Open access peer-reviewed chapter - ONLINE FIRST

Insecticide Use and Application in Cameroon

Written By

Nambangia Justin Okolle, Ekwa Yawa Monono, Amungwa Ivan Tabikam, Mambo Stephania Kinge and Magwell Pierre Fils Rodrique

Submitted: October 15th, 2021Reviewed: January 12th, 2022Published: March 27th, 2022

DOI: 10.5772/intechopen.102634

IntechOpen
InsecticidesEdited by Ramón Eduardo Rebolledo Ranz

From the Edited Volume

Insecticides [Working Title]

Dr. Ramón Eduardo Rebolledo Ranz

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Abstract

Cameroon has a diverse natural environment with five agro-ecological zones that support the cultivation of many crops. The country relies mainly on agriculture, with main export crops such as cocoa, coffee, cotton and banana. The agricultural sector occupies an average of about 47 million hectares of land with different production system practices such as mono cropping, mixed cropping, intercropping etc. Biotic factors are major constraints. These biotic constraints are seriously hindering the crop production, resulting to pre-and post-harvest losses and lower yields. These pests are mainly from the arthropod, vertebrate, mollusk, weeds and nematode groups and disease-causing pathogen such as fungi, viruses and bacteria. With these constraints famers in developing world like Cameroon are forced to look for ways to control these pests and pathogens which lead to the use of numerous preventive and curative techniques including the use of insecticides. Using insecticides is not against the law but the application methods and the supply routes carried out by farmers and traders respectively might be bad. This is why this chapter reviews the insecticides supply routes, registration procedure and registered insecticides, insecticidal application with its malpractices while looking at its intoxication as well as the alternatives to the use of synthetic insecticides in Cameroon and make possible recommendations to promote judicious use of insecticides in Cameroon.

Keywords

  • registration
  • malpractices
  • intoxications
  • synthetic chemical alternatives

1. Introduction

The purpose of this research was to gather relevant information concerning the sources, practices and intoxications resulting from the use of insecticides in Cameroon. It was also to collect information on different options that can replace synthetic insectides and finally to give recommendations that will help foster best practices and minimize cost of production to users as well as minimize effects to human health and the environment.

To meet our purpose, we carried out mainly desk study that allowed us to collect, analyze and summarize information from different sources such as internet search engines (mainly www.google.com), library of the Institute of Agricultural Research for Development—IRAD and that of the African Research Centre on Bananas and Plantains—CARBAP), consultation of some national experts especially those at the Phytosanitory Department of the Ministry of Agriculture & Rural Development (MINADER), and Whatsapp groups of related professionals. The information collected were mainly primary research (peer-reviewed manuscripts published in journals) as well as scientific reports or articles in conference proceedings or annual reports. We also carried out secondary literature review from news bulletins, magazines, and books. Review focus on all these sources was on the following aspects; the agricultural sector, sources of insecticides, registration procedure & list of registered insecticides, insecticide application methods & associated Malpractices, different intoxications or poisonings resulting from malpractices, and alternatives to the use of synthetic insecticides.

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2. The agriculture sector and agro-ecological zones

2.1 Geographical location & regions

Cameroon is a country located at the crossroads of West and Central Africa with a surface land size of 475,440 km2 [1] and a population of about 22.71 million inhabitants. It is bordered by Nigeria, Chad, Central African Republic, Equatorial Guinea, Gabon and Republic of Congo to the West, Northeast, East, and South respectively. Cameroon lies on the Bight of Bonny coastline, which is part of the Gulf of Guinea and the Atlantic Ocean [1]. Cameroon is called ‘Africa in miniature’ because it is characterized by a richly diversified natural environment such as mountains, desert, rain forest, savannah grassland and oceanland. The country consists of three main natural regions [2].

  • The southern forest (including the regions of Centre, East, Littoral, South and South West) is situated in the maritime and equatorial zones

  • The western highlands charatristize (covering the regions of West and North West)

  • The Sudano-sahelian north (covering Adamawa, North and Far North) (Figure 1)

Figure 1.

Different regions (a) and agroecological zones (b) in Cameroon.

2.2 Agro-ecological zones

The natural regions in Cameroon are divided into five agro-ecological zones (Table 1 and Figure 1) each characterized by dominant physical, climatic, and vegetative features.

Agro-ecological zonesRegionsAltitude (m)Rainy days/yearRainy months/yearRainfall (mm)Mean annual temperature (range)Main crop and animal production
Sudano-SahelianNorth and Far North250–50090–1203–5500- 90028°C (7.7)Maize, millet-sorghum, rice, cowpea, soybean, onion, sesame, fruits, cotton, cattle and small ruminants
Sudano-Guinean (high Guinea savannah)Adamawa500–1500110–15071500–180023°C (6.4)Maize, yam, cassava, sweet potatoes, rice, cotton, cattle, pig, small ruminants, poultry birds
Western highlandsWest and North West1500–2500175–2207–91800–240021°C (2.2)Maize, beans, potatoes, rice, sweet potatoes, vegetables, coffee, pig, poultry, cattle, small ruminants, fisheries
Humid forest (monomodal rainfall)Littoral and South West0–500180–2409–122000–11,00026°C (2.8)Banana, plantain, cassava, cocoyam, sweet potatoes, maize, vegetables, cocoa, coffee, oil palm, rubber, fruits, poultry, pig, poultry birds, small ruminants, fisheries
Humid forest (bimodal rainfall)Centre, East and South400–1000125–1757–91500–200025°C (2.4)Plantain, cassava, banana, maize, cocoyam, sweet potatoes, cocoa, oil palm, rubber, coffee, maize, cocoa, oil palm, fruits, poultry, pig, fisheries, small ruminants

Table 1.

Agro-ecological of Cameroon characteristics, geographical features, rainfall patterns and major crops cultivated and animal species reared (source: authors compilation).

2.3 Importance and production systems

The economy of Cameroon relies mainly on agriculture, with main export crops such as cocoa, coffee, cotton and banana. On an average about 47 million hectares of Cameroon’s land are used for the agricultural sector [2]. It estimated to be less than 5% of the entire territory; moreover, the exploitation of forestry, mining and fisheries represent an additional contribution to the economy of the country. Agriculture in Cameroon is currently employing about 70% of its workforce and providing 44% of its gross domestic product and 30% of its export revenue [1]. The different production systems practiced in the country are:

2.3.1 Dry farming and terracing

These are commonly practiced in the western highlands of Cameroon. Terracing is practice across steep-slop banks on the western highlands with main crops cultivated such as plantains, yams, and potatoes. Dry farming system is practiced along the few fertile gentle slopes and in localities of undulating reliefs [3].

2.3.2 Intercropping and mixed cropping

These are practiced mainly by smallholder farmers. The practices differ from one agro-ecological zone to another but many characteristics of these practices are the same nationwide. Intercropping/mixed farming is mostly carried out on small farm sizes, generally those <2 hectares. Most of the intercrop mixes contain one leguminous crop. Crops intercrops are selected based on their importance for household consumption and market. While there are cases where food crops are intercropped with cash crops, the practice is predominantly carried out by food crop farmers [4]. Some of the farmers grow more than two crops on the same land during one growing season, especially those cultivating on a land size <1 hectares [3]. Some of such farms also have one or more livestock.

2.3.3 Crop rotation

This is the practice of planting different crops sequentially on the same land to reduce the spread and rapid attack of crops by pests and diseases. The crops also differ from one agro-ecological zone to another.

2.3.4 Mono cropping

This is commonly practiced by large scale farmers >5 hectares. This cropping system is mostly industrial agricultural institutes such as CDC, PAMOL, SOCAPALM, Tole tea etc. where they cultivate crops like palms, banana, tea, rubber etc.

2.4 Main constraints in the agricultural sector

Like most developing countries, the agricultural sector in the country faces lots of constraints; (i) poor farm-to-market roads, (ii) insufficient access to finance, (iii) most are small farms still using rudimentary tools, (iv) most of the smallholder farmers have not been trained on good agricultural practices, (v) insufficient links to market and market information, (vi) insufficient and low standard transformation/processing of commodities, (vii) pests and diseases are a major constraint, (viii) most of the smallholder farmers misusing agrochemicals.

Biotic constraints (pests and pathogens) are seriously hindering the crop production, resulting to pre-harvest losses, post-harvest losses and lower yields. Arthropod pests especially insects are the most common and serious group causing damage to crops. Most damaging insect Orders are Coleoptera, Lepidoptera, Hemiptera, and Diptera. Most mentioned group of disease-causing agents are fungi and viruses. Severity of the pests and diseases varies with the crop and crops hardest hit by diseases are cocoa, tomatoes, banana/plantain, onions, sorghum, maize, pineapple, cucumbers, pepper and water melons while those hardest hit by pests are cocoa, tomatoes, maize, groundnuts, bananas/plantains, sorghum, millet, cotton, pineapple, coffee and cucumbers.

The different agro-ecological zones are faced with biotic and abiotic constraints that affect the agricultural productivity. Pests are mainly from the arthropod, vertebrate, mollusk, weeds and nematode groups of living things. Disease-causing pathogens are mainly fungi, viruses and bacteria. For cocoa, black pod; capsids; rodents and primates reported as the main pests/diseases. Corm borer weevils, mealy bugs, aphids, snails, black sigatoka, banana bunchy top disease and Banana streak virus for bananas/plantains; blight, fruit flies, white flies, aphids and mole crickets for tomatoes, peppers, and African nightshade; fall army worm, stem borers, snails, rust and maize weevil for maize; boll worm for cotton; bruchids for cowpea; thrips and mildew for onions, leaf miners for oil palm, grasshoppers, caterpillars, aphids and whiteflies also attack lots of traditional African vegetables.

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3. Sources of insecticides and purpose

3.1 Definition

Insecticides are agrochemicals in the pesticide family used to control insects by killing them or preventing the establishment or proliferation of those considered harmful. They play an important role in agriculture and public health by improving the yield and productivity of crops caused by pests and by reducing the rate of vector-borne diseases by killing or affecting growth and development of vectors such as mosquitoes, houseflies, tse tse flies, sand flies, cockroaches, etc. They are pesticides formulated essentially for repelling, killing, harming or mitigating insects from crops and other agri-food sources such as ranches, poultry farms, etc. Insecticides work differently based on their mode of actions; some disrupt the nervous system, whereas others damage the exoskeletons, others repel or control them. Insecticides application helps in managing and mitigating insects; thereby guaranteeing crop protection and preventing yield loss, they are the main weapons against insects in Africa. Insecticides are widely used in Cameroon by farmers and traders to protect their plants and products during production and post-harvest storage [5].

3.2 Insecticide supply routes

There are two main supply routes in Cameroon—a legal and an illegal supply chain. Pesticides (including insecticides) are imported mainly from France (30.9%), Switzerland (14.0%), Norway (5.7%) and the USA (5.1%). Other countries (such as Germany, China, and India) supply 16.6% while 27.7% were of unidentified sources. Pesticides are imported by local companies to large distributors and then distributed to chemical retailers (95% of all pesticides) or to farmers’ societies (5%) [6].

Cameroon does not currently produce any insecticides for crop protection, timber protection and public health uses, but repackaging is practiced by some distributors [7]. Consequently, all national demand for insecticides is met by imports. In Cameroon, the quantities of pesticides imported are undergoing a clear evolution; from 960 tons in 2015 to 1163 tons in 2019 [8].

3.3 Main dealers of insecticides

There are about 13 recognized large companies that carry out the majority of insecticide and other agrochemical imports into Cameroon although the major companies are: FIMEX International SA, AGROCHEM, ARYSTA Life Science, JACO, AFRICAWARE, ADER, BASE-F, Syngenta and YARA (Ministry of Agriculture & Rural Development). These main private companies operating in the phytosanitary business are mostly grouped within the association CropLife Cameroon, an international association of pesticide companies whose mission is to promote the availability of quality pesticides within the country. CropLife’s advocacy role involves financial support and regular sensitisation of pesticide import and distribution companies to conduct their activities in a manner that takes into account national and international regulatory requirements in order to ensure the promotion of appropriate health, safety and environmental protection measures for all those who may be directly or indirectly affected by their activities.

The responsibility of the distributor is his/her obligation to answer for the act of making available to the end user plant protection products that have safety and quality standards. Law No. 2003/003 of 21 April 2003 on plant protection stipulates that the distributor must verify that the plant protection products are registered or have a valid Provisional Sales Authorization (PSA) in Cameroon. In order to meet this expectation, he must confirm that the product of standard (formulation, mode of action and type or family of products, he must be able to distinguish the products, which means he must know how to read the label and has adequate training). The regulations stipulate that the technician in charge of pesticide distribution must have been trained by an approved agricultural training institution. Although the distribution of phytosanitary products is an economic activity, the technician must be able to give technical advice to his clients.

3.4 Distribution of insecticides in Cameroon

The distribution of pesticides is subject to strict rules and the distributor must be registered in the MINADER database. Article 24:(1) of Law No. 2003/003 of 21 April 2003 on plant protection stipulates that the marketing of plant protection products in bulk or on display is prohibited. The same applies to the possession of obsolete plant protection products [9]. Small scale distributors or retailers buy from the large companies. Some of these large companies put in place measures that allow the retailers to be registered before being allowed to get products. Sellers mainly buy their supplies from large authorized distributors. In addition to vendors, permanent retailers operate agricultural input sales outlets in the main markets of Cameroon. In addition to permanent retailers, hawkers do sell in several markets at once, traveling from one market to another.

In 2017, a pilot study on the harmful effects of agricultural pesticides on human health and the environment in some regions of Cameroon, carried out in five different zones representing the main agricultural production basins of the 5 agro-ecological zones indicated that although all the retailers claim to get their supplies preferentially from approved distributors, the majority of pesticide sellers found in the markets do not have any sales authorization as required by the Law and are not listed in MINADER’s data base. This creates an informal market for agricultural pesticides (including insecticides). Some of them sell in bulk and on stalls. This creates a situation where unregistered and expired products are found in the markets (Figure 2) [10].

Figure 2.

Photo of a typical store where pesticides are sold. (a) and (b) Pictures of pesticides of retailers salers. (c) Picture of typical store where pesticides are sold (source: Pouokam, 2016; Cameroon Tribune 2021).

3.5 Importance of insecticide

Insecticides are widely used in the country by chemical retailers, farmers’ organizations, farmers and post-harvest traders to protect their plants and products during production and post-harvest storage. The importance of plant protection products in agriculture is justified by their impact on increasing crop yields (cereals, banana and plantain, pineapple, tomato, rubber, cocoa, wood, vegetable and fruit crops, cotton, sugarcane, carrots, rice, oil palm, maize, coffee, logs, stocks, cabbage) by an average of 30–40%, reduction of damage caused by pests and diseases which can reach 30–50% of losses in the field or after harvest [11, 12].

Insecticides are applied to the environment to reduce the population and damage caused by insect pests below a level that cannot cause economic damage. They therefore play an important role in agriculture and public health. In Cameroon, public health, insect pests and/or vectors of importance include mosquitoes, house flies, cockroaches, bed bugs, midges. Insecticides are also used to control urban pests such as beetles and termites destroying ceilings and other furniture of houses. The use of insecticides has an advantage in terms of economic efficiency and improved human health and welfare (Figure 3).

Figure 3.

Sample damage caused by pests and diseases: photos of bed bug and its effects on humans, fall army worm on maize leaves, cocoa black pod disease and mold on maize cobs.

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4. Registration procedure and analysis of registered insecticides

4.1 Registration procedure

4.1.1 Legal and institutional framework

In Cameroon, laws exist that guide the distribution and appropriate use of agrochemicals especially synthetic pesticides. These laws concern the use or misuse of pesticides and align with certain international conventions (e.g. Stockholm, Rotterdam, International Plant Protection) of which Cameroon is a signatory. One important law is No. 2003/003 of April 2003 concerning phytosanitory measures or crop protection practices. According to this law, pesticides are substances or group of substances (example insecticides) used to destroy or control below threshold levels crop pests, disease vectors, species that are undesirable to plants and animals or negatively affect the entire value chain of agricultural products. Pesticides can cause harm to humans, animals or the environment if not properly used or disposed.

Also, some pesticides residues or phytosanitary products may accumulate in organisms after repeated applications andthis may cause diseases and subsequently death. For this reason, laws and decrees are usually published to regulate the sale, storage and use of all phytosanitary products that enter the Cameroonian markets. In relation to this, some products or active ingredients that are identified as toxic by the competent authorities have been banned and removed from the market. This Law documents the principles and rules governing plant protection in Cameroon. Generally, pest control is carried out through (i) the development, adoption and adaptation of standards, (ii) the prevention and fight against pests of plants and plant products, (iii) theuse of pesticides that are safe to human and animal health and for the environment, (iv) the dissemination and popularization of appropriate techniques for plant protection, (v) control of the import and export of pesticides.

Furthermore, chemical treatments are applied in accordance with good agricultural practices issued by the competent authority in order to protect human and animal health and protect the environment from hazards arising from the presence or accumulation of pesticide residues. Any natural or legal person wishing to perform phytosanitary treatments in a professional capacity must first be approved by the competent authority. In addition, only registered pesticides or those with a provisional sales authorization must be imported, distributed, packaged or used in Cameroon. All plants, plant products, soil or growing medium, bodies and biological pest control products are subject to: phytosanitary inspection regardless of their place of production, multiplication and storage and their mode of transport; control during their manufacture, import, export, packaging, distribution and use.

4.1.2 Procedure for registration in ECCAS and Cameroon

The procedure for registration of pesticides in Cameroon is almost the same for the countries in the Economic Community of Central African States (ECCAS) region although there might be some slight differences. This procedure has been endorsed by the Central African Pesticides Committee (CPAC) in collaboration with all the ECCAS countries [13]. The procedure involves three main steps:

Step 1: Submission of a complete registration application file to the Permanent Secretariat of the Central African Pesticides Registration Committee (CPAC) together with payment of an examination fee. The file is then forwarded to experts for examination.

Step 2: After examination of the file, CPAC may decide to either (i) register the pesticide in Central Africa region for 10 years; (ii) grant a Provisional Sale Authorization (PSA) for a two-year period pending further studies; (iii) retain the file under study pending additional information or (iv) refuse to register the pesticide. A registered pesticide is issued a unique number that is valid for all CPAC member states.

Step 3: The CPAC Permanent Secretariat transmits the results of the deliberation to the applicant and to the member states, and publishes the list of registrations and PSA in CPAC periodical.

The pesticide registration application file comprises all information necessary to assess the efficiency of the pesticide and the potential hazards that such a pesticide might pose to humans, non-target organisms and the Central African environment as a whole. It includes all information on the identification and the physico-chemical properties of the product and the active ingredient, toxicology, effects on the environment and wildlife, the residues as well as information on the safety measures on the use of the product [13]. The file includes the following items submitted in French or English:

  • An application for the registration of a commercial product;

  • A specification sheet;

  • A technical package;

  • An analytical file;

  • A toxicology file;

  • The original label or scale model;

  • A reference sample of the active ingredient(s) contained in the commercial product and a sample of the commercial product;

  • A registration certificate in the country of origin.

The registration criteria comprise of:

  • an administrative information (name and address of applicant, patent holder, manufacturer of formulation and manufacturer of active ingredients);

  • identity of the formulation (brand name of the formulation, names and proportion of active ingredients, etc.);

  • identity of the active ingredients (ISO, purity, proportions of additives, etc.);

  • intended uses (type of pesticide, target crops, countries with similar ecologies where the formulation is registered).

The files include physico-chemical, biological efficacy, analytical, toxicology, environmental, residue and packaging and labeling files. The files shall comprise only abstracts of these studies. The complete studies is made available to CPAC on request.

Labeling of pesticide containers is designed as a means of attaining a high level of communication between the pesticide dealer and the user. Therefore, it should be clear and concise and should contain fundamental data for the use of pesticide in complete safety and with guaranteed efficiency throughout its life span. The label should describe the content, present a clear visible indication of the hazard, direction for the sound use of the content, name and address of manufacturer as well as manufacture and expiry dates. Additionally, a specification sheet or technical notice should be enclosed to supplement information on the description of active ingredients, direction for use and necessary precautions.

The importation, sale and use of pesticides in Cameroon are regulated by Law No. 2003/003 of 21st of April 2003 regarding phytosanitary protection, particularly in section 1 of chapter III of the law. Here, it is clearly stated that only registered phytosanitary products or products that have a Provisional Sale Authorization (PSA) could be imported, distributed, conditioned or used in Cameroon. These products are supposed to be marketed and used only in their original packaging material. In addition, equipments used for the application of pesticides are supposed to respect specific norms. To this, their production, importation and distribution in Cameroon are regulated by the law. Interested persons are supposed to submit an application file for certification of the equipment to the National Commission for Homologation of Pesticides and the Certification of phytosanitary equipment (CNPHCAT) and must pay an evaluation fee. Registration is a process at the end of which a competent authority approves the importation, distribution and use of a product after results of scientific analysis indicate that the product is effective, does not present any risks or danger to humans, animals or the environment when used as recommended.

The regulation binding the registration of pesticides in Cameroon is the same for the countries in the ECCAS. This regulation was put in place by CPAC in collaboration with all the ECCAS. The regulation clearly indicates that a pesticide may not be homologated unless its formulation conforms to the following criteria:

  • It is sufficiently effective against the target organism; has no phytotoxic effect, it is not harmful to humans and wildlife not initially targeted and has no negative effects on the environment.

  • It has acceptable biological efficacy.

  • Established experimental and analytical methods can determine the components, impurities and residues of the pesticide.

  • Maximum residue limits for agricultural products intended for human consumption and subject to homologation.

Where most of the above criteria are respected, a Provisional Sale Authorization (PSA) is granted, which will be valid for a limited period of 2 years nonrenewable.

Registration of a product involves the following:

  • Chemical analysis of a sample of the product conducted in an accredited laboratory;

  • Biological efficacy tests conducted by a research institute during one or two cropping seasons;

  • Pre extension tests conducted by plant protection services of the Ministry of Agriculture and Rural Development over at least one cropping season;

  • Combined tests of bio-efficacy and pre extension for at least one cropping season.

Individuals or group of persons who intend to submit a phytosanitary product for registration are supposed to deposit an application file to the National Commission for Homologation of Pesticides and the Certification of phytosanitary equipment (CNPHCAT) and must pay an examination fee. This commission is created in MINADER but includes one or two members from other government ministries such as Ministries of Scientific Research and Innovation, Higher Education, Public Health, Animal Husbandry and Fisheries, Environmental Protection and Nature Protection among others. The chair of the commission is the Minister of Agriculture and Rural Development as stated in chapter IV of the Prime Ministerial Decree no. 2005/0772/PM of 06 April 2005. This decree also provides details on procedure for submission of a phytosanitary product for homologation in its chapter II.

4.2 Analysis of registered insecticides

The list of pesticides registered in Cameroon as of 04 March 2021 by the National Commission for the Homologation of Phytosanitary Products and Certification of Treatment Equipment housed within the Ministry of Agriculture and Rural Development for the control of crop and wood pests and for public health uses is estimated at nearly 900 pesticides, 90% of which are pesticides and 10% growth regulators [14, 15]. Of this list, insecticides represent about 34% of the total registered pesticides. It is subject to periodic renewal, but provides a framework that is binding on all at the national level. The toxicological class of insecticides according to the World Health Organization classification, indicate that 2% are in Class Ia (extremely dangerous) for use in food storage; 3% of registered insecticides are in Class Ib (very dangerous), including insecticides and nematicides used to treat cotton, tomatoes, plantains, vegetables; 32% in Class II (moderately dangerous); and 63% in Class III (slightly dangerous) [14].

Of the 311 insecticides registered by March 2021, mostare registered for use on cotton (24.4%), tomatoes (22.5%), cocoa (21.9%), and public health (13.2%) (Figure 4). Table 2 shows the different sectors on which insecticides are registered, major group of insecticides and their percentages, target pests and examples of main active ingredients.

Figure 4.

Distribution of insecticides registered in Cameroon.

SectorTarget pestMajor groups of insecticidePercentage of the groupExample of most registered active ingredient of the group
Banana/plantainCorm borer weevils
Nematodes
Neonicotynoid37.5 (6/16)Imidaclopride
Thiametoxam
WoodsXylophage insectsDifferent types mainly combinationsThiacloprid
Boric acid
Magnesuim phosphide
CocoamiridsNeonicotynoid80.9 (55/68)Imidaclopride
Thiametoxam
Acetamiprid
CoffeeCoffee berry borersNeoticotynoid100 (1/1)Imidacloprid
Lamda cyahothrine
SugarcaneTermitesPheny pyrazole100 (1/1)Fipronil
CabbageCaterpillarsMicrobial100 (1/1)Bacillus thuriengensisvar. kurstaki
CottonBoll wormIvermectine
Pyrethroid
60.5 (46/76)Emamectine benzoate
Cypermethrine
Vegetable cropWhite flies
Thrips
100 (1/1)Abamectine
Stored cropsStore pestsOrganophosphates in combination83.3 (10/12)Pyrimifos-methyl
Permithrine
Aluminum phosphide
Public healthMosquitoes
Midges
Pyrethroid70.7 (29/41)Transfluthrine
Lamda cyahalothrine
Alpha cypermethrine
MaizeFall army worm
Stem borers
Ivermectine42.9 (6/14)Emamectine benzoate
Oil palmLeaf minerOrganophosphafe100 (1/1)Thioryclam hydrogenoxalate
TomatoFruit flies
White flies
Pyrethroid77.3 (58/75)Cypermethrine
Lamda cyahalothrine

Table 2.

Target pests and major group of insecticides and active ingredients registered for different sectors in Cameroon.

From Table 3, 11 commercial insecticides are registered with characteristics of highly hazardous pesticides (HHPs) comprising 07 active ingredients according to World Health Organization. These HHPs are registered only for banana/plantain, woods, cotton, stored products, and tomato. Cocoa with 68 registered insecticides has no active ingredient which is HHP.

SectorCommercial nameActive ingredientsToxicological class*
Banana/plantainCounter 15 FC
Moking 10 G
Vykingran 10 G
Terbufos 150 g/kg
Ethoprofos 100 g/kg
Oxamyl 50 g/kg
Ia
Ib
Ib
WoodsMagtoxinMagnesium phosphide 660 g/kgIb
CottonAlmec 036 ECAbamectine 36 g/LIb
Stored productsAladin
Magtoxin
Phostoxin
Aluminum phosphide 56%
Magnesium phosphide 660 g/kg
Aluminum phosphide 56%
Ia
Ib
Ia
TomatoAbamet 18 EC
Tetrakill 20 EC
Furadent Super 10 G
Abamectine 18 g/L
Abamectine 20 g/L
Oxamyl 10%
Ib
Ib
Ib

Table 3.

List of highly hazardous insecticides registered in Cameroon.

According to World Health Organization.


Only four biocontrol agents have been registered (Bacillus thuringiensis kurstaki, B. subtilis, emamectine benzoate, and a nuclear polyhedrovirus). These microbial biocontrol agents are to be used mainly on caterpillars infesting cabbage and maize as well as for public health. So far, no botanical insecticide has been registered in Cameroon although several are used by farmers—including neem aqueous extracts, neem oil, wood ash, pepper extracts, Piper spp. powder, and water extracts of tobacco and hemp.

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5. Insecticide application methods and associated malpractices

5.1 Application methods

The mode of application of insecticides is very important for optimizing their functions especially as less than 1% of these applied insecticides get to their target organisms [16, 17]. The over-reliance on chemical pesticides in combating pests throughout the world cannot be emphasized, yet it remains the most efficient, cheap and most accessible control mechanism in controlling pests [18]. Danquah et al. [19] reports cases of organochlorine insecticides residues in Cameroon, Ghana and India within vegetable cultivation, water resources and soil sediments which results largely due to application malpractices.

5.1.1 Current insecticide application methods widely used in Cameroon

The desired results of any insecticides can be achieved based on the appropriate methods used and also respecting the time factor. Methods of application varies depending on the nature of the insecticide, their formulation, the soil characteristics, the pests and the availability of clean water [20]. The applications of insecticides is basically for seed treatment, soil treatment or foliar treatment. Insecticides come either in solid, liquid or powder forms, and it is these forms that dictate the methods and appliances used.

5.1.1.1 Sprayers, broomsticks and leaves

Numerous studies show that in Cameroon and Africa, more than 70% of farmers use sprayers which ranges from knapsack, to motorized knapsack sprayers and others in applying pesticides [19, 21, 22]. It is the most widely used method in the application of insecticides that comes in both powder and liquid forms requiring mixing with water before usage.

As observed with most small scale farmers, the mixing of the insecticides with water is carried out with plastic buckets ranging from 10 to 15 liters while others use their knapsacks, fetching water from nearby streams and using teaspoons, table-spoons or corks of bottles as their measuring units. These are all incorrect estimation measures that lead to either over-dosage or under-dosage of insecticides.

As reported by Christos et al. [22] some resource-poor farmers often improvise by using brooms, mesh and leaves on a wooden short stick in sprinkling pesticides mixed in buckets (Figure 5).

Figure 5.

Using manual knapsack sprayer on sweet potatoes and fuel-powered sprayer on maize at Ekona, South West Region, Cameroon.

5.1.1.2 Dusting

This is the application of powder insecticides without diluting in water, usually using a duster [22]. In Cameroon very few farmers actually know and use dusters in the application of insecticides. From observation and sampling a handful of tomatoes farmers around Buea, just one in ten farmers know about the dusting techniques and also these few could not afford the duster. These farmers improvise by mixing these insecticides with water and spray. Some farmers apply these powder insecticides with hands upon wearing gloves, without any protective equipment especially for their nostrils and mouth. This practice leads to either over-dosing or under-dosing of plants often resulting in environmental contamination and pollution. Also, farmers have been reported using their bare hands to mix wood ash and terbufos and thereafter apply the mixture on leaves of maize and vegetables such as African nightshade (Solanumspp).

5.1.1.3 Granular application

These are insecticides designed in the forms of solid granules which are made to last longer with the gradual release of the active ingredients slowly upon contact with the soil or roots of plants. In Cameroon more than 70% of the farmers interviewed apply granular pesticides with their hands without any protective, with some using empty tomato tins in spreading them upon the soil.

Most often, these tomato tins serve as their measuring instrument, and depending on the plants, some apply a tin per plantain or banana but for smaller plants like tomatoes, they use a tin for 5–10 plants.

5.2 Malpractices linked to the application methods

5.2.1 Inappropriate application appliances

Besides using sprayers, sprinklers and dusters, using of broomsticks and bundles of leaves and brushes attached to sticks and dipping in a bucket of mixed insecticides is the usual practice in Cameroon and in most other African countries [19, 21]. This leads to ineffective application of insecticides resulting in wastage and environmental pollution.

5.2.2 Application without personal protective equipment (PPE)

In Cameroon, applying pesticides without all the required PPEs is a common practice by a majority of small-scale farmers especially as no monitoring mechanism is in place to enforce usage of PPEs. In a studies conducted in Buea by Christos et al. [21] about 76.4% tomatoes farmer use inappropriate or no PPEs during the application of insecticides, while Asongwe et al. [23] shows that 95% of farmers in Bamenda Municipality do not protect themselves during pesticide applications. Rugalema and Mnyone [18] reported scenarios of insecticides sprinkling at homes with the hands.

5.2.3 Incorrect measurement and different mixtures

Farmers in Cameroon use teaspoons, corks of beer bottles, or corks of containers, together with empty liters as their measuring units for insecticides. Using these listed items as their measuring units most often results in inappropriate measurement of pesticides that automatically results in environmental pollution and possible the contamination of farmers themselves.

Usually water is fetched in any nearby stream or river irrespective of the source or quality and more recently farmers have dug wells where they fetch water for watering their crops especially during the dry seasons with the same buckets used in mixing the insecticide.

Different concentration of different insecticides with varying active ingredients are usually mixed and used in managing insecticides, especially when the pests affecting the plants is unknown. According to Tarla et al. [24], during the rainy seasons farmers in Foumbot apply pesticides as often as twice a week and when the rains are at their peak, their fields are treated thrice a weak. These frequency of treatment overloads the environment and compromises on the quality of the plant with residues.

5.3 Factors affecting Insecticides malpractices

It is without doubts that pesticides have greatly increased crop productivity and simultaneously contaminated and polluted our soils and water resources, and also affecting our health. The technology used for their application remains hugely remote and archaic in most parts of Africa, particularly Cameroon, and it is the cost for the massive wastage and unnecessary environmental pollution. Some of the main factors affecting insecticides application malpractices include;

5.3.1 Knowledge of farmers

Many of the malpractices surrounding the safe usage and handling of pesticides is due to the fact that a majority of farmers including vendors have not had any formal training or technical support on the judicious use and safe handling of pesticides; Sonchieu and Blandine et al. [25, 26] pointed out that educational levels is the factor affecting knowledge, attitude and overall practices about pesticides usage.

5.3.2 Equipment cost and maintenance

Generally, spraying equipments in use are often in poor conditions due to lack of proper maintenance and the cost of buying original of these equipment or their parts is expensive for majority of these farmers. As reported by Abhilash and Singh [27] a large number of farmers never change sealing washers in their equipment and this is equally true for Cameroon, where most farmers share equipment without any maintenance knowledge on these equipment besides controlling the nozzles for faster application which does not necessarily lead to efficiency.

5.3.3 Repackaging or no labeling/or labeling in different languages

In Cameroon, using of pesticides without labels is a practice by vendors for selling banned products [21, 26]. In some cases, repackaging of pesticides in small quantities is to meet customer’s demand due to the high cost in purchasing the entire container that is usually more than the amount required, thereby resulting to packaging in smaller containers without labels.

There are also products that are package in the Chinese and French, with little or no English language making it difficult for the farmers to follow the instructions and without proper guidance on usage there is bound to be malpractice.

5.3.4 Weather conditions

In order to maximize the best results possible from pest control mechanisms, accurate timing in pesticides application is paramount [27]. Unfortunately, Cameroon does not have reliable meteorological stations to provide farmers with information related to weather conditions and this situation has been compounded by the changing climates. This makes it difficult for small-scale farmers to accurately apply insecticides in a timely manner that will be most beneficial for plant growth. According to Balasha and Nsele [28], about 60% of farmers apply insecticides during the early mornings and late evenings from about 4–6 pm, with a handful applying irrespective of the time as it is the case observed in Wotutu area where farmers apply more pesticides after the rainfall had washed the previous pesticides about an hour after application.

5.3.5 Inappropriate concepts and economic pressure

In Cameroon, farming is looked upon as the last resort for many people especially cultivation of vegetables like tomatoes, cucumbers, and watermelons so as to make some fast profit. Yet in order to achieve optimum results these respective endeavors it requires mastery, so most Cameroonians believe more utilization of pesticides and chemicals automatically translates to high yields; thereby over-reliance and abusive use of pesticides is practiced, as it is the case reported by Tarla et al. [24] that pesticides use does not always adhere to recommended safe practices [29].

Any desired results with regards to pesticides can only be guaranteed by properly respecting the guidelines of the producer and timing too is of the essence. Unfortunately application methods still depends on many variables such as the nature of the insecticide, its formulation, pests to be controlled, application site, water availability and training of the farmer, without of any these factors in place malpractice is most likely to occur.

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6. Intoxications resulting from malpractices

Intoxications or poisonings resulting from insecticides are mainly the result of malpractices at the level of agrochemical companies, retailers, and farmers [24, 30]. Highest poisoning cases reported for Littoral and followed by South West Region. These are then followed by North West, West and Centre Regions while the least is from the Northern Regions (Adamawa, North and Extreme North). Highest cases from Littoral and South West is not surprising because very large cocoa and banana plantations are found in these Regions and these two crops are noted for their intensive use of pesticides especially insecticides and fungicides. In addition, there are also many vegetable farmers who cultivate to meet the demands of Douala—the economic capital found in the Littoral Region and near to the South West Region. To have high yields and high quality crops, these farmers use much insecticides and therefore possibilities of misuse and ultimately intoxications.

The crops most implicated for these poisonings are tomato, cotton, banana, cabbage, lettuce, onion, African nightshade, and cocoa while the most implicated insecticides are terbufos (Class Ia), ethoprofos (Class Ia), cypermethrine (Class II & III), chlorpyriphos-ethyl (Class II), combination of lambda cyhalothrine & imidacloprid (Class II). Although the signs/symptoms of intoxications vary with the different implicated active ingredients, the common signs and symptoms of acute intoxications reported are vomiting, abdominal pain, diarrhea, skin irritations, headaches, blurred visions, convulsions as well as rare cases of immediate death, most of which are accidental and occupational. The most common routes of exposure is the skin and respiratory tract. Most of the health personnel have no training or knowledge on recognizing and managing intoxications. From their responses, except for one case of suicide attempt, all cases of intoxications mentioned in the health centres or hospitals are accidental.

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7. Alternatives to the use of synthetic insecticides

Apart from their cost, pesticides have a significant impact on human health, wildlife (terrestrial and aquatic) and the environment (soil and water pollution, etc.). Pesticides are often of poor quality or illegal, due to the low level of control of sales and distribution channels, and are generally misused because farmers are poorly trained in their use and have little knowledge of pest biology and ecology. Cameroon produces several agricultural commodities for export and domestic consumption hence this has increased the rate of application of inputs such as pesticide to help protect the crops from pests and diseases. Chemicals continue to be the main tools to protect crops during field and storage in spite of the deleterious effects as a result of malpractices.

Generally, the pest management practices reported by researchers and farmers include mainly use of synthetic pesticides and their alternatives such as cultural practices, botanical pesticides, use of biological control agents and the use of resistant/tolerant varieties. Of all the alternative pest management techniques, cultural practices and use of plants with insecticidal properties are the most common. Use of botanical insecticides is very common for cocoa, tomatoes, and stored products (e.g. maize, beans, cowpea). Sanitation, manual weeding, use of traps, and pruning are the most common cultural practices for field crops while use of containers with tight-fitting lids or bags is most common practice to protect stored products such as grains of maize, beans and cowpea.

In Cameroon, farmers depend on the use of synthetic insecticides to reduce crop losses due to insect pest, increase crop production, and urge to meet up with the high demand for agricultural products [25, 31]. However, over dependence and inappropriate applications of synthetic insecticides has led to harmful effects on the environment and human health [32]. These effects are numerous such as disruption of the normal functioning of the ecosystem, toxicity for a wide range of non-target organisms including humans and a high tendency to accumulate in the environment [33]. In addition to these, there is also the problem of pest ecological backlashies such as resurgence, replacement, and resistance. Most insecticides easily become ineffective due to the development of resistance by the insect pest. In order to minimize or completely eliminate the challenges posed by these chemicals, many researchers have carried out a number of researches in an attempt to find sustainable alternatives to replace synthetic insecticides [32]. Numerous efforts have been undertaken by IRAD, CARBAP, Universities and some International organizations like IITA and CIRAD to search and evaluate efficacies and effectiveness of alternatives to synthetic insecticides for the management of insect pests. Alternatives to synthetic insecticides include techniques such as:

  • Crop rotation

  • Host plant resistance

  • Physical and mechanical control

  • Botanical insecticides

  • Biological control agents

7.1 Cultural control methods

Cultural techniques for pest management involves the manipulation of the environment or implementation of preventive practices with the aim to reduce pest population and their damages [32].

7.1.1 Intercropping

This is the practice of increasing crop diversity by growing more than one plant species in close proximity in a field to overcome insect pest outbreaks associated with monocultures [34]. Tanyi et al. [35] used this system of intercropping beans and maize together with use of extracts of Piper spp. to manage fall army worm in the Buea municipality. Most smallholder farmers have diverse cropping systems and therefore do not have much insect pest problem.

7.1.2 The use of Insect resistant plant varieties

Although the use of synthetic pesticides is usually effective, most pesticides easily become ineffective due to the development of resistance by the weevils or insects [32]. Cultivation of plant varieties which are resistance to insect attack minimizes the need for insecticide applications [32, 34] For cocoa, resistant/tolerant varieties used are IMC60, Catongo Trinitario, Playa Alta2, SIC5, SNK614. For tomato, use of improved or tolerant varieties such as Dona F1, Heinz 1370, Fline Mecline and Mobo line. For bananas/plantains, use of tolerant varieties such as CRBP 039, FHIA 21. For cotton, use of Bt-Cotton, use of tolerant/resistant varieties such as NGT115, SARC-1-57-2, KVX-165-14-1, LORI, IT97K-556-6-IITA. The use of resistant/tolerant varieties such as the local variety VYA-Cowpea.

7.2 Biological control methods

Biological control is an environmentally sound and effective means of reducing or mitigating pests and their effects without having to spray the plant with chemical insecticides but rather through the use of natural enemies. Biological control agents of insect pests are in three groups namely; predators, parasitoids and pathogens. There are three primary methods of using biological control agents in pest control programs which are the importation, augmentation and conservation methods.

7.2.1 Entomopathogens

Although not widely applied on agro-ecosystems in the country, some entomopathogens have been evaluated on research stations/sites. Trichodermaspp. has been used in the biological control of cocoa brown rot caused by Phytophtora infestanswhile endophytes have been evaluated for crop protection purposes [36, 37, 38]. Pathogenic organisms such as entomopathogenic fungi (Beauveria bassianaand Metarhizium anisopliae), entomopathogenic nematodes (Steinernemaspp. and Heterorhabditisspp) and endophytes (nonpathogenic Fusariumspp) have been tested against Cosmopolites sordidus(banana borer weevil) [32]. After the application of these biological agents, results revealed that entomopathogenic fungi and nematodes are effective in controlling adult weevils while endophytes effectively control the immature stages of the pest mainly at the level of the laboratory/shade houses [32]. Emamactine benzoate and oxymatrine are used for stem borer and fall army worm (caterpillars) management on maize while sex pheromones are sometimes used to capture and kill adult moths. For cotton, emmamectine benzoate, spinosad are used to control the cotton bollworms (Helicoverpa armigera). Metarrhizium anisoplaeused on flower bud thrips on cowpea.

7.2.2 Predators and parasitiods

In banana/plantain farms, some farmers encourage the trap-jaw ant (Odontomachusspp) as they are convinced these have excellent searchability and feed on eggs, larvae and pupae of C. sordidus. In the Northern regions, where majority of the cotton farms are found, they encourage and promote survival of natural enemies: parasitoids such as Pediobius vigne, Trichogramma, Schixopyrannusand predatory mites used for the management of caterpillars on cotton. The weaver ants (Oecophylla longinoda) are usually conserved by some cocoa farmers to help reduce the population of cocoa capsids (mirids).

7.3 Plants with insecticidal properties

Several plants with insecticidal properties (mortality, repellence, development disruptor, feeding and oviposition deterrence) have been identified and their efficacies tested in the laboratory and fields. A total of 29 plant species reported as plants having some pesticidal properties and use for one or more different pests and diseases. Based on journal publications on insecticidal plants in the country, there are 29 plant species belonging to 21 different plant families of which Fabaceae (19.1%), Amaryllidaceace (19.1%), and Meliaceae (14.3%) were the most reported. Most common parts used are seeds and leaves mainly as extracts or dry powders. These insecticidal plants are usually applied in the form of ash, essential oils, powder formulations and aqueous or alcohol extracts.

7.3.1 Ash

Ash is one of the most common product used by smallholder farmers especially in the rural and peri-urban areas. The ash collected from household kitchens or burnt wood [39]. Some use only the dry wood ash while others mix fine dry soil with wood ash. Some others mix their ash with conventional insecticides such as Mocap (ethoprofos or terbufos), cypermethrine or kerosene. Some mix the ash with water or kerosene and used as sprays [39].

Most farmers in Buea Sub-Division, South West Region, Cameroon believe that applying a combination of terbuphos (Counter 10G®) and ash (from rubber plants wood and oil palm bunch residue ash) as seed treatments helps to protect suckers from the banana weevil (Cosmopolites sordidus) and stimulate plant growth better than their sole forms [40]. This mixture is mostly applied on soil around the corms or put in the planting holes before planting the plants. Sometimes ash of plant parts are used as insecticide such as the leaves of Cupressus arizonica, Eucalyptus grandis, Ocimum gratissimumand root ash of Vetiveria zizanioidesagainst Sitophilus zeamais(Coleoptera: Curculionidae) [41]. The ash of E. grandisand O. gratissimumat the rate of 0.25 g/25 g maize grains significantly reduced the number of emerged weevils but if E. grandisash is increase at 20 g/2 kg grains it significantly reduced grain weight loss and protected grains for 6 months without adversely affecting the germination of the seeds [41].

7.3.2 Essential oils

Essential oils from so many plant parts have been use as insecticide in Sub Saharan Africa especially in Cameroon. The essential oils are extracted from the seeds, leaves, bark and roots of the plant. Crude essential oils of Lippia rugosaand Hyptis spicigeraare the most promising for Tribolium castaneumbecause of their efficacy on the other life stages. They are more efficient, with 100% mortality, on larvae at early stages and young adults [42]. Oben et al. [39] reported that essential oil from dried seed powder of Piper guineensehas potentials for development as an organic insecticide against Sitophilus oryzaeL. and other pests of stored grains. This is because Pipercarene, copaene, α-caryophyllene or β- caryophyllene with insecticidal propertie [39].

The insecticidal properties of formulations based on Ocimum gratissimumessential oil and montmorillonite clay against the maize weevil (Sitophilus zeamais). The formulations based on essential oils adsorbed on modified clays is considered as alternatives to synthetic insecticides for use in storage and protection of maize grains from Sitophilus zeamaisThe insecticidal potentials of essential oils of Chenopodium ambrosioidesand Cupressus sempervirensare very effective low persistence against S. zeamaison stored maize because persistence of both oils dropped to zero within 2 weeks [43]. In some localities in Cameroon, essential oils of pericarps of ripe fruits from Citrus aurantifolia, C. limon, C. sinensisand C. reticulataare used for the development of natural biocides [44]. Azadirachta indica(neem) seeds have been widely used in the northern part of Cameroon as essential oil. A. indicaseed oils and powders from sun-dried kernels, shade-dried kernels, sun-dried seeds and shade-dried seeds seed oil was more active towards Callosobruchus maculatuson cowpea seeds and Sitophilus zeamaison maize grains [45].

Essential oils of Lippia adoensisleaves have already shown good insecticidal efficacy on Sitophilus zeamais. The essential oil of young leaves killed more weevils than that of old leaves, but old leaves were more repellent (II ≤ percent repellency ≤ V) than young leaves (0 ≤ percent repellency ≤ I). With its persistence levels of 98.47% after 96 h, the essential oil of old leaves more persistent than that of young leaves (94.66% after 96 h). The efficacy of essential oil from dry leaves of Callistemon viminalis(Myrtaceae) against Acanthoscelides obtectus(Say) (Coleoptera; Bruchidae) a major pest of Phaseolus vulgarisof stored beans in Cameroon was evaluated and the results revealed that at the end of the first day of exposure, the highest concentrations of essential oil applied to the beans (0.40 μl/g) and to the filter paper discs (0.251 μl/cm2) caused mortality rates of 72.6% and 80%, respectively. These rates increased to 97.5% and 100% respectively after 4 days of exposure.

Essential oils from the leaves of Ocimum canumSims (camphorated basil) and Ocimum basilicumL. (sweet basil) caused 100% mortality on Anopheles funestusadults at a concentration of 200 ppm for O. canumand 250 ppm for O. basilicum.

7.3.3 Powder formulation

In Cameroon some of the method of application is through powder formulation where the plant parts are dried then later grind and may be sieve or not depending on the user. These powders are sometimes mixed with other materials such as wood ash or other plants. The application is done by band placement or broadcasting depending on the farmer. For example in the western highlands of Cameroon plant materials consisting of leaves, seed and/or roots; Cupressus arizonica, Eucalyptus grandis, Ocimum gratissimum, Vetiveria zizanioides, Balanites aegyptiaca, Lophira lanceolata, Hemizygia welwitschii, Plectranthus glandulosus, Laggera pterodontaand Azadirachta indica are considered as alternatives to synthetic insecticides for the protection of stored maize grains against Sitophilus zeamais[43, 45, 46, 47] Dried ground leaves/seed powders of some spices (Syzygium aromaticum, Piper guineense, Aframomum citratumand Ocimum basilicum), leave/seed powder of Hemizygia welwitschiiand/or Plectranthus glandulosus, Azadirachta indicahave an insecticidal potential against the cowpea weevil (Callosobruchus maculatus), common bean weevil and maize, thus small-scale farmers have been using them to protect their stored-product [45, 46, 48, 49]. In the Far North region of Cameroon, powders of Hyptis spicigera(Lamiaceae), A. indica(Meliaceae) and Vepris heterophylla(Rutaceae) are mostly used as insecticides single or associated with food during storage in combination with two or three others plants to control the red flour weevil (Tribolium castaneum) [50]. The flours from Phaseolus sativumand Phaseolus vulgarisseeds are also used to protect sorghum grains against the attack of Sitophilus oryzae[51].

7.3.4 Aqueous extact

Azadirachta indica(neem) fruit reduces insects’ pest in the heading and maturation stages of rice plant [52]. The aqueous leaves, seeds, roots (aqueous extracts) of Azadirachta indica, Boswellia dalzielii, M. anisopliae, Lippia rugosa, Annona senegalensis and Jatropha curcasand their combinations are considered as potential natural insecticide in the management of thrips population on Vigna unguiculatain the fields. This would increase Vigna unguiculatayield and free environmental pollution from synthetic insecticides [53]. Aqueous extracts of Cannabis sativa, Guibourtia tessannii, Erythrophleum ivorense, Thevetia peruviana, Azadiratchta indica, Ceiba pentandra, Pachyelasma tessmanii, Nicotinia tabacum,wood ash, Chnopodium ambrosoides, Lobelia columnaris, Carica papaya, Urtica dioica, Grotolania juncea,Pepper, as well as smoke from burnt flowers of oil palm and cocoa husks are used in cocoa farms to manage capsids (mirids) and caterpillar infestations. Cupressus benthanmii, Vetiveria zizaniodes, Piper guineense, Tithonia diversifolia, Mucuna cochinchinensis,garlic, onion, ginger used on tomatoes to reduce population of fruit flies, leaf miners, white flies and caterpillars. Afromomum melegueta, Piper guineense,and A. indicaextracts with greater effectiveness against C. sordidus, mealybugs and aphids infesting Musaspp. [32]. Extracts of three Cupressus species (C. macrocarpa, C. sempervirens and C. arizonica), as well as Chenopodium ambrosioideshave been shown to have larvicidal and repellent properties against the Anopheles gambiaein Cameroon [54, 55].

7.3.5 Plant emulsions

The insecticidal properties of detergent-oil (mixture of liquid washing detergent and vegetable oil) emulsions of four plants (Lantana camara, Allium sativum, Coffea arabica,and Jatropha curcas) are used to control mealy bug infestation in banana and plantain field [40].

7.4 Integrated pest management

Integrated Pest Management (IPM) is a concept that is widely used or documented in diverse literature related to agriculture, environment and pesticides. This concept is becoming more and more popular as people become more and more conscious of the detrimental effects of pesticides and other chemicals used in agriculture, forestry and public health. According to Norris et al. [56], IPM is defined as a decision support system for the selection and use of pest control tactics singly or harmoniously coordinated into a management strategy, based on cost-benefit analyses that take into account the interests of and impacts on producers, society, and the environment. Considering this definition IPM can simply be defined as the use of all available pest management techniques or options that are compatible, cost-effective and environment-friendly.

From several discussions (especially with farmers and agriculture officers and researchers), literature and rapid observational assessments, it is clear that on the part of most farmers in the rural areas and a few in urban/peri-urban areas they are applying IPM unknowingly. These farmers have been working for long on the same pieces of land and/or on the same crops. They therefore have some wealth of information about their agro-ecosystems (the behavior of the crops, the different pests and their population dynamics, etc.). With this knowledge, most of these farmers have learnt to apply two or more techniques for managing the pest or pest complexes in their farms. They commonly apply combinations of cultural, physical and chemical options. Those who are flexible have (with the help of agriculture extension workers and researchers) added a genetic component (the use of improved and/or tolerant/resistant varieties) to their management strategy.

In addition, most farmers that are closer to research stations and the large agro-industrial plantations are having extra advantage by considering them as their role models. The farmers cultivate the same crops and put every effort to implement the same IPM strategy that these research stations and the plantations use in their farms. Apart from these hands-on experiences, the farmers (some of which are workers in these research stations and plantations) benefit from the few seminars/workshops concerning IPM for specific crops and good agricultural practices or best management practices. Such seminars/workshops are very common for crops such as cocoa, bananas, maize, cotton, and vegetables in peri-urban zones or in areas where pesticide abuse and misuse are common practices.

For the agriculture technicians/extensionists, research technicians, agric/crop protection students, and research assistants/researchers, from time to time they benefit from seminars/workshops/trainings on best management options and good agricultural practices for specific crops or pests. Most of these trainings/workshops are usually organized and sponsored by the Ministries of Agriculture and Health and/or international organizations/research centers such as IITA, CIRAD, IRAD, World Vegetable Centre, FAO, and GIZ. These organizations have played an important role in the implementation of Farmers’ Field Schools (FFSs) in some rural areas of the country. For instance, GIZ in collaboration with the Delegations of Agriculture in the South West, Centre, South and Littoral Regions have organized and sponsored FFSs in the major cocoa producing areas. In these FFSs, farmers are taught and followed up in the farms on good agricultural practices and on using of pesticides only when absolutely necessary.

In addition, texts of certain decrees give some information on how biological control and IPM should be carried out. According to these texts, IPM is to be carried out with the following aim in mind; (i) reduce dependency on pesticides, (ii) effective control on the use of pesticides, (iii) reduce the risks resulting from abusive and inappropriate use of pesticides.

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8. Recommendations to promote judicious use of insecticides

  • The decision to select a particular insecticide should be based on an assessment of the risks and benefits and the potential hazard to public health and the environment.

  • Legislation to control and regulate the manufacture, importation, distribution and sale of Insecticides should be strict. Only registered and recommended products should be used.

  • Urgent need for government regulatory authorities to monitor the use of agrochemicals in the country, to strengthen controls for effective implementation of pesticide bans and to implement rigorous control of obsolete pesticide stocks in Cameroon.

  • Raise awareness of the need for proper monitoring of insecticides in the country and develop strategies to reduce insecticide residues in food, and measures should be taken by regulatory authorities to manage the country’s stock of obsolete pesticides and regulate the use of agrochemicals in the country.

  • Training and intensive monitoring of farmers so as to effectively monitor the application of insecticides by the insecticides units.

  • Promoting safe and proper use of insecticides by producers and the general public.

  • The national pesticide registration committee should limit the registration of many commercial products with the same active ingredients and concentrations. In addition, it should also stop the registration of pesticides with Class I toxicity. Otherwise, sales and use of such insecticides should be done under strict measures.

  • The government should intensify monitoring of insecticides activities at all levels as well as ensuring sanctions to defaulters of laws, decrees or decisions.

  • Produce official and important pesticide documents in the English and French language as well as making these documents accessible to the public.

  • Set up agro-health centres for pesticides and related chemicals. Such centres to be charged with training on pesticides (use, safety measures, pesticide application management, recognizing and managing intoxications).

  • Introduce a course (Management of Pesticide Intoxications) in health/agriculture institutes/departments to teach students on pesticide basic classification, merits and demerits, use/misuse, safety measures/first aid, sign/symptoms of poisoning/intoxications, management of intoxications, international/national legislation).

  • Promote research and use of biofertilizers and biopesticides especially those made from local bioresources.

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9. Conclusions

Agriculture is an important sector in Cameroon with significant contribution to the GDP. Biotic constraints (especially insects and pathogens0 play a major role in reducing the productivity of farmers and therefore most tend to rely on use of agrochemicals such as synthetic insecticides and fungicides. Improper use of these chemicals is not only increasing cost of production but also greatly affecting the health of farmers and consumers. Although there are several conventions and laws in the country to promote best practices in the use of pesticides, the implementation is weak and this needs to be strengthened by continuous monitoring, sensitization and training of stakeholders including health practictioners.

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Acknowledgments

Institute of Agricultural Research for Development for help in providing some useful journal articles.

Conflict of interest

No conflict of interest.

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Written By

Nambangia Justin Okolle, Ekwa Yawa Monono, Amungwa Ivan Tabikam, Mambo Stephania Kinge and Magwell Pierre Fils Rodrique

Submitted: October 15th, 2021Reviewed: January 12th, 2022Published: March 27th, 2022