bluuebunny/crossref_metadata_2025 huggingface dataset:
CROOK ROOT OF WATERCRESS
Authors: TOMLINSON J. A.
Published: February 2008

Zinc, used as zinc sulphate at 0.5 p.p.m., was found to inhibit the growth of Spongospora subterranea (Wallr.) Lagerh., f.sp. nasturtii Tomlinson, the cause of crook‐root disease of watercress. A relatively insoluble finely powdered glass frit containing zinc oxide (zinc frit) largely prevented infection by this fungus when added, at 0.2 g./350 ml., to water in which watercress was growing.

In field trials made in 1955‐56 on brown watercress at Bere Regis, Dorset, and on green watercress at Greatford, Lincolnshire, zinc frit was applied at two rates of 1 and 1/2 lb. per sq.yd. After 4–8 weeks, plants in the treated beds grew more strongly and root infection was reduced considerably. Untreated control beds remained heavily infected from September to April but, in the treated beds, the disease was greatly reduced from November to January though, by April, this effect had largely disappeared. Disease control at both places was associated with increases in total crop and individual plant weight. Field trials in 1956‐57 gave similar results.

When zinc frit was shaken with distilled water for 24 hr. a solution containing 0.21 p.p.m. zinc was obtained, but if watercress plants had been grown in the water before it was shaken with the frit the solution contained 2.82 p.p.m. zinc. The treated water was found to contain 16 p.p.m. CO2 which had a solvent action on the frit. Field tests showed that plants in watercress beds liberated sufficient CO2 into the water to bring into solution a fungitoxic concentration of zinc. Observations on the crook‐root fungus showed that the suppression of the disease by zinc was caused by the killing of the zoospores.

The zinc content of watercress in beds treated with zinc frit was at a safe level for human consumption and the zinc content of the outflow water from such beds was non‐toxic to trout (Salmo gairdnerii Richardson).

A previous theory on the release of metals from glass by plants is discussed in relation to the experiments described on the release of zinc from zinc frit.
SOME FACTORS AFFECTING THE OCCURRENCE AND DEVELOPMENT IN POTATOES OF GANGRENE CAUSED BY PHOMA SOLANICOLA PRILL. & DELACR.
Authors: MALCOLMSON JEAN F.
Published: February 2008

It is shown that gangrene is a soil‐ and haulm‐borne disease and that infection of the tubers can take place through cuts, bruises, ‘eyes’ and lenticels. Low temperature and dry, dark storage were found to be most favourable to development of the disease, but rotting was more severe if the tubers had been kept at a higher temperature before infection took place. Storage at 21° C. for 10 days was sufficient to arrest rotting. Gangrene developed on all the potato varieties tested, but different varieties showed differences in susceptibility to the disease. No difference was observed in the susceptibility of early and late varieties but susceptibility increased with advancing maturity of the tubers.
INVESTIGATIONS ON FUNGICIDES
Authors: FAWCETT C. H. , SPENCER D. M. , WAIN R. L.
Published: February 2008

Twenty (aryloxythio)trichloromethanes were examined for in vitro fungicidal activity against six fungi. All compounds showed a direct fungistatic effect and some exhibited a marked fumigant action. Good protectant action against Alternaria solani on tomato and Botrytis fabae on broad bean was obtained with certain compounds, but none was better than the three standard protectants used for comparison. When supplied to plants through their roots, eight conferred significant systemic fungicidal protection against Alternaria solani in tomato, but there was no significant protection against Botrytis fabae in broad bean. In preliminary tests the 2:4:5‐trichlorophenoxythio analogue gave promising results when examined as a fumigant fungicide for eradication of downy mildew in lettuce plants, for reducing lenticel rot in stored apples and for preventing blue‐mould in oranges.
THE DEFINITION AND CLASSIFICATION OF ABNORMALITIES OF FRUIT PIGMENTATION IN THE TOMATO VARIETY ‘POTENTATE’
Authors: COOPER A. J.
Published: February 2008

The need for a detailed classification of the pigmentation abnormalities that occur during the ripening of tomato fruits is discussed and a possible classification is presented. The amounts of the different types of pigmentation abnormality occurring show large annual differences and pronounced short‐term fluctuations in any one season.
THE ADAPTATION OF FUNGI TO FUNGICIDES: ADAPTATION TO THIRAM, ZIRAM, FERBAM, NABAM AND ZINEB
Authors: PARRY K. E. , WOOD R. K. S.
Published: February 2008

The concentrations of thiram preventing germination of spores of Botrytis cinerea in drops of a 1% solution of sucrose, and on the surface of a sucrose‐nitrate agar have been determined. Thiram had much less effect on germination in the agar medium, even when a purified agar was used. There was no growth on sucrose‐nitrate agar if the concentration of thiram exceeded 31 p.p.m. Attempts to obtain strains able to grow at higher concentrations were unsuccessful.

Similar results were obtained with ziram, nabam and zineb.

Ferbam also was more effective in preventing spore germination in spore drops than on agar media; this effect was obtained with ordinary and with purified agar.

On a sucrose‐nitrate agar generally there was no growth if the concentration of ferbam exceeded 125 p.p.m., but in one of forty‐eight plates containing 250 p.p.m. ferbam, five slowly growing colonies were produced, and from these colonies arose mycelium which grew and sporulated rapidly on 500 p.p.m. ferbam agar. Agar disk inocula were transferred from these cultures to agar containing higher concentrations of ferbam and in this way, and by repeating the process, a strain was obtained which grew slowly but continuously, and sporulated on agar containing 5000 p.p.m. ferbam. However, the poor solubility of this fungicide made it difficult to assess quantitatively the degree of adaptation.

A proportion of the spores from this strain germinated in drops containing about twice the concentration of ferbam which prevented germination of parent spores.

The resistance of the mycelium of the resistant strain was not lost after repeated subculture on fungicide‐free agar. The resistant strain was as susceptible as the parent strain to thiram, ziram, nabam and zineb.

Attempts to obtain strains of Venturia inaequalis resistant to thiram, ferbam, ziram and zineb were unsuccessful.
SAPROPHYTIC BEHAVIOUR OF SOME CEREAL ROOT‐ROT FUNGI: IV. SAPROPHYTIC SURVIVAL IN SOILS OF HIGH AND LOW FERTILITY
Authors: BUTLER F. C.
Published: February 2008

In southern New South Wales the resumption of ley land for wheat growing has been accompanied by an increase in take‐all (Ophiobolus graminis) and Fusarium root rot (Fusarium culmorum). No such increase has been observed in foot and root rots of wheat caused by Helminthosporium sativum and Curvularia ramosa.

It is shown experimentally that these differences are related to the relative capacity of the causal fungi to persist in wheat straw buried in each of two unsterilized soils which, because of past cultural treatments, differed in their organic carbon and total nitrogen content. While the saprophytic survival of O. graminis and F. culmorum was promoted by high soil fertility that of H. sativum was markedly depressed. The survival of C. ramosa was little affected by soil fertility.

F. culmorum, H. sativum and C. ramosa each remained viable under the soil conditions best suited to their survival in one‐third to one‐half of the test straws for 2 years but O. graminis was not recovered after the 52nd week of sampling.
THE EFFECT OF INORGANIC MANURES, MOISTURE AND INOCULUM ON THE INCIDENCE OF ROOT DISEASE CAUSED BY RHIZOCTONIA SOLANI KUHN IN CULTIVATED SOIL
Authors: DAS A. C. , WESTERN J. H.
Published: February 2008

An account is given of experiments designed to study the effect of inorganic manures, both singly and in combination, soil moisture and available inoculum on the development of root disease in glasshouse soils.

Growth of Rhizoctonia solani Kuhn in sterilized soil was increased by applications of balanced fertilizer, by moderate doses of potassium and by the highest rate of phosphates applied. It was decreased by the higher applications of nitrogen and the highest rate of potassium. In unsterilized soil growth was poor in all treatments.

Fresh weights of lettuce seedlings were increased by moderate applications of balanced fertilizer but decreased by the higher levels of this and of the individual ingredients. Most disease was found in the balanced (basic) and nitrogen series: potassium and phosphatic amendments had comparatively little effect.

Mycelium of R. solani grew best, and produced most disease, in the relatively drier soils. It was found to need a minimum supply of nutriment (food base) to establish itself in soil but high concentrations of inoculum reduced pathogenicity. Its survival in artificially inoculated soils was shown to be little affected by soil fertility.

A description is given of a method to demonstrate the persistence and rate of spread of a parasite under relatively natural conditions.
STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS: II. BACTERIAL LEAF BLIGHT DISEASE OF CASTOR (RICINUS COMMUNIS L.)
Authors: SABET K. A.
Published: February 2008

The bacterial disease of castor in the Sudan has been reinvestigated. Typically the disease symptoms are brown or black, round or angular lesions on leaves; occasionally the thin succulent branches are attacked, but not the vascular tissue.

The bacterium responsible for the disease was previously thought to be Pseudomonas solanacearum E.F.Sm. but comparative studies show that the Sudan species differs in pathogenicity and physiology from P. solanacearum. It closely resembles Xanthomonas ricinicola (Elliott) Dowson (=Bacterium ricini Yoshi and Takimoto) in characters, host range and pathogenic effects. In culture on solid media the growth of X. ricinicola is typically yellow, while that of the Sudan species is dirty white; but this difference is not considered sufficient to justify the establishment of a new species.

The author proposes the specific name ricini originally adopted by Archibald (1927) and Yoshi & Takimoto (1928), for the species of Xanthomonas causing the leaf blight disease of castor, and considers that the causal organism in the Sudan is an atypical strain of this species.
PHYSIOLOGICAL STUDIES ON THE VERTICILLIUM WILT DISEASE OF TOMATO
Authors: THRELFALL R. J.
Published: February 2008

The water loss per unit leaf area of tomato plants was decreased after inoculation with Verticillium albo‐atrum. When diseased plants began to wilt water loss temporarily increased, but then rapidly decreased to become less than that of healthy plants grown under conditions of adequate or restricted water supply.

The transpiration of excised leaves from plants grown with a restricted water supply was reduced, but not so severely as that of comparable leaves from infected plants. Water loss from leaves on infected plants was reduced irrespective of any blocking of the petiolar xylem.

The rate of water loss from turgid leaf disks on mannitol solutions, and the rate of water uptake of leaf disks on water was similar for disks cut from wilting or turgid leaves of diseased plants or healthy plants grown with an adequate or restricted water supply.

Disease or poor water supply reduced leaf growth but had no effect on the rate of leaf initiation. Although the density of stomata was higher on leaves of diseased plants the stomatal area was less than on healthy plants.

The resistance to water flow in diseased stems was high and was correlated with vessel blockage. About half the blocked vessels contained hyphae. The severity and localization of symptoms in inoculated plants growing on susceptible or resistant rootstocks was directly related to the extent of invasion by the pathogen and to vessel blockage.

Experiments on the wilting activity of cell‐free filtrates from cultures of the pathogen in vitro indicated that it produced a stable substance, not an enzyme, that caused wilting in cut shoots by blocking the end of the stem. It is suggested that an increasing internal water shortage causes major symptoms of disease.
HOST RANGE STUDIES WITH FIFTY‐TWO PLANT VIRUSES
Authors: HOLLINGS M.
Published: February 2008

The reactions of fifteen plant species in families related to the Caryophyllaceae (Hutchinson's classification) when mechanically inoculated with sixty‐eight isolates of fifty‐two plant viruses are described. No general relationship could be detected between susceptibility to particular viruses and taxonomic relationships of the host plants. Some of the species were susceptible to many more viruses than were others.

Chenopodium amaranticolor, Gomphrena globosa and Tetragonia expansa were hosts for many viruses and their reactions make them suitable as standard test plants. Amaranthus caudatus, Celosia argentea, Beta vulgaris and Spinacia oleracea had limited use in diagnostic or quantitative work. Dianthus barbatus and Primula malacoides were convenient plants for maintaining stock cultures of some viruses. Phytolacca americana, Stellaria media, Fagopyrum esculentum and Plantago lanceolata had little use, and Portulaca oleracea and Lythrum salicaria were useless as test plants.

All fifteen species contained inhibitors of infection; these did not prevent infection on the fifteen species, but many did so in Solanaceous and Leguminous plants.

Systemic invasion in some hosts depended on such factors as temperature, virus concentration in the inoculum, virus strain and type of local lesion.

Strains of one virus often had different host ranges or caused different kinds of symptoms, while similar symptoms were sometimes caused by different viruses. But some viruses that caused similar symptoms on several of the test plants also shared other properties. Host‐range studies can be used to separate similar viruses or virus strains, and can suggest similarities between viruses for further study. But host‐range studies are unlikely to provide a useful basis for a natural classification of viruses.
THE FRIT FLY AND ALLIED STEM‐BORING DIPTERA IN WINTER WHEAT AND HOST GRASSES
Authors: JEPSON W. F. , HEARD A. J.
Published: February 2008

Sampling for stem‐boring larvae was undertaken in 1954‐56 on ley plots of Lolium perenne, Dactylis glomerata, Festuca arundinacea, F. rubra, Agrostis tenuis and Poa pratensis in randomized experiments at Hurley, Berks. The samples showed infestations by dipterous larvae, mainly species of Oscinella, Meromyza and Opomyza. The larvae showed preferences for specific grass hosts. More larvae were found where plots had been grazed throughout the season than where an early hay cut had preceded grazing. The total numbers of larvae varied between o and 688 per sq.yd. in November.

The larval populations of the leys were reflected in the populations in winter wheat which followed the plough‐up of the leys. Populations of up to sixty‐five larvae per sq.yd., mostly species of Oscinella, were found in the wheat in March. In 1956 a heavy larval infestation was associated with the death of considerable numbers of wheat plants.
EFFECTS OF PREVIOUS WHEAT CROPS, SEED‐RATE AND NITROGEN ON EYESPOT, TAKE‐ALL, WEEDS AND YIELDS OF TWO VARIETIES OF WINTER WHEAT: FIELD EXPERIMENT 1954‐56
Authors: GLYNNE MARY D. , SLOPE D. B.
Published: February 2008

In a replicated field experiment mean yields of wheat from plots that, in the preceding 2 years, had carried oats, beans or potatoes were 39.2 and 42.6 cwt. per acre in 1954 for Holdfast and Cappelle, respectively; 42.8 and 55.8 in 1955 and 34.9 and 49.6 in 1956. Previous wheat crops had more effect than any other treatment in increasing the incidence of eyespot, take‐all and weeds and in decreasing the number of ears per unit area and the yield of grain. In 1956 on plots carrying the first, second and third successive wheat crops the percentages of straws with eyespot were respectively 12, 54 and 42 and with take‐all 0.1, 1 and 16. Cappelle was less severely infected by eyespot than Holdfast. The second and third successive wheat crops yielded an average of 23.3 cwt./acre less than the first wheat crop. Cappelle consistently yielded more than Holdfast, the mean difference being 13.8 cwt./acre after potatoes but only 3.8 cwt./acre after two wheat crops. The higher seed‐rate gave an average increase in grain yield of 3.3 cwt./acre; but where eyespot and take‐all were both severe the lower seed‐rate yielded as much total and more dressed grain than the higher. Wheat given a spring top dressing of 6 cwt./acre Nitro‐Chalk yielded an average of 4 cwt./acre more grain than wheat given 3 cwt./acre.
GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE L.): IV. THE EFFECT OF NITROGEN, PHOSPHORUS AND POTASSIUM SUPPLY ON GROWTH DURING THE FIRST YEAR
Authors: LANGER R. H. M.
Published: February 2008

In a sand‐culture experiment lasting 21 weeks plants of timothy grown from seed were maintained at all combinations of three levels of nitrogen, phosphorus and potassium. The number and weight of tillers, leaves and ears, and the weight of roots, were determined at the end of the experiment, and for some of the treatments at intervals of 4 weeks. All three nutrients had significant effects, especially N which at its lowest level of supply tended to mask the effect of the other two elements. Potassium influenced tiller numbers least, especially those of primary tillers, but in the presence of high concentrations of N and P it had a large effect on leaf area and dry weight. Relative growth and net assimilation rates responded to varying nutrient supply only in the early stages of growth, so that in general variations in dry weight were associated with nutrient effects on leaf area.
THE DESTRUCTION OF DIDYMELLA LYCOPERSICI KLEB. IN TOMATO HAULM COMPOSTS
Authors: PHILLIPS D. H.
Published: February 2008

Experiments have been carried out to assess the possibility of the destruction by composting of mycelium of Didymella lycopersici in diseased tomato haulms. The results of laboratory trials with agar cultures and with infested tomato stems and fruits suggest that the fungus is destroyed if kept under moist conditions at 35° C. for from 3 to 6 days. Agar cultures buried for approximately this length of time in composting material at this or higher temperatures were dead when recovered. When composts made from haulms of tomatoes affected by Didymella stem rot were tested by placing them round the stem bases of tomato plants, or by growing tomato plants in them, few of the test plants became diseased. It was concluded that D. lycopersici present in tomato refuse could be destroyed by careful composting.
SOME PROPERTIES OF BARLEY STRIPE MOSAIC VIRUS*
Authors: KASSANIS B. , SLYKHUIS J. T.
Published: February 2008

Barley varieties differed greatly in their reactions to infection with barley stripe mosaic virus (BSMV) obtained from the variety Gloire du Velay growing in Cambridgeshire from seed imported from France. Lolium multiflorum Lam., previously considered immune, proved susceptible, as did Beta vulgaris L. and Chenopodium amaranticolor Coste & Reyn., which gave only local lesions, and Spinacea oleracea L. which became systemically infected.

Heating at 65° C. for 10 min. destroyed the infectivity and serological activity of BSMV. Sap was still infective after 32 days at 20° C., but lost its infectivity and half of its serological activity in 3 days at ‐ 20° C.; adding sugar to the sap prevented inactivation by freezing. The virus content of inoculated barley leaves increased most rapidly in plants kept at 24–28° C. At 24° C. increase was most rapid during the first 5 days, and the maximum virus concentration was reached about 10 days after inoculation. The highest infection end‐point of sap was 1/2048, when the precipitation end‐point with virus antisera was 1/256, and sap contained 1013 virus particles per ml.: the ratio of infectivity to serological activity and to number of virus particles is much smaller than with tobacco mosaic virus.

The rod‐shaped particles are about 20 mμ wide and, in fresh sap, most are between 135 and 175 mμ long. Various treatments, especially heating to 50° C, cause the particles to aggregate linearly. Preparations partially purified by alternate cycles of low‐ and high‐speed centrifugation and by precipitation with ammonium sulphate contain from 0.35 to 0.53% P, 12.3 to 13.2% N and 6.2 to 10.2% carbohydrate. Such preparations are insoluble in water but dissolve in borate buffer at pH 7.5: they inactivate below pH 4.5.
FACTORS AFFECTING THE SPREAD OF APHID‐BORNE VIRUSES IN POTATO IN EASTERN SCOTLAND: I. OVERWINTERING OF POTATO APHIDS, PARTICULARLY MYZUS PERSICAE (SULZER)
Authors: FISKEN A. G.
Published: February 2008

Three species of potato aphids, Myzus persicae (Sulzer), Macrosiphum euphorbiae (Thomas) and Aulacorthum solani (Kltb.), overwinter in eastern Scotland, primarily as apterae on perennial, glasshouse, frame and brassica crops. Brassica crops are the commonest hosts of overwintering Myzus persicae, the principal vector of potato leaf roll and Y viruses, and these crops are concentrated in the market‐gardening areas of the Lothians and Moray. Although crops of savoy cabbage and brussels sprout often carried numerous M.persicae during the winter, spring cabbage, cabbage for seed and broccoli seem the most important overwintering hosts because they usually persist until mid‐May, long enough to allow the development and dispersal of alatae to spring‐planted crops. Many alatae dispersed during July and August from crops colonized in spring. Although M. persicae overwintered as eggs on peach and viviparously on plants in glasshouses, the influence of such sites, which are generally distributed throughout the main seed‐potato growing areas of Angus, Perth and Fife, was local and unless numerous M. persicae survive the winter on weeds, the market‐garden area of the Lothians is probably the most important source from which this aphid disperses in spring and early summer to colonize potato crops in eastern Scotland.
FACTORS AFFECTING THE SPREAD OF APHID‐BORNE VIRUSES IN POTATO IN EASTERN SCOTLAND: II. INFESTATION OF THE POTATO CROP BY POTATO APHIDS, PARTICULARLY MYZUS PERSICAE (SULZER)
Authors: FISKEN A. G.
Published: February 2008

Surveys in the years 1954‐56 showed that potato crops in most districts of eastern Scotland were infested by the aphids Myzus persicae (Sulz.), Macrosiphum euphorbiae (Thomas) and Aulacorthum solani (Kltb.). Crops in different districts became infested by Myzus persicae at different times and to different extents, and these differences seemed consistent between years. Crops in the Edinburgh area were colonized between mid‐May and mid‐June, whereas crops in north Perthshire escaped infestation until the end of July or mid‐August. The time and degree of infestation by M. persicae seems correlated with distance from sites where this aphid overwinters. Trap records show that many alate M. persicae disperse from outdoor brassica and early potato crops in the Edinburgh area between mid‐July and mid‐August, a period during which potato crops in Fife, Angus and Perthshire usually become infested. The freedom of crops in the better seed‐producing areas from widespread infection by potato leaf roll and Y viruses is probably associated with lateness of aphid infestation rather than scarcity of aphid vectors.
FUNGICIDAL ACTIVITY AND CHEMICAL CONSTITUTION: VII. A STUDY OF THE STRUCTURAL SPECIFICITY OF SEVEN FUNGICIDES
Authors: BYRDE R. J. W. , WOODCOCK D.
Published: February 2008

The relative saturations of the following fungicides, in dilute McIlvaine buffer containing sucrose, required for 50% inhibition of spore germination of Sclerotinia laxa were determined as under: phenylmercuric chloride, 0.0002; nystatin, 0.028; dichlone, 0.034; copper‐8‐quinolinolate, 0.039; 2:4‐dichloro‐6‐(o‐chloroanilino)‐s‐triazine, 0.131; captan, 0.132; bis‐(5‐chloro‐2‐hydroxyphenyl)methane, 0.234. These values are discussed in relation to current views on the fungitoxicity of the compounds.
A COMPARATIVE STUDY OF THE GROWTH OF WILD OATS (AVENA FATUA L. AND A. LUDOVICIANA DUR.) AND OF CULTIVATED CEREALS WITH VARIED NITROGEN SUPPLY
Authors: THURSTON JOAN M.
Published: February 2008

Growth analysis of wild oats (Avena fatua and A. ludoviciana) grown in pots with different levels of nitrogen supply showed many similarities to spring barley, winter oats and winter wheat.

Small differences that could affect competition between wild oats and cereals occurred mainly in the seedlings. Wild oat seedlings were smaller than the corresponding cultivated cereals in total dry weight, total nitrogen content, leaf area and number of shoots. However, very young wild oat plants had higher net assimilation rates than the cultivated cereals and soon caught up and passed them. The difference in net assimilation rate did not persist, and in the later stages of growth differences in dry‐matter production depended mainly on differences in leaf area. Another important difference between wild oats and cultivated cereals was that 98–100% of the wild oat seeds and none of the crop seeds were dormant 2 months after harvest.

Ear emergence in wild oats spread over a longer period, the range of ear heights was greater and the tallest ears were taller than in the corresponding cultivated cereals. Assimilation in the ear appeared to account for less of the total dry matter of the plants of wild and cultivated oats than of wheat. The wild oats produced more seeds per plant than the cultivated cereals, but the 1000‐grain weight, and hence the total dry weight of seeds, was lower in the weeds than in the crop.

Addition of nitrogen to the soil affected the growth of the wild oats in the same ways as the cultivated cereals; they took up the same amount of nitrogen per plant as winter oats and winter wheat but more than spring barley.

It is concluded that wild oats are most susceptible in the seedling stage to competition from the crop and that nitrogenous fertilizer applied to an infested field is unlikely to alter the balance between the yields of crop and of wild oats.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Authors: VITOU HELEN , WAIN R. L.
Published: February 2008

The cress‐root test and the maize‐root segment tests, both of which depend on the measurement of root‐growth inhibition, have been used to assess the growth‐regulating activity of a wide range of phenoxyalkanecarboxylic acids. The results are presented and compared with those obtained with the same compounds in other tests in which shoot tissues were employed. The results are also discussed in relation to current theories on mode of action and structure/activity relationship. These studies included the ‘α‐hydrogen’ effect, the activity of stereoisomers and activity of homologues of seventeen series of ω‐phenoxyalkanecarboxylic acids, considered in relation to their degradation within the tissues by β‐oxidation. Earlier findings were largely confirmed. Compounds which had previously been shown to be active in shoot tests such as the wheat‐cylinder, the pea‐curvature and the pea‐segment tests, were found to be active in the root‐growth inhibition tests and, furthermore, the degree of activity was usually similar.

It is concluded that the two root tests investigated are of real value in assessing the activity of phenoxy acids in studies on the relationships between chemical structure and plant growth‐regulating activity.
EXPERIMENTS ON THE MODE OF ACTION OF DIELDRIN SEED‐DRESSINGS AGAINST SEEDLING ATTACK BY THE LARVAL FRIT FLY, OSCINELLA FRIT L
Authors: WAY M. J.
Published: February 2008

Experiments with dieldrin seed‐dressings were done to see whether the conditions favouring their action against wheat bulb fly larvae apply also to frit fly.

Experiments with oats and wheat in boxes and a small field trial with oats showed that fewer newly hatched larvae were killed when dieldrin‐treated seed was sown deeply than when sown 1/4 ‐ 1/2 in. deep; shallow sowing probably puts the insecticide where the larvae are likely to meet it before they attack the plant. Kill was never complete even with dieldrin applied at almost forty times more than the highest rate normally used. This is partly because some larvae hatch from eggs on the plant and these, unlike those from soil eggs, can enter the shoot without touching the seed dressing.

Even in the most favourable circumstances (large doses of dieldrin applied to the shallow‐sown seed and the plant at the one‐leaf stage at the time of attack) there was little evidence that frit fly larvae are killed inside the shoot by systemic action of dieldrin translocated from the seed. This is not because the pales which normally surround the oat seed impair the uptake of insecticide, or because of any other factor specific to oats. Frit fly larvae also survived in wheat from seed dressed with doses of dieldrin that can kill almost all wheat bulb fly larvae by systemic action. Possible reasons for this difference are discussed.
SOME OBSERVATIONS ON THE CEREAL‐ROOT EELWORM POPULATION OF FIELD PLOTS OF CEREALS WITH DIFFERENT SOWING TIMES AND FERTILIZER TREATMENTS
Authors: HESLING J. J.
Published: February 2008

In the autumn of 1953 an experiment was begun to follow changes in the cereal‐root eelworm population of small plots on a field in Shropshire. The plots were cropped with either oats, wheat, barley or rye, sown in the autumn and spring, and some plots had fertilizer. Each plot received the same treatment for 3 years; in the fourth year an indicator crop of spring oats was grown on all the plots.

Under rye and autumn‐sown wheat the eelworm population fell to a level which permitted a good oat crop in 1957. Autumn‐sown wheat, barley and rye generally produced lower eelworm populations than their spring‐sown counterparts, but autumn‐sown oats proved to be the most efficient host. The order of host efficiency was oats (best), barley, wheat, rye. The eelworm populations were generally higher on plots receiving fertilizer treatment. In this experiment all oat plots, and spring‐sown barley plus fertilizer, produced populations which severely damaged the 1957 oat crop.
STUDIES ON THE DERMESTID BEETLE TROGODERMA GRANARIUM EVERTS: ECOLOGY IN MALT STORES
Authors: BURGES H. D.
Published: February 2008

Detailed studies on the environment in malt stores and its effect on the Khapra beetle are described. The observations are correlated with the conclusions from parallel laboratory work.

Bulks of malt are stored at 26–69° C. and cooling near their centres is slow. After loading, the distribution of heat is controlled mainly by the position of the kiln, the size of the store and the development of Khapra infestations. Three zones of temperature may be recognized, too hot for Khapra (above 40° C.), favourable (30–40° C.) and too cool for rapid breeding (below 30° C.). Population growth may be progressively retarded by cooling, or heat from the kiln and insect‐heating may allow continuous breeding, although part of the malt may be heated above 40° C., causing migration of the larvae. Some migrants stop in a new favourable zone and others continue into the cool zone, often for a long way.

The larva is the most prominent stage in most populations. Throughout population growth, low temperature and the accumulation of faecal pellets cause some larvae to enter diapause and hide either in crevices or on the walls just below the malt surface. After the malt is unloaded, huge numbers of larvae may be hidden and some may survive for more than 4 years. Reloading with new, hot malt stimulates some of the cryptic larvae to emerge, pupate and breed. More larvae emerge from the hottest positions than from elsewhere. The very sharp gradient of humidity in stores does not appear to influence larval behaviour. In contrast to unmalted cereals, malt is too dry to allow a significant upward translocation of moisture above a hot region.

Control is very difficult. Current methods involve persistent attack on larvae in empty stores with methyl bromide and contact insecticides, combined with structural improvements. Control by cooling the malt before storage is promising.
THE EFFECTS OF SPRAY TREATMENTS ON INFESTATION OF THE OAT CROP BY THE FRIT FLY (OSCINELLA FRIT L.)
Authors: JEPSON W. P.
Published: February 2008

Criteria are given for the timing and assessment of the effect of sprays on experimental plots, based on biological observations at Silwood Park from 1950 to 1955 and on previous work.

A preliminary experiment on small plots in 1952 indicated that ‘blanket spraying’ with DDT and parathion throughout the life of the crop gave protection against both tiller and grain attack. A more detailed replicated plot trial in 1953 showed that for oats planted on 22 April two carefully timed tiller sprays with parathion reduced tiller infestation from 31 to 3%. Six panicle sprays at weekly intervals reduced a heavy grain attack of 60% to 13%. Dieldrin was also effective but significantly less so than parathion. Much of the damage to the crop was caused by weed growth following initial loss of the primary oat shoots.

In 1954 and 1955 two and three parathion sprays were applied to 2‐acre fields in order to study recolonization. Despite almost complete control of the tiller generation, a normal evenly distributed infestation of the panicles was found.

It is concluded that good control of the tiller generation may best be achieved by a spray programme based on knowledge of the phenology of the fly combined with that of the crop. The first general emergence in early May is likely to be critical.

Reinvasion of a sprayed crop may take place within 4–5 days and panicle infestation may not be causally related to tiller infestation in the same field.
SEED AND SOIL TREATMENT WITH SYSTEMIC INSECTICIDES TO PREVENT APHID COLONIZATION OF EMERGING BEET SEEDLINGS
Authors: GATES L. F.
Published: February 2008

Dimefox at 2 lb. or diethyl ethylthiomethyl dithiophosphate (Thimet) at 1 lb. applied at drilling in 100 gal. water along the drills, or seed treated at rates giving 6–8 oz. Thimet or 8–24 oz. diethyl ethylthioethyl dithiophosphate (Disyston) per acre†, made sugar beet seedlings toxic to aphids up to 30 days after sowing four root crops in April‐May, and up to 30–40 days after sowing five steckling crops in autumn. Malathion, demeton, demeton methyl, bis (dimethylamino) azido phosphine oxide (N.C.7) and schradan were less effective. The infestation of green aphids was decreased by the treatments during what is often a critical period for virus infection in summer‐sown stecklings and occasionally in spring‐sown root crops. Germination was 73–100% of the control after soil treatments, 91–98% after Disyston seed treatments and 62–84% after Thimet seed treatments. The treatments slightly decreased Aphis fabae injury to steckling seedlings in 1955 and the number of plants with yellows in a steckling experiment in 1956.
FURTHER EXPERIMENTS ON BLACK‐LEG DISEASE OF SUGAR‐BEET SEEDLINGS
Authors: GATES L. F.
Published: February 2008

Soaking sugar beet seed for 20 min. in ten times its weight of water containing 40 p.p.m. ethyl mercury phosphate to control seed‐borne Phoma betae gave better seedling emergence than surface treatments with commonly used organo‐mercury dusts or with Panogen (methyl mercury dicyandiamide), thiram, Granosan M (ethyl mercury p‐toluene sulphonanilide), captan, Dow 9B (zinc trichlorophenate) or Cerenox (acylphenylhydrazone). In 4 years' field trials, soaking seed in ethyl mercury phosphate solution followed by dusting with an insecticidal dust, compared with a routine mercury‐plus‐insecticidal dust, increased seedling emergence at fifty‐three of fifty‐nine sites by an average of 10% under good emergence conditions and by 20–30% under adverse conditions. Final plant stand was increased each year by an average of 5.8, 3.4, 1.8 and 0.6%, respectively.
STUDIES OF THE BIOLOGY OF SCLEROTIUM CEPIVORUM BERK: HOST RANGE; PERSISTENCE AND VIABILITY OF SCLEROTIA
Authors: COLEY‐SMITH J. R.
Published: February 2008

In a number of host range tests infection by Sclerotium cepivorum occurred only on Allium spp.

Sclerotia of S. cepivorum were almost unaffected by 2 years' dry storage in the laboratory. A high proportion survived for 4 years under undisturbed conditions in the field. There was no effect of soil pH, soil nutrient status, or inorganic supplementation on sclerotial persistence. Organic soil supplements gave variable results, sometimes reducing sclerotial numbers and on other occasions having no effect.

Weekly rubbing of nylon bags containing soil and sclerotia caused the latter to disintegrate, but trowelling of soil containing sclerotia had no effect.

It is concluded that S. cepivorum sclerotia persist in soil for many years, in the absence of the host plant, and that outbreaks of white rot on rested land could be due to such survival.
STUMP PROTECTION AGAINST FOMES ANNOSUS: TREATMENT WITH SUBSTANCES OTHER THAN CREOSOTE
Authors: RISHBETH J.
Published: February 2008

Various substances when added to the stump surface in concentrated solution directly after felling markedly affect the course of fungal colonization. The extent to which applications kill stump tissues probably affects the rate at which saprophytes develop.

Nitrogenous applications favour growth of Trichoderma viride and Penicillium spp., which tend to suppress surface colonization by Fomes annosus; ammonium sulphamate is especially effective in this respect.

Some other applications are initially toxic to stump fungi but rapid leaching from the stump surface soon permits growth of various moulds, which again tend to suppress F. annosus and to a large extent other primary basidiomycete colonizers. Substances of this type include urea, which encourages growth of Ophionectria cylindrospora, and disodium octaborate, which favours Botrytis cinerea. The probable mode of action of these substances is discussed.

Stumps usually die more rapidly after such treatments than after creosoting, and often as fast as untreated ones. The rapid colonization of treated stumps by saprophytes is of advantage where application is incomplete or the stump is subsequently damaged. The effectiveness of treatments in preventing a major spread of Fomes annosus from roots already containing the parasite is variable and apparently depends to some extent on the particular species becoming dominant.

Preliminary screening may be performed in the laboratory with sections of pine stem inoculated with stump fungi; potential protectants are then tested in the forest.
VIRUSES OF COWPEA, VIGNA UNGUICULATA L. (WALP.), IN NIGERIA
Authors: CHANT S. R.
Published: February 2008

The cowpea strain of tobacco mosaic virus was isolated from a range of leguminous hosts at Ibadan, but was rare in cultivated crops. Systemic symptoms in species infected experimentally are described.

A new virus of cowpea was also found in Nigeria. The physical properties (thermal inactivation point 56° C., dilution end‐point 1/50,000 and longevity in vitro 4 days at 25° C.) differ from those for cowpea viruses reported elsewhere and the name cowpea yellow mosaic virus is proposed. This virus produces local lesions in French bean (Phaseolus vulgaris L.) and local and systemic lesions in Bengal bean (Mucuna aterrima Holland), but does not infect other leguminous hosts. The virus was purified and an antiserum prepared against it.

Both viruses are transmitted by a beetle (Ootheca mutabilis Sahlb.) which loses infectivity within 48 hr. of leaving plants infected with either or both viruses.
FIELD TRIALS OF THE EFFECT OF ALDRIN ON CLUBROOT OF SUMMER CABBAGE
Authors: CHANNON A. G. , KEYWORTH W. G.
Published: February 2008

Field experiments were carried out from 1956 to 1958 on the effect of soil applications of aldrin on clubroot disease of summer cabbage. In the first two seasons the compound was applied either as a dust, broadcast and worked into the soil, or as an emulsion watered round the plants. Results in 1956 were inconclusive and the same plots were used again in 1957, the same quantities of aldrin being re‐applied. In this season increasing doses of the compound gave increasing control of the disease. The treatment of individual plants with emulsion was more successful than the application of dusts.

In 1957 half of each plot received a heavy dressing of ground limestone. Lime alone gave a control equal to that given by the highest aldrin treatment. Lime and aldrin together gave a further reduction in clubbing.

In 1958 increasing doses of emulsion were tested. These gave increasing control of disease but the higher doses caused some phytotoxicity which was reflected in a delay in maturation of the crop.

A reduction of clubbing from ‘severe’ to ‘moderate’ caused a marked increase in crop, but further reductions in clubbing did not result in any corresponding increase in crop weight.
THE INCIDENCE OF CERTAIN SEED‐BORNE DISEASES IN COMMERCIAL SEED SAMPLES
Authors: MARSHALL GILLIAN M.
Published: February 2008

The incidence of ergot, Claviceps purpurea (Fr.) Tul., in commercial cereal seed samples submitted to the Official Seed Testing Station from 1918 to 1957 has been examined.

Rye samples were more frequently contaminated than wheat or barley and no cereal ergots were recorded in oats.

A relatively high proportion of ergot‐contaminated rye samples occurred every 8–10 years. This appeared to be associated with high relative humidity and low maximum temperature during June. Similar trends were found for wheat and barley.

No varietal differences in susceptibility to ergot contamination were found for rye or barley, but there was some evidence that spring wheat varieties were more frequently contaminated than winter ones.
THE COLIFORM BACTERIA ASSOCIATED WITH POTATO BLACK‐LEG AND OTHER SOFT ROTS
Authors: GRAHAM D. C. , DOWSON W. J.
Published: February 2008

The biochemical characteristics of twenty‐five isolates of soft‐rot coliform bacteria from different countries are recorded. Because of the variability of the reactions, strains capable of producing potato black‐leg at both low and high temperatures, or at higher temperatures only, cannot be distinguished from one another with certainty by biochemical tests alone. They do, however, give an indication of potential pathogenic reactions. Thus the low‐temperature strains correspond with Pecto‐bacterium carotovorum var. atrosepticum and are distinguished from the high‐temperature isolates by their gas production, rapid fermentation of lactose and maltose, methyl red and Voges‐Proskauer reactions and failure to give a positive indole test.

Because of their delayed lactose fermentation the chrysanthemum blight pathogen, the carnation slow wilt organism, the guayule bacterium and the organism causing leaf rot of Philodendron are classified as a new variety of P. carotovorum (Jones) Waldee.

The diagnosis of the coliform soft‐rot bacteria should be based on qualitative and quantitative biochemical reactions rather than on host range.
MOVEMENT OF EELWORMS
Authors: WALLACE H. R.
Published: February 2008

The optimum crumb sizes for movement of potato‐root eelworm larvae in a sandy loam, a heavy clay and a peat soil were 150–250 and 250–400 μ. Mobility was very similar in clay and sandy loam, in both of which there was an optimum suction for movement. In the peat, however, mobility increased with suction and no optimum suction was established. Larvae may be able to move in peat at high suctions because friction between the larvae and the peat crumbs is less than between clay or sand crumbs. Larvae moved to the wet end of a moisture gradient in sand, the number increasing with the steepness of the gradient. The rate of spread of larvae in sand 150–250 μ diameter varied between 2 and 3 cm. a day, depending on suction. As pore size increases, any upward movement in a moisture gradient is opposed by falling under gravity. Larvae do not respond to a moisture gradient or fall under gravity in sand where the width of the pore approximates to the diameter of the larva. The presence of host roots also counteracted the response to a moisture gradient; the degree of orientation to the roots increased with the time the roots were in the sand. Direct observation on larvae, newly emerged from cysts, in the presence of host plant roots, suggests that larvae orientate themselves at a distance from the root and do not reach the root by random movement. Many of the movements of eelworms are explicable by considering the relationship between pore size, eelworm diameter and water distribution, and a diagram relates movement and various soil factors.
THE POLLINATION REQUIREMENT OF THE FIELD BEAN (VICIA FABA)
Authors: RIEDEL I. B. M. , WORT D. A.
Published: February 2008

Many of the flowers on field bean plants fail to produce pods even when fully pollinated. When insect pollination is prevented pod production on the lowest inflorescences, which normally produce most pods, is reduced but a compensatory increase on the upper ones ensures a moderate yield. This change in the distribution of pods may be a useful indication of insufficient pollination.
TOPICAL APPLICATION OF MOBILE LIQUIDS TO INSECTS BY MEANS OF MICRO‐CAPILLARY TUBES
Authors: HEWLETT P. S. , LLOYD C. J.
Published: February 2008

A method is described for topical application of mobile liquids, whether volatile or not, to insects. The principle is that of the self‐filling micro‐pipette, the ‘pipettes’ being calibrated lengths of fine, thin‐walled glass capillary tube; for use a micro‐capillary tube is mounted in a special holder. The doses delivered were shown to be adequately reproducible for mean doses of 0.03 μl. upwards. Precautions in use are: (1) in filling the capillary, its tip is dipped into the reservoir of liquid no more deeply than is necessary: (2) the dose is applied to the insect in such a way that the liquid is carried rapidly away from the delivery tip; and (3) pressure for expulsion of the dose from the capillary is maintained until after the delivery tip is removed from the insect.

A convenient apparatus for keeping a batch of insects under anaesthesia during their dosage is described.
THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM‐ROT OF TOMATOES
Authors: HACK JUDITH , WILLIAMS P. H.
Published: February 2008

About 93% of Didymella lycopersici spores were destroyed after 4 weeks incubation in unsterilized soil. A survey of the microflora of glasshouse soil receiving different treatments and inoculated with D. lycopersici showed no clear relation between numbers of any group of organisms and the incidence of stem rot. Sterilized soil was not made toxic to D. lycopersici by the growth of a number of soil microorganisms even after 9 months incubation, but addition of unsterilized soil or of a suspension of unsterilized soil quickly restored toxicity. Direct observations of spores in soil on slides showed that their fate varied with the treatment of the soil before inoculation. With fresh soil or air‐dry soil moistened 2 or more days before inoculation, lysis of spores occurred. With air‐dry soil moistened and inoculated simultaneously, some spores germinated but growth of germ tubes soon ceased. No direct connexion could be seen between the fate of the spores and soil microorganisms. Addition of glucose to unsterilized soil reduced its toxicity to D. lycopersici. Soils steamed for 1 min. or longer were not toxic to D. lycopersici, but soils steamed for very short periods were as toxic as unsterilized soils although the soil microflora was much reduced.
THE TOXICITY OF SOME INSECTICIDES TO FIFTH‐INSTAR NYMPHS OF THE DESERT LOCUST
Authors: MacCUAIG R. D.
Published: February 2008

The toxicities of the insecticides γ‐BHC, diazinon, dieldrin, DNC, heptachlor and parathion to fifth‐instar hoppers of the desert locust were determined. Parathion and dieldrin were the most toxic, followed in descending order by heptachlor, γ‐BHC, diazinon and DNC. The resistance of the hoppers to γ‐BHC and DNC changed appreciably with age within the instar.

The effects of some factors which might influence the resistance of the insects were examined and are discussed.