Abstract
Background: Resource-poor small-scale farmers often cannot afford the high prices of chemical insecticides to control pests on crops; as a result, some use botanical insecticides.
Aim: The aim of the study was to document ethnobotanical pest control methods used by rural small-scale farmers to control pests of cabbage in the Eastern Cape Province of South Africa.
Setting: 217 rural small-scale crop-producing farmers from 14 towns in the Amathole, Joe Gqabi, Alfred Nzo, Chris Hani and OR Tambo Districts participated in the study.
Methods: Questionnaires were administered to consenting farmers between July and November in 2012, using the convenience and stratified purposive sampling techniques. Data collected were subjected to descriptive statistical analysis.
Results: The majority of farmers using botanical insecticides were females above the age of 60 years. The farmers identified 23 plants, which they use in their pest control strategies against seven pests of cabbage. The annual herb Tagetes minuta L. (Asteraceae) was cited as the most commonly used herb by 47% of the respondents, followed by Chenopodium ambrosioides L. (Chenopodiceae), Aloe ferox Mills. (Asphodelaceae) and Nicotiana tabacum L. (Solanaceae). Various plant parts were used in combinations or alone in the preparation of formulations mainly against aphids, cutworms and the diamondback moth.
Conclusion: The plants, plant parts, combinations and formulations used by farmers in their cabbage pest control strategies need to be scientifically authenticated for efficacy.
Introduction
Cabbage (Brassica oleracea var capitata L.) is the most cultivated brassica crop in South Africa (Mandiriza-Mukwirimba, Kritzinga & Aveling 2016:35–44). It is widely used throughout the country in making salads, soup, ink, cabbage atchar, canned as prickled cabbage and at times frozen for later use (Department of Agriculture, Fisheries and Forestry [DAFF] 2010).
Studies indicate that cabbage contains a high content of vitamin K, antioxidants, dietary fibre, folate and several carotenoids and glucosinolates that are not found in other foods (Mithril et al. 2012:777–785). The use of the crop has been shown to reduce the risk of some cancers, especially those in the colorectal group (Ibrahim & Yusuf 2015:248–251). Other medicinal benefits of cabbage include the treatment of gout, stomach problems such as peptic ulcers and constipation, deafness, eye problems, headache, skin problems, asthma, morning sickness and hangovers (Stephen & Suresh 2015:546–561).
In the Eastern Cape Province, cabbage is one of the most cultivated vegetables (Kiribige 2014) and the crop is regarded as one of the staple foods (Mkize 2003). It is an inexpensive source of vitamins and minerals in a maize-based diet. Insect pests are some of the most significant constraints to cabbage production in the province and are often controlled with chemical insecticides (Kiribige 2014; Mlanjeni 2014; Weeks 2007). Some farmers, particularly those not participating in the government programmes, tend not to control at all although they have pest problems because of the high costs of chemical insecticides. Others use alternative methods, with a few practising indigenous pest control methods such as botanical insecticides (Mlanjeni 2014). In the province, knowledge on indigenous pest control methods is available but is being eroded because of the lack of documentation (Odeyemi, Masika & Afolayan 2006:174–176). The aim of the study was to identify and document plants, plant parts, combinations used in botanical insecticides prepared by rural small-scale farmers in the control of insect pests of cabbage.
Materials and methods
Study sites
A survey involving 217 farmers was conducted in five of the six district municipalities (Figure 1) of the Eastern Cape Province covering 14 towns, that is Amathole (Butterworth, Centane, Stutterheim, Keiskamahoek), Alfred Nzo (Mount Ayliff, Mount Frere), Joe Gqabi (Mount Fletcher, Sterkspruit), Chris Hani (Cala, Cofimvaba, Engcobo) and OR Tambo Districts (Tsolo, Libode and Port St John’s).
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FIGURE 1: Geographical map of the study sites. |
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Survey methodology
The survey was carried out between July and November 2012 using the convenience and stratified purposive sampling techniques. The proposal for the study met the ethical requirements set by the Döhne Agricultural Development Ethical Committee, and a certificate on ethical compliance was issued prior to the commencement of data collection. Every participating farmer gave a verbal consent prior to the administration of questionnaires. The farmers were interviewed individually using detailed semi-structured questionnaires.
Data collection and analysis
Data were collected on plants and plant parts used in insect pest management, preparation methods, including formulations and their combinations, and their target pests, and farmer demography. Plants used by respondents in pest control strategies were collected and identified at the Döhne Agricultural Development Institute Herbarium in Stutterheim, where voucher specimens are kept. The valid plant names were confirmed using specialised literature such as Dold and Cocks (1999:267–292), van Wyk, van Oudtshoorn and Gericke (1997) and Bromilow (1995). Pictures, live and voucher specimens were used for identification of insect pests. Where there was uncertainty, confirmation was obtained from the Albany Museum at Rhodes University in Grahamstown, South Africa. Mkize (2003) was used to verify local names of insects.
Data were analysed using descriptive statistics, whereas percentages were calculated using Microsoft Excel (2010).
To calculate the frequency of citation percentage of plants used in pest control, equation 1 was used:
Results and discussion
Demography of farmers
The majority of farmers in the study area were females with a male farmer to female farmer ratio of 9:16 (Table 1). Overall, farmers were aware of insects affecting cabbages in their cultivation areas. This could be attributed to their level of education, because only 8% of the farmers had never attended school. The experience with farming in those cultivation areas as majority were old and therefore they could have in-depth understanding of pests in their cultivation areas.
| TABLE 1: Demographic information of respondents. |
The knowledge and use of botanical insecticides differed from district to district. Older farmers from Alfred Nzo and Chris Hani districts with the mean age of 65 and 78 years, respectively, were more knowledgeable than the rest. This confirms an assertion by Odeyemi et al. (2006) that the indigenous knowledge in the province resides with older farmers.
Plants used in the control of cabbage pests
Farmers identified 23 plants used in their cabbage pest control strategies (Table 2). The majority of the plants belonged to the Solanaceae (22%) and Asteraceae (22%) families and were mainly collected from the wild (65%). The most cited and used plants were Tagetes minuta L. (Asteraceae), Chenopodium ambrosioides L. (Chenopodiceae), Aloe ferox Mills. (Asphodelaceae) and Nicotiana tabacum L. (Solanaceae), with citation frequencies of 47%, 32%, 30% and 30% respectively. The citing of these plants by the farmers is consistent with the findings of Mlanjeni (2014) in the same cultivation zones, which reported their use in the control of maize stalk borers. In addition, Odeyemi et al. (2006:174–176) reported the use of T. minuta, A. ferox and N. tabacum by farmers to control insect pests of various crops in Mthatha, Lady Frere, Queenstown, Alice, King William’s Town, Whittlesea, Bhaziya and Engcobo. Inclination towards the wide use of these plants in the province could be because of their relative effectiveness in insect pest management, ease of access compared to other plants and their multi-purpose characteristics as some are also used medicinally and in ethno-veterinary formulations and their combinations (Dold & Cocks 1999; 2000; 2002).
| TABLE 2: Plants identified and used by farmers for pest control in cabbage. |
Pest control preparation methods, formulations and combinations and their target pests
To prepare plant materials, farmers made and used different formulations and combinations (Table 3). The use of formulations and combinations by farmers in these study areas for insect pest management is consistent with small-scale farmers from other parts of South Africa and Africa. Researchers such as Sibiya et al. (2013:1790–1798), Kamanula et al. (2011:41–49), Lwoga (2009), Deng et al. (2009:231–235) and Agea et al. (2008:419–420) have alluded to similar activities of products from these plants on a variety of crops by small-scale farmers in KwaZulu-Natal, Zambia and Malawi, Tanzania, Kenya and Uganda, respectively.
| TABLE 3: Preparation methods, plant parts, formulations and combinations used and their corresponding target pest. |
The 27 pest control preparation methods, identified by famers, were categorised using four extraction techniques, namely boiling, mixing, soaking and a combination of boiling and soaking. Mixing and soaking techniques were the most prevalent (44.4%). The prevalent use of these two extraction techniques could be associated with the fact they are inexpensive compared to boiling, and perhaps do not take as much time as when a combination of mixing and boiling is employed.
Farmers in this study worked with a variety of plant parts in the preparation of insecticides. Similar to a number of studies conducted on indigenous insect pest method, including that of Mugisha-Kamatenisi et al. (2008:342–348) in Kenya, they used leaves alone, leaves and bark, leaves and bulb, whole plants, leaves and stalks, cloves and pods. Leaves were the most used plant parts. Seemingly, leaves are easier to pick and to work with compared to other plant parts, and possibly were a convenient choice for older farmers who were the majority users of botanical insecticides in this study. Leaves also contain more secondary plant metabolites, thereby observed to be most active.
Formulations and their combinations were applied either on the whole cabbage plant, leaves including the head or avoiding the head, the whole plant and around it or just around the plant. This seemed to vary per insect pest.
Regarding quantities of ingredients or plant parts, farmers were unable to provide quantities of each ingredient used in formulations or combinations because they depended on plant availability, as the majority were not cultivated. As a result, preparation methods were not standardised. Farmers, however, did indicate intervals of insecticide application.
Arthropod pests of cabbage in the cultivation areas
Farmers identified six insect pests and one arachnid (spider) as pests of cabbage (Table 4). Of the six insects, only a cricket (Orthoptera: Stenopelmatidae) was not controlled by using plant insecticides. The most cited arthropod pests were aphids (Hemiptera: Aphididae), cutworms (Lepidoptera: Noctuidae) and the diamondback moth (DBM) (Lepidoptera: Plutellidae) with a citation frequency of 53.4%, 51.2% and 29% respectively. Aphids, the DBM and cutworms are confirmed as the most prevalent pests of cabbage in South Africa (DAFF 2010; Mkize 2003; Weeks 2007). The prevalence of each pest differed per district. Only 40% of formulations or combinations were prepared against cutworms, whereas 89% were for the control of aphids. This could mean that aphids were viewed as the most problematic pests in the study areas. Although spiders were perceived as pests, they are generally predators of insect pests and their presence in gardens is regarded rather as that of a friend than a foe (Sunderland 1999: 308–316).
| TABLE 4: Arthropod pests of cabbage in the study areas. |
Conclusion
These findings, based on farmers’ observations and practices, will need to be tested under greenhouse and field conditions. A continuous documentation, assessment and validation of indigenous pest control methods is needed so that the information does not get eroded or lost. Furthermore, research on these methods may lead to the development and deployment of local technologies for pest management.
Acknowledgements
The authors would like to acknowledge the farmers who willingly participated in this study and the Eastern Cape Department of Rural Development and Agrarian Reform for funding this project.
Competing interests
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
Authors’ contributions
N.L.S. was the project leader and was responsible for all conceptual contributions and the writing of the manuscript. M.A.P. provided consistent comments during the analysis and write-up of the manuscript, and thoroughly reviewed it. All authors read and approved the final version of the article.
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