bluuebunny/crossref_metadata_2025_split huggingface dataset:
Verticillium Wilt Of The Hop
Authors: KEYWORTH W. G. 
Published: February 2008

The two hop varieties Fuggle and OR55 have respectively low and high resistance to wilt caused by virulent strains of Verticillium albo‐atrum. When the pathogen enters through the roots it grows vigorously in the stems of Fuggle plants and slightly in the stems of OR55 plants. Leaf symptoms are correspondingly severe and mild.If Fuggle stems are grafted on to OR55 roots and vice versa, and the fungus thus invades the stems from roots of the opposite resistance type, it now grows slightly in the Fuggle stems and vigorously in the OR55 stems. Leaf symptoms are correspondingly mild and severe, and thus wilt intensity is related to the variety of root and not to the variety of stem. Evidence is available which shows that this is not due to the transfer of a ‘resistance factor’ generated in the resistant roots.The variety Fuggle has low resistance to virulent strains of V. albo‐atrum but high resistance to mild strains. As in the case of varietal type this resistance is expressed by vigorous or slight growth of the fungus in the stems (and corresponding leaf symptoms) when the fungi are introduced through Fuggle roots. When they are directly inoculated into the stems there is no differentiation of the strains. If a small inoculum is used both strains induce mild wilt. If a large inoculum is inserted into a pith cavity both strains induce severe wilt. The reaction of the Fuggle stem is thus governed by conditions relating to the type of invasion and not to the strain of pathogen.It is suggested that this also applies with root inoculations. Normal stems of both Fuggle and OR55 varieties have a high resistance to invasion from a weak source of the pathogen (such as exists in a highly resistant root), and the fungus can invade the stems heavily only from a suitable inoculum source (i.e. a root of low resistance).Heavy invasion of the stem from a root may be due to

A lowering of stem resistance by:

toxins diffused from the invaded root,
an impairment of normal root function.

An increase in invasive power of the pathogen by:

the establishment of a ‘food base’ in the root,
the diffusion of a ‘fungal accelerator’.

The main conclusions that the primary focus of the disease is in the root and that the normal stems of all varieties possess a similar (and possibly high) resistance is supported by other researches on Fusarium wilt of tomatoes and other wilt diseases and may be of general application.
OBSERVATIONS ON THE INCIDENCE OF CLUB‐ROOT DISEASE OF BRASSICAE IN LIMED SOILS IN RELATION TO TEMPERATURE
Authors: COLHOUN JOHN 
Published: February 2008

When cabbage plants growing in artificially contaminated, heavily limed soil were maintained at greenhouse temperatures (mean about 23d̀ C.) for periods of up to 12 days and then at shade temperatures in an open‐air verandah (mean not exceeding 12.5d̀ C.) for up to 21 days only slight attacks of club root developed. Exposure to greenhouse temperatures for at least 6 days and then in a verandah to a mean air temperature of about 16d̀ C. permitted severe attacks to develop. A very severe attack occurred when plants remained in the greenhouse throughout an experiment, but all the plants were healthy when verandah temperatures only were employed.It is suggested that exposure to favourable temperatures for infection and development of the disease for 12 hr. daily may permit the occurrence of a moderately severe attack.
FIELD STUDIES ON THE INFLUENCE OF WEATHER CONDITIONS ON EGG‐LAYING BY THE CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE BCHÉ. I
Authors: MILES MARY 
Published: February 2008

The duration and intensity of egg‐laying by the spring generation of Erioischia brussicue Bché has been studied by removing daily the soil around the stems of cabbage plants on an observation plot. In 1952, eggs were first found on 22 April; the peak period of egg‐laying lasted from 30 April to 22 May, and in the last week of May the rate of egg‐laying declined rapidly. In the peak period the rate of egg‐laying was 5–46 eggs per day per plant with a mean rate of 23 eggs per day per plant. The spring infestation on observed plants was 258–817 eggs with a mean of 533 eggs per plant.Variation in the daily rate of egg‐laying was associated with weather conditions. Warm sunny weather induced heavy egg‐laying but in cool, wet and windy weather fewer eggs were laid.A summer peak of egg‐laying associated with the second generation of E. brassicae occurred in late June and early July. Attack in summer was less intense than in spring, a total of 1298 eggs being recorded for the summer peak period (24 June‐14 July) compared with 5796 eggs during a similar period (30 April‐20 May) in spring.Observations on the numbers of flies that emerged from alternate plants on the observation plot showed that the low rate of egg‐laying in summer was not the result of a lack of adults. Consideration of biotic and climatic factors suggested that while high temperatures and long periods of sunlight stimulated the summer flies to great activity the environment provided little food to sustain them, and in consequence they did not survive to complete oviposition.The puparia were collected from the undisturbed alternate plants in order to obtain information on the numbers of E. brassicae that reached maturity. It was estimated that 5–6% of the eggs reached the pupal stage; approximately two‐thirds of the puparia gave rise to flies and one‐third were parasitized. About 9% of the puparia remained viable in the soil to give rise to the following spring generation, about 90% having given rise to flies in the year in which they were formed.
TESTS OF SYNERGISM BETWEEN NICOTINE AND THE PYRETHRINS
Authors: TURNER NEELY , BLISS C. I. 
Published: February 2008

Synergism between nicotine and pyrethrum applied by injection to adult Oncopeltus fasciatus Dal. has been reported by Turner (1951).When these insecticides were applied alone and as a mixture to adult Tribolium castaneum Hbst., using a dipping technique, the data indicated that independent joint action occurred. Similar action could be eliminated because the two insecticides had varying relative potency.Since the effect of the pyrethrins has been short‐lived in some insects, it was postulated that the absence of synergism might be caused by failure of the nicotine to reach a site of action while the pyrethrins were still acting.Application of nicotine, followed later by treatment with pyrethrins, gave evidence of synergism. A test in which the interval between treatments was varied from ¾ to 6 hr. showed that toxicity was greatest with the shortest interval between applications, and evidence of synergism had practically disappeared after 6 hr. The maximum amount of synergism observed was about twofold.
BIOASSAY SYSTEMS FOR THE PYRETHRINS: IV. STOICHIOMETRIC RELATIONS WITH PYRETHRUM SYNERGISTS*
Authors: BLACKITH R. E. 
Published: February 2008

The sharp limitation of synergistic action when equimolecular proportions of the pyrethrins and some of their synergists are tested against flying mosquitoes has been confirmed when such mixtures are employed in assays using Calandra granaria L. crawling on oil‐films on filter‐paper.Limitation of the relative potencies of pyrethrum‐synergist mixtures appears to be a general property, and except for piperonyl butoxide the limiting relative potency is attained at equimolecular proportions of insecticide and synergist.These observations are discussed in connexion with a general theory of insecticidal action.
BREEDING PEARS FOR RESISTANCE TO THE PEAR SCAB FUNGUS, VENTURIA PIRINA ADERH.
Authors: STANTON W. R. 
Published: February 2008

Clonal isolates of Venturia pinna, shown in a previous paper to differ in range of pathogenicity, have been used to inoculate the following pear seedlings: (i) resistant seedlings from families which appeared to be segregating for resistance under field conditions, (ii) two whole families of field‐resistant × field‐susceptible parentage.In (i), it was found that clones of the fungus could infect some of the seedlings hitherto regarded as field‐resistant. In (ii), segregation for susceptibility in the two families varied, according to the clone of the fungus used, from approximately a 1:1 ratio down to ‘all resistant’. Resistance to individual clones appeared to be dominant to susceptibility, but further data are required before attempting a complete interpretation.There was a general correlation between susceptibility to the different clones. Those that produced the most infection were isolated from the parental varieties of the seedlings. This correlation was not, however, complete and clones differing in host origin tended to attack different groups of seedlings.
THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES: I. DEVELOPMENT OF RESISTANCE TO DDT IN A STRAIN OF DROSOPHILA MELANOGASTER MEIG.
Authors: TATTERSFIELD F. , KERRIDGE JILL R. , TAYLOR JEAN 
Published: February 2008

Successive spraying with DDT suspensions of the adults of a wild colony of Drosophila melanogaster and the progeny of survivors enhanced the resistance to that insecticide.The rate at which resistance increased depended on: (1) the relative proportion of resistants to susceptible individuals, or (2) the intensity of selection as measured by the concentration of DDT, the proportion killed or on both. The resistance of the populations of the insects fluctuated considerably whether subjected to successive sprayings or not, and in one sprayed series there was some indication of a rhythm with peaks of susceptibility occurring at regular intervals.Enhanced resistance may show a change of slope in the probit log concentration regression line, leading to different relative values at different levels of mortality, or by a parallel shift of the regression line. The former appears to be a preliminary stage of selection and indicates a change in the frequency distribution within a population.Increasing the concentration of DDT, slowly or rapidly, may have enhanced resistances at an increased rate, but the series sprayed with the lower initial concentration reached finally the same end point, as judged by the values of log lc. 50.During the course of these experiments the insects developed sensitivity to carbon dioxide (used in anaesthesis). Its bearing on our work is considered in Part II.
STUDIES ON THE FEEDING OF MYZUS PERSICAE (SULZ.) ON RADIOACTIVE PLANTS
Authors: WATSON MARION A. , NIXON H. L. 
Published: February 2008

Adult apterae of Myzus persicae (Sulz.), were fed, after a period of fasting, on leaves containing radioactive phosphorus. The weight of sap imbibed by the aphids after varying feeding times was estimated by relating their radioactivity, at the end of each feeding period, to the activity per unit fresh weight of the leaf lamina on which they fed. The calculations were made on the assumption that 32P is uniformly distributed in the leaf tissues.The mean rates of uptake so estimated were about 10 μg. of sap for the first hour of feeding; 40 μg/hr. between 1 and 4 hr. feeding, and 17 μg./hr. between 6 and 24 hr. feeding. The decrease in apparent rate of uptake with the longer feeding times is attributed to loss of 32P in nymphs born during the feeding period.When aphids were fed on seedlings raised in water culture solution containing 32P no activity was detected after 5 min. feeding and an insignificant fraction after 15 min., but when the isotope was introduced by immersing the leaves for several days in the culture solution, aphids fed for 5 and 15 min. became appreciably active.The increase in rate of uptake after 1 hr. of feeding indicates that aphids do not start to feed normally until they reach the phloem, but the activity after short feeding times suggests that previously starved aphids feed to some extent on other tissues, possibly only on the epidermis.
FACTORS AFFECTING THE PRODUCTION OF LOCAL LESIONS BY PLANT VIRUSES
Authors: MATTHEWS R. E. F. 
Published: February 2008

Beans inoculated with tobacco necrosis virus were kept in the dark at different temperatures for 1 hr. before and 1 hr. after inoculation; in this experiment the number of lesions increased with temperature over the range 55–82° F.The effect of 30 min. periods of darkness before or after inoculation depended on the time of day, the number of local lesions usually being decreased. Prolonging the night period before inoculation sometimes increased the number of lesions.Light appeared to be more important than temperature in controlling the daily variation in susceptibility. However, in a test over a 30 hr. period this variation continued even when plants were placed under constant conditions before and after inoculation.When plants that had been kept in the dark were exposed to light of about 800 f.c. intensity for 1 min. immediately before inoculation the number of local lesions was doubled.
PHYSIOLOGICAL RACES OF PHYTOPHTHORA INFESTANS: A COMPARISON OF THE DIFFERENTIAL HOSTS AT THE PLANT BREEDING INSTITUTE, CAMBRIDGE, WITH THOSE OF THE SCOTTISH SOCIETY FOR RESEARCH IN PLANT BREEDING
Authors: HOWARD H. W. 
Published: February 2008

At the Plant Breeding Institute, Cambridge, there have been recognized three physiological races of blight (Phytophthora infestans), A, B and C; and at the Scottish Society for Research in Plant Breeding, Edinburgh, there have been used five races, A, B1, B2, C and D, obtained in the British Isles.It is shown that the two Cambridge types of differential hosts, AbC and ABc (where A= resistant to race A, a= susceptible to race A, etc.), are Ab1b2CD and AB1B2cD respectively on the Scottish scheme, and that the Cambridge races A, B and C correspond to the Scottish races A, B1 and C respectively.A number of blight isolates were tested on both the Cambridge and Scottish differential hosts. Isolates of race types A, B1, B1, C and D were found.The identification and origin of physiological races of blight, and the breeding of blight‐resistant potatoes, are discussed.
A METHOD FOR MEASURING THE NARCOTIC ACTION OF CHEMICALS USING THE GRAIN WEEVIL, CALANDRA GRANARIA
Authors: BRADBURY F. R. , ARMSTRONG G. 
Published: February 2008

A method of measuring narcotic potency is described. Grain weevils (Calandra granaria) are exposed to the narcotic vapour in 2l. round‐bottomed flasks illuminated from the bottom, and narcotic potency measured as number of grain weevils so affected as to be unable to climb the glass walls. Some common anaesthetics have been examined as an illustration of this method. Results are fitted by the probit planeY= A +b1 log α+b2 log t,where Y= a function of the number of insects affected (probit); α= the thermodynamic concentration of the narcotic vapour; t= time of exposure of insects to the narcotic vapour. The values of the coefficients b1 and b2 are discussed in relation to the biological action of the narcotic vapours.
WIND DIRECTION AND THE INFESTATION OF BEAN FIELDS BY APHIS FABAE SCOP.
Authors: TAYLOR C. E. , JOHNSON C. G. 
Published: February 2008

Bean fields are often attacked by Aphis fabae very heavily along the edges: and on a field at Rothamsted in 1948 the sides facing the wind during the primary migration had more colonies than those in the lee of the crop (Johnson, 1950). Additional observations on the distribution of colonies were made on six bean fields at Sutton Bonington in 1950–2.At Rothamsted in 1948 it was assumed that the more numerous colonies on the windward sides of the field followed a heavier deposition of primary migrants there, though the migrants themselves were not observed on the crop. In 1950–2 the locations of primary migrants, as well as of colonies, were recorded in three out of the six fields observed.
THE CONTROL OF BLOWFLIES INFESTING SLAUGHTER‐HOUSES
Authors: GREEN A. A. , KANE JOYCE 
Published: February 2008

A field experiment has been conducted to control blowflies which fell as mature larvae from railway wagons carrying domestic refuse and infested the soil at the sidings of a refuse collecting and sorting depot.The surface of the soil was treated so that the insects were exposed to insecticide both as migrating larvae and newly emerged adults. Dusts and emulsions of DDT and BHC were compared on the basis of equal cost. A method was evolved for obtaining quantitative measurements of the effectiveness of the treatments by trapping flies emerging from the soil.DDT was more effective than BHC, dusts were more effective than emulsions, and small quantities applied twice weekly were more effective than a correspondingly heavy dose applied monthly. DDT dust applied twice weekly was estimated to have killed 79.7% of larvae and pupae and 95.7% of emerging adults: overall control was 99.1%. Equally high control was maintained when the method was adopted as a routine measure by the local authority.
SAP‐TRANSMISSIBLE MOSAIC DISEASES OF SOLANACEOUS CROPS IN TRINIDAD
Authors: DALE W. T. 
Published: February 2008

Four sap‐transmissible viruses were isolated from cultivated Solanaceae in Trinidad: (1) tobacco mosaic virus, from tobacco, tomato and sweet pepper; (2) cucumber mosaic virus, from tobacco and petunia; (3) ‘pepper vein‐banding virus’, probably related to pepper mosaic viruses in Puerto Rico and Brazil, from peppers and tobacco; (4) ‘egg‐plant mosaic virus’, possibly related to the tobacco ring‐spot virus, from egg‐plant and tomato. Pepper vein‐banding virus causes leaf‐crinkling and vein‐banding in Physalis floridana, petunia, various Nicotiana spp. and most peppers; the Large Bell Hot pepper is killed; tomato and egg‐plant are immune. Egg‐plant mosaic virus produces mosaic, ring‐spotting, or both, on different solanaceous species. It also gives local and systemic ring‐spotting on Chenopodium hybridum and necrotic local lesions on the primary leaves of cowpea (var. Black‐eye); cucumber is a symptomless carrier. Only cucumber mosaic virus was found naturally infecting non‐solanaceous hosts, cucumber and certain common wild plants.The thermal inactivation point of pepper vein‐banding virus is 62° C, its dilution end‐point 2×10‐5 and its longevity in vitro 6 day s at 23–30° C.; corresponding values for egg‐plant mosaic virus are 78° C., 10‐6 and over 3 weeks. Aphisgossypii transmits cucumber mosaic and pepper vein‐banding, but not egg‐plant mosaic, of which Epitrix sp. is an occasional vector. Tobacco mosaic, as elsewhere, probably has no regular insect vectors in Trinidad.
STUDIES IN THE MODE OF ACTION OF INSECTICIDES
Authors: HOPF H. S. 
Published: February 2008

Homogenates of the thoracic nervous system of Locusta migratoria migratoriodes are able to hydrolyse acetylcholine (ACh) and o‐nitrophenylacetate (NPA), and this hydrolysis can be inhibited by tetraethylpyrophosphate (TEPP) at approximately the same molar concentration for both substrates. It is possible that one acetyl‐esterase is responsible for the breakdown of the two substances, and there is no reason to assume the existence of a specific acetylcholinesterase. In normal horse serum, on the other hand, the pseudocholinesterase is quite distinct from the enzyme responsible for the breakdown of NPA.In an attempt to correlate the inhibition of the locust nerve cord acetylesterase with toxic activity to insects and mice, four chlorinated diethyl‐phenylphosphates were tested as contact poisons against a number of insects and by injection against locusts and mice, and also as in vitro inhibitors of locust nerve cord acetylesterase and horse‐serum pseudocholinesterase. The chemicals were the 2‐chloro‐, 4‐chloro, 2:4‐dichloro‐ and 2:4:5‐trichloro‐ analogues of diethyl‐phenylphosphate.Good correlation exists between their in vitro activity against the nerve‐cord acetylesterase and their contact activity to aphids, but not between the former and injection toxicity to locusts. No correlation could be established between the inhibition of horse‐serum cholinesterase and injection toxicity to mice. It is thought likely that the inhibition of nerve‐cord acetylesterase is of greater importance in aphids than in other insects, where the toxic action of the phosphoric esters is at least partly concerned with other vital processes, and that a detoxication mechanism in the mammal breaks down some of the phosphoric esters, but not others.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M. 
Published: February 2008

Conditions affecting the production of gliotoxin by a strain of Trichoderma viride, known to produce this antibiotic in synthetic culture media, were studied in two types of soil, a highly acid, sandy podsol from Wareham Heath and a less acid garden soil. High yields of an antibiotic substance, which results from bioassays showed to be similar to gliotoxin, were obtained from both inoculated soils when autoclaved and supplemented with organic material. The autoclaved soils behaved differently when unsupplemented; Wareham soil supported production of the antibiotic but little or none was produced in the garden soil. No antibiotic activity could be demonstrated in soil which had not been inoculated with T. viride.Acidification of unsupplemented garden soil by addition of sulphuric acid had a favourable effect on production of the antibiotic, but raising the pH of Wareham soil by addition of calcium hydroxide also increased the yield. These effects, therefore, cannot be due simply to the change in pH of the soil.The beneficial effect of autoclaving the soil on production of the antibiotic assumed to be gliotoxin was analysed and separated into three distinct effects, elimination of the microflora, increase in availability of nitrogen compounds and increase in available carbon compounds. The last effect was considered to be of greatest significance.The antibiotic was produced in normal Wareham soil if supplemented with additional carbon compounds, but not in garden soil unless this had also been acidified before inoculation. A chromatographic method of bioassay used in the later work gave more substantial evidence that the antibiotic produced in the soil was, in fact, gliotoxin.
THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY
Authors: CROOKE W. M. , HUNTER J. G. , VERGNANO ORNELLA 
Published: February 2008

The influence of varying levels of iron and substrate pH on the uptake of nickel and the intensity of toxicity symptoms in oat plants have been investigated using sand‐and water‐culture techniques.Nickel‐toxicity symptoms (both necrosis and chlorosis) are less severe when the concentration of iron in the nutrient solution is high. The reduction in degree of necrosis is related to a reduced content of nickel in the leaf blades, whilst that of chlorosis is related to the Ni/Fe ratio in the leaf blades—an internal antagonism being indicated in the latter case.A reciprocal relationship exists between the nickel and iron contents of the leaf blades; the nickel content is materially reduced by high concentrations of iron in the nutrient solution, and the iron content by nickel, the former being the more pronounced effect.Uptake of nickel increases with increasing pH for a constant iron level in the substrate, although the degree of necrotic symptoms is similar over pH range 4–7. Iron uptake is reduced by both nickel and increasing pH and results in chlorosis at pH values of 5·5 and above.For a constant level of iron supply the phosphate content of the stem extracts is higher the greater the degree of nickel toxicity; the phosphorus status of the plant may be a factor in producing nickel toxicity but if so, it has to be considered in relation to other factors.