摘要:

Summary.1Three varieties of hops which had previously shown complete resistance to the attacks ofS. Human, became slightly infected in the greenhouse in the spring of 1926.2The susceptibility shown was only temporary; all the infected plants during May and June again acquired their power of complete resistance.3The conidia produced on an “immune” plant proved unable to infect that plant, although able to infect a susceptible variety.4It appears probable that abnormal weather conditions (possibly low temperature) brought about the temporary susceptibil

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07011.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1Twenty composite plants were built up by grafting either a scion of an immune variety of hop on a susceptible stock, orvice versa. Inoculation of young leaves of the scion, after a considerabll growth of the latter had taken place since grafting, showed that no change had been effected in the varietal immunity or susceptibility in relation toSphaerotheca Humuli.2In the above experiments, scions of six different immune varieties were grafted on stocks of four different susceptible varieties and scions of four different susceptible varieties were grafted on stocks of five different immune varieties.3The results obtained render it improbable that immunity or susceptibility toS. Humuliis connected with any translocatable substance in the hop plant.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07012.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1A “foot‐rot” disease of young tomato plants from Guernsey caused byRhizoctonia solanihas been investigated.2The disease is least prevalent on dry open soils; it is most severe at temperatures ranging from 16°C.‐20°C3The degree of infection was increased by stable manure; slightly decreased by ammonium sulphate; apparently unaffected by lime, potassic and phosphatic manures.4Soil sterilisation by heat was the most effective and reliable means of controlling the disease. During the season the disease was checked by uspulun.5Control methods are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07013.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07014.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.A detailed account is given of the life history and parasites ofHylemyia (Chortophila) brassicae, the cabbage root fly. The various stages are described and figured. The egg is deposited in the vicinity of the roofs of Cruciferous plants, in the heads of cauliflowers, and in autumn on the leaves and cut stem of Brassicas. The period of the egg stage lasts from 3 to 5 days, the larva when full grown is smooth, white in colour, and possesses a caudal corona of well‐defined tubercles, one pair of which is bifurcate and serves as a means of identification. The maggots feed in the roots of Cruciferous plants, or in the heads of cauliflowers and turnips, while late in the autumn they may occasionally be found tunnelling in the midrib ofBrassicaleaves. The larval period lasts from 19 to 25 days. The puparium is reddish brown in colour and measures about 7 mm. in length. The length of the pupal stage is very variable and may occupy from an average of 16 days to 69 days. Pupation takes place in the soil in proximity to the plant. The adult is a dark grey insect somewhat resembling the home fly but is more bristly.There are three generations in the season; as a general rule hibernation is in the soil in the pupal stage.Four other types of larvae found associated with those ofH. brassicaein Cruciferous plants are described, the most important beingPhytomyza rufipesMeig.A detailed description of the parasites ofH. brassicaeis given; these are the larva of the Staphylinid beetleAleochura bilineataGyll., the CynipidCothonaspis rapaeWestw., the BraconidDacnusa stramidpesHalid. and the Anthomyid flyPhaonia trimaculatuBouché, the larvae of which are carnivorous and feed uponH. bassicuelarvae. There are also described a Proctrotrupid,Emllonyx EigatusNees., which is parasitic upon the larva ofAbochara bilinmtaGyll. and a Tachinid fly,One&agilisMeig., which is associated withH. brassicae, although the exact relationship has not been determined.An unusual form of parasitism of the adult fly by some kind of micro‐organism is also figured and briefly descr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07015.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.1The toxicities toAphis rumicisL. of the fatty acids from formic to stearic and of the sodium and ammonium salts and methyl esters, applied as spray fluids, have been quantitatively determined. Two un‐saturated acids, undecenoic and oleic, are included.2There is a rise in toxicity of the acids with increase of molecular weight as the series is ascended from acetic to undecylic acid. Formic acid is exceptional. Beyond undecylic acid, there is a fall in toxicity, and acids higher in the series than tridecylic show only slight toxic action.3The sodium salts of the fatty acids are in most cases much less toxic than the corresponding acids, though the difference is less marked with the higher acids. Oleic acid and sodium oleate are of the same order of toxicity.4The ammonium salts are also generally less toxic than the corresponding acids, but the differences are much less than in the case of the sodium salts. With some of the higher acids,e.g. myristic and oleic, neutralisation with ammonia increases toxicity. The relatively high toxicity of the ammonium salts may be due, at least partly, to liberation, by hydrolysis, of free fatty acid in a very finely divided state.5Methylation of the fatty acids reduces toxicity; all the methyl esters are less toxic than the acids or ammonium salts.6Both the ammonium salts and the methyl esters show, like the acids themselves, increase of toxicity with increase of molecular weight up to a certain point. The formates are exceptional.7The fatty acids do not show marked toxicity to the eggs ofBelenia tetralunariaHüfn. at concentrations below 2 per cent.8Possible relationships between certain physical properties (physical state. volatility, dissociation constants, partition coefficients and surface tension) of the fatty acids and their insecticidal action are discussed.9Determination of partition coefficients as between olive oil and water and comparison of the figures with the relative toxicities show a steady rise in toxicity with a decrease in the partition coefficients (water/oil) from acetic to capric acid. Formic acid is again exceptional. With lauric and oleic aoids there is a break in the correlation. The bearing of the solubility relationships of the acids on these results is consider

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07016.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Summary.A study of the wireworm problem in Great Britian shows that this pest is especially important in areas devoted to intensive agriculture and commercial horticulture.In addition to most farm crops, strawberries, various flowers and tomatoes me particularly susceptible to wireworm attack and because these crops 60 often occur on new land, losses due to the activities of the pest are frequent, and serious. The nature and extent of wireworm attack, both in the field and in glasshouses, is described herein.Examination of weeds growing in infested fields indicate that wire‐worms are found in numbers at the root of some plants such as couch‐grass,Agropyrum repens, and yarrow,Achillea millifolium, while very few occur at the roots of pants like chickweed,Stelkria media, gout‐weed,Chenopodium albumand annual nettle,Urtica urens.Field observations on the movements of wireworms in the soil throughout the autumn, winter and spring indicate that there is a definite downward migration in autumn and an upward migration in spring. Correspondingly wireworm activity in the surface soil was noted to be at its height in September and October, and March, April and May.Expehents on the use of baits as a means of assembling wireworms, indicated that large numbers will collect to baits such as wheat, oats, and bran, and moreover these baits can be used to attract wireworms from the roots of crop plants, on which they are feeding. Because of the seasonal movements of wireworms, baiting is best carried out in autumn or spring.Calcium cyanide in granular form has been found to be highly toxic to wireworms and used, in connection with the baiting, at the rate of 2–3 Ib. per 100 yd. of bait row, destroyed 75–100 per cent. of the wire‐worms assembled.Based on the results of experiments conducted in Lincolnshire, Hertfordshire, and West Sussex, during the years 1925 and 1926, and involving 10,000 wireworms, recommendations are made for the control of wireworms by means of baits and the use of calc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07017.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY

摘要:

Book reviewed in this article:The Biological Relations of Optically Isomeric Substances. By ArthurR. CushnyEnzynzes: Properties, Distribution, Methods and Applications. By SelmanA. Waksmanand WilburtC. DavisonThe Composition and Distribution of the Protozoan Fauna of the Soil. By H. SandonHydrogen Ion Concentration. Its Significance in the Biological Sciences and Methods for its Determination. Volume 1. Principles of the Theory. By LeonarMichaelis

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1927.tb07018.x

出版商:Blackwell Publishing Ltd    

年代:1927

数据来源: WILEY