摘要:

Datura tatulais a more suitable host than potato for studying the factors influencing the transmission of potato leaf‐roll virus byMyzus persicae; it is more easily infected, provides a better source of virus for feeding aphids, produces symptoms more quickly and over a longer period of the year.Loughnane's (1943) claim that leaf‐roll virus is transmitted by starved aphids that feed for only 5 min. on infected potato plants was not confirmed. The shortest infection‐feeding time in whichM. persicaeaphids became infective was 2 hr.; such aphids did not infect healthy plants in the first 2 days and, when transferred to a series of healthy plants at intervals, infected only few. The ability to cause infections was increased by increasing the length of infection feeding. Aphids fed for many days on infected plants could infect healthy plants in the first 15 min. of test feeding, and they continued to cause infections for long periods.Aphids became infective more readily when feeding on recently infectedDatura tatula, showing only slight symptoms, than on older plants with pronounced chlorosis; similarly, young potato sprouts showing no symptoms were better sources of virus for aphids than older plants showing severe leaf roll.The differences in severity of symptoms shown by potato plants with leaf roll in the field mainly occur because of differences in virulence of accompanying strains of potato virusX, but isolates of leaf‐roll virus were found that also varied in vi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00894.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The length of the developmental instars ofCalandra oryzaehas been estimated at relative humidities of 50, 60, 70 and 80% at 21° C., at 70% at 18, 25 and 30° C., and at 80% at 18° C., by the dissection daily of samples of infested wheat‐grains. The results are expressed as a median obtained by the method of probit analysis. Comparison of this method, with estimates of median and mean obtained by orthodox arithmetical methods from similar work onRhizopertha, show that the probit method gives good estimates.About 90% of the eggs laid are fertile. Normally only one adult will develop in a grain, all other individuals being destroyed by cannibalism. The sex ratio is unity. It was not possible to crossC. oryzaeandC. granaria.The daily oviposition rate ofC. oryzaeat 17, 21 and 25° C. increases with relative humidity. There is a critical point at about 60%r.h. below which egg laying declines rapidly, and mortality is high. At 100%r.h. the oviposition rates per female per day are approximately 1.3, 2.5 and 3.4 at 17, 21 and 25° C. respectively.In experimental conditions most eggs per grain are obtained by giving isolated females one grain each, but more eggs are laid by females given more than one grain. Daily egg output is reduced by grouping females or including males. In culture, depths of grain up to 7 cm. do not discourage egg

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00895.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The assessment of populations ofAnisopus fenestrate(Scopoli, 1763) in sewage bacteria beds by the trapping of adults at the surface has been previously proved to be unsatisfactory. Methods were therefore developed for determining the numbers of egg masses, larvae and pupae as well as the total organic matter in a unit volume of bed. The relative larval populations of three areas under investigation were related to the loading of the beds as measured by the sewage strength and rate of application. In the upper 2 ft. 6 in. the numbers of larvae and pupae per unit volume of bed decreased with depth. There was no evidence of any vertical migration of the larvae before pupation. The horizontal distribution of larvae was found to be affected by the method of distribution. In beds served with fixed spray jets larvae are more abundant nearer the jets than at some distance away. In beds served with travelling distributors the larvae are more abundant in the zones below the jets than in the drier intermediate zones. In both cases relatively higher percentages of pupae in the drier zones might indicate a horizontal migration of larvae before pupating or of the pupae themselves.The incidence of the larvae throughout 1949 in all three beds showed recurring peaks. In the following year a more intensive investigation on one area showed that this was due to successive generations of the fly; the proximity of the peaks is determined mostly by temperature and their size by the amount of food available in the bed during the larval grazing phase.In the area not treated with insecticide intraspecific competition during a period when food was limiting, due to depletion by the previous generation, resulted in a natural reduction in the population. In the area treated with insecticide the food was retained and this natural control was thereby delayed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00896.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Acetylcholine, choline chloride, acetyl‐β‐methylcholine, benzoylcholine, carbamyl choline, adrenaline andd‐tubocurarine are non‐toxic when injected into the locust. Prostigmine is also non‐toxic, and eserine considerably less toxic to the locust than to man.The toxic effect of tetraethyl pyrophosphate (TEPP) cannot be antagonized by injection of atropine or enhanced byd‐tubocurarine.The injection of acetylcholine chloride following injection of TEPP does not affect subsequent mortality.These findings are discussed, and it is suggested that the physiology of the nervous system of the insect is unlike that of the mammal, neither cholinesters nor adrenaline being concerned in it. Phosphorus insecticides are thought to inhibit a general esterase not specifically connected with

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00897.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The absorption of the systemic insecticide bisdimethylamino fluorophosphine oxide containing32P by plants has been studied, and where possible comparisons have been made with bisdimethylaminophosphonous anhydride.The radio‐oxide is absorbed by the roots of a broad‐bean plant from culture solutions. The level of radioactivity in the plant increases as the solution is absorbed and is higher in the washed roots than in the rest of the plant. The radioactivity of the remaining culture solution decreases as more of it is taken up by the plants showing that the roots selectively absorb the oxide from solution. In this latter respect it differs from the anhydride which is selectively rejected at similar rates of transpiration. The material is absorbed more slowly by plants growing in soil than in sand.An appreciable part of the oxide absorbed by the roots is given off as vapour by the leaves. The transpired material can be collected and shown to be radioactive and systemically insecticidal. Aphids feeding on treated plants contain radioactive material.The oxide is less lipoid soluble than the anhydride and does not penetrate as readily into the leaves of the broad bean. Since it is also lost by vaporization from the plants only small amounts are translocated following leaf applications to beans, cabbages and h

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00898.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00899.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Data are presented showing the effect of degree of refining upon the specific gravity, viscosity, unsulphonatable mineral residue (U.R.), refractive index, average molecular weight, group analysis, sulphur content and phototoxicity of two spindle oil distillates in the boiling range 300–390° C.Cucumber plants proved very suitable for demonstrating differences in phyto‐toxic properties of the oils.Spindle oils refined to a U.R. of 82 or higher, and a specific gravity of 0.885 or lower, showed no phytotoxicity in the tests on these plants. A fair agreement was found between the results of these tests and the specifications laid down by Dr H. Martin for spray

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00900.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

A suitable basic medium for the growth ofBacillus subtilis, particularly in relation to the production of an antibiotic inhibitory toFusarium udum, is described. Organic nitrogen with carbohydrate and K2HPO4is shown to be essential for the growth ofBacillus subtilis.Magnesium sulphate, manganese and iron are found to increase the production of the antibiotic. Effects of temperature, period of incubation, aeration, etc., on the production of the inhibitory substance are described. The active principle is adsorbed by soil and to a lesser degree by kaolin. The organic matter and the soluble salts in the soil do not appear to play an important role in the loss of activity of the filtrates during passage through a bed of soil.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

The activity ofPlasmodiophora brassicaeWor. in the soil was measured simultaneously by counts of root‐hair infection on cabbage seedlings and percentage clubbing of older plants. A linear relation was found between the logarithms of the mean number of root‐hair infections per seedling and the logarithms of the spore concentration in the inoculum. It was found that a high proportion of clubbed plants could be associated with very low average numbers of root‐hair infections on seedlings. The percentage of clubbed plants can be used for assessing quantitatively the infestation of soil byP. brassicaebut only at lower levels of infestation than can counts of root‐hair infections. An effect of early application and higher levels of nutrients in increasing clubroot indicates that the nutrient status of the soil is also important, but it is not clear whether this is due to increased club growth or to a direct effect on the fungus.Experiments on the survival of resting spores showed that, in a wet acid soil, there was a rapid decline in numbers of infections to a low and nearly constant level with increasing time from inoculation. This decline could be considerably delayed by alkaline or dry soil conditions or by the addition to the soil of mustard oil (allyl isothiocyanate). This fall in activity is ascribed to spontaneous germination of resting spores, germination being prevented or delayed by such conditions as alkalinity, low soil moisture or the presence of inhibitors.In an attempt to cause biological stimulation of resting‐spore germination by growing short‐term catch crops in infested soil (re‐infestation of the soil from diseased crucifers being prevented), there were fewer infections on test cabbage seedlings after crucifers or ryegrass had been grown than after a number of other non‐crucifers. In fallow soil, a similar reduction was, however, caused by adding nutrients alone.It was confirmed thatP. brassicaecan infect the root hairs of a number of non‐crucifers and form zoosporangia and zoospores, but no other stages of the fungus have been seen in those plants.Possible improvement of the sampling design in experiments using the root‐hair infection‐count method

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00903.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY