ACKNOWLEDGEMENTS

Let me express my thanks in connection with the plan of organization of this Symposium.

As the "Strawberry Plant under Protection" symposium is placed under the auspices of the International Society for Horticultural Science, my first thanks go to this organization. In spite of the manifold occupations required of him, Dr. de BAKKER, General Manager at the Dutch Board of Agriculture, had accepted to be among us; but family reasons have obliged him to phone me this morning and to ask me to excuse his absence. He has asked to M. VAN KOOT, from Naaldwijk, to represent him at this session today.

We approached the Comité belge de Recherches du Fraisier and asked them to accept the responsability for the organization of the Symposium. M. HABRAN, the active president of this committee, will give us more details about this group of researchers and extension members, which - as it has already been said - has deeply influenced both the practical evolution and technical knowledge at hand to date. We thank M. HABRAN as well as M. LEMAITRE, Research Worker at this committee, for the help they gave to us. We thank too M. GILLES, BENOIT & AERTS, attached to the Research Station of Gorsem, to the Research Station of Sint Katelijne Waver and to the Experimental Garden of Meerle, respectively well known researchers entirely devoted to our problem, and authors of a great number of very interesting publications. We shall meet these four specialists when we shall visit their working-places.

The belgian Board of National Education and the Ministery of Agriculture have agreed to patronize our Symposium. Since some sittings will be held in Gembloux and since I myself depend on its services, let me first express my gratefulness to the Rector of the Faculté des Sciences agronomiques de l'Etat of Gembloux - presently abroad - and to the Protector - Professor HENNAUX - who has accepted with enthousiasm to welcome us and to stay today. To these acknowledgements I want to join those I address to Professor LECRENIER - holding the mastership of Horticulture Department to which I belong myself - who gave us intellectual and material help and advise.

The Symposium is also patronized by the Ministry of Agriculture. The General Director of the Agronomical Research Department - M. LIEVENS - has accepted to delegate the Director of the Agronomical Research Centre of Gembloux M. LECOMTE and his Public Relations M. CANTILLON and to be represented by M. DERMINE, Director of the Fruit and Vegetable Plant Station of Grand Manil who, furthermore, took an active part in the organization of the Symposium and accepted to welcome the Congress and to show them round his Station. We thank all these persons heartfully.

Let us revert once more to the International Society for Horticultural Science which patronizes our Symposium, the various Sections, Commissions and Working-groups of which have collaborated with us. Let us first mention the "Vegetable" Section. Much to their regret, its president, Professor FRITZ of Weihenstephan and its active secretary M. PECAUT of Montfavet cannot be with us. However, they have delegated specialists to represent them: M. WINTER and M. MOLOT whom we sincerely thank.

The Commission for "Protected Cultivation" has also taken an active part in the organization of the Colloquium; we have already named its president, Professor LECRENIER. His devoted secretary, M. VAN KOOT has accepted to come and replace his President. We sincerely thank him for his presence today. The Commission for "Horticultural Economics" apologizing for his president, Dr. FOLLEY's absence, has delegated a qualified researcher, M. ELEMA of Wilhelminadorp; we are most grateful.

Finally, the Commission for "Horticultural Engineering" has given us its help through its various Working-Groups: "Greenhouse Climate", "Greenhouse Structure", and "Plastics in Horticulture", We mention Professor RENARD, Prorector at the Technical University of Hannover, whose work have put a mark on the orientation of the research in horticultural technique for more than twenty-five years. We cannot overlook the Working-Group "Plastics in Horticulture" over which we preside. It is as responsible of this Working-Group and as a Rector at the Chaire d'Horticulture of our Faculty that we decided to organize this Symposium. Indeed, we feel that this Working-Group "Plastics in Horticulture" may play an important part practically and theoratically by organizing international meetings where general subjects (such as the Symposium of Turino in 1967) or particular ones (such as the present Symposium) are approached. This is also the reason why we want to take an active part in Congresses prepared by other international organizations such as the 5th International Congress on Plastics in Agriculture of Budapest, organized by the C.I.P.A. (International Committee for Plastics in Agriculture).

We associate to the previous organizations the so-called International Committee for Plastics in Agriculture which is responsible for the organization of the above Congress which will be held in Budapest next week and in which some of us will take an active part; it is with a view to coupling the two Manifestations as much as possible that we proposed our Symposium to be held from May 29th to June 2nd. The C.I.P.A. and the I.S.H.S. have agreed to exclude the problems of strawberry plants under shelter from the Colloquium of Budapest and to keep them for this present meeting. We sincerely thank M. BUCLON, General Secretary of the C.I.P.A. for his understanding, for his help and for this presence among us.

We should be angry with ourselves for not thanking sincerely all the persons who are here today, whatever their future participation to our Symposium. Among all the researchers coming from eighteen countries and who I cannot cite personally here, I should like to mention M. GONTSHAROUK, well known in the scientific world, actually Agricultural Counsellor of the U.S.S.R. Embassy for the Netherlands and Belgium, and who has wanted to attend all the sessions of our Symposium with his Assistant M. VOLOSSOV.


INTRODUCTORY LECTURE

As a conclusion to this introduction, let us try to place in their general context the various problems that will be considered: i.e. the problems of the strawberry plant culture under shelter by opposition to the culture in the open air.

On the hand, we have the plant - the Strawberry Plant - which, as already stated, has well-precised needs that are not always easy to be satisfied.

On the other hand, we find climate of the country or of the region where the culture is to be carried out: obvious reasons have led as to call it "natural climate". It has its own characteristics (insolation, temperature, water balance, winds…) which vary in the course of the year. This climate is not always favourable to the growth of the strawberry plant and it allows growing in the open air only at periods easily precised. But the general wish is to lengthen these periods, haastening or delaying the dates of natural production by growing these plants under shelter, i.e. by putting a cover of given properties between the natural climate and the plants. It goes without saying that the most important characteristics are photometric, since they are the greatest modifier that acts on the above mentioned natural climate and changes it into a climate that may be called "spontaneous" or "derived"; it comes spontaneously from the first as a result of the properties of the covering material. Obviously, other factors than the cover have quantitative influence upon the qualitive climate generated by the cover: dimensions, orientation and structure of the shelter…

Contrary to the common thought, the spontaneous climate does not necessarily meet the needs of the plants better than the one its comes from: an unfortunate choice of the cover may bring still poorer living-conditions to the plant. The shelter (and especially its cover) must be advisedly chosen if it as to provide the culture with a spontaneous climate more favourable than the climate it comes from. The agronomist is therefore to use his skill to predetermine advisedly the characteristics of that shelter, which, under specified conditions, would help to improve the natural climate for the plant. Thus, the spontaneous climate will often prove to be far from optimum; indeed, for instance, by raising the thermic minimums, a cover raises the maximums automatically and sometimes it even stresses them. The user of the shelter will thus have to bring about some changes in the derived climate: the extreme temperatures will be moderated by heating and ventilation, the balance of water improved by watering and ventilation,… but a sensible choice of the shelter must obviously reduce such "a posteriori" interventions and even suppress them.

These considerations explain why we have preferred to treat some subjects rather than others.

As you already know, 5 subject will be considered:

1. the building of shelters i.e. the properties and use of modern materials liable to be used as covering materials for strawberry plants;
2. the climate within the shelters i.e. the so-called "spontaneous" or "derived" climate coming from the natural climate of a region subsequently to the use of a well-determined cover;
3. the agronomical consequences of the characteristics of the spontaneous climate, i.e. the problems of the strawberry plant culture under the new conditions generated by the shelter;
4. to these subjects it has seemed logical to add a fourth ("Diseases") taken as a further consequence of the characteristics of the derived climate, as far as the plant is concerned;
5. finally, we deem it logical, since the agronomist is an engineer of production bound to financial imperatives and since the market gardening industry is no kind of charity organization, to study the economic aspect of the problem.

   Let us revert each of these subjects.

1. Building of shelters:

   While glass has long been the only material used in horticulture, about 1955 there appeared in Europe a new family of materials, commonly called "plastics", completely different from glass as far as the properties and the conditions of use are concerned. We will not present all these new materials; they are sufficiently known. The aim of the reports is to precise the present tendencies both regarding the creation of new synthetic materials and their use, i.e. the conception and building of shelters; indeed, some are completely different from the traditional glass-covered shelters. Fundamental and applied research go hand in hand with the users disederatums. Much is expected from the confrontation of the various standpoints that will be put forward, since the think that the industry, creators of new products, is to work ultimately according to the general directions of the users of their products and of the agronomists whose aim is to foresee the future problems and to determine the most efficient ways of use.

2. Climate within the shelter:

   The problem is to characterize the "spontaneous" climate derived from the "natural" climate subsequently to the use of the cover such as it is described in subject 1. General principles and practical examples will be given. We wish to make it clear that by the word "shelter" we mean classicalgreenhouses as well as plastic tunnels of any dimension and "plastic mulching", baffling expression for the non-initiated but which simply means "covering of the ground by means of very thin plastic layers of well-defined properties". As we could be helped by specialists in the research and use of covering materials (subj. 1), in a similar way, we have been helped by several specialists, researchers and extension members in "plastic mulching".

3. Culture

   During the reports, the general exigencies of the various varieties of strawberry plants and the characteristics of the spontaneous climate under some precised types of shelter relatively to the natural climate of the considered region will be compared. Furthermore, some speakers will describe their effort to adapt the strawberry plant to the new conditions; we think a.o. of the problem of the varieties for the culture under shelter, problem which remains for us one of the most important, above all for the strawberry plant whose assortment of varieties is rapidly renewed, which is favourable to a good evolution of the culture. Finally, the influence of various ways of culture on the final result of the culture will be treated: planting-time, use of "frigo", plants, etc.

4. Phytosanitary problems:

   A more or less perfect adaptation of the shelter to the exigencies of the plants and conversely a more or less sensible choice of the varieties relatively to the spontaneous climate has some consequential effects on the phytosanitary control: obviously, the more unfavourable the spontaneous climate is to the plants, the less these ones may cope with their natural enemies and the more important is man's action. Furthermore, some derived climates are liable to favour the development of some parasites or predators, though they prevent more or less efficiently the pullulation or even the mere survival of other enemies (or friends!) of the plants. Thus, new phytosanitary problems appear in culture under shelter. They should be solved without any delay. Finally, without being cryptogamic or zoologic, some diseases called "physiologic" because often scarcely known, add to the previous ones: it is therefore useless to explain the importance of such reports devoted to the research of the origins of malformation of fruit in sheltered cultured.

5. Economic problems:

   Economic problems are hard to be approached in international congresses, composed in their majority of researchers and extension members, specialized in technical matters: the conditions of production vary too widely from one country to the other. However, the confrontation of the ideas of four specialists from different countries (United Kingdom, France Netherlands and Belgium) is of major interest. Furthermore, during the previous days, on one hand, these economists will have had the opportunity of being confronted directly with technical problems that they seldom have to study thoroughly, and on the other hand, the researchers and the technicians will have been able to grasp the complexity of financial problems and feel better their incidence on the final results of the culture and hence on the very subject of their works.