**3.4 Plants phytopathology and water monitoring**

28 Pesticides in the Modern World - Risks and Benefits

Overall the application of Agrochemicals significantly reduced the number and the species of pests on the treated plots. The Coleoptera and the Hymenoptera contain the main species of the predatory and natural enemies thus auxiliary (no target insect) of plants protection, having a significant impact on the dynamics of the populations of pests. The preservation of these different auxiliaries is necessary for a sustainable management of natural resources. Deltamethrin has a good level of selectivity with a superior advantage for the management of pests and the environment over the Acephate which, has a low selectivity but a wide range of effectiveness against insect pest and good residual activity. The preservation of the auxiliaries of culture in spite of the chemical treatment is essential considering the important

The Lepidoptera (larva), Orthoptera and Hemiptera represent the most important group of insect pests, which attack and cause the highest damage in vegetable gardening of lettuce, spinach and turnip. However, the considerable differences in number of captured insects and pests found between the treated and untreated field plots show that a targeted

The majority of the groups of pests which attach and cause important damage on turnip, spinach and lettuce can be controlled by the application of agrochemical products applying good agricultural practices (GAP) compatible with the protection of the environment and

However, one of the biggest problems encountered by vegetable producers is their lack of sufficient knowledge about how to use safely the agrochemicals. Very large numbers of empty pesticide containers are left lying in the fields because of the lack of collection and disposal facilities and constitute acute potential hazards for the environment and the fauna

The producers are not sufficiently aware of the risks of pesticides accumulation in vegetables, and the possible health problems for consumers being exposed to these risks. They are also often confronted with the problems of accessibility to agricultural credits.

role that they play in the maintenance of agro-ecological balances.

application of agrochemicals against these groups of pests is efficient.

the preservation of non-target organisms.

Photo 6. Pesticides Plastic container on the plot (Maneb)

due to the left-over of toxic pesticides in the containers (Photo6).

We identified only one pathogenic fungus on the lettuce (9 % of production). It is Cladosporium *sp of The* Amastigomycota *Divion*; *Group of Deuteromycete;* Hyphomycetes' Class and *Gender of Cladosporium.* This fungus is the agent responsible of Cladosporium gray mold, but the preventive spraying of Maneb (photo 6) gives efficient protection on the lettuce.

The irrigation water is characterized by the presence of micro-organisms such as Thermotolerant Coliform and the fecal Streptococci. Their numbers areas respectively one hundred fifty (150) times and one thousand (1000) times higher than the criteria for international standard allowed for irrigation water quality in agricultural fields (Table 9 and Photo 7).


Table 9. Microbiology Monitoring of Irrigated Water

Photo 7. Irrigated water quality is doubtful

The microbiological analysis of the irrigation water highlighted an overload of thermotolerant Coliforms and fecal Streptococci. These bacteria which are not normally pathogenic are usually used to indicate the possible presence of pathogenic microfauna organisms. Thus their very high number compared to the threshold recommended shows a low water quality (Photo 7).

 The strong presence of these indicator bacteria suggests a probable presence in the irrigation water of very dangerous pathogenic parasites that could develop and cause very important damages to the plants, farmers and the consumers.

The contaminated vegetables can cause a certain number of diseases. Particularly, the contaminated salads are sources of bacterial diseases such as the typhoid and paratyphoid

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fevers (Salmonella typhi/paratyphi) whose origin comes from the excrements of the patients or healthy carriers (MESSIAEN C.M, 1989). Other bacteria of the Salmonella species can also cause collective intoxications. The periodically endemic Cholera in the tropical countries, maybe transmitted by soiled salads. Also the bacterial dysenteria (Shigella dysenteriae) can be transmitted by soiled vegetables believed contaminated by the excrements. The preventive protection against these diseases is often done by vaccination. But the use of hygienic measures like disinfections with chloramphenicol, bleach into the water or the potassium permanganate (KMnO4) is of primary importance.
