**2.1 Plants**

Subsistence crops are defined as crops that may be rich in proteins or carbohydrates grown by a farmer principally to feed his or her family, with little or nothing left over to sell while urban farming crops are considered as crops supplying luxury items intended for privileged people (MESSIAEN C.M., 1989);. Our study concerned three urban farming vegetable crops namely: Lettuce, Spinach and Turnip.

#### **2.1.1 The Lettuce,** *Lactuca sativa L*

14 Pesticides in the Modern World - Risks and Benefits

The main objective of this study is to assess the impact of pest on urban farming Lettuce, Spinach, and Turnip production, the application of agrochemicals for plant protection, and the quality of irrigation water. The specific objectives are (1) to evaluate the impact of agrochemicals application on plants' pests, (2) to determine their economic incidence, (3) to monitor irrigation water quality, and (4) to control some essential production factors which

The study was conducted near the "M'POUTO village "located around the lagoon Ebrié next to the district of Riviera-Golf of the city of Abidjan, the economic capital of Côte

Photo 1. M' POUTO village; district of Riviera-Golf in Abidjan City. Côte d'Ivoire

climatic conditions of the study zone is characterized by four seasonal cycles:

composed of tall grasses and scattered bushes (Photo 1).

respectively 33°C and 21°C.

namely: Lettuce, Spinach and Turnip.

**2.1 Plants** 

The experimental zone is in full sub-equatorial climate with surrounding vegetation mostly

The area is characterized by hydromorphic and sandy soils (DUCHAUFOUR Ph, 1997). The

A big or long rainy season from May to July and a small shorter rainy season from October to November followed by a long dry season from December to April and a short dry season from August to September. The average annual rainfall is about 2500 millimeters with a relative humidity of 80 to 90 %. The maximum and minimum average air temperatures are

Subsistence crops are defined as crops that may be rich in proteins or carbohydrates grown by a farmer principally to feed his or her family, with little or nothing left over to sell while urban farming crops are considered as crops supplying luxury items intended for privileged people (MESSIAEN C.M., 1989);. Our study concerned three urban farming vegetable crops

are indicators of a good standard quality production.

**2. Materials and methods** 

d'Ivoire.

The Lettuce, *Lactuca sativa* **L. (Asteraceae or Compositaceae)** is the more consumed vegetable in the world. There are approximately 149 varieties worldwide (CHAUX C et al., 1994). There are two main classes of lettuce: non-head forming lettuces such as the " celtuce " or " lettuce - asparagus " and the head-forming lettuces such as the " Batavia " or " curly " cabbage lettuce (Photo 2).

Seeds germination is normal between 0°C and 25°C, and sunlight plays a major role in the growth and the development process. Lettuce has a high water demand (E.J. RYDER et al, 1976), and grows well in different types of soils presenting a steady structure with good water holding capacity. In general, lettuce is a moderately heavy consumer of nutrients. Seedlings of lettuce are planted at 2 to 4 leaf-stage in well-prepared seedbeds (trays of earth) ploughed at depth and mixed to manure. The application of fertilizer (NPKS) is often necessary and must be incorporated in the soil before planting. The growth cycle is very variable (45 to 100 days) depending on the variety. Agrochemicals applications (insecticides and fungicides) on the lettuce cultures against the pest attacks are often done in the middle and end of cultural cycle.

Photo 2. Lettuce salad: *Lactuca sativa (*Batavia)

## **2.1.2 The spinach,** *Spinacia oleracea L*

The spinach, *Spinacia oleracea L*. **( Chénopodiaceae)**, is named " the prince of vegetables " (VERGNIAUD P. 1976). It is an annual plant generally cultivated as biennial in vegetable gardens (Photo 3). The plant develops initially, on a very short axis, a rosette constituted of fifteen (15) to twenty (20) leaves. These leaves are lengthily petiolate with full limb more or less blighted. Mineral fertilization (NPK) is often necessary according to expected yields. But the poultry's liquid manures and dejections abundantly brought are very largely sufficient to face exports of mineral elements. Watering must be sufficiently abundant to satisfy the water needs of the plant. The diseases and pest management of the plants must be carefully and frequently controlled (LAUMONNIER R., 1978). Also, weeding is very important and a thinning can be practiced in case of a very dense germination and seedlings. Spinach usually matures in 35 to 45 days. The plant may be harvested from the time there are 5-6 leaves on the plant right before the seed stalk develops (Photo 3). The phytosanitary protection of the plants intervenes in middle and end of cycle (FABIEN SEIGNOBOS et al., 2000).

Quality of Vegetables and Pests Control in African Urban Cities 17

The used method is the visual trapping by colored traps to estimate the presence, the quantity and the quality of the individual species (RIBA et al., 1989; FISCHER et al., 1987).

All these traps contain some soapy water which captures insects. The harvest of the grips is made every two days with change of the trapping liquid. Insects are kept in glass jars

The ground is raised to form wide mounds or ground trays of 10 meters long by 1, 5 meters

Every Block is formed by two plots of land or beds of 5 meters by 1, 5 meters each (see Fig1,). One of the plots of land is treated and the other one is untreated and constitutes the Control plot (blank). All in all, four Blocks and eight plots of land were realized: two Blocks for Lettuce, one Block for Spinach and one Block for Turnips. Every plot of land contains

**(***S***)- α-cyano-3-phenoxybenzyl (1***R,***3***R***)-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylate (***IUPAC***)** 

containing some alcohol (70 degrees) before being sent to the laboratory.

**2.2 Experimental plots** 

wide Blocks.

two traps.

**2.3 Agrochemicals** 

**Structural formula:** 

Two types of traps were put in every plot of land: - An air trap at the level of the foliage (see Fig 1). - A ground trap on the surface of the ground**.** 

Fig. 1. Experimental Plots with air and ground traps

**2.3.1 Deltamethrin: trade name DECIS (K -OTHRINE) Molecular formula: C22H19Br2NO3** (WHO., 1990a, 1990b)

Photo 3. Spinach: *Spinacia oleracea L* 
