weed”, as mentioned by 82.7% of respondents. Other names included “Akintola” (6.7%), “Queen Elizabeth weed” (2.7%), and “Independent weed” (0.7%). Additionally, 10% of respondents identified the weed by various other local names. According to many respondents, C. odorata became widespread in 1956, coinciding with the first visit of Queen Elizabeth II to Nigeria, which led to its being named “Queen Elizabeth’s leaves”. Some respondents also associated the weed with Nigeria’s struggle for independence between 1956 and 1960, stating that its flowers were used as a symbol of celebration after the nation gained sovereignty, a movement led by Chief Obafemi Awolowo. This association resulted in the weed being called “Awolowo leaves” and “Independence leaves” (Figure 5).

When it came to knowledge about the time of the weed’s arrival in their communities, responses varied significantly. Of the 150 respondents, 89 (59.3%) claimed that C. odorata had been in their community for over 20 years, while 39 respondents did not know its time of arrival. Three respondents reported that the weed had been present for 6–10 years, and one reported it as appearing last year. Meanwhile, 16 respondents indicated that the weed had been introduced 11–20 years ago. Some respondents stated that the weed had been present “before we were born”, “we just met it”, or “it was there before my parents were born”. These responses were collectively recorded as indicating that the weed had been present for more than 20 years (Figure 6).

When asked about the reasons for the introduction of C. odorata, the majority of respondents (40.7%) admitted that they did not know why the weed was introduced. However, 30% believed it was introduced as a weed, 21% as a hedge crop, and 13.3% as an ornamental plant. Most respondents (76.7%) agreed that the weed spreads naturally, with its seeds being dispersed by air or water (Figure 7).

3.3. The Benefits of C. odorata

The majority of the respondents (92.7%) acknowledged C. odorata as a beneficial plant. However, despite its perceived benefits to humans, 60.3% of the respondents stated that they do not use the weed as animal feed. A significant proportion of the respondents (84%) highlighted the weed’s role in enhancing soil fertility, with some noting that crops grown on fallow lands previously occupied by C. odorata produce good yields. Additionally, C. odorata was widely recognized for its medicinal properties in the study area. An overwhelming 94.6% of respondents reported that the weed is effective in preventing bleeding and aiding in wound healing. Furthermore, 84.6% of respondents indicated that they use C. odorata to treat fever. (

Table 1. The benefits of C. odorata.

Category	Responses	* Frequency	Percentage of Response
Is C. odorata beneficial?	Yes	139	92.7
	No	10	6.7
	Do not know	1	0.6
Do animals eat C. odorata?	Yes	56	38.3
	No	88	60.3
	Do not know	2	1.4
Does C. odorata enhance soil fertility?	Yes	130	89.7
	No	11	7.6
	Do not know	4	2.7
Does C. odorata stop bleeding and enhance wound healing?	Yes	141	94.6
	No	7	4.7
	Do not know	1	0.7
Is C. odorata used in treating fever?	Yes	126	84.6
	No	20	13.4
	Do not know	3	2

* Total frequencies less than 150 indicate either missing or invalid responses where the respondent(s) did not provide any responses to the questions.

). The methods for treating fever with the weed varied among the respondents (Figure 8): 32.1% of respondents boil the weed and drink the infusion or extract; 20% mix C. odorata leaves with other herbs before boiling and drinking the concoction; 12.9% drink the extract obtained from squeezing or mashing the leaves in water; and 12.1% mix the squeezed extract with other substances before consumption.

When asked about other health benefits of C. odorata, 17.8% of the respondents mentioned its use in treating stomach aches. However, 39% were not aware of any other health benefits associated with the weed (

Table 2. Other benefits/uses of C. odorata in the study area.

S/N	Other Benefits of C. odorata	No. of Respondents	Percentage of Respondents
1	Stomach pain/ache	26	17.8
2	Ulcer	8	5.5
3	Diarrhoea	1	0.7
4	Urinary tract infection	2	1.4
5	Malaria	3	2.1
6	Diabetes	4	2.7
7	Headache/Back pain	4	2.7
8	Other ailments	13	8.9
9	Culinary uses	16	11
10	Agricultural uses	7	4.8
11	Do not know or unclear responses	57	39
12	Injuries	4	2.7
13	Improves sexual libido	1	0.7
	* Total	148	100

* The total frequency is less than 150 because two of the respondents did not provide any responses to the questions.

). Regarding the choice between C. odorata and orthodox medicine for treating fever, most respondents (56.4%) preferred C. odorata over orthodox medicine (22.1%). Additionally, 8.7% of respondents chose both, stating that C. odorata would be used as first aid, with orthodox medicine serving as the primary treatment (Figure 9). The reasons given by respondents for choosing C. odorata over orthodox medicine are detailed in

Table 3. Responses on the reasons for the preference of C. odorata (Awolowo), orthodox medicine, or both to treat fever.

S/N	C. odorata (Awolowo)	Orthodox Medicine	Both
1	“It is more accessible”.	“I am used to orthodox drugs”.	“I will use Awolowo in the morning and Orthodox in the evening”.
2	“It is fresh from nature, natural, and healthy”.	“I cannot stress myself to make the herbs”.	“I will use Awolowo as first aid before using orthodox medicine”.
3	“It is easy to prepare”.	“My children do not like herbs; doctors warn against drug abuse”.	“I will use Awolowo, but if it does not work, I will use the orthodox medicine”.
4	“It is reliable, cheap, free, and works faster than orthodox medicine”.	“It has a dosage”	“Depending on the state of the fever”.
5	“It clears all diseases or other ailments in the body”.	“It is well preserved”.
6	“The forefathers used it and lived long”.	“My knowledge of science”
7	“I trust it more than orthodox medicine (which is mainly chalk)”.	“It is pure and active”.
8	“I am a traditional man who believes in traditional treatment options”.	“I was raised with orthodox medicine”.
9	“Awolowo acts fast in the healing process, and it is first aid”.
10	“My family sells herbs, and orthodox medicine is not powerful”.

.

3.4. The Negative Impact of C. odorata on Livelihoods

According to 53.4% of respondents, the presence of C. odorata in their farms directly contributes to reduced crop yields. Additionally, 63.7% of respondents noted that C. odorata grows rapidly and forms dense thickets, which impede farmers’ movement across the invaded landscape. This often necessitates repeated slashing to keep the narrow footpaths (approximately 1 m wide) clear within the farming areas. This repetitive and time-consuming weed-slashing task further limits agricultural activities as farmers spend a considerable amount of time slashing the weed. Despite these challenges, a significant portion of respondents (85%) did not perceive C. odorata as having a detrimental impact on wildlife. Many reported that animals such as cane rats, porcupines, and antelopes frequently inhabit thickets of C. odorata, suggesting that the weed provides a habitat rather than a hindrance to these species. Furthermore, most respondents indicated that C. odorata does not negatively affect useful grasses, grazing lands, shrubs, or other beneficial plants. Similarly, they reported no adverse effects of the presence of the weed on animal health. In terms of livestock interactions with C. odorata, 59.9% of respondents stated that livestock do not consume the weed. As a result, 83.3% reported that livestock do not fall ill from eating the weed. However, among the few respondents who observed animals feeding on C. odorata, antelopes, snails, and rabbits were specifically mentioned as species that consume the plant. An overwhelming 96.4% confirmed that no livestock had died from ingesting the weed (

Table 4. The negative impact of C. odorata on livelihood.

Indices	Responses (%)
	Yes	No	Do not know
Useful grasses	24	73.3	2.7
Grazing land	23.4	74.5	2.1
Shrubs	43.4	55.9	0.7
Wildlife	10.2	87.8	2
Movement	63.7	36.3	0
Availability of useful plants	36.4	63.6	0
Crop yield	53.4	44.5	2.1
Animals consuming C. odorata	36.7	59.9	3.4
Animals sick due to eating C. odorata	10.4	83.3	6.3
	1–5 animals (%)	None (%)
Number of animal deaths recorded after they consumed C. odorata	3.6	96.4

).

3.5. The Control of C. odorata

Farmers employ various methods to control the spread of C. odorata, with the choice of technique often depending on available resources and the specific conditions of their farmland. Among the respondents, the most commonly used method is slashing, with 45.5% of farmers reporting the use of cutlasses or machetes to cut down the weed manually. This labour-intensive method is preferred due to its immediate effectiveness, although it requires regular repetition to manage regrowth. A smaller portion of respondents, 12.8%, rely on burning to control C. odorata, particularly during the dry season when conditions favour this method. Additionally, 10.8% of respondents reported uprooting the weed by hand, which, while effective for small-scale infestations, is time-consuming and physically demanding. The use of herbicides, e.g., glyphosate, paraquat, or atrazine, is the least common method of weed control, cited by only 1.4% of respondents. Some farmers also employ a combination of methods, adapting their approach based on the extent of infestation and other local factors (

Table 5. The management and control of C. odorata.

Method of Control	No. of Respondents	Percentage of Respondents
Slashing	67	45.3
Burning	19	12.8
Herbicide	2	1.4
Uprooting	16	10.8
Slashing and herbicide	2	1.4
Slashing and burning	15	10.1
Slashing and uprooting	15	10.1
Burning and herbicide	1	0.7
Slashing, burning, and uprooting	8	5.3
Slashing, burning, and herbicide	1	0.7
Slashing, herbicide, and uprooting	2	1.4
* Total	148	100

* The total frequency is less than 150 because two of the respondents did not provide any responses to the questions.

).

When asked about the safety of controlling C. odorata, 60% of respondents reported that they do not sustain injuries during the process. However, 40% mentioned that injuries can occur, particularly when slashing mature or dried strands of the weed, which can become tough and hazardous to handle. Regarding the spread of C. odorata, 55% of respondents observed that the spread of C. odorata is increasing, while 36% believed that the spread of the weed has depreciated over time. Despite this, a significant majority, 83.8%, believe that C. odorata should not be eradicated, citing its beneficial effects on health and soil fertility (

Table 6. The responses on C. odorata’s control and spread.

Category	Response	* Frequency	Percentage of Response
Does C. odorata cause injuries?	Yes	58	40.0
	No	87	60.0
Is C. odorata difficult to control?	Yes	27	18.5
	No	113	77.4
	Do not know	6	4.1
Is the spread of C. odorata increasing?	Yes	82	55.4
	No	53	35.8
	Do not know	13	8.8
Should C. odorata be eradicated?	Yes	24	16.2
	No	124	83.8

* Total frequencies less than 150 indicate that missing or invalid responses were omitted.

).

When asked to identify the most problematic weed in their area, 59% of respondents pointed to elephant grass (Pennisetum purpureum Schumach) as the most challenging to manage. Descriptions of this weed include phrases such as “it is a wicked grass”, “it is too difficult to control”, and “it does not respond to pesticides”, highlighting the frustration it causes. Some farmers also noted that elephant grass has begun to outcompete C. odorata in certain areas, further complicating weed management efforts. In addition to elephant grass, 20.1% of respondents identified Mimosa diplotricha C. Wright, commonly known as “touch-me-not”, as another problematic weed. This plant is particularly troublesome due to the dense rows of thorns on its stems, which can cause serious injuries to farmers. A few respondents also mentioned other challenging weeds, including Sida acuta Burm. F (wire grass or stubborn grass), Bambusa vulgaris Schrad (bamboo), and Megathyrsus maximus Jacq (Guinea grass), each presenting unique difficulties in weed management within the study area (

Table 7. The most problematic weed in the study area.

Common Name	Scientific Name	Number of Respondents	Percentage of Respondents
Elephant grass	Pennisetum purpureum	82	59.0
Touch-me-not	Mimosa diplotricha	28	20.1
Stubborn grass/Wiregrass	Sida acuta	6	4.3
Elephant grass/Touch-me-not/Wiregrass	As written above	18	12.9
Bamboo	Bambusa vulgaris	2	1.4
Guinea grass	Megathyrsus maximus	3	2.3
* Total		139	100

* A total number of respondents less than 150 indicates that missing or invalid responses were omitted.

).

4. Discussion

Chromolaena odorata is a well-known invasive weed in Southern Nigeria, and a significant majority of rural inhabitants are familiar with its presence. Although historical records show that it was first documented in Nigeria in 1937 [12], most respondents in the study area reported its widespread occurrence by 1956. The weed’s spread can explain this discrepancy in reported arrival times. After arriving in 1937, C. odorata likely went through the less prominent but no less profound stages of invasion, comprising colonization, naturalization, and spread, before becoming widely noticeable [1]. According to the theories of plant invasion, an exotic plant must overcome various biotic and abiotic barriers during the acclimatization stages before it becomes invasive, which usually takes many years [2,33]. The initial colonization and naturalization phases may have gone unnoticed, only becoming apparent when the weed started affecting the livelihoods of locals, hence the time gap in when it was first perceived. Taken together, from the first documented evidence to the locals’ perception of its arrival, it is anecdotally suggestive of a little short of two decades for Chromolaena’s lag phase.

Interestingly, the majority of respondents in this study consider C. odorata beneficial, particularly for its medicinal (or ethnobotanical) and agricultural fertility uses [23,34,35]. Empirical support for the locals’ perceptions of the soil-improving capacity of C. odorata abound in the literature [35,36,37,38]. For instance, Tondoh and coworkers [36] reported an increase in key soil macronutrients, mineral pools, soil macroinvertebrate abundance, and overall soil biomass in C. odorata-dominated sites compared to control plots. Similarly, C. odorata was found to be a more effective fallow species than Calliandra calothyrsus and Pueraria phaseoloides in enhancing soil fertility [37]. Others [35,38] have enunciated C. odorata’s efficiency in soil nutrient accretion, although the extent of nutrient enrichment largely depended on the duration of the fallow period. In addition to its role in nutrient cycling, C. odorata has been identified as an effective organic mulch (15). In fact, records [39,40] indicate that its rapid decomposition facilitates nutrient release, thereby improving soil fertility. Moreover, C. odorata has been demonstrated to enhances soil microbial biomass and enzymatic activities [41], which may contribute to its rapid biodegradability and its competitive advantage over native vegetation [42].

Beyond its effects on soil properties, C. odorata has also been linked to improved agricultural productivity, as evident in the increase in crop yields following fallow periods dominated by C. odorata. For example, notable yield improvements in yam and rice cultivated on previously C. odorata-occupied soils have been reported [43,44,45]. The most plausible explanation for these yield improvements is the enhanced availability of essential nutrients following C. odorata-mediated soil enrichment.

In rural areas, where access to healthcare is limited, villagers often rely on affordable, readily available alternatives like medicinal herbs. This was demonstrated in this study when over 50% of the respondents indicated a preference for using aqueous leaf extracts of C. odorata after mild heating to treat fever due to its low cost and accessibility. Farmers, who are frequently exposed to injuries during agricultural work, often use the weed to stop bleeding, which is seen as a significant and beneficial first aid before seeking orthodox medical assistance. Furthermore, many respondents believe in the potency of herbs to heal various ailments because they believe in traditional medicine prepared through herbs that are directly sourced from nature. Over 80% of respondents claimed that the weed plays an important role in agriculture as a fallow plant, rejuvenating nutrient-depleted soils. Similar studies [46,47] have highlighted C. odorata’s use in traditional medicine and agriculture. However, contrary to these reports, C. odorata provided no benefits in East Africa, where its recent introduction caused sudden and devastating impacts [20]. We consider that the most plausible explanation for these obverse patterns could be because, for East Africans, the presence of the weed is relatively new, and the people are yet to adapt to the reality of the invasive weed, unlike in Ghana and Nigeria, where a longer human–chromolaena interaction periods allowed its integration into the daily lives of rural-dwelling West Africans [22,46]. In Nigeria, in 1975, when the weed was fairly new to the inhabitants, the weed’s devastating impact on oil palm plantations and crop farms prompted a large-scale biological control effort after mechanical and chemical control methods failed to control the weed effectively [48]. Despite the introduction of the biocontrol agent Pareuchaetes pseudoinsulata to manage the weed, it was unsuccessful. Because subsequent large-scale control efforts were not recorded, the locals likely adapted to C. odorata by utilizing the weed for several purposes, which metamorphosed into its beneficial properties today, hence reiterating the fact that as people interact with an invasive weed, they discover novel ways to utilize it.

Despite the perceived benefits, this study also reveals that C. odorata poses a substantial economic burden on farmers due to its negative impact on crop yields and quality. More than half of the respondents indicated that the weed’s encroachment on farmlands reduces crop productivity. In Ghana, its initial invasion led to a sharp decline in staple crop yields, forcing farmers to abandon affected areas [14]. Our finding aligns with previous studies from Tanzania and Kenya, where C. odorata similarly dominated agricultural landscapes, diminishing yields [19], while in Nepal, C. odorata also affected the productivity of key crops [47]. Other invasive weeds, such as Parthenium hysterophorus, have caused crop declines in Pakistan, affecting potato, sugarcane, and maize production [5]. Likewise, Vernonanthura polyanthes and Lantana camara have negatively impacted agricultural productivity in various communities [11,49]. Furthermore, over 60% of respondents in this study reported that C. odorata hinders movement due to the dense thickets it forms, a phenomenon also observed with Mikania micrantha in Nepal, which obstructed human and wildlife movement [6].

Despite its invasiveness, over 70% of respondents find C. odorata relatively easy to control, using manual methods such as uprooting or cutting (slashing with cutlasses), with few opting for herbicides. Similar reports from Ghana indicate that the use of herbicides to control the weed is rare [21]. In contrast, weeds like Parthenium hysterophorus are more difficult to manage, requiring substantial financial costs for control [5]. Nevertheless, farmers in the study area reported encountering mainly newly emerged shoots of C. odorata, which are easier to remove manually.

However, the respondents claimed that Elephant grass (Pennisetum purpureum L.) poses a more significant challenge to farmers than C. odorata. Elephant grass, commonly called Napier grass, is a member of the Poaceae family, and it is native to tropical Africa. Farmers in the communities surveyed alluded to the spread of Elephant grass to the nomadic cattle herdsmen (commonly referred to as Fulani herders) who migrate from northern Nigeria to the southern parts of the country in search of grazing land for their cattle. The farmers believe that the weed’s seeds are dispersed through cattle faeces, contributing to its rapid spread across farmlands. Respondents widely regarded elephant grass as a troublesome weed because of its resilience, rapid regrowth (even after mechanical removal), and resistance to pesticides, resulting in difficulty in managing this weed and contributing to low yield in crop farming in the area. Despite its invasive tendencies, many scientific studies have emphasized the potential benefits of Elephant grass as fodder for cattle and raw material for biofuel production [50,51].

While Elephant grass serves as a valuable resource in some contexts, its capacity for rapid spread and regrowth remains a serious challenge for rural farmers in the study area, most of whom are crop farmers rather than livestock farmers. Consequently, they do not derive economic benefits from the grass, making its aggressive growth much more of a threat than an asset, as opposed to how some perceive C. odorata. Several factors contribute to the prioritization of Elephant grass management over C. odorata. Firstly, Elephant grass is highly persistent and vigorous, exhibiting rapid growth [51] that allows it to outcompete crops for essential resources such as light, water, and nutrients. Its ability to thrive in areas with precipitation above 1000 mm, its high yield capacity, and its resistance to pests and diseases makes the study site particularly suitable for its proliferation, further enhancing its dominance in agricultural fields. Farmers in the study area find Elephant grass particularly difficult to control due to its resilience. Traditional methods such as slashing are largely ineffective because of its rapid regrowth, while its high photosynthetic efficiency allows it to recover quickly even after herbicide application [51]. Consequently, managing Elephant grass requires more effort and resources, making it a greater concern for farmers than C. odorata, despite the latter’s well-documented ecological impacts.

Unsurprisingly, the locals perceive C. odorata as a rapidly spreading plant. This aligns with the concept of “propagule pressure”, which posits that invasive plants with high seed production are more likely to dominate their habitats [52]. The weed’s prolific seed production and rapid germination have enabled its continued spread in invasive regions. A similar situation was observed in Kenya with the invasive Prosopis species, which continued to spread despite being incorporated into local livelihoods [53]. In contrast, in Ghana, C. odorata was found to be decreasing in density, likely due to the successful establishment of biocontrol agents like Pareuchaetes pseudoinsulata and Cecidochares connexa in that region [21]. However, the effectiveness of biocontrol can vary depending on ecological context, and there are cases where unintended consequences have arisen. For instance, Havens et al. [54] cautions that the promotion of biocontrol as the most effective approach for invasive weed management is sometimes overstated due to potential non-target effects. This highlights the need for rigorous, case-specific assessments of novel biocontrol agents before widespread implementation, particularly as past biocontrol efforts against C. odorata in Nigeria, such as the introduction of P. pseudoinsulata, were unsuccessful [46]. While using biocontrol agents remains a valuable tool in managing invasive weeds [55], its application should be complemented with integrated management strategies [54,56].

5. Conclusions

The findings of this study highlight the relationship between rural communities and invasive species. While C. odorata is widely recognized for its rapid spread, local perceptions reveal a dual narrative one that acknowledges both its challenges and its usefulness; herein lies the ‘double-edged sword’. Its integration into medicinal and agricultural practices demonstrates how communities adapt to ecological changes, transforming a once-perceived threat into a resource. Notwithstanding, concerns remain over its encroachment on farmlands and its impact on crop management. Contrastingly, Pennisetum purpureum emerges as a more pressing agricultural concern, with farmers emphasizing its persistence, rapid regeneration, and competitive nature. This distinction in perspectives suggests that management priorities are shaped by direct economic and labour-related burdens, which underscores the importance of local knowledge in understanding invasive species dynamics. Effective management strategies should incorporate community experiences to ensure practical and sustainable interventions. One possible strategy is the promotion of controlled utilization, where local communities are encouraged to harness C. odorata for soil improvement and medicinal use, while implementing preventive measures to limit its encroachment on farmlands. For instance, policymakers could support research into optimized fallow periods to maximize soil benefits without allowing unchecked spread. Additionally, community-based awareness programs could guide farmers on targeted removal strategies that help to contain the weed in agricultural zones. Biological control remains a viable option, but its implementation should consider past challenges and the potential for unintended ecological consequences. Further exploration of microbial and fungal biocontrol agents should be pursued alongside local knowledge integration. Ultimately, a participatory approach—where policymakers, researchers, and local stakeholders collaborate—will be essential for developing sustainable management strategies that mitigate the invasive risks of C. odorata while preserving its recognized benefits.