**2.2 Experimental plots**

16 Pesticides in the Modern World - Risks and Benefits

The turnip, *Brassica rapa L. var. rapa*, **(Brassicaceae)** is produced in specialized market gardening. The plant is normally bi-annual (photo 4). In its vegetative stage it is constituted of a basal rosette made of about fifteen leaves with real green limb and bristling with rough

According to the varietal type, it has a tuberous root of flattened, conical or cylindrical form and of variable color (white (photo 4), yellow, black or two-tone) (LAURENCE S et al., 2009). One notes about thirty varieties but the range of the varieties currently cultivated is rather restricted (Tokyo hybridizes F1, Chinese turnip…). Turnips are primarily cultivated

The needs in mineral elements are important and sustained fertilization (NPK) is needed before planting and during the growth cycle. The application of manure must be done

The growth cycle is 40 - 70 days dependent on climatic conditions and varieties. Turnips are harvested as young roots by successive thinnings. The diseases control and protection of

Photo 3. Spinach: *Spinacia oleracea L* 

hairs (photo 4).

**2.1.3 The turnip,** *Brassica rapa L. var. rapa*

in full field by direct seeding on fertile well-prepared seedbeds.

before planting and preferably on the previous crop in a rotation.

turnips must be regular due to frequent pest attacks.

Photo 4. Turnip: Brassica rapa L. (White – Turnip)

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). Two types of traps were put in every plot of land:


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

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

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 two traps.
