Ethnobotanical Survey of Plants Used as Biopesticides by Indigenous People of Plateau State, Nigeria

Abstract

The quest for sustainable health, environmental protection, and the conservation of beneficial organisms makes the use of biopesticides a desirable option. This research aimed to identify the botanicals used in the management of farm and household pests in Plateau State, Nigeria. A cross sectional study was carried out using semi-structured questionnaires and on-the-spot, face-to-face interviews. The main issues captured include the pests, the plants used to manage the pest, the parts used, the cultivation status, the availability, the effects on the pests, the indigenous formulation methods, and the modes of application. The quantitative data were analyzed using the Frequency of Citation (FC), Relative Frequency of Citation RFC (%), and Use Value (UV). A total of 45 plant species belonging to 42 genera, 20 orders, and 30 families were found to be useful in the management of 15 different pests. The FC, RFC (%), and UV values identified the most popularly used plants as Mesosphaerum suaveolens (L.) Kuntze, Gymnanthemum amygdalinum (Delile) Sch.Bip., Azadirachta indica A. Juss, Canarium schweinfurthii Engl., Euphorbia unispina N.E.Br., and Erythrophloem africanum (Benth.) Harms. The plants that showed broad uses by the ethnic groups include Azadirachta indica A. Juss (7 uses), Erythrophloem africanum (Benth.) Harms, Khaya senegalensis (Desr.) A. Juss., and Gymnanthemum amygdalinum (Delile) Sch.Bip. The perception of the respondents indicated that most of the biopesticides are available, affordable, effective, eco-friendly, and safe. This survey provides a pathway for the formulation of stable biopesticides.

1. Introduction

Highly hazardous pesticides (HHPs) have continued to pose unacceptable risks and disproportionately account for the negative impacts of pesticides on human health and the environment, particularly in low and middle-income countries (LMICs) including Nigeria [1]. The challenge of HHPs’ management in Nigeria is enormous because of indiscriminate use, over reliance on synthetic pesticides, and lack of control measures leading to increased risks to food safety, the health of consumers and agricultural workers. Furthermore, the use of synthetic chemical pesticides has affected both the living and non-living components of the environment, as evident by diseases; mortalities; population changes; genetic disorders; physiological deformities; phytotoxicity; gene erosion in plants, mammals, birds, insects, and other organisms; and pesticide residues in the soil, air, and water [2].

The use of natural plants has been found to be humanly safe, ecofriendly, biodegradable, affordable, and to largely affect only the target pests in the management of pests of stored products, especially in the tropics [3,4,5,6,7]. Thus, the modern-day quest for sustainable health, the protection of the environment, and the conservation of beneficial organisms makes biopesticides a preferable option to synthetic chemicals in agricultural and household pest management [8]. For this reason, various indigenous communities in Nigeria use these botanicals to solve their unique recurring pest problems. It has been discovered that many of the botanicals such as Azadirachta indica A. Juss, Alstonia boonei De Wild., Annona squamosa L., Capsicum frutescens L., Eucalyptus camaldulensis Dehnh., Garcinia kola Heckel, Justicia adhatoda L., Lantana camara L., Moringa oleifera Lam., Nicotiana tabacum L., Ocimum spp., and Zingiber officinale Roscoe have been reported as potential alternatives in the control of the maize weevil (Sitophilus zeamais) [9,10,11].

There are numerous government agencies that have been established to research the use of biopesticides in Nigeria and to complement the existing pest management and control strategies of the Nigerian Government. These agencies include the Federal Ministry of the Environment (FMEV), the Federal Ministry of Agriculture and Rural Development (FMA and RD), the National Agency for Food and Drug Administration Control (NAFDAC), and the National Environmental Standards and Regulations Enforcement Agency (NESREA). Most of these programs are operational but are yet to sufficiently achieve the desired impact as further actions must be taken [1]. An indigenous knowledge system and practices is defined as a body of knowledge that develops within a given community through observation and real-life experiences over a period of time, communicated orally or otherwise from one generation to the other with the ultimate aim of molding its thought for the sole purpose of ensuring survival and progress [12]. Most rural communities have a fairly rich knowledge of the indigenous uses of medicinal plants; however, this knowledge, as well as its associated cultural practices, is gradually diminishing in the new generation [13]. Therefore, the survey and documentation of a country’s or community’s natural resources is an important prerequisite for the proper utilization of its raw materials, and the full knowledge of various plants is necessary as to enhance this proper utilization [14]. Several studies carried out in Africa and Asia showed that plants are routinely used as biopesticides [15,16,17,18,19,20,21].

Incidentally, there is a dearth of information with respect to the ethnobotanical knowledge system and practices in Plateau State, Nigeria, due to rural-urban migration, the substitution of traditional with modern practices and a penchant for orthodox drugs, or the utter disregard for traditional practices [22]. For this reason, only few ethnobotanical studies have been carried out in Plateau State on various medicinal plants. Some authors [23,24,25] reported the indigenous knowledge of general medicinal plants in some Local Government Areas (LGAs) of Plateau State. Their findings indicated that 39 plants from 33 families, 50 plants from 22 families, and 40 plants from 22 families were found to be used indigenously as medicinal plants. The authors of [26] surveyed plants used for the treatment of viral infections and found 64 medicinal plants from 39 families. The authors of [27] studied the medicinal plants used in the treatment of mental illnesses and found 42 plants from 31 families. The authors of [22] studied the medicinal plants used in the treatment of animal diarrhea in Plateau State and found 132 Plants from 25 families. No reports of an ethnobotanical survey on biopesticides were found, denoting the importance of this study. It is, therefore, of the utmost necessity for the knowledge of these biopesticides to be harnessed and properly documented for future generations. Some of these plants can be tested to ascertain their scientific validity, because the loss of this knowledge can only be stopped with rational ethnopharmacological studies that validate the local popular knowledge to be transmitted to the rest of the population, given its clear economic benefits, and establishing that ethnobotanical knowledge is important throughout the world [28]. Furthermore, the increasing awareness of the need for food safety and quality control applied to residual pesticide concentrations in harvested/stored farm produce, as well as the demand for safe and affordable alternatives from indigenous bioresources, also serve as the motivation for this survey. The result of this research will be important data for pharmacological studies and other Research and Development (R&D) activities related to biopesticides and for future studies on plants. Therefore, the aim of this study is to document the knowledge of the indigenous people of Plateau State with respect to their usage of bioresources in the management of pests to provide the baseline primary data on biopesticides that will enhance their usage, enable the development of safe alternatives to unacceptable HHPs, and the result in the enactment of national biopesticide policies. So far, this is the first reported attempt, as far as we know, to identify plants with pesticidal activities in Plateau State. It will further ascertain whether there is a consensus in the indigenous use of biopesticides amongst Plateau State’s ethnic groups.

2. Materials and Methods

2.1. Study Area

Plateau State is in the north central part of Nigeria with a land mass of about 30,913 km² and an average population of 4,200,442 as per 2016’s projected population figures [29]. The State is situated between latitude 8°24’ N and 10°46′ N and longitude 8°32′ E and 10°34′ E, as shown in Figure 1. It is generally mountainous, with rock formations scattered across the guinea savannah. The altitude of the entire state ranges from 300 to 1829 m above sea level. The high altitude in the northern part gives it a near temperate climate with an average temperature between 18 and 22 °C. On the other hand, the southern part has slightly different climatic conditions, which are generally more humid and warmer. The variation in the climatic conditions of the state explain why its biodiversity is high. The dominant occupation of the people in the area is farming, which occurs mainly in the rainy season. The major ethnic groups in the state include Berom, Afizere, Amo, Anaguta, Bache, and Irigwe (located in northern part of the state); Ngas, Ron-Kulere, Mwaghavul, Boghom, and Mushere (found in the central part of the state); and Taroh, Goemai, Doemak, Youm, Tehl, and Jukun (found in the southern part of the state), located in the 17 LGAs. The major crops grown include maize, rice, soya bean, groundnuts, acha, yam, Irish potatoes, and temperate vegetables.

2.2. Selection of Study Sites

In this study, the state was divided into three (3) zones: Northern, Central, and Southern zones. The sites were purposely selected based on ethnic representation to ensure effective coverage of the various ethnic/cultural groups that are either indigenous to or reside within the state. Site coordinates of sampling locations were determined using the Global Positioning System (GPS), G-PORTER GP-102+ model.

2.3. Ethnobotanical Data Collection

Ethnobotanical data were collected between August and September 2020 from the main ethnic groups in 55 localities from 15 LGAs of the state. A cross sectional study was carried out using semi-structured questionnaires randomly administered to knowledgeable persons within the various ethnic groups, from which 212 respondents were realized within the entire study area.

We obtained information in the field from both men and women that were informants (166 males and 46 females) in all communities visited according to the methods of [27,30]. The main issues captured in the questionnaires include locations, target pests, plants/plants products used for managing pests, parts used, cultivation status, availability in the locality, formulation methods, and modes of application. Majority of responses obtained were based on practical experience and very few on general knowledge of respondents.

To ensure maximal retrieval of the questionnaires, we carried out the exercise by on-the-spot administration of questionnaires, which further allowed room for wide interaction with the target groups and helped to raise other necessary, salient issues that the questionnaire was unable to address. Mindful of the diversity of the cultures and traditions of the various ethnic groups in the study area, we used the common languages spoken by the people for communication at the point of sampling. In the event where the spoken language was unfamiliar, we overcame this barrier with the aid of interpreters whom we guided on what the study aimed to achieve. Samples of plants referred to by respondents were collected by volunteers from the locality, farmlands, and nearby bushes for further identification.

2.4. Voucher Specimen Collection

Voucher numbers were assigned to the preserved specimens and deposited in the herbarium of the Department of Plant Science and Biotechnology, University of Jos. The plants were identified using keys and description given in [31,32] and arranged according to the classification of [31].

2.5. Data Analysis

The data collected were summarized using descriptive methods such as frequencies, percentages, graphs, and tables with the help of excel 2010 and SPSS 2019. To statistically analyse the data collected, the following quantitative indices were evaluated:

i 

Frequency of Citation (FC)

The FC was calculated as follows:

$$FC=\frac{Number of times \mathrm{a} particular species was mentioned}{Total number of times that all species were mentioned}\times 100$$

ii 

Relative Frequency of Citation (RFC)

The RFC index described by [33] was used as the number of informants who mentioned the use of the species (FC) divided by the total number of informants participating in the survey (N). The RFC index ranges from “0–1”; “0” when nobody referred to a plant as useful, and “1” when all informants referred to a plant as useful.

$$RFC =\frac{FC}{\mathrm{N}}$$

iii 

Use Value (UV)

The Use Value (UV) demonstrates the relative importance of plants known locally as a pesticide remedy. We calculated the UV using the following formula [27]:

$$UV =\frac{\sum Ui}{\mathrm{N}}$$

where Ui is the number of uses mentioned by each informant for a given species and N refers to the total number of informants interviewed. If a plant secures a high UV score, that indicates there are many use reports for that plant, implying that the plant is important, while a low score (approaching zero) denotes few reports related to its use.

3. Results

3.1. Socio-Demographic Data of the Respondents

Table 1. Statistics on the usage of plants as pesticides in Plateau State, Nigeria.

Parameter	Count	Percentage (%)
Gender
Female	46	21.70
Male	166	78.30
Occupation
Business	12	5.63
Civil servant	17	7.98
Clergy	9	4.23
Community Leader	1	0.47
Driver	1	0.47
Farmer	153	72.30
Herdsman	2	0.94
Hunter	1	0.47
Security	5	2.35
Student	7	3.29
Tradesman	4	1.88
Age (Years)
20–39	64	30.19
40–59	89	41.98
60–79	52	24.53
80–99	6	2.83
100–119	1	0.47

shows the demographic data of the respondents. The age of the respondents (46 female and 166 males) ranges between 20 to 105 years, and the majority of them were within 40 to 59 years (41.98%). Most of the respondents were farmers 72.3% (153) and only 7.98% (16) were formally employed.

3.2. Plant Species Used as Biopesticide in the Study Area

The survey revealed that 45 plant species belonging to 42 genera, 20 orders, and 30 families were used in the management of 15 different pests in Plateau State (

Table 2. Plants used as pesticides in Plateau State, Nigeria.

S/NO	Vouchers Numbers	Family	Species	English Name	Local Name	Parts Used	Target Pest
1	JUHN21000366	Amaryllidaceae	Allium cepa L.	Onions	Albassa (Hausa), Leh zipir (Mushere)	Bulb	Snakes
2	JUHN21000368	Amaryllidaceae	Allium sativum L.	Garlic	Tafarnuwa (Hausa), Ugulang (Amo)	Rhizome	Snakes
3	JUHN21000369	Amaryllidaceae	Crinum jagus (J.Thomps.) Dandy		Gadali/Albassan machiji (Hausa), Dau (Doemak), Girime (Irigwe),	Bulb; Leaf; Whole	Snakes
4	JUHN21000370	Annonaceae	Uvaria chamae P.Beauv.	Bush banana/Finger root	Rikuki (Hausa), Ngwayam (Amo)	Seed	Human lice, Lice
5	JUHN21000407	Apocynaceae	Calotropis procera (Aiton) W.T.Aiton	Calotropis	Tumfafia/Tumphafia (Hausa)	Latex	Fungi
6	JUHN21000371	Asphodelaceae	Aloe vera (L.) Burm.f.	Aloe vera		Latex	Fungi
7	JUHN21000372	Asteraceae	Gymnanthemum amygdalinum (Delile) Sch.Bip.	Bitter leaf	Shuwaka (Hausa), Munaan (Mwaghavul), Limtii (Mushere), Chulup (Berom), Gwanye, Manineng, Naf (Ron), Riti, Sudul	Latex; Leaf; Fruit	Aphids, Birds, Fungi, Insects, Lice, Mites, Rodents, Termites, Weevils
8	JUHN21000373	Bignoniaceae	Kigelia africana (Lam.) Benth.	Sausage tree	Hantsargiiwaa (Hausa)	Fruit	Termites
9	JUHN21000374	Bombacaceae	Ceiba pentandra (L.) Gaertn.		Bwas (Doemak), Dadawan Remi (Hausa)	Seed	Snakes
10	JUHN21000375	Burseraceae	Canarium schweinfurthii Engl.	African olive/Canarium	Atile (Hausa), Paat (Mushere, Mwaghavul), Toeng paat (Ngas) Ting fwat (Berom)	Latex; Leaf; Seed; Stem Bark	Mosquitos, Snakes, Termites, Weevils
11	JUHN21000376	Chenopodiaceae	Dysphania ambrosioides (L.) Mosyakin and Clemants		Kafi Gwano Wari (Hausa)	Leaf	Mosquitos, Snakes
12	JUHN21000367	Clusiaceae	Garcinia kola Heckel	Bitter Cola	Namijin goro (Hausa)	Fruit	Snakes
13	JUHN21000377	Cucurbitaceae	Lagenaria siceraria (Molina) Standl.		Kwarya duma (Hausa)	Leaf	Weevils
14	JUHN21000379	Euphorbiaceae	Euphorbia tirucalli L.	African Milkbush	Kaampaar (Mushere, Mwaghavul)	Latex; Leaf; Stem	Termites
15	JUHN21000380	Euphorbiaceae	Euphorbia unispina N.E.Br.	White cactus	Ngaar (Mwaghavul, Mushere), Tinya (Hausa), Bango (Bache), Tulup (Berom)	Latex; Leaf; Stem	Ants, Birds, Intestinal Worms, Rodents, Snakes, Termites
16	JUHN21000378	Euphorbiaceae	Jatropha curcas L.	Jathropha	Binidazugu (Hausa), Moor biring (Mushere, Mwaghavul), Kubazina (Amo)	Latex; Leaf; Leaf and Stem; Seed; Stem Bark	Fungi, Lice, Lice, Mites
17	JUHN21000409	Euphorbiaceae	Manihot esculenta Crantz	Cassava	Rogo (Hausa)	Leaf	Fungi
18	JUHN21000381	Fabaceae	Arachis hypogaea L.	Groundnut	Gyadda (Hausa), Khom (Mushere, Mwaghavul), Abwai (Amo), Yaba (Berom)	Fruit Peel, Seed	Termites
19	JUHN21000383	Fabaceae	Erythrophleum africanum (Benth.) Harms	African blackwood	Gwaska (Hausa), Kisom (Mupun), Ravu/iravo (Fyer), Kuchol (Amo), Sere (Fyem)	Bark; Latex; Leaf; Leaf and Stem Bark; Stem Bark; Whole	Birds, Fungi, Intestinal Worms, Rodents, Snakes, Termites, Ticks, Weevils.
20	JUHN21000382	Fabaceae	Parkia biglobosa (Jacq.) R.Br. ex G.Don	African Locust Bean tree	Dorowa (Hausa), Ting Mess (Mwaghavul), Tsekep Mess (Mushere)	Fruit, Leaf, Seed	Birds, Mosquitos, Rodents, Snakes, Termites, Weevils
21	JUHN21000408	Lamiaceae	Mesosphaerum suaveolens (L.) Kuntze	American Mint	Yin furtu (Youm), Din fut (Telh), Nimuum/Fining (Jukun), Jeye/Kuni muun (Mupun), Kuni ribuk (Torak), Mah mur (Mernyang), Nzeing (Berom), Sulendhe (Aten), Wok switi (Bogom), Yen Fet (Geomai), Yen fut (Mushere), Yim fut (Tal), Yim mur (Mernyeng)	Latex, Leaf	Fungi, Mosquitos, Snakes, Weevils
22	JUHN21000384	Lamiaceae	Melissa officinalis L.	Lemon balm	Kwili-shuiti (Bogom)	Leaf	Mosquitos
23	JUHN21000385	Lamiaceae	Ocimum americanum L.	Curry like	Daaddooyaa/(Hausa), Girime (Irigwe), Ihal-soo (Pyem), Ndaw (Tarok)	Leaf; Leaf and Stem	Butterflys, Mosquitos, Weevils
24	JUHN21000386	Lauraceae	Persea americana Mill.	Avocado Pear	Fiya (Hausa)	Seed	Rodents
25	JUHN21000398	Lythraceae	Lawsonia inermis L.	Henna Plant	Lalle (Hausa)	Flower	Snakes
26	JUHN21000403	Malvaceae	Adansoniadigitata L.	Baobab	Kuka (Hausa)	Leaf	Snakes
27	JUHN21000399	Malvaceae	Bombax ceiba L.	Bombax sp.	Tsap	Leaf	Birds, Rodents,
28	JUHN21000401	Arecaceae	Elaeis guineensis Jacq.	African oil palm	Tsekwep Moorbhang (Mushere), Shep Moorbhang (Mwaghavul)	Fruit; Seed	Termites, Ticks
29	JUHN21000402	Malvaceae	Hibiscus cannabinus L.	Kenaf	Rama (Hausa)	Seed/Calyx	Fungi Snakes
30	JUHN21000400	Malvaceae	Hibiscus sabdariffa L.	Sorrel	Yakuwa (Hausa), Diyang	Seed/Calyx	Snakes
31	JUHN21000405	Meliaceae	Azadirachta indica A. Juss	Neem	Dogon Yaro/Maina (Hausa) Darbagiah	Bark; Leaf; Seed; Seed, Leaf and Stem bark	Birds, Fungi, Human lice, Insects, Intestinal Worms, Lice, Rodents, Termites, Weevils
32	JUHN21000404	Meliaceae	Khaya senegalensis (Desr.) A. Juss.	Mahogany	Madachi (Hausa), Theen (Mushere, Doemak), Nchit (Bache), Tcho (Berom)	Bark; Leaf and Stem Bark; Seed; Stem Bark	Chicken Lice, Fungi, Human lice, Intestinal Worms, Lice, Mites, Termites, Weevils
33	JUHN21000406	Moraceae	Ficus macropodocarpa H.Lév. and Vaniot	Ficus	Durumi (Hausa)	Latex	Fungi
34	JUHN21000387	Myrtaceae	Eucalyptus camaldulensis Dehnh.	Eucalyptus	Rastata/gadina (Hausa), Cyata/Liyata (Irigwe)	Leaf	Mosquitos, Weevils
35	JUHN21000388	Opiliaceae	Opilia amentacea Roxb.	-	Rupan gadda (Hausa)	Leaf	Birds, Rodent
36	JUHN21000389	Pedaliaceae	Sesamum radiatum Thonn. ex Hornem.	Benniseed	Karkashi (Hausa), Lhem (Mushere, Mwaghavul)	Leaf	Human lice, Lice
37	JUHN21000390	Poaceae	Cymbopogon citratus (DC.) Stapf	Lemon grass	Kwalunkop (Aten)	Shoot	Mosquitos
38	JUHN21000391	Rubiaceae	Spermacoce verticillata L.	False buttonweed/African borreria	Gurdudal (Fulani)	Latex	Fungi, Mites
39	JUHN21000392	Rutaceae	Citrus sinensis (L.) Osbeck	Orange	Lemon zaki (Hausa),	Fruit; Fruit Peel; Leaf	Mosquitos
40	JUHN21000393	Sapotaceae	Vitellaria paradoxa C. F. Gaertn.	Shea Tree	Kadanya (Hausa)	Seed	Snakes
41	JUHN21000394	Scrophulariaceae	Eremophila oldfieldii F.Muell.		Karara, Kaikayi (Hausa)	Pod; Whole	Intestitnal Worms, Snakes
42	JUHN21000397	Solanaceae	Capsicum frutescens L.	Hot pepper/Pepper	Barkono, Chitta (Hausa), Shitaa (Mushere), Njitaa (Mwaghavul)	Fruit; Seed; Whole	Birds, Rodents, Termites, Weevils
43	JUHN21000395	Solanaceae	Solanum lycopersicum Lam.	Tomato	Tumatir (Hausa)	Leaf	Fungi
44	JUHN21000396	Solanaceae	Nicotiana tabacum L.		Taba (Hausa)	Leaf	Chicken Lice, Mosquitos, Snakes, Weevils
45	JUHN21000410	Verbenaceae	Lantana camara L.	Lantana	Kimbar/Kashin kuda (Hausa), Tikanahu (Aten)	Leaf	Mosquitos

). The families with the highest number of species are: Euphorbiaceae, Fabaceae, and Malvaceae with four species each; Amaryllidaceae, Solanaceae, and Meliaceae with three species each; and the remaining families were represented by one species each.

Thirty-three plant species from twenty-one families are used as a repellent, fifteen plant species from ten families as insecticides, twelve species from ten families as fungicides, and nine species from eight families are used to control rodents. A total of eleven species are used as insecticides and repellent; seven other species are used as avicides and rodenticides (Table 2 and Figure 2).

3.3. Parts Used, Cultivation Status, and Availability

The frequency of the plant parts used by the respondents (Figure 3) indicated that the most used plant parts were leaves (26 plants), followed by seeds (14 plants), latex (11 plants), fruit (7 plants), whole plant (5 plants), stem bark (4 plants), and fruit peel (3 plants), while the use of the rhizome, flower, leaf/fruit, and the combination of seed/leaf/stem bark occurred once.

On the other hand, the majority of the plant species occurred domestically (55%), followed by those in the wild (25%), and 20% were found both domestically and in the wild. The perception of the respondents on their availability indicated that most of the plants were always easily available (93%) and only 7% were difficult to come by (

Table 3. Method of Administration, Cultivation Status, Availability, and Status of Usage of Pesticidal Ethnobotanical Plants in Plateau State.

		Method of Administration	Cultivation Status			Availability		Status of Usage		Freq of Report Amongst Ethic Group
S/NO	Species		DO	DO/WI	WI	Easy	Difficult	Whole	Mixed
1	Adansonia digitata L.	SM(1)			1	1			1	1
2	Allium cepa L.	SP(1)	1			1		1		1
3	Allium sativum L.	SP(1)	1			1		1		1
4	Aloe vera (L.) Burm.f.	TO(1)	1			1		1		1
5	Arachis hypogaea L.	BA(1),PO(2), SR(1).	4			4		4		4
6	Azadirachta indica A. Juss	DR(7), OR (1), PO(16), SR(3), SP(1) and TO(3).	29		2	30	1	30	1	9
7	Bombax ceiba L.	DR(2).		2			2	2		1
8	Calotropis procera (Aiton) W.T.Aiton	TO(1).	2			2		2		2
9	Canarium schweinfurthii Engl.	PO(2), SM(19), TO(3).	16	2	6	22	2	24		10
10	Capsicum frutescens L.	DR(16), PO(3).	19			19		18	1	7
11	Ceiba pentandra (L.) Gaertn.	SP(1).			1	1		1		1
12	Citrus sinensis (L.) Osbeck	PO(2), SM(3).	5			5		3	2	4
13	Crinum jagus (J.Thomps.) Dandy	OR(1), PO(8), SR(2).	10		1	8	3	11		6
14	Cymbopogon citratus (DC.) Stapf	PO(9), SM(1).	9		1	9	1	10		7
15	Dysphania ambrosioides (L.) Mosyakin and Clemants	PO(14), SM(2), TO(1).	16	1		17		17		6
16	Elaeis guineensis Jacq.	PO(1), TO(2).	3			3		3		3
17	Eremophila oldfieldii F.Muell.	OR(1), PO(1).	2			2		2		2
18	Erythrophleum africanum (Benth.) Harms	DR(12), PO(4), SM(1), SR(1), SP(4), WS(1).	2	17	4	15	8	23		8
19	Eucalyptus camaldulensis Dehnh.	PO(4), SM(3).	6		1	7		7		3
20	Euphorbia tirucalli L.	PO(9).	6		3	9		9		5
21	Euphorbia unispina N.E.Br.	BA(2), DR(10), PO(11), SP(1).	2	1	21	17	7	23	1	4
22	Ficus macropodocarpa H.Lév. and Vaniot	TO(1).	1			1		1		1
23	Garcinia kola Heckel	PO(1).	1				1	1		1
24	Gymnanthemum amygdalinum (Delile) Sch.Bip.	DR(11), PO(26), SR(1), SP(2), TO(6), WS(2).	39	6	3	47	1	44	4	8
25	Hibiscus cannabinus L.	SR(1), SP(1), TO (1).	3			3		3		2
26	Hibiscus sabdariffa L.	PO(1), SP(1).	2			2		2		2
27	Jatropha curcas L.	TO(7).	6	2		8		8		3
28	Khaya senegalensis (Desr.) A. Juss.	BT(2), DR(1), OR(4), PO(1), SP(2), TO(10).	11	5	4	17	3	19	1	12
29	Kigelia africana (Lam.) Benth.	PO(3).	3			3		3		1
30	Lagenaria siceraria (Molina) Standl.	PO(1).			1	1		1		1
31	Lantana camara L.	PO(8), SM(9).	13	4		17		16	1	6
32	Lawsonia inermis L.	TO(1).	1			1		1		1
33	Solanum lycopersicum Lam.	TO(1).	1			1		1		1
34	Manihot esculenta Crantz		1			1			1	1
35	Melissa officinalis L.	POandSM(1).	1			1		1		1
36	Mesosphaerum suaveolens (L.) Kuntze	PO and SM(7), SM(17), TO(1).	8	60	1	68	1	69		17
37	Nicotiana tabacum L.	PO(5), SM(2), SR(1), SP(1).	9			9		9		8
38	Ocimum americanum L.	DR(2), PO(5).	4	3		4	3	7		3
39	Opilia amentacea Roxb.	DR(2).			2	2		2		1
40	Parkia biglobosa (Jacq.) R.Br. ex G.Don	DR(4), PO(1), SM(1), SP(4), TO(1).	7	1	3	11		9	2	6
41	Persea americana Mill.	BA(1).	1			1		1		1
42	Sesamum radiatum Thonn. ex Hornem.	WS(10).	10			10		10		6
43	Spermacoce verticillata L.	TO(7).	5	1	1	7		7		5
44	Uvaria chamae P.Beauv.	TO(2).		2		1	1	2		1
45	Vitellaria paradoxa C. F. Gaertn.	SM(1).					1	1		1
	Percentage		55	20	25	93	7	97	3

A = Bait, BT = Bathing, DR = Dressing, OR = Orally, PO = Positioning, SM = Smoking, SR = Spraying, SP = Spreading, TO = Topically, WS = Washing, DO = Domestic, and WI = Wild.

).

3.4. Modes of Preparation and Application

The respondents employed a variety of methods in the preparation and administration of pesticidal plants (Table 3). The study revealed that the commonest practice for pesticide application employs the use of a single species (97%) as compared to the use of a mixture of two or more species (3%). Figure 4 depicts that the most common method of application is positioning fresh or dry plant materials to emit a fragrance/odor (41.39%); followed by a topical application of latex, sap, or exudates (24.17%); and the smoking of dry or fresh leaves (17.22%).

3.5. Uses and Ethnobotanical Indices

The species with the highest number in the pesticidal use category (

Table 4. Frequency of Citation (FC), % Relative Frequency of Citation (%RFC), and Use Value (UV) of pesticidal plants in the study area.

S/N	Species	Effect on the Pest	FC	RFC (%)	UV
1	Adansonia digitata L.	Repellent (1)	1	0.47	0.005
2	Allium cepa L.	Repellent (1)	1	0.47	0.005
3	Allium sativum L.	Repellent (1)	1	0.47	0.005
4	Aloe vera (L.) Burm.f.	Fungicide (1)	1	0.47	0.005
5	Arachis hypogaea L.	Attractant/Biocontrol (4)	4	1.89	0.019
6	Azadirachta indica A. Juss	Antifeedant (1), Avicide (2), Expellant (1), Fungicide (1), Insecticide (11), Repellent (13), Rodenticide (2)	31	14.62	0.118
7	Bombax ceiba L.	Avicide (1), Rodenticide (1)	2	0.94	0.005
8	Calotropis procera (Aiton) W.T.Aiton	Fungicide (1), Repellent (1)	2	0.94	0.009
9	Canarium schweinfurthii Engl.	Repellent (24)	24	11.32	0.108
10	Capsicum frutescens L.	Avicide (1), Antifeedant (1), Insecticide (4), Repellent (12), Rodenticide (1)	19	8.96	0.08
11	Ceiba pentandra (L.) Gaertn.	Repellent (1)	1	0.47	0.005
12	Citrus sinensis (L.) Osbeck	Repellent (5)	5	2.36	0.024
13	Crinum jagus (J.Thomps.) Dandy	Repellent (11)	11	5.19	0.047
14	Cymbopogon citratus (DC.) Stapf	Repellent (10)	10	4.72	0.047
15	Dysphania ambrosioides (L.) Mosyakin and Clemants	Repellent (17)	17	8.02	0.061
16	Elaeis guineensis Jacq.	Insecticide (2), Repellent (1)	3	1.42	0.014
17	Eremophila oldfieldii F.Muell.	Anthelmintic (1), Insecticide (1)	2	0.94	0.009
18	Erythrophleum africanum (Benth.) Harms	Acaricide (1), Avicide (4), Insecticide (11), Repellent (2), Fungicide (1), Rodenticide (4)	23	10.85	0.071
19	Eucalyptus camaldulensis Dehnh.	Insecticide (2), Repellent (5)	7	3.3	0.028
20	Euphorbia tirucalli L.	Insecticide (1), Repellent (8)	9	4.25	0.042
21	Euphorbia unispina N.E.Br.	Avicide (3), Fungicide (1), Insecticide (8), Repellent (7), Rodenticide (4)	23	10.85	0.071
22	Ficus macropodocarpa H.Lév. and Vaniot	Fungicide (1)	1	0.47	0.005
23	Garcinia kola Heckel	Repellent (1)	1	0.47	0.005
24	Gymnanthemum amygdalinum (Delile) Sch.Bip.	Avicide (3), Fungicide (4), Insecticide (6), Miticides (3), Repellent (29), Rodenticide (3)	48	22.64	0.175
25	Hibiscus cannabinus L.	Fungicide (1), Repellent (2)	3	1.42	0.014
26	Hibiscus sabdariffa L.	Repellent (2)	2	0.94	0.009
27	Jatropha curcas L.	Fungicide (4), Insecticide (2), Miticides (1)	7	3.3	0.019
28	Khaya senegalensis (Desr.) A. Juss.	Anthelmintic (3), Expellant (2), Fungicide (2), Insecticide (5), Miticides (1), Repellent (7)	20	9.43	0.09
29	Kigelia africana (Lam.) Benth.	Attractant/Biocontrol (3)	3	1.42	0.014
30	Lagenaria siceraria (Molina) Standl.	Antifeedant (1)	1	0.21	0.005
31	Lantana camara L.	Repellent (17)	17	8.02	0.08
32	Lawsonia inermis L.	Repellent (1)	1	0.47	0.005
33	Solanum lycopersicum Lam.	Fungicide (1)	1	0.47	0.005
34	Manihot esculenta Crantz	Insecticide (1)	1	0.47	0.005
35	Melissa officinalis L.	Repellent (1)	1	0.47	0.005
36	Mesosphaerum suaveolens (L.) Kuntze	Antifeedant (2), Insecticide (1), Repellent (66)	69	32.55	0.307
37	Nicotiana tabacum L.	Insecticide (1), Repellent (8)	9	4.25	0.042
38	Ocimum americanum L.	Insecticide (2), Repellent (5)	7	3.3	0.033
39	Opilia amentacea Roxb.	Avicide (1), Rodenticide (1)	2	0.42	0.005
40	Parkia biglobosa (Jacq.) R.Br. ex G.Don	Avicide (1), Repellent (9), Rodenticide (1)	11	5.19	0.047
41	Persea americana Mill.	Rodenticide (1)	1	0.47	0.005
42	Sesamum radiatum Thonn. ex Hornem.	Insecticide (10)	10	4.72	0.047
43	Spermacoce verticillata L.	Fungicide (4), Repellent (3)	7	3.3	0.033
44	Uvaria chamae P.Beauv.	Repellent (2)	2	0.94	0.009
45	Vitellaria paradoxa C. F. Gaertn.	Repellent (1)	1	0.47	0.005

FC = Frequency of citation, RFC = Relative frequency of citation, UV = Use value.

) were A. indica (seven uses); Erythrophleum africanum (Benth.) Harms, Khaya senegalensis (Desr.) A. Juss., and Gymnanthemum amygdalinum (Delile) Sch.Bip. (six uses); and Euphorbia unispina N.E.Br. and Capsicum frutescens L. (five uses). The FC, RFC (%), and UV values of the identified plant species for the study area range from 1–69, 0.47–32.25, and 0.005–0.307, respectively (Table 4). The pesticidal plants reported in this study with high FC, RFC (%), and UV values are Mesosphaerum suaveolens (L.) Kuntze (69, 32.55%, and 0.307 respectively), G. amygdalinum (48, 22.64%, and 0.175 respectively), A. indica (31, 14.62%, and 0.118 respectively), Canarium schweinfurthii Engl. (24, 11.32%, and 0.108 respectively), and E. unispina and E. africanum (23, 10.85%, and 0.071 each, respectively). Fourteen of the species mentioned have FC, RFC (%), and UV values of 1, 0.210%, and 0.005 respectively.

3.6. Comparative Analysis of Plant Species Reported by Different Ethnic Groups

When the reported plant species of the ethnic groups were compared (

Table 5. Use Report, Number of Informants, and Plants Species used by Different Ethnic Groups.

Ethnic Groups	Use Report	No. of Informants	No. of Species Reported
Angas	33	15	14
Ron-Kulere	18	11	12
Berom	38	16	11
Goemai	48	17	11
Anaguta	25	9	10
Taroh	33	11	10
Afizere	24	10	8
Amo	22	8	8
Mwaghavul	16	7	8
Pyem	9	5	8
Aten	11	7	7
Fyer	12	4	7
Tehl	24	10	7
Jukun	24	10	6
Mupun	19	7	6
Fulani	6	4	5
Irigwe	23	8	5
Mushere	18	10	5
Bache	16	8	4
Bogwom	11	6	4
Buji	11	5	4
Doemak	22	12	10
Jar	10	4	4
Youm	20	8	4

), we found that the Angas people contributed 14 species, followed by the Ron-kulere with 12 species, Berom and Goemai with 11 species each, and Anaguta and Tarok with 10 species each. The Goemai recorded the largest number of use reports (URs) (48), followed by the Berom with 38, and Angas and Taroh with 33 cases each.

The results showed that 27 (60%) of the 45 plant species are used by more than one ethnic group. Four species (M. suaveolens, K. senegalensis, C. schweinfurthii, and A. indica) are the most common to all ethnic groups having occurred 17, 12, 10, and 9 times, respectively. E. africanum, N. tabacum, and G. amygdalinum occurred eight times each. Apart from similar uses of plants, each ethnic group also used its own unique plant species. Eighteen out of the forty-five plants species are uniquely used by only one ethnic group, while four species are used by two and three groups each.

4. Discussion

4.1. Demographic Data

Generally, the study revealed that the indigenous people of Plateau State have sufficient knowledge of the use of plants for the management of pests. The profile of the respondents interviewed in this study indicates that a large section of the population is aware of the use of pesticidal plants from different ethnic groups irrespective of their sex and age. More information was obtained from men about the pesticidal plants due to the fact that they are more engaged in farming than women [34]. Interestingly, a considerable number of women were encountered during the interview due to their active roles in subsistence farming and other agricultural activities common to the state. In Plateau State and other reported areas [18,28], the respondents’ age of 40–59 years depicts the peak of their productive years (Table 1). The authors of [35] indicated a curvilinear relationship between the age of the respondents and the number of plant species identified in Niger, suggesting that the knowledge of plant species drops after a certain age.

4.2. Plant Species Used as Biopesticide

The 45 pesticidal plants from 30 families used for pest management purposes reported in this study represents a higher number than the 36 plant species from 28 families earlier reported on crop protectants in the Federal Capital Territory of North Central Nigeria by [36]. Another report by [15] revealed the use of 31 plants belonging to 22 families for pest management by rural farmers in Ekiti State, Nigeria.

The family with the highest number of species are: Euphorbiaceae, Fabaceae, and Malvacea followed by Amaryllidaceae, Solanaceae, and Meliaceae (Table 2). Previous studies by [36] have confirmed the prevalence of pesticidal effects of plant species belonging to the family Fabaceae and Lamiaceae followed by Apocynaceae, Cucurbitaceae, Euphorbiaceae, and Plantaginaceae. Our results agree with those of [16,17], who found that the family Euphorbiaceae was one of the most used sources of plant-based pesticides in Southwestern and Northern Uganda, respectively. Other studies in sub-Saharan Africa such as [18,19] also reported that Euphorbiaceae is the family with the highest number of biopesticidal plants. This observation could be attributed to their range of phytochemical compounds, including the polyphenols, phenolic acids, flavonoids, saponins, tannins, acetylenes, coumarins, and triterpenes in these families [37].

Thirty-two plant species were found to be used as repellents, fifteen as insecticides, and twelve as fungicides, while nine were used to control rodents, with several plants having broad pesticidal activities. Interestingly, A. indica, which is used as an antifeedant, avicide, expellant, fungicide, insecticide, repellent, and rodenticide, is of economic significance among the plants. For example, the activity of A. indica has been associated with the presence of Azadirachtin reportedly used in the control of over 200 insect pests from different insect orders [20]. A notable example of an avicide and rodenticide in this study is E. africanum (‘Gwaska’ in Hausa), reputed for its use as an ideal poison to kill or scare away stubborn pests such as birds and rodents from cultivated farmland as corroborated by [38,39].

Similarly, M. suaveolens, the most frequently cited plant belonging to the family Lamiaceae, was the most represented insect repellent plant family as found also in an earlier study in Kenya [21]. It is used for some ethnobotanical applications in rural communities in African countries [40] and the plant is readily available close to villages, along roadsides, on farmsteads, etc. In line with our findings, the plant has been reported by many to be a potent herb that exhibits insecticidal properties [41] that include feeding deterrence and insect repellency against mosquitoes and pests of stored grains [42,43,44,45].

The data obtained revealed that some plants such as A. indica, C. frutescens, E. africanum, E. unispina, K. senegalensis, and G. amygdalinum, had multiple pesticidal properties, as they were implicated in the control of five to seven pest each. Similarly, an investigation on the protectant effectiveness of some Nigerian native plants against the maize and cowpea weevil by [46,47] recognized that several plants have broad pesticidal activity and are commonly used in traditional agricultural applications in many parts of developing countries.

4.3. Parts Used, Cultivation Status and Availability

Our findings in this study, wherein the most frequently used plant parts are the leaves followed by seeds, latex, and fruits (Figure 2), are consistent with earlier reports [48,49,50]. This could be because leaves are readily available, very abundant, and very easy to harvest [51]. The harvesting of leaves is relatively more sustainable since the plant can regrow new leaves easily, especially during the rainy seasons. According to the plant defense theory [52], the bioactive compounds or secondary metabolites presumed to be responsible for repelling attackers are more concentrated in the leaves compared to other parts of the plants [17,50]. Providentially, the preference for leaves may greatly benefit from the perspective of the conservation of these plants compared to harvesting the plants’ roots, bark, or gathering the whole plant. In the same vein, the minimal use of roots and the whole plant for pest control is an added advantage for conservation purposes.

This study and other similar studies [53,54] revealed that most of the respondents believed that most of the plants are available, effective, dependable, eco-friendly, and have low toxicity. The level of respondents’ awareness, confidence, and acceptability may be a strong impetus for the implementation of biopesticides’ utilization and development in the region. This also emphasizes the significance of indigenous knowledge and practices in the promotion of the use and production of pesticides in Nigeria.

The various plants used by the respondents for biopesticides are locally sourced from the wild or cultivated domestically by the locals; they are not obtained from commercial sources.

4.4. Modes of Preparation and Application

The practice of using a single plant for pesticide preparation compared to the use of a mixture of two to three plant species is very evident in this study. On the contrary, for ethnomedicinal studies, most of the reported remedies [55] involved the use of concoctions of two to three plant species.

For most insects, positioning fresh or dry plant materials was the most popular method of application for repelling insects such as mosquitoes. Their positioning by the hanging of repellent plants on the walls, roofs, or by the entrance was consistent with previous studies in Ethiopia [56], Guinea Bissau [57], and Uganda [48]. In addition, [57] reported that hanging fresh leaves gave a repellent activity of greater than 70% against mosquitoes. The practice of positioning M. suaveolens, A. indica, E. africanum, Eucalyptus tereticornis Sm., K. senegalensis, Lagenaria siceraria (Molina) Standl., Ocimum americanum L., and G. amygdalinum in between grains during storage has been observed in many localities. It is expected that these plants naturally provide several organic bioactive compounds which in turn provide an odor that is typically volatile in nature and is found to be offensive, especially against insect pests of stored grain, mosquitoes, and flies [58,59].

The common practice of the smoking or smoldering of both fresh or dry leaves inside the house to repel mosquitoes and other insects of veterinary importance accords with reports from Guinea Bissau [57], Kenya [54], and Ethiopia [56]. In Guinea Bissau, it was demonstrated that smoldering the leaves of M. suaveolens showed repellent activity beyond 80% [57]. It was documented that the repellent activity of burned plants might be due to the release of specific volatile compounds (e.g., β-ocimene) created during combustion or from the plant materials themselves [48,60].

4.5. Uses and Ethnobotanical Indices

Demonstrated by the FC, RFC (%), and UV values of the identified plants species, M. suaveolens, G. amygdalinum, A. indica, C. schweinfurthii, E. unispina, and E. africanum are the most popular pesticidal plants in this study (Table 4). The RFC (%) and UV values are indicators of the frequency mentioned by the informants and indicate that they are the most recognized plant in the study area. In agreement with this, the UV values in our study are driven by species with the greatest number of uses rather than those cited by more informants. However, the intensive use and excessive exploitation of these species can threaten their existence and, consequently, the biodiversity of the region, since 25% of the species used by the local population are from the wild. It is, therefore, necessary to take protective measures and regulate their harvesting to preserve the plant species of the region and ensure their sustainability.

4.6. Comparative Analysis of Plant Species Reported by Different Ethnic Groups

The largest number of URs reported by the Goemai, Berom, Angas, and Taroh might have resulted from these ethnic groups having the largest number of informants. The URs reflect the importance of the category in the ethnic group, and the diversity of plant species indicates the richness of the ethnic group’s knowledge.

The strong similarity among the plants used and the URs of the ethnic groups, namely, the Angas and Ron-kulere, Goemai and Taroh, and Berom and Anaguta, may be attributed to their having closer cultural exchanges, shared religious beliefs, and proximity to one another. The villages visited are often inhabited by a single ethnic group, but the villages of other neighboring ethnic groups are usually a short distance away; this encourages close communication and the free exchange of information amongst them, using similar/common dialects. Four plants are widely used in these communities as biopesticides, namely, M. suaveolens, K. senegalensis, C. schweinfurthii, and A. indica. This could be due to their availability, higher use knowledge, and similar criteria for their selection. Most informants believed that the strong smell emitted by these plants may be responsible for their use to manage both farm and household pests.

Apart from the similar uses of the plants, each ethnic group also retains its own unique knowledge. These differences in knowledge may be related to their environment. Being in different environments, they have different nearby plant resource banks to choose from. The distribution and availability of one plant to an ethnic group and the absence of another to a different group may be responsible for the optional selection of a plant to solve an existing pest problem.

Furthermore, our interaction with some of the informants yielded some claims that we considered unscientific and rather superstitious or spiritual. For instance, there were occasional mentions of some plants being used to repel or kill witches and wizards. Specifically, Allium sativum L. and O. americanum were reportedly used by the Amo, Bache, Buji, and Irigwe ethnic groups to repel witches and wizards, while most of the ethnic groups reported they use E. africanum to detect or kill witches and wizards. The claim of using A. sativum agrees with similar reported work [61]. On the other hand, some ethnic groups use E. enispina to repel farm enemies that hamper farm produce yields. Further interaction with other ethnic groups also revealed that twisted rope obtained from the bark of Piliostigma thonningii (Schumach.) Milne-Redh., when tied around the necks of dogs, can repel ticks (Rhipicephalus sanguineus).

5. Conclusions

This study reports the first ethno-biopesticide survey in Plateau State, Nigeria. From the study, a total of 45 plant species belonging to 42 genera, 20 orders, and 30 families were found to be useful in the management of 15 different pests by 24 indigenous people of the state. Notably, 33 of the plant species from 21 families are used as a repellent, 15 species from 10 families as insecticides, 12 species from 10 families as fungicides, and 9 species from 8 families are used to control rodents. The most frequently used plants based on FC, RFC (%), and UV values are M. suaveolens, G. amygdalinum, A. indica, C. schweinfurthii, E. unispina, and E. africanum. Comparing the plants used by different ethnic groups, we discovered the Angas people contributed 14 species, the Ron-kulere were responsible for 12 species, the Berom and Goemai contributed 11 species each, while the Anaguta and Tarok input 10 species each. Similarly, the Goemai ethnic group recorded the largest number of URs (48), followed by the Berom with 38, and the Angas and Taroh with 33 cases each. The practice of using a single plant for pesticide preparation compared to the use of a mixture of two to three plant species is very evident in this study. For most insecticides, positioning fresh or dry plant materials was the most popular method of application for repelling insects such as mosquitoes. In addition, the common practice of the smoking or smoldering of both fresh or dry leaves inside the house to repel mosquitoes and other insects was a common occurrence among all the ethnic groups. Notably, our findings indicated that there was a consensus with respect to the use of biopesticides for pest control by the ethnic groups covered in the survey. However, the efficacy and safety of all the reported plants will be verified in our further work.