bluuebunny/crossref_metadata_2025 huggingface dataset:
THE CONTROL OF MANGOLD FLY (PEGOMYIA BETAE CURTIS) WITH DDT AND OTHER CHLORINATED HYDROCARBONS
Authors: JONES F. G. W. , DUNNING R. A.
Published: February 2008

Laboratory and field trials were carried out in the period 1948–52 with DDT, BHC, and other chlorinated hydrocarbon insecticides and with parathion for the control of mangold‐fly larvae (Pegomyia betae Curtis) mining in the leaves of sugar beet. Kills ranging from 85 to 99% were obtained within 6 days with ‘high’‐ and ‘ low‐volume’ sprays using 6–24 oz. of DDT per acre in the form of an oil emulsion applied as a top cover only. Formulation in oil improved the action of the DDT, it being necessary to use dusts and wettable powders at excessive rates to obtain equivalent kills. DDT was usually superior to BHC when compared at customary rates of application for both insecticides. When oil emulsions were compared side by side, however, as ‘low‐volume’ sprays, DDT was not significantly better than BHC. In the same trial, toxaphene, aldrin and dieldrin also gave kills of the same order as BHC and DDT. With the possible exception of parathion, none of the insecticides used appeared to have any effect upon eggs.

Plot yields of two of the trials were determined in the autumn, but only at one trial was there a significant increase in yield on the treated plots. At this trial the mangold‐fly infestation was severe, there being twenty‐five unhatched eggs and twenty larvae per plant at the time of treatment. Attempts were made to assess the degree of defoliation and to relate it to the larval population and to the effect on yield.

Commercial insecticides of the ‘stock emulsion’ and ‘miscible oil’ types occasionally caused phytotoxicity when applied to sugar beet at excessive, ‘high‐volume’ rates and concentrations. More serious phytotoxicity was observed in tests of commercial insecticides used at ‘low‐volume’ rates and concentrations. Out of ten products tested, only three were acceptable over the whole range of rates and concentrations employed, whilst four caused injury over the whole range.

The results obtained in the field and the laboratory were in agreement but did not always agree with the findings of other workers. BHC has previously been recommended largely on the basis of experiments on larvae mining very small beet plants when in, or just beyond, the cotyledon stage. All the trials by the authors were on sugar‐beet seedlings with about six foliage leaves and normal in size for the time of the year. On these plants BHC proved ineffective both as dust and ‘high‐volume’ spray when used at customary rates, but was effective as a ‘low‐volume’ spray in oil emulsion.

The successful control of mining larvae by DDT and other chlorinated hydrocarbons is probably due to penetration of the leaf tissue by the insecticide.
THE DISTRIBUTION OF VIRUSES IN DIFFERENT LEAF TISSUES AND ITS INFLUENCE ON VIRUS TRANSMISSION BY APHIDS
Authors: BAWDEN F. C. , HAMLYN BRENDA M. G. , WATSON MARION A.
Published: February 2008

Exposing both surfaces of leaves systemically infected with cabbage black ring spot virus (CBRSV) or henbane mosaic virus to ultra‐violet radiation decreases the infectivity of expressed sap to about one‐fifth. As irradiation probably inactivates virus mainly in the epidermis, which occupies about one‐quarter the volume of the leaves, these viruses seem to occur at much higher concentrations in sap from the epidermis than in sap from other cells. By contrast, tobacco mosaic virus seems not to occur predominantly in the epidermis.

CBRSV and henbane mosaic virus are normally transmitted most frequently by previously fasted aphids that feed for only short periods on infected leaves, but aphids treated like this transmit rarely from leaves that have been exposed to ultraviolet radiation. Irradiation has relatively little effect on the proportion of aphids that transmit after long infection feedings. Fasting seems to increase transmission by increasing the probability that aphids will imbibe sap from the epidermis of leaves they newly colonize. With longer periods on infected leaves, the ability of fasted aphids to transmit probably decreases because they then feed from deeper cells and their stylets contain sap with less virus. Only virus contained in the stylets seems to be transmitted, not virus taken into the stomach. About half the transmissions of henbane mosaic virus by aphids that have colonized tobacco leaves for hours may be caused by insects that temporarily cease feeding on the phloem and newly penetrate the epidermis.

Irradiating infected leaves affected the transmission of sugar‐beet mosaic virus in the same way as that of henbane mosaic virus, but had little effect on the transmission of beet yellows virus, whose vectors become more likely to transmit the longer they feed on infected plants.
STUDIES OF THE TOXICITY TO WORKER HONEY‐BEES (APIS MELLIFERA L.) OF CERTAIN CHEMICALS USED IN PLANT PROTECTION
Authors: JONES G. D. GLYNNE , CONNELL JOAN U.
Published: February 2008

Laboratory techniques are described for the estimation of the stomach poison, direct and residual film contact poison and fumigant poison effects of chemicals to adult worker honey‐bees.

The toxicity of eleven chemicals used in plant protection has been investigated by these methods. The order of effectiveness as stomach and contact poisons was: parathion, TEPP, γ‐BHC, dieldrin, aldrin, chlordane, o, o‐diethyl‐o‐ethylmercaptoethyl thiophosphate (constituent of Systox), bisdimethylamino fluorophosphine oxide, toxaphene and the sodium salts of 2:4‐D and MCPA: as residual films, dieldrin, aldrin, γ‐BHC, parathion, chlordane, and o, o‐diethyl‐o‐ethylmercapto‐ethyl thiophosphate (constituent of Systox); toxaphene, TEPP and bisdimethylamino fluorophosphine oxide had no measurable effect; as fumigants, dieldrin, γ‐BHC, aldrin, parathion, and chlordane; the remainder had no measurable effect.
BIOLOGICAL TECHNIQUES FOR THE EVALUATION OF FUNGICIDES
Authors: COLHOUN JOHN
Published: February 2008

The effectiveness of fungicides for the control of Plasmodtophora brassicae Woron. in pot tests under controlled conditions is influenced by spore load, duration of storage of spores prior to inoculation, time of year and temperature. Many fungicides are less effective in soil which has been heavily treated with calcium hydroxide than in unlimed soil or in soil treated with calcium carbonate. In general, fungicides are less efficient when very heavy attacks of the disease occur. If experiments are made under comparable conditions consistent conclusions can be obtained.

A schedule of testing is recommended, and it is suggested that fungicides found to be satisfactory in a preliminary test should be subjected to a detailed test. The proposed method of evaluation of a fungicide is to compare its efficacy with that of a standard treatment under comparable conditions. For comparative purposes the efficiency of a fungicide is measured by the percentage number of diseased plants occurring in treated soil and also by the disease index.
A STUDY OF THE EFFECT OF MILDEW INFECTION ON THE REACTION OF WHEAT VARIETIES TO BROWN RUST
Authors: MANNERS J. G. , GANDY DOREEN G.
Published: February 2008

The effect of the presence of Erysiphe graminis tritici on the reactions of each of five wheats, Malakoff, Democrat, Mediterranean, Hussar and Webster, to Puccinia triticina was studied. Under normal environmental conditions, mildew increased the susceptibility to rust of Malakoff and Democrat, though not, except in isolated instances, that of Mediterranean or Hussar. High light intensities enhanced the effect of mildew on the reaction of Democrat to P. triticina. The susceptibility of Webster to rust was unaffected or decreased by the presence of mildew.

In all varieties there was a decided tendency for rust and mildew to develop on different parts of the leaf, and when a leaf was heavily mildewed the development of P. triticina was sometimes almost entirely inhibited. The reason for this is obscure, since spores of P. triticina and E. g. tritici germinate well in each others presence, and cytological studies revealed several cases of the presence of both mildew and rust haustoria in a single living host cell. Anatomical investigations also showed that the effect of mildew on rust infection was confined to rust pustules within 1 mm. of mildew colonies.

The results obtained are in accordance with Gassner's theory that susceptibility to rust is due to the presence of certain specific proteins in the host leaf.
EFFECT OF TETRACHLORONITROBENZENE ON THE SPROUTING AND CROPPING OF POTATO TUBERS
Authors: BROWN W. , REAVILL MARY J.
Published: February 2008

Potato tubers dusted with a preparation containing 3% tetrachloronitrobenzene (TCNB) and kept in a nearly closed container in the laboratory showed reduced sprouting. The reduction was greater the lower the temperature and the earlier the application of the dust; it was less marked with tubers lying on a moist substratum. After long exposure, and especially at higher temperatures, sprouts of treated tubers tended to show a ‘witch's‐broom’ appearance. The repressive effect of TCNB on growth rate disappeared as soon as the tubers were brought into ordinary air. To a certain extent the action of TCNB was antagonized by treatment of the tubers with ethylene chlorhydrin.

Replicated field experiments over three seasons, with four potato varieties, gave a measure of the check to bulking of the crop which is brought about by winter storage of seed tubers in presence of TCNB. This check was eliminated by airing the tubers before planting, the time necessary for this depending on conditions. An airing period of about 6 weeks, in an unheated greenhouse (apart from sun‐ heat) was found to be sufficient for this purpose.

The speed of emergence of the variously treated batches was closely correlated with the yields produced, especially in the earlier liftings.

The average number of shoots per plant was significantly increased by the dust treatment and this was reflected in a higher seed/ware ratio in the mature or late‐lifted crop.

There was no evidence that the delay in sprouting brought about by TCNB was due to an effect on the respiration rate of the dormant tubers.

The concentration of active principle was materially diminished in treated clamps after the period (c. 5 months) of winter storage. Estimates were also made of the persistence of TCNB on exposed surfaces in still and in moving air.
FIELD STUDIES ON THE INFLUENCE OF WEATHER ON EGG‐LAYING BY THE CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE BCHÉ. II
Authors: MILES MARY
Published: February 2008

Observations on the intensity and duration of egg‐laying by Erioischia brassicae Bché were continued in 1953 on the same site as in 1952. Eggs were first observed on 31 April and the spring peak period of egg‐laying lasted from 3 to 30 May with a daily average of 40 eggs/plant. The mean total in spring 1953 was 1287 eggs/plant. Summer peaks occurred on 1–20 July (average 17 eggs/day/plant) and 5–11 August (average 21 eggs/day/plant).

In the field the threshold of reproduction was approximately 60° F. The rate of egg‐laying was highest at 65–70° F. and it declined during prolonged periods of higher temperatures.

The annual cycle of generations, as shown by egg counts and confirmed by the examination of puparia, consisted of two generations and a partial third. The spring generation developed without a prolonged diapause, and there was complete emergence during the summer. The overwintering puparia came from the second and third generations of larvae.
ON THE HOST RANGE AND SYSTEMATIC POSITION OF THE BACTERIA RESPONSIBLE FOR THE YELLOW SLIME DISEASES OF WHEAT (TRITICUM VULGARE VILL.) AND COCKSFOOT GRASS (DACTYLIS GLOMERATA L.)
Authors: SABET K. A.
Published: February 2008

Inoculations with Corynebacterium rathayi (E. F. Sm.) Dowson, alone or combined with the eelworm Anguina tritici into the leaves and shoots of cocksfoot grass (Dactylis glomerata L.) and wheat (Triticum vulgare Vill.), fail to cause infection. Inoculations made through the soil with Corynebactmim rathuyi and C. tritici (Hutchinson) Burkh. plua Anguina tritici cause infection in wheat but not in cocksfoot grass. The symptoms produced on wheat resemble those of yellow slime disease of cocksfoot grass. Successful infection of wheat with Corynebacterium rathay. or C. tritici is dependent on the presence, in the soil surrounding the plants, of Anguina tritici together with one of these bacterial species, which are considered to be so closely related as to suggest that Corynebacterium tritici is but a geographical variety of C. rathayi.
ANALYSIS OF VIRUS LOCAL LESION EXPERIMENTS
Authors: FRY P. R. , TAYLOR W. B.
Published: February 2008

Calculations based on variation of lesion counts about means within the range 7 to 260 per half‐leaf show that the standard deviation may be rendered independent of the mean by a transformation log (x+12) for half‐leaf experiments in bean, tobacco and Nicotiana glutinosa and log (x+21) for whole‐leaf experiments in bean.

Half‐leaf experiment designs are superior to those using whole‐leaves.

Balanced Incomplete Block designs are more efficient than Randomized Blocks or comparisons using a common standard.

The use of covariance to remove the effect of leaf susceptibility gives increased accuracy over the treatment‐standard comparison if used with designs allowing removal of both plant variation and that due to leaf age.
FURTHER STUDIES ON THE BREAKDOWN OF 2:4‐DICHLOROPHENOXYACETIC ACID BY A SOIL BACTERIUM
Authors: AUDUS L. J. , SYMONDS K. V.
Published: February 2008

Bacterial growth rates and the kinetics of detoxication have been followed during the course of breakdown of 2:4‐dichlorophenoxyacetic acid in a liquid mineral salt medium by cultures of Bacterium globiforme isolated from garden soil. It was found that toxicity persisted apparently unchanged long after bacterial growth had ceased, and finally disappeared suddenly after a lag period comparable in duration with those obtained in soil perfusion experiments. These results can best be explained by the production of highly phytotoxic intermediates in the first stages of 2:4‐D breakdown. Preliminary experiments involving paper partition chromatography indicate that there may be at least two such intermediates.
THE HATCHING RESPONSES OF SOME ROOT EELWORMS OF THE GENUS HETERODERA
Authors: WINSLOW R. D.
Published: February 2008

An account is given of investigations on the hatching responses, under laboratory conditions, of nine species or varieties of Heterodera, namely, the beet, cabbage, clover, Galeopsis, carrot, hop, potato, oat and pea eelworms. In the first seven of these, marked differences occurred in hatching responses from cysts incubated in root leachings from various plants, these differences being virtually diagnostic for the eelworm species concerned. In general, good responses to leachings from host plants occurred, whereas there was little or no response in non‐host leachings; but cases of response to non‐hosts and of failure to respond to hosts were encountered. Promising results were obtained in the analysis, by bio‐assay, of mixtures of some of these eelworm species. No appreciable response occurred from cysts of oat and pea eelworms incubated in host leachings, but there was some evidence that such a response did occur from pea eelworm cysts under field conditions. Curves for rate of hatching of seven species and for hatching in diluted leachings in five species were found to be of the form described by Fenwick for potato eelworm. Results are given of some experiments on the effect of age of plant on potency of the root leachings, and on the loss of potency during storage.
SOME EFFECTS OF ULTRA‐VIOLET RADIATION ON LEAVES OF FRENCH BEAN (PHASEOLUS VULGARIS L.)
Authors: BENDA G. T. A.
Published: February 2008

Exposing the primary leaves of French bean to ultra‐violet light produces a variety of effects, their magnitude depending on the extent of the exposure and the subsequent treatment of the leaves. Effects include some that are externally obvious, such as glazing and bronzing; others are detectable by changes in susceptibility to virus infection, by increased sensitivity to damage by ultra‐violet, and by an increased tendency for cells to collapse when the leaves are kept in darkness. Some of the effects can be counteracted by exposing leaves to visible light. Effects of radiation are not confined to epidermal cells, and measurements with detached epidermis indicate that from a quarter to a half of incident radiation of wave‐length 2536 A. may be transmitted by the epidermis.
INVESTIGATION OF CHRYSANTHEMUM VIRUSES 1. ASPERMY FLOWER DISTORTION
Authors: HOLLINGS M.
Published: February 2008

Tomato aspermy virus alone distorted some chrysanthemum flowers, and aggravated symptoms produced by other chrysanthemum viruses. First‐season infection affected only a proportion of the blooms; in subsequent seasons nearly all flowers showed symptoms with increased severity.
SOME PROPERTIES OF FOUR VIRUSES ISOLATED FROM CARNATION PLANTS
Authors: KASSANIS B.
Published: February 2008

Four viruses isolated from commercial carnation varieties were transmitted to Sweet William plants (Dianthus barbatus L.), which react characteristically with them. Two, carnation ring‐spot virus and carnation mottle virus, have spherical particles, the first about 19 nift and the second about 32 mμ in diameter. Both survive heating for 10 min. at 85o but not at 90 ° C, and remain active at room temperature in sap from Sweet William for more than 2 weeks. They are not serologically related, and have not been transmitted by Myzus persicae.
THE RESPIRATION OF TOBACCO LEAVES IN THE 20‐HOUR PERIOD FOLLOWING INOCULATION WITH TOBACCO MOSAIC VIRUS
Authors: OWEN P. C.
Published: February 2008

The effect of infection with tobacco mosaic virus on the respiration rates of detached tobacco leaves in the period immediately after inoculation differed in plants grown at different times of the year. During winter, infection increased respiration rates, and in summer decreased them. In winter‐grown plants, increasing the light intensity during the period before inoculation decreased respiration rates after infection. Extending the day length for winter‐grown plants did not alter the effect of infection on respiration. Respiration rates began to change in less than 1 hr. after inoculation and are unlikely to be associated with the formation of new virus.
ESTERASE INHIBITION BY ORGANO‐PHOSPHORUS RESIDUES, WITH SOME OBSERVATIONS ON POSSIBLE EFFECTS ON PLANT METABOLISM
Authors: LORD K. A.
Published: February 2008

Organo‐phosphorus residues in tissues of sprayed plants were detected by estimating the esterase‐inhibiting activity of their leaf and root extracts. This method was used to examine the anti‐esterase effects of mangold plants that had been sprayed with Systox, parathion and Hanane. Extracts of leaves of these treated plants were shown to inhibit added choline esterase for some weeks after treatment. The enzymic hydrolysis of phenyl acetate by extracts of leaves and roots of mangold plants treated with these insecticides was reduced for varying periods of up to 8 weeks.

Assays of parts of bean plants that had been sprayed with demeton‐S showed that anti‐esterase activity was limited to those parts that had been sprayed: tissues developed subsequent to spraying showed no such effects. Leaves sprayed about z months previously inhibited added choline esterase and showed reduced activity in hydrolysing phenyl acetate. There is some evidence that substances, possibly substrates in the plant enzyme systems affected, accumulate in treated leaves.
CHEMICAL STRUCTURE AND NARCOTIC POTENCY TO GRAIN WEEVILS. ALCOHOLS AND METHYL ESTERS OF FATTY ACIDS
Authors: BRADBURY F. R. , ARMSTRONG G.
Published: February 2008

The narcotic and toxic potencies of the first seven homologous alcohols and the methyl esters of the first seven homologous fatty acids have been determined using grain weevils (Calandra granaria). The experiments were designed as balanced incomplete blocks, and Finney's probit plane technique was applied to the results. In both series of compounds the narcotic and toxic potencies expressed in thermodynamic concentrations decreased with increasing number of carbon atoms. The margin between narcotic dose and toxic dose is greater in the alcohol series than in the ester series. The methyl esters of the fatty acids showed a stepwise descent in biological potency, the odd numbered series being more active than the even series. The penetration of these compounds into grain weevils and their biological action are discussed in relation to the coefficients of response to log concentration and log time of exposure.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Authors: FAWCETT C. H. , WAIN R. L. , WIGHTMAN F.
Published: February 2008

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 postulated by other workers.
THE INCIDENCE AND CONTROL OF CAULIFLOWER MOSAIC IN BROCCOLI IN SOUTH‐WEST ENGLAND
Authors: JENKINSON J. G.
Published: February 2008

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 they cause.
THE EMERGENCE OF LARVAE OF HETERODERA ROSTOCHIENSIS UNDER CONDITIONS OF CONSTANT AND OF ALTERNATING TEMPERATURE
Authors: BISHOP DAPHNE
Published: February 2008

A description is given of the effect of alternation of temperature on the emergence of larvae from cysts of the potato‐root eelworm. Both potato‐root diffusate and anhydrotetronic acid have been used as hatching stimulants. When the temperature is alternated between 25 and 150 C. there is a significant increase in the number of larvae emerging. The effects of using pre‐warmed as opposed to cold diffusate on cysts of different ages and of renewing the difrusate twice a week instead of once a week are also examined. A maximum has been found in the response‐concentration curve when cysts are stimulated by anhydrotetronic acid.
THE CONTROL OF FUSARIUM BLIGHT IN OAT SEEDLINGS WITH ANTAGONISTIC SPECIES OF CHAETOMIUM
Authors: TVEIT M. , WOOD R. K. S.
Published: February 2008

Forty‐seven isolates representing twenty‐seven species of Chaetomium were tested for their ability to control seedling blight of oat seedlings caused by Fusarium spp., chiefly F. nivale (Fr.) Ces. In pot tests the majority of the isolates were ineffective, but certain isolates of Chaetomium cochliodes Pall, and C. globosum Kunze gave a large measure of control and were as effective as an organic mercury seed dressing. Control of disease was also obtained when living material was attached to the surface of oat seed and when infested seed was soaked in cell‐free filtrates from cultures of isolates which reduced disease in vivo.

Substantial control of disease was obtained when infested seed was sown in soil to which cultures of C. cochliodes had been added 10 months previously. This antagonist was able to grow through unsterile soil in the presence of certain added substrates.

The results of pot experiments were confirmed in field experiments.

Isolates of Chaetomium which controlled disease in pot and field experiments were not strikingly antagonistic to Fusariirm nivale in pure culture on agar media.
INVESTIGATIONS ON FUNGICIDES. I. FUNGICIDAL AND SYSTEMIC FUNGICIDAL ACTIVITY IN CERTAIN ARYLOXYALKANECARBOXYLIC ACIDS
Authors: FAWCETT C. H. , SPENCER D. M. , WAIN R. L.
Published: February 2008

Fifty‐four aryloxyalkanecarboxylic acids have been examined as systemic fungicides. Of these, four which produced negligible damage in broad‐bean seedlings yet conferred systemic fungicidal protection to broad beans against Botrytis fabae and to tomatoes against Alternaria solanixvere studied in detail. The direct fungicidal activity of twenty compounds was assessed against B. fabae and Pythium ultimum. No correlation between fungicidal and systemic fungicidal action toward B. fabae was established. Other possibilities regarding their mode of action as systemic fungicides are discussed. The systemic fungicidal activity of a‐phenoxyziobutyric and 2:4:6‐trichlorophenoxyacetic acids in beans and of the latter compound in tomato plants was found to depend upon seasonal factors, but for 3‐phenoxybutyric and 5‐phenoxycaproic acids such variation was not observed. Results obtained in the bean test by two methods of assessment were found to correlate. The potato petiole test (van Raalte) for assessing systemic fungicidal activity was studied and modified. Evidence was obtained that the results might be unreliable owing to toxic effects produced by the compounds on the petiole tissue. Attempts were made to avoid this complication, but when phytotoxicity was eliminated, little fungicidal activity was shown.
THE ABSORPTION, BREAKDOWN AND SYSTEMIC BEHAVIOUR IN PLANTS OF 32P‐LABELLED DEMETON‐S
Authors: THOMAS W. D. E. , BENNETT S. H. , LLOYD‐JONES C. P.
Published: February 2008

Investigations are described on the general behaviour of diethyl‐5‐(a‐ethylthioethyl) phosphorothiolate (demeton‐S) labelled with 32P, after leaf application to beans, apples and Coleus; and to the roots of beans growing in soil or sand.

Following leaf application, three processes, evaporation, breakdown into toxic non‐volatile compounds, and absorption, occurred concurrently and effectively removed unchanged demeton‐S from the leaf surface within a few hours. The evaporation gave rise to a fumigant action on Aphis fubue. Both demeton‐S and its degradation products were absorbed, the former degrading rapidly within the tissue untreated foliage. In no instance following leaf application could any unchanged demeton‐S be found elsewhere in the plant. Analyses showed a higher proportion of primary toxic degradation products in the treated than in the untreated leaves.

Translocation from treated leaves was never sufficient to kill aphids feeding on the Following root application to beans in soil or sand, aphids feeding on the shoot tips were killed after z days; unchanged demeton‐S was translocated following root application.

Demeton‐S and its toxic derivatives appeared to move much more freely in xylem than in phloem tissue; movement from xylem to phloem must occur, but subsequent transport within the latter tissue is limited.

Autoradiographic evidence confirmed the limited extent of movement within leaves.
FEEDING HABITS OF THE COTTON WHITEFLY, BEMISIA TAB AC I GENN. (HOMOPTERA: ALEYRODIDAE)
Authors: POLLARD D. G.
Published: February 2008

The cotton whitefly, Bemisia tabaci Genn., is important in the Sudan first as the vector of leaf‐curl virus, and secondly because it, principally when immature, directly damages plants. It damages both leaf‐curl‐resistant and susceptible varieties, and during recent years the increase in DDT spraying against the cotton jassid has increased the numbers and importance of the cotton whitefly.

The macroscopic effects of the nymphs on the leaves include: (I) ‘asal’ (honeydew), often produced in quantities sufficient to cover the leaves and contaminate the lint in open bolls; (2) chlorotic spots caused by the saliva of feeding nymphs removing chlorophyll and starch; (3) development of anthocyanin; (4) leaf shedding and a reduced growth rate.

The stylets of nymphs on the lower leaf surface can reach the phloem, except when they follow a convoluted path. The stylets usually penetrate between the epidermal cells. Penetration through the parenchyma is predominantly intercellular, and the objective is the phloem. Stylets terminated in the phloem in 82% of examples examined, with the remainder ending in the parenchyma. Only one case of partial penetration of the xylem occurred. A stylet, or salivary, sheath is rare; it is a delicate structure with an annular construction. Stylet tracks occur rarely and indicate probing in the region of the phloem.

Damage to the tissues is limited to slow chloroplast destruction and occasional plasmolysis; the phloem is neither blocked nor obviously damaged.
THE EFFECT OF INFECTION WITH TOBACCO MOSAIC VIRUS ON THE RESPIRATION OF TOBACCO LEAVES OF VARYING AGES IN THE PERIOD BETWEEN INOCULATION AND SYSTEMIC INFECTION
Authors: OWEN P. C.
Published: February 2008

Leaves of tobacco plants inoculated with tobacco mosaic virus were divided into three groups: (a) inoculated leaves; (b) younger non‐inoculated leaves present at the time of inoculation; (c) leaves formed since inoculation. The respiration rate of each group was compared with that of similar leaves from healthy plants. The respiration rate of inoculated leaves was increased by a constant amount for 3 weeks after inoculation, when it decreased. The respiration rate of group (b) leaves was not affected at any time, and that of group (c) leaves was decreased by 10% when they showed symptoms. The increased respiration in the inoculated leaves occurred too soon to reflect virus formation, and it is suggested that it reflects an initial change in infected cells preparatory to virus synthesis. The subsequent decrease in respiration may be due to the accumulation of virus which does not contribute to the total leaf respiration.
THE EFFECT OF DARKENING ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION WITH VIRUSES
Authors: WILTSHIRE G. H.
Published: February 2008

The susceptibility of French bean plants to infection by the Rothamsted strain of tobacco necrosis virus as measured by the local‐lesion method is increased by a rise in temperature and usually by darkening the plant before inoculation. If part only of a leaf is darkened, that part becomes more susceptible. Plants in full light also become more susceptible if carbon dioxide is removed from the air, whereas the susceptibility of plants in the dark is not altered.

Darkening leaves decreases their content of malic, fumaric, succinic and glycolic acids and increases the content of citric acid; the content of oxalic and malonic acids remains constant. These changes occurred in winter and summer and whether or not darkening increased susceptibility.

The effect on susceptibility of individual acids infiltrated into the leaf was measured in leaves kept in the light or in the dark before inoculation. None of the acids used produced any large change in susceptibility.
THE CONTROL OF POTATO VIRUS DISEASES BY INSECTICIDES
Authors: BROADBENT L. , BURT P. E. , HEATHCOTE G. D.
Published: February 2008

Replicated trials were carried out in the years 1950, 1951, 1953 and 1954 to see if the spread of leaf‐roll virus and virus Y in potato crops could be reduced by applying insecticides. The crops were disease‐free, except for small numbers of deliberately introduced infected plants, and were sprayed at intervals of 10 or 14 days, according to the stage of growth of the plants, with a tractor‐mounted spraying machine at 1OO gal./acre/application. Disease spread was estimated by growing tubers taken from the five plants on either side of each infector. DDT emulsion, DDT suspension, endrin, schradan, mipafox, malathion, parathion and Systox prevented the spread of leaf‐roll virus and decreased the spread of virus Y, although DDT emulsion was the only insecticide used in all the trials. Dieldrin and toxaphene were ineffective. When virus control was successful, aphid control (estimated by counting apterae in the crops) was good.
ON THE CONTROL OF POTATO‐ROOT EELWORM (HETERODERA ROSTOCHIENSIS WOLLENW.) BY CHLORINATED PHENOL AND p‐m‐ CRESOL IN SOLUBILIZED FORM*
Authors: STONE L. E. W.
Published: February 2008

Solubilized phenols and cresols, applied at the rate of 1s gal./sq.yd. at 5% strength on light sandy loam, have killed up to approximately half the population of potato‐root eelworm in the top 8 in of soil. When nematicide distribution was aided by rotavation on the same site, yields were approximately doubled compared with untreated areas. The eelworm population in the soil also increased, but not so much as that where no treatment had been applied.

Under cold glasshouse conditions on light loam, high‐volume methods have greatly increased the yield of tomatoes compared with untreated plots, but the soil population of potato eelworm has also risen. 20 gal. to the square yard of 0·5%p‐m‐ cresol is better than 10 gal. of 1% by both criteria.

There is evidence of a slow kill of cyst contents in soil samples stored in the laboratory.

The high‐volume type of soil drench is shown to be highly effective under laboratory conditions. The importance of the initial water content of the soil is demonstrated. The superiority of the 20 gal. treatment over the 10 gal. one is confirmed.

Investigations on kill in depth by very large applications of dilute nematicide in the same cold glasshouse have demonstrated the part played by the rate at which the material is applied. The degree of kill in the 6–12 in. soil layer is still inadequate.

The practical applications of this type of nematicide are briefly discussed.
THE EFFECT OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND MORTALITY OF TRIBOLIUM CASTANEUM (HERBST) (COLEOPTERA, TENEBRIONIDAE)
Authors: HOWE R. W.
Published: February 2008

The speed of development and the developmental mortality of Tribolium castaneum were studied over a series of temperatures between 15 and 40°C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.

Eggs did not hatch at any humidity at 17·5°C. or less, nor at 10% R.H. at 40°C. At all other conditions about 80% of eggs hatched. Humidity does not affect the duration of the egg period. The effect of temperature on the egg period is shown graphically, the shortest period occurring at 37·5°C.

Larvae fail to develop into normal adults at 20°C. and also fail at 90 and 30% R.H. at 40°C. At 20°C. and 70% R.H. pupae may be formed but they do not become normal adults. The rate of larval development is affected by both temperature and humidity. Development is quickest at the highest humidity used at any temperature and at 35°C. for each humidity. Larval mortality is less than 20% except at 40°C. and at combinations of low humidity and low temperature. The results correspond with published results using similar foodstuffs.

Groundnuts were used as a food in a series of experiments at 30°C. and another series at 70% R.H. Larvae on this food were much more susceptible to the effects of humidity and were unable to develop at 20 or 40°C. at 70% R.H. In all conditions development was slower and mortality higher than on wheatfeed.

The pupal period is not affected by humidity and is shortest at 37·5°C.

The conditions in which Park found that cultures of T. castaneum became extinct, 24°C. and 30% R.H., lie inside the zone in which development is possible. The possible causes for this discrepancy are discussed.
THE VALUE OF GLASSHOUSE TESTS WITH SEEDLINGS IN SELECTING PLANTS TOLERANT TO BEET YELLOWS VIRUS
Authors: WATSON MARION A. , RUSSELL G. E.
Published: February 2008

Commercial strains of sugar beet, and breeders' lines of Beta vulgaris and B. vulgaris subsp. maritima, were exposed to infection with SBY and SBYN strains of beet yellows virus, using varying numbers of Myzus persicae as vectors, so as to cause a wide range of symptoms. The severity of the symptoms was assessed by scoring for superficial veinal necrosis (‘etch’). All varieties of sugar beet tested were susceptible to infection, but the severity of the symptoms varied, particularly between the cultivated and wild beet types.

The scores for severity of symptoms made in the glasshouse were positively correlated with similar scores made in a field experiment using two cultivated and two wild beet types. The symptom scores were also positively correlated with losses in root and sugar yields caused by the virus.
SEEDLING BLIGHT OF SUGAR‐CANE‐A NEW DISEASE CAUSED BY HELMINTHOSPORIUM SACCHARI BUTLER
Authors: LOVELESS A. R. , SMITH C. E. M.
Published: February 2008

The fungus Helminthosporium sacchari Butler, known to be the cause of eye spot, a common air‐borne disease of sugar‐cane leaves, is now shown to be the cause of an undescribed seed‐borne disease of sugar‐cane seedlings. It is therefore suggested that the disease should be renamed eye spot and seedling blight of sugarcane.

The symptoms of seedling blight are described, and the pathogenicity of the fungus to sugar‐cane seedlings is confirmed. Incidence of seedling blight is shown to be markedly affected by the growing conditions, and disease‐escape is common. The two most important factors predisposing seedlings to attack appear to be (i) the relative humidity of the atmosphere, and (ii) the occurrence of a check to the continuous growth of the seedlings.

With the discovery of the existence of seedling blight, eye spot assumes a particular significance in plant‐breeding plots, because it may be responsible for the loss of sugar‐cane seedlings, any one of which is potentially a desirable new variety.
THE CONTROL OF LOOSE SMUT IN WHEAT AND BARLEY
Authors: BATTS C. C. V.
Published: February 2008

Loose smut (Ustilago nuda) has become increasingly troublesome in some widely grown wheat and barley varieties in recent years. The usual control of the disease is hot water treatment of the grain, and experiments have been carried out to find the most satisfactory treatment. Variations in times and temperatures for each stage of the treatment were made.

In preliminary small‐scale experiments, the moisture content of the grain after different periods of soaking in water was determined, together with the effects on such grain of subsequent treatment at increasing temperatures. Wheat was able to withstand higher temperatures than barley.

After presoaking in cold water for 4 hr. a draining period of 3 hr. helped considerably in controlling the disease. After a warm presoak (c. 90° F.) for 4 hr. the long drain was not necessary. The temperature of the grain in the hot tank must rise as rapidly as possible. Following the presoaking periods, 10 min. in the hot tank at 127–129° F. for wheat and 124–126° F. for barley were found to give control. Single tank treatments, e.g. 4 hr. at 113° F., also gave control.

In general, the higher the temperature at any stage of the treatment, the greater the reduction in germination. The reduction in vigour was reflected in the percentage germination after j days.

When sown, the plants from hot‐water‐treated seed were a few days later in appearing above ground compared with plants from untreated seed. After a week or two, however, no differences were visible. The tiller populations after earing were not closely related to the original germination percentage of the seed; plots which were thin in the early stages often tillered well.

The effects of soaking in chloranil (Spergon) suspensions and in water alone was also investigated, the recommendations of Tyner being followed. No control was achieved in wheat by either treatment, but for barley both treatments gave control, but sometimes with serious reduction in germination.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Authors: TOOTHILL JOYCE , WAIN R. L. , WIGHTMAN F.
Published: February 2008

A study has been made of the growth‐regulating activity of a number of phenoxy acids possessing halogen or methyl substituents in the 2:6‐ or 33‐ positions of the nucleus. The pea curvature, Avena cylinder elongation and tomato‐leaf epinasty tests have been used for assessing biological activity. The results show that in general 3:s‐ is more closely associated with inactivity than 2:6‐ substitution. The introduction of a further halogen atom into the 4‐ position does not enhance activity in the 2:6‐ compounds but does so in the 3:s‐ derivatives. Although the 2:4:6‐trichloro‐ and 2:4:6‐tribromo‐phenoxyacetic acids are almost inactive, a:4‐dichloro‐6‐fluoro‐ and 2:4‐dibromo‐6‐fluoro‐ phenoxyacetic acids are very highly active. When a methyl group is substituted into the side‐chain of certain phenoxyacetic acids possessing 2:6‐ substituents, growth‐promoting activity is increased. Some of these findings conflict with recent theories on mode of action of phenoxy acids which are discussed in relation to the present work.
STUDIES OF THE BIOLOGY OF SCLEROTIUM CEPIVORUM BERK.
Authors: SCOTT M. R.
Published: February 2008

The white rot fungus (Sclerotium cepivorum) spread more rapidly between onion plants touching one another than between separated plants; the proportion of plants infected, over a range of spacing distances, was approximately inversely proportional to the spacing. The fungus invades the bulb through roots, and spread from plant to plant was prevented by not allowing contact between their roots.
THE EFFECT OF TEMPERATURE ON INFECTION WITH STRAINS OF CUCUMBER MOSAIC VIRUS
Authors: HITCHBORN J. H.
Published: February 2008

Cucumber mosaic virus strains differed in their ability to multiply in plants at 37° C. Some strains multiplied in inoculated leaves and produced systemic symptoms in plants at this temperature; plants systemically infected with one such strain remained infected after prolonged treatment at 37° C. Other strains did not appear to multiply in inoculated leaves at 37° C. and heat treatment was successful in freeing plants from infection with these. Tests with one strain of each type showed both to be rapidly inactivated in expressed sap at 37° C.

Strains of cucumber mosaic virus forming small necrotic local lesions in leaves of french bean var. Canadian Wonder, produced many fewer lesions in plants kept after inoculation at 25° C. for 24 hr. and then at 15° C. than in plants kept continuously at the lower temperature.
THE EFFECT OF DIFFERENT HOST PLANTS OF POTATO VIRUS C IN DETERMINING ITS TRANSMISSION BY APHIDS
Authors: WATSON MARION A.
Published: February 2008

A stock of potato virus C derived from Edgecote Purple potatoes in 1945 was not then transmitted by aphids, although more than 2000 aphids were used in conditions optimal for transmitting the serologically related potato virus Y. This stock of virus C has been propagated continuously since, by manual inoculation in a series of Nicotiana glutinosa and N. tabacum, and in 1955 it was transmitted by the aphid Myzus persicae (Sulz.): about one in twenty of the aphids transmitted it compared with one in two for potato virus Y.

Virus C derived from the Edgecote Purple potatoes in 1955 was not transmitted by aphids; both stocks of virus C produced only local lesions in Majestic potato leaves, and gave similar symptoms in tobacco.

When inoculated to Majestic potatoes and then returned to tobacco plants, potato virus C usually ceased to be aphid transmitted and did not recover this property in any of the subsequent subcultures.

Transmission from stock by aphids did not isolate a strain of virus C which was any more readily transmitted by aphids, indeed, for the first two or three subcultures, aphids usually transmitted more readily from plants inoculated manually. But the few isolates which remained aphid transmissible, after a second passage through potato, were rather readily transmitted.

These results suggest that the ability of a virus to be aphid transmitted is, at least in part, determined by the host plant in which it is multiplying, but the nature of the changes which determine this ability are unknown.
METHODS FOR THE STUDY OF BLOWFLY POPULATIONS
Authors: MacLEOD JOHN , DONNELLY JOSEPH
Published: February 2008

The advantages and disadvantages of laboratory‐bred material for fly‐marking experiments are discussed. Experimental evidence suggests that the tendency to uniformity of history of laboratory‐bred blowflies in relation to protein‐feeding produces no rhythm, apparent in the first 4 days at least, in their response to protein bait attractants.

The change from insectary environment to field conditions may sometimes result in either a greater or a lower proportionate recapture of a laboratory‐bred sample than that for a comparable wild‐caught sample. The nature of the difference is apparently associated with the weather conditions of the release area, but may be due to other causes, probably including physiological debilitation of laboratory‐maintained strains.