bluuebunny/crossref_metadata_2025 huggingface dataset:
SOIL POPULATIONS OF BEET EELWORM (HETERODERA SCHACHTII SCHM.) IN RELATION TO CROPPING
Authors: JONES F. G. W.
Published: February 2008

Experiments on specially constructed microplots were undertaken to overcome some of the difficulties associated with population studies using field plots. In these microplots Cruciferae caused greater increases in beet‐eelworm populations than Chenopodiaceae when the initial population was low and greater decreases when it was high. Non‐hosts and inefficient hosts caused reductions of the same order as host plants in the same families.

When sugar beet was grown at varying initial populations, the final population tended to rise to a ‘ceiling’ which varied with soil and season. The ‘ceiling’ effect is also observed in the field and in pot tests, and may be used as a measure of the efficiency of different host plants or, if the same host plant is grown, as a measure of the effect of different soils and seasons. A linear relationship exists between the logarithm of the initial eelworm population and the yield of roots and tops.

Eelworm attack upon sugar beet renders the plants incapable of profiting from favourable growing conditions and reduces the size of the plants without affecting the sugar content of the roots. Within certain limits, the final eelworm population is independent of yield or plant density. Cruciferae are far less susceptible to injury by root invasion than the cultivated varieties of Beta vulgaris.

It is suggested that host efficiency in raising and supporting eelworm populations and susceptibility to injury are distinct and independent attributes of host plants. Decay of populations in land under fallow or non‐host crops in non‐host families is approximately 20, 40 and 50% per annum for cysts, cysts with contents, and eggs respectively, and appears to be largely independent of initial population level. The average egg content of cysts with contents falls from 177 eggs/cyst in the first winter after the cultivation of a host crop to 131, 118 and 114 in the second, third and fourth respectively. The in vitro hatch from beet‐eelworm cysts is affected by previous cropping. Low hatches are sometimes obtained in the winter and spring after the cultivation of host crops, especially where there has been considerable increase. A period of maturation appears to be necessary before eggs are fully sensitive to hatching stimuli.

The implications of the microplot results are briefly discussed. Population increase appears to be limited by intraspecific competition rather than by specific enemies. The development and decline of infestations follows a course similar to that in other pests but, because of lack of mobility, the time factor is greatly extended. The differential effects of soil, season and host crop render set rotations ineffective as a measure of control once land has become generally infested. At this stage a system of advice based on soil sampling is desirable.
SOIL AERATION AND THE EMERGENCE OF LARVAE FROM CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHM
Authors: WALLACE H. R.
Published: February 2008

Moisture content, pore size, depth and oxygen consumption in the soil, which influence soil aeration, have been studied in relation to larval emergence from cysts of the beet eelworm. Experiments show that the rate of larval emergence increases with aeration. In studies of larval emergence in the field emphasis should be laid on soil structure rather than on a mechanical analysis. Those factors associated with good soil tilth favour high rates of larval emergence.
THE ROTTING OF APPLES BY GLOEOSPORIUM PERENNANS ZELLER & CHILDS
Authors: EDNEY K. L.
Published: February 2008

The extent of rotting of commercially stored Cox's Orange Pippin apples by Gloeosporium species has been severe in recent years. G. perennans has been found to be mainly responsible.

Tree infections of this fungus have usually been found to be prevalent in the orchards on farms where storage losses of fruit have occurred, and conidia of G. perennans have been found on cankers at all seasons during the year. Winter as well as summer pruning cuts have been found to become infected. Detached leaves of Cox's Orange Pippin have been successfully inoculated with G. perennans in the laboratory and the fungus has also been found on dead detached leaves in the orchard after picking time. Considerable variations have been found in the susceptibility to rotting of samples of different varieties of apple and samples of Cox's Orange Pippin apples from different orchards. Periodic loading of fruit with spores after picking has shown that resistance declines with length of storage. Wide variation in the time at which rotting commences in commercially stored samples has been observed. A series of inoculations on picked and unpicked immature fruit has shown that the apple loses its resistance to attack on picking. Lenticels which are impermeable to gaseous exchange have been shown to be resistant to penetration by the fungus. Temperature affects the development of lenticel rotting by G. perennans, infection being most rapid at temperatures of about 20°. Rotting can occur at 0° C.
A SOLANACEOUS HOST OF THE VIRUS OF ‘INFECTIOUS CHLOROSIS’ OF MALVACEAE*
Authors: SILBERSCHMIDT K. , TOMMASI L. R.
Published: February 2008

Viruses that are transmitted by white‐fly occur commonly in solanaceous and malvaceous species, and infected plants from both families often exhibit similar kinds of symptoms. Consequently it has often been assumed that the same viruses infect species in both families, although attempts to demonstrate this experimentally have all failed. Now, however, using Bemisia tabaci (Genn.), we have transmitted the infectious chlorosis virus of Malvaceae from Sida rhombifolia to Nicandra physaloides. Bemisia tabaci also transmitted the virus from infected Nicandra physaloides to healthy seedlings of both N. physaloides and Sida rhombifolia. Attempts to infect Nicotiana tabacum failed.
BARK‐SPLIT–A VIRUS DISEASE OF PLUMS
Authors: POSNETTE A. F. , ELLENBERGER CHRISTINA E.
Published: February 2008

The bark‐split disease of plums commences with necrotic lesions in the outer bark, causing depressions on the surface; these lesions extend in area and depth, resulting in split and roughened bark, and crippling or killing trees of sensitive varieties like Cambridge Gage.

The causal virus was transmitted by grafting in the dormant season, but, probably because it is localized in older tissues, it was rarely transmitted or scion‐perpetuated by summer budding.

About 90% of Common Plum clonal rootstocks from East Malling Research Station's layer‐beds were found to be infected. Apparently virus‐free Common Plum was propagated by cuttings from the roots of Common Plum under normal Cambridge Gage trees.

A different type of bark‐split disease developed on Shiro Plum inoculated with virus from a tree of Quetsche Précoce de Zimmer. Leaf symptoms accompanying infection with this and with the virus from Common Plum were similar.

Bark‐split disease is compared and contrasted with diamond canker of French Prune in California, and features that distinguish bark‐split from bacterial canker are described.
TRANSMISSION AND HOST‐RANGE STUDIES OF STRAWBERRY GREEN‐PETAL VIRUS
Authors: FRAZIER N. W. , POSNETTE A. F.
Published: February 2008

The virus causing phyllody (virescence) in clover flowers was transferred by Cuscuta subinclusa to Fragaria vesca and Duchesnia indica plants which then produced symptoms of strawberry green‐petal disease.

The jassid Euscelis plebejus (Fall.) in several forms, including E. lineolatus Brullé, transmitted green‐petal virus from clover to clover, to and from a wide range of other hosts, and from but not to strawberry. Two viruses (or strains) were distinguished, one causing phyllody and the other witches' broom on clover; both were retained for more than 2 months by the vector, in which both had a latent period of about 30 days. Macrosteles viridigriseus (Edwards) also transmitted both viruses.

Variation in symptoms on strawberry plants infected naturally, and experimentally through dodder, suggested that two diseases have previously been grouped under the name ‘green petal“. It is proposed to distinguish these as (a) green petal caused by the virus inducing phyllody in clover, and (b) bronze leaf wilt caused by the clover witches' broom virus.
INVESTIGATION OF CHRYSANTHEMUM VIRUSES II. VIRUS B (MILD MOSAIC) AND CHRYSANTHEMUM LATENT VIRUS
Authors: HOLLINGS M.
Published: February 2008

Chrysanthemum virus B is widespread in English chrysanthemum stocks, but it appears to do little damage, for in thirty‐four varieties it caused no or very slight symptoms; the name mild mosaic is proposed for the disease.

Virus B infected ten out of eighty‐six plant species tested by mechanical inoculation and by grafting. Petunia was used as a local lesion test plant; petunias were much less susceptible to infection during the summer. In addition, some petunias showed genetical resistance at all seasons. The concentration of infective virus B in chrysanthemum sap decreased in the summer.

Virus B was transmitted by five out of six aphid species tested; aphids became infective with short acquisition feeds, and lost infectivity within 1 hr.

Chrysanthemum was difficult to infect by mechanical inoculation, and the virus was not spread by leaf contact, or by knives used for taking cuttings.

The thermal inactivation point of virus B is between 70 and 75°C.; the dilution end‐point varied from 1/10 to 1/1000, depending on the host plant tissue from which sap was obtained; the virus inactivated within 24 hr. at 18°C.

Infective sap contained rod‐shaped particles, about 750 ± 17 mμ, not found in sap from uninfected plants. Three strains of virus B were differentiated by their reaction on petunia; one strain prevented infection by a second.

Two other, previously unrecorded, viruses were found in chrysanthemums that cause local lesions in petunia: vein mottle virus was similar in some ways to virus B, but virus B did not protect plants against vein mottle. Vein mottle severely damaged some varieties of chrysanthemum, but caused no symptoms in others.

Chrysanthemum latent virus was carried without symptoms by eleven varieties of chrysanthemum; thirteen out of twenty‐seven plant species were readily infected by mechanical inoculation. Latent virus had a dilution end‐point of 1/200 to 1/500, was inactivated after 10 min. at 70°C., or within 48 hr. at room temperature. It was not spread by the cutting knife, root contact, or by two species of aphid. It was found rarely and seems of no commercial importance in English chrysanthemum stocks.
THE USE OF TETRACHLORONITROBENZENE ISOMERS ON POTATOES
Authors: BROOK M. , CHESTERS C. G. C.
Published: February 2008

In laboratory and field experiments from 1952 to 1955, 2:3:5:6‐tetrachloro‐I‐nitrobenzene (tecnazene) delayed the development of sprouts on treated potato tubers, and 2:3:4:6‐TCNB retarded sprout development in two laboratory experiments. At the usual commercial rates of application the 2:3:4:5 isomer had no effect on sprout development and very little effect at higher rates. The crop from 2:3:5:6‐TCNB‐treated seed tubers usually contained a higher proportion of small tubers than that from untreated or 2:3:4:5‐TCNB‐treated seed. Marketable yield from 2:3:5:6‐TCNB‐treated seed was sometimes below that from untreated seed, but when this happened the yield from 2:3:4:5‐TCNB‐treated seed was higher.

Both isomers produced good control of dry rot, Fusarium caeruleum (Lib.) Sacc., on five varieties of potatoes, but did not produce a commercial control on Doon Star. To achieve control, the isomers had to be present at the time of infection. There was some evidence that the development of disease symptoms was delayed in treated, infected tubers. Since 2:3:4:5‐tetrachloro‐1‐nitrobenzene has no sprout depressant action it merits further trial as a fungicidal treatment for seed potatoes.
GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE L.) III. ABSORPTION AND DISTRIBUTION OF NITROGEN, PHOSPHORUS AND POTASSIUM DURING THE FIRST YEAR OF GROWTH
Authors: WILLIAMS R. DORRINGTON
Published: February 2008

Absorption of nitrogen, phosphorus and potassium by S48 timothy plants ran parallel to dry‐weight increase, at an increasing rate until the autumn, almost completely ceasing in the winter, and increasing again in the spring.

Flowering tillers accumulated nutrients until ear emergence, after which the content per tiller of all nutrients decreased until death of the tillers during the winter.

Non‐flowering tillers continued to accumulate nutrients steadily throughout the whole period of the experiment.

These observations are discussed in relation to the perennial habit of the plant.
THE EFFECT OF DATE OF SOWING ON THE INCIDENCE OF POWDERY MILDEW ON SPRING‐SOWN CEREALS
Authors: LAST F. T.
Published: February 2008

Delaying the date of sowing of spring‐sown barley in 1953 and wheat in 1954 from February to April increased the incidence of powdery mildew, Erysiphe graminis DC., from May onwards. Before then, conditions did not favour the rapid spread of mildew.

From mid‐June, infected barley produced necrotic lesions. These developed sooner on the early‐ than on the late‐sown crops, and on the lower than upper leaves. Perithecia were first seen on 29 June. They were abundant on the wheat by 20 July.

Mildew reduced the yield of barley sown on 30 March and 28 April 1955 by 8 cwt./acre. The percentage loss was greater in the late‐ than in the early‐sown crops. The number of ears per metre of row, the weight of 100 ears and the 1000‐grain weights were reduced. Altering the seed rate from 1 ½ to 2½ bushels/acre did not affect the incidence, or the effect, of mildew on grain yield.
CONCENTRATE SPRAYING OF APPLE TREES I. FUNGICIDAL EFFICIENCY OF LIME‐SULPHUR
Authors: MOORE M. H.
Published: February 2008

Experiments are described in which the efficiency of undiluted lime‐sulphur applied as a spray mist of small droplets, formed by and carried in a stream of compressed air, was compared on small Cox's Orange Pippin apple trees with that of diluted lime‐sulphur applied either in the same way or by orthodox hydraulic spraying. The control without spray damage of apple scab (Venturia inaequalis (Cooke) Wint.) and apple mildew (Podosphaera leucotricha (Ell. & Everh.) Salm.) was the criterion.

The undiluted concentrate proved at least as effective and safe as the hydraulically applied dilute spray when a satisfactory method of application, by a paint spray gun, had been established. A 50% dilution applied in this way at increased volume proved equally effective, but a 10% dilution similarly applied failed to give satis‐factory control of scab, probably because of the reduced dosage.
ANEMONE MOSAIC–A VIRUS DISEASE
Authors: HOLLINGS M.
Published: February 2008

The name anemone mosaic is proposed for a previously unrecorded virus disease of Anemone coronaria L.; infected plants have mottled leaves, and broken and distorted flowers. This virus can cause winter browning, and can contribute to crinkle in anemones.

The virus infected forty‐seven out of ninety plant species tested; it was transmitted by mechanical inoculation, and by four of the six aphid species tested. Most aphids ceased to be infective within 30 min. when continuing to feed after leaving an infected plant.

Properties in vitro varied according to conditions of the tests; the thermal inactivation point was always below 62°C., the dilution end‐point did not exceed 1/2500, and the virus inactivated at 18°C., the fewer than 72 hr.

Intracellular inclusion bodies were produced in all hosts examined.

Anemone mosaic virus is very similar to viruses placed in the turnip virus 1 group of Hoggan & Johnson, and is serologically related to cabbage black ringspot virus, although AMV infection did not protect plants against infection with cabbage black ring‐spot virus.

Weeds naturally infected with AMV were found in anemone plantations, and this virus was detected, together with cucumber mosaic and tobacco necrosis viruses, in corms imported into this country.
THE BIOLOGICAL CONTROL OF THE WATTLE BAGWORM (KOTOCHALIA JUNODI HEYL.) BY A VIRUS DISEASE
Authors: OSSOWSKI L. L. J.
Published: February 2008

The polyhedral virus disease of the wattle bagworm is described together with a method of purifying and assaying the virus. A procedure is suggested for making preparations of the virus suitable for spraying large areas.

Aqueous suspensions of 10,000 polyhedra/cu. mm. applied to trees when the larvae were hatching caused a very high mortality; there was no increased mortality when higher concentrations were used. Newly hatched larvae showed symptoms after 3–4 days' feeding on contaminated food and they died 2 days later. Older larvae died more slowly, but the mortality was still high enough to prevent serious defoliation of the infected trees.

The polyhedra remained infective out‐of‐doors for long enough to suggest that a high mortality could be obtained by spraying before the larvae emerged. Once disseminated in the field, polyhedra were not washed off by heavy rain and they appeared not to affect insect parasites of the bagworm.
THE SURVIVAL OF RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON) AND PERCH (PERCA FLUVIATILIS L.) AT VARIOUS CONCENTRATIONS OF DISSOLVED OXYGEN AND CARBON DIOXIDE
Authors: ALABASTER J. S. , HERBERT D. W. M. , HEMENS J.
Published: February 2008

The relative importance of dissolved oxygen and dissolved carbon dioxide in determining the lethal effect of an environment for rainbow trout and perch has been investigated with an apparatus which controls the concentrations of these gases in a body of water. It is shown that concentrations of carbon dioxide which sometimes occur in polluted streams can more than double the minimum concentration of dissolved oxygen necessary for the survival of half a population of rainbow trout fingerlings for 24 hr. Increase in temperature between 12·5 and 19·5°C. shortens period of survival in solutions containing up to 67 p. p. m. CO2. Within the range of dissolved oxygen concentration which is lethal in the presence of 59 p. p. m. CO2 or more, perch are more resistant than rainbow trout in the lower, but less resistant in the higher, oxygen concentrations. The relation between carbon dioxide concentration and the oxygen tension at which rainbow trout blood is half saturated with oxygen is similar to the relation between carbon dioxide concentration and the oxygen tension at which the median period of survival of this species is I hr.
OBSERVATIONS ON THE CONTROL OF POTATO‐ROOT EELWORM (HETERODERA ROSTOCHIENSIS WOLLENW.) UNDER GLASS BY D‐D* AND SOLUBILIZED p‐m CRESOL†
Authors: STONE L. E. W.
Published: February 2008

D‐D injected at 400 Ib./acre into light loam in two glasshouses in Wiltshire killed 93.9 and 91.5% of the eelworm population, respectively, in the 0–9 in. soil layer.

Growing tomatoes in pots in house 1 on top of the treated soil resulted in an overall fall in eelworm population to approx. one‐seventh of its original value. Tomatoes grown in the treated soil in house 2 built up the population to approx. times its original level.

Combined treatments, using solubilized cresols as a surface seal instead of water, increased the kill in the 0–3 in. soil layer, but a higher degree of kill here is still required.

All populations have been estimated by the root diffusate technique.
THE INFLUENCE OF TEMPERATURE AND DAYLENGTH ON SPOTTED WILT VIRUS DISEASE OF TOMATO
Authors: SELMAN I. W. , GRANT SHEILA A.
Published: February 2008

The responses of young tomato plants to infection with tomato spotted wilt virus were studied at constant temperatures. The plants were grown in nutrient solutions and given three daylength treatments.

The length of the incubation period was positively correlated with temperature and a regression equation for this relationship is given. The calculated temperature at which this period becomes infinite is 6.7°C. The temperature coefficient (Q10) varied from 1.7 to 2.9.

Dry‐weight determinations were made of stems, leaves and roots. In healthy plants the leaf/stem ratio generally fell with rise of temperature and the shoot/root ratio rose. Infection changed these ratios, which is interpreted as indicating that it interfered with supplies of carbohydrate to the growing regions.

Systemic symptoms are described for plants raised at 11.4°, 18.3°, 23.9°, and 29.4°C.

Changes in daylength did not affect the systemic symptoms or incubation period. With a 9 hr. day at 29.4°C., the virus content of sap was significantly lower than with 12 or 15 hr., and with a 12 hr. day was significantly higher than with a 15 hr. day.
THE INSECTICIDAL MATERIAL IN LEAVES OF PLANTS GROWING IN SOIL TREATED WITH PARATHION
Authors: DAVID W. A. L. , ALDRIDGE W. N.
Published: February 2008

After parathion solutions had been watered on to soil around the roots of cabbage plants with leaves infested with Brevicoryne brassicae, Myzus persicae or Pieris brassicae larvae, these leaves showed a toxic effect on the feeding insects. In comparable experiments, Aphis fabae on leaves of broad bean was not affected at dosages that damaged the plants. The effect on the cabbage plants was observed when the parathion was of the highest degree of purity, as shown by chemical tests and its negligible anticholinesterase activity, although it was greater with commercial grade material. It occurred when all possibility of a fumigant action was excluded.

When the roots of wheat plants were treated with solutions of pure parathion the leaf guttation fluid was toxic to Aëdes aegypti larvae and contained an active anticholinesterase. This was shown to be paraoxon; no parathion could be detected in the fluid. The paraoxon was formed rather slowly from the parathion when the roots and leaves of wheat seedlings were immersed in the solution but not in the presence of compost alone.

In plants treated with pure parathion the translocation of the paraoxon formed under the influence of the roots was sufficient to account for the toxic effects produced. With commercial parathion, analogues or isomers present as impurities may also be translocated. Both these sources of systemic poisons should be borne in mind when considering parathion treatment of greenhouse soil in which food crops are to be grown.
THE USE OF TISSUE CULTURES TO PRODUCE VIRUS‐FREE CLONES FROM INFECTED POTATO VARIETIES
Authors: KASSANIS B.
Published: February 2008

By growing the excised apical meristems of sprouts from the potato varieties King Edward and Arran Victory, infected respectively with potato paracrinkle virus and potato virus S, virus‐free plants were obtained. Although the method failed to produce virus‐free plants from varieties infected with potato virus X, this virus also seems not to be present in apical meristems, for no virus could be demonstrated in callus tissue that developed from excised meristems less than 200 μ across. The concentration of tobacco mosaic virus in tomato roots and tobacco stems is also much less near the growing point than in older cells, but there is no evidence that the meristematic region is virus‐free.
THE EFFECT OF MALEIC HYDRAZIDE ON THE GROWTH RESPONSE OF PLANTS TO GIBBERELLIC ACID
Authors: BRIAN P. W. , HEMMING H. G.
Published: February 2008

Maleic hydrazide (MH) and gibberellic acid (GA) were applied alone and in combination at various doses to dwarf and tall varieties of garden pea, and their effect on stem extension measured. Combinations of MH and 3‐indolylacetic acid (IAA) were also studied. Stern extension of dwarf peas was accelerated by GA and inhibited by MH. Their effects were not additive, since MH reduced the response to GA at all concentrations of each tested. IAA did not affect stem extension, whether applied alone or in combination with MH. Stem extensions of tall peas was not affected by GA or IAA alone. MH severely inhibited growth and this inhibition was not reduced either by GA or by IAA. At low doses MH broke apical dominance and side branches developed; extension of these was stimulated by GA and IAA and extension of the main axis correspondingly still further reduced. The results show that MH prevents the response to GA of GA‐sensitive plants. It is suggested that the rapid growth of tall peas, as compared with that of dwarfs, and their lack of response to GA, are due to a greater capacity to synthesize a ‘GA‐like hormone’. Growth of tall peas is much more drastically inhibited by MH than that of dwarf peas and the suggestion is made that the inhibition of shoot growth induced by MH is due primarily to blocking the activity of the postulated ‘GA‐like hormone’.
THE EFFECT OF TENSION OF DISSOLVED OXYGEN ON THE TOXICITY OF UN‐IONIZED AMMONIA TO SEVERAL SPECIES OF FISH
Authors: MERKENS J. C. , DOWNING K. M.
Published: February 2008

The resistance to rapidly lethal concentrations of un‐ionized ammonia ranging from about 2.0 to 8.8 p. p. m. N was determined for rainbow trout (Salmo gairdnerii Richardson), perch (Perca fluviatilis L.), roach (Rutilus rutilus (L.)), and gudgeon (Gobio gobio (L.)) in tensions of dissolved oxygen 53.4 and 96.7% of air‐saturation value at 15.2°C.

The relation between concentration of un‐ionized ammonia and period of survival from a few hours to 13 days was investigated for rainbow trout in two tensions of dissolved oxygen, 45.7 and 100.3% of air‐saturation value, at 20.1°C.

Period of survival of all the species tested decreased with rise in concentration of un‐ionized ammonia.

Decrease in tension of dissolved oxygen increased the toxicity of un‐ionized ammonia to all species except gudgeon, for which there was no significant difference in period of survival at the two levels of oxygen.

The effect of oxygen tension on period of survival was greatest in the lowest concentrations of un‐ionized ammonia.

Resistance of perch and roach to lack of oxygen was not significantly affected, but that of rainbow trout was reduced significantly, by the presence of a small concentration of ammonia (not toxic to trout within at least 13 days).
GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE)
Authors: LANGER R. H. M.
Published: February 2008

All tillers of timothy (Phleum pratense) growing in sand culture were labelled at weekly intervals. At each of eighteen dates between June and December a sample of plants was harvested, and dry weight and leaf area were determined for each group of tillers.

Tiller production was continuous throughout the experiment. Only those tillers which appeared before the end of July were able to form inflorescences, but among them the proportion of tillers with ears decreased with increasing lateness of origin.

Dry weight per plant increased rapidly for the first 14 weeks, and then did not change significantly until the end of the experiment. The flowering tillers lost dry weight after seed maturation; vegetative tillers, although smaller in size, continued to increase in number and weight. Dry weight per inflorescences was greatest in the main stem and decreased in subsequent tillers.

Leaf area per plant rose to a maximum soon after ear emergence and then declined, largely because the loss in leaf surface sustained by the flowering tillers was not offset by a corresponding increase in the vegetative tillers. Leaf area ratio decreased at first rapidly but later more gradually, while net assimilation rate was relatively high until maximum leaf area was almost attained, but then fell continuously to negligible values by October. Relative growth rate decreased throughout the experiment.

Initially the growth of the plant was largely determined by the flowering tillers in which, in close resemblance to the cereal plant, leaf area ratio and relative growth rate declined continuously. Tillers which did not flower were successively smaller in size and, because of their later origin, were exposed to less favourable environmental conditions by the time they had increased sufficiently in number to affect the growth of the plant.
WILT OF LUCERNE CAUSED BY SPECIES OFVERTICILLIUM
Authors: ISAAC IVOR
Published: February 2008

A wilt disease of lucerne caused by species ofVerticilliumis described: at twenty‐eight disease areas in England and Wales the pathogen wasV. albo‐atrum, while at one site it wasV. dahliae. Both pathogens form superficial conidia on the basal regions of infected stems. It is shown thatV. albo‐atrumis introduced into a new area in contaminated plant material harvested with the seed from an infected crop. Rapid secondary spread of the disease follows the dissemination of spores from infected stems, and by contact of these and transported fragments of diseased tissues with the wounded surfaces of recently cut lucerne plants. It is recommended that seed should be collected only from healthy crops and that machinery, footwear, etc. should be disinfected before leaving a site of infection.

Manurial trials showed that the incidence of wilt induced byV. albo‐atrumwas very severe under all soil conditions tested, whereasV. dahliaeis a virulent pathogen only to plants in soil rich in superphosphate. Generally the more vigorous the growth of the lucerne–in soils rich in potash and hoof and horn–the more rapid is both the onset of wilt and the resulting secondary spread of the disease throughout the crop.
STUDIES ON THE HOST RANGES OF VIRUSES FROM THEOBROMA CACAO L.
Authors: TINSLEY T. W. , WHARTON A. L.
Published: February 2008

Only plants in the natural order Tiliales were susceptible to experimental infection by viruses found infecting cacao. Of sixty‐three species in the Tiliales colonized with infective mealybugs, twenty‐eight became infected with the New Juaben virus. The ease with which different species contracted infection and the severity of symptoms varied considerably. The host ranges of seven other viruses were all contained in that of the New Juaben virus. The viruses could be divided into three groups according to their host ranges, and it is suggested that host ranges may prove helpful in attempts to classify cacao viruses. Four species of Corchorus were all rapidly killed by any of the eight viruses.
THE ACTION OF DRUGS ON THE NERVOUS SYSTEM OF THE LOCUST (LOCUSTA MIGRATORIA)
Authors: HARLOW P. ANNE
Published: February 2008

Two preparations of the hind‐leg of the locust have been used to investigate the physiological effect of chemicals on nerve muscle and on the central nervous system.

In the first preparation, the isolated hind‐leg is made to kick regularly by electrical stimulation of the crural nerve. Test chemicals are perfused in saline solution through the femur.

The second preparation makes use of a reflex synapsing in the metathoracic ganglion. A reflex retraction of the tibia of the hind‐leg is initiated by stimulating the tarsus by heat at regular intervals; the chemicals are applied in agar or paraffin blocks directly to the ganglion. In both cases the movements of the tibia or of the extensor or flexor tibialis muscles separately are recorded mechanically on a smoked drum.

Acetylcholine has no action on the nervous system except for an unusual action on the nerve muscle preparation. Acetyl β‐methylcholine, carbamylcholine and benzoylcholine have no action on either preparation except at high concentration.

Decamethonium and d‐tubocurarine had no effect on either preparation, while nicotine and eserine, after initial excitation, caused a simple reversible block in both preparations, the ganglion being affected at a lower concentration.

Adrenalin and adrenergic drugs have no effect on either preparation.

The organo‐phosphorus insecticides, parathion, paraoxon and TEPP, acted on the ganglion only and at low concentrations. Their main site of action is on the central nervous system.

DDT affected ganglionic and nerve muscle preparations, whereas γ‐BHC acted rather similarly on the ganglion but had no effect on nerve muscle.

There is no evidence for a cholinergic mechanism at the neuromuscular junction in the leg muscles. The ganglion, on the other hand, was markedly affected by the anticholinesterases tested, but acetylcholine and related cholinesterase substrates, and drugs which interfere with the action of acetylcholine in mammals, had no effect. Acetylcholine was still without effect when injected through the membrane sheathing the ganglion. On the other hand, micro injection experiments show that the sheath is relatively impermeable to prostigmine.
THE CONTROL OF CERTAIN PLANT DISEASES WITH SULPHONAMIDES
Authors: CROWDY S. H. , ELIAS R. S. , JONES D. RUDD
Published: February 2008

In in vitro tests, sulphanilamide was more toxic to plant pathogenic fungi than to bacterial plant pathogens, but sulphadiazine and other heterocyclic‐ring substituted compounds were more toxic to plant pathogenic bacteria than to fungi. When tested in vivo against a number of facultative plant parasites the sulphonamides were without effect except in providing slight control of Pseudomonas coronafaciens on oats. Against a number of obligate parasites including Uromyces fabae on broad beans and Puccinia triticina on wheat, the sulphonamides gave effective control when applied either through the roots or leaves. The minimal effective concentrations in the leaves of the more active compounds varied between 100–200 μg./g. fresh weight of leaf tissue.

The sulphonamides are also toxic to higher plants and both the fungitoxic and phytotoxic effects could be reversed with p‐aminobenzoic acid.

A number of sulphanilamides with acyl substituents on the p‐amino‐group were tested against P. triticina and were shown to control the disease with very slight phytotoxic damage. Control could be attributed to the release of ‘free’ sulphanilamide by hydrolysis within the plant.

Two factors appear to control the systemic action of sulphonamides: first, the movement in the plant which results in the accumulation of effective concentrations in the leaves, and secondly, the specificity of a sulphonamide for a particular host‐parasite association.
THE USE OF TETRACHLORONITROBENZENE ISOMERS ON LETTUCE
Authors: BROOK M. , CHESTERS C. G. C.
Published: February 2008

Field experiments were carried out from 1951 to 1955 on winter lettuce plants grown in boxes under glass and in the open, and on commercial crops in unheated glasshouses. Each of the three isomers of tetrachloronitrobenzene, applied as 5% dusts at 1/4 and 1/2 oz. per square yard of bed, gave significant protection against Botrytis disease, but the 2:3:4:5 isomer was inferior to the other two isomers and they all delayed the hearting of the crop. The 2:3:4:5 isomer at both rates of application and the 2:3:5:6 and 2:3:4:6 isomers at 1/2 oz./sq.yd. delayed hearting of a commercial crop by more than 14 days and are not recommended at these rates. Local overdoses of fungicide should be avoided.
FUNGICIDAL ACTIVITY AND CHEMICAL CONSTITUTION
Authors: BYRDE R. J. W. , CLIFFORD D. R. , WOODCOCK D.
Published: February 2008

A series of 5‐n‐alkyl oxines was tested against the mycelium of Aspergillus niger. As non‐chelated molecules, they showed maximum fungistatic activity at a chain length of 5–6 carbon atoms. Values of Ferguson's thermodynamic activity coefficient, obtained from spore germination tests with Sclerotinia laxa, indicated that the mechanism of toxicity of the lower homologues is predominantly chemical, whilst that of the n‐amyl and higher members is mainly physical.

The ED 50 value of 5‐n‐amyl‐6‐hydroxyquinoline, which is incapable of chelation, was found to be eighty times greater than that of 5‐n‐amyl oxine (in the non‐chelated form). The optimum initial pH for fungistatic activity of the latter was 5.4–5.6.

In the presence of metals the pattern of fungistatic activity was markedly altered: maximum activity in the presence of Cu2+, Fe2+and Zn2+was found with oxine and 5‐methyloxine.
FACTORS AFFECTING INFECTION GRADIENTS FROM A POINT SOURCE OF PUCCINIA POLYSORA IN A PLOT OF ZEA MAYS
Authors: CAMMACK R. H.
Published: February 2008

Two plots of Zea mays were planted in April and September, respectively, at Ibadan, Nigeria during 1956. A point source of inoculum consisting of potted maize plants heavily infected with the American corn rust, Puccinia polysora Underw., was introduced at pre‐arranged times before the plots became naturally infected. Disease gradients from these point sources of infection were assessed by the number of pustules subsequently appearing on plants along the circumferences of concentric circles around the source of infection. ‘Control’ plots were planted at the same time as the main trial and the pattern of natural infection was observed in an attempt to assess the degree of contamination in the main experiment.

In the centre of the main experiment a volumetric spore trap gave continuous records of the uredospore content of the atmosphere immediately above the crop during both plantings for periods of 2 weeks before planting until 2 weeks after the last assessment of infection.

The forms of the disease gradients were considerably altered by several factors—principally contamination by inoculum from outside sources, the method of assessment and the time at which the assessments were made.
STUDIES ON THE TRANSMISSION OF CASSAVA MOSAIC VIRUS BY BEMISIA SPP. (ALEYRODIDAE)
Authors: CHANT S. R.
Published: February 2008

Whiteflies, which had originated from a mixed culture of Bemisia spp. collected from cassava (Manihot utilissima Pohl.) in the field, needed to feed for at least 4 hr. on the young leaves of a cassava plant with mosaic before they acquired the virus. Whiteflies that acquired virus in 4–6 hr. required another 4 hr. to become viruliferous. Once viruliferous they could infect healthy plants in a feeding period of 15 min., but longer periods gave more infections. Adult whiteflies remained infective for more than 48 hr. after ending their infection feed. Cassava fed upon by only one viruliferous fly sometimes became infected.

The virus‐vector relationships of cassava mosaic virus resemble those of cotton leaf‐curl virus but the first could not be transmitted to cotton or the second to cassava.
RASPBERRY YELLOW DWARF, A SOIL‐BORNE VIRUS
Authors: HARRISON B. D.
Published: February 2008

An apparently undescribed virus, provisionally named raspberry yellow dwarf virus (RYDV), was isolated from naturally infected raspberry, strawberry, blackberry and several weed species by mechanical inoculation of sap to Chenopodium amaranticolor. The severe disease it caused in Malling Exploit raspberry usually occurred patchily in otherwise normal plantations: these patches increased in size from year to year. RYDV was differentiated from raspberry ringspot and tomato black ring viruses by the symptoms produced in C. amaranticolor, tobacco and Petunia hybrida. RYDV lost infectivity when sap was heated for 10 min. at 61° C., diluted 10‐5or kept for 15 days at 18° C. RYDV was precipitated without inactivation by acetone and by ammonium sulphate.

Isolates of RYDV from different plants and localities, and of different virulence, were identified by plant‐protection and serological tests. Such tests gave no evidence that RYDV was related to raspberry ringspot, tobacco ringspot, tomato black ring or cucumber mosaic viruses.

Raspberry and sugar‐beet plants became systemically infected with RYDV when grown under glass in soil from a field where the disease had occurred in raspberry plants, and where the virus persisted in the soil for 3 years after the raspberry plants were removed. RYDV seems to be widely disseminated in England but recently introduced and rare in eastern Scotland.

Like raspberry ringspot and tomato black ring viruses, RYDV causes symptoms of the ringspot type in tobacco, has a wide natural and experimental host range, is soil‐borne and of local importance. Such features seem characteristic of ringspot viruses as a group.
‘BULBIFORMIN’, AN ANTIBIOTIC PRODUCED BY BACILLUS SUBTILIS
Authors: VASUDEVA R. S. , SUBBAIAH T. V. , SASTRY M. L. N. , RANGASWAMY G. , IYENGAR M. R. S.
Published: February 2008

The antimicrobial spectrum of the antibiotic produced by Bacillus subtilis has indicated that it is chiefly antifungal. In the presence of the antibiotic, a characteristic bulb formation has been observed in the spores and hyphae of the test fungi. The active principle has been shown to be thermolabile. The importance of magnesium in relation to growth and antibiotic production has been indicated. Large quantities up to 30 p.p.m. are required for maximum production of the antibiotic which is not intracellular, but is secreted into the medium.

The data presented suggest that the antibiotic under consideration is different from those of B. subtilis previously described, therefore the name proposed for this antibiotic is ‘bulbiformin’.
LIGHT QUALITY AND PHOTOREACTIVATION OF PLANTS AND VIRUSES
Authors: CHESSIN M.
Published: February 2008

Visible light of different spectral regions was tested for its ability to reverse three effects of ultra‐violet radiation, namely, injury (glazing) of French bean leaves, increased resistance of French bean leaves to infection by the Rothamsted tobacco necrosis virus, and inactivation of potato virus X. The different spectral regions were obtained with colorimetric filters and the filtered and unfiltered light from fluorescent tubes; all three effects were reversed only by regions of wave‐lengths shorter than 4700 Å. Thirty minutes of illumination at 300–380 f.c. gave substantial photo‐reactivation, but irradiated potato virus X did not become affected by visible light until 30 min. after tobacco leaves were inoculated.
A COMPARISON OF HIGH AND LOW VOLUME SPRAYS FOR CONTROL OF THE BEAN APHID, APHIS FABAE SCOP. ON FIELD BEANS
Authors: WAY M. J. , BARDNER R. , van BAER R. , AITKENHEAD P.
Published: February 2008

Insecticides were sprayed in different amounts of water to control Aphis fabae Scop. attacking spring‐sown field beans. The single application of each insecticide was timed to coincide with the end of aphid migration from the winter host to the crop. A tractor‐mounted row‐crop hydraulic sprayer was used.

In one experiment seven different insecticide sprays were compared at high volume (in 140 gal. of water per acre); the most effective were nicotine at 22.4 oz. of active constituent per acre, demeton at 5.6 oz. and demeton‐methyl at 11.2 oz.

A further comparison was made of five insecticides for each of which a selected dose of active ingredient was applied in 60 gal. (medium volume) and in 10 gal. of water per acre (low volume). The amount of insecticide retained on the plant following the low‐volume application was not less than that from the medium‐volume spray; the efficiency of A. fabae control was not affected by the volume sprayed except with malathion which did better at the medium volume. The systemic insecticides demeton‐methyl at 6 oz. of active constituents per acre, the related compound 4741 at 3 oz. and fluoroacetamide at 3 oz. stopped the aphid numbers from rising above a peak of eight per plant compared with 230 per plant for malathion (low volume) at 12 oz. 2400 per plant for lindane at 6 oz. and 3550 per plant for check treatments sprayed with wetter only. Grain yields ranged from around 4 cwt. per acre on check treatments to around 27 cwt. per acre on plots sprayed once with the systemic insecticides. There was a curvilinear relationship between grain yield and log number of A. fabae per plant.
STUDIES ON SOIL POPULATION OF CONTARINIA PISI WINN. IN 1957 IN YORKSHIRE AND LANCASHIRE
Authors: BEVAN W. J. , UNCLES J. J.
Published: February 2008

For studying the population of pea‐midge cocoons, larvae and pupae in the soil, a new method of examining the ‘float’ obtained from washing soil through the wet‐extraction apparatus is described.

Examination of soil samples in the summer of 1957 from fields which carried heavily attacked pea crops in 1956 indicated that pupae were present at depths of 0–3, 3–6, 6–9 in., respectively, from 18 June onwards, and that the peak emergence of midges was in the period 28 June‐2 July; observations on adult activity in pea fields confirmed this. Small numbers of pupae were recovered throughout July.

Similar studies on pea fields in 1957 showed the build‐up of the cocoon population and the rate of pupation of this generation of larvae. The first flight of 1957 was composed of individuals from the 1956 generation and was far larger than the second flight, which was composed of some 1956 generation and part of the first 1957 generation.

There were indications that increases of temperature might accelerate pupation with a resulting earlier emergence of adults.

The size of midge populations recorded from soil from green pea and dry‐harvesting pea fields tended to be similar and appeared to be related to sowing date.
STRIATE MOSAIC OF CEREALS IN EUROPE AND ITS TRANSMISSION BY DELPHACODES PELLUCIDA (FAB.)*
Authors: SLYKHUIS JOHN T. , WATSON MARION A.
Published: February 2008

A virus disease that resembles wheat striate mosaic was found affecting up to 5% of the plants in English wheat fields in 1956. Symptoms on wheat included fine chlorotic striae, followed by stunting, general chlorosis, and death of plants. Other hosts included oats, barley, rye, perennial rye grass and Italian rye grass.

The virus was transmitted by Delphacodes pellucida (Fabricius) (Homoptera, Delphacidae). A few of the insects were already infective when caught in the field. The percentage of infective individuals was increased by feeding the insects for 24 hr. or longer on diseased plants, and up to 56% became infective after feeding on diseased plants for 3 days. Non‐infective insects were unable to transmit the virus until from 8 to 36 days after they first fed on diseased plants, but they frequently remained infective for the remainder of their lives, up to 10 weeks after feeding on a diseased plant. Infective insects seldom transmitted the virus during test feeds as short as 30 min. When fed for 1 or more days on each test plant, some insects infected many plants in succession, others seldom infected test plants even if they fed as long as 7 days on each. The virus was transmitted through the eggs to as many as 88% of the progeny of infective females, and to some of the progeny of a few females that had failed to infect wheat test plants.
THE DISTRIBUTION OF VIRUSES IN LEAVES AND THEIR INACTIVATION BY ULTRA‐VIOLET IRRADIATION
Authors: HITCHBORN J. H.
Published: February 2008

The infectivity of sap expressed from the lower epidermis stripped from leaves systemically infected with potato virus Y, henbane mosaic virus or tobacco mosaic virus was compared with that of sap from the underlying mesophyll. Results suggested that the concentration of virus in each of the two tissues was about the same.

Ultra‐violet irradiation of leaves infected with potato virus Y or henbane mosaic virus greatly reduced the infectivity of sap expressed from subepidermal tissues.
PROPERTIES AND HOST RANGE OF TURNIP CRINKLE, ROSETTE AND YELLOW MOSAIC VIRUSES
Authors: BROADBENT L. , HEATHCOTE G. D.
Published: February 2008

Three isolates of turnip yellow mosaic virus and two other flea‐beetle transmitted viruses, turnip crinkle and turnip rosette, have many similar properties: thermal inactivation end‐point between 80 and 90° C.; dilution end‐point greater than 10‐4; longevity in vitro at about 20° C. at least 30 days. All were transmitted by mechanical inoculation to a wide range of cruciferous host plants, including many weeds. Turnip yellow mosaic virus infected only Reseda odorata outside the Cruciferae, whereas rosette virus infected a few and crinkle virus many non‐cruciferous hosts.