摘要:

SummaryWeeds were collected from carrot fields and some other sites at 27 localities in seven counties in Norway during August and September of 1986 and 1987. Leaf and petiole lesions were microscopically examined forMycocentrospora acerina. Viola arvensisandViola tricolorwere commonly observed with the pathogen. The fungus was also registered onFumaria officinalis, Galium aparine, Matricaria inodora, Matricaria matricarioides, Ranunculus repens, Senecio vulgarisandStachys palustris.In inoculation experiments in the greenhouse,M. acerinainfected carrot leaves and 13 of 16 species of weeds. The symptoms on the various susceptible plants showed some variation, but were essentially of the same pattern. The investigation indicates that weeds are common hosts of M.acerina.A list of 23 host weed species is given.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03476.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryPatterns of floral development, dry matter distribution and seed yield were examined in winter oilseed rape plants subjected to different pre‐floral growth environments. The duration of pre‐floral growth and plant size at flower initiation, measured in terms of total mainstem leaf number, were manipulated by varying the temperature between seedling emergence and flower initiation.Exposure of seedlings to low temperatures from cotyledon expansion onwards markedly reduced the duration of pre‐floral growth and the number of leaves on the mainstem. The subsequent development pattern of plants was largely dependent on the date of flower initiation and therefore vernalisation requirement. Indeed, the period of growth from flower initiation to maturity, considered on the basis of thermal time, was directly related to the duration of pre‐floral growth and mainstem leaf number. The thermal durations of the bud development phase and flowering period in plants exposed to different pre‐floral cold treatments but with a common date of flower initiation were similarly linked to these two parameters.Plants exposed to prolonged periods of low temperature treatment from cotyledon expansion onwards initiated fewer mainstem leaves during a relatively short pre‐floral growth phase and their yield potential was limited by a reduction in branch and flower numbers. Plants maintained at higher temperatures produced more mainstem leaves during an extended period of pre‐floral growth and supported a greater number of branches and flowers. However, this additional yield potential was not realised due to a reduction in seed numbers and mean seed weight. It appeared that seed yield of these plants was limited by increased competition between an excessive number of lower branches and flowers, a problem apparently created by excessive pre‐floral growth. Minimal competition for available assimilates between the limited number of branches of plants with a shorter pre‐floral growth phase and fewer mainstem leaves, resulted in lower levels of pod abortion, greater seed production and ultimately incr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03477.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryCommon heliotrope,Heliotropium europaeum(Boraginaceae), a summer annual, is a serious weed of pastures in Australia causing poisoning in sheep and other grazing animals. The weed is native to Mediterranean and Middle Eastern regions of Eurasia where it is attacked by several arthropods and pathogens including the rust fungusUromyces heliotropii.The host‐specificity of a virulent and effective strain of the rust from Turkey has been tested by inoculating 96 plants of importance to the Australasian region using both microscopic and macroscopic observations of the reaction of host and non‐host plants. The test plants included several members of the Boraginaceae and related families as well as species ofHeliotropiumnative to Australia. The infection was mostly limited to European species ofHeliotropium. U. heliotropiiwas thus found to represent a safe introduction and has recently been introduced to Australia for the biological control of common heliotr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03478.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryA large rotary trap designed to measure aerial spider density is described. A comparison of the rotary trap catch and a suction trap catch of spiders and other invertebrate groups showed that the rotary trap was operating at a greater efficiency for most groups. For spiders and non‐staphylinid beetles the two traps caught equal numbers. There were no differences in the species composition of spiders between the rotary and suction trap catc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03479.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryA nutrient, slant‐board technique was developed in order to estimate the losses to roots of white clover (Trifolium repensL.), caused by the feeding of the larvae ofSitonaweevils. In this preliminary experiment losses of up to 50% of root length were found. This simple technique was straightforward to use and has the potential for applications in a large range of root‐pest/feeding stud

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03480.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY