Albert Minks and Simon Voerman
Research Institute for Plant Protection (IPO-DLO), 6700 GW Wageningen, The Netherlands
Introduction
[top]
Pheromone research at Wageningen started at the then called Laboratory for Research on Insecticides (LIO) in 1967. Leafroller moths were chosen as subject for our studies, because they formed at that time a major problem in pome fruit orchards in the Netherlands. After we had shown that live female traps worked effectively, we set our first goal, namely the chemical identification of the sex pheromone of the summerfruit tortrix moth, Adoxophyes orana. The publication of the pheromone identification of the closely related red-banded leafroller, Argyrotaenia velutinana, by Roelofs & Arn in 1968 came right on time and helped us in convincing our research leaders to give green light to go ahead with our research. A fruitful collaboration between LIO and TNO at Delft (F.J. Ritter & C.J. Persoons) was initiated and continued until 1980. Pheromone identifications of several leafrollers and other moth species followed, starting with that of A. orana in 1971 (see further Table 1A).
In addition to the identification studies, we developed our own lines of research: a chemical (S. Voerman) and an entomological research line (A.K. Minks). Our major objective was to make pheromones usable in agricultural practice, according to the institutional policy, which we could endorse fully. We both preferred a "no-nonsense" approach in our research, probably due to our Friesian origin, and we have tried to keep things straightforward e.g. by taking our chemicals directly into the field for activity testing. During all these years we kept our believe in the great practical potential of pheromones. These substances are unique in their species specificity and extremely low toxicity, which are very favourable characteristics for pest control agents in integrated control systems. The great potential has been illustrated by the large number of pheromone traps used nowadays for monitoring. During more than 25 years tens of thousands of traps per season have been used worldwide in many different cultures and this number is still growing.
Pheromone research at Wageningen has made a significant contribution to that development in chemical respect (through the systematic production of potential pheromone compounds of high quality), as well as in entomological respect (through making methods of indirect and direct control with pheromones applicable to agricultural practice). We are glad that we can add that a consistent research policy could be maintained, despite budget cuts and changes in the organisational framework: LIO was renamed IOB (Institute for Pesticide Research) in 1979. On its turn the activities of IOB were terminated in 1990 and the pheromone research group became part of IPO-DLO.
Chemical research and the IPO pheromone bank
[top]
Chemical research eventually resulted in the development of the so-called pheromone bank, which became one of the best known and most valuable assets of our present institute IPO-DLO.
Soon after the first successful identifications of lepidopterous sex pheromones in the early 70's had been completed, it became apparent that only a rather limited number of compounds was involved. These pheromones comprised almost exclusively unsaturated alcohols, esters and aldehydes with 10 to 18 carbon atoms in the aliphatic chain. Mono-unsaturated acetates and alcohols played an important role. It became also clear that there were certain relationships between chemical structure of the pheromone and the taxonomic position of groups of moths.
This triggered the idea to make a collection of these compounds by synthesizing the complete series of mono-unsaturated acetates and alcolhols, later followed by a selected group of poly-unsaturated compounds. It became known as the pheromone bank and was originally meant as a service to colleagues. Compounds were delivered to be used as reference compounds for identification problems in gaschromatography and electroantennography. A special argentation chromatography set-up was developed to obtain substantial quantities of end products with a high isomeric purity: an essential requirement in pheromone chemistry. The pheromone bank made it also possible to quickly find effective attractants via EAG- and field screening (see Table 1B).
In more recent years, when the financing of our institute became more and more problematic, the pheromone bank developed gradually into a commercial enterprise. We found ourselves back selling pheromone dispensers in increasing numbers, for an increasing number of moth species and for increasing prices. It was a niche in the market and we could serve a large group of clients in many countries. We still synthesize most of the compounds by ourselves, but, when it is cheaper, we also buy pheromones from the industry. Yet, this is not as simple as it looks at first sight, as there are only few reliable addresses available. A fortunate example concerns the pheromone of the codling moth, Cydia pomonella, which is available for an acceptable price and at a good quality. Pheromone components that are not for sale must be synthesized by ourselves in our own laboratory, such as those of the potato moths, Phthorimaea operculella (E4,Z7-13Ac and E4,Z7.Z10-13Ac; identified 20 years ago) and the recently discovered mixtures (E3-14Ac and E3,Z7-14Ac) for Symmetrischema tangolias and (E3,Z8-14Ac and E3,Z8,Z11-14Ac) for Scrobipalpuloides absoluta (Table 1A). And there are more simple looking compounds for which only tedious and time consuming methods exist. They form a real challenge for the pheromone chemist and keep him alive.
Table 1 List of Dutch identifications of sex pheromones and sex attractants of Lepidoptera
| A. Identifications of sex pheromones by means of chemo-analytical research, confirmed by field screening | |
| Adoxophyes orana | Meijer et al. 1972 |
| Clepsis spectrana | Minks et al. 1973 |
| Archips podana | Persoons et al. 1974 |
| Phthorimaea operculella | Persoons et al. 1976 |
| Cryptophlebia leucotreta | Persoons et al. 1977 |
| Spodoptera exigua | Persoons et al. 1981 |
| Syndemis musculana | Persoons et al. 1984 |
| Symmetrischema tangolias | Griepink et al. 1995 |
| Scrobipalpuloides absoluta | Griepink et al. 1996 |
| B. Number of sex attractants, found via field screening of compounds from the IPO pheromone bank, arranged per lepidopteran family (until 1995) | |
| Acrolepiidae (1) | Noctuidae (10) |
| Argyresthiidae (6) | Pyralidae (8) |
| Drepanidae (1) | Sesiidae (4) |
| Gelechiidae (2) | Tineidae (3) |
| Glyphipterigidae (1) | Tortricidae (49) |
| Gracillariidae (8) | Yponomeutidae (3) |
The IPO pheromone bank has great significance for our clients, both the dispenser users for practical purposes and for the chemists, the reference compound users. We firmly believe that our institute should maintain and even extend the pherobank, since it certainly has a much higher potential to serve clients than is being used now. Collaboration with pheromone sellers in other markets should be sought and further developed.
Entomological research first concentrated on the estimation of the efficiency of sex pheromone traps and on the development of quantitative monitoring with sex pheromone traps through studies of the relationship between trap catches and moth numbers actually present in the field. In the 80's our attention shifted to mating disruption and we were mainly occupied in efficacy testing of various commercially available pheromone dispensers, first of all orchard pests. Recently, after excellent greenhouse facilities became available to our institute, we spent most of our time on pheromone control of noctuid pests in greenhouse cultures. The renewed collaboration with TNO, this time the TNO Plastics and Rubber Research Institute (J.J. de Vlieger & J. Klijnstra), should be mentioned here, since TNO polymer dispensers are being used in all our greenhouse tests. Highly fruitful and very exciting is also our cooperation with Syntech (J.v.d. Pers), where portable EAG and SSR equipment is being developed that enables direct measurement of pheromones in ambient air.
The IOBC/WPRS Working Group on Semiochemicals
[top]
We always have felt a close relationship with this working group. We were both present at the meeting of the IOBC/WPRS Working Group "Integrated Pest Management in Fruit Orchards", held at Wädenswil in November 1973, where at least 30% of the programme was devoted to pheromones. From the pheromone colleagues assembled at the meeting the idea arose to start "their own" working group. The proposals were readily accepted by the IOBC/WPRS Council and in October 1975 the first meeting of the Working Group "The Use of Insect Pheromones in Integrated Control" took place at Wageningen. There were 32 participants from 8 countries. The major goal of this first meeting was to get an idea of what was done in Europe in the rapidly expanding field of pheromone research. The participants found the meeting very rewarding, as most of them realized that they were badly informed about each others work.
Table 2 shows that since then the Working Group has met at 12 other occasions, including the recent meeting at Montpellier. Its meetings developed into an important forum for pheromone workers in Europe in the first place, but we are happy to state that they were often attended by colleagues from countries outside the WPRS region, such as the USA, Australia, Canada and Japan. It looks a bit contradictory, but a major problem of the Working Group has always been the overwhelming interest. Most meetings were attended by more than one hundred participants and showed rather the character of a conference, which was not really in line with the meetings of most other IOBC/WPRS Working Groups, where joint projects were planned, executed and the results discussed at the next meeting. However, there is no doubt that the significance of the Semiochemical Working Group has been great and that numerous informal collaborative projects have been initiated and carried out in the past 20 years as a result of its activities.
Table 2 Meetings of the IOBC/WPRS Working Group on Semiochemicals since 1975
| Convenor: Albert K. Minks (1975-1985) | ||||
| Wageningen | NL | 1975 | Introductory meeting, various topics | |
| Harpenden | UK | 1977 | Chemistry and biological activity | |
| Wädenswil | CH | 1979 | Fundamental and applied aspects | |
| Nyon | CH | 1982 | Mating disruption in fruit and grapes | |
| Hamburg | D | 1984 | Pheromone and attractant chemistry | |
| Balatonalmádi | H | 1984 | Joint meeting with EPRS Working Group | |
| Convenor: Heinrich Arn (1985-1995) | ||||
| Neustadt/Weinstrasse * | D | 1986 | "Behavior of Moths and Molecules" | |
| Avignon * | F | 1988 | "Current Status of Insect Monitoring with Attractants | |
| Granada | E | 1990 | "Pheromones in Mediterranean Pest Management" | |
| San Michele all'Adige * | I | 1992 | "Mating Disruption in Orchards and Vineyards" | |
| Chatham * | UK | 1993 | Basic and applied aspects | |
| St. Peters Insel | CH | 1994 | "The Wormy Apple Brainshop" | |
| Convenor: Peter Witzgall (since 1995) | ||||
| Montpellier * | F | 1996 | "Technology Transfer in Mating Disruption" | |
* The proceedings of these meetings have been published as IOBC/WPRS Bulletins.
When glancing through the reports of the early meetings, it is striking to see that some of the items are still present on the programme of today, which does not mean that no progress has been made in this field. On the contrary! It is also interesting to note that already in the meetings in 1977 and 1979 proposals for a pherobank and a pheromone list came forward. We described above that the pherobank idea became reality and developed to a highly successful operation. The same can be said about the pheromone list. After a rather amateurish attempt by the first author of this contribution, which appeared in 1984 as IOBC/WPRS Bulletin VII/1, Heinrich Arn published, together with Miklós Toth and the late Ernst Priesner, the "List of Sex Pheromones of Lepidoptera and Related Attractants", as an IOBC/WPRS Brochure in 1986. The book became a great success and serves now as the vademecum of every pheromone researcher. A 2nd edition appeared in 1992, which can still be obtained from the Federal Research Station at Wädenswil in Switzerland. Nowadays the regularly updated list can also be consulted on the Internet.
These examples show that the Working Group has played an important role in the coordination and stimulation of pheromone research in Europe. It is still much alive. We sincerely hope that it will continue its activities for many more years to come.
After almost 30 years in pheromone research it is time to say goodbye. We have really enjoyed working together with you in this exciting area of research. Many highlights have passed along in all those years and we consider ourselves as very lucky that we could play our part. One important recommendation emerges from our experience: close collaboration between chemists and entomologists, preferably in the same institute is essential for success in this research area!
So it is time to stop now: Simon will do this completely and Albert will hang around for another year or so by participating in some small projects. And he certainly will continue with his editorial work.
Finally, we are happy to announce that the management of our institute has recently decided to continue with pheromone research. Some months ago a successor for Simon Voerman has been appointed: Dr. Frans Griepink, a young and bright chemist, who has to meet great expectations. Although his position is secure for one year only, we are optimistic about further developments. It is further agreed that in the coming autumn Albert will be replaced by one of the IPO entomologists via an internal reshuffle.
Cardé RT, Minks AK (1995) Control of moth pests by mating disruption: successes and constraints. Annu Rev Entomol 40, 559-585
Griepink FC, van Beek TA, Visser JH, Voerman S, de Groot Æ (1995) Isolation and identification of sex pheromone of Symmetrischema tangolias (Gyen) (Lepidoptera: Gelechiidae). J chem Ecol 21, 2003-2013
Griepink FC, van Beek TA, Posthumus MA, de Groot Æ, Visser JH, Voerman S (1996) Identification of the sex pheromone of Scrobipalpula absoluta: determination of double bond positions in triple unsaturated straight chain molecules by means of dimethyl disulphide derivatization. Tetrahedron Letters 37, 411-141
Houx NWH, Voerman S, Jongen WMF (1974) Purification and analysis of synthetic insect attractants by liquid chromatography on a silver-loaded resin. J Chromatogr 96, 25-32
Meijer GM, Ritter FJ, Persoons CJ, Minks AK, Voerman S (1972) Sex pheromones of summer fruit tortrix moth Adoxophyes orana: two synergistic isomers. Science 175, 1469-1470
Minks AK, de Jong DJ (1975) Determination of spraying dates for Adoxophyes orana by sex pheromone traps and temperature recordings. J econ Entomol 68, 729-732
Minks AK, Cardé RT (1988) Disruption of pheromone communication in moths: is the natural blend really most efficacious? Entomol exp appl 49, 25-36
Minks AK, Roelofs WL, Ritter FJ, Persoons CJ (1973) Reproductive isolation of two tortricid moth species by different ratios of a two-component sex attractant. Science 180, 1073-1074
Minks AK, Voerman S, Klun JA (1976) Disruption of pheromone communication with micro-encapsulated antipheromones against Adoxophyes orana. Entomol exp appl 20, 163-169
Persoons CJ, Voerman S, Verwiel PEJ, Ritter FJ, Nooyen WJ, Minks AK (1976) Sex pheromone of the potato tuberworm moth, Phthorimaea operculella: isolation, identification and field evaluation. Entomol exp appl 20, 289-300
van Deventer P, Minks AK, Blommers LHM, Neumann U, Jilderda K (1992) Mating disruption utilizing lepidopterous sex pheromones: three years of testing in apple orchards in the Netherlands. Proc. Brighton Crop Prot. Conf. - Pests and Diseases, 1992 (3), 1193-1198
van der Pers JNC, Minks AK (1993) Pheromone monitoring in the field using single sensillum recording. Entomol exp appl 68, 237-245
Voerman S (1979) Chemical conversion of 9-tetradecen-1-ol acetates to 3,13-octadecadien-1-ol acetates, sex attractants for male clearwing moths (Lepidoptera: Sesiidae). J chem Ecol 5, 759-766
Voerman S (1988) The pheromone bank: a collection of unsaturated compounds indispensible for discovery of sex attractants for Lepidoptera. Agric Ecosyst Environm 21, 31-41
Voerman S, Rothschild GHL (1978) Synthesis of the two components of the sex pheromone system of the potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) and field experience with them. J chem Ecol 4, 531-542
Voerman S, Persoons CJ, Priesner E (1984) Sex attractant for currant clearwing moth Synanthedon tipuliformis (Clerck) (Lepidoptera: Sesiidae). J chem Ecol 9, 1371-1376
Weatherston I, Minks AK (1995) Regulation of semiochemicals - global aspects. Integr Pest Management Rev 1, 1-13
[top]