**3. Cases of pesticide mis-use**

314 Pesticides in the Modern World - Risks and Benefits

2008). The climatic conditions of West Africa especially rainfed lowland ecology is conducive for build up of pest populations. Pesticide use in Africa accounts for less than 5% of global pesticide use and per hectare averages are low, estimated at around 1 kg/ha active ingredient applied (compared with 3- 7kg/ha in Latin America and Asia (PAN, 2010). However, low use volumes do not necessarily equate to low risk, particularly as some of the most toxic pesticides continue to be applied in Africa especially in West Africa, often under extremely dangerous conditions (PAN, 2010). Though, there are differences in the rate of agrochemicals application across the agroecological zones, pesticide use was high in dry savannah of West Africa (Ephraim *et al.,* 2010). Pesticide use in Africa accounts for only 2– 4% of the global pesticide market of US\$31 billion (Williamson *et al.,* 2008). Although Africa is currently neither a major consumer nor producer of chemicals in global terms, pesticides use in the African agricultural sector is likely to increase as a result of the growing commercialization as well as the growing focus of development agencies on improving yields of small farmers (Nelson *et al.,* 2006). Most African countries were net importers of pesticides. In Ghana, the number of pesticides dumped by the chemical industries was between 163 to 180 units as at 2002 (Suglo, 2002). In Kabba area of Kogi State, Nigeria, the number of pesticide users increased dramatically from 42% in 1971 to 78% in 1998 (Youm *et al.,* 1990). Importation of agrochemicals into sub-Sahara Africa increased in monetary values from \$16.1 million in 1973 to \$30 million in 1977 (Youm *et al.,* 1990). Most of the pesticides brought into West African countries have been banned. Pesticide that is banned for agricultural purposes in 52 countries due to its hazardous nature is being used in Ghanaian agriculture (Glover *et al.,* 2008). Most farmers in Africa increasingly depend on pesticides alone to control insect pest, and without satisfactory understanding of the associated hazards. Nigeria ranked first among West African countries in terms of quantities of pesticides use (Abete *et al.,* 2000). Thus, Nigeria alone accounted for nearly 93% of UK pesticide exports to West African countries. Pesticides are the main sources of pollution in

Fig. 2. Pesticide application on rice field

Over the decades, chemical pesticide use has posed a threat to subsistence farming in West Africa because of the well known technical drawbacks such as high cost, lack of adequate protection for the user, absence of safety warnings, excessive and wasteful use leading to environmental pollution. A case in point is the Gezira irrigation scheme in Sudan, where continuous use of pesticides against the cotton jassid, *Empoaca lybica* has led to resistance in the whitefly (*Bemisia tabaci*), cotton bollworm (*Helicoverpa armigera*), and aphids (*Aphis gossypii*). This, in turn, has led to even higher rates of pesticide application and the consequent emergence of secondary pest outbreaks due to the selective removal of natural enemies from the crop system. For instance, citrus leafminer (*Liriomyza trifolii*) is native to Asia but has been a minor pest of citrus in Africa until recent years when it is now considered as the major threat to citrus (Abete *et al.,* 2000). The picture was not different in Madagascar where *Spodoptera littoralis* became a serious pest due to over-use of chlorinated hydrocarbons including monophos-DDT against cotton pests. Pesticide overuse to control pests in other crops such as cotton, coffee, cacao, groundnuts has resulted in the development of resistance to dieldrin and DDT by two mosquito species, *Anopheles gambiae*  Giles and *Anopheles rofipes* (Gough) in the West African countries of Ivory Coast, Nigeria, Ghana, Mali, Burkina Faso, Togo, and Senegal.

In South East Asia, Brown Planthopper (BPH), a secondary pest of rice, suddenly became a major pest due to insecticide misuse. Since 2005, outbreaks of rice BPH have occurred in East-Asian countries such as Vietnam, China and Japan.

#### **3.1 Destruction of non-target organisms and natural enemies**

Non-target organisms are organisms that the pesticides are not intended to kill. Natural enemies include insect predators, insect parasitoids, and insect pathogens. Over 98% of sprayed insecticides reach a destination other than their target species, including non- target species. Successful biological control using five exotic parasitoids against the potato tuber moth, *Phthorimaea operculella*, both native of South America was achieved in Zimbabwe and Zambia. Unfortunately, this system has broken down due to increase in pesticide use by farmers unaware of the value of biological control, and due to the need other pests. Overuse of pesticides in Ghana to control cocoa mirids resulted in the killing of numerous non-target beneficial organisms. As a consequence, the shield bug, *Batl1ycoelia thalassina*  (HerrichSchaeffer), a secondary pest resurged and caused a yield loss of 18% of the cocoa crop in Ghana's Eastern and Brong-Ahafo Regions (Owusu, 1971, Alfred *et al.,* 2001,).

#### **3.2 Human and animal health hazards**

Chemicals pollute the water body thus making it unsafe for human use e.g. drinking, washing of farm produce, etc. Many of the pesticides used are persistent soil contaminants,

Is Pesticide Use Sustainable in Lowland Rice Intensification in West Africa? 317

Biological control is a major component of sustainable agricultural systems that are designed and managed to reduce dependence on chemical and other energy-based inputs, minimize ecological risk resulting from farming practices, and enhance agricultural productivity in relation to resources available. To ensure that biological control will contribute to sustainable agriculture, AfricaRice identified the gregarious endoparasitoid *Platygaster diplosisae* (Hymenoptera: Platygastridae) and the solitary ectoparasitoid *Aprostocetus procerae* (Hymenoptera: Eulophidae) are the most important wasps attacking AfRGM. The *Paspalum* gall midge (PGM) *Orseolia bonzii* Harris (Diptera: Cecidomyiidae) which infests *Paspalum scrobiculatum* L. (Poaceae), a common weed in rice agroecosystems, is distinct from AfRGM, and is an alternative host for the two main parasitoids of AfRGM. The delay between the destruction of *Paspalum scrobiculatum* and the appearance of AfRGM populations on a rice crop means that the large majority of the parasitoids from *O. bonzii* die before AfRGM population is available – asynchrony between pest and associated natural enemies. AfricaRice has shown that habitat manipulation with *Paspalum scrobiculatum*  management at the edge of rice fields had significantly increased the carry-over of parasitoids from *Paspalum* gall midge (*Orseolia bonzii*) to AfRGM. The combination of beneficial organisms, tolerant varieties and habitat management suppressed AfRGM, restored nature's balance, and resulted in increased rice yields (Nwilene et al., 2008a).

Chemical free products for insect pest control include the use of botanicals and biological control using pathogens. AfricaRice has demonstrated that neem seed powder and neem oil can provide effective control against termites in West Africa (Nwilene et al., 2008b). Termites constitute a major biotic constraint to upland rice production in West Africa. The control of termites has largely relied on broad spectrum and persistent organochlorine insecticides. Land use practices can affect the flow of water and persistent pesticides along toposequences from the fragile upland to the lowlands thereby causing harmful effect to humans. To meet the needs of upland rice farmers in West Africa, AfricaRice has shown that the biological control pathogen – the entomopathogenic fungus *Metarhizium anisopliae* is effective against termites on rice fields and can also be used as alternative to persistent chemical pesticides because of the serious health and environmental risks in terms of pollution, destruction/death of non-target/useful insects, and the reduction of biodiversity.

The Food and Agriculture Organization of the United Nations in collaboration with technical assistance from AfricaRice introduced the concept of IPM training in farmer field school (FFS) to West Africa through a series of technical cooperation projects in irrigated rice schemes in Ghana, Cote d'Ivoire and Burkina Faso. Following the success of this programme, IPM farmer field school projects were extended to several other countries in West, Eastern and Southern Africa. The initial results obtained by farmers who applied IPM practices for irrigated rice production in Ghana showed that yields of rice were consistently higher in IPM fields than in fields where conventional farming practices were adopted. In the rice fields where farmers adopted IPM practices, pesticide use for pest control was reduced by over 90% and savings on pesticide use amounted to \$100 per ha. Net returns from such fields were 32% higher than in farmer practice fields. Data from Mali show

**4.2 Biological control** 

**4.3 Chemical-free products** 

**4.4 Adoption of IPM practices** 

whose impact may endure for decades and adversely affect soil conservation (USEPA, 2007). Pesticide related poisoning deaths are often caused by using pesticide packages or containers after they are emptied of toxicants. It was reported by Youm *et al.* (1990) that forty six residents in Ilorin area of Nigeria were hospitalized as a result of "mistakenly drinking or eating pesticides". Also, in a study conducted by Hotton *et al.* (2010) in the northeastern part of Nigeria on effect of pesticide use, he found out various ailments associated with pesticide use and the use of pesticide container. These include: bronchilis chest pain, asthma, cough, running nose, vomiting, nausea, excessive sweating, diarrhea, burning on urination, abdominal pain, irritation of eye, temporarily and permanent lost of vision, weakness of arms, hands and legs, stiffeners of the waist, fatigue, etc. Empty pesticide containers are used to store food because of a lack of understanding on dangers of pesticides, poor pesticide labeling, and a low literacy rate. Pesticides that are applied to crops can volatilize and may be blown by winds into nearby areas, potentially posing a threat to wildlife (Sequoia & Kings, 2007). More importantly, the remains of these pesticides flow back to the streams and river. Some people at the other end will fetch it for drinking and for other domestic activities thus resulting to one ailment or the other depending on the concentration. Fish and other aquatic biota may be harmed by pesticide-contaminated water (Collin *et al.,* 2008).
