bluuebunny/crossref_metadata_2025 huggingface dataset:
STUDIES ON THE BEAN APHID (APHIS FABAE SCOP.) AND ITS CONTROL ON FIELD BEANS
Authors: WAY M. J. , SMITH P. M. , POTTER C.
Published: February 2008

Field trials on chemical control of Aphis fabae Scop, attacking spring‐sown field beans were carried out during the years 1950–2. The insecticide sprays were applied once only, soon after primary aphid migration into the bean crop had ceased. Destruction of the few aphids present at this early date stops build‐up of the big populations that often develop later.

An 0.02% (w/v) parathion spray was used in all three field trials. This gave excellent control of A. fabae as did the systemic insecticides Isopestox and Systox at 0.05% (w/v) active ingredient, and nicotine at 0.1% (w/v). Sprays containing allethrin (0.05% (w/v) pure material), pyrethrins (0.05% and 0.02% (w/v) total pyrethrins plus piperonyl butoxide) and an 0.1 (w/v) DDT emulsion gave moderate control. A. fabae was not controlled in plots treated with an 0.1% (w/v) DDT crystalline suspension, and the aphid population reached a higher peak than in the untreated plots; the suspension is not only relatively ineffective against the aphid, but is more toxic than the DDT emulsion to its Coccinellid predators.

On the bean plant the 0.05% (w/v) Systox spray showed some residual toxicity to A. fabae for at least 5 days after application, but stopped causing 100% kill within 24 hr. 0.02% (w/v) parathion and 0.1 (w/v) DDT emulsion had slight, and 0.02% (w/v) pyrethrins and 0.1% (v/v) nicotine, no residual toxicity.

In the year 1950, aphid attack on the field plots was slight and damage insignificant. In 1951, there was a moderate attack and the yield of bean seed was significantly increased by all insecticidal treatments; where aphid control was most efficient (parathion and Isopestox treatments) the yield (16.7–17.1 cwt./acre) was about × 2.7 that of the untreated control (6.3 cwt./acre). In 1952, there was severe aphid attack, and the mean seed yield of the untreated control plots was 1.4 cwt./acre. Plots treated with the DDT suspension yielded 1.3 cwt. seed/acre, but all other insecticides, including the DDT emulsion, increased the seed yield to 10.3–14.8 cwt./acre.

All preparations used in 1952, except nicotine, were destructive to adult Coccinellid predators of A. fabae; Adalia bipunctata was more susceptible than Coccinella septempunctata. However, in 1952, predators on the experimental area were too uncommon to be economically important.
EXPERIMENTS ON SPRAYING WITH DDT TO PREVENT THE FEEDING OF SCOLYTUS BEETLES ON ELM AND CONSEQUENT INFECTION WITH CERATOSTOMELLA ULMI
Authors: PEACE T. R.
Published: February 2008

Experiments were done for three years on street elms at Folkestone and Aldenham to repeat American work on the use of insecticidal sprays to prevent feeding by Scolytus beetles, which carry Ceratostomella ulmi, the cause of elm disease. Although the fungus can remain alive in the older annual rings of an infected tree, active disease usually results from fungus freshly introduced by Scolytus. Thus spraying is of value on infected, as well as uninfected elms.

The results of the experiments supported American conclusions that DDT was superior to benzene hexachloride. A 1.5% solution of DDT in miscible oil gave reasonably good, but not perfect, control, and was much superior to solutions made from DDT in the form of a dispersible powder.

Spraying of trees 20–30 ft. high cost over £1 per tree per year, which is considered prohibitive, except for small trees of special amenity or sentimental value.
THE DIFFERENT DISTRIBUTION OF TWO BRASSICA VIRUSES IN THE PLANT AND ITS INFLUENCE ON SPREAD IN THE FIELD
Authors: BROADBENT L.
Published: February 2008

Previous knowledge provided no explanation for the greater prevalence of cauliflower mosaic than of cabbage black ring spot in field crops of cauliflower. Both viruses are spread principally by Myzus persicae and Brevicoryne brassicae, and both are transmitted equally readily from infected seedlings. Cabbage black ring spot virus has a much wider host range, and sap from infected leaves has a higher dilution end‐point than sap from leaves infected with cauliflower mosaic virus.

At least part of the difference between the rate at which the two viruses spread in the field may be accounted for by the different manner in which they are distributed in old infected plants, and the effect this has on transmission by aphids. Cauliflower mosaic virus occurs in high concentration in all the new leaves produced by infected plants. Cabbage black ring spot virus, on the other hand, occurs mainly in the older leaves, and even there is localized in parts that show symptoms. Only in recently infected plants does cabbage black ring spot virus occur in young leaves.

After flying, most aphids alight on the upper parts of plants; they are therefore less likely to acquire cabbage black ring spot virus than cauliflower mosaic virus. It may be significant that cabbage, a host in which old leaves are in a more favourable position for alighting aphids than are those of cauliflower, is also often extensively infected with cabbage black ring spot virus.
STUDIES IN RUBUS VIRUS DISEASES
Authors: CADMAN C. H.
Published: February 2008

Raspberry leaf mottle virus is acquired by Amphorophora rubi in feeding periods of 1/2‐2 hr. Longer feeding periods cause no significant fluctuations in infectivity. During continuous feeding on healthy plants, infectivity declines rapidly after 2 hr., but persists for at least 5 hr. if aphids are transferred frequently to fresh healthy plants. The estimated probability of infection by single aphids is 1 in 20. Rarely more than 50% of test plants, Rubus occidentalis, seedlings became infected, and this is thought to be due mainly to variation in plant susceptibility. Young leaves of infected Norfolk Giant are, however, better sources of virus than older leaves.
THE SYSTEMIC INSECTICIDAL ACTION OF CERTAIN COMPOUNDS OF FLUORINE AND OF PHOSPHORUS ON PHAEDON COCHLEARIAE FAB.
Authors: DAVID W. A. L. , GARDINER B. O. C.
Published: February 2008

Four compounds—bisdimethylaminophosphonous anhydride (schradan), bis(dimethylamino)fluorophosphine oxide (dimefox), diethyl paranitrophenyl phosphate (paraoxon) and sodium fluoroacetate (acetate)—have been tested against the mustard beetle, Phaedon cochleariae Fab. When the four compounds are compared by a direct contact technique in which insects can also imbibe some of the test solutions, or the insects are caged with foliage which has been dipped and then dried, the order of toxicity to adults and larvae was found to be Paraoxon > acetate ≏ dimefox > schradan.

The paraoxon is very much more toxic than the other compounds. In all cases the adults are more resistant than the larvae.

When the insecticides are applied systemically the order of toxicity changes to Paraoxon > dimefox > acetate ≏ schradan because the acetate causes the plants to wilt and less of it is absorbed. Both paraoxon and dimefox give complete kills of adult Phaedon which is the most resistant stage, at practical concentrations.

When the insecticides were applied to the outer leaves and translocated to the inner untreated leaves an effect was observed with the dimefox and paraoxon after numerous application, but with a single application very inconsistent results were obtained.

It is concluded that schradan and the acetate are ineffective systemically against Phaedon. The dimefox and paraoxon are very effective, but because of their high mammalian toxicity they would require very careful handling in practice.
STUDIES IN THE ANTAGONISM BETWEEN BLASTOMYCES LUTEUS AND SPECIES OF VERTICILLIUM
Authors: ISAAC IVOR
Published: February 2008

Blastomyces luteus has been shown to be antagonistic in culture to both Verticillium albo‐atrum and V. dahliae over a wide range of temperature and irrespective of the pH value of the medium. When B. luteus is grown on Dox's and potato‐dextrose solutions it produces an exudate which, added to agar media, has an inhibiting effect upon the growth of these two species of Verticillium. The effectiveness of this inhibiting material is slightly reduced by boiling for 15 min.

When ‘spent’ Dox's liquid medium, which has supported the growth of B. luteus, is injected into tomato and antirrhinum seedlings inoculated with Verticillium no control of the disease is effected, but when B. luteus mycelium is added to soil infected with Verticillium, marked reduction in the incidence of disease results when the antagonistic organism and the pathogens have co‐existed in the soil a sufficient length of time for the exudate of the former to be effective upon the development of the latter.
THE EFFECT OF TIME OF APPLICATION OF NITROGENOUS FERTILIZER ON POWDERY MILDEW OF WINTER WHEAT
Authors: LAST F. T.
Published: February 2008

Applying nitrogenous fertilizer (N) to wheat plants of different ages affected the incidence of powdery mildew, Erysiphe graminis DC, differently. When N was applied before the flag leaf had emerged, the infection‐index (number of pustules per 100 sq.cm. of leaf blade) increased to a maximum and then declined. If N was applied after the flag leaf had emerged, the infection‐index increased steadily without reaching a peak, and the increased susceptibility was not associated with an increased relative leaf growth rate as when N was applied earlier.

The integral of the number of pustules per unit area with time, and the number of perithecia on the leaves of the main stem, both increased with increasing delay in the application of N. Plants given N in either April or May had at least three times as many pustules as those given N in January. The time when N was applied did not affect the date when perithecia appeared.

After adding N to nitrogen‐deficient plants, the already mature leaves which had resisted mildew infection, became susceptible. This change is not associated with changes in the epidermal wall.
INVESTIGATIONS ON RESISTANCE TO DISEASE AMONG SPECIES OF THE GENUS AVENA
Authors: WILLIAMS WATKIN , VERMA U. N.
Published: February 2008

Fifty‐three samples representing species of the genus Arena were tested for resistance to infection by Ustilago avenae and U. kolleri following artificial inoculation. Among the diploid and tetraploid species tested, eleven out of thirty‐seven samples of Arena strigosa subsp. strigosa showed complete resistance to all the cultures with which they were inoculated. Avena strigosa subsp. barbata (three samples), and Avena strigosa subsp. abyssinica (one sample), also proved to be resistant to all the available races.

Variation in morphological and physiological characteristics within species and samples (varieties?) of the lower chromosome groups of Avena were observed and its consequences in breeding and race identification discussed.

Race identification was carried out on the eight Ustilago cultures and the existence of at least six races established. The tester varieties used in the present study proved inadequate for the complete separation of the smut races.
DRY‐ROT DISEASE OF THE POTATO
Authors: McKEE R. K.
Published: February 2008

Inoculation of wounded tubers at intervals throughout the storage season showed that, after harvesting, resistance to infection by F. avenaceum was maintained for a longer period than resistance to F. caeruleum, although eventually the tubers became equally susceptible to both fungi. Tubers were less readily infected through clean‐cut than through scarified wounds. Resistance to infection was greater when an interval elapsed between wounding and inoculation than when the wound was inoculated immediately; this was related to an increase in the intrinsic ability of the cells near the wound to resist infection rather than to suberization of the wounded surface or wound periderm formation.

Histological studies showed that F. caeruleum grew through the intercellular spaces and that the adjacent host cells remained alive, often for considerable periods, whereas F. avenaceum killed and penetrated the cells with which it came into contact. Restriction of incipient or established lesions caused by F. caeruleum and of incipent lesions caused by F. avenaceum was associated with suberin deposition on the host cell walls and in the intercellular spaces; in established lesions caused by F. avenaceum, restriction was attributed to an increase in the intrinsic resistance of the adjacent host cells, similar to that found near a wounded surface.
HEAT‐THERAPY OF VIRUS‐INFECTED PLANTS
Authors: KASSANIS B.
Published: February 2008

Virus‐free plants were produced from parents systemically infected with the following five viruses: tomato bushy stunt, carnation ring spot, cucumber mosaic, tomato aspermy and Abutilon variegation. The leaves formed while the infected plants were kept at 36°C. were free from symptoms, and test plants inoculated from these remained uninfected. When cuttings were taken from the infected plants at the end of the treatment most grew into healthy plants. The treated plants themselves usually developed symptoms after varying lengths of time at 20°C, but some that before treatment were infected with tomato aspermy, cucumber mosaic or Abutilon variegation viruses, remained permanently healthy.

The same method failed to cure plants infected with tomato spotted wilt, potato virus X and tobacco mosaic virus, although it decreased their virus content. Heat‐therapy seems not to be correlated with the thermal inactivation end point of the virus in vitro.
THE ABSORPTION, TRANSLOCATION AND BREAKDOWN OF SCHRADAN APPLIED TO LEAVES, USING 32P‐LABELLED MATERIAL
Authors: BATT R. F. , BENNETT S. H. , THOMAS W. D. E.
Published: February 2008

The methods of propagation of plant material for experimental use, the procedure for preparing the radioactive solution, and its application to leaves either by dipping or spraying are described.

A description is given of the conditions under which the plants were kept, the procedure adopted at sampling involving leaching of the treated leaves, subdivision of the plant and preparation of samples for determination of ‘schradan’ and ‘schradan equivalent’ by liquid counting.

The methods of compiling results to determine the distribution and status of the applied schradan in or on the leaves at harvest, are outlined.
THE BIOLOGY AND CONTROL OF OTIORRHYNCHUS CLAVIPES BONSD. (RHYN. COLEOP.), A PEST OF STRAWBERRIES
Authors: IBBOTSON ALAN , EDWARDS C. A. T.
Published: February 2008

Otiorrkynchus clavipes Bonsd. is a serious pest of strawberries around Cheddar, Somerset. The weevils nibble the foliage, the larvae eat the roots of the plants, and burrow into the rootstock.

The beetles appear in two waves, pupating in the autumn and emerging en masse in the spring, or pupating in the late spring and summer and emerging in succession between mid‐June and the end of August. Both sexes are found and can be distinguished by the posterior thoracic sterna, which are concave in males and convex in females. Mating is alternated with egg‐laying and the beetles lay between 100 and 300 eggs per female. On emergence the beetles eat voraciously, and roughly one egg is laid for every 10 sq.mm. of leaf consumed. Both parthenogenetic and fertile eggs are laid and hatch in between 17 and 24 days.

The larvae burrow rapidly when hatched and can only penetrate soil spaces which will admit their head capsules. The distribution of head capsule widths in mixed populations of larvae of all ages shows there are five instars. While feeding, the larvae are clustered within the root range of the plants and find their way to their food from plant to plant, guided by the exudates from the strawberry roots. As the larvae grow older they descend in the soil and turn to white soft pupae in smooth earthen cells 6–8 in. below the plants.

Adult damage to foliage is unimportant but larval damage to roots is serious and has been largely responsible for restricting the effective life of the strawberry beds to at most 2 years. Although weevil attack can be avoided by growing the crop in a 1‐year rotation, control is difficult owing to the intensive cropping, which creates the most suitable conditions for the spread of the infestations. The adults are killed with 10% DDT dust; and the larvae by DDT and BHC preparations poured on to the soil, at a pint per plant, or by DD injection. The limitations and possibilities of various methods of control are discussed.
PROVISIONAL LISTS OF HOST PLANTS OF SOME ROOT EELWORMS (HETERODERA SPP.)
Authors: WINSLOW R. D.
Published: February 2008

In host‐range tests carried out at Cambridge, 1951‐3, beet eelworm was found to parasitize nearly all Cruciferae tested, while other hosts were found amongst the Amaranthaceae, Caryophyllaceae, Chenopodiaceae, Labiatae, Phytolaccaceae, Polygonaceae, Scrophulariaceae and Tropaeolaceae. Cabbage eelworm parasitized nearly all Cruciferae tested, and a few Labiatae. Hosts of Galeopsis and clover eelworms were found amongst the Caryophyllaceae, Labiatae, Leguminosae, Polygonaceae and Scrophulariaceae. Potato eelworm cysts were found only on Lycopersicum and Solanum; carrot eelworm only on Daucus; and hop eelworm only on Urtica (Urticaceae) and Cannabis and Humulus (Cannabinaceae). Pea eelworm appeared to parasitize only the genera Lathyrus, Lens, Pisum and Vicia (Leguminosae), while hosts of oat eelworm appeared to be distributed more or less at random within the Gramineae.
THE ANTIBIOTIC ACTION OF BACILLUS SUBTILIS IN RELATION TO CERTAIN PARASITIC FUNGI, WITH SPECIAL REFERENCE TO ALTERNARIA SOLANI (ELL. & MART.) JONES & GROUT
Authors: VASUDEVA R. S. , CHAKRAVARTHI B. P.
Published: February 2008

The culture filtrate of a strain of Bacillus subtilis is shown to be antagonistic to the growth of Rhizoctonia solani, R. bataticola, Alternaria solani, Botrytis cinerea, Fusarium udum, and Colletotrichum falcatum, exhibiting specificity of action. Malformation of the germ tube of Alternaria solani spores resulting in ‘bulb’ formation is also reported. Diffusion of the antibiotic principle inside host tissues is indicated.
A SURVEY OF WILD OATS (AVENA FATUA AND A. LUDOVICIANA) IN ENGLAND AND WALES IN 1951
Authors: THURSTON JOAN M.
Published: February 2008

In 621 samples of wild oats, collected in England and Wales by N.A.A.S. and N.I.A.B. Officers, only two species (Avena fatua and A. ludoviciana) were found but both were very variable. A. fatua occurred in all wheat‐ and barley‐growing areas, in both winter and spring corn and on all soil types. A. ludoviciana occurred (with two exceptions) only within approximately 80 miles radius of Oxford, mainly on heavy soila and chiefly in winter corn.

The amount of wild oats present appeared to depend on the frequency in the rotation of corn or other crops in which wild oats would shed seed. Deep ploughing often increased the infestation. The data did not show whether a field could be freed of wild oats by grassing down for a number of years, nor what is the maximum period of survival of buried wild oat seeds.
STUDIES ON THE SYNERGISTIC EFFECT OF PIPERONYL BUTOXIDE AND ISOBUTYLUNDECYLENEAMIDE ON PYRETHRINS AND ALLETHRIN
Authors: NASH RUTH
Published: February 2008

Experiments are described to compare the toxicity of natural pyrethrins and allethrin, the completely synthetic homologue of cinerin I, and to show the effect of the two synergists, piperonyl butoxide and iaobutyl undecyleneamide (IN 930) on both these active ingredients, using a measured‐drop technique with Mucca domestiur L. the housefly, and a residual‐film technique with Cimex lectularius L. the bed bug. In the conditions of the experiment, pyrethrins were shown to be twice as toxic as allethrin to flies, and 5.5 times as toxic as allethrin to bugs. The two synergists were tested at several ratios to the two insecticides, ranging from 1 : 1 to 20 : 1. The results were plotted as series of log. concentration/probit regression linea. These were parallel for the bug tests; but in the fly tests, the slope of the line increased with a rise in the proportion of Synergist to insecticide. The estimated median lethal concentrations indicated, in all cases, that the toxicity increased with a rise in the ratio of synergist to insecticide, at least up to 20 : 1. However, the enhancement of toxicity was greatest for the smaller ratios and fell off as the ratio increased. Piperonyl butoxide was the more powerful synergist, increasing the potency of pyrethrins 5 times and allethrin 4 times to flies, and pyrethrins twice and allethrin 3 times to bugs, whereas IN 930 did not increase the potency of either ingredient more than twice to either test insect.

The addition of piperonyl butoxide to residual films of pyrethrins greatly prolonged their effectiveness; but an experiment designed to investigate the effect of the synergist on the stability of this insecticide showed that this action, if it exists, must be slight.
PRELIMINARY STUDIES ON POTATO APHIDS IN NORTH AND NORTH‐EAST SCOTLAND
Authors: SHAW M. W.
Published: February 2008

Studies of potato aphids made in the potato seed‐growing areas of north and north‐east Scotland during 1950‐3 showed that potato plants were first infested during July, but with few aphids; maximum populations did not develop until mid‐late August or early September, which is the period of potato haulm destruction in seed crops. Myzus persicae (Sulzer) was scarce in rural districts and most numerous near urban areas. The main influx of alatae occurred in early August. Aulacorthum solani (Kltb.) was the predominant species north of Inverness. Macrosiphum euphorbiae (Thomas) was present in small numbers in many potato fields, but Aphis nasturtii (Kltb.) was extremely scarce.

Because of the small numbers of aphids found during two years by examining two or three compound leaves per haulm, it was preferable to count the aphids on one main stem and all its leaves.

Stove‐pipe sticky traps provided information complementary to complete stem/leaf examination, but are considered to be of doubtful use in an area where aphids are few.
THE DEVELOPMENT OF LARGE SUCTION TRAPS FOR AIRBORNE INSECTS
Authors: JOHNSON C. G. , TAYLOR L. R.
Published: February 2008

Small suction traps for estimating the density of airborne insects, and its fluctuations, in relatively sheltered situations, e.g. in crops, have already been designed and used.

Larger, more powerful traps have now been developed for use in more exposed situations where insect densities are very low, or where winds are relatively strong, e.g. high in the air. Because of the large sample obtained they also enable very short‐term density fluctuations to be followed.

The radical modifications of design and the special problems encountered in the operation of very large traps are described.
THE EFFECTS OF INSECTICIDE TREATMENT ON THE MACROFAUNA POPULATIONS, FILM ACCUMULATION AND EFFICIENCY OF SEWAGE PERCOLATING FILTERS
Authors: HAWKES H. A.
Published: February 2008

In an attempt to replace the laborious method of assessing macrofauna populations of sewage filters, which involves the separation of the macro‐organisms from unit volumes of stone samples excavated from the filters, it was found that the numbers of Anisopus fenestrate (Scopoli, 1763) larvae taken weekly during 1951 in baited traps placed in the filters were greatly affected by the amount of available food within the filter. A method involving separation by flotation was, however, evolved for the rough estimation of Collembola.
THE LOSS OF WEIGHT OF PYRETHRIN‐TREATED FLOUR BEETLES, TRIBOLIUM CASTANEUM (HERBST), AND ITS APPLICATION TO BIOASSAY
Authors: HEWLETT P. S. , GOSTICK K. G.
Published: February 2008

Pyrethrin‐treated flour beetles, Tribolium castaneum (Herbst), lose weight rapidly. The weight lost by batches of beetles, a readily determined graded response, has been investigated with a view to its use in bioassay. Strong evidence was obtained that (1) in pyrethrum extracts only the pyrethrins cause the loss, and that (2) the other extractives do not modify the loss caused by the pyrethrins. Allethrin also caused a rapid weight loss; piperonyl butoxide, by itself producing little loss, greatly increased the loss caused by pyrethrum solutions and by allethrin, paralleling its effects on toxicity. The pyrethrin content of solutions appeared to account quantitatively for their weight‐reducing activities; irradiation of pyrethrum solutions that destroyed their toxicity also destroyed their weight‐reducing properties; and neither pyrethrum oleoresin heat‐treated to destroy the pyrethrins, nor irradiated solutions, modified the weight loss due to allethrin.

Factors influencing weight loss were investigated. Beetles were exposed, mostly for 3 hr. at 25°C., on hard filter‐papers treated with solutions of pyrethrins in a non‐volatile oil (Shell Risella oil 17, formerly called P31). At fixed deposit the loss rose sigmoidally with increasing pyrethrin concentration from about 0.7 % for zero concentration to an upper limit of about 6.5 % of initial beetle weight. A log‐logit transformation made the sigmoid curve linear. The carrier oil and the length and temperature of the exposure to the pyrethrins influenced the weight loss. At 25°C, the rate of air movement and the relative humidity between 40 and 90% did not. Pyrethrins in Risella oil 17 could be applied satisfactorily to the filter‐papers by means of a spraying tower, or by pipette if the solutions were first diluted with a volatile solvent, which was allowed to evaporate subsequently. Deposits of given pyrethrin content were about 1.3 times as active in producing a weight loss if prepared by spraying than if prepared by solvent evaporation.

The technique, design, and analysis of results, for bioassays based on weight loss are described. The most elaborate method of analysis ever likely to be needed is given, with a worked example, but a considerably simpler method, only slightly longer than the probit analysis for quantal‐response assays, would probably suffice normally.

For a given number of beetles used, the weight loss method of assay has about the same inherent precision as the film method of Parkin & Green (1943), but is less precise than the direct spray method of Hewlett (1947). However, larger numbers of beetles can be used in the new method, the assessment of the insecticidal effect is more objective, and results are obtained more quickly y‐BHC and DDT cause T. castaneum to lose weight less rapidly than do pyrethrins.
A FURTHER STUDY OF THE TOXICITY OF POTASSIUM CYANIDE TO RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON)
Authors: HERBERT D. W. M. , DOWNING KATHLEEN M.
Published: February 2008

The distributions of the periods of survival of individual rainbow trout in solutions of potassium cyanide are asymmetrical and approximately log‐normal within the range of concentration where the relation between log time and log concentration is linear, whereas they are symmetrical and approximately normal at higher concentrations.

Some inherent, persistent features possessed by the fish influence survival time in both the higher and lower ranges of concentration, but other such features exert a significant influence only in the lower concentrations.

Some of the features influencing survival time in the lower concentration range only, are associated with body size.
AN EXPERIMENT IN RABBIT CONTROL
Authors: PHILLIPS WINIFRED M.
Published: February 2008

A successful experiment in rabbit control was carried out over one year on a 300‐acre farm in Pembrokeshire. The control measures adopted were trapping, gassing and ferreting, in that order. Information on rabbit density was based primarily on counts of rabbit holes and on the number of animals caught. Observations were made on the breeding state and sex ratio of the population. Successful control was attributed to the persistent application of a variety of methods, and not to any one method in particular. Gassing was equally efficient on high and low rabbit populations; the three methods of application, namely pumping, spooning and a combination of both, were found to be equally effective. Re‐infestation occurred, but was checked to some extent by trapping around the boundary.

The breeding season appeared to extend from January to June, inclusive. The sex ratio was biased in favour of females throughout the experiment. An almost even sex ratio was observed in embryos.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Authors: SEELEY R. C. , WAIN R. L.
Published: February 2008

Application of some growth substances markedly stimulated flowering laterals of the hop plant. The effect was specific to certain compounds and varied between varieties of hops and in the stage of flower development. The initial stimulation was not maintained by repeated application of the chemical, and untreated control laterals yielded a greater weight of cones with a higher soft resin content.
THE EPIDEMIOLOGY AND CONTROL OF NOSEMA DISEASE OF THE HONEY‐BEE
Authors: BAILEY L.
Published: February 2008

The proportion of honey‐bees infected with Nosema apis (Zander) declines in summer as the old infected bees die, for they cease to transmit their infection to the newly emerged individuals during the flying season. N. apis spores survive the summer on combs contaminated with infected faeces during the preceding winter. Although bees clean the combs during the summer, all infected material is not removed, and even well‐used brood comb, which has been repeatedly cleaned by bees, can carry infection. Only a few bees may contract infection in the autumn from these faeces, but they join the winter cluster and initiate the next outbreak of the disease. Transferring a colony on to clean comb early in the spring or summer removes the source of the disease, and it then disappears when all the old infected bees die.

Old broodless comb can be sterilized quite simply by fumigation for a few days with the vapours of formalin or glacial acetic acid. Acetic acid is preferable, because it does not poison any honey or pollen in the combs. Formaldehyde can safely be used only with empty combs.

The autumn is the best time for treating colonies chemotherapeutically, because the combs are then cleanest and the few bees which are infected can be cured during the winter. The drug can be incorporated in the syrup normally fed to colonies in autumn, and there is no risk of seriously contaminating subsequent honey crops. However, such treatment cannot eliminate the disease because sufficient spores remain on the combs for the disease to start again when the drug supplied in the winter stores is exhausted.
THE STANDARDIZATION OF AIR‐FLOW IN INSECT SUCTION TRAPS
Authors: TAYLOR L. R. , COLEMAN W. S.
Published: February 2008

The air‐flow and its variations in sixteen insect suction traps of five different types have been measured, using regularity of air sample size as the criterion of efficiency. Traps with the air‐filtering cone enclosed in a cylinder and using axial flow fans with single‐phase capacitor‐start‐and‐run or three‐phase motors are most efficient and can have normal working limits of + 4 % of the mean air delivery.

However, for smaller traps which are to be used only close to the ground or in cover, the original type with exposed cone and shaded‐pole motor is quite satisfactory provided certain precautions are taken. Normal working limits of 5 8 % are then obtained.

These errors are derived in detail and the expected errors in more extreme conditions and with other traps are indicated.
THE APHICIDAL ACTION OF SOME SYSTEMIC INSECTICIDES APPLIED TO SEEDS
Authors: DAVID W. A. L. , GARDINER B. O. C.
Published: February 2008

When large seeds such as broad bean are soaked in certain systemic insecticides, notably demeton, the plants which they produce are toxic to aphids. With small seeds the effect is difficult to detect.

Experiments with demeton solutions and broad beans show that equal quantities of water and demeton are absorbed. Beans vary greatly in the rate at which they absorb solution, so, to reduce variations, about 24 hr. soaking is necessary. The insecticidal activity of the plant is directly related to the quantity of solution absorbed by the seed. Larger bean seeds absorb more solution than small beans and the plants are more toxic. After short periods of soaking (4 hr.) there is more insecticide in the seed coat than in the cotyledons, after 24 hr. there is more in the cotyledons. Some of the toxic material in the seed reaches the growing plant via the soil and roots. The material in the cotyledons can pass directly to the growing plant. As some of the material absorbed by the seed passes into the soil, any factors such as an increase in soil volume or heavy watering which tend to dilute the insecticides reduce the quantity of toxic material reaching the plant. The same quantity of demeton is more effective when absorbed by a seed than when watered on to the soil around it. Seeds soaked in insecticide, dried, and stored for one month produced plants toxic to aphids.
RELATIONSHIPS BETWEEN THE CHEMICAL CONSTITUTION AND FUMIGANT TOXICITY OF THE ALKYL IODIDES
Authors: HASSALL KENNETH A.
Published: February 2008

Nineteen alkyl iodides have been tested as fumigants against the grain weevil, Calandragranaria, using the technique previously described. Relative toxicities, and also the toxicities of mixtures of selected pairs of iodides, were determined.

Secondary and tertiary isomers were in general less toxic than the primary, irrespective of whether the toxicity was measured by molar LD 50' or the corresponding relative saturation (Pt/pB) values. Despite differences in LD 50', isomeric primary iodides often acted at about the samep,/p, value. It is suggested that these observations provide evidence that, although chemical reactivity appears to be the principal factor determining the values of LD so's in the iodide series, such physical factors as phase distribution also play their part, and their effect becomes noticeable for the primary isomers, for which the chemical reactivities may be nearly the same.

The deaths of individual grain weevils which had been exposed to iodides were more or less delayed. The change of the kill with time was, under standard conditions, the same when all except methyl and the tertiary iodides were used, which suggests that with these possible exceptions, all the iodides have the same type of chemical action on the organisms. The toxicities of mixtures of selected iodides tended to confirm this, for they varied from about 1.0 to 1.25 times the value predicted from the toxicities of the single iodides using the similar action equation. Despite the apparent similarity in mode of action the LD 50's and pt / p8 values varied widely, as did the ratios of the LD 50's of successive homologues in different isomeric series. This suggests that neither the magnitude of the pt / p8 value, nor the way in which it changes from member to member in a series, gives always a useful indication of the type of action shown by a compound or group of compounds.
THE EFFECT OF REPEATED SPRAYING OF INSECTS ON THEIR RESISTANCE TO INSECTICIDES
Authors: TATTERSFIELD F. , KERRIDGE J. R.
Published: February 2008

The administration of carbon dioxide in sublethal concentrations or for sublethal periods of time gave rise to an increased resistance to its effect in a strain of Drosophila melanogaster susceptible to the toxic effects of this gas. The effect did not appear to be permanent.

The successive administration by spraying of sublethal concentrations of DDT and BHC did not increase the resistance of a strain of D. melunoguster to their effects, either in the insects sprayed or their progeny. Only when the dosages were such as to give a high death‐rate did a significant increase of resistance of the progeny of the treated insects take place; the tendency was if anything to increase susceptibility, although the indications were not in favour of DDT acting as acumulative poison.

In a preliminan series of tests the topical application of D D T in sublethal doses to the adult insects resulted in a reduction in the amount or in the rate of egg laying.
A STUDY OF A FIELD POPULATION OF THE BLOWFLIES LU CILIA CAESAR (L.) AND L. SERICATA (MG.)
Authors: CRAGG J. B. , HOBART J.
Published: February 2008

Attempts to measure the dispersion, population density and longevity of blowflies are described. The experiments were made at Aber, Caernarvonshire, in 1943 on a narrow strip of coastal farm land (if x f ml.). Two liberations of laboratory‐bred Lucilia sericata (Mg.) were made. On the second occasion 286 flies of each sex were marked, and nine males and nineteen females were captured, the last capture occurring 15 days after liberation. The population density of this species was estimated to be approximately seven males and sixteen females per acre for the 840‐acre strip on the day of the second liberation.

On 24 days during the period 20 August–20 September 1943, field‐caught L. caesar (L.) females were marked, and trapping both by meat and chemical baits was continued for a further 3 weeks. 3600 females were marked, 847 being recaptured at least once, and sixteen on at least four occasions. In the later part of the blowfly season, a life of 5–6 weeks is apparently not unusual for L. caesar females. The population drawn upon by the traps at the liberation centre fluctuated between 700 and 30,000 during the 4‐week period. This may have represented a very localized concentration equivalent to 6–238 females per acre. Dispersion of marked L. caesar was low. On the assumption of a maximum spread of 5 miles, some 63 % of the marked flies remained within 4 mile of the liberation centre.
THE INFLUENCE OF HIGH CONCENTRATIONS OF AMMONIUM AND SODIUM MOLYBDATES ON FLAX, SOYBEAN AND PEAS GROWN IN NUTRIENT SOLUTIONS CONTAINING DEFICIENT OR EXCESS IRON
Authors: WARINGTON KATHERINE
Published: February 2008

Ammonium molybdate supplying 20 or 40 p.p.m. Mo prevented chlorosis caused by low iron supply in young flax plants, but sodium molybdate was effective only at the higher concentration. Temporary darkening of the green colour of the shoots was also produced by 40 p.p.m. Mo in iron‐deficient soybean and pea plants, but was soon followed by more severe chlorosis. Symptoms of molybdenum toxicity always developed when 40 p.p.m. Mo were given, whether or not the intensity of chlorosis was reduced. With an increase in iron supply, a reduction in molybdenum toxicity symptoms was confirmed in soybean and peas. In flax the higher level of iron eventually proved excessive unless it was combined with 40 p.p.m. Mo. High molybdenum thus seemed able to counteract both iron deficiency and toxicity in this plant.

High iron reduced the molybdenum content (p.p.m./d.m.) of both shoot and root in soybean, peas and also in flax provided the iron was not excessive. High molybdenum usually reduced the iron content of the shoot, but markedly increased it in the root. Molybdenum‐induced chlorosis could thus be partly attributed to inhibition in iron translocation, but the beneficial effect of high molybdenum or high iron on colour was not obviously correlated with the analytical data.
STUDIES ON THE EFFECT OF TEMPERATURE ON VIRUS MULTIPLICATION IN INOCULATED LEAVES
Authors: HARRISON B. D.
Published: February 2008

The rate at which the Rothamsted tobacco necrosis virus (RTNV) accumulates in inoculated French bean leaves increases with rising temperature to 22°C. and then decreases. Three days after inoculation, leaves at 22°C. contain 4000 times as much virus as at 10°C. and 1000 times as much as at 30°C. At all temperatures the rate of accumulation may depend on the balance between synthesis and inactivation of RTNV, but inactivation becomes increasingly important with rise of temperature above 22° C. and as the virus content of the leaves increases. Above 22°C. the rate of multiplication may increase but less rapidly than the rate of inactivation, and exposing inoculated leaves to ultra‐violet radiation at various intervals after inoculation suggests that at 30°C. RTNV multiplies in and moves from the initially infected epidermal cells in slightly less than the 6 hr. needed at 22°C. Thirty hr. are needed at 10°C. Newly formed virus is rapidly inactivated at 30°C. Raising the ambient temperature also decreases the numbers of local lesions produced by RTNV, possibly by increasing the chances that the introduced virus particles will become inactivated. Increasing the virus content of the inoculum above the level giving one lesion per sq.cm. does not increase the subsequent virus content of inoculated leaves.

At temperatures of 30°C. and below, tomato aucuba mosaic virus produces necrotic lesions in leaves of tobacco and Nicotiana glutinosa whereas above 30°C. the lesions are chlorotic. In both hosts this virus multiplies more rapidly when the infected cells are killed.
SOME OBSERVATIONS ON THE HATCHING RESPONSES OF THE CABBAGE‐ROOT EELWORM, HETERODERA CRUCIFERAE FRANKLIN
Authors: DONCASTER C. C.
Published: February 2008

Samples of root diffusate from sprouts (Brassica oleracea var. gemmifera), swedes (B. napus var. napobrassica), rape kale (B. napus var. arvmsis), and white mustard (Sinupis alba), all stimulated larval emergence from cysts of Heterodera cruciferae. When mustard‐root diffusate was added to leachings from the other species tested there was no apparent effect on larval emergence. In half dilution with tap water, mustard leachings were comparable in activity with similar dilutions of leachings from the other species under observation. Leachings from soil were less active than those from the four species of plants tested, but showed significant activity in comparison with tap water.

The form of the hatching curve was studied using diffusates from both sprouts and mustard roots, and in each case when cumulative hatch was plotted against time on a logarithmic scale, the sigmoid curve obtained closely fitted the theoretical sigmoid calculated from a probit analysis of the data.

Estimates were obtained of the log activity values of leachings from the four species of plants tested and from soil, following an examination of the dilution curves for mustard and sprouts root diffusates. These curves were closely parallel with one another, and it was therefore considered justifiable to derive log activity values for these root diffusates, although the cysts used in the hatching tests and the root‐diffusate samples were each obtained from a single source. For this reason some caution is perhaps called for in the interpretation of the results presented in this paper.
PECTIC ENZYMES SECRETED BY VERTICILLIUM DAHLIAE AND THEIR ROLE IN THE DEVELOPMENT OF THE WILT DISEASE OF COTTON
Authors: KAMAL M. , WOOD R. K. S.
Published: February 2008

An isolate of Verticillium dahliae obtained from Uganda was highly virulent to young cotton plants under greenhouse conditions. A hyaline variant which often appeared in culture was as virulent as the parent isolate, but preliminary experiments indicated that it did not survive as long in unsterile soil. The parent isolate grew rapidly in cotton plants after root inoculation and was isolated from stems and leaves well before the appearance of disease symptoms visible to the naked eye.

Protopectinase was produced in the absence of pectic materials, but more active preparations were obtained when media contained pectic substances. In general, there was a close correspondence between the protopectinase activity of culture filtrates and the toxicity of these filtrates to parenchymatous cells. Some separation of the two activities was obtained by heating enzyme solutions or by plasmolysing the test tissue.

Protopectinase solutions had little pectinesterase activity but rapidly reduced the viscosity of solutions of pectic substances. In general, the properties of protopectinase and the viscosity‐reducing enzyme were similar.

Young cotton shoots wilted rapidly when placed in cell‐free filtrates from cultures of the pathogen. Wilting was delayed under conditions unfavourable for transpiration. Evidence was obtained which showed that wilting was caused by the uptake of thermostable compounds of high molecular weight which impeded the upward flow of the vascular sap. Pronounced vascular browning was obtained only when solutions containing protopectinase were used. Wilting and vascular browning were obtained with solutions having little pectinesterase activity; in contrast, a solution having high pectinesterase activity produced relatively little vascular browning.
AN ANALYSIS OF THE EFFECTS OF INFECTION WITH LEAF‐ROLL VIRUS ON THE GROWTH AND YIELD OF POTATO PLANTS, AND OF ITS INTERACTIONS WITH NUTRIENT SUPPLY AND SHADING
Authors: WATSON D. J. , WILSON J. H.
Published: February 2008

The decrease in total dry weight of potato plants (var. Craig's Defiance) caused by infection with leaf‐roll virus was almost entirely at the expense of the tubers; the dry weight of the leaves and stems was increased, and that of roots and stolons only slightly decreased. The percentage loss of dry weight of the tubers was decreased by nitrogenous fertilizer, but was unaffected by phosphorus or potassium.

Infection greatly decreased net assimilation rate (NAR) between May and early July, but subsequently infected plants had a higher NAR than healthy plants. Infection also decreased leaf area per plant until early July, but it delayed senescence of the leaves, so that in late July and August infected plants had more leaf area than healthy plants. The more rapid senescence of healthy plants probably accounts for their lower NAR at this time. The mean decrease in NAR by infection was about 20%, and this was the chief cause of the loss of yield, for the mean decrease in leaf area was only 4%.

Comparisons of intact plants with plants from which either the rolled or the unrolled leaves were removed indicated that the lower NAR of infected plants was mainly due to diminished photosynthetic efficiency of the older, rolled leaves. The effects of nitrogen, phosphorus and potassium on NAR, and their interactions with infection, were small and rarely significant.

Nitrogenous fertilizer increased leaf area throughout the growth period; phosphorous increased it in the early stages but hastened senescence of the leaves, so that in August it decreased leaf area; potassium increased leaf area particularly in the later stages of growth. At the times when nitrogen, phosphorus or potassium increased leaf area they usually also increased the effect of infection as this tended to reflect plant size. Except in the early stages of growth infected plants had more leaves than healthy plants, because leaf production continued longer and more lateral branches developed.

Shading decreased NAR but increased leaf area; consequently it had no effect on yield. There were no interactions between shading and infection.

The loss of yield caused by infection of Up‐to‐Date plants was smaller than with Craig's Defiance because the leaf area of Up‐to‐Date was not decreased by infection, and the depression of NAR started later than with Craig's Defiance.
A LOCAL‐LESION TECHNIQUE FOR MEASURING THE INFECTIVITY OF CONIDIA OF BOTRYTIS FABAE SARDIÑA
Authors: LAST F. T. , HAMLEY ROSEMARY E.
Published: February 2008

Discrete lesions developed when conidial suspensions of Botrytis fabae Sardiña were rubbed with the forefinger on leaves of broad bean plants (Vicia faba L.) subsequently kept in a water‐saturated atmosphere. The numbers of lesions which developed were directly proportional to the concentration of inoculum. At equal concentrations, conidia from young cultures produced more lesions than conidia from old cultures.

Variation in lesion numbers between plants within a pot always considerably exceeded the variation between opposite half‐leaflets of a leaf, as did variation between pots and between leaves of old, but not of young plants.

As the standard error of the number of lesions developing per half‐leaflet (x) increases as the mean increases, the values of x need to be transformed before being statistically analysed. A suitable transformation is

z = log10 1/2{x + c +√(x2+ 2cx)}, where c = 20.