摘要:

Summary:The metabolism of the herbicide napropamide has been studied in the field in the soil of replacement crops (cereals, corn, sugar beet, potato and several vegetables). Napropamide was soil applied in the autumn and the soil left fallow during the winter. Crops were sown in April of the following year and simulated the replacement crops that are grown in the event of failure of the first autumn‐sown crop. Trials were made twice, i.e. during the 1987‐1988 and 1988‐1989 crop seasons. The soil metabolism of napropamide was also studied in a rose nursery. Napropamide was transformed by microbiological processes in the soil into the corresponding monoethylamide and acid. These compounds did not generally accumulate in the soil, and their individual concentrations did not exceed that of residual napropamide during the observed growing seasons. The kinetics, metabolic pathways and agricultural implications of the herbicide are briefly disc

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01755.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The aim of this paper is to show the need for developing plant population biology studies in order to improve weed management when traditional approaches in weed science have failed, as shown by recent reviews on herbicide resistance. It is also suggested that the usual weed definitions do not reflect the new aims of weed ecology. The results of studies on the genetic, demographic and spatial variability of weed populations and their regulation by pests and pathogens are reported, and are discussed in the specific case of clonal perennial species.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01756.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The distribution of 37 common weed species in eight common Danish crops in response to seven edaphic factors was evaluated using linear logistic regression with adjustment for over‐dispersion. The main effects of soil properties on weed distribution were adjusted for crop type and sample year by the regression. Crop type and soil clay content were generally those explanatory variables that had the greatest influence on occurrence of the weed species, but all other factors examined (sample year, loss on ignition, pH, P, K, Mg and Mn) also had an effect on the occurrence of some weed specie

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01757.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Studies on the ecology and control of thistles in Australia, particularly those related to pasture improvement, are reviewed, and the results used to interpret increases and changes in thistle dominance. Several hypotheses, based on ecological differences in the thistles, their life cycles and changes in the soil/seed environment may explain the changing species incidence in the field, and it is postulated that, within a restricted group of competing thistle species, it may be more meaningful to interpret these ecological differences in terms of ‘tolerance of unfavourable conditions’ than in terms of ‘optimal requirements’.Alternative strategies for the control of thistles, including pasture competition, grazing management, the utilization of high soil fertility, and chemicals, are also assessed. It is re‐emphasized that the aim of any long‐term programme to control thistles, with or without the release of biological agents, should be the establishment and/or maintenance of a vigorous perennial pasture. The relative importance of different thistle species in Australian pastures and the ecology and dynamics of soil seed banks are identified as important areas for future thist

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01758.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:This study examined the effects of competition on the growth ofAvena fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A.fatuawas much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A.fatuato reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change‐over from cereal dominance in mixtures to A.fatuatiominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the art of canopy height extension. At one site the rder of competitiveness at anthesis was A.fatua= barley>wheat, and at the other site the order was A.fatua>wheat>barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variable

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01759.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:An in‐vitro growth system for investigating the behaviour ofS. gesnerioideson cowpea has been developed. The roots of young cowpea plants were spread over glass fibre filter paper in a shallow plastic tray, and a known number of germinatedStrigaseeds were placed on the cowpea root surface. This allowed the infection process of the parasite to be quantified. Good access to the host‐parasite association enabled the entire infection process to be easily monitored and tissue removed for cytological studies. Observations revealed for the first time that contact ofS. gesnerioidesradicles with host roots stimulated the development of radicular hairs and swelling of the tip of these radicles. Furthermore, penetration of cowpea roots byStrigawas shown to be localized and to cause very little damage to the host roots. Swollen parasite tubercles developed on the surface of the roots only after the host stele had been penetrated by invadingStrigacells. This growth system is suitable for in‐vestigating the mechanisms of host resistance. and also for rapidly screening cowpea germplasm for new sources of resistance to the Parasite. Resistant cowpea cultivars offer the best potential solution for control of this Par

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01760.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Pot and field experiments were performed in Burkina Faso in 1987 and 1988 to evaluate the resistance of selected ‘low‐stimulant’ sorghum (Sorghum bicolor(L.) Moench) varieties to the parasitic weed (Striga hermonthica(Del.) Benth. In a pot experiment, the variety IS‐7777 supported the lowest number and had the latest emergence ofStriga, compared with the other varieties tested. The varieties IS‐14825, IS‐6961, IS‐7739, IS‐14928 and IS‐14975 also had signifi cantly lower numbers of emergedStrigaper pot than the resistant control Framida. The resist ance of IS‐7777 was confirmed in field experi ments, as was that of IS‐7739, IS‐6961 and IS‐14928. However, the yield potential of these poorly adapted varieties was low inStriga‐infested fields. The varieties IS‐14975, IS–14825 and Seguetana Niarabougou exhibited a low susceptibility associated with a grain yield equivalent to that of the other varieties in farm fields infested byStriga. As Seguetana is already grown by Sahelian farmers, its use could be recommended in the absence of resistant varieties adapted to Sahelian agroclimatic conditions. The exceptionally high level of restance exhibited by IS‐7777 could be exploited in studies on the genetics and mechanisms of resistance of the host plant to the parasite, as well as

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01761.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01762.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Résumé:MALHERB est un logiciel de reconnaissance des mauvaises herbes des cultures. Ce logiciel permet la détermination, au stade adulte, de 490 espèces dont 82 graminées. Il utilise différentes descriptions d'une même espèce tenant compte de la variabilité intra‐spécifique et des difficultés de reconnaissance de certains organes. Les notions botaniques ne sont pas indispensables pour l'utilisation du logiciel. MALHERB gère une base de connaissances constituée essentiellement de 2 fichiers distincts contenant des ‘Plantes feuillées à port de graminées’ et des ‘Plantes feuillées à port different’. Les fichiers comportent, d'une part la description d'espèces à partir de caractères morphologiques et, d'autre part, des données ecologiques concernant leur répartition géographique, les cultures, le pH, la texture du sol auxquels elles sont associées. Le logiciel détermine d'abord des groupes d'espèces ayant en commun certains caractères, puis propose a l'utilisateur une clé spécifique à chaque groupe. Dans le cas où l'échantillon ne comporte pas certains organes necessaires à la détermination, MALHERB propose alors une reconnaissance fondée sur la comparaison de profils de caractères écologiques stationnels conduisant à un classement de vraisemb

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01763.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY