bluuebunny/crossref_metadata_2025 huggingface dataset:
METHODS FOR THE STUDY OF BLOWFLY POPULATIONS
Authors: MACLEOD JOHN , DONNELLY JOSEPH
Published: February 2008

The variance of groups of traps sampling the blowfly populations of areas of different degrees of complexity is examined from data for three representative types of pasture—semi‐arable, reclaimed peat bog, and upland sheepwalk.

For mean catches of under twenty flies the coefficient of variation was less for limited areas of homogeneous vegetational cover than for larger areas and greater diversity of vegetation; at intermediate mean levels the difference was negligible, hut it reappeared at mean levels of 40 and upwards.

Throughout the range of catches examined the variance was much greater than the mean. For very low catches even the standard deviation exceeded the mean, and at no level of mean was it less than 40%.

Even for uniform areas such as association fragments the high variance made results with less than six traps difficult to interpret, and ten or more traps are advised.

Two methods of comparative sampling of populations are discussed—stratification of the area to be sampled into subunits of relatively uniform vegetational or edaphic facies, and random distribution of the traps over the whole area. For the mean catches by these methods standard regression lines are suggested, from which variance estimates may be made when comparing observed means. Both regressions consist of two straight lines, the lower in each case having a steeper slope. The lines are:

Sections S.D. =x̄+ 1 and 0·5x̄+7.

Subsection blocks S.D. = 0·8x̄+ 1 and 0·4x̄+9
FUNGICIDAL ACTIVITY AND CHEMICAL CONSTITUTION:
Authors: BYRDE R. J. W. , WOODCOCK D.
Published: February 2008

Nine derivatives of pentachlorophenol have been prepared and tested for fungistatic activity against the mycelia of Botrytis fabae, Sclerotinia laxa and Stereum purpureum and for phytotoxicity towards tomato, apple and plum. The most fungitoxic of these compounds was the acetyl ester. Its phytotoxicity, although much less than that of pentachlorophenol itself, nevertheless precludes its effective use as an eradicant fungicide on foliage.
THE EFFECTS OF STREPTOMYCIN AND TERRAMYCIN, SINGLY AND IN COMBINATION, ON THE LEAF BLIGHT DISEASE OF MAIZE CAUSED BY BACTERIUM CAROTOVORUUM F. ZEAE SABET
Authors: SABET K. A.
Published: February 2008

The growth in vitro of Bacterium carotovorum f. zeae Sabet, the cause of the root and stalk rot and leaf blight disease of maize, was inhibited by dihydrostreptiomycin sulphate and by Terramycin (oxytetracycline). Joint applications showed a synergistic action, and the bacterium was most susceptible to a 1:1 mixture of the two antibiotics. This mixture is effective in checking the development of resistant strains which develop rapidly after treatment with streptomycin alone.

Roots of maize seedlings in water cultures, and leaves of older plants readily absorb both antibiotics. High water content of soil favoured absorption; sunlight had no effect. Absorption from leaf applications first increased with higher concentration and frequency of spraying, but after eight daily applications of streptomycin toxic symptoms appeared and there was evidence that the antibiotic was inactivated.

Antibiotic treatment of maize leaves shortly before inoculation with B. carotovorum f. zeae reduced the incidence and severity of leaf blight. The therapeutic effect extends at first both downward and upward but later only upward. Treatment of the leaves did not induce resistance to infection in the stems and roots.
GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE)
Authors: LANGER R. H. M.
Published: February 2008

Individual tillers of timothy (Phleum pratense) growing from seed in pots were labelled and their life history studied over a period of two years.

The leaf axil position of the first‐produced tiller depended on its time of origin. A minimum of five leaves on the parent axis was necessary before its appearance, and no tiller emerged from the axil of any of the three terminal leaves of a shoot.

Ear‐bearing capacity was high in early‐formed tillers, but decreased progressively with later dates of origin despite favourable day length; all tillers arising after the end of July failed to produce inflorescences. A greater proportion of tillers on the main stem formed ears than secondary tillers of the same age. Time of ear emergence varied only within a few days for all tillers arising before the end of April. The number of leaves formed up to ear emergence varied linearly with date of origin and tiller position, the lowest recorded number being six.

Dry weight and length of inflorescence as well as seed yield per tiller varied linearly with the date of origin of tillers. Primary tillers generally had longer and heavier inflorescences and produced more seed per stem than secondary tillers of the same age.

Tillers arising at all times were found to have a limited span of life, not normally exceeding just over a year. The mean age of ear‐bearing tillers varied linearly with their date of origin. Death‐rates of all tillers generally increased with their age. Relative death‐rates of fertile and vegetative tillers rose rapidly in the autumn but decreased during winter and early spring. Vegetative tillers which elongated in the year of formation survived for a shorter time than equivalent tillers in which stem elongation was delayed until the following year.

The perennial habit of grasses is discussed in relation to tiller survival. Successive new formation and death of tillers keep the plant in a condition of continuous dynamic change.
THE EFFECT OF DATE OF PLANTING AND OF HARVESTING POTATOES ON VIRUS INFECTION AND ON YIELD
Authors: BROADBENT L. , HEATHCOTE G. D. , McDERMOTT N. , TAYLOR C. E.
Published: February 2008

Experiments during 1953–6 tested the effects of early and late planting of King Edward potatoes on the incidence of virus diseases in the tubers and the suitability of the tubers for use as seed. Plantings were made each month from April to August and tubers were lifted after 12 weeks' growth or after the haulms had died.

Aphids began to colonize the early‐planted plots about mid‐June each year, but their multiplication and flying were influenced by weather and varied greatly from year to year. The May‐planted plots usually carried the most aphids. Winged aphids visited the July and August plantings, but few bred extensively though the plants were young and green. The incidence of virus diseases in the tubers was not related to the maximum aphid populations on the plants. Most of the plants that became infected became so by aphids flying from diseased potato plants in the same field, and the late‐planted plots did not escape. Crops planted in mid‐April and harvested in early July produced the fewest virus‐infected tubers.

Planting in April and lifting at the end of the season produced most ware‐sized tubers. In plots lifted after 12 weeks, May or June planting produced more ware than April planting. Few or no ware‐sized tubers were produced from July or August planting, and yields of seed‐sized tubers also were poor. Most seed‐sized tubers were produced by the late‐lifted May or June plantings. The date of lifting had little effect on the total number of tubers, but the date of planting affected it greatly. Most tubers were usually set by the May plantings and the number decreased with successive plantings.

Early‐lifted immature tubers were easily damaged and were difficult to store. Blighted tubers occurred only in the July or August plantings, which also suffered most from slug and cutworm damage.

Infection with leaf‐roll virus reduced yield by about three‐quarters, whether the seed had been lifted early or late the previous year. Healthy or virus‐infected mature seed produced a bigger crop the next year than immature seed obtained by early lifting or late planting.

Late‐planted tubers produced more main stems than those planted at the normal time, but growth of axillary shoots was reduced and total leaf area remained small, even when the plants were not attacked by blight.
FACTORS AFFECTING THE PATHOGENICITY OF BACTERIA TO POTATO TUBERS. II
Authors: MURANT A. F. , WOOD R. K. S.
Published: February 2008

Potato tubers in the laboratory were rotted by an isolate of Erwinia aroideae, but isolates of Pseudomonas sp. (probably P. marginalis), Flavobacterium sp., and Pseudomonas syringae were only weakly pathogenic. Differences in the amount of rotting of tubers of different varieties were not related to differences in the rates of browning of outer cells, of suberin development or of phellogen formation.

Growth‐regulating substances which affected the rate at which healing occurred at the wound surface did not affect rotting when they were added to inocula of Erwinia aroideae or Pseudomonas sp.

Increasing the water content of tuber tissue by soaking had little effect on the rotting caused by Erwinia aroideae, but greatly increased rotting by the other organisms. The rotting by each of the four organisms was increased further when the tissue was injected with water. Cell‐free filtrates from cultures of each of the four bacteria rotted soaked and injected tissue in much the same way as did the bacteria, but in normal tissue filtrates from cultures of the non‐pathogenic bacteria caused more rotting than did E. aroideae preparations, although in maceration tests with disks cut from potato tubers they had about the same activity.

The non‐pathogenic bacteria caused active rots when the outer surfaces of tubers were sealed with Vaseline; this treatment also increased rotting by E. aroideae. Only E. aroideae grew to any extent anaerobically in liquid culture. E. aroideae and Pseudomonas sp. rotted Vaseline‐sealed tubers more than unsealed tubers kept in a desiccator over alkaline pyrogallol.

Rotting of tubers by Erwinia aroideae, but not by Pseudomonas sp., was increased when the tubers were kept in a moisture‐saturated atmosphere.

The two species of Pseudomonas, but not the other two bacteria, caused appreciable rotting at 5°C.

Allowing surfaces of inoculation cavities to heal for 1–4 days before inoculation reduced the number and size of active rots caused by Erwinia aroideae, but did not prevent attack. Delaying inoculation for 1 day did not affect rotting by cell‐free filtrates from cultures of this organism and of Pseudomonas sp.

The surface layers of tubers, peeled and exposed to the air for 2 days, did not contain readily extractable materials toxic to Erwinia aroideae or Pseudomonas sp.

Pseudomonas sp. could be made to attack the healed surface of sealed tubers, by keeping the surface moist for twelve hours after inoculation.

The significance of these results is discussed.
AN ANALYSIS OF THE GROWTH RESPONSE OF YOUNG TOMATO PLANTS TO INFECTION BY VERTICILLIUM ALBO‐ATRUM
Authors: SELMAN I. W. , PEGG G. F.
Published: February 2008

Infection of seedling tomatoes with Verticillium albo‐atrum checked growth but did not result immediately in leaf yellowing. Localized wilting occurred in some plants 2 weeks after the check to growth was evident. 8 weeks after inoculation, dry weights of leaf, stem and root were decreased by 72, 70, and 65% respectively.

Of the growth attributes studied, leaf area was most reduced by infection and this was due to a failure of the leaves to expand rather than to a fall in the rate of leaf production. Neither water nor nitrogen appeared to be limiting factors in this respect. The water content of infected leaves was not reduced until 6 weeks after inoculation, when leaf yellowing and necrosis had also appeared. The percentage N contents of stem, root and leaf of infected plants exceeded those of the healthy controls 24 days after inoculation. N uptake was not seriously impaired until 21 days later.

The photosynthetic efficiency of the green leaves of infected plants was reduced. The mean values for net assimilation rates were: Healthy 0.47 and infected 0.39 g./dm.2/week.

Plants, in which two‐thirds of the root system had been killed by crushing, were placed in contact with mycelium in soil. This initial root injury did not significantly affect the growth of infected plants.

The data accord with a toxin theory of damage to infected plants, but the slow development of chlorosis and wilting symptoms in the young plants suggested a greater tolerance to the toxin than is found in older plants.
THE ANALYSIS AND RECONSTRUCTION OF DIURNAL FLIGHT CURVES IN ALIENICOLAE OF APHIS FABAE SCOP.
Authors: JOHNSON C. G. , TAYLOR L. R. , HAINE E.
Published: February 2008

Experiments, in which alate aphids were marked immediately after eclosion from the last nymphal instar and observed until they took flight, gave information which, together with the measured rate of moulting and a continuous record of temperature, has been used to construct theoretical daily curves for numbers flying from a bean crop. These curves have been matched against the observed curves for the same days.

The differences between curves so constructed for a period of 17 days and the observed curves for the same period are of the same order and kind as the differences between two measured curves in different sites at the same time.

The different types of daily flight curve can thus be accounted for in terms of the rate of production of alatae by moulting, the effect of temperature on the teneral (‘drying out’) period and the effect of low light intensity and temperature on take‐off behaviour.
INVESTIGATIONS ON RESISTANCE OF OATS TO STEM EELWORM, DITYLENCHUS DIPSACI KÜHN
Authors: GRIFFITHS D. J. , HOLDEN J. H. W. , JONES J. M.
Published: February 2008

A procedure adopted for testing many varieties of oats and segregating progenies for reaction to attack by stem eelworm (Ditylenchus dipsaci Kühn) is described, and its merits and limitations discussed in relation to the breeding of resistant varieties.

A study of some 250 forms of oats revealed new sources of resistance in cultivated and wild species. New sources of resistance in the cultivated species Avena sativa were found only in winter types, and in the other hexaploid species in forms belonging to A. byzantina (C) Koch, and the winter wild oat A. ludoviciana Dur.

Segregate progenies in advanced generations could be selected in the field by their reaction in a single drill in the first year followed by a head‐row progeny test in the next season. Reaction was sufficiently well defined to identify the truebreeding resistant and susceptible lines.

The inheritance of reaction to stem eelworm in crosses involving Grey Winter and susceptible types depended on a single factor pair with resistance dominant.
BACTERIAL CANKER OF STONE‐FRUITS III. INOCULUM CONCENTRATION AND TIME OF INOCULATION IN RELATION TO LEAF‐SCAR INFECTION OF CHERRY
Authors: CROSSE J. E.
Published: February 2008

Leaf scars on the fruiting spurs of the cherry varieties Roundel (high resistance) and Napoleon (low resistance) were inoculated with Pseudomonas mors‐prunorum on four separate occasions in the autumn, using, on each occasion, the same range of five different inoculum concentrations. The results, recorded the following year, showed that the percentage diseased spurs (disease incidence) and the severity of the disease symptoms (disease severity) both increased with inoculum concentration.

The median threshold concentration of inoculum (T. C. 50), defined as the concentration necessary to give 50% diseased spurs, varied with time of inoculation, but on all occasions was considerably higher for Roundel than for Napoleon.

In another experiment the leaf scars at the nodes of the current year's growth, inoculated at weekly intervals throughout the autumn, were found to be susceptible from the beginning of September to the latter part of October. During this period disease incidence varied considerably with time of inoculation. There was evidence that this variation was related to two factors which influenced the numbers of bacteria penetrating into leaf scars, namely, (1) the rate of evaporation of the infection drop, and (2) the rate of suction of inoculum into the vessels of the leaf traces.

The experiments provided evidence of a long infection period beginning early in the autumn. It is suggested, therefore, that the timing of bactericidal sprays in the autumn be advanced and that the present concept of ‘protective’ sprays in disease control be replaced by one based on the eradication of external sources of inoculum.
THE TOXICITY OF DDT IN ABRASIVE AND NON‐ABRASIVE DUSTS TO THE RICE WEEVIL, CALANDRA ORYZAE L. (COLEOPT., CURCULIONIDAE)*
Authors: HARLOW P. ANNE
Published: February 2008

The toxicity of DDT in different dust carriers to the rice weevil, Calandra oryzae, was determined under standardized conditions, using deposits large enough to ensure that the insects accumulated an excess of dust.

Some evidence was obtained that DDT is transported to the cuticle as a vapour.

At high humidity, the toxicity of DDT was not markedly affected by any carrier except charcoal which reduced the toxicity, probably by absorption of DDT vapour. Small differences in toxicity of DDT caused by other carriers could not be accounted for by differences in their average particle size, bulk density, amount adhering to insect, surface area, abrasiveness to insects or effect on behaviour of the insect.

At low humidity, abrasive dusts killed the insects by desiccation, thus adding to the toxic effect of DDT. Abrasion of the insect's cuticle did not affect the apparent rate of penetration of DDT at 50% R. H. or at 95% R. H.

Starved insects were more susceptible to DDT poisoning, and in some experiments abrasive carriers increased the toxicity of DDT by preventing the insects from feeding.
THE CUMULATIVE TOXICITY OF γ‐BHC AND DIAZINON APPLIED IN SMALL DOSES TO LOCUSTS
Authors: MACCUAIG R. D.
Published: February 2008

The toxicity of γ‐BHC and Diazinon when applied over a period of time to adults of the desert locust, Schistocerca gregaria (Forsk.), has been determined. The insecticides were applied in oil solutions, by means of the micro‐drop syringe, to the ventral surface of the abdomen.

When doses were applied in two equal portions with a 72 hr. interval, or in four equal portions at 24 hr. intervals, no significant decrease in toxicity, in comparison with a single dose, could be detected with either insecticide. It is concluded, therefore, that if similar effects occur when locusts are sprayed with these insecticides in the field, successive spraying will be fully cumulative over a period of 72 hr. Previous work using DNC has shown that doses applied over 4 days were only half as effective as equivalent single doses and that continued dosing after 4 days brought about very little increase in kill.

The sexes were similar in resistance to γ‐BHC when the doses were measured in μg./g., but females were considerably more resistant to Diazinon than males.
THE COMPARISON OF YELLOW CYLINDRICAL, FLAT AND WATER TRAPS, AND OF JOHNSON SUCTION TRAPS, FOR SAMPLING APHIDS
Authors: HEATHCOTE G. D.
Published: February 2008

Different traps were compared to find the type most suitable for studying aphid vectors of plant viruses quantitatively.

A Moericke water trap caught more aphids than a flat sticky trap of equal area. A flat sticky trap (930 sq. cm.) caught half as many aphids as a cylindrical trap (945 sq. cm.), which caught about one‐third as many as a water trap (1200 sq. cm.) or a Johnson suction trap (9 in. fan) when operated at between 2 and 3 ft. over bare soil.

Yellow traps caught proportionally more Tuberculoides annulatus, and in summer more Capitophorus species than a suction trap, but significantly fewer Anoecia corni, Sitobium spp. and Pemphigus bursarius. Traps with a level surface caught proportionally more Brevicoryne brassicae, Aphis fabae and Myzus persicae, but fewer Anoecia corni and Drepanosiphum plantanoides than vertical cylindical traps. Attraction by colour influences the catch on horizontal traps more than on cylindrical traps because there is less impaction by the wind.

Only suction traps indicate the number of aphids per unit volume of air and are non‐selective, but they are expensive and require an electric power supply. Water traps effectively catch those aphids that are attracted to yellow, but they require frequent attention. Sticky traps catch fewer aphids than either suction or water traps, but they can be left unattended for about 2 weeks. Flat sticky traps catch aphids likely to land on a crop, and cylindrical traps show when aphids are in the air, but not if those aphids are able or wanting to land. For routine work cylindrical sticky traps have other advantages; they are cheap and do not require skilled handling, and their catches of alate Myzus persicae have been correlated with the spread of some plant viruses.
INVESTIGATIONS ON FUNGICIDES II. ARYLOXY‐ AND ARYLTHIO‐ALKANECARBOXYLIC ACIDS AND THEIR ACTIVITY AS FUNGICIDES AND SYSTEMIC FUNGICIDES
Authors: FAWCETT C. H. , SPENCER D. M. , WAIN R. L.
Published: February 2008

A wide range of aryloxyacetic acids and corresponding acids with alkyl groups in the side chain, their arylthio‐ analogues and the antibiotic griseofulvin have been assessed in the plate test for fungistatic effect on six fungi, and as systemic fungicides against Botrytis fabae in broad beans and Alternaria solani in tomatoes. The results indicate that in general, arylthio‐ derivatives are more fungicidal than their aryloxy‐ analogues. The systemic fungicidal performance of x‐(2‐chlorophenylthio)propionic acid in the tomato test at 1–100 p. p. m. was found to be of the same order as that shown by griseofulvin at 50–500 p. p. m. Variable results were obtained with griseofulvin in the tornato test and its performance in the bean test was consistently poor. Further evidence is presented which indicates that the protection conferred by certain compounds may not be due to activity per se.
REVIEWS
Authors: CRAGG J. B.
Published: February 2008

Book reviewed in this article:

The Rabbit. By HARRY V. THOMPSON and ALASTAIR N. WORDEN.

The Distribution and Abundance of Animals. By H. F. ANDREWARTHA and L. C. BIRCH.

Biology of the Laboratory Mouse. Edited by GEORGE D. SNELL.

Features of Evolution in the Flowering Plants. By RONALD GOOD.

Tobacco Diseases with Special Reference to Africa. By J. C. F. HOPKINS.

Bibliographie der Pflanzenschutz‐Literatur 1950. Edited by J. BÄRNER.

Principles of Fungicidal Action. By JAMES G. HORSFALL.

Progress in Nuclear Energy. Series VI. Biological Sciences. Vol. 1. Edited by J. C. BUGHER, J. COURSAGET and J. F. LOUTIT.

Bacterial Diseases of Plants. By C. STAPP.

The Biology of the Heteroptera. By N. C. E. MILLER.

Man's Role in Changing the Face of the Earth. Edited by W. L. THOMAS.
THE NEMATICIDAL PROPERTIES OF AZIDES
Authors: BRADBURY F. R. , CAMPBELL A. , SUCKLING C. W. , JAMESON H. R. , PEACOCK F. C.
Published: February 2008

The use of sodium azide and organic acid azides for the control of potato root eelworm has been investigated: in suitable conditions they were effective both in greenhouse tests and in field trials. The biological activity of azides has been shown to arise from liberation of undissociated hydrazoic acid. The acid is only liberated in effective quantities in acid soils, but in such soils it is decomposed with formation of nitrogen. Organic acid azides are decomposed by a wide range of dust diluents and by soil, and there is some evidence that in diluents the main decomposition reaction is the formation of isocyanate by the Curtius rearrangement, whereas on wet soils extensive hydrolysis occurs giving hydrazoic acid, which is subsequently decomposed.
EFFECTS OF NUTRIENT TREATMENTS ON STEM‐BREAK OF FLAX (CAUSED BY POLYSPORA LINI LAFF.)
Authors: COLHOUN JOHN
Published: February 2008

Flax was grown in prepared composts containing different levels and ratios of nitrogen, phosphorus and potassium. When the cotyledons were inoculated with Polyspora lini Laff. the incidence of the seedling phase of the disease was not influenced by nutrient treatments, all plants being attacked. In such inoculated plants the lowest incidence of the stem‐break phase of the disease occurred in composts deficient in phosphorus. Increasing doses of the phosphatic fertilizer were associated with increases in susceptibility to stem‐break as well as in plant height and fibre yield. Small additions of the fertilizer produced little effect. In one experiment the incidence of stem‐break was directly and very significantly correlated with the percentage of phosphorus in the plants when nitrogen and potassium were held constant. Significant correlations were not found to exist between the incidence of stem‐break and the percentage of nitrogen or potassium in plants when the other two appropritate variables were held constant.
VERTICILLIUM WILT OF BRUSSELS SPROUT
Authors: ISAAC IVOR
Published: February 2008

A wilt disease of Brussels‐sprout plants caused by Verticillium dahliae Kleb, is described. Field observations indicate that the disease is more severe in a wet than in a dry season, the various stages of the pathological symptoms appearing earlier and developing more rapidly. This was corroborated by experiment; under dry conditions the onset of wilt symptoms was delayed and the severity of attack diminished. Since nine different strains and/or species of Verticillium wound‐inoculated into Brussels sprouts failed to induce wilt, and since the isolate from this host proved to be non‐pathogenic to a wide range of plants usually susceptible to attack by Verticillium spp., it is suggested that the V. dahliae from Brussels sprouts is a distinct physiological strain. Variations in the amounts of the different chemical constituents of the soil (calcium, nitrogen from two different sources, phosphate and potassium) have no apparent effect upon the incidence of disease. The pathogen is not seed‐borne but it may be spread by the dissemination of infected plant tissues. Some control measures are suggested and farmers are advised to grow in the infected soil runner beans, cauliflower and broccoli which are resistant to attack by this fungus.
FIELD EXPERIMENTS ON POTATO SKIN‐SPOT DISEASE CAUSED BY OOSPORA PUSTULANS OWEN & WAKEF
Authors: BOYD A. E. W.
Published: February 2008

In experiments on skin‐spot disease of potatoes, caused by Oospora pustulans Owen & Wakef., Kerr's Pink proved the most susceptible of twenty‐four commercial varieties; Arran Banner, Majestic and King Edward were highly susceptible; Home Guard and Golden Wonder were highly resistant.

Thymol and tetrachlornitrobenzene, applied as dusts to pits of potatoes at lifting, did not give satisfactory control of the disease. The efficacy of an organo‐mercury dip treatment at lifting time was confirmed.

The incidence of the disease was considerably decreased by storing tubers in boxes instead of in pits, by digging the crop about a month before normal harvest, or by cutting the haulms at this time and digging at the normal time.

Ware tubers showed a significantly higher infection than seed tubers of the same crop, indicating that susceptibility of tubers increases towards maturity.

The difference in eye infection between varieties may not be related to that of general superficial infection. It is suggested that, in future, the assessment of varietal susceptibility should be based upon the degree of eye infection, which is in practice the measure of the economic importance of the disease. Tubers having pustules at or near all the eyes gave markedly reduced sprout emergence and plant stand.
VIRUSES CAUSING ROSETTE AND OTHER DISEASES IN GROUNDNUTS
Authors: STOREY H. H. , RYLAND AUDRIE K.
Published: February 2008

From plants with a form of groundnut rosette disease, characterized by discrete areas of green and chlorotic tissue on the leaflets and here designated ‘mosaic rosette’, a virus was separated that produced only a mild mottle or sometimes a mottle with rare chlorotic flecks. It was separated by leaf grafts, by mechanical inoculation and by Aphis craccivora.

Plants inoculated simultaneously with the mottle virus and normal rosette virus usually developed the mosaic‐rosette symptoms. When the mottle virus was introduced 14–35 days before the rosette virus, the plants failed to develop the severe chlorosis of rosette; the mottle virus thus protected the plant from rosette, and this was true whether the rosette virus was inoculated by aphids or by grafting.

Plants showing two other forms of mild mottle were collected in the field; viruses from them were readily transmitted by grafting or by mechanical inoculation, but not by A. craccivara. In plant‐protection tests with one of these, it failed to protect plants from developing chlorotic symptoms when later inoculated with the rosette virus, although a form of interaction was evident and the doubly‐infected plant was less severely chlorotic and less stunted than one infected with the rosette virus alone.
A TECHNIQUE FOR THE BIOLOGICAL EVALUATION OF INSECTICIDAL AEROSOLS
Authors: GOODWIN‐BAILEY K. F. , HOLBORN J. M. , DAVIES M.
Published: February 2008

The development of a technique for testing insecticidal aerosols produced from pressure dispensers is described. The method of rearing the test insect, Musca domestica L., is given in detail.

Both free‐flying and caged flies were exposed in a room of 1194 cu. ft. Six insecticidal solutions were selected for test.

The biological efficiency of each aerosol was judged on the time required to paralyse 50% of the test insects (KD 500) and on the percentage kill obtained in 24 hr. Statistical analysis of some of the estimated figures for KD 500 showed a standard error of 4–5% of the mean.

The effects of temperature, of distribution and of dosage of the aerosol on the results were investigated.

Free‐flying flies were preferred, mainly because of better replication of results.

The technique adopted is described as a specification and suggestions are made for its practical application.
EMBRYONIC DEVELOPMENT AND ESTERASE ACTIVITY OF EGGS OF PIERIS BRASSICAE IN RELATION TO TEPP POISONING
Authors: POTTER C. , LORD K. A. , KENTEN J. , SALKELD E. H. , HOLBROOK D. V.
Published: February 2008

The embryological development of eggs of Pieris brassicae was studied in relation to the occurrence of enzymes hydrolysing phenyl acetate and acetylcholine. Phenyl acetate is hydrolysed at a high rate at all stages of development of the embryo. Hydrolysis of acetylcholine only becomes appreciable in the later stages of development. The first significant level of hydrolysis of acetylcholine can be correlated with the development of a nervous system in the embryo to a stage where it may be functional.

Aqueous solutions of TEPP were applied to eggs soon after they were laid. Low doses of TEPP allowed a high percentage of eggs to develop to the point of hatching before death occurred. Most fully developed embryos became active before they died. As the dose was increased less development took place and with very high doses little development occurred.

The significance of these results is discussed. The available evidence does not indicate that the poison penetrates slowly nor that it is ‘locked up’ and later released. The explanation that seems to fit the evidence best is that the poison penetrates rapidly and reacts irreversibly with, probably phosphorylates, one or more components of the egg, the extent of subsequent development depending upon the proportion of a biochemical system or the number of systems inactivated. Whilst inhibition of cholinesterase may play a part in the poisoning process, at least under some conditions, the evidence indicates that the death of the embryo may result from some other cause.
THE INFLUENCE OF THE pH OF THE NUTRIENT SOLUTION AND THE FORM OF IRON SUPPLY ON THE COUNTERACTION OF IRON DEFICIENCY IN PEAS, SOYBEAN AND FLAX BY HIGH CONCENTRATIONS OF MOLYBDENUM
Authors: WARINGTON KATHERINE
Published: February 2008

The prevention of chlorosis in flax by high concentrations of molybdenum in a nutrient solution was associated with a delay in the precipitation of iron from ferric citrate, a slower drift of pH towards alkalinity and an increase in the iron content of the root. These effects were greater with ammonium than with sodium molybdate and occurred with solutions started at pH 4.6 but not at pH 6.6.

When FeEDTA was the source of iron, a similar delay in pH drift in the solution and accumulation of iron in the root occurred, but there was no chlorosis or precipitation of iron in the control treatment, so the effect of high molybdenum could not be fully determined.

When ferric chloride was used, high molybdenum did not prevent chlorosis nor delay iron precipitation or cause accumulation of iron in the root, though the rate of pH drift resembled that of solutions containing the organic forms of iron.

Similar results were obtained with peas and soybeans receiving high molybdenum treatment, but suppression of chlorosis was only temporary.

It is suggested that the capacity of molybdenum to offset chlorosis is due to the formation, in acid solution, of a complex with phosphorus which renders iron more available by delaying the formation of ferric phosphate. This seems to occur only when iron is supplied in the organic form.
SOME EFFECTS OF NITROGEN SUPPLY ON THE INFECTION OF TOMATO PLANTS WITH TOMATO SPOTTED WILT VIRUS
Authors: SELMAN I. W. , GRANT SHEILA A.
Published: February 2008

The susceptibility of tomato plants to systemic infection by tomato spotted wilt virus was increased by increasing nitrogen supply to levels above that optimal for growth. The virus content, estimated by local‐lesions counts, was also raised by increasing nitrogen. The period between inoculation and the appearance of systemic symptoms was decreased by increasing nitrogen to a point slightly greater than the optimal level for growth, but increased by additional applications.

Infected plants receiving more nitrate or ammonium compounds than were needed for optimal growth showed abnormal leaf symptoms and no bronzing. N, P and Mg analyses showed that these symptoms were related primarily to nitrogen content. Such leaves contained more virus than bronzed leaves.
ARREST OF THE SWOLLEN‐SHOOT VIRUS DISEASE OF CACAO IN THE GOLD COAST BY CONTROLLING THE MEALYBUG VECTORS WITH THE SYSTEMIC INSECTICIDE, DIMEFOX
Authors: HANNA A. D. , HEATHERINGTON W.
Published: February 2008

A 13‐acre plot of cacao, in an area devastated by swollen shoot, was treated by dimefox applied to the soil nine times. The plot was examined every month and trees recorded as they showed symptoms. The number of such trees decreased very rapidly a year after the first treatment and remained low for the 3 years that the experiment was continued. This suggests that the time between infection and symptom development can extend to about I year. The cause of the continued appearance of a few diseased trees could not be determined.

As cacao farms differ from one another, it was difficult to find suitable control plots. Three farms in the neighbourhood of the chemically treated area were selected. The initial percentage of diseased trees in each was lower than on the chemically treated plot. The three farms were inspected every month and newly discovered trees with symptoms were felled. The number of such trees decreased 12 months after the initial cutting out and then increased abruptly until it again reached a high level.

Chemical treatment combined with cutting out was more efficient than cutting out alone in arresting the advance of the disease.
INVESTIGATIONS ON FUNGICIDES. III. THE FUNGITOXICITY OF 3‐ AND 5‐ALKYL‐SALICYLANILIDES AND PARA‐CHLOROANILIDES
Authors: TOPPS J. H. , WAIN R. L.
Published: February 2008

The anilides and para‐chloroanilides have been prepared from the first four homologues of the 3‐ and 5‐alkylsalicylic acid series and the fungistatic activity of these compounds has been assessed by two methods. In tests against mycelium, the chloroanilides usually induced less retardation of growth than the corresponding anilides. The effect of introducing an alkyl grouping was in general to reduce the fungistatic effect but with the n‐propyl derivatives this trend was less marked. Salicylanilide gave the greatest over‐all inhibition of the fungi investigated.
STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS
Authors: SABET K. A.
Published: February 2008

The bacterial leaf spot disease of jute (Corchorus olitorius) is characterized by the development of brown circular spots, about 2–5 mm. in diameter, on the leaves, surrounded, sometimes, by a yellow halo. The disease on the stems causes elongated lesions, and on the capsules produces small sunken spots. Defoliation and death of the stems may result in severe infections. The disease is ascribed to a new variety of Xanthomonas nakatae (Okabe) Dowson, the cause of a somewhat similar disease of Corchorus capsularis in Formosa (Elliott, 1951), on the ground that: (i) the minor differences between the two pathogens in biochemical characters are considered well within strain differences, and (ii) the Sudan pathogen does not infect C. capsularis, and Xanthomonas nakatae has not been reported to infect Corchorus olitorius. These differences do not justify the creation of a new species. The name Xanthomonas nakatae v. olitorii is suggested for the cause of the disease under consideration.
THE INOCULATION OF TOBACCO CALLUS TISSUE WITH TOBACCO MOSAIC VIRUS
Authors: KASSANIS B. , TINSLEY T. W. , QUAK FREDERIKA
Published: February 2008

Although cultures of normal and conditioned tobacco callus tissue occasionally became infected when dilute solutions of tobacco mosaic virus was poured over them, injuries were usually required, and the number of infections depended on the type and number of injuries. Tissues infected by superficial injuries usually became virus‐free after subculturing, whereas those infected by needle‐prick remained infected permanently. Although no plasmodesmata were found joining cells in the tissue cultures, tobacco mosaic virus moved between them at a rate of about 1 mm. per week, approximately the same rate as it moves through cells of the leaf parenchyma.
VIRUS DISEASES OF ADANSONIA DIGITATA L. (BOMBACACEAE) AND THEIR RELATION TO CACAO IN GHANA
Authors: ATTAFUAH A. , TINSLEY T. W.
Published: February 2008

Virus‐infected Adansonia digitata L. were found in the Guinea‐savannah woodland forming the Northern Territories and on the Accra plains of Ghana, but those tested in the rain forest were not infected. Three viruses isolated from infected trees resembled the Kpeve cacao virus, but no definite relationship could be established. It is unlikely that the original outbreaks of swollen shoot in cacao came from A. digitata.
SOME ASPECTS OF THE EFFECT OF THE SOLVENT ON THE TOXICITY OF SOLUTIONS OF INSECTICIDE
Authors: HADAWAY A. B. , BARLOW F.
Published: February 2008

The effect of varying the solvent upon the contact toxicities of solutions of insecticides to mosquitoes and flies has been investigated using DDT, prolan, dieldrin, endrin and malathion. The insects were allowed to walk for a limited time on filterpapers impregnated with the solutions. Chemical structure of the solvents had a general influence upon the biological activity of the solutions. Providing that the physical properties of the solvents were similar, insecticides were more effective in paraffinic hydrocarbons than in aliphatic long‐chain esters and related compounds, and were least effective in aromatic esters. Physical properties of the solvents were of importance in determining the effectiveness of insecticides dissolved in a group of solvents of similar chemical structure. Viscosity was an especially reliable guide as it presumably controlled the rate at which the solution could pass from the paper and be absorbed by the insects during the exposure period.

The order in which the solvents could be arranged with regard to their ability to influence biological action was the same for all the insecticides used, but the ratios of the median lethal concentrations in different solvents varied greatly from one insecticide to another. Consequently, the relative toxicities of the insecticides depended upon the solvent in which they were dissolved.

When some of the solutions used in filter‐paper tests were applied topically to the insects the differences in effectiveness were greatly reduced, showing that an important influence of the solvents had been upon pick‐up of insecticide from the papers. However, even with topical applications there were still some differences in median lethal concentrations and especially in rates of action between the solvents, thus providing further evidence that the solvent is also concerned with passage of insecticides through the insect cuticle.

The relative toxicities of the solutions bore no relationship to the solubilities of the insecticides in the solvents, and it was concluded that in these experiments chemical potential was not likely to be a controlling factor.
CONTROL OF SEED‐BED LOSSES OF GROUNDNUTS BY SEED TREATMENT
Authors: TARR S. A. J.
Published: February 2008

Fungicide treatment of groundnut (Arachis hypogaea L.) seed usually reduced seed‐bed losses and improved emergence, plant populations and yields of this crop when cultivated under rain in the sandy soils of Kordofan (west‐central Sudan) or under irrigation in the alkaline clay soils of the Gezira. These beneficial effects were greatest with slightly damaged seeds, such as would occur with machine sowing, but were present even when selected undamaged seed was sown by hand; they were attributed to protection against a number of soil micro‐organisms, including Aspergillus niger van Tieghem, A.flavus Link and Rhizopus spp. Agrosan GN (organo‐mercurial, 1% mercury equivalent) or 50% thiram powder, both applied at the rate of 1 g./lb. of seed, are suggested as suitable dressings for groundnut sowing seed in the two areas studied. Combined fungicide‐insecticide dressings containing up to 40% by weight of γ‐BHC did not control a late attack of wilt, due to root attack by cockchafer grubs (Schizonycha sp.), which developed some 8 weeks after sowing in the Gezira.
PHOTOSYNTHESIS AND RESPIRATION RATES OF LEAVES OF NICOTIANA GLUTINOSA INFECTED WITH TOBACCO MOSAIC VIRUS AND OF N. TABACUM INFECTED WITH POTATO VIRUS X
Authors: OWEN P. C.
Published: February 2008

The rates of respiration and of photosynthesis of tobacco leaves infected with potato virus X were not affected until the leaves showed symptoms; the respiration rate was then increased by more than 30% and the photosynthesis rate decreased by 20%. When local lesions appeared on the leaves of Nicotiana glutinosa infected with tobacco mosaic virus, but not before, the respiration rate was increased by an amount, up to 30%, that varied with the number of lesions. The photosynthesis rate was decreased by 20%, but there was no effect on photosynthesis or respiration until symptoms appeared. These results differ from those previously reported for tobacco leaves infected with tobacco mosaic virus, in which both respiration and photosynthesis were affected within 1 hr. of inoculation. The validity of extrapolating arguments based on the results obtained with other combinations to this commonly used combination and vice‐versa is questioned.
A GENETIC STUDY OF THE COLOUR FORMS FOUND IN POPULATIONS OF THE GREENHOUSE RED SPIDER MITE, TETRANYCHUS URTICAE KOCH
Authors: HUSSEY N. W. , PARR W. J.
Published: February 2008

There are two forms of greenhouse red spider mite in Great Britain, one with green summer females and the other with reddish brown females. The latter, usually associated with carnations, does not hibernate. Breeding experiments show that these forms are subgenerically distinct, but hybrids of low fertility can occur. The reddish colour of these female hybrids is incompletely dominant over the green and under some conditions they are indistinguishable from the reddish brown form. Biological information suggests that the British reddish brown form is distinct from Tetranychus cinnabarinus Bois.
BACTERIAL BOLL ROT OF COTTON (XANTHOMONAS MALVACEARUM (E. F. SMITH) DOWSON)
Authors: LOGAN C.
Published: February 2008

Two inoculation techniques were compared for their value in assessing resistance of cotton to bacterial boll rot. In the first method, bacterial suspensions were applied with a fine brush to the outsides of young bolls immediately after corolla drop. In the second, suspensions were inoculated into the wall tissue of bolls 3–4 weeks old with a fine needle. The second method is the simpler and produces infections in all weather conditions; other advantages are that bolls are inoculated after the period of natural shedding and the circular lesions are easily measured, but a disadvantage compared with the brush method is that the puncture method does not satisfactorily indicate damage to the lint.

Results from the two methods of inoculation suggest that resistance lies in some component of the boll‐wall tissue that affects bacterial growth and not in a physical factor that prevents the bacteria entering the boll. Variability in resistance occurs in local strains of cotton, and this could probably be exploited to give high resistance without the need of a large crossing programme to introduce new genes.
METHODS FOR THE STUDY OF BLOWFLY POPULATIONS
Authors: DONNELLY JOSEPH
Published: February 2008

1. A simple method of radioactive labelling of L. sericata larvae is described.

2. More uniform count levels are obtained in individuals which have fed entirely on radioactive foods than in those which first feed on non‐active food.

3. The radioactive count rates of the larvae are correlated with larval live weight and the counting rates of resulting imagines correlated both with corresponding larval counting rates and with imaginal live weight.

4. The loss of 32P in the larvae due to causes other than decay of the isotope is traced from the prepupal stage to 3 weeks after emergence. The first and major loss occurs at emergence, when about 10% of the original 31P is shed as empty puparium and meconium. Adults lose about 1.5% per day.

5. The distribution of 32P in the adult body of L. sericata labelled in the larval stage has been determined. The abdominal tissues have a lower activity than the rest of the body.
EXPERIMENTS ON THE MOVEMENT OF STREPTOMYCIN IN CHERRY TREES
Authors: CROSSE J. E. , GARRETT CONSTANCE M. E.
Published: February 2008

Systemic activity of streptomycin in cherry trees was investigated by studying the penetration of the antibiotic into leaves and its subsequent translocation.

Antibiotic penetration appreciably suppressed infection with Pseudomonas morsprunorum. In detached leaves the uptake of the antibiotic was progressive with time.

Widespread and rapid distribution of the antibiotic in the transpiration stream resulted from petiolar injection. Immersion of the laminae of intact leaves in the antibiotic resulted in a much slower translocation, possibly occurring in the transpiration stream.

Evidence suggests that the antibacterial activity detected in fruiting spurs after field spraying is not dependent on the presence of leaves, but results from direct penetration of the antibiotic through the dermal tissues of the spur.

It was concluded that foliar sprays at field concentrations were unlikely to result in significant systemic distribution of the antibiotic, but that localized activity might be an important factor in the control of bacterial canker.