摘要:

Existing test methods for the moth‐proofness of wool were compared in inter‐laboratory experiments and found to be lacking in accuracy and agreement between laboratories.Several factors influencing the usefulness of such a test method were investigated, and it was found that a considerable gain in accuracy could be reached if weight loss due to larval attack on test samples was referred to weight loss obtained with a standard wool serge impregnated with a standard moth‐proofing substance. Apart from this principle, improvements in the general testing procedure, including the number of test samples and test animals used, the definition of weight loss and the introduction of strict randomization procedures proved to be valuable.As a provisional reference standard, wool serge impregnated with dinitro‐α‐naphthol was adopted. A tolerance level for the moth‐proofness of wool serge w

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02235.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

For studying the population of pea‐midge cocoons, larvae and pupae in the soil, a new method of examining the ‘float’ obtained from washing soil through the wet‐extraction apparatus is described.Examination of soil samples in the summer of 1957 from fields which carried heavily attacked pea crops in 1956 indicated that pupae were present at depths of 0–3, 3–6, 6–9 in., respectively, from 18 June onwards, and that the peak emergence of midges was in the period 28 June‐2 July; observations on adult activity in pea fields confirmed this. Small numbers of pupae were recovered throughout July.Similar studies on pea fields in 1957 showed the build‐up of the cocoon population and the rate of pupation of this generation of larvae. The first flight of 1957 was composed of individuals from the 1956 generation and was far larger than the second flight, which was composed of some 1956 generation and part of the first 1957 generation.There were indications that increases of temperature might accelerate pupation with a resulting earlier emergence of adults.The size of midge populations recorded from soil from green pea and dry‐harvesting pea fields tended to be similar and appeared to be rel

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02236.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Laboratory tests with a nuclear polyhedral virus disease ofHeliothis armigeraindicated that it was more infective and had a shorter incubation period in the younger instars than in the older larvae.Larvae on cotton plants sprayed with an aqueous suspension of the virus became infected; mortality depended on the number of polyhedra applied to the plant irrespective of the concentration in the suspension. Spraying with the virus seems unlikely to control bollworm in Uganda, but might do so where it is not already endemic and where bollworm numbers fluctuate more during the year.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02237.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

A virus disease that resembles wheat striate mosaic was found affecting up to 5% of the plants in English wheat fields in 1956. Symptoms on wheat included fine chlorotic striae, followed by stunting, general chlorosis, and death of plants. Other hosts included oats, barley, rye, perennial rye grass and Italian rye grass.The virus was transmitted byDelphacodes pellucida(Fabricius) (Homoptera, Delphacidae). A few of the insects were already infective when caught in the field. The percentage of infective individuals was increased by feeding the insects for 24 hr. or longer on diseased plants, and up to 56% became infective after feeding on diseased plants for 3 days. Non‐infective insects were unable to transmit the virus until from 8 to 36 days after they first fed on diseased plants, but they frequently remained infective for the remainder of their lives, up to 10 weeks after feeding on a diseased plant. Infective insects seldom transmitted the virus during test feeds as short as 30 min. When fed for 1 or more days on each test plant, some insects infected many plants in succession, others seldom infected test plants even if they fed as long as 7 days on each. The virus was transmitted through the eggs to as many as 88% of the progeny of infective females, and to some of the progeny of a few females that had failed to infect wheat test plant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02238.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

A strain of cucumber mosaic virus isolated from a spinach plant in 1946 was readily transmitted byMyzus persicaeuntil 1955 when it lost this property, although it was still being propagated in conditions in which other strains remained transmissible.M. circumflexusalso transmitted other strains but not this one. It was transmitted as readily as other strains byAphis gossypiiandMyzus ascalonicus. M. ascalonicustransmitted less frequently thanAphis gossypii.Transmission of the spinach strain by other aphids did not make it transmissible byMyzus persicae; nor did propagation in different plant species or several passages through spinach. In 1955 the spinach strain was occasionally transmitted byM. persicae, but the cultures isolated in this way were no more readily transmissible by the aphid than was the bulk culture maintained by manual inoculation of sap, and after a few weeks all cultures ceased to be transmitted byM. persicae.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02239.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The infectivity of sap expressed from the lower epidermis stripped from leaves systemically infected with potato virusY, henbane mosaic virus or tobacco mosaic virus was compared with that of sap from the underlying mesophyll. Results suggested that the concentration of virus in each of the two tissues was about the same.Ultra‐violet irradiation of leaves infected with potato virusYor henbane mosaic virus greatly reduced the infectivity of sap expressed from subepidermal tissue

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02240.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Raspberry ringspot virus (RRSV) was found in eastern Scotland and Wiltshire infecting several varieties of raspberry, several weed species and sugar beet. Serological tests, and protection tests inPetunia hybrida, showed that isolates from different host species found at several localities in eastern Scotland were more closely related to one another than to the isolate from Wiltshire. RRSV was readily transmitted toChenopodium amaranticolorby mechanical inoculation of sap from diseased raspberry but less readily to other species. Both the symptoms shown byC. amaranticolor, French bean, tobacco andPetunia hybrida, and its behaviour in serological and plant‐protection tests, distinguished RRSV from tomato black ring, raspberry yellow dwarf, tobacco ringspot and cucumber mosaic viruses. Preparations of RRSV lost infectivity when diluted 10‐4, kept for 3 weeks at 18° C., or when heated for 10 min. at 70° C. but not at 66° C. RRSV was precipitated without being inactivated by ammonium sulphate, ethanol or acetone. It was inactivated at pH 3.The beet ringspot strain of tomato black ring virus was isolated from the raspberry varieties Malling Seedling V and Malling Exploit by mechanical inoculation of sap toChenopodium amaranticolor, but not from other varieites growing in virus‐infested soil.RRSV and the beet ringspot strain of tomato black ring virus are soil‐borne. They infected plants grown under glass in soil collected from several different fields: the incidence of infection differed in different soils, but infection by each virus was favoured by the same samples of soil. Infection with tomato black ring virus occurred equally in soil collected at different times of the year. Treatment with formaldehyde or parathion made soil non‐infective. Attempts to detect virus in extracts of virus‐containing soils, and to make autoclaved soils infective by watering them with virus suspensions or by growing artificially infected plants, failed, suggesting that infection depends on some factor other than free virus, possibly the presence

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02241.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Three isolates of turnip yellow mosaic virus and two other flea‐beetle transmitted viruses, turnip crinkle and turnip rosette, have many similar properties: thermal inactivation end‐point between 80 and 90° C.; dilution end‐point greater than 10‐4; longevityin vitroat about 20° C. at least 30 days. All were transmitted by mechanical inoculation to a wide range of cruciferous host plants, including many weeds. Turnip yellow mosaic virus infected onlyReseda odorataoutside theCruciferae, whereas rosette virus infected a few and crinkle virus many non‐crucif

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02242.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The discovery, occurrence and symptoms of crook‐root disease (Spongospora subterranea(Wallr.) Lagerh. f.sp.nasturtiiTomlinson) are described.Assessment of crook root in commercial watercress beds indicated that the disease increased with increasing distance from the water source, was more severe from October to April than from May to September, and affected brown more than green watercress.The healthier condition of plants near the fresh‐water inlets, compared with those growing further down the bed, was associated with the low concentration of zoospores.Water from the river Dene, Wellesbourne, contained a factor inhibiting crook root, which was shown to be calcium bicarbonate. In laboratory tests, increasing concentrations of calcium bicarbonate from 62 to 540 p.p.m. gave an increasing degree of control of the disease. The same effect was shown in a small field test.The combined (Ca + Mg) bicarbonate content in eighty‐seven spring and artesian waters supplying diseased watercress beds in various counties varied, with one exception, from 282 to 401 p.p.m. The only bed fed by water with a higher total bicarbonate content (525 p.p.m.) was free from crook root.It was shown that solutions containing 350–750 p.p.m. calcium bicarbonate had no effect on the germination of zoosporangia or the activity of zoospores.Certain resemblances are noted between the control of crook root by calcium bicarbonate and the control of club root of brassicas

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02243.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Zinc, used as zinc sulphate at 0.5 p.p.m., was found to inhibit the growth ofSpongospora subterranea(Wallr.) Lagerh., f.sp.nasturtiiTomlinson, the cause of crook‐root disease of watercress. A relatively insoluble finely powdered glass frit containing zinc oxide (zinc frit) largely prevented infection by this fungus when added, at 0.2 g./350 ml., to water in which watercress was growing.In field trials made in 1955‐56 on brown watercress at Bere Regis, Dorset, and on green watercress at Greatford, Lincolnshire, zinc frit was applied at two rates of 1 and 1/2 lb. per sq.yd. After 4–8 weeks, plants in the treated beds grew more strongly and root infection was reduced considerably. Untreated control beds remained heavily infected from September to April but, in the treated beds, the disease was greatly reduced from November to January though, by April, this effect had largely disappeared. Disease control at both places was associated with increases in total crop and individual plant weight. Field trials in 1956‐57 gave similar results.When zinc frit was shaken with distilled water for 24 hr. a solution containing 0.21 p.p.m. zinc was obtained, but if watercress plants had been grown in the water before it was shaken with the frit the solution contained 2.82 p.p.m. zinc. The treated water was found to contain 16 p.p.m. CO2which had a solvent action on the frit. Field tests showed that plants in watercress beds liberated sufficient CO2into the water to bring into solution a fungitoxic concentration of zinc. Observations on the crook‐root fungus showed that the suppression of the disease by zinc was caused by the killing of the zoospores.The zinc content of watercress in beds treated with zinc frit was at a safe level for human consumption and the zinc content of the outflow water from such beds was non‐toxic to trout (Salmo gairdneriiRichardson).A previous theory on the release of metals from glass by plants is discussed in relation to the experiments described on the release of zinc fro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02244.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY