bluuebunny/crossref_metadata_2025 huggingface dataset:
OBSERVATIONS ON THE BIOLOGY and CONTROL OF CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE (BCHE)
Authors: MILES MARY
Published: February 2008

In the south‐east of England egg‐laying by Erioischia brassicae Bche began in the third week of April and was at its maximum in the fourth week of April and the first week of May. From then on to early October small numbers of eggs were continually present about brassica crops. Egg counts on cauliflowers at the end of April showed up to 141 eggs/plant and on spring cabbage on 6 May up to 117 eggs; the flies showed no preference for newly set plants. Eggs on the soil were almost exclusively those of Erioischia brassicae; eggs on the plants were mainly those of Pegohylemyia fugax Meig., with small numbers of Erioischia brassicae and Delia cilicrura Rond.

Larvae were found continuously from the fourth week of April to mid‐January, those found in December and January were from the previous autumn. Larvae, up to eighty‐one per plant, at the roots of brassica crops were almost exclusively Erioischia brassicae. A few Pegohylemyia fugax and Delia cilicrura occurred, but no Erioischia floralis Fall, were found. A technique for separating larvae from the soil and plant roots is described.

Great variation in the size of puparia was noted. Small puparia (4‐4‐5 mm. long) were heavily parasitized by cynipid wasps.

In trials on cauliflowers and brussels sprouts the efficiency of calomel dust (4 %) and benzene hexachloride (flea beetle and wireworm dusts) was compared. An application of B.H.C. wireworm dust at 40 lb./acre (approximately 11,000 plants) appeared to have the same efficiency as an application of calomel dust at the rate of 80 lb./acre. The concentration of benzene hexachloride in flea beetle dust applied at rates up to 40 lb./acre (11,000 plants) was insufficient to secure the measure of control given by calomel dust at 80 lb./acre. In 1949 calomel dust remained effective from 2 July, when it was applied, until 30 August when observations ceased.

Good growing conditions masked injury and were very important in preventing loss from injury by cabbage root fly.
THE COMPARISON OF SUCTION TRAP, STICKY TRAP and TOW‐NET FOR THE QUANTITATIVE SAMPLING OF SMALL AIRBORNE INSECTS
Authors: JOHNSON C. G.
Published: February 2008

The sticky trap and stationary aerial ‘tow‐net’ catch insects which alight or fly on to them or are blown against them by the wind. It would be expected that such traps would be inefficient in light winds or in calm weather; and even though their efficiency should increase with stronger winds, errors of unknown magnitude may occur not only in estimations of density and of proportions of species in the air, but also with comparisons of actual catches. These errors are due to unknown degrees of weighting as the traps sample by means of a variable wind from a changing population density. The suction trap, on the other hand, samples a constant quantity of air in all relevant wind‐speeds and does not appear to suffer so seriously from these disadvantages. It also works efficiently in perfectly calm weather when maximum densities of insects are often in the air.

The performances of the three traps in the field operating over a range of wind‐speeds are described. Particular attention has been paid to aphids, for which the sticky trap and tow‐net are generally used and for which the suction trap was primarily designed. Density estimates of these insects in winds below about 3 m.p.h. are much larger when calculated from suction trap catches as compared with estimates from sticky trap and tow‐net catches. There is reason for the belief that the suction trap is neither attractive nor repellent to aphids to a significant extent, and that it catches these insects at random by virtue of its air stream alone; weighting of catches due to variable quantities of air being sampled does not occur. It is considered, therefore, that the suction‐trap values of density are likely to be the more accurate ones. Sampling of other small insects is also discussed.
SOIL SAMPLING FOR POTATO ROOT EELWORM CYSTS
Authors: ANSCOMBE F. J.
Published: February 2008

The National Agricultural Advisory Service (Advisory Entomologists) has adopted a uniform soil‐sampling technique for potato root eelworm. In Part I the recommended technique is quoted in full. In Part II an account is given of some experimental sampling done by the Advisory Entomologists, on which the recommendations are partly based. In trying to estimate the average cyst content of the soil of a field, a statistical problem is encountered of deciding on an adequate sampling procedure. A similar problem was investigated in the wartime wireworm survey, but the rather different features of eelworm sampling call for fresh consideration of points of detail.
NOTES ON THE FEEDING HABITS OF HOUSE‐RATS IN RANGOON, BURMA
Authors: HARRISON J. L. , WOODVILLE H. C.
Published: February 2008

During a poison campaign against house‐rats, particularly of the species Bandicota bengalensis, Rattus rattus nr. khyensis and R. exulans concolor, a number of incomplete experiments were carried out on feeding habits and the take of poison.

The rats showed a reaction to new objects similar to that of R. norvegicus in England.

A marked preference was shown for boiled rice over any other available foodstuff. The amount eaten was roughly proportional to the surface area of the rat. Barium carbonate in boiled rice was an acceptable poison bait, and the optimum concentration of poison was in the range 10–20%.
HOST ALTERNATION IN APHIS FABAE SCOP. I. FEEDING PREFERENCES AND FECUNDITY IN RELATION TO THE AGE AND KIND OF LEAVES
Authors: KENNEDY J. S. , BOOTH C. O.
Published: February 2008

The feeding preferences and comparative fecundity of laboratory‐bred, alienicolae alatae of Aphis fabae were investigated in small leaf cages on spindle and sugar beet leaves, representing a winter and a summer host respectively, both in pots in the greenhouse and while growing naturally outdoors.

The aphids' readiness to stay and feed, and their average reproduction rate, both varied between leaves of different ages and kinds, and there was evidence of true fecundity differences among aphids feeding on different leaves. As a general rule, readiness to settle and reproduction rate varied together in the same sense, but they did so significantly less often in comparisons between leaves of different kinds, spindle and beet, than in comparisons between leaves of one kind only. Among the leaves on the same kind of plant, the aphids preferred to feed and reproduced faster, on the whole, on young and early senescent leaves than on mature ones. To a limited extent, this rule seemed to govern also the aphids' comparative readiness to settle and reproduce, as between leaves of the two different kinds of plant. Allowing for age‐differences among the leaves, the aphids settled and reproduced better on spindle than on beet leaves. Since the aphids used were alienicolae, this tends to confirm the usual designation of the winter host as primary and the summer hosts as secondary, for a given aphid species.

These findings form the basis of a dual discrimination theory of host selection, which assumes that aphids respond behaviourally to at least two main classes of leaf property: one associated with the age of the leaf and the other with the kind of plant. It is suggested that in nature these two sensory requirements of the aphids may be essentially contradictory, and that the shifting patterns of aphid distribution among leaves and plants may depend on the shifting distribution of leaves offering a satisfactory compromise between them. The phenomenon of host alternation is considered in the light of the dual discrimination theory, as a particular instance of a shifting distribution‐pattern probably connected with the alternation of the seasons of active growth and senescence in the winter and summer host plants.
AGGREGATION IN APHIS FABAE SCOP. I. AGGREGATION ON PLANTS
Authors: IBBOTSON ALAN , KENNEDY J. S.
Published: February 2008

A study of free infestations of Aphis fabae Scop. on the leaves of its host plants, spindle and sugar beet, showed that the clustered distribution of the aphids within the boundaries of each leaf was not a matter of chance but involved active aggregation. Experiments in small leaf cages showed that aggregation could take place independently of any differences between portions of a leaf, being brought about by truly gregarious reactions between the aphids. Experiments in which walking aphids were made to encounter other live or dummy aphids fixed to leaves, showed that the gregarious reactions were of at least two kinds. The aphids both probed more often, and remained inserted for longer, near other aphids than apart from them.

It appears that the unequal distribution of aphids among the leaves of a plant is due primarily to intrinsic differences between leaves, but is aided by gregariousness, while the aggregations observed on leaves are due primarily to gregariousness, and only secondarily to differences between portions of a leaf. It is suggested that the primary function of gregariousness is to concentrate the aphids on to the best feeding sites, both among the parts of a plant, and among whole plants; that is, it acts as an aid in host selection, even with aphids which do not aggregate so compactly as A. fabae. The functions of compact aggregation and other specialized forms of gregarious behaviour remain to be discovered.
THE POTATO TUBER NEMATODE, DITYLENCHUS DESTRUCTOR THORNE, 1945; THE CAUSE OF EELWORM DISEASE IN BULBOUS IRIS
Authors: GOODEY J. BASIL
Published: February 2008

For about twenty‐five years a fairly widespread disease of bulbous iris has been known, the cause of which has always been attributed to a biologic race of the stem eelworm Ditylenchus dipsaci (Kühn, 1857), Filipjev, 1936.

Thorne (1945) showed that the nematode causing rot in potato tubers is different from D. dipsaci and named it D. destructor. This nematode has since been reported from Mentha arvensis L. by Hurst (1948) and from Sonchus arvensis L. by Goodey & Goodey (1949).

Examination of nematodes from diseased iris bulbs showed them to possess rounded tail tips and six incisures on each lateral field; characters by which Ditylenchus destructor is distinguished from D. dipsaci.

Cross‐inoculation experiments showed that the eelworm causing disease in potato tubers would invade and set up characteristic symptoms in iris bulbs and, in the opposite direction, the eelworm responsible for disease in iris bulbs would give rise to characteristic symptoms in potato tubers. Transfer was also effected from potato and iris to Mentha arvensis and from iris to Sonchus arvensis.

The history of the disease in bulbous iris is briefly reviewed and the biology of Ditylenchus destructor discussed and compared with that of D. dipsaci.

The conclusion that D. destructor is the nematode causing eelworm disease of bulbous iris has been reported earlier (Goodey, J. B. 1950).
THE INSECTICIDAL ACTIVITY OF PARATHION, ITS ISOMERS AND SOME RELATED COMPOUNDS
Authors: WOODCOCK D. , STRINGER A.
Published: February 2008

Heat treatment of parathion at 140° C. and above resulted in isomerization and then thermal decomposition; the loss of toxicity to Calandra granaria being correlated with a reduction of the thiono‐sulphur content. Similar results were obtained with O:O‐dimethyl‐(4‐nitrophenyl)‐thiophosphate. Paraoxon, O:S‐diethyl‐(4‐nitrophenyl)‐thiophosphate, and O:O‐diethyl‐S‐(4‐nitrophenyl)‐thiophosphate, although all possessing considerable contact activity, were less insecticidal than parathion; O:O‐dimethyl‐(4‐nitrophenyl)‐thiophosphate, on the other hand, was considerably more effective than parathion. O:O‐bis(2‐chloroethyl)‐O‐(4‐nitrophenyl)‐thiophosphate was considerably less toxic than parathion and appeared to have a different mode of action. Compounds, S‐ethyl‐bis‐(4‐nitrophenyl)‐thiophosphate, O‐ethyl‐bis‐(4‐nitrophenyl)‐thiophosphate, and triethyl thiophosphate were ineffective as contact insecticides.

In the series of compounds examined, replacement of the group P = S by P = O or alteration in size of the groups attached to the central phosphorus atom caused a reduction of insecticidal activity.
THE CONTROL OF WIREWORM BY GAMMA BENZENE HEXACHLORIDE: THE DEVELOPMENT OF A SEED DRESSING FOR CEREALS
Authors: JAMESON H. R. , THOMAS F. J. D. , TANNER C. C.
Published: February 2008

Gamma benzene hexachloride has been used successfully as a seed dressing in field trials for wireworm control. For application to cereals at 2 oz./bushel, the optimum concentration of γ‐isomer was 20–30 % in a dressing which advantageously included an organomercurial seed disinfectant.

Risks to germination and plant growth were thoroughly explored in the field. The 20 and 30 % dressings were safe; over‐strength dressings containing 50 or 70 %γ‐B.H.C. did not reduce grain yields significantly.

Seed dressed with 20 or 30 %γ‐B.H.C. germinated normally after storage for 12 months. When seed was dressed at 4 oz./bushel with 35 %γ‐B.H.C. and 1 % mercury as organomercurial, germination was delayed but total emergence was not affected.
THE EFFICIENCY OF CHEMICAL TREATMENTS OF VEGETABLE SEEDS AGAINST SEED‐BORNE AND SOIL‐BORNE ORGANISMS
Authors: JACKS HARRY
Published: February 2008

Out of thirty‐four newer fungicides tested in greenhouse and field trials, red cuprous oxide (Cuprocide), tetrachloroparabenzoquinone (Spergon), methyl mercury dicyandiamide (Panogen), tetramethylthiuram disulphide (T.M.T.D.), ferric dimethyldithiocarbamate (F.D.D.), zinc trichlorophenate (Dow 7B) and 1‐p‐sulphamylphenyl‐3:5‐dimethyl‐4‐nitrosopyrazole (36L) were selected for detailed investigation on lettuce, pea, French bean, turnip, red beet, tomato and celery. Derivatives of dithiocarbamic acid, and 36L and Spergon among non‐metallic compounds compared favourably with cuprous oxide and organomercurial compounds. Addition of hormones, insecticides or nemacides did not improve emergence. Soil tests were more satisfactory than laboratory selection. Rates of application recommended by manufacturers often injured small seeds, and the optimum dosages were determined by extensive tests.

Results obtained depended on conditions of test. Under glass, emergence was lower at 5–12° C. than at 16–20° C. Emergence was optimum at 45 % water‐holding capacity, and additional tests are required at higher and lower moisture to assess phytocidal and protectant action.

In field trials seed treatments were generally most beneficial in cool and moist soil, and improved emergence in all but driest soil. T.M.T.D., Spergon and 36L were the most effective seed protectants. Mixing of these materials did not improve emergence. Emergence in relatively dry soil (25 %w.h.c.) was improved by watering after sowing, but emergence was decreased in moist soil by watering within 2 days of sowing.

A seed‐borne form of Rhizoctonia solani was isolated from most seeds. Pythium, Rhizoctonia and Fusarium were commonly isolated from seedlings. Pythium was commoner at low and Fusarium at higher temperatures. Surface disinfection of seed by Spergon and Panogen compared favourably with acidulated mercuric chloride. Ascochyta on pea seed was not controlled, but all treatments except Cuprocide improved emergence of spotted pea seed. T.M.T.D., 36L and Spergon were the most efficient in controlling pre‐emergence damping off. Seed treatment was more beneficial for pea than other vegetables, but emergence was usually improved by protectants except for turnip and celery seed.

Treated seed stored dry for 10 months gave better emergence than untreated seed, and showed no evidence of diminished germination.
BACTERIAL WET ROT OF POTATO TUBERS FOLLOWING PHYTOPHTHORA INFESTANS
Authors: DOWSON W. J. , JONES D. RUDD
Published: February 2008

Potato tubers infected with Phytophthora infestans in the field produce abnormal amounts of liquid which often appear on the surface of tubers kept in a saturated atmosphere. Under these conditions a soft rot, associated with bacteria, develops.

Healthy tubers artificially infected with pure cultures of P. infestans produce a similar liquid and, if further inoculated with pure cultures of certain bacteria, develop a wet rot which spreads if the bacteria are pathogenic or is confined to the zone of fungal invasion if the bacteria are saprophytes.

Sap extracted from Phytophthora‐infected tissue contains more sugar and has a greater osmotic pressure than sap extracted from healthy tissue. Thus, water may be withdrawn from healthy tissue which would result in the infected tissue containing more liquid than does the healthy tissue.
STUDIES IN BACTERIOSIS, XXVII FACTORS INFLUENCING INFECTION BY CORYNEBACTERIUM FASCIANS (TILFORD) DOWSON
Authors: JACOBS S. E. , MOHANTY U.
Published: February 2008

Laboratory experiments showed that gram (Cicer arietinum) could be infected by Corynebacterium fascians. Parallel tests on sweet peas and gram confirmed the existence of host specificity among strains of the pathogen, and of differences in host susceptibility towards a given strain. Adventitious root formation appeared as a new, though rare, sign of infection. Inoculation of aerial dormant buds invariably caused infection whereas cotyledonary bud inoculation often failed. Sporing bacteria antagonistic to C. fascians in culture media were isolated from soil, but they failed to exert their influence in infection experiments in sand.
THE EFFECTIVENESS OF STRAINS OF THE NODULE ORGANISM WHEN ASSOCIATED WITH DIFFERENT SPECIES OF CLOVER
Authors: BOND G. , McGONAGLE M. P.
Published: February 2008

The effectiveness in nitrogen fixation of fifty‐four strains of the clover nodule organism has been tested on red, white and alsike clover in aseptic tube‐culture by comparing the nitrogen content of nodulated plants grown on nitrogen‐free medium against that of non‐nodulated plants grown on media with and without nitrate‐nitrogen. The performance of the strains was to a considerable degree consistent on all three hosts. Minor changes were shown but for the most part did not exceed the experimental error. Thus in respect of these three clovers there is no marked host species effect. Seed inoculants or naturally occurring strains effective on one species are likely to be effective on the other species.
THE EFFECT OF INFECTION WITH BEET YELLOWS AND BEET MOSAIC VIRUSES ON THE CARBOHYDRATE CONTENT OF SUGAR‐BEET LEAVES, AND ON TRANSLOCATION
Authors: WATSON M. A. , WATSON D. J.
Published: February 2008

The loss of total carbohydrate (sugars and starch) per cent of residual dry matter (dry matter less total carbohydrate) during a period of darkness from leaves of sugar‐beet plants infected with yellows virus was as great as that from the leaves of healthy plants. The conclusion of previous workers, based on the results of the Sachs iodine test for starch and the occurrence of ‘phloem gummosis’ in infected plants, that starch accumulates in infected leaves because translocation is prevented by blockage of the sieve‐tubes, is therefore incorrect.

Older leaves of infected plants had a higher content of reducing sugars and sucrose, and usually but not invariably of starch, both at the beginning and end of the dark period, than comparable leaves of healthy plants. By far the greater part of the increase was in reducing sugars. In leaves taken in late September from infected plants growing in the field, 20 % or more of the total dry matter was present as reducing sugars. The reducing sugars in both healthy and yellows‐infected leaves were shown by paper chromatography to be glucose and fructose in approximately equal amounts.

Accumulation of carbohydrate in infected leaves is probably not a passive consequence of differences in carbohydrate production, distribution and utilization, but is attributable to changes in the physiology of the cells of the leaf.

The carbohydrate content of sugar‐beet leaves was little affected by infection with beet mosaic virus.

Yellows‐infected leaves had a lower water content per cent of fresh weight than healthy leaves. This was accounted for by the higher carbohydrate content of infected leaves, for the ratio of water: residual dry matter was not affected by infection or was slightly reduced. This implies that hydration was independent of carbohydrate content.
DEPOSITION OF AIR‐BORNE LYCOPODIUM SPORES ON CYLINDERS
Authors: GREGORY P. H.
Published: February 2008

For the study of deposition of air‐borne particles on plant and trap surfaces a small wind tunnel has been constructed giving turbulent or streamline flow up to about 10 m./sec. The efficiency with which cylinders of from 0.018 to 2.0cm. diameter, coated with glycerine jelly, catch Lycopodium spores at wind speeds over the range 1–10 m./sec. has been measured experimentally with a Cascade Impactor, operated iso‐kinetically, as standard. Efficiency has been found to increase as wind speed increases, and as cylinder diameter decreases. Similar effects have been observed in the field. Efficiencies observed are lower than predicted by Sell and Glauert, but agree well with those predicted by Langmuir and Blodgett, except with the narrowest cylinders. The standard vertical sticky traps used in routine trappings of fungus spores, pollen, and crop‐protectant sprays and dusts have a low trapping efficiency.
RESOLUTION OF STRAWBERRY VIRUS COMPLEXES IV. THE LATENT PERIOD OF VIRUS 3 IN THE VECTOR
Authors: PRENTICE I. W. , WOOLLCOMBE TAMSYN M.
Published: February 2008

From the time of first feeding on plants infected with strawberry virus 3, 10–19 days elapsed before Capitophorus fragariae became infective, a longer ‘latent period’ than any previously recorded for an aphid‐transmitted virus. The time taken for aphids to develop infectivity after leaving infected plants decreased with increasing duration of the infection feed. Aphids which had fed for 16 days on an infected plant caused infection in the first day of test feeding.
FACTORS AFFECTING THE BEHAVIOUR AND ACTIVITY OF THE CABBAGE ROOT FLY (ERIOISCHIA BRASSICAE BCHÉ)
Authors: MILES MARY
Published: February 2008

The behaviour of cabbage root flies is governed by their need for food and shelter. Captive flies fed on sugar solution lived for periods up to 62 days, and a bred female laid 122 eggs.

Weather conditions determine the activity and the length of life of the flies. Feeding and egg‐laying occur in warm sunny weather, and long periods of sunshine with temperatures of at least 60° F. in the latter half of April are associated with the onset of attack on the host plants. In cold or wet weather the flies shelter in soil or in thick herbage, and if they are immobilized for some time they die of starvation. In this way, the onset of cold weather checks the development of cabbage root fly attack. Details are given to show how the weather affected the activity of the flies in the springs of 1948–50 inclusive.

Eggs are laid in batches of varying size at irregular intervals during approximately 4 weeks. The position of the eggs about the host plants is affected by weather conditions. They are usually laid in the soil, but when the pressure of sunshine and drought is removed they are laid freely on aerial parts of the plants.

Knowledge of the influence of the weather on the activity of the flies enables attack to be anticipated with some degree of accuracy and control measures to be carefully timed.
THE EFFECT OF TEMPERATURE ON THE DEVELOPMENT OF THE POTATO‐ROOT EELWORM, HETERODERA ROSTOCHIENSIS
Authors: FENWICK D. W.
Published: February 2008

Experiments on the effect of temperature on the development of Heterodera rostochiensis are described. Temperatures above 20° C. slightly reduce penetration of larvae into the potato root and greatly restrict their development in the plant tissues. The temperature range of this parasite is compared with that of H. marioni, and a possible relationship to their geographical distribution is discussed.
THE REACTION OF VIRUS‐INFECTED POTATO PLANTS TO PHYTOPHTHORA INFESTANS
Authors: MÜLLER K. O. , MUNRO J.
Published: February 2008

The growth of Phytophthora infestans was retarded on leaves of potato plants that had been artificially inoculated with virus X or with virus Y.

Using different virus strains and potato varieties, the effect of virus infection on blight development was found to be greater, the more severe the systemic virus symptoms exhibited on the infected leaves before P. infestans inoculation.

The development of the fungus was never increased by virus infection.

The reduced blight development on virus‐infected leaves is partially caused by an increase of resistance to infection. It is also suggested that virus infection alters the nutritional status of leaves to one less favourable for the development of P. infestans.
VIRUS DISEASES OF CACAO IN WEST AFRICA VIII. THE SEARCH FOR VIRUS‐RESISTANT CACAO
Authors: POSNETTE A. F. , TODD J. McA.
Published: February 2008

The methods used and the results of 10 years' search for cacao resistant to swollen‐shoot disease are described. Selection among the trees surviving in farms devastated by this virus disease led to the discovery of mild virus strains which can protect trees against virulent strains.

When tested by graft inoculation with virulent virus, none of the selections showed any immunity or resistance save that conferred by previous mild‐strain infection. A low degree of tolerance was found in some selections.

Local selections and a range of new introductions were tested by mealybug infection, and only types from the Upper Amazon region of Ecuador were consistently resistant to infection. This genetical resistance seems to be strongest in cacao from the Nanay peninsula, near Iquitos.
STUDIES IN RUBUS VIRUS DISEASES I. A LATENT VIRUS OF NORFOLK GIANT RASPBERRY
Authors: CADMAN C. H.
Published: February 2008

A selection of Norfolk Giant raspberry is infected with a virus transmissible by Amphorophora rubi Kalt. after short feeding periods on infected plants and persisting for at least 18 1/2 hr. in the aphid. This virus is identified with one which is carried without symptoms by Norfolk Giant and Baumforth's Seedling B, and causes necrosis on Rubus henryi and mosaic symptoms on R. saxatilis, American black raspberry R. occidentalis (var. Cumberland) and the red raspberry varieties Chartham, Mailing Landmark and St Walfried. The virus is present in some commercial stocks of Baumforth's Seedling B, Burnetholm Seedling, and the Mailing varieties Enterprise, Notable and Promise. The name raspberry leaf mottle is proposed.
MUSTARD OILS AND CONTROL OF THE POTATO‐ROOT EELWORM, HETERODERA ROSTOCHIENSIS WOLLENWEBER: FURTHER FIELD AND LABORATORY EXPERIMENTS
Authors: ELLENBY C.
Published: February 2008

Allyl isothiocyanate has already been shown to be effective against the potato‐root eelworm. Experiments are described in which this mustard oil, which occurs in the seed of black mustard, is compared with two similar substances; one, phenyl isothiocyanate, is synthetic, the other, phenethyl isothiocyanate, occurs in the roots of many crucifers, including black mustard.

In hatching experiments, various concentrations of each of these oils in potato‐root excretions are used to stimulate eelworm cysts. The earlier results with allyl isothiocyanate are confirmed; it is also shown that the emergence of larvae decreases with increasing concentration of oil. An experiment in which different concentrations of oil are used in different strengths of root excretions showed that it is unlikely that there is any stoichiometric interaction between root excretions and mustard oil.

Field experiments were carried out in different years and on different plots so that their comparison is difficult. But they appeared to show that talc is inferior to peat as a carrier for mustard oil. A comparison of the three oils on talc gave no significant improvement in yield, although plants treated with the allyl oil did best. In another trial with allyl isothiocyanate on talc, highly significant improvements in yield were obtained at dosages of 8 and 12 g. per row of ten plants, but the improvements were smaller than those reported previously for oil on peat. In a peat experiment on a plot giving the poor control yield of 4 oz. a plant, yield increased regularly with dosage and was almost trebled at 9 c.c. of oil per row of ten plants. On a plot with control yields of over 20 oz. a plant, 6 c.c. of oil per row increased yield by over 50%. It is shown that the increased yields are almost certainly due to a reduction in the severity of the attack, i.e. that the laboratory hatching trials ‘explain’ the field results. Although the cyst counts reported are by no means beyond criticism, they show conclusively that treated plants producing heavier crops of potatoes bear fewer cysts than control plants with lower yields.

There is a suggestion that polyploidy may be induced by certain dosages of allyl isothiocyanate.
A SIMPLE METHOD FOR TESTING THE TOXICITY OF VOLATILE ANTISEPTICS TO WOOD‐ROTTING FUNGI
Authors: FINDLAY W. P. K. , VERNON J. W.
Published: February 2008

Methods used for determining toxicity of volatile compounds to fungi are reviewed and a simple laboratory method for carrying out such tests is described.

Results from this type of test may be applicable in practice where the mycelium of the fungus is freely exposed to the action of the vapour, but if it is desired to sterilize infected wood of any appreciable thickness, information about the penetration of the vapour across the grain of the wood and of its sorption by the wood must be obtained before any treating schedule can be drawn up.
THE BIOLOGY OF THE RICE WEEVIL, CALANDRA ORYZAE (L.)
Authors: HOWE R. W.
Published: February 2008

The length of the developmental instars of Calandra oryzae has been estimated at relative humidities of 50, 60, 70 and 80% at 21° C., at 70% at 18, 25 and 30° C., and at 80% at 18° C., by the dissection daily of samples of infested wheat‐grains. The results are expressed as a median obtained by the method of probit analysis. Comparison of this method, with estimates of median and mean obtained by orthodox arithmetical methods from similar work on Rhizopertha, show that the probit method gives good estimates.

About 90% of the eggs laid are fertile. Normally only one adult will develop in a grain, all other individuals being destroyed by cannibalism. The sex ratio is unity. It was not possible to cross C. oryzae and C. granaria.

The daily oviposition rate of C. oryzae at 17, 21 and 25° C. increases with relative humidity. There is a critical point at about 60%r.h. below which egg laying declines rapidly, and mortality is high. At 100%r.h. the oviposition rates per female per day are approximately 1.3, 2.5 and 3.4 at 17, 21 and 25° C. respectively.

In experimental conditions most eggs per grain are obtained by giving isolated females one grain each, but more eggs are laid by females given more than one grain. Daily egg output is reduced by grouping females or including males. In culture, depths of grain up to 7 cm. do not discourage egg laying.
THE ECOLOGY OF ANISOPUS FENESTRALIS SCOP. (DIPTERA) IN SEWAGE BACTERIA BEDS
Authors: HAWKES H. A.
Published: February 2008

The assessment of populations of Anisopus fenestrate (Scopoli, 1763) in sewage bacteria beds by the trapping of adults at the surface has been previously proved to be unsatisfactory. Methods were therefore developed for determining the numbers of egg masses, larvae and pupae as well as the total organic matter in a unit volume of bed. The relative larval populations of three areas under investigation were related to the loading of the beds as measured by the sewage strength and rate of application. In the upper 2 ft. 6 in. the numbers of larvae and pupae per unit volume of bed decreased with depth. There was no evidence of any vertical migration of the larvae before pupation. The horizontal distribution of larvae was found to be affected by the method of distribution. In beds served with fixed spray jets larvae are more abundant nearer the jets than at some distance away. In beds served with travelling distributors the larvae are more abundant in the zones below the jets than in the drier intermediate zones. In both cases relatively higher percentages of pupae in the drier zones might indicate a horizontal migration of larvae before pupating or of the pupae themselves.

The incidence of the larvae throughout 1949 in all three beds showed recurring peaks. In the following year a more intensive investigation on one area showed that this was due to successive generations of the fly; the proximity of the peaks is determined mostly by temperature and their size by the amount of food available in the bed during the larval grazing phase.

In the area not treated with insecticide intraspecific competition during a period when food was limiting, due to depletion by the previous generation, resulted in a natural reduction in the population. In the area treated with insecticide the food was retained and this natural control was thereby delayed.
DRY‐ROT DISEASE OF THE POTATO*
Authors: FOISTER C. E. , WILSON A. R. , BOYD A. E. W.
Published: February 2008

A study has been made of the incidence of dry rot in seed potatoes in relation to commercial handling methods, and it has been shown that infection following grading by mechanical reciprocating riddles fitted with bare wire screens is more serious than that following normal handling at harvest or during transport. Hand picking, hand riddling and the use of rubber‐spool graders or rubber‐coated screens reduced infection by varying amounts. The higher incidence of the disease in ‘transported’ as against ‘home‐saved’ seed is regarded as being due to machine grading of such stocks some months prior to planting.

Contamination of stores or boxes has not been found to play any material part in the spread of infection under commercial conditions unless tubers are roughly handled during storage. As contact infection has been found to be rare, it is considered that the practice of ‘picking over’ stocks during the winter to remove diseased tubers is unnecessary and may lead to further infection.

In addition to wounds, lesions of both blight and powdery scab, but not common scab, have been found to be a means of infection.
DRY‐ROT DISEASE OF THE POTATO
Authors: McKEE R. K.
Published: February 2008

Examination of 144 samples of seed potatoes affected with dry rot, comprising 1218 tubers, showed the presence of parasitic Fusaria in 91% of the lesions. The parasitic Fusaria consisted of 93%Fusarium caeruleum, 6%F. avenaceum and less than 1% each of F. arthrosporioides and F. tricinctum. F. tricinctum has not previously been recorded on potato in this country.

A method is described whereby the presence of F. caeruleum can readily be detected in tubers affected with dry rot.
DRY‐ROT DISEASE OF THE POTATO
Authors: McKEE R. K. , BOYD A. E. W.
Published: February 2008

Living tubers were inoculated by a standard method with small quantities of the soil to be tested and held under conditions suitable for infection. The number of dry‐rot lesions that developed was regarded as giving a measure of the soil infectivity; this number, expressed as a percentage of the total number of inoculations, was termed the ‘Infectivity Index’ of the soil.

In these experiments, 91% of the lesions were caused either by Fusarium caeruleum or by a few other Fusarium species of which much the most common was F. avenaceum. In most instances it proved possible to distinguish the lesions caused by these two groups of fungi in tubers of the variety Doon Star by the colour of the rotted tissues as seen on cutting; isolations showed that 85% of the separations made in this way were correct.

Data are given indicating the sensitivity and consistency which may be expected from the method.
STUDIES IN RUBUS VIRUS DISEASES II.
Authors: CADMAN C. H.
Published: February 2008

Three diseases characterized by vein chlorosis of varying grades of severity are shown to be graft transmissible to a wide range of raspberry varieties. The diseases are thought to be caused by related strains of a virus transmissible by Doralis (Aphis) idaei V. d. G. and rarely, if at all, by Amphorophora rubi Kalt. It is proposed to refer to the diseases and viruses respectively as mild, moderate and severe vein chlorosis.
STUDIES IN RUBUS VIRUS DISEASES
Authors: CADMAN C. H.
Published: February 2008

A chlorotic veinbanding disease of raspberries is shown to be due to a virus transmissible by the aphid Amphorophora rubi Kalt. after infection feeding periods of 18 hr. or more.

This virus causes leaf symptoms, masked in hot weather, on a wide range of European and North American varieties. Symptoms on the latter are analogous to those of the red raspberry mosaic of American authors.

The names veinbanding disease and raspberry veinbanding virus are proposed.
STUDIES OF THE CLOVE TREE
Authors: SHEFFIELD F. M. L.
Published: February 2008

Experimental grafting between cloves is very difficult with shoots, and so far has proved impossible with roots. Use has therefore been made of naturally occurring grafts in the study of sudden‐death disease. Volunteer seedlings often grow up closely adpressed to old trees. If the old tree dies from sudden‐death disease, the pole† usually survives, but occasionally it dies almost simultaneously with the old tree. The poles discussed invariably had an independent root system, but those which died were found to have their roots grafted to those of the old tree whilst poles which survived, although closely adpressed to the old tree, had no organic connexion with it. These observations cannot be reconciled with any but a pathogenic hypothesis as to the nature of the sudden‐death disease.
THE COMPETITION BETWEEN BARLEY AND CERTAIN WEEDS UNDER CONTROLLED CONDITIONS
Authors: MANN HAROLD H. , BARNES T. W.
Published: February 2008

One of the commonest agricultural practices in Britain is the undersowing of barley and other corn crops with clover as a preparation for a clover ley after the corn crop has been reaped. The effect of the clover growing among the corn, where manuring (especially with nitrogen) is made as favourable as possible for the corn crop, is not clear. If nitrogen is deficient, it is well known that clover can furnish nitrogen for the corn, but where the supply is ample, the clover may act as a competitive crop.

When barley and clover were planted together, with abundance of water and nutrients for both, it was found that the presence of even a small number of barley plants reduced the growth of the clover by over 50%, but that an increase in the density of the barley did not increase the effect. The presence of the clover reduced the barley crop by an amount which tended to get less as the density of the barley was increased. In a sparse crop of barley, increase in clover density reduced the growth of barley very little, while that of the clover was again found to be little more than half what was obtained when this plant was grown alone.

There is no evidence of any specific effect of the roots of the one plant on the other. In the circumstances of these experiments it would seem that, far from the clover supplying nitrogen to the barley, it tends to steal some of that which would otherwise be available to the latter, when they are grown together.
VARIATION WITHIN FRENCH BEAN VARIETIES
Authors: BATEMAN A. J.
Published: February 2008

The internal variability of several varieties and strains of French bean is investigated, confining attention to the single character, seed weight. Out of eleven strains examined only two appeared to be homogeneous for seed weight, whilst two were obviously heterogeneous even by superficial examination of the seed.

A comparison of the distribution of seed weights in five strains of Canadian Wonder showed that each strain contains at least two or three lines out of the minimal estimate of four shared between them.

The natural out‐crossing of fourteen varieties, including those analysed for seed weight, is compared. There are indications that varieties vary in their out‐crossing propensities. No indication was found of the causes of the high frequencies of out‐crossing occasionally encountered.

The possible sources of intra‐varietal variation are briefly surveyed.
ASPECTS OF THE PHYSIOLOGY OF THE SHEEP TICK
Authors: Lees A. D.
Published: February 2008

Recent work on the ecology of the sheep tick has posed many problems of a physiological nature that could best be investigated by laboratory or by combined laboratory and field studies. Three subjects of relevance to sheep tick ecology are briefly considered in the following paragraphs.
THE PHYTOTOXIC PROPERTIES OF ALTERNARIC ACID IN RELATION TO THE ETIOLOGY OF PLANT DISEASES CAUSED BY ALTERNARIA SOLANI (ELL. & MART.) JONES & GROUT
Authors: BRIAN P. W. , ELSON G. W. , HEMMING H. G. , WRIGHT JOYCE M.
Published: February 2008

Alternaric acid, a metabolic product of some strains of Alternaria solani, is highly phytotoxic. If introduced into the vascular system of cut shoots of tomato or potato, it travels upwards and causes necrotic lesions of the stem, petioles and leaf blades, very similar in appearance to the lesions appearing in some phases of natural attack by A. solani. Alternaric acid also produces similar lesions on plants outside the host‐range of A. solani. Associated with the production of visible lesions is a disturbance of the water‐balance of shoots. Transpiration is increased and, in spite of a simultaneous but smaller increase in water uptake, this eventually leads to complete desiccation of the shoots. A strain of A. solani known to produce alternaric acid in synthetic culture media produces a substance with similar biological properties when inoculated into tomato fruits. Since other workers have shown that some of the symptoms of A. solani attack are toxigenically induced, it is tempting to suggest that alternaric acid is the toxin concerned. On the other hand, there is no correlation between virulence of strains of A. solani and their ability to produce alternaric acid in synthetic culture media or in tomato fruits. Some highly virulent strains produce little or no alternaric acid under any conditions tested. There is some evidence that other toxins beside alternaric acid are produced by A. solani, not necessarily in the same proportions by all strains.
DRY‐ROT DISEASE OF THE POTATO
Authors: BOYD A. E. W.
Published: February 2008

The standard injection method of inoculation was used in conjunction with the riddle‐abrasion method, at three periods during the storage season, to determine the effect of storage of potatoes of three varieties at three temperatures or ranges of temperature upon their subsequent susceptibility to Fusarium caeruleum.

Susceptibility was greatly increased by increase in storage temperature. Low‐temperature storage (39°F.) before inoculation decreased susceptibility. If, however, such storage immediately followed inoculation, although little or no signs of rotting were obvious after 6 weeks, when these tubers were replaced for a further 6 weeks at the normal temperature of incubation (60°F.) the amount of rotting was enhanced.

Some practical consequences of these facts are discussed.
STUDIES OF FLUCTUATIONS IN INSECT POPULATIONS XIII. AN IMPROVED METHOD OF ASCERTAINING THE CORRECT DATE TO SAMPLE WHEN ASSESSING LARVAL INFESTATIONS OF THE WHEAT‐BLOSSOM MIDGES
Authors: BARNES H. F.
Published: February 2008

Fully fed larvae of the wheat‐blossom midges need moist conditions in order to descend from the ears to the soil. A dry spell coinciding with the fully fed stage therefore causes an accumulation of larvae, which subsequently leave the ears in a body when rain comes. Conversely, in wet weather each larva leaves the wheat as soon as it finishes feeding, and, since all the eggs are not laid on the same day, the descent will then be a gradual process.

A method is described of taking small samples of wheat ears at frequent intervals, thus facilitating the determination of the correct date on which to take the main sample for the assessment of infestation by the two wheat‐blossom midges.
FURTHER OBSERVATIONS ON THE BIOLOGY OF THE CABBAGE ROOT FLY, ERIOISCHIA BRASSJCAE BCHÉ
Authors: MILES MARY
Published: February 2008

In 1951, eggs of Erioischia brassicae were first found in the field on 2 May, and the peak period of egg‐laying occurred 19–31 May. This was up to a month later than in the period 1948‐50.

The periodic removal and examination of the surface soil showed that eggs of E. brassicae were continuously present on the host plants from mid‐June to early November. Plants under observation during this period showed an average of 285 eggs per plant and other plants exposed to attack from July to November showed an average of 162 eggs per plant. Peak periods of egg‐laying, as indicated by numbers of eggs per plant per day, occurred in late June and early July, in mid‐August and, to a less extent, in the first half of October. The plants showed no increase in the rate of infestation as the season advanced, although E. brassicae has a reproductive capacity of about 100 eggs per female and three to four generations a year.

The difference between the observed egg populations and pupal populations indicated that E. brassicae had a heavy mortality rate in its immature stages. The condition of puparia showed that the species was subject to a high degree of natural control, a fact for consideration when direct control measures are formulated.

Pupal diapause extending from October 1949 to May 1951 was observed in one specimen of E. brassicae and from October 1949 to August 1951 in one specimen of its Hymenopterous parasite, Trybliographa rapae Westw.

Tests with tar‐oil winter wash showed that at a concentration of 1 1/4% it killed eggs of Erioischia brassicae and repelled gravid females for approximately a week. Laboratory tests with BHC indicated that it had no adverse effects on the eggs but was larvicidal.
THE ACTION OF METALDEHYDE ON THE SLUG AGRIOLIMAX RETICULATUS (MÜLLER)
Authors: CRAGG J. B. , VINCENT MYRTLE H.
Published: February 2008

Metaldehyde both as powder and in solution can act on slugs either by contact or as a ‘stomach poison’. The characteristic effects of metaldehyde poisoning were immobilization broken by outbursts of unco‐ordinated muscular activity and sliming which usually resulted in severe water loss. 24 hr. after treatment with moderate doses slugs were still abnormal and rarely fed within 30 hr. of treatment. It was not possible to determine the M.L.D. with the methods used, but 0·06 nig. solid metaldehyde taken orally could be lethal to slugs of 400–800 mg. body weight. Lethal effects were produced by contact of 1 hr. with concentrations equivalent to 0·0063 mg./cm.2. Toxicity increased with rise in temperature and recovery from moderate doses was dependent on slugs being in a saturated or almost saturated atmosphere. No obvious gut lesions were found in slugs which had been dosed with or had eaten metaldehyde. Its action was not by depolymerization in the gut or body cavity. In the light of laboratory and small scale field trials it is suggested that broadcasting and spraying are the best methods of applying the material.
HERBICIDES THE RELATIVE TOXICITY OF NITROPHENOLS TO VARIOUS ORGANISMS
Authors: Simon E. W.
Published: February 2008

The effect of increasing degrees of nitration on the toxicity of phenols was assessed by measuring the toxicity of phenol, o‐ and p‐nitro phenols and 2:4‐dinitro phenol with several different test organisms. Toxicity levels were determined by the concentration required in each case to bring about the following responses: (i) to halve the rate of radial growth of Trichoderma viride at pH 3, (ii) to halve the respiration rate of yeast at pH 3, (iii) to halve the rate of frond multiplication of Lemna minor at pH 5·4, (iv) to bring about 50% mortality of seedlings of Brassica alba in a spraying test and finally (v) to halve the rate of respiration of leaf disks of B. alba vacuum‐infiltrated with the toxic solution at pH 3.