摘要:

SUMMARYSurveys in 1974–75 in which 20 plants were examined in each of 105 fields showed that cabbage stem weevil was widespread on spring oilseed rape in the south of England, the larvae sometimes infesting a large percentage of plants and reducing vigour and yield. In replicated field trials during 1974–77, infestations were reduced by seed treatments of gamma‐HCH or sprays of gamma‐HCH, azinphos‐methyl, azinphos‐methyl + demeton‐S‐methyl sulphone, chlorpyrifos or triazophos. In some experiments treatments significantly improved plant growth or yield, or both. Granules of carbofuran or phorate also reduced larval infestations and damage, but both thiofanox granules and dimethoate sprays were ineffective. Sprays of gamma‐HCH or azinphos‐methyl + demeton‐S‐methyl sulphone which were effective against stem weevil could also in some years give improved control of blossom

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03964.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYInfection of carrot roots byMycocenlrospora acerinain chill storage (3.5 °C) following inoculation with chlamydospores was studied in 1973–74 and 1974–75.AREAS of intact periderm were only rarely infected, and the high level of periderm resistance predominated over other variables. However, wound infection tended to increase with depth of wound and with increasing age of the plants at harvest. Irrespective of age of root or depth of wound, roots were comparatively resistant to infection at harvest and early in storage, resistance being expressed as a restriction of mycelial growth on the wound surface or localisation of the lesion. Increasing susceptibility with time in storage, depth of wounds, or age at harvest, resulted in larger numbers of inoculated sites becoming infected and a more rapid development from localised to progressive les

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03965.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe period of infection byPseudocercosporella herpotrichoideswas investigated by transplanting winter wheat from uninfested to infested sites at Cambridge. Maximum infection was found on plants moved between November and March; most conidia were trapped during winter but infection was not closely related to the numbers of conidia. Plants exposed at intervals on infested land and incubated in a standard environment became infected throughout the period from October to July; infection was not closely related to the numbers of conidia trapped or plant age, but was positively correlated with the number of wet days/wk. Thus, while enoughP. herpotrichoidesconidia were dispersed throughout the life of winter wheat crops to cause substantial infection, environmental factors limited the development of new infections from April onwards. Practical implications of these results for the choice of sowing date, the development of resistant varieties, and fungicide use, are discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03966.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe susceptibility to gangrene infection of wounds of various shapes and depths on potato tubers was studied by inflicting wounds using differently‐shaped brass teeth and rods of different diameters. Inoculating wounds with spore suspensions or damaging tubers which had been previously contaminated withPhoma exiguavar.foveataor which had been recently lifted from plots of field experiments showed that wounds in which tissue was crushed were most susceptible to infection. Over a wide range of inoculum concentrations and in experiments using several different cultivars the incidence of infection of any wound type was compared to that of the standard severe cut and crush wound. Using a probit transformation a linear relationship was established, the slope of the line indicating the relative susceptibility of the wound.In 1977 and 1978, crops of cv. Pentland Dell were surveyed for damage incidence, inoculum and inoculum potential on arrival at a commercial bulk store. Nets of tubers buried among the tuber bulk were recovered after storage and gangrene incidence compared with damage and inoculum assessments. Inoculum potential and incidence of severe damage both influenced disease development but damage incidence was of greater importance, showing that priority should be given to decreasing damage and to curing to promote rapid wound healing in endeavours to control the diseas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03967.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYErgot (Claviceps purpurea) of grasses is prevalent throughout Britain. The disease also occurs regularly in most cereal varieties but generally is of low incidence. Incidence is much greater in open‐flowering and male‐sterile cereals, with the infection seeming to come, initially, from the large reservoir of inoculum amongst grasses. The production of F1‐hybrid cereal seed, which necessitates the use of male‐sterile lines, could therefore be jeop

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03968.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYIn a series of experiments excised leaves from take‐all infected wheat plants and from control plants were inoculated withSeptoria nodorum. Larger lesions, more lesions/leaf and more pycnidia/unit area of lesion were produced from take‐all plants. Significant effects of predisposition were demonstrated when only 3% of the area of the total root system was infected by take‐all.Microscopical investigations revealed that germ‐tubes ofS. nodorumgrew more rapidly on leaves from take‐all plants, but the time of penetration was not affected. It is proposed that the observed effects of predisposition arose because more germ‐tubes produced successful infections and host tissue was more rapidly colonised.The importance of these results for the epidemiology of glume blotch i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03969.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYChocolate spot lesions increased in size only slowly when the relative humidity of the air was below 66%. Following a lag phase immediately after infection the rate of increase was linear and proportional to humidity betweenc. 70% and 100% r.h. Lesions on leaflets kept at 70% r.h. for 8 h and at 100% r.h. for 16 h/day increased in size at only 27% of the rate of those at continuous 100% r.h. The optimum temperature for lesion growth was between 15 and 22 °C, the minimum<4 °C and the maximumc. 30 °C. Humidity did not interact with temperature between 10 and 20 °C. Neither light intensity nor a film of water over the leaves affected lesion growth. These findings are discussed in relation to meteorological data and field observations.The possible mechanisms whereby humidity affects lesion growth did not appear to be related to CO2and O2concentrations nor to the overall water potential of the leaf.Preliminary evidence is presented for the production of phytotoxins within lesi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03970.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYFiltrate extracts from liquid cultures ofB. fabaeand extracts from spreading chocolate spot lesions contained at least two heat‐stable, light‐labile phytotoxic compounds. Lesions similar in appearance to those of chocolate spot developed after injection of fractions containing these compounds into healthy bean leaves. Of 15 plant species injected with an extract from lesions,Vicia fabaappeared to be the most susceptible to damage.Evidence is presented to support the hypothesis that under conditions of low humidity the concentrations of toxic compounds in an infected leaf become high enough to kill healthy cells surrounding infected tissue. The dead tissue then dries out preventing further fungal growth and lesion spread. In saturated air, however, the toxic compounds diffuse throughout the lamina and become too dilute to kill uninfected tissue. Tissue does not become desiccated and the fungus continues to spr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03971.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe failure of Benlate (50% benomyl) to controlMycogone perniciosaon mushroom farms where isolates of the organism were benomyl sensitive was investigated. A comparison was made of carbendazim levels, the major fungitoxic breakdown product of benomyl, in unsterilised casing, autoclaved casing and autoclaved casing mixed with a small proportion (1.7%) of casing previously treated with benomyl but from which all detectable levels of carbendazim had disappeared. Added benomyl was effective in controllingM. perniciosain autoclaved casing, less effective in unamended casing and ineffective in the amended casing mixture. The recovery of carbendazim from these treatments was directly related to disease occurrence.Studies on farms where benomyl or other carbendazim generating fungicides had been used indicated that a lack of control ofM. perniciosawas associated with the disappearance of fungicide from the casing before cropping began. This was not so on a farm where carbendazim generating fungicides had not been used before these investigations. Thiabendazole, a fungicide closely related to the carbendazim generators showed only a slight decline in concentration in casing capable of degrading benomyl.Bacteria isolated from the casing were examinedin vitrofor their ability to degrade benomyl. Five groups of bacteria were compared and three bacteria,Pseudomonas putida, Pseudomonas aeruginosaand an unidentified member of the Entero‐bacteriaceae were most able to degrade benomy

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03972.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

SUMMARYBarley yellow striate mosaic virus (BYSMV) was inoculated by its planthopper vectorLaodelphax striatellus(Homoptera, Delphacidae) to 44 species of Gramineae, 26 of which in eight tribes were infected. The virus was not transmitted through wheat seed nor did it infect five dicotyledonous hosts of other rhabdoviruses. The most susceptible species were in the tribes Festuceae and Hordeae. Barley,Bromusspp., oats,Phalaris canariensis, Setaria italica, Sorghumspp., and sweet corn cv. Golden were diagnostic hosts. Electron microscopy of crude sap was also a sensitive diagnostic method. Properties of BYSMV were determined by injectingL. striatelluswith crude sap from infected barley. Sap was infectious after 10 min at 50–55 °C but not after 10 min at 60 °C, when diluted with buffer to 10‐‐2but not to 10‐‐3, when stored for 2 but not 4 days at 5 °C or when kept for 1 but not 2 days at 22 °C.The planthopperJavesella pellucidawas an experimental vector of BYSMV but the virus was not transmitted by the leafhoppersMacrosteles sexnotatusorPsammotettix striatus(Homoptera, Cicadellidae). The latent period of BYSMV inL. striatelluswas most commonly 15 or 16 days (minimum, 9 days; maximum, 29 days). The minimum acquisition access period for transmission was between 1 h and 5 h, and the minimum inoculation feeding time was 15 min. After 24 h and 8 day acquisition feeds, 30.4% and 42.8% respectively ofL. striatellustransmitted BYSMV. When transferred daily, infective hoppers transmitted virus intermittently. The maximum retention of infectivity byL. striatelluswas 36 days.Two of five infective females transmitted BYSMV transovarially. Larvae became infective in the second wk after hatching and transmitted f

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1980.tb03973.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY