摘要:

The use of sodium azide and organic acid azides for the control of potato root eelworm has been investigated: in suitable conditions they were effective both in greenhouse tests and in field trials. The biological activity of azides has been shown to arise from liberation of undissociated hydrazoic acid. The acid is only liberated in effective quantities in acid soils, but in such soils it is decomposed with formation of nitrogen. Organic acid azides are decomposed by a wide range of dust diluents and by soil, and there is some evidence that in diluents the main decomposition reaction is the formation of isocyanate by the Curtius rearrangement, whereas on wet soils extensive hydrolysis occurs giving hydrazoic acid, which is subsequently decomposed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00462.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Techniques for determining the influence of various substances on the rate of larval emergence from cysts of the beet eelworm are described. There is no significant difference between the rates of larval emergence in glutamic acid, galactinol, inositol and water; the rate of larval emergence in beet diffusate, on the other hand, was significantly higher. Studies of larval emergence in carbohydrates suggest that the cyst population used in the experiments was heterogeneous, consisting of two types of cyst which have different reactions to stimulation at different concentrations. The significance of root exudates in relation to beet eelworm is discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00463.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

D‐D injected at 400 Ib./acre into light loam in two glasshouses in Wiltshire killed 93.9 and 91.5% of the eelworm population, respectively, in the 0–9 in. soil layer.Growing tomatoes in pots in house 1 on top of the treated soil resulted in an overall fall in eelworm population to approx. one‐seventh of its original value. Tomatoes grown in the treated soil in house 2 built up the population to approx. times its original level.Combined treatments, using solubilized cresols as a surface seal instead of water, increased the kill in the 0–3 in. soil layer, but a higher degree of kill here is still required.All populations have been estimated by the root diffusate te

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00464.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

The resistance to low tensions of dissolved oxygen over periods ranging from less than a day to a week was determined for rainbow trout (Salmo gairdneriiRichardson), perch (Perca fluviatilisL.), roach (Rutilus rutilus(L.)), and mirror carp, a domestic form of the common carp (Cyprinus carpioL.) at 10°, 16° and 20°C., tench (Tinea tinea(L.)) at 10° and 16°C., dace (Leuciscus leuciscus(L.)) at 16° and 20°C., chub (Squalius cephalus(L.)) at 20°C., and bleak (Alburnus alburnus(L.)) at 16°C.At each temperature period of survival decreased with fall in oxygen tension.Rise in temperature between 10° and 20°C. reduced resistance to lack of oxygen of all species except rainbow trout, in which there was no significant difference between resistance at 16° and 20°C. Rise in temperature between 10° and 16°C. did, however, lower resistance considerably.Tench were the most resistant to lack of oxygen and, in general, trout were the most susceptible. At 20°C. mirror carp required a higher tension of oxygen to enable them to survive for a week than did rainbow trout, but for shorter periods could withstand much lower tensions than rainbow trout; at 10° and 16°C. their resistance was intermediate between that of tench

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00465.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Flax was grown in prepared composts containing different levels and ratios of nitrogen, phosphorus and potassium. When the cotyledons were inoculated withPolyspora liniLaff. the incidence of the seedling phase of the disease was not influenced by nutrient treatments, all plants being attacked. In such inoculated plants the lowest incidence of the stem‐break phase of the disease occurred in composts deficient in phosphorus. Increasing doses of the phosphatic fertilizer were associated with increases in susceptibility to stem‐break as well as in plant height and fibre yield. Small additions of the fertilizer produced little effect. In one experiment the incidence of stem‐break was directly and very significantly correlated with the percentage of phosphorus in the plants when nitrogen and potassium were held constant. Significant correlations were not found to exist between the incidence of stem‐break and the percentage of nitrogen or potassium in plants when the other two appropritate variables were held c

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00466.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

A wilt disease of Brussels‐sprout plants caused byVerticillium dahliaeKleb, is described. Field observations indicate that the disease is more severe in a wet than in a dry season, the various stages of the pathological symptoms appearing earlier and developing more rapidly. This was corroborated by experiment; under dry conditions the onset of wilt symptoms was delayed and the severity of attack diminished. Since nine different strains and/or species ofVerticilliumwound‐inoculated into Brussels sprouts failed to induce wilt, and since the isolate from this host proved to be non‐pathogenic to a wide range of plants usually susceptible to attack byVerticilliumspp., it is suggested that theV. dahliaefrom Brussels sprouts is a distinct physiological strain. Variations in the amounts of the different chemical constituents of the soil (calcium, nitrogen from two different sources, phosphate and potassium) have no apparent effect upon the incidence of disease. The pathogen is not seed‐borne but it may be spread by the dissemination of infected plant tissues. Some control measures are suggested and farmers are advised to grow in the infected soil runner beans, cauliflower and broccoli which are resistant to attack by this

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00467.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

In experiments on skin‐spot disease of potatoes, caused byOospora pustulansOwen&Wakef., Kerr's Pink proved the most susceptible of twenty‐four commercial varieties; Arran Banner, Majestic and King Edward were highly susceptible; Home Guard and Golden Wonder were highly resistant.Thymol and tetrachlornitrobenzene, applied as dusts to pits of potatoes at lifting, did not give satisfactory control of the disease. The efficacy of an organo‐mercury dip treatment at lifting time was confirmed.The incidence of the disease was considerably decreased by storing tubers in boxes instead of in pits, by digging the crop about a month before normal harvest, or by cutting the haulms at this time and digging at the normal time.Ware tubers showed a significantly higher infection than seed tubers of the same crop, indicating that susceptibility of tubers increases towards maturity.The difference in eye infection between varieties may not be related to that of general superficial infection. It is suggested that, in future, the assessment of varietal susceptibility should be based upon the degree of eye infection, which is in practice the measure of the economic importance of the disease. Tubers having pustules at or near all the eyes gave markedly reduced sprout emergence and plant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00468.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

A study of the development of skin spot in the potato variety Kerr's Pink has shown that humid conditions, both before and after infection byOospora pustulans, increase the incidence of the disease. The results of inoculation experiments have indicated that infection of the tuber does not take place much before the normal time of lifting.It has been found that the pathogen may enter the tuber by way of the lenticels, and that invasion of the cortex and the production of a cork cambium takes place shortly after infection. Some damage to buds was observed within 16 days of inoculation. Although the affected pocket of cortical tissue soon dies, discoloration of the periderm is not apparent until much later. It is suggested that this may be the reason for the comparatively long period which elapses between infection and the appearance of skin‐spot symptom

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00469.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

By using the detached‐leaf technique and Black's series of differential host varieties, seven physiologic races ofPhytophthora infestans(Mont.) de Bary have been distinguished as occurring in Northern Ireland. Six were found at the Dunanney potato variety trial plots, namely: race 1; race 2; race 4; race I, 2; race 1,4; and race I, z, 4. The remaining race, race 0, was isolated from the commercial potato crop.In a survey, comprising seventy‐three isolates, of the physiologic races occurring in the commercial potato crop, only race o and race 4 were found (3 and 70 isolates respectively).Certain modifications to the detached‐leaf technique have given improved results, including the formation of normal lesions and the elimination of atypical infections showing sparse sporulation.The variation in the host‐parasite reaction of the detached leaves and the identity of the common race in commercial potato crops are di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00470.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

When tomatoes were planted in steamed soil inoculated with spores ofDidymella lycopersiciKleb., a large proportion became infected, but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro‐organisms before inoculation withD. lycopersicireduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion ofD. lycopersicispores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants. Steamed soil remained susceptible to infection byD. lycopersicifor 4 months.D. lycopersicisurvived in a glasshouse soil over the winter, but the number of diseased plants was small. Cultivation may lessen the amount of disease by burying most of the infected surface layers of the soil. The peak of infection under glass occurred in May. The amount of disease and the yield were correlated, but with severe infection the yield varied with the time of infection and the distribution of diseased plant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1957.tb00471.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY