**1. Introduction**

310 Pesticides in the Modern World - Risks and Benefits

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polychlorinated biphenyls and mercury in osprey eggs—1970–79—and their relationships to shell thinning and productivity. Arch. Environ. Contam. Toxicol.

association of grouse moor in Scotland with the illegal use of poison to control

Rice is a major staple food for about 3 billion people (Nguyen and Ferrero 2006). In West Africa, it is indeed no longer a luxury food and has become a major source of calories for the urban poor. The poorest urban households obtain 33% of their cereal-based calories from rice (NISER, 2005). Urbanization, changes in employment patterns, income levels, and rapid population growth have contributed to widening the gap between supply and demand (Figure 1). The gap between production and consumption is made up by imports, which are estimated at 2 million metric tones per annum.

Fig. 1. World Population Growth 1950–2050 (Source: United Nations, 2009).

 \* A. Togola2, O. E. Oyetunji1, A. Onasanya2, G. Akinwale1, E. Ogah3, E. Abo4, M. Ukwungwu4, A. Youdeowei5 and N. Woin6

Is Pesticide Use Sustainable in Lowland Rice Intensification in West Africa? 313

The major insect pests of lowland rice in West Africa include: the African rice gall midge (AfRGM), *Orseolia oryzivora* Harris and Gagné (Diptera: Cecidomyiidae); the rice stem borer complex: the stalk-eyed flies – *Diopsis* spp. (Diptera: Diopsidae); the African white borer – *Maliarpha separatella* Ragonot (Lepidoptera: Pyralidae); the yellow stem borers – *Scirpophaga* spp. (Lepidoptera: Pyralidae). Other important pests of rice include: vectors of rice yellow mottle virus (*Trichispa sericea* Guérin, *Chaetocnema pulla* Chapius, *Chnootriba similis* Thunberg and *Oxya hyla* Serville, etc.). All these pests are indigenous to West Africa except *Maliarpha* 

Serious damage to the rice crop by the complex of insect pests result in significant yield losses which are typically in the range 10-30% yields and, in some regions or years, may exceed 90% (Nguu, 2008) (Table 2). Pests cause considerable and unacceptable crop losses in the field and in storage. The very high food losses in West Africa, attributable to pests,

Country Pests Estimated crop loss

African rice gall midge

African rice gall midge

Table 2. Examples of average losses attributable to pests of rice in selected West African

The yield potential of rice cultivated in the intensified systems is continually challenged by chronic pest infestations and by pest outbreaks. This challenge is seen by the chemical industries mostly based in Asia and developing countries as an avenue to aggressively market their products in West Africa. The products are sold without proper training of smallholder farmers on how to safely apply it and without warning of the harmful effect on the environment. The sad aspect of the race for pesticide sales is that many banned pesticides in Asia and other developed countries of the world are being dumped in West Africa. The indiscriminate use of the pesticides has posed a lot of danger to the environment and ecosystem making human life to be under threat. The current article, therefore, not only meets a demand expressed from the regional entomologists but also makes an important contribution to raise alarm of the danger of pesticides in lowland rice which is currently

As agricultural production system moves more and more from subsistence to market – oriented large scale farming, a concomitant increase in pesticide usage arise (Sosan *et al,*

25 – 30% 10 – 35%

10 – 40% 20 – 60%

**1.2 Insect pests of rice in West Africa** 

*separatella* that can also be found in Asia.

**1.3 Yield losses caused by insect pests** 

Nigeria Stem borers

Burkina Faso Stem borers

**1.4 The race for pesticide sales in West Africa** 

**2. Importation of pesticides into West Africa** 

Source: Youdeowei (1989, 2004)

being targeted for intensification.

countries

highlight their role in causing food shortages that lead to hunger.

Ghana Stem borers 30%

Mali African rice gall midge 20 – 35% Cameroon Stem borers 26 – 30%

Rice remains one major crop in which West Africa can easily become self-sufficient given the potentials that abound in the region. The potential land area for rice production in West Africa is between 4.6 million and 4.9 million ha. Out of this, only about 3.7 million ha—or 75 percent of the available land area—is presently cropped for rice. Cultivable land to rice is spread over five ecologies, namely: rainfed upland, rainfed lowland or shallow swamp, irrigated rice, deepwater or floating rice and tidal mangrove swamp. The commonly used ecosystems and share of rice area for the rice ecosystems are presented in Table 1.


**Upland:** area expansion and yield increase may be fulfilled **Rainfed lowland:** most promising **Irrigated lowland:** dam construction is too expensive at current rice price Source: Sakurai, 2006

Table 1. Rice production ecology in West Africa

Amongst these, lowland rice has the highest priority, being the ecology that represents the largest share of rice area and rice production. Smallholder farmers with farm holdings of less than 1 ha cultivate most of the rice produced in West Africa. However, rice productivity and production at the farm level are constrained by several factors. These constraints include insufficient appropriate technologies, poor supply of inputs, ineffective farmer organizations and groups, poor quality of rice, poor marketing arrangements, inconsistent agricultural input and rice trade policies, and environmental constraints. These environmental constraints include poor drainage and iron toxicity in undeveloped lowland swamps, poor maintenance of developed lowland swamps, drought, deficiencies of N and P, poor soil management practices, seasonal over-flooding of rice fields, pests and diseases.

#### **1.1 Hypothetical shift in production system**

With the increasing awareness of the limited potential for intensification of rice production in the uplands, farmers are gradually moving into the lowlands, which are less fragile (permits residual moisture use), more fertile and ecologically robust. The lowland areas are underutilized in West Africa. The lowland areas are expected to meet the growing demand for rice in West Africa because they provide potential for expansion, diversification and intensification of rice production in the region. This change in farming practice has been accompanied by an increase in the use of agrochemicals (pesticides and fertilisers), highyielding varieties and monoculture/continuous cropping, which further disrupt traditional farming and natural ecosystem functioning. Most West African countries are currently undergoing intensification in rice production to cope with the high population pressure. However, these may have adverse consequences on pest outbreaks, if it lacked the vision on the conservation of renewable inputs (biodiversity), and the whole issue of sustainability. This prediction is based on the hypothesis that with the improvement in the irrigation system, farmers will be able to grow high-yielding, photo-insensitive rice crops, and more crops per year on the same field. In such systems, the pest and beneficial cycles will be uninterrupted.
