ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02484.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Fifteen series of aryloxyacetic, α‐aryloxy‐propionic, ‐butyric and ‐isobutyric acids and the corresponding arylthio‐analogues have been synthesized and their growth‐regulating activity has been assessed in the tomato‐leaf epinasty, wheat cylinder and the pea curvature tests. It is shown that in general arylthio‐derivatives are less active than their aryloxy‐analogues. Although for a cell elongation response the presence in the molecule of an a‐hydrogen atom is usually necessary, three exceptions to this generalization have now been found. A lower activity in the 3:5‐dichloro‐ compared with the 2:6‐dichloro‐compounds has been demonstrated. Evidence is presented to show that an ortho hydrogen atom in the nucleus is not an essential requirement for cell elongating activity as is

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02485.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Application of some growth substances markedly stimulated flowering laterals of the hop plant. The effect was specific to certain compounds and varied between varieties of hops and in the stage of flower development. The initial stimulation was not maintained by repeated application of the chemical, and untreated control laterals yielded a greater weight of cones with a higher soft resin content.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02486.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

A number of isosteres of DDT and related compounds have been synthesized and examined for insecticidal activity using the grain‐weevil, locust and cotton stainer. A marked loss of activity follows replacement of the chlorine atoms of DDT by methyl and hydroxyl groups. In the nitroalkane series, the optimum structure for maximum toxicity was present in i:i‐di‐/>‐chlorophenyl‐2‐nitropropane. The significance of these results has been reviewed in the light of current theories of DDT structure and activity. Many of the compounds expected to be toxic were found not to be so, and this inactivity can be attributed either to the initial hypotheses being invalid or to the operation of biological factors preventing concentration of the compound at the sit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02487.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The proportion of honey‐bees infected withNosema apis(Zander) declines in summer as the old infected bees die, for they cease to transmit their infection to the newly emerged individuals during the flying season.N. apisspores survive the summer on combs contaminated with infected faeces during the preceding winter. Although bees clean the combs during the summer, all infected material is not removed, and even well‐used brood comb, which has been repeatedly cleaned by bees, can carry infection. Only a few bees may contract infection in the autumn from these faeces, but they join the winter cluster and initiate the next outbreak of the disease. Transferring a colony on to clean comb early in the spring or summer removes the source of the disease, and it then disappears when all the old infected bees die.Old broodless comb can be sterilized quite simply by fumigation for a few days with the vapours of formalin or glacial acetic acid. Acetic acid is preferable, because it does not poison any honey or pollen in the combs. Formaldehyde can safely be used only with empty combs.The autumn is the best time for treating colonies chemotherapeutically, because the combs are then cleanest and the few bees which are infected can be cured during the winter. The drug can be incorporated in the syrup normally fed to colonies in autumn, and there is no risk of seriously contaminating subsequent honey crops. However, such treatment cannot eliminate the disease because sufficient spores remain on the combs for the disease to start again when the drug supplied in the winter stores is exhaus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02488.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The air‐flow and its variations in sixteen insect suction traps of five different types have been measured, using regularity of air sample size as the criterion of efficiency. Traps with the air‐filtering cone enclosed in a cylinder and using axial flow fans with single‐phase capacitor‐start‐and‐run or three‐phase motors are most efficient and can have normal working limits of + 4 % of the mean air delivery.However, for smaller traps which are to be used only close to the ground or in cover, the original type with exposed cone and shaded‐pole motor is quite satisfactory provided certain precautions are taken. Normal working limits of 5 8 % are then obtained.These errors are derived in detail and the expected errors in more extreme conditions and with other trap

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02489.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02490.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Cauliflower mosaic in south‐west England is most prevalent where there is a sequence of brassica crops that overlap in time. Broccoli yields can be increased by using plants raised in seed‐beds separated by half a mile from old infected plants. Surrounding seed‐beds with crops of kale or barley decreased the incidence of mosaic even when the seed‐beds were only 5 yd. from infected plants.Most plants infected at harvest contract infection after transplanting. A plant infected in the seed‐bed or early in the growing season can produce a group of infected plants immediately around it, and almost as many farther away. Spread can occur in the same pattern from these secondarily infected plants.Loss of yield is correlated with the time plants are infected. Plants infected as seedlings produce little or no curd or seed, whereas those infected when nearing maturity yield almost as well as uninfected plants.The movement of alate aphids is positively correlated with the numbers of infectedplants, and symptoms in field plants generally appear 8–9 weeks after infection.Cauliflower mosaic virus occurs in strains distinguishable by the severity of symptoms

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02491.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

The rosette virus was transmitted to groundnut plants, if previously etiolated, bymechanical inoculation of juice with ‘Celite’ addition; but only a small proportion of the inoculations succeeded.Aphis craccivora (Koch), the known vector, transmitted the virus by feeding on germinating groundnut seeds; and from this fact we developed an experimental technique that is convenient and flexible.Different races of this species appeared to vary in inherent efficiency in transmission, and one failed ever to transmit. Within races that could transmit, all larval forms and alate and apterous adults might transmit; but alatae were sometimes significantly more efficient than apterae, and at other times the converse held. A field experiment showed that wingless forms, moving over the soil surface, might play a predominant part in secondary spread around a rosetted plant.Comparative tests with groups of I, 2, 3 and 4 infective aphids supported the hypothesis that infections by this vector are individual and independent.Single aphids, tested for 24 hr. on 10 successive days without access to an outside source of virus, might infect on any day up to the tenth. Similar results were obtained in a succession of I hr. tests on a single day. In the infected seed the virus rapidly became available to feeding aphids; previously non‐infective aphids acquired the virus by feeding on a seed during the third day from the first exposure of this seed to infective a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02492.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

Cacao virus iA, the most important and prevalent of the viruses that attack cacao in the Gold Coast, occurs in strains that differ widely in their virulence towards cacao. Outbreaks usually contain trees infected with different strains and individual trees are often infected simultaneously with more than one strain; this can be demonstrated by coppicing the trees, and by inoculating sets of test plants with grafts from different parts of one tree. Neither mild nor virulent strains seemed to be consistently dominant in roots or in other parts of cacao trees.Cacao plants infected with mild strains were nearly always protected against the effects of infection by virulent strains; however, virulent strains entered hosts already infected with mild strains, but usually without causing any symptoms unless the plants were coppiced. The severe symptoms that developed on new growth from such coppiced plants were seldom repeated in later growth. Mealybugs transmitted the virulent strains from leaves with symptoms characteristic of infection by the latter, but not from leaves free from such symptoms. These results suggest that the multiplication of a virulent strain is impeded in plants infected with a mild strain.In the field, infection with a mild strain protected mature trees against the effects of virulent strains spread by mealybugs. During 3 years in which 273 out of 387 previously uninfected trees became severely diseased, only 35 out of 416 infected with themildstrain developed symptoms of infectionwiththevirulent strain. Five years after infection with the mild strain, trees were yielding I pod per tree more than in the year they were infected, whereas the decrease on trees infected with the virulent strain was 16 pods per tree. Some limitations in the practical application of protection by mild strains, and objections to its use as a control measure, are discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1955.tb02493.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY