摘要:

The present paper, the sixth of the series, gives the results of testing some 700 species of the larger Basidiomycetes for bacteriostatic properties. Initially, the ‘juice’ extracted from the sporophore was tested and this was followed in certain cases by a test of the metabolism solution produced by the fungus in culture. The results indicate that the larger Basidiomycetes are among the more promising fungus groups which produce antibiotics and that they compare favourably in this respect with the Aspergilli and the Penicillia. Of the 700 species tested approximately 70 are strongly and approximately 100 weakly positive againstStaphylococcusaureus and/or Bacterium c

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06737.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Results are presented to show that all the rules of proof for insect transmission ofNematosporabyDysdercusspp. have now been satisfied: viz. a close association of the insect with diseased plants in nature; visitation of healthy plants by the insect under conditions suitable for transmission of the disease; the presence of the pathogen in or on the insect in nature or following visitation to a diseased plant; and experimental production of the disease by insect visitation under controlled conditions. Hence it is claimed that Dysdercus spp. are proved vectors of internal boll disease of cotton.Fungal material as spores or mycelium is carried as an external contaminant on the mouth‐parts, although it is located in the deep stylet pouches, where protection is afforded and spore germination is possible.The fungus is cast off with the exuviae during moulting, but recontamination from exuviae or other sources in the environment occurs.The transmission is hence purely mechanical with the insect obligatory only in its function as a syringe to inject the fungus which is otherwise unable to reach its substrate. Insect and fungus can develop independently and the insect is apparently unharmed by the presence of the fungus.Nematospora spores also reach the intestine but do not appear to remain viable there and do not germinate.The fungus is believed to enter and leave the insect by the same route. The spores are well adapted in shape to reach the stylet pouches of the insect.No alternative morphological form of Nematospora gossypii within the insect has been found.The results do not lead to methods of control of the disease beyond those in practice‐trapping of insects, destruction of alternative host plants, and the alteration of time of planting to avoid insect att

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06738.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Inoculation with soil samples proved that the fungus causing dry rot is frequently present in field soils in Cheshire and in soil adhering to imported seed tubers. The fungus was viable in soils having a wide range ofpH values and in fields which had not grown potatoes for 5‐6 years. Other sources of infection include lofts, used sacks, seed boxes, diseased tubers, and knives used for cutting seed potatoes.Bruised tubers stored in heavily contaminated boxes developed much dry rot; far less disease occurred in unbruised tubers. In boxes containing own‐saved seed, healthy tubers in contact with diseased ones remained sound. Bruised tubers in contact with, or contaminated by, diseased tubers contracted dry rot. Cutting seed with a contaminated knife increased the disease seven‐fold.Inoculation of tubers attached to the parent plant showed that little or no infection occurred before lifting. In field trials severe dry rot developed in several varieties 6‐8 weeks after lifting.The results are discussed in relation to seed tr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06740.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Suitable organo‐mercury preparations applied by the short wet method of seed treatment and organo‐mercury powders, of the type used for treating cereal seeds, fixed to the seed with water by the fixation method of treatment, gave as satisfactory control of seedling blight and better control of stem break and browning than a proprietary dry fungicide containing tetra‐methyl thiuram disulphide (Nomersan) applied at the rate of 12 oz./cwt. of seed.Treatment of seed heavily infected withPolyspora Lintusing an efficient fungicide resulted in highly significant increases in crop and fibre yields, while in the case of seed heavily infected withColletotrichum Linisimilar treatments significantly increased the yield of fibre but not the crop yield. Some treatments significantly increased the crop and fibre yields even when the seed used was only slightly contaminated with P.Liniand C.Lini.The results presented support the suggestion that effective treatment of the seed may produce an increase of fibre not directly attributable to the prevention of seedling blight or stem break and browning but which may be explained by a general beneficial effect due to seed disinfection.The results obtained suggest that no treatment consistently affected crop establishment in the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06741.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

After a brief discussion of the methods and accuracy of diagnosis of the ‘phloem necrosis’ disease in the field, the results of plot records taken over a number of years are presented. These are compared with the figures supplied from estates for the removal of non‐productive diseased bushes, which is undertaken as a routine measure of control and regeneration of affected fields. Taking all the evidence together a frequency of at least 25% diseased bushes is suggested for the aggregate acreage of tea above 6000 ft. At lower elevations no reliable estimate is possible.Despite the pronounced effect on individual bushes there appears to be no general tendency for the yield of affected estates to decline. Two estates, believed to be representative, are dealt with in which a decline in yield occurred from 1929 to 1930, followed by a recovery some 4 or 5 years later. The fields judged to be most heavily affected in each of the two properties, respectively, show a decline in yield relative to the estate as a whole, not exceeding 19 1b. made tea per acre per annum, which is only 33% of the mean yield during the last 10 years. The great variability in individual bush yields is stressed, and the conclusion is drawn that the elimination of unproductive bushes and their replacement by supplies of a type which, so far, has remained unaffected (although possibly ‘carrying’ the virus) will more than counteract the effect of the continued and gradual deterioration of the necrotic bushes remaining.The distribution of diseased bushes in the field is irregular, and records from observation plots have mostly given positive results on examination by Cochran's geometric series ‘aggregation’ test and the X2test for ‘neighbour infection’. The rate of spread of the disease in the different areas is highly variable, and doubling of the incidence of infection may occur in periods ranging from 3 1/2 to less than 1 year. Two ‘rogueing’ experiments are described, the results of which lend further emphasis to the importance of bush‐to‐bush spread. The course of the disease in these experiments has been expressed by means of the Verhulst‐Pearl logistic curve, whence it appears that complete rogueing of all ‘necrotic’ and ‘suspected’ bushes at 6‐monthly intervals has reduced the rate of spread to about one‐th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06742.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

A method is described of transmitting the virus of the ‘woodiness’ disease of passion fruit by means of single leaf grafts. The grafts can be made from one species to another in the generaPassifloraandTacsoniaand from these genera to species ofAdeniaand vice ve

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06743.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

The role of aphis vectors in the deterioration of potato stocks is well known, and any effort to maintain healthy (virus‐free) stocks of potatoes depends on the degree of their isolation from these vectors. In practice this isolation depends on geographical, climatic, and biological factors; of these the biological factors are fundamental, as it is only from their study that the significant geographical and climatic factors can be determined.The present work consists of a survey made during 1942 and 1943, in the Northern Agricultural Advisory Province. Special attention is paid to overwintering, and the prevailing weather conditions at the time of the spring migratio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06744.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Observations made on the beet eelworm (Heterodera schachtiiSchm.) between 1934 and 1943 are described. This eelworm confines its attacks to crop plants of the families Chenopodiaceae and Cruciferae. Cysts similar to those of the beet eelworm have been recorded on many weeds. Records of beet eelworm on weeds of the above families are probably authentic, but those of other families require confirmation. In the field, the four so‐called strains ofHeterodera schachtii(viz. the beet, oat, pea and potato strains) behave as distinct species. Some evidence is given for the possible existence of a cruciferous strain.Attempts were made to ascertain the distribution of beet eelworm in East Anglia. A general search was conducted throughout the area and special attention paid to beet‐sugar factories, beet‐loading sites, sewage farms, and to certain important beet‐growing areas located in the Isle of Ely and neighbouring counties. Throughout the search, diagnosis was based on the finding of lemon‐shaped cysts on the roots of sugar beet, red beet or mangolds. Details of our present knowledge of the distribution of beet eelworm are given. It appears to have been present in Britain for a considerable time but is not yet widely disseminated.The spread of beet eelworm is considered in detail, and it is concluded that the establishment of the beet‐sugar industry has led to a considerable increase in the rate of spread.Measures for the control of beet eelworm are described. In the early days of the industry, beet was grown without regard to rotation, thus providing conditions similar to those existing in Germany before 1870 when 'beet‐sickness was becoming a serious problem. The first control measure was the introduction of a clause into contracts forbidding the growing of beet after beet or mangolds. More effective measures, which were adopted in 1939, are described. In 1943, the Sugar‐Beet Eelworm Order was issued enforcing these measures over a wide area and extending them to cover all susceptible crops.Effective control measures may result in a reduced rate of spread of the beet eelworm but cann

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06745.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Hatching experiments were carried out with potato‐root eelworm cysts (a) from plant pots containing different numbers of earthworms, and (b) from worm casts. Cysts from these sources differed from controls in the following ways: (1) more larvae emerged, per cyst; (2) the larvae emerged sooner; (3) more cysts produced larvae; (4) the number of emerging larvae, per cyst, increased with the number of earthworms.Examination of the contents of cysts isolated from worm casts showed that, compared with controls, 145% more eggs hatched; it also indicated some of the limitations of the ‘per‐cyst’ basis of expressing

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06746.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

The uses of inorganic compounds of mercury for the control of plant pests is reviewed, and a summary of the relevant chemical and physical properties of the compounds concerned is given. On chemical evidence a working hypothesis is propounded showing that all compounds may be expected to decompose into metallic mercury.A pot technique is described by means of which a correlation can be obtained between the effective mercury content of a given soil sample and the rate of growth of wheat seedlings. The mathematical treatment of the results is described, and the validity of the pot technique is verified by statistical analysis of results. Using the pot technique it is shown that volatilization losses are insignificant but that mercury is slowly rendered ineffective by the formation of mercuric sulphide. The effect of sulphur‐reducing bacteria is considered and the influence ofVibrio desulpkuricanson mercury is studied in detail.Experimental evidence obtained by the pot technique is produced to show that mercurous chloride slowly decomposes in the soil giving mercury and mercuric chloride, mercuric chloride rapidly decomposes into mercury and mercurous chloride, and other inorganic compounds decompose directly into mercury. The working hypothesis is substantiated in all major aspects.The uses and properties of the organo‐mercury compounds are then discussed. Type compounds selected are ethyl mercury phosphate, phenyl mercury acetate and methoxyethyl mercury acetate.Using the pot technique it is shown that the formation of organo‐mercury clays takes place and that these clays decompose giving metallic mercury. A mechanism is sugg

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06747.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY