bluuebunny/crossref_metadata_2025 huggingface dataset:
OBSERVATIONS ON THE LIFE HISTORY AND BIOLOGY OF TIPULA LATERALIS MEIG.
Authors: WHITE J. H.
Published: February 2008

The occurrence of large numbers of larvae of Tipula lateralis Meig. in watercress beds has not hitherto been recorded. Observations on commercial beds and laboratory experimental work show this species to be primarily a saprophyte feeding on rotting submerged cress leaves, though it can develop during the final instar on green cress. Populations as high as 250,000/acre do not affect cress beds adversely.

There are two generations a year and probably a partial third. The life cycle can be completed in 63 days. Mating and oviposition are described, the preferred site for egg laying being on wet soil. The average number of eggs is over 500. The egg and first‐instar larva are described for the first time. There are four instars, the anal segment of the first being radically different from that of the remainder. It has been shown that pupation cannot take place under water as previously stated.
SOME FACTORS AFFECTING THE TRANSMISSION OF LEAF‐ROLL VIRUS BY APHIDS
Authors: KASSANIS B.
Published: February 2008

Datura tatula is a more suitable host than potato for studying the factors influencing the transmission of potato leaf‐roll virus by Myzus 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 which M. persicae aphids 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 infected Datura 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 virus X, but isolates of leaf‐roll virus were found that also varied in virulence.
STUDIES IN THE MODE OF ACTION OF INSECTICIDES
Authors: HOPF H. S.
Published: February 2008

Acetylcholine, choline chloride, acetyl‐β‐methylcholine, benzoylcholine, carbamyl choline, adrenaline and d‐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 by d‐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 cholinesters.
FACTORS AFFECTING THE SURVIVAL OF PLASMODIO‐PHORA BRASSICAE WOR. IN THE SOIL AND ITS ASSESSMENT BY A HOST TEST
Authors: MACFARLANE I.
Published: February 2008

The activity of Plasmodiophora brassicae Wor. 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 by P. brassicae but 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 that P. brassicae can 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 is briefly discussed.
SOME EFFECTS OF NITROGEN NUTRITION ON THE MORPHOLOGY AND ANATOMY OF MARROW‐STEM KALE
Authors: ARNEY S. E.
Published: February 2008

Marrow‐stem kale plants grown on plots receiving frequent additions of sulphate of ammonia showed a 40% increase in length of internode and a 25% increase in number of nodes per plant, and the leaf size was increased by between 50 and 70% over plants in plots receiving no N fertilizer. Leaves of kale continue to increase in area until they turn yellow, and the high N leaves showed a greater rate of increase in area at every stage in the life of the leaf.

Various features of leaf structure, such as stomatal index, and thickness of palisade and mesophyll, were unaffected by N treatment. The size of the epidermal cells of the leaves was very variable, and although the high N leaves showed a 12% increase in area per epidermal cell over the low N leaves, this difference is not statistically significant. The increased area of the high N leaves can therefore be attributed mainly to increased cell division during the life of the leaf. Only a very slight increase in rate of cell division is necessary to produce the observed effect.

The greater leaf area of the high N plants can be attributed mainly to increased size of individual leaves, but there was also a significantly greater number of living functional leaves per plant on the high N plants; at 23 weeks from sowing the high N plants had an average of 13.4 living leaves, while the low N plants had only 11.7 living leaves per plant.

There was an appreciable degree of N succulence in the high N kale leaves, which showed a 2% greater moisture content than the low N leaves.

A seasonal drift in epidermal cell size, palisade thickness, and total leaf thickness, is shown to be fully significant, statistically. Marked variations in stomatal frequency are barely significant at the 5% level.
STUDIES ON THE APHID TRANSMISSION OF A STRAIN OF HENBANE MOSAIC VIRUS
Authors: BRADLEY R. H. E.
Published: February 2008

A virus causing a wilt of Datura stramonium was identified as a strain of henbane mosaic virus. It causes necrotic local lesions in Nicotiana rustica, and local lesions are demonstrable in tobacco by staining with iodine. Some of the factors affecting its transmission by Myzus persicae (Sulz.) were studied quantitatively using these lesions.

Infective aphids differed little in their ability to cause infection, and usually produced two or three lesions. The duration of the feeding puncture did not affect the number of infections and had little effect on the percentage of aphids becoming infective. Transmissible virus did not seem to be continually imbibed while aphids fed on infected plants, and there were indications that it was acquired immediately before aphids withdrew their stylets from the leaf. Aphids became infective when allowed to make feeding punctures into epidermis stripped from infected leaves.

M. persicae transmitted during feeding punctures as brief as 5–10 sec; the probability of single feeding punctures resulting in infection reached a maximum with those lasting from 20 to 30 sec, during which the stylets did not penetrate as far as the centre of the epidermal cell and little or no saliva appeared to be ejected. M. persicae did not transmit the virus when its stylets were artificially wetted with infective sap.

Periods of darkness before inoculation with datura wilt virus increased the susceptibility of Nicotiana rustica to infection by rubbing, but not to infection by aphids.
THE CHEMICAL CONTROL OF WATER WEEDS IN THE GEZIRA AREA OF THE SUDAN
Authors: JONES K. WILSON , ANDREWS F. W.
Published: February 2008

Chlorophenoxyacetate weed‐killers have been tested for the control of aquatic weeds in the canals of the Sudan Gezira. Using water in tanks, it was shown that 10 parts per million of sodium 2‐methyl‐4‐chlorophenoxyacetate (Methoxone) or of sodium 2:4‐dichlorophenoxyacetate (Fernoxone) would kill most of the angiospermous water‐weeds found in the Gezira area.

Small‐scale field experiments, using channels of known water capacity, have shown that not only leaves and stems but also seeds and underground rhizomes were killed in treated stagnant water, provided that the weed‐killers were applied as dusts. The water remained toxic to crop plants for approximately 7 weeks after treatment.

In a large‐scale experiment in 1950, treating normal irrigation canals, temporary weed clearance was attained, re‐infestation was delayed, and one major canal, 4.5 km. long, remained weed‐free 12 months after treatment.
DRY‐ROT DISEASE OF THE POTATO
Authors: BOYD A. E. W.
Published: February 2008

A laboratory method is described in which a modified hypodermic syringe is used to inoculate potato tubers with Fusarium caeruleum. This injection method gives consistent results and permits reliable assessments of factors such as varietal susceptibility.

The occurrence of arrested lesions is noted.

Suspensions of very high spore concentration or of spores already germinated did not greatly increase the amount of dry rot above that given by the standard too spores per inoculation, provided that spore germination was adequate.

The size of tuber and site of inoculation were found to have a considerable effect upon the results of inoculation experiments, large tubers being more susceptible than small ones and the heel end being more susceptible than the rose end. The necessity for uniformity of material used in inoculation experiments is emphasized.
SOME EFFECTS OF HIGH TEMPERATURE ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION WITH VIRUSES
Authors: KASSANIS B.
Published: February 2008

When plants were kept at 36°C. for some time before inoculation, their susceptibility to infection by five mechanically transmissible viruses was greatly increased. When kept at 36° after inoculation, fewer local lesions were produced than at lower temperatures, but the effects of the post‐inoculation treatment differed with different viruses. Tomato spotted wilt and tobacco mosaic viruses multiply in plants at 36°, and the post‐inoculation treatment reduced the local lesions they caused to numbers that varied between 10 and 90% of the control; these two viruses also have large thermal coefficients of heat inactivation. By contrast, tobacco necrosis, tomato bushy stunt and cucumber mosaic viruses, were much affected by post‐inoculation treatment, lesion formation being completely prevented by exposure to 36° for a day or more. These three viruses appear not to multiply in plants at 36°, and although they have high thermal inactivation points, they have small temperature coefficients of thermal inactivation.

The extent to which lesion formation was affected by pre‐ or post‐inoculation exposure of plants to 36° depended not only on the length of the treatment, but also on the physiological condition of the plants.

The symptoms of infected plants changed considerably if kept at 36°. At 36°Nicotiana glutinosa, inoculated with tobacco mosaic virus, gave chlorotic local lesions instead of necrotic ones, and became systemically infected. When systemically infected plants were brought to ordinary glasshouse temperature, the infected tissues all collapsed and died in a day.
SOIL SAMPLING FOR WHEAT‐BLOSSOM MIDGES
Authors: GOLIGHTLY W. H.
Published: February 2008

A method of assessing the population of wheat‐blossom midges by the recovery of the cocoons from soil is described.

In the dry summer of 1947, considerable numbers of larvae of Sitodiplosis mosellana Géhin were still in the ears at the time of harvesting. Burning the straw immediately after combining may considerably reduce the numbers of midges.

The majority of the larvae are found in the top 3 in. of the soil although a considerable number may be found from 3 to 6 in. Headland infestations may be lighter than the rest of the field.

Cocoons of S. mosellana remain viable in the soil for several years, and 150,000 per acre were recovered in February 1951 from a field which had not had a wheat crop since 1944. At the same time 50,000 Contarinia tritici Kirby cocoons per acre were found in a field which was last under wheat in 1947.

Viable pupae were successfully obtained by soil sampling, and the pupation in the soil and subsequent emergence of the midges can be followed. Thus it is possible also to estimate the numbers of midges that will emerge.

Progress has been made towards predicting outbreaks of these two midges.
SYSTEMIC FUNGICIDES INTRODUCTION
Authors: Wain R. L.
Published: February 2008

The idea of controlling plant diseases by introducing curative chemicals into the plant goes back many years. All the early work, which has been reviewed by Müller (1926), was of an empirical nature and although claims were made from time to time that particular treatments were effective, no clear and reliable method ever became established for controlling a plant disease by internal therapy. Within the last few decades, however, such treatment for certain animal diseases with substances possessing antibacterial properties has given spectacular results. This success in the animal led to a renewed interest in the control of plant diseases by similar means, though it was of course recognized that the animal, with its circulating blood system capable of carrying chemicals rapidly to all tissues, is very different from the plant.
THE EVALUATION OF SYSTEMIC FUNGICIDES BY MEANS OF ALTERNARIA SOLANI ON TOMATO
Authors: Stubbs J.
Published: February 2008

I wish to deal briefly with the method we use at the Hawthorndale Laboratories for investigating the systemic fungicidal activity of griseofulvin and other materials. Our work on systemic fungicides has necessarily depended on our working out a suitable and reliable technique.
ROOT INJURY AS A FACTOR IN THE ASSESSMENT OF CHEMOTHERA‐PEUTANTS BY THE TOMATO FUSARIUM WILT TEST
Authors: Keyworth W. G.
Published: February 2008

Studies of the tomato Fusarium wilt test for screening chemotherapeutants were made by the writer at the Connecticut Agricultural Experiment Station, U.S.A., during 1951. The test compounds were applied on ten successive days to the roots of tomato plants growing in sand. The plants were then uprooted, their roots washed and dipped in a bud‐cell suspension of F. oxysporum lycopersici and the plants re‐potted. A standardized assessment of wilt and vascular discoloration was made some 21 days later, by which time the control plants were usually severely diseased. Several compounds greatly reduced disease severity.
PÓT TESTS OF NEMATICIDES AGAINST POTATO‐ROOT EELWORM
Authors: PETERS B. G.
Published: February 2008

Details are given of nematicidal tests, directed against the potato‐root eelworm, in 81. glazed pots of infested soil. The soil was sampled a few weeks after injection to secure data on the kill achieved, by counting the eelworm larvae hatching in root diffusate. A potato tuber was then planted in each pot and yielded information on phytotoxic or soil‐amendment effects. A second soil sample at the end of the season showed the degree to which the eelworm population had recovered after treatment. With only duplicate pots, and single batches of 100 cysts from each pot, clear‐cut results were achieved with D–D mixture and ethylene dibromide. In the present pilot test, the data were handled by ordinary analysis of variance methods, by which the lowest significant percentage kill was 73%, but the methods could be adapted for purposes of probit analysis.
THE CHANGING NUMBERS OF APHIS FABAE SCOP., FLYING AT CROP LEVEL, IN RELATION TO CURRENT WEATHER AND TO THE POPULATION ON THE CROP
Authors: JOHNSON C. G.
Published: February 2008

Aphis fabae Scop, flying over bean crops in the summer usually show a double peak of aerial density during the day; scarcely any flight occurs at night. The first peak is thought to be composed mainly of alatae moulted since the previous evening and the decline of the peak to their depletion as they fly away from the crop. The second peak is probably composed mainly of alatae moulted during the same day. Lack of flight at night is due partly to low temperature, partly to lack of alatae old enough to fly and probably also to low light intensity.

Contrary to expectation changes in aerial density from hour to hour are only very weakly correlated with weather factors, especially wind‐speed. The total numbers in each of the two peaks do show a low but significant correlation with both wind‐speed and temperature in one case, but even then only a relatively small amount of the variation in aerial numbers is associated with weather changes. Other factors, particularly rapid changes in the numbers of alatae on the crop caused by moulting, accumulation before flight and depletion by flight evidently obscure changes due simply to varying flight behaviour. Thus because of large populations on the crop, it is possible to have quite large numbers in the air even when the weather is relatively unfavourable for flight.

In addition to these observations, the relation between total numbers caught at different wind‐speeds shows that most of the migration occurred in winds when the aphids could have had no control over the general direction of flight. The current view that most migration takes place only in calm weather can therefore no longer be held.
THE USE OF TETRA‐ AND PENTA‐CHLORONITRO‐BENZENES IN THE CONTROL OF BOTRYTIS DISEASE AND RHIZOCTONIA ATTACK OF LETTUCE
Authors: LAST F. T.
Published: February 2008

Botrytis disease in the ‘spring’ lettuce crop was controlled by six talc dusts containing s, 10 or 20 % of tetra‐ or penta‐chloronitrobenzene. All the dusts increased equally the final stand in the frames, but the number of seedlings with stem lesions decreased with increasing concentrations of both compounds. At similar concentrations the tetra‐ was more effective than the penta‐compound. The percentage survival in the field was increased by the dust treatments. The 20% dust of the penta‐ was only as effective as the 5% dust of the tetra‐compound.

The dusts affected the leaves, stunted the seedlings and delayed hearting. At similar concentrations the tetra‐ was more harmful than the penta‐compound. The 5 % dust of the tetra‐ was less damaging than the 20% dust of the penta‐compound.

The spread of Rhizoctonia solani was reduced by incorporating the dusts with soil. Again, the 5% tetra‐ dust was as effective as the penta‐ dust at 20%. At 12·5 g. of dust per 20 kg. of soil, none of the dusts retarded the rate of emergence of lettuce seedlings but the highest concentration of the tetra‐ series reduced the number emerging.

Foliage applications of two dusts, 5% tetra‐ and 20% penta‐ dusts, controlled the spread of R. solani.
OBSERVATIONS ON APPLE CANKER
Authors: CROWDY S. H.
Published: February 2008

Field observations on leaf‐scar canker of apple confirm its importance in the southwest of England: on a heavily infected tree more than 5% of the current year's growth may be damaged. Leaf scars may become infected by spores of Nectria galligena which are sucked into the tracheids of a freshly exposed scar where they develop in a relatively protected environment. These freshly exposed scars become much less susceptible to infection after approximately one hour.

Infections established in leaf scars may develop immediately into cankers or they may be confined by a suberized or gum barrier. Mycelium from some of these confined lesions may spread into the surrounding healthy tissue through growth cracks when the buds develop. The lesions extend throughout the winter and spring; usually the scars earliest inoculated are the first to show cankers. It seems possible that infections of this type might be controlled by eradicant sprays applied just before leaf‐fall.
SCAB, CANKER, AND BRANCH BLISTER OF APPLE AT EAST MALLING IN RELATION TO NUTRITIONAL TREATMENT OF THE HOST
Authors: MOORE M. H. , BENNETT MARGERY
Published: February 2008

On the sandy loam at East Mailing, moderate annual dressings of inorganic sources of nitrogen and potash exerted no consistent influence on the incidence of apple scab, even when the dressings were continued over an eleven‐year period on established trees of four different varieties on M.IX rootstock. Likewise, no influence of such dressings continued over five seasons was shown on the incidence of apple canker on the rootstock M.VIII, which was grown under conditions favourable for severe infection.

There was evidence from early observations that grassing‐down to excess can reduce the incidence of scab, but only at the expense of nitrogen starvation in the trees. Short‐term mixed leys had no such effect.

The incidence of branch blister, a functional disease associated with adverse soil conditions and retarded vigour, was greatly reduced in the variety Cox's Orange Pippin by potash manuring, and was further influenced by the rootstock.
STUDIES IN THE BACTERIAL DIE‐BACK AND CANKER DISEASE OF POPLAR
Authors: SABET K. A. , DOWSON W. J.
Published: February 2008

The bacterial die‐back and canker of poplar is characterized by dark necrotic areas in the leaves, die‐back accompanied by cracks in the bark of 1–4‐year‐old branches, and by cankers on the trunk and branches of different ages. The cankers may be ‘closed’ or ‘open’ and when moist exude slime containing bacteria.

The disease is caused by Pseudomonas syringae f. sp. populea, a new forma specialis closely resembling Ps. syringae in bacteriological characters but differing from it in parasitism. The association of the slime with the bacteria is essential for the production of typical lesions.

Inoculations with the pathogen alone, or in association with other organisms produce atypical symptoms.

The bacteria attack the cortical parenchyma and occasionally invade the xylem vessels.
Studies On Plant Growth‐Regulating Substances
Authors: FAWCETT C. H. , OSBORNE DAPHNE J. , WAIN R. L. , WALKER RUTH D.
Published: February 2008

Eight series of aryloxyacetic, α‐aryloxy‐propionic, ‐butyric and ‐isobutyric acids have been synthesized, and their growth‐regulating activity has been assessed using six different test methods, viz. tomato‐leaf epinasty, Avena cylinder, Avena curvature, tomato parthenocarpy, tomato‐leaf rooting and the Went pea test. The ability to induce morphogenic effects in tomato plants was also studied. The results are critically discussed and shown to be consistent with the view that in tests involving only cell extension the presence of an α‐hydrogen atom is usually necessary for growth‐regulating activity to be shown. In tests in which cell division occurs this effect is not so clearly defined, though the presence of an α‐hydrogen does, in general, correlate with growth‐regulating activity.
A STUDY OF THE EPIDEMIOLOGY OF CLUB‐ROOT DISEASE OF BRASSICAE
Authors: COLHOUN JOHN
Published: February 2008

The epidemiology of club‐root disease of cabbages has been studied by growing plants in naturally and artificially contaminated soils under varying conditions of moisture, temperature, spore load, soil reaction and lime content.

The disease can occur in both acid and alkaline soils. By attention to the interaction of factors influencing infection the presence or absence of an attack, as well as its extent and severity, can be predetermined.

In acid soils, very favourable conditions for the incidence of the disease are a moisture content equal to about 70 % of the maximum water‐holding capacity and a mean air temperature of 18–23° C. Fluctuations in soil moisture at high levels provide as favourable conditions for infection as a high constant moisture. The level of spore load (within the limits of 103 to 2.5 × 107 spores per g. of soil) does not influence the number of diseased plants in acid soils when favourable conditions for an attack and for good growth of the host are provided. Under less favourable conditions spore load does exercise an effect.

The disease occurred in both naturally and artificially contaminated soils showing a pH of 7.8 at planting time; in the former, the pH was adjusted to 7.8 by liming in the field over a period of years, and in the latter by treatment with pure calcium hydroxide shortly before planting. In alkaline soils infection is favoured by high moisture content, high temperature and high spore load. Satisfactory conditions for infection are provided, as in acid soils, at a moisture content of 70% of the maximum water‐holding capacity, it being immaterial whether this level is constantly maintained or fluctuating at high levels. No diseased plants occurred when the soil moisture fluctuated or remained constant at low levels. Severe attacks occurred in alkaline soils when the air temperature fluctuated between points much higher and lower than the mean temperature of 23° C. It is suggested that the optimum temperature for infection is higher than 23° C. In alkaline soils at moisture contents and temperatures favourable for infection a heavy attack can develop only in the presence of a high spore load.

In general, it was found that the conditions which were most favourable for the incidence of the disease also favoured the intensity of its development.

No substantial differences in the incidence of the disease in different soils were found, but more plants contracted club root in the lighter soils when conditions were less favourable for infection.

The results obtained suggest that while liming in the field may control the disease if the spore load is low, even very heavy applications of lime may not be effective if the soil is heavily contaminated and soil moisture and temperature do not operate as limiting factors.
Saprophytic Behaviour Of Some Cereal Root‐Rot Fungi
Authors: BUTLER F. C.
Published: February 2008

The ability of four cereal root‐rot fungi, Helminthosporium sativum, Curvularia ramosa, Ophiobolus graminis and Fusarium culmorum, to colonize wheat straw as saprophytes has been investigated. Test pieces of straw were buried in a graded dilution series of maizemeal‐sand culture of the test fungus with unsterilized soil. For assessing percentage straws colonized, three methods were compared: (1) isolation on agar plates, (2) Garrett's (1938b) wheat‐seedling test and (3) incubation on moist sand, to promote sporulation (the ‘sand‐plate’ test). Curvularia ramosa and Fusarium culmorum were found to behave as vigorous competitive saprophytes of the soil‐inhabiting type, whereas Helminthosporium sativum and Ophiobolus graminis proved to be weak saprophytic colonizers of the specialized root‐inhabiting type.
OBSERVATIONS ON THE UPTAKE AND TRANSLOCATION OF FIVE ACTINOMYCETE ANTIBIOTICS BY CUCUMBER SEEDLINGS
Authors: PRAMER D.
Published: February 2008

The uptake and translocation of five actinomycete antibiotics by cucumber seedlings has been investigated by qualitative and quantitative techniques.

Chloromycetin and streptomycin were absorbed from nutrient solution by the root system of cucumber seedlings and translocated to the leaves. The streptomycin concentration of leaf tissue increased with time to a level above that in the nutrient solution, whereas the chloromycetin concentration tended to remain constant at a level below that in the nutrient environment. Chloromycetin and streptomycin were identified in the leaf tissue of treated seedlings by paper chromatography.

No convincing evidence of uptake and translocation of aureomycin, neomycin or terramycin was obtained.
STUDIES IN THE INTERACTIONS BETWEEN SPECIES OF VERTICILLIUM
Authors: ISAAC IVOR
Published: February 2008

It is shown that five parasitic species of Verticillium, viz. V. alboatrum, V. Dahliae, V. ticorpus, V. nigrescens and V. nubilum, developed together on agar media or wheat grains as saprophytes without causing mutual antagonism but, when these were injected together, as a mixed spore suspension, into antirrhinum and tomato, suppression of V. tricorypus, V. nigescens and V. nubilum by either one or other of the remaining two invariably resulted. The two most virulent pathogens, V. alboatrum and V. Dahliae, were not recoverable from soil after the elapse of 6 months from the time of inoculation; while the other three less virulent pathogens could be isolated after about 12 months in the soil. It is concluded that V. alboatrurn and V. Dahliae may be described as ‘root inhabiting’ and V. nigrescens and V. nubilurn as ‘soil inhabiting’, while V. tricorpus may be considered as an intermediate type.
DEPOSITION OF AIR‐BORNE LYCOPODIUM SPORES ON PLANE SURFACES
Authors: GREGORY P. H. , STEDMAN O. J.
Published: February 2008

The deposition of Lycopodium spores on sticky surface traps, including vertical and horizontal microscope slides and Petri dishes as used in routine aerobiological survey, was studied in a small wind tunnel at wind speeds from approximately 0.5–9.5 m./sec.

Deposition results from several processes acting singly or in combination. The pattern of deposit on a microscope slide orientated at angles varying from o to 90° to the wind, with gravity either positive, neutral or negative, indicates that, except on a surface parallel to the wind at the lowest wind speed, sedimentation under gravity plays a minor part in deposition on plane surfaces. As the wind speed is increased the deposit is decreased because of ‘edge shadow’. At the highest wind speed the deposit is as large on the lower as on the upper surface of the horizontal slide, which suggests deposition by turbulence. Deposition by impaction against a vertical strip increases with wind speed, and efficiencies observed are lower than for cylinders of the same diameter. The deposit on slides inclined at angles of 45° or less to the wind direction is increased by impaction of an ‘edge drift’. The interaction of these various deposition processes on mean deposition at different angles and wind speeds gives a series of curves with a maximum at 90° at 9.5 m./sec. and with minima at 0, 90 and 180° at wind speeds lower than 9.5 m./sec. At these lower wind speeds there are two maxima in the range 20–70° and 135–150° respectively.

Deposits on Petri dishes show rim effects differing at different wind speeds. These can be eliminated by sinking the dish below a flat surface.

Blow‐off from non‐sticky surfaces is least at about 45°, and greatest at 0°.

Spore concentration in air is difficult to estimate from the deposits on planesurface traps, because horizontal traps under‐record at medium wind speeds, and because vertical traps are very sensitive to changes in wind speed. Power‐operated suction traps are to be preferred when data on spore concentrations are required.
TOXICITY TO THE GRAIN WEEVIL OF SOME ALKYL COMPOUNDS APPLIED AS VAPOURS
Authors: HASSALL KENNETH A.
Published: February 2008

A simple fumigation technique is described, which allows twenty to thirty tests to be made at once with different concentrations of vapour. The 50% lethal doses (LD 50's) of different substances were estimated by the probit method of analysis, the slopes of the probit lines also being recorded.

The present work had two aims, the first being the investigation of the relationship of the molar LD 50's of different substances to one another. The substances were so chosen that comparison could be made both within homologous series and, for compounds with the same alkyl groups, between them. The second aim was to find out to what extent the slopes of probit lines varied for compounds believed to have like and unlike modes of action.

Some of the series were known to contain substances with an anaesthetic or narcotic effect, symptoms which are frequently attributed to substances with some type of physical action. Other series included compounds which had little or no observed narcotic effect, which were lethal at low vapour concentrations and for which evidence exists that they possess chemical toxicity for some organisms. A series which might reasonably be expected to have some of the attributes of both the ‘physical’ and chemical toxicants was also used.

On plotting log molar LD 50's against the number of alkyl carbon atoms, the well‐known linear relationship was noted for the series with an observed narcotic effect, the constant logarithmic difference being large in all except the alcohol series. However, the upper members of the series which were presumed chemically toxic also possessed toxicities which showed a constant logarithmic difference, but a much smaller one than that characteristic of the first group. The bromide series had for its higher members a constant difference in the log LD 50's intermediate between these two groups. On the other hand, the lower members of the bromide, iodide and thiocyanate series had log LD 50's which were not related in any obvious way. These experimental results are discussed in terms of phase distribution and chemical reactivity.

Two poisons whose modes of action on a given organism are much alike often show parallel probit regression lines, especially if they possess similar chemical constitutions. There is, however, no reason why this should necessarily be the case, and in the present investigation it was found that compounds with an observed anaesthetic or narcotic effect often had very different probit slopes. Within most series, the slope was not greatly different except for the lower and higher members, for which it often appeared higher than for the intermediate ones. Between series, a rough correlation often existed between probit slope and median response vapour pressure.
The Control Of Blowflies Infesting Slaughter‐Houses
Authors: GREEN A. A.
Published: February 2008

Field experiments on the control of blowflies have been carried out at a large slaughter‐house which was heavily infested both by flies breeding on the premises and by those attracted from surrounding districts.

The control of breeding by admixture of a larvicide with slaughter‐house refuse proved to be impracticable. Although a single treatment of the surface of refuse was ineffective, daily applications of DDT or BHC markedly reduced the degree of infestation and killed some emerging adults.

The introduction of a scheme for rotational storage and collection of refuse and a general improvement in sanitary conditions, together with a daily application of 5% DDT dust to refuse and nearby vegetation, resulted in the prevention of breeding on the premises and a very considerable reduction in the adult population.

Results of experimental applications are compared with those obtained in practice using unskilled labour.
BIOLOGICAL INVESTIGATIONS INTO THE VALIDITY OFCONTARINIASPECIES LIVING ON THE CRUCIFERAE, WITH SPECIAL REFERENCE TO THE SWEDE MIDGE,CONTARINIA NASTURTII(KIEFFER)*
Authors: STOKES BARBARA M.
Published: February 2008

Biological investigations have proved thatContarinia nasturtii(Kieffer),C. isatidisRübsaamen and C.ruderalis(Kieffer) are in reality one species. The namesC. isatidisRübsaamen andC. ruderalis(Kieffer) are therefore synonyms ofC. nasturtii(Kieffer). Considerable doubt has been thrown on the authenticity of several other species.

The host plant range ofC. nasturtiiwas already known to be very extensive. Fourteen additional host plants, including two tetraploid varieties and several weeds have been added during this investigation. Eight were established by experiments, and the remaining six have previously been recorded as host plants ofC. ruderalis. In addition,Brassica nigra, Lepidium sativumandRapistrum rugosumhave since been established as host plants ofContarinia nasturtiiin Holland.Diplotaxis tenuifoliaandLunaria annuaare suspected as host plants, but the evidence is not yet conclusive.
OBSERVATIONS ON THE OCCURRENCE OF THE EELWORM, PRATYLENCHUS PRATENSIS FILIPJEV, IN DELPHINIUM ROOTS
Authors: STONE L. E. W.
Published: February 2008

Pratylenchus pratensis has been found associated with lesions on delphinium roots: its presence in the tissues is best demonstrated by a modification of the Flemming staining method.

At specific sites, the severity of delphinium root‐rot was correlated with the soil population of P. pratensis. After infested soils had been fumigated with methyl bromide, delphiniums grown in the treated soils had more vigorous root systems, containing fewer eelworms per unit weight than those grown in untreated soil. The use of D‐D also shows promise as a control measure against P. pratensis.

No pathogenic fungus has been found in the delphinium root lesions.
THE VEGETATIVE DEVELOPMENT OF THE POTATO PLANT
Authors: TAYLOR C. E.
Published: February 2008

A study of the vegetative growth of potato plants indicated that all varieties grown under identical conditions are likely to show similar growth rates during the early stages of development.

Differences in total leaf area per plant between varieties became apparent at the stage when rapid development of axillary shoots from the main axis occurred. The maincrop varieties, Stormont Dawn and King Edward, attained a greater total leaf area than the early varieties, Ulster Chieftain and Arran Pilot, because of the greater development of axillary shoots.

It is suggested that the number of nodes produced beneath the terminal inflorescence on the main axis approximates to a constant value, independent of variety. Varietal differences were manifested in the distribution between leaves above ground and stolons below, the early varieties producing fewer leaves above ground than the maincrop, in inverse proportion to the number of underground stolons.

The yields of tubers per plant are given for four varieties. Differences between varieties in the rate of tuber formation are related to differences in the development of haulms.

It is considered probable that the potato plant exhibits a basic growth form which is modified in each variety in a characteristic manner according to the stage in the growth cycle and the rate at which the growth substances are distributed to the various organs of the plant.
EXPERIMENTS ON THE POSSIBLE CONTAMINATION OF HONEY WITH SCHRADAN
Authors: JONES G. D. GLYNNE , THOMAS W. D. E.
Published: February 2008

The reported low toxicity of schradan to honey‐bees has been confirmed. This has led to the consideration of the possibility that this systemic insecticide might be present in nectar and subsequently appear in honey in an unchanged form.

Using radioactive schradan labelled with 32P, it has been shown that spray applications of this insecticide to mustard and borage plants result in the contamination of nectar. A series of nectar samples taken over a 4‐week period following spraying showed on radio assay a progressive decrease in total 32P content and also in the amount of schradan present in proportion to the decomposition products. The highest figure recorded for the schradan content of nectar was 21 p.p.m.

Tests on the stability of schradan in contact with the honey stomach of the bee and also in contact with the enzyme invertase, in vitro, showed that no appreciable breakdown occurred. Furthermore it was shown that schradan was stable in contact with honey over a period of 2 1/2 months.

It is concluded that this systemic insecticide may appear in an unchanged form in the honey obtained from the nectar of plants which have been sprayed less than 4 weeks previously.
THE INFLUENCE OF IRON SUPPLY ON TOXIC EFFECTS OF MANGANESE, MOLYBDENUM AND VANADIUM ON SOYBEAN, PEAS AND FLAX
Authors: WARINGTON KATHERINE
Published: February 2008

The investigations were carried out in nutrient solution with iron as ferric citrate and nitrogen in the form of nitrate.

Addition of 2.5 p.p.m. vanadium to plants in which iron chlorosis was already‐established, either by a lack of iron or by excess manganese, failed to counteract the condition, and caused toxic symptoms.

Reduction of the standard iron supply to ½ or ⅓ accentuated the toxicity of 2–5 or 5 p.p.m. V to soybean and flax, but a similar reduction in phosphorus had no influence. Toxicity to peas, however, was increased when the phosphorus was reduced to 1/10, provided the iron level was high (20 p.p.m. Fe).

Raising the iron supply to 20 or 30 p.p.m. Fe counteracted the toxicity of manganese (10 p.p.m.), molybdenum (40 p.p.m.) and vanadium (2.5 p.p.m.), but the result was less marked when these three elements were combined. Iron supplied in successive, small doses proved less efficient in overcoming molybdenum or vanadium, but not manganese excess, than the same amount of iron supplied in fewer and larger quantities. Varying the iron supply had little effect when the concentration of the three elements was low. When increased iron supply had reduced the chlorosis caused by high manganese or vanadium, it also reduced the manganese and vanadium contents of the shoot (p.p.m./d.m.), but the molybdenum content was only lowered by high iron when given in non‐toxic concentration (0.1 p.p.m. Mo) combined with excess manganese.

The iron content of the shoot (%/d.m.) was scarcely affected by the amount of iron supplied, but was generally reduced by high concentrations of manganese, molybdenum or vanadium.

Results regarding the effect of vanadium on the phosphorus content of the shoot were conflicting, and differences occurred only when the iron supply was low. Here the phosphorus content of soybean and peas was generally reduced, while that of flax was increased.

Yield data for soybean and flax indicated an interaction between manganese with both molybdenum and vanadium if the iron supply was low, but none between molybdenum and vanadium. The effect of all three metals was additive in respect to iron.
A MICRO‐DROP APPLICATOR AND ITS USE FOR THE TREATMENT OF CERTAIN SMALL INSECTS WITH LIQUID INSECTICIDE
Authors: HEWLETT P. S.
Published: February 2008

An instrument has been constructed for applying minute drops of liquid insecticide to selected parts of individual insects. The principle of the instrument, which is not original, is to express minute amounts of liquid from a hypodermic syringe, and blow the drop from the needle tip by a puff of air. This model is considered to have advantages over previous models working on the same principle. In particular, a very convenient form of fitting was developed for blowing the drop from the needle tip, and fittings of this type could be incorporated in existing similar applicators with little modification of the latter. The high directional accuracy of dropfire necessary for treating selected parts of small insects was achieved.

An immersion method was developed for determining the sizes of individual drops of Shell oil P31 delivered, and hence the uncontrolled variability of drop‐volume. It showed that the standard deviation in the volumes of drops intended to be equal in size was about 9% of a mean volume of 0.017 μ1. falling progressively to about 2% as the mean volume increased to 0.33 μl. These standard deviations, however, are of limited value, because the sizes of successive drops delivered appeared frequently to be correlated. A method in which the drops are delivered on to an oleophobic surface for measurement of the diameters of the oil lenses formed was found insufficiently accurate for determining the relative variability of drops of P31.

A suction method was devised for manipulating, without anaesthetization or chilling, small beetles such as Calandra and Tribolium. This enabled large numbers to be individually treated with the applicator in a reasonable time. A similar but slower method was used successfully with the larvae of Ephestia. The biological results achieved have been very satisfactory.

The effects of uncontrolled variation in drop size on dose‐response data are discussed.
THE EFFECT OF BODY WEIGHT ON THE RESISTANCE TO INSECTICIDES OF THE LAST‐INSTAR LARVA OF DIATARAXIA OLERACEA L., THE TOMATO MOTH
Authors: WAY M. J.
Published: February 2008

At a constant temperature of 24° C. the final larval instar of Diataraxia oleracea lasts about 10 days, during which its resistance to DDT and γ‐BHC as contact insecticides progressively increases up to the 5th or 6th day. It then suddenly decreases, this coinciding with cessation of feeding and the beginning of prepupal formation.

Between the 2nd and the 6th days the gross body weight of the last‐instar larva increases from about 0.27 to 0.65g. Under the conditions of the experiments, the LD50 of parathion, as a stomach poison, was linearly related to body weight; on the same basis TEPP was slightly less, and lead arsenate, slightly more, toxic to the larger than to the smaller larvae. However, DDT as a stomach or contact insecticide, and γ‐BHC as a stomach poison were notably less toxic to the larger larvae. For example, the increase in LD50 for an increase in larval body weight of × 2 was about × 11 for DDT as a stomach poison and about × 12 as a contact insecticide.

The order of effectiveness of the above insecticides as stomach poisons for the last‐instar larva of D. oleracea was parathion > DDT > γ‐BHC > TEPP = lead arsenate. Zinc fluoarsenate and rotenone were relatively non‐toxic. Larvae of D. oleracea were repelled by food leaf treated with an extract of natural pyrethrins.