ALBERT

Notes: Mountain domes rising to ≈ 6600 m along Tibet’s Tanggula range herald the Eocene intrusion of calcalkaline granites into terranes accreted much earlier. Together with coeval, cogenetic volcanics, such intrusives, which have similar crystallization and cooling ages, may be part of an ESE-trending belt cutting central Tibet in half. This magmatic belt may have marked a former northern boundary of the plateau, testifying to S-directed subduction of the Asian mantle. Such subduction would have developed soon after India’s collision but long before the rise of the plateau’s present rims, along one of central Tibet’s Mesozoic sutures.

Notes: Approaches to the biological control of weeds in arable crops and integration of biological weed control with other methods of weed management are broadly discussed. Various types of integrative approaches to biological control of weeds in crops have been studied within the framework of a concerted European Research Programme (COST-816). During the period 1994–99, some 25 institutions from 16 countries have concentrated on five target weed complexes. Some major scientific achievements of COST-816 are: (i) combination of the pathogen Ascochyta caulina with an isolated phytotoxin produced by this fungus to control Chenopodium album in maize and sugar beet; (ii) the elaboration and preliminary field application of a system management approach using the weed:pathogen system Senecio vulgaris:Puccinia lagenophorae to reduce the competitiveness of the weed by inducing and stimulating a disease epidemic; (iii) combination of underseeded green cover with the application of spores of Stagonospora convolvuli to control Convolvulus species in maize; (iv) assessment of the response of different provenances of Amaranthus spp. to infection by Alternaria alternata and Trematophoma lignicola, the development of formulation and delivery techniques and a field survey of native insect species to control Amaranthus spp. in sugar beet and maize; (v) isolation of strains of different Fusarium spp. that infect all the economically important Orobanche spp. and development of novel, storable formulations using mycelia from liquid culture. Although no practical control has yet been reached for any of the five target weeds, potential solutions have been clearly identified. Two major routes may be followed in future work. The first is a technological approach focusing on a single, highly destructive disease cycle of the control agent and optimizing the efficacy and specificity of the agent. The second is an ecological approach based on a better understanding of the interactions among the crop, the weed, the natural antagonist and the environment, which must be managed in order to maximize the spread and impact of an indigenous antagonist on the weed.

Notes: In 1986, the Working Group on Biological Control within the European Weed Research Society planned a weed survey in 10 major crop systems throughout Europe. They were: (1) winter and (2) spring cereals, (3) maize and sorghum, (4) potatoes, (5) sunflower and soya, (6) colza (winter rapeseed), (9) sugar beet and (10) temperate orchards and irrigated Mediterranean orchards.Questionnaires were sent out to prominent weed scientists in all 26 European countries to rate the abundance and frequency of important weeds according to three classes for all crop systems in their respective countries. The results of the survey are presented.Based on the per cent of maximum score attained by individual weed species the 15 most important weeds were determined for each crop, and the 20 top scoring weeds for all crop systems combined. The prospects for biological control of weeds in Europe are discussed. Etude européenne des mauvaises herbes de dix cultures majeure.s en vue d'identifier les possi-bilités de lutte biologique En 1986, le Groupe de travail sur la lutte biologique au sein de la Société Europeenne de Mal-herbologie (European Weed Research Society) a organisé une enquete sur les mauvaises herbes présentes dans dix cultures majeures d'Europe: (1) céréales d'hiver et (2) d'été, (3) maïs et sorgho, (4) pomme de terre, (5) tournesol et soja, (6) colza, (7) cultures légumières, (8) vignes et verges méditerranéens non irrigués, (9) bet-terave à sucre et (10) vergers de la zone tem-pérées et méditerranéens irrigués.Des questionnaires ont été envoyés à des mal-herbologues reconnus des 26 pays européens pour, au moyen d'une classification à trois niveaux, évaluer dans leur pays 1'abondance et la fréquence des mauvaises herbes importantes dans ces systèmes de culture. Les résultats de 1'enquête sont présentés.Les 15 mauvaises herbes les plus importantes ont été déterminées pourchaque culture en fonc-tion du pourcentage du score maximum atteint par les différentes espèces, ainsi que les 20 mauvaises herbes obtenant les plus haul scores pour toutes les cultures combinées. Les possibilités de lutte biologique centre les mauvaises herbes en Europe sont discutees. Erhebung über die Verbreitung europäischer Unkrautarten als mögliche Zielefiir eine biologis-che Bekämpfung in zehn Hattptkultiiren Die Arbeitsgruppe ‘Biologische Bekämpfung’ der Europäischen Gesellschaft für Herbologie plante 1986 eine Unkrautaufnahme in 10 großen Kulturen in ganz Europa: (1) Wintergetreide. (2) Sommergetreide, (3) Mais und Sorghum, (4) Kartoffel, (5) Sonnenblume und Soja, (6) Winterraps, (7) Gemüse, (8) Wein und nichtbewässerte mediterrane Obstkulturen, (9) Zuckerrübe und (10) mitteleuropäische und bewässerte mediterrane Obstkulturen. Das Ergebnis einer Umfrage in allen 26 europäischen Ländern über die Abundanz und Frequenz wichtiger Unkräuter wird dargestellt. Die 15 für jede Kultur wichtigsten Arten und die 20 allgemein häufigsten Arten wurden bestimmt. Die Möglichkeiten der biologischen Unkrautbekämpfung in Europa werden diskutiert.

Notes: A ‘system management’ approach of biological weed control in crops is proposed and compared with other method's of biological weed control. It is based on the management of a weed pathosystem in order to maximize the natural spread and disease severity of a native or naturalized pathogen. This approach may be well-suited to situations where it is necessary to control single weed species in crops, and where no immediate and complete control is required, the production of large amounts of the agent is rather limiting (e.g. when using biotrophic fungi), and/or the importation of an exotic agent is not possible. This strategy provides fundamental knowledge of underlying mechanisms of crop production systems and is aligned with the view of modern agro-ecology, in which complete eradication of weeds is not desirable. The fundamental research required for a successful application of the ‘system management’ approach will be illustrated with the biological control project of Senecio vulgaris L. using the naturalized rust fungus Puccinia lagenophorae Cooke. A five-step procedure, together with selected results, will be presented. Main emphasis is given to the infection window, the study of the genetic structure of the plant and pathogen population, and the management of the infection conditions (a) to maximize the spread of the disease and the impact on the plants, and (b) to minimize the development of resistant plant populations. Joint application of herbicides at low doses, additional necrotrophic pathogens, and of biochemicals interfering with the weed's defence also will be envisaged, as well as their integration into general pest control practices. In this regard, biological weed control agents have to be seen as stress factors, not as weedkillers, and biological weed control as an integral part of a well-designed pest management strategy, not as a sole cure.

Notes: Experiments with potted plants of the weed Li naria vulgaris Mill. (Scrophulariaceae) were carried out to evaluate the effects of root mining by Eteobalea (syn. Stagmatophora) spp. (Lep. Cos-mopterigidae). Attacked plants had a shorter flowering season and produced seeds of lower weight. Continuous mining during winter resulted in a doubling of the number of stems in spring, but the total plant biomass remained un affected. This may have been caused by dis rupted apical dominance due to root-crown damage. The observed effects are expected to complement those of other agents used in the biological control of L. vulgaris in North America. L'incidence du minage des racines par Eteobalea spp. sur la croissance végétative et la reproduction sexuée de la linaire commune Linaria vulgaris Mill.Des expériences en pot sur Linaria vulgaris Mill. (Scrophulariacées) ont été conduites pour évaluer 1'effet du minage des racines par Eteobalea (syn Stagmatophora) spp. (Lep. Cosmo-pterigidae). La période florale des plantes attaquées était plus courte et les graines pro-duites avaient un plus faible poids. Un minage continu pendant 1'hiver se traduisait par un dou-blement du nombre de tiges au printemps mais la biomasse totale de la plante n'était pas affec-tée. Cela pourrait être dûà 1'arrêt de la dominance apicale par suite de dommages au collet. On attend des effets observés qu'il complètent ceux d'autres agents utilisés dans la lutte biolo-gique centre L. vulgaris en Amérique du Nord. Einfluß der Befalls der Wurzelbohrer Eteobalea spp. auf Wachstum und sexuelle Fortpflanzung des Gemeinen Leinkrauts (Linaria vulgaris Mill.) Bei Topfversuchen über die Wirkung des Fraßes von Eteobalea (= Stagmatophora) spp. in den Wurzeln von Linaria vulgaris Mill. hatten die be-fallenen Pflanzen eine kürzere Blühperiode, und die Samen waren leichter. über den Winter an-hallender Befall führte zur Verdopplung der Sproßdichte, doch die Gesamt-Biomasse blieb unverändert. Dies könnte auf die Unterbrechung der Apikaldominanz infolge der Schädigung der Wurzelkrone zurückzuführen sein. Die be-obachteten Wirkungen könnten die anderer biologischer Agentien zur biologischen Bekämpfung von Linaria vulgaris in Nord-amerika ergänzen.

Notes: Individual sperm cells produced by two male morphs of the bluehead wrasse Thalassoma bifasciatum did not differ in size (i.e. cell volume). Initial phase (IP) males (high sperm competition) had a 60% higher sperm concentration in their milt than did terminal phase (TP) males (low sperm competition), which may reflect differences in how accurately the two male morphs need to allocate sperm to their spawns. The energy density of milt was about 16% lower than that of eggs. Estimates of gametic energy investment based on (a) the difference in testis weights between the beginning and the end of the spawning period and (b) the number of sperm released in natural spawns (determined in other studies), suggested that, on a daily basis, IP males invest about 65% of that of females. Estimates based on stripping milt from IP males at the beginning and the end of the spawning period, however, indicated that their daily energy investment in gamete production is about 10% of that of females Gametic investment by TP males is lower than that by both IP males and females.