Welcome in Aix enProvence Scientific Committee

From nicotine to -T: biopesticides, not a simple question of easily marketable molecules.

Bernard J.R. Philogène
Department of Biology, Faculty of Science, University of Ottawa, Ottawa, Canada K1N 6N5
Molecules of plant origin have had an important role in the control of organisms regarded as pests in agriculture and health, early in the game. They have been particularly in evidence at the end of the 19^th and the beginning of the 20^th century. Following the introduction of synthetic pesticides, biopesticides of plant origin (nicotine, rotenone, pyrethrum, etc.) faded into the background, pyrethrum and its derivatives excepted.
Within half a century synthetic pesticides went from spectacular results to serious problems for both target pests and non-target organisms, and the environment (resistance, chronic toxicity, various accidents).
While we are currently witnessing the resurgence of certain arthropod-borne diseases, the emergence of new infestationsd such as West Nile virus in North America, more severe restrictions placed on the use of synthetic pesticides by government agencies, and more vocal an global protests by environmentalists, scientists are actively looking for acceptable methods of control.
Biopesticides are again in the limelight because they are seen as “natural products” not capable of environmental contamination, There in fact hundreds of molecules of plant origin capable of modifying insect behaviour (e.g. azadirachtin) or which are simply toxic (e.e. alpha-terthienyl). An examination of several of these molecules extracted from both cultivated plants, and less known tropical species will demonsrtrate that there is a long way to go from chemical characterization to marketability. We will discuss current research on potential biopesticides with a new mode of action, capable of delaying if not preventing the onset of resistance in pests. Biopesticides will have to be subjected to the same scrutiny for registration as the synthetic pesticides they seek to replace.

Com. 6
Phthorimaea operculella granulosis virus: a biopesticide to control potato tuber moth in Tunisia
Laarif A a., Fattouch S b., Essid W b., Marzouki N b., Ben Salah H a. & Ben Hammouda M.H. c
a Laboratoire d"Entomologie, INRAT, Ariana 2049 Tunisie ; e-mail: [e-mail]

b Laboratoire de Génie Biologique, INSAT, Tunisie. c Laboratoire de Physiologie et Physiopathologie des Insectes, INAT,Tunisie.

Recent advances in the development of biopesticides offer opportunities for the worldwide exploitation of biological agents as replacements for more hazardous and environmentally unacceptable chemical pesticides and for inclusion in Integrated Pest Management programmes. The production and use of biopesticides in a developing country as in Tunisia, can provide local employment opportunities, reduce health risks and costs due to chemical poisoning and environmental damage. In addition to this, there are the benefits obtained through the control achieved by preserving natural enemies and indigenous biodiversity.
A number of qualities make baculoviruses attractive biological alternatives to chemicals for pest control, including the ability to produce and apply them using methods similar to those employed for chemical pesticides.
One of the main pest of potatoes in Tunisia, responsible of very large losses in potato production and storage, is the potato tuber moth Phthorimaea operculella (Zeller) (PTM). An alternative to chemicals in PTM control is a granulosis virus (Baculoviridae, Eubaculovirinae) isolated from this specie (see Raman & Alcazar, 1988) and already used against this pest (Ben Salah & Aalbu, 1992).
The objective of this study was to carry out a screening and an evaluation of local granuloviruses naturally present in Tunisia pest populations and to isolate local strains of this virus allowing the selection of a virus better adapted to the local host or ecosystems. On the basis of symptomatology, P. operculella larvae have been collected from different locations (the North, the Cap Bon and the Sahel of Tunisia). Indirect Enzyme-linked immunosorbent assay (ELISA) using a serum raised against the purified Tunisian isolate virus (Ben Salah & Aalbu, 1992) and applied for these samples had lead us to establish the geographical virus distribution. Comparative study of symptomatological and immunological approaches demonstrates that the serological technique complements the symptomatology for a better detection of the virus.
BIBLIOGRAPHY
Ben Salah H. and Aalbu R. (1992). Field use of granulosis virus to reduce initial storage infestation of the potato tuber moth, Phthorimaea operculella (Zeller), in North Africa. Agriculture, Ecosystems and Environment, 38, 119-126.
Raman K. V. & Alcazar, J. (1988): Biological control of potato tuber moth, Phthorimaea operculella (Zeller), using a granulosis virus in Peru. In Astun Potato association (APA), Proc., June 12-16, 1988, Kumming, China, 173-174.


com. 7
Plant Biopesticides : a future for IPM ?
Catherine Regnault-Roger
Laboratoire d’Ecologie Moléculaire

Université de Pau et des Pays de l’Adour-France

BP 11 55 – F-64013 PAU Cedex

[e-mail]

The intensive use of organic synthetised pesticides after the Second World War pointed the occurrence of sever ecological disorders. Nowadays, the urgency to develop alternative or complementary approaches for friendly environmental agriculture and development is demonstrated. Among these alternative approaches, one of the ways being explorated now is the plants biopesticides.

This strategy is not really recent. Secondary plant compounds were already used to control phytophagous insects since the end of the XIX° century. But it made great strides during the thirty last years because of the technological and scientific progress in the area of analytical chemistry and molecular biology. Consequently, the identification of semiochemical compounds improved the comprehension of species relationships and the interest of some for plant protection . It is pointed however that these kinds of compounds have difficulty to become a market success.

This communication intends to bring some arguments to the following questions:

• 
  Which answer can bring the allelochemical molecules to the IPM current concerns ?
  

• 
  Which interest do they represent for a durable development?
  
• 
  Which are the obstacles with their marketing?
  
• 
  Does this alternative approach have a future for plant protection?
  

The answers to these questions participate in the clarification of this significant debate for our future.
Com. 8
The control of the bio-attacks against dates in Tunisian palm groves – Present situation and perspective
KHOUALDIA Othman
INRAT/ CRPh 2260 Degache Tunisia

Although Date palm sector is in full expansion in Tunisia, the commercial quality of the date didn't record a substantial improvement, by reason of damages caused by the pestes, notably Ectomyelois ceratoniae Zeller (Lep. Pyralidae) or pyrale of caroubes, that is a bug polyphage. Besides pods of caroube, his larva feeds itself of very varied fruits as quinces, pomegranates, oranges, figs and notably dates on which it causes some considerable damages, can reach 20% of the national production.

Oligonychus afrasiaticus (MCGREGOR) became a major problem for the Date palm production, because of the considerable damages that it causes on dates
The present situation and the perspective of date palm pests control are presented.


Com. 9
Effects of sorption and biodegradation on toxicity of parathion and paraoxon to Nematodes: experiments and modeling.
K. Hdadi-Saffih*, M. Amichot** L. Bruckler*
* Unité “Climat, Sol et Environnement” (Avignon, UR 403 INRA)

** Unité “Réactions des Organismes aux Stress Environnementaux (Antibes, UMR INRA-UNSA,)
The parathion is an Organophosphaorus insecticide extensively used as agricultural and domestic pesticide. The toxicity of parathion for non-target organisms has been the subject of extensive research. Under aerobic conditions parathion is activated by oxidative desulfuration to the oxygen analogue paraoxon, that has a potent anticholinesterase effect and is more toxic than the parent chemical. Tests using pure cultures are the most widely used test methods for the toxicity assessment of chemical compounds and effluents, however great differences can occur between effects in pure culture and in soil. Testing toxicological effects in soil conditions is necessary because taking into account chemical and biological transformations of pesticides in soils makes it possible that competitive sorption may display reduced or increased toxicity as compared to the parent compounds in solution. For these reasons, it has been suited in this work to test the effect of sorption and biodegradation of parathion and paraoxon in soil on their toxicity to nematodes. This was made by testing the toxicity of organic chemicals freely dissolved in the pore water of soil on nematodes and comparing it to the toxicity of pure parathion and paraoxon applied directly to nematodes. The capacity of prediction of the toxicity of parathion and its metabolite paraoxon in soil was performed by developping a kinetic model for describing rates of sorption and biodegradation of parathion, and modeling the concentration in liquid phase of parathion and the main metabolite paraoxon. The results indicated a good agreement between the prediction of toxicity and direct effects of chemicals dissolved in the pore water of soil on nematodes.


Com. 10
Effect of pesticide exposure on Pacific oyster, Crassostrea gigas, haemocytes
B. Gagnaire¹, F. Géret², J. Haure³, J-L. Martin³, T. Burgeot² and T. Renault^1
1 Ifremer, Laboratoire de Génétique, Aquaculture et Pathologie, 17390 LA TREMBLADE, France

² DEL-PC, Ifremer, Rue de l’île d’Yeu, B.P. 21105, 44311 NANTES Cedex 3, France

³ Ifremer, Polder des champs, 85230 BOUIN, France
Shellfish industry has developed in an important way in France and particularly in estuarine areas. But these areas are subjected to pollutions due to anthropic activities. Particularly, agriculture is source of important quantities of several pesticides rejected in the rivers ; these pollutants may then be conducted in the estuarine areas. The harmful effects of pesticides on animals inhabiting these estuarine zones are poorly known. Among these animals, bivalve molluscs represent an interesting model because they are sedentary, so they cannot escape in the case of a chronic or sudden pollution. Moreover, they filter water intensively, which favour bioaccumulation of pollutants in their tissues.

In this context, effects of pesticides on haemocytes functions were tested in Pacific oyster, Crassostrea gigas. A pesticide combination (alachlor, metolachlor, atrazine, therbutylazine, glyphosate, fosetyl aluminium, carbaryl, diuron) in environmentals concentrations was tested in vivo on Pacific oysters. Animals used corresponded to two genetically selected populations produced in hatchery.

Other experiments involved in vitro contact between pesticides and cells of the defence system, haemocytes. Concentrations used were higher in order to approach concentrations that may exist within the animal tissues.

For all experiments, effects of pollutants on haemocyte activities have been analysed. Haemocytes were analysed by flow cytometry ; this technique allows to monitor different immune functions in a short period. Viability and cellular activities have been analysed.

Results indicate modifications of activities with the different treatments.
Key words: Crassostrea gigas, flow cytometry, haemocytes, pesticides, immunotoxicity.

Com. 11