bluuebunny/crossref_metadata_2025 huggingface dataset:
BROWN ROOT ROT OF TOMATOES
Authors: EBBEN M. H. , WILLIAMS P. H.
Published: February 2008

Tomato roots with brown root rot showed three types of lesion: cortical rot of fine roots, ‘corky root’, and basal stem rot. The fungi most commonly isocated from diseased roots were: Colletotrichum atramentarium, Chaetomium spp., Cephalosporium spp., Volutella ciliata, and a grey mycelial fungus sometimes producing pycnidia (Pyrenochaeta sp.). Other fungi isocated less frequently were: Myrothecium roridum, Petriella asymmetrica, Trichoderma airide, Phytophthora spp., Alternaria sp. and Fusarium spp. There were differences between the numbers of each species isocated from the three types of lesion in steamed and in unsteamed soils, and some seasonal variation.

Inoculation experiments with seedlings in vitro showed that Ckaetomium cochliodes and Petriella asymmetrica could infect radicles. On older plants growing in soil Colletotrichum atramentarium was the only effective pathogen. Culture filtrates from C. atramentarium, Chaetomium cochliodes, and P. asymmetrica decreased root growth when tested in vitro. Leachates from loam and a loam‐manure mixture decreased the growth of tomato root‐tip cultures; the effect of these leachates was altered by autoclaving.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M.
Published: February 2008

Antibiotic production in and around particles of plant debris in soil was studied. High yields of an antibiotic, shown by bioassay methods to be similar to gliotoxin, were obtained from wheat straws buried in a normal, unautoclaved; acid podsoc from Wareham Heath which had been inoculated with a strain of Trichoderma viride known to produce gliotoxin in culture media. Only a little of the antibiotic was produced in the soil immediately surrounding the straws. Much less was produced in straws buried in John Innes potting compost and none at all in straws buried in a Kettering loam. In no case was an antibiotic detected in straws from un‐inoculated soils.

If, however, the Kettering loam was acidified or, alternatively, the straws themselves were acidified and then buried in untreated Kettering loam, good yields of the antibiotic were obtained from straw extracts. Conversely, when the pH of Wareham Heath soil was raised by addition of calcium hydroxide to the soil no antibiotic activity could be detected in the straws. This suggests that the pH of the soil and of the food substrate has a profound effect on production of an antibiotic, assumed to be gliotoxin, by T. viride. The results obtained suggested that increased production of gliotoxin after autoclaving the straws was due to a decrease in the pH of the straws rather than to a release of nutrients.
THE OLFACTORY BEHAVIOUR OF LUCILIA SPECIES (DIPTERA) UNDER NATURAL CONDITIONS
Authors: CRAGG J. B.
Published: February 2008

Using an apparatus of the ‘two‐choice’ type under field conditions, it has been demonstrated that a wool‐factor forms an important part of the mechanism whereby female Lucilia sericata may be attracted to sheep. The ‘wool‐factor’ could not wholly be replaced by ammonium‐ or sulphydryl‐type attractants.

L. sericata was strongly attracted by the combination of ammonium carbonate/indole with sheep wool but less strongly attracted when ethyl mercaptan/hydrogen sulphide was used with sheep wool. L. caesar and L. illustris, on the other hand, were not markedly responsive to the ammonium‐type attractants but were strongly attracted by the sulphydryl mixture used either alone or in combination with sheep wool.

Temperature is an important element in the oviposition stimulus. The amount of oviposition by L. sericata was increased when substances known to induce oviposition were exposed at 30–40† C.

Sheep wool kept moist and incubated at approx. 38† C. under field conditions for 3 weeks did not attract L. sericata and oviposition did not occur on such wool. This suggests that bacteria normally present on the wool fibre as distinct from the skin, do not play an important part in rendering sheep susceptible to blowfly attack.
LABORATORY STUDIES ON THE CHEMO‐SENSORY REACTIONS OF BLOWFLIES
Authors: CRAGG J. B. , COLE PATRICIA
Published: February 2008

Attraction of various blowflies to sheep wool has been demonstrated under laboratory conditions using a choice‐chamber technique. The attractive factor in wool is intimately associated with the wool fibre for it does not disappear during storage and it is not completely removed by washing.

Only female flies were attracted to wool. The highest degree of attraction was obtained from fertilized females which had daily access to meat. Even in the absence of fertilization and meat, attraction was not completely abolished.

The species and strains tested can be placed in the following order in terms of strength of response to sheep wool: Lucilia sericata (British), L. cuprina (tested on damp floor)>L. sericata (Danish: country)> L. sericata (Danish: city), L. sericata (Australian) > L. illustris, L. caesar. No response was given by Calliphora vomitoria.

The olfactory organs involved in the response to wool are mainly on the antennae but antennaeless L. sericata and L. cuprina with some tarsi removed were still able to show some response to wool provided that they were tested on a damp floor. In the course of testing the olfactory responses it was also shown that the main humidity receptors are present on the antennae.

The existence of a ‘wool‐factor’ to which only certain strains of L. sericata and L. cuprina are specially sensitive offers a possible explanation for the greater efficiency of these species as myiasis‐producing forms.
SOME EFFECTS OF TANNIC ACID AND OF LEAF EXTRACTS WHICH CONTAIN TANNINS ON THE INFECTIVITY OF TOBACCO MOSAIC AND TOBACCO NECROSIS VIRUSES
Authors: THRESH J. M.
Published: February 2008

The inhibition of infection by tobacco necrosis and tobacco mosaic viruses by tannic acid, and by extracts of raspberry and strawberry leaves, was associated with the precipitation of the viruses. Precipitation and inhibition were reversible, and infective virus was obtained from the precipitate formed between the viruses and tannins. Infectivity was fully restored by diluting mixtures of virus and tannin adequately and partially restored by adding alumina or nicotine sulphate.

Viruses and tannins are thought to form non‐infective complexes, in which the virus and tannin components are held together by co‐ordinate linkages or hydrogen bonds.

Macerating tobacco leaves infected with tobacco mosaic virus together with raspberry leaves greatly decreased the infectivity of the extracts; adding nicotine sulphate to the mixture of leaves before it was ground increased the infectivity, even though nicotine sulphate alone decreases the infectivity of tobacco mosaic virus. Even in the presence of nicotine sulphate, much of the virus was precipitated by substances from the raspberry leaves.

Extracts of roots of Fragaria vesca plants, infected with a tobacco necrosis virus, were more infective when made by macerating the roots with four times their weight of buffer at pH 8 than when made without buffer. Various methods are suggested for facilitating the transmission of viruses from plants that contain tannin.
DETERMINATION OF THE RESISTANCE OF LOCUSTS TO DNC IN RELATION TO THEIR WEIGHT, AGE AND SEX
Authors: MacCUAIG R. D.
Published: February 2008

Experiments have shown that the resistance of adults of the desert locust (Schistocerca gregaria) and the African migratory locust (Locusta migratoria migratorioides) to DNC applied as a contact poison to the ventral surface of the abdomen is directly related to their body weight, irrespective of age or sex.

Varying the site of application of the insecticide had little effect on the susceptibility of the insects except when the dose was applied to the wings or femur, these being less effective sites of entry for the poison.

Increasing the post‐treatment temperature from 25 to 36°C. had no noticeable effect on mortality, but the speed of action of the insecticide was much increased.
THE INFLUENCE OF STORED POLLEN AND OF COLONY SIZE ON THE BROOD REARING OF HONEYBEES
Authors: ALLEN M. DELIA , JEFFREE E. P.
Published: February 2008

Four hundred and thirty records of the numbers of bees in honeybee colonies and of the amounts of brood and pollen present have been kept during various months of the years 1945‐53, and the data have been used to calculate total and partial regression coefficients showing the influence of stored pollen and of colony size on brood rearing throughout the year.

It was found that pollen storage and colony size were correlated but that, even allowing for this, colony size and pollen both independently influenced brood rearing.

The annual distribution of the total regression coefficients of brood on pollen was somewhat similar to the brood curve itself, rising from a minimum in October and November to a maximum in midsummer, while the partial regression coefficients showed less clearly marked but similar features.

Both total and partial regression coefficients showing the influence of colony size on the amount of brood reared were also at a minimum in October and November, but reached their peaks in May.

The quantities of brood present in these colonies at Aberdeen, Scotland, followed a pattern similar to that given by Nolan for colonies near Washington, D.C.
SOME SOIL FACTORS AFFECTING VERTICILLIUM WILT OF ANTIRRHINUM
Authors: ISAAC IVOR
Published: February 2008

Variations in the application rates of chalk and superphosphate and the omission of all the fertilisers had no visible effect on the incidence of wilt caused by any of the five Verticillium species.

he literature dealing with the influence of soil conditions upon the Verticillium wilt of a wide range of host plants is reviewed. It is shown that the species V. alboatrum, V. dahliae, V. nigrescens, V. nubilum and V. tricorpus vary inter se in their pathogenicity to Antirrhinum majus, and that their infectivity may be influenced by soil treatments. Thus, in pot cultures, the incidence of antirrhinum wilt induced by Verticillium dahliae and V. nigrescens was reduced by increasing sulphate of potash or ammonium sulphate; or by decreasing soil moisture. Very wet soil and heavy dressings of hoof‐and‐horn were the only conditions under which V. nubilunt and V. tricorpus induced wilt symptoms. Z7. albo‐atrunt was the most virulent species tested; none of the soil treatments decreased its pathogenicity.
VASCULAR INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E. F. SMITH) DOWSON
Authors: WICKENS G. M.
Published: February 2008

Cotton seedlings raised under glass from seed pre‐soaked in a water suspension of Xanthomonas malvacearum, and watered by sub‐irrigation only, developed atypical dull green flaccid areas extending from the periphery of the cotyledons. Later symptoms that variably developed were: vascular discoloration, not necessarily continuous, in the petioles of affected cotyledons, in the hypocotyl, and in parts of the plant above the cotyledonary node; premature withering of cotyledons; dull green flaccid areas in true leaves, not necessarily the lowest, later turning brown and drying, with usually a chlorotic margin; parenchymatous attack in stems, petioles and leaves. Evidence is adduced, from the progression of symptoms and from associations between them, and from isolations of the pathogen from various parts of the plant at different stages, that the course of this type of infection is primarily vascular, progressing from the edges of cotyledons into the hypocotyl and thence upwards in vascular tissues. Thence the infection may break out at any time into parenchymatous tissues, leading to the more characteristic forms of the disease, of greater or less severity according to the susceptibility of the parenchyma at the time of its invasion. Similar symptoms have been observed in field plantings, and it is suggested that vascular infection is of greater and wider significance in the epidemiology of bacterial blight than has hitherto been commonly accepted.
THE SYSTEMIC ACTION AGAINST PSEUDOMONAS MEDICAGINIS VAR. PHASEOLICOLA OF A STREPTOMYCIN SPRAY APPLIED TO DWARF BEANS
Authors: NAPIER EUNICE J. , TURNER DOROTHY I. , RHODES A. , TOOTILL J. P. R.
Published: February 2008

The prophylactic effect resulting from the localized application of streptomycin as a foliage spray on dwarf bean plants has been examined. Streptomycin sulphate solution applied to the primary leaves exhibited a marked and consistent systemic, antibacterial, prophylactic action even at sites as far removed from the point of application as the fourth trifoliate leaf. This systemic protection against the halo blight organism persisted for various periods up to a maximum of 11 days. Mannosidostreptomycin was much inferior to streptomycin in its systemic prophylactic action against halo blight.
A METHOD FOR OBTAINING A CONTROLLED DAILY TEMPERATURE CYCLE
Authors: HOWE R. W.
Published: February 2008

An apparatus is described which gives a controlled daily cycle of temperature. The hand of a 24 hr. clock is connected by a rod to the arm operating a thermostat contact and moves the contact slowly backwards and forwards. Its method of use is described and the shape of curve it produces is expressed as a mathematical formula. A method of obtaining a nearly constant relative humidity is described.
FACTORS AFFECTING THE PATHOGENICITY OF BACTERIA TO POTATO TUBERS. I
Authors: MURANT A. F. , WOOD R. K. S.
Published: February 2008

An isolate of Erwinia aroideae caused much more rotting of potato tubers than did isolates of Pseudomonas sp., Flavobacterium sp., and Pseudomonas syringae; filtrates from cultures of each of the bacteria in potato extract had about the same macerating activity.

Pseudomonas sp. and P. syringae, but not Erwinia aroideae or Flavobacterium sp., were agglutinated in three different types of potato extract at the normal pH of potato tubers.

Measurements of growth by turbidity and total count methods were compared. In undisturbed potato sap, Erwinia aroideae had grown much more after 12 hr. than had Flavobacterim sp. and Pseudomonas syringae. Erwinia aroideae also grew more rapidly than Pseudomonas sp., but in this case the difference was caused largely by a longer lag phase.

The two species of Pseudomonas grew far less rapidly in potato sap cultures shaken hourly than in undisturbed cultures. Erwinia aroideae grew slightly more rapidly in disturbed culture. Measured by the total count method, growth of Flavobacterium sp. was better in undisturbed cultures, but the opposite result was obtained when growth was measured turbidimetrically.

With a small inoculum, growth of Erwinia aroideae and of Pseudomonas sp. was delayed by as much as 3 days in potato sap sterilized by heat. This effect was not obtained with an inoculum twenty times bigger, with potato extract, or with sap sterilized by filtration.

Potato sap reduced the macerating activity of preparations from each bacterium; oxidation of the sap had no further effect. Production of macerating enzymes by Flavobacterium sp. and Pseudomonas syringae, but not by Erwinia aroideae and Pseudomonas sp., was less in potato sap than in potato extract. Erwinia aroideae secreted macerating enzymes into potato sap much more rapidly during the first 12 hr. of growth than did Pseudomonas sp.

The activities of filtrates from cultures of Erwinia aroideae and Pseudomonas sp. were higher at the pH of the culture at the time of sampling than at higher and lower values.

The addition of CaCO3 to media apparently increased the pH optimum for macerating activity of Erwinia aroideae and, to a lesser extent, Pseudomonas sp. preparations.

There was little difference in the toxicity of preparations of similar macerating activity from cultures of the four organisms.
MOULTING RHYTHM IN THE ALIENICOLAE OF APHIS FABAE SCOP. (HEMIPTERA: APHIDIDAE) IN THE FIELD
Authors: JOHNSON C. G. , HAINE E. , COCKBAIN A. J. , TAYLOR L. R.
Published: February 2008

In a natural population of alienicolae of Aphis fabae Scop, on field beans in July 1952, the frequency of moulting of the last larval instar into the alate form was usually relatively high between about 04.00 and 08.00 hr. G. M. T. This high rate was followed by a decline to a lower fluctuating rate for the rest of the day. The moulting rate at night was usually very low.

The high rate of moulting in the morning, just as the temperature is rising, may be due to acceleration of nymphal development which leads to a synchronization of moulting, much as teneral development of alatae, if accelerated, produces flight peaks during the day (Johnson, Taylor & Haine 1957): data on the relations of moulting and nymphal development to temperature are, however, insufficient for making a complete analysis along these lines.

Changes in moulting rate during the rest of the day are correlated with temperature and with time, both independently. A rise of 1°C. ambient temperature is associated with an 11.6% rise in moulting rate: a fall of 1°C. with a drop of 10.5% and a lapse of 1 hr. in time by a 5.4% drop in the rate. Sunshine and humidity show no simple correlation with moulting rate.
THE PRODUCTION OF ANTIBIOTICS IN SOIL V. BREAKDOWN OF GRISEOFULVIN IN SOIL
Authors: WRIGHT JOYCE M. , GROVE JOHN FREDERICK
Published: February 2008

When griseofulvin (I; R= Cl, R′= OCH3), a chlorine‐containing antibiotic produced by Penicillium nigricans, was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, a Pseudomonas sp., increased in the soil steadily after adding griseofulvin.

When a little soil was added to a solution (pH 7·0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as the Pseudomonas sp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5·0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown.

The Pseudomonas sp. also degraded two derivatives of griseofulvin, dechlorogriseofulvin (I; R= H, R′= OCH3) and the amine (I; R= Cl, R′= NH2). Cl– was detected in the solutions after breakdown of griseofulvin by the Pseudomonas; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl–. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the liberation of Cl‐.
THE PROPERTIES OF TOMATO ASPERMY VIRUS AND ITS RELATIONSHIP WITH CUCUMBER MOSAIC VIRUS*
Authors: GOVIER D. A.
Published: February 2008

Chrysanthemum plants infected with tomato aspermy virus (TAV) produce severely distorted and discoloured flowers but show only slight leaf mottle.

TAV infected twenty‐five of forty‐five species (belonging to seventeen genera) tested and was transmitted by the aphid species Aulacorthum solarti, Macrosiphoniella sanborni and Myzus persicae.

Sap from infected tobacco leaves lost infectivity when diluted more than 1 in 10,000, when heated for 10 min. at above 65°C. and when stored for more than 42 hr. at 16–18°C.

Partial protection was obtained between TAV and two strains of cucumber mosaic virus. Evidence was obtained that this was true protection between related viruses and serological tests confirmed the view that TAV is a strain of cucumber mosaic virus. Evidence was obtained that this was true protection between related viruses and serological tests confirmed the view that TAV is a strain of cucumber mosaic virus.
THE LINE‐PATTERN VIRUS DISEASE OF PLUMS
Authors: POSNETTE A. F. , ELLENBERGER CHRISTINA E.
Published: February 2008

The disease, now usually called line‐pattern of plum, has been described under many names in most countries where plums are grown extensively.

Naturally infected trees show widely differing Symptoms; this has two causes: (1) different varieties react differently to the same isolate of the virus, and (2) different isolates cause different symptoms in the same variety. Because the virus occurs in strains with different pathogenicities, the choice of indicator varieties is important when selecting virus‐free material by transmission tests. Peach seedlings and the mazzard clone, F 12/1, were the most sensitive types found.

The line‐pattern virus does not become fully systemic in some varieties of plum. In this and other respects, it resembles the viruses that cause apple mosaic; three isolates obtained from plum and two from apple produced similar Symptoms in peach and apple. It is therefore suggested that plum line‐pattern and apple mosaic viruses are caused by strains of one virus.
OBSERVATIONS AND EXPERIMENTS ON THE HESSIAN FLY (MAYETIOLA DESTRUCTOR SAY)
Authors: STOKES BARBARA M.
Published: February 2008

Experiments showed that a stem midge collected locally on couch grass (Agropyron repens) and similar midges collected on wheat, barley and rye were of the same species, i. e. the hessian fly, Mayetiola destructor Say. There were three main flights per year, with some overlapping of the generations. In experiments, Aegilops ovata, Triticum compactum, T. dicoccoides, T. durum, T. spelta and T. turgidum were successfully used as host plants besides wheat, barley, rye and couch grass. Individual female midges when moved from plant to plant gave rise to families on the different host plants; similarly, succeeding generations of midges were able to breed on various host plants other than those from which they themselves were reared. Oviposition also took place on plants on which larvae failed to establish themselves.

Wheat seemed more favourable for the hessian fly than couch grass, and more midges were reared from young plants than from mature ones.

Unisexual families occurred in about half the experiments. The following parasites were bred: Trichacis didas Walker, Eupteromalus? hemipterus Walker, Platygaster sp., Chrysocharis sp. and Tetrastichus sp.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES XI. AUXIN ANTAGONISM IN RELATION TO A THEORY ON MODE OF ACTION OF ARYL‐ AND ARYLOXY‐ALKANECARBOXYLIC ACIDS
Authors: WAIN R. L. , WIGHTMAN F.
Published: February 2008

A study has been made of the antagonistic effects of a range of phenoxy and other acids on the growth‐promoting activity of a number of auxins as assessed by the Avena cylinder and pea curvature tests. The compounds examined as inhibitors were selected on a logical basis, these molecules not possessing the structural requirements considered necessary for growth‐regulating activity, yet possessing groupings which might allow them to accumulate at a site of action from which the growth response by auxins might be initiated. Our previous demonstrations that inactive stereoisomers of x‐aryloxy propionic acids can competitively inhibit the activity of their active enantiomorph has been confirmed and a similar antagonism has been found to operate with other inactive aryloxy acids. Such competitive antagonism is discussed in relation to a ‘three‐point’ contact theory on mode of action.
PARTICLE SIZE OF INSECTICIDAL SUSPENSIONS AND THEIR CONTACT TOXICITY VI. EFFECT OF TEMPERATURE ON RELATIVE TOXICITY
Authors: McINTOSH A. H.
Published: February 2008

Two aqueous suspensions, one containing crystals of uniform size and the other containing colloidal particles, were made with each of seven solid contact poisons (two DDT‐analogues, DDT, rotenone, 2‐bromomercurithiophen, dieldrin and endrin). The relative toxicity of each pair of suspensions was found in dipping or measured‐drop tests on as many as possible of the species Oryzaephilus surinamensis L., Tribolium castaneum Herbst and Tenebrio molitor L. In addition, some tests were made by injection of colloidal suspensions.

In each test, insects were kept after treatment at two temperatures: 28°C. and 11, 17 or 20°C.; counts of kill were made after 24 hr. The tests measured three different kinds of temperature coefficient of insecticidal action.

In the contact tests, the colloid was nearly always more toxic than the crystals. In all the tests, except those with dieldrin, the relative toxicity (colloid: crystals) was greater at the lower after‐treatment temperature, i. e. the temperature coeficient of the relative toxicity was negative. But in the case of dieldrin, the coefficient was positive.

The DDT‐analogues, DDT, rotenone and endrin were more toxic at the lower after‐treatment temperature, i. e. they had negative temperature coefficients of kill by contact action. In all these cases the temperature coefficient of kill by contact action was greater for colloid than for crystals. Dieldrin and 2‐bromomercurithiophen had positive temperature coefficients of kill by contact action. With dieldrin, the temperature coefficient was greater for colloid than for crystals; but with 2‐bromomercurithiophen, the reverse was true.

The temperature coefficient of kill by injection was negative for DDT, but positive for dieldrin and endrin; the other poisons were not tested by injection.

A possible explanation for the results of the contact tests is given in an Appendix. The explanation is based on a number of assumptions about the penetration of insect cuticle by solid poisons. These assumptions lead to the conclusion that the effect of temperature on the relative toxicity depends on the temperature coefficient of kill by internal action of the poison on the insect. This can be measured by injection tests. If it is negative or zero, the ratio of toxicities (colloid: crystals) by contact action, measured quite soon after treatment of the insects, will be greater at a low temperature after treatment than at a high temperature after treatment; but if the coefficient is positive, the effect of temperature on relative toxicity cannot be foretold. The experimental results seem to confirm the assumptions.
THE STIMULATORY PROPERTIES OF SOME ORGANIC SUBSTANCES ON CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHMIDT
Authors: WALLACE H. R.
Published: February 2008

Techniques for determining the influence of various substances on the rate of larval emergence from cysts of the beet eelworm are described. There is no significant difference between the rates of larval emergence in glutamic acid, galactinol, inositol and water; the rate of larval emergence in beet diffusate, on the other hand, was significantly higher. Studies of larval emergence in carbohydrates suggest that the cyst population used in the experiments was heterogeneous, consisting of two types of cyst which have different reactions to stimulation at different concentrations. The significance of root exudates in relation to beet eelworm is discussed.
THE DEVELOPMENT OF POTATO SKIN‐SPOT DISEASE
Authors: ALLEN J. D.
Published: February 2008

A study of the development of skin spot in the potato variety Kerr's Pink has shown that humid conditions, both before and after infection by Oospora pustulans, increase the incidence of the disease. The results of inoculation experiments have indicated that infection of the tuber does not take place much before the normal time of lifting.

It has been found that the pathogen may enter the tuber by way of the lenticels, and that invasion of the cortex and the production of a cork cambium takes place shortly after infection. Some damage to buds was observed within 16 days of inoculation. Although the affected pocket of cortical tissue soon dies, discoloration of the periderm is not apparent until much later. It is suggested that this may be the reason for the comparatively long period which elapses between infection and the appearance of skin‐spot symptoms.
PHYSIOLOGIC RACES OF PHYTOPHTHORA INFESTANS (MONT.) DE BARY IN NORTHERN IRELAND*
Authors: DOLING D. A.
Published: February 2008

By using the detached‐leaf technique and Black's series of differential host varieties, seven physiologic races of Phytophthora infestans (Mont.) de Bary have been distinguished as occurring in Northern Ireland. Six were found at the Dunanney potato variety trial plots, namely: race 1; race 2; race 4; race I, 2; race 1,4; and race I, z, 4. The remaining race, race 0, was isolated from the commercial potato crop.

In a survey, comprising seventy‐three isolates, of the physiologic races occurring in the commercial potato crop, only race o and race 4 were found (3 and 70 isolates respectively).

Certain modifications to the detached‐leaf technique have given improved results, including the formation of normal lesions and the elimination of atypical infections showing sparse sporulation.

The variation in the host‐parasite reaction of the detached leaves and the identity of the common race in commercial potato crops are discussed.
THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM ROT OF TOMATOES PART I. GLASSHOUSE EXPERIMENTS
Authors: WILLIAMS P. H. , HACK JUDITH
Published: February 2008

When tomatoes were planted in steamed soil inoculated with spores of Didymella lycopersici Kleb., a large proportion became infected, but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro‐organisms before inoculation with D. lycopersici reduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion of D. lycopersici spores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants. Steamed soil remained susceptible to infection by D. lycopersici for 4 months. D. lycopersici survived in a glasshouse soil over the winter, but the number of diseased plants was small. Cultivation may lessen the amount of disease by burying most of the infected surface layers of the soil. The peak of infection under glass occurred in May. The amount of disease and the yield were correlated, but with severe infection the yield varied with the time of infection and the distribution of diseased plants.
THE EFFECT OF INFECTION WITH TOBACCO ETCH VIRUS ON THE RATES OF RESPIRATION AND PHOTOSYNTHESIS OF TOBACCO LEAVES
Authors: OWEN P. C.
Published: February 2008

Unlike tobacco mosaic virus, which increases the respiration of tobacco leaves within an hour of their being inoculated, a virulent strain of tobacco etch virus did not change respiration rates until leaves showed external symptoms. The respiration rates of inoculated or systemically infected leaves with symptoms rose to 40% above that of healthy leaves, three times the increase produced by tobacco mosaic virus. The increased respiration rate occurred at all times of the year and was maintained through the life of the leaves.

Leaves infected with tobacco etch virus and showing symptoms had a photo‐synthetic rate 20% lower than that of healthy leaves.
THE EFFECTS OF INFECTION WITH TOBACCO MOSAIC VIRUS ON THE PHOTOSYNTHESIS OF TOBACCO LEAVES
Authors: OWEN P. C.
Published: February 2008

The rate of photosynthesis of tobacco leaves infected with the Rothamsted type culture of tobacco mosaic virus was lower than that of comparable healthy tobacco leaves. The lower rate was inferred from Net Assimilation Rates of whole plants and confirmed by direct comparisons of photosynthetic rates of inoculated and healthy leaves. The effect began within 1 hr. of inoculation. It was not caused by an effect of the virus on the stomata, and inactivated virus inoculum did not change the rates. The results indicate either a more rapid movement of virus from the epidermis into the chlorenchyma than has been previously recorded or an effect of virus infection at a site distant from the cells containing virus.
STUDIES ON THE HOST RANGE, PROPERTIES AND MODE OF TRANSMISSION OF BEET RINGSPOT VIRUS
Authors: HARRISON B. D.
Published: February 2008

An apparently undescribed mechanically transmissible virus has been named beet ringspot virus (BRV). It occurs naturally in Scotland in sugar‐beet, turnip, swede, potato and many kinds of weed plants. BRV is readily distinguished from raspberry ringspot virus by the symptoms produced in Chenopodium amaranticolor, French bean, tobacco and Petunia hybrida plants. BRV lost infectivity when heated for 10 min. at 63°C. but not at 60°C.: at 20°C. its longevity in vitro was about 3 weeks. BRV was precipitated by ammonium sulphate, ethanol and acetone.

Protection experiments with tobacco plants, and serological tests, gave no evidence that BRV was related to tobacco ringspot, raspberry ringspot, potato bouquet or tobacco rattle viruses, but showed that viruses isolated from different host plants and from different localities were strains of BRV.

BRV is soil‐borne: in glasshouse experiments sugar‐beet, beetroot, potato, turnip, swede, French bean, Fragaria vesca, oat and wheat plants often became systemically infected when grown in soil from the site of a disease outbreak, but the virus was restricted to the roots of many infected plants. When sugar‐beet seedlings were grown in virus‐containing soil, BRV was first detected in their roots, where its concentration increased, before progressively increasing amounts of virus were found in the shoots.

Soils from five localities were found to contain BRV. BRV has been found only where the soil is light in texture, and often in fields where raspberry ringspot virus occurs.
THE EFFECT OF MCPA AND 2:4‐D HERBICIDES ON THE QUALITY OF SPRING OATS FOR MILLING AND PROVENDER FEEDING
Authors: KENT N. L. , HUTCHINSON J. B.
Published: February 2008

MCPA applied to oats at the 1‐ to 2‐leaf stage had slight effects on grain quality, whereas 2:4‐D at this stage generally increased kernel weight, husk ash content, and content of abnormal grains, and decreased the grain yield. Applied at the 4‐ to 5‐leaf stage, 2:4‐D also increased kernel nitrogen content and decreased kernel oil content. Effects were enhanced as the dosage increased. Yielder and Craigs Afterlea were most susceptible to 2:4‐D at the 4‐ to 5‐leaf stage; Sun II, a relatively resistant variety, at the 6‐ to 7‐leaf stage.
THE GROWTH OF BOTRYTIS CINEREA PERS., FUSARIUM CAERULEUM (LIB.) SACC., AND PHOMA FOVEATA FOISTER IN THE PRESENCE OF TETRACHLORONITROBENZENE ISOMERS
Authors: BROOK M. , CHESTERS C. G. C.
Published: February 2008

The linear growth of Botrytis cinerea, Fusarium caeruleum and Phoma foveata in culture was reduced in the presence of vapour from any of the three isomers of tetrachloronitrobenzene. The isomers were fungistatic but not fungicidal.

Differences in activity were observed amongst the isomers. The 2:3:4:6 isomer was the most active against all three test fungi. 2:3:5:6‐TCNB (tecnazene) was more active than 2:3:4:5‐TCNB against Botrytis cinerea, but less active against Fusarium caeruleum and Phoma foveata. Two strains of Fusarium caeruleum resistant to the 2:3:5:6 isomer were not resistant to the other two isomers, although they were more resistant than their 2:3:5:6‐TCNB sensitive parent strains.

Sporulation and sclerotial production by Botrytis cinerea were completely suppressed by 2:3:5:6‐TCNB and 2:3:4:6‐TCNB but not by the 2:3:4:5: isomer.
THE EFFECTS OF NITROGEN SUPPLY UPON THE VERTICILLIUM WILT OF ANTIRRHINUM
Authors: ISAAC IVOR
Published: February 2008

Isolates of Verticillium albo‐atrum, V. dahliae and V. nigrescens grown on media adequately supplied with sodium nitrate induced wilt rather more rapidly in antirrhinum plants growing in soils with a normal and an excessive amount of nitrogen than in plants in nitrogen‐deficient soil, though plants became diseased in all soils. Similarly treated isolates of V. nubilum and V. tricorpus induced a greater incidence of wilt in plants in soil supplied with heavy dressings of organic nitrogenous fertilizer than in plants in soil deficient in nitrogen, although V. tricorpus from a medium containing much sodium nitrate, in contrast to V. nubilum, was pathogenic to plants in such deficient soil. The ability of the nitrogen‐starved isolates to penetrate the host plant was significantly diminished, and even when wound‐inoculated into stems their effect upon the host was much reduced.
SOME CONTROL MEASURES FOR ANTHRACNOSE DISEASE OF TOBACCO*
Authors: COLE J. S.
Published: February 2008

Laboratory, greenhouse and seed‐bed trials of copper and organic fungicides for the control of Colletotrichum tabacum on tobacco were made in Southern Rhodesia. In the seed‐bed trials the best control was obtained by sprays of maneb, thiram, zineb and captan. During the hot, dry weather in the early part of the season little damage was caused by the disease and it was easier to control than later, when rain and overcast weather were more frequent. Mixtures of zineb and copper compounds gave better control than either component alone.

When seed‐beds were covered with light cloth for shade, they suffered greater damage from the disease than when a thin grass mulch was used.
A TECHNIQUE FOR EXAMINING SOIL FOR THE PRESENCE OF PLASMODIOPHORA BRASSICAE WORON
Authors: COLHOUN JOHN
Published: February 2008

A technique based on growing plants under controlled conditions in a glasshouse has been evolved which demonstrates within a minimum period of 5 weeks whether or not a given area of land is contaminated with Plasmodiophora brassicae. The technique also facilitates estimation of the degree to which a soil sample is contaminated.
SOME HISTOLOGICAL OBSERVATIONS ON VIRUS‐INFECTED THEOBROMA CACAO L.
Authors: KNIGHT R. , TINSLEY T. W.
Published: February 2008

Although the five cacao viruses studied produce different external symptoms in infected plants, they affect internal anatomy similarly. Symptoms on leaves occur only if these are still developing when they become infected, and the viruses seem to produce their effects usually by preventing differentiation of the cells. The tissues of chlorotic areas of infected leaves are undifferentiated and similar in structure to young unexpanded leaves. In stem and root swellings xylem and phloem are both increased, but they occur in the same proportions as in normal secondary thickening. The anatomical effects of infection seem insufficient alone to account for the death of cacao trees, but they may well be complementary to the serious necrosis of the root system which results from virus infections.
THE REACTION OF WHEAT VARIETIES TO LOOSE SMUT AS DETERMINED BY EMBRYO, SEEDLING, AND ADULT PLANT TESTS
Authors: BATTS C. C. V. , JEATER ANN
Published: February 2008

The possibility of using an embryo test as a means of determining the reaction of wheat varieties to loose smut (Ustilago tritici (Pers.) Rostr.) has been investigated. Fifty‐seven varieties were inoculated with two physiologic races by the partial vacuum method and the embryos, seedlings, and adult plants were examined for infection. Most of the varieties were fully susceptible to one or both races, and only ten showed real resistance to any one race. Braun R and Molinel proved almost immune to infection. The resistance in other varieties which showed no infection in the field was expressed as embryo susceptibility, i.e. the embryo became infected in much the same way as in field‐susceptible varieties.

In the latter varieties infection passes from the embryo into the growing point of the young seedling. In the embryo‐susceptible field‐resistant varieties, infection does not pass from the scutellum and the growing point is therefore uninfected.

The reaction of most of the varieties tested was straightforward resistance or susceptibility, but in a few varieties a small proportion of the grains reacted differently from the majority. These reactions are discussed.
THE CHEMOTHERAPEUTIC EFFECT OF PYRIDINE‐2‐THIOL‐N‐OXIDE AND SOME OF ITS DERIVATIVES ON CERTAIN PLANT DISEASES
Authors: ROMBOUTS J. E. , SIJPESTEIJN ANTJE KAARS
Published: February 2008

Limited systemic protection of broad bean against Botrytis fabae and of cucumber against Cladosporium cucumerinum has been observed as a result of the application of pyridine‐2‐thiol‐N‐oxide and its carboxymethyl derivative. Apparently this protection is, to some extent, the result of translocation of the chemicals in the plants. It was found that the vapour phase of pyridine‐2‐thiol‐N‐oxide plays an additional role in the chemotherapeutic activity. There is no evidence that the copper chelate of pyridine‐2‐thiol‐N‐oxide is translocatable in plants. Root applications of these three compounds had no chemotherapeutic effect.
INTERPRETATION OF DOSAGE‐MORTALITY DATA FOR DDT‐RESISTANT HOUSEFLIES
Authors: HEWLETT P. S.
Published: February 2008

The slopes of the lines relating probit mortality to the log.‐dose of DDT are generally lower for resistant than for susceptible strains of houseflies. Two effects that could each account for this are discussed. The first concerns the relation of the amount of DDT absorbed to the dose; the conditions under which it would occur are stated, and published data on the absorption are analysed. The second concerns the variability from fly to fly of the amount of DDT exerting a toxic effect at the primary site of action, a variability that would seem to be brought about, or greatly intensified, by the enzymatic detoxification of DDT in resistant flies. Both mechanisms may occur, reinforcing one another.
AN APPARATUS FOR SCREENING COMPOUNDS FOR REPELLENCY TO FLIES AND MOSQUITOES
Authors: BOVINGDON H. H. S.
Published: February 2008

An apparatus for determining the repellency of a chemical compound is described. Its action depends upon the insects' coming into contact with the compound deposited on a glass surface. The numbers of insects settling on treated and untreated glass plates at intervals over a period of 40 min. and under conditions that minimize varying disturbing factors are counted. The quotient obtained by dividing the total numbers on the untreated plates by the total numbers on the treated plates is called the ‘repellence quotient’, and must reach certain given values before significance is assumed and a compound is regarded as repellent.

Typical results obtained with the apparatus are given and include the detailed determination of the repellency of butoxypolypropylene glycol (MW 800).
MOVEMENT OF EELWORMS
Authors: WALLACE H. R.
Published: February 2008

Experiments on vertical migration through saturated soil fractions, horizontal migration through soil fractions at different pressure deficiencies and migration in single layers of particles showed that the beet eelworm, Heterodera schachtii Schmidt, attained maximum speed when the pore diameters were between 30–60 μ. Speed of the eelworms increased as lateral displacement of the body was restricted by external resistances acting perpendicularly to the body axis; at the maximum speed there was no lateral movement, each part of the body following the part immediately in front of it. The speed of beet eelworm larvae in water films of various thickness was measured; maximum speed occurred in a film 2–5 μ thick. Four arbitrarily classified types of progression were observed in the pore spaces. It is suggested that the ‘moisture characteristic’ supplies most of the information required about the physical properties of the soil in relation to eelworm movement. By examining such a curve the pore size distribution can be ascertained and the probable behaviour of beet eelworm larvae in the medium predicted.
MOVEMENT OF EELWORMS
Authors: WALLACE H. R.
Published: February 2008

Studies of mobility in horizontal tubes containing different soil fractions at different suctions and in single layers of particles, showed that the optimum particle size for movement of Heterodera schachtii and Ditylenchus dipsaci was 150–250 and 250–500 μ, respectively. In both species mobility was greatest when (a) there were few pores smaller in diameter than the eelworm width, (b) the pore diameter was narrow enough to restrict lateral movement, (c) the tortuosity of the channels between particles was such that the body form of the eelworm had waves of long wave‐length and short amplitude. By plotting tracks among water droplets it was possible to show quantitatively the relationship between the form of the body waves and the speed of the eelworms. The optimum temperature for movement was 15°C. for H. schachtii and 15–20°C. for D. dipsaci. The comparative study suggested that there was a simple relationship between body length, particle size and speed.
SOME EFFECTS OF VIRUS INFECTION ON LEAF WATER CONTENTS OF NICOTIANA SPECIES
Authors: OWEN P. C.
Published: February 2008

Infection with tobacco mosaic virus decreases the water content which detached tobacco leaves attain when kept for 20 hr. in conditions of minimum water stress, and does so more when the plants are kept in light before inoculation than when they are kept in darkness. No such effects of infection during the first day after inoculation were obtained with tobacco leaves infected with either tobacco etch virus or potato virus X, or with Nicotiana glutinosa leaves infected with tobacco mosaic virus. These results, like those showing early effects of TMV on respiration and photosynthesis of tobacco leaves, suggest that inoculation with TMV affects deeper leaf tissues than the epidermis earlier in tobacco leaves than in other leaves, and earlier than other viruses in tobacco leaves.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Authors: HEACOCK R. A. , WAIN R. L. , WIGHTMAN F.
Published: February 2008

A number of polycyclic carboxylic acids have been prepared and their plant growth‐regulating activity has been assessed in the wheat‐cylinder, pea‐curvature and pea‐segment tests. The compounds were selected in relation to a theory on the mode of action of plant‐growth substances which involves the association of three essential groupings in the molecule with specifically sited receptor centres within the plant cell. High activity was found only in those compounds possessing a > CHCOOH grouping adjacent to an aromatic ring. It is concluded that molecular size, stereochemical and electronic considerations may all operate in determining whether compounds of this type show activity. The results obtained together with those of other workers are discussed in relation to current theories on mode of action.
STUDIES UPON THE COPPER FUNGICIDES
Authors: ARMAN PAMELA , WAIN R. L.
Published: February 2008

Evidence is presented for the presence, on apple and dwarf bean leaves, of substances which can dissolve copper from dried Bordeaux deposit. The solution of copper is not associated with the bacterial breakdown of these substances. Copper was dissolved by the action of apparently uninjured as well as injured leaves and it is concluded that copper‐dissolving substances are liberated from intact leaf surfaces. The capacity of leaves to dissolve copper from dried Bordeaux deposit was not lost by repeated washing of the leaf. This further evidence of the sustained activity of the host plant in bringing copper into solution emphasizes the importance of host action in relation to the fungicidal and phytotoxic action of Bordeaux mixture under field conditions.
STUDIES ON PLANT CUTICLE
Authors: MARTIN J. T. , BATT R. F.
Published: February 2008

The waxy coverings of the leaves of different species of plant have been fractionated into wax, acidic, volatile and oil components. The levels of the waxy deposits on the leaves and the relative proportions of the principal components of the waxy coverings differed widely. Wax predominated in the waxy coverings of the leaves of cabbage and cauliflower and acidic materials in those of apple and pear.

The role of ether‐soluble acidic constituents in a possible defensive mechanism of leaves against fungi, the contribution of water‐soluble acidic constituents to the toxic action of copper fungicides and the influence of the waxy covering on spray deposition, phytotoxicity and the behaviour of DDT deposits on leaves are discussed. Earlier work on the nature of leaf wax components is reviewed.