bluuebunny/crossref_metadata_2025_split huggingface dataset:
A COMPARISON OF THE GROWTHS OF WILD AND OF CULTIVATED OATS IN MANGANESE‐DEFICIENT SOILS
Authors: THURSTON JOAN M. 
Published: February 2008

Two species of wild oats, Avena fatua and A. ludoviciana, and two varieties of cultivated oats for comparison, were grown to maturity in pots of manganese‐deficient soil with and without added manganese. A. ludoviciana showed different leaf symptoms of manganese deficiency from A. fatua and the cultivated varieties. In other respects wild and cultivated oats were similar in their responses to the level of manganese supply, though differences were observed in the severity of the effects. These are summarized in Table 6. The relative susceptibility to manganese deficiency of the wild and cultivated oats differed according to the effect considered. The total dry weight at harvest is an integration of all the preceding effects on growth and is therefore presumably the best single criterion for determining susceptibility to manganese deficiency. On the basis of per cent loss of total dry weight at harvest due to lack of manganese, A. fatua is judged less susceptible and A. ludoviciana more susceptible than the two cultivated varieties and no distinction can be made between the latter.The most interesting differences between wild and cultivated oats in response to the level of manganese supply occurred in seed production. Manganese‐deficient wild oats showed a smaller reduction in the number of seeds formed but a greater reduction in the size and manganese content of individual seeds than the cultivated varieties.Manganese deficiency lowered the percentage of viable seeds and the percentage of dormant seeds produced by both A. fatua and A. ludoviciana.
THE ACTION OF MERCURY AS A SOIL FUNGICIDE
Authors: BOOER J. R. 
Published: February 2008

Metallic mercury and mercury compounds in the soil retard the growth of plants. The development of mosses and lichens is inhibited, and experimental evidence shows that the growth of toadstools on turf and the activity of ascomycetes is retarded by mercury. In vitro, mercury has no fungicidal action but the rate of growth of hyphae is reduced by mercury vapour.The lack of fungicidal properties of mercury and its good performance in controlling certain soil‐borne diseases are reconciled by assuming that a differential retardation disturbs the relationships necessary for infection. This assumption is supported by diagrams which treat the rates of growth of the parasite and the host as population characteristics normally distributed.
SEROLOGICALLY RELATED STRAINS OF POTATO VIRUS Y THAT ARE NOT MUTUALLY ANTAGONISTIC IN PLANTS
Authors: BAWDEN F. C. , KASSANIS B. 
Published: February 2008

Tobacco veinal necrosis virus is serologically related to potato viruses Y and C. It does not protect tobacco, Nicotiana glutinosa, or potato plants from infection by them, and tobacco and N. glutinosa plants infected with either virus Y or C are still susceptible to it. There is some evidence that it does not multiply normally in potato plants infected with virus Y and that it is sometimes suppressed in such plants.The possession of antigenic groups in common with viruses Y and C is considered to justify identifying tobacco veinal necrosis virus as a strain of virus Y, and to be of greater taxonomic significance than failure to protect plants against other strains. A further difference from other strains is that it is more virulent towards tobacco than towards potato.
STUDIES ON THE MECHANISM OF INSECTICIDAL ACTION OF ORGANO‐PHOSPHORUS COMPOUNDS WITH PARTICULAR REFERENCE TO THEIR ANTIESTERASE ACTIVITY
Authors: LORD K. A. , POTTER C. 
Published: February 2008

The preparation of an extract of the mealworm larvae, Tenebrio molitor L. which hydrolyses ethyl butyrate and o‐nitrophenyl acetate, but not acetylcholine, is described. The inhibition of this esterase by TEPP‐containing materials and parathion was determined.An enzyme that hydrolysed o‐nitrophenyl acetate and was inhibited by a TEPP‐containing material was demonstrated in the five other insect species used.The relative toxicities as contact insecticides to adult Tribolium castaneum Hbst. of ten samples of TEPP‐containing materials were compared with their relative activities as esterase inhibitors. There was not an exact quantitative correlation between TEPP content estimated chemically, insecticidal activity and anti‐esterase activity; but the correlation was sufficient to suggest interdependence of these factors.Eggs of Diataraxia oleracea L. and Ephestia kühniella Zell, were shown to contain an enzyme that hydrolysed o‐nitrophenyl acetate and was inhibited by the TEPP‐containing materials. This enzyme was present in eggs less than 24 hr. old, i.e. before there was any visible signs of development. The TEPP was shown to be toxic to these eggs and in high concentrations kills at an early stage of development before differentiation of the nervous system. This, in conjunction with the other evidence, suggests that esterases other than the choline‐esterase of the nervous system are important when considering the toxic action of these compounds.Comparison of the anti‐esterase activity and toxicity of parathion and TEPP‐containing materials as insecticides showed that although the TEPP materials were the more potent enzyme inhibitors, parathion was the more potent contact insecticide to five species of insects. This appears to be due to the relative instability of TEPP. The study of the rates of action of the two poisons applied at different concentrations supports this view.
THE PENETRATION OF THE INSECT CUTICLE BY ISOMERS OF BENZENE HEXACHLORIDE
Authors: ARMSTRONG G. , BRADBURY F. R. , STANDEN H. 
Published: February 2008

The penetration of the α‐, β‐, γ‐ and δ‐isomers of benzene hexachloride through the insect cuticle has been studied by a micro‐colorimetric technique.Grain weevils were exposed for varying periods to deposits of pure isomers of benzene hexachloride on filter‐paper. The amounts of each isomer picked up by the insects were determined as two fractions, one ‘outside’ representing that which could be removed by cold methanol washing, and the other ‘inside’ recovered after decomposing the insects with nitric acid.The results show that the amounts of each isomer taken up by the insects are in the approximate ratio of their solubilities in hydrocarbon solvents, and that the y‐isomer penetrates through the outer layers of the insect integument much more rapidly than the other three isomers tested.On the basis of these results it is concluded: (i) that the first stage of pick‐up of insecticide by the insects is simple solution of the insecticide in the outer waxy covering of the epicuticle; and (ii) that structural effects play an important part in the penetration through the insect cuticle as well as in toxic effects at the site of action.
PARTICLE SIZE OF INSECTICIDAL SUSPENSIONS AND THEIR CONTACT TOXICITY III. TEMPERATURE COEFFICIENTS AND TESTS BY INJECTION
Authors: McIntosh A. H. 
Published: February 2008

Aqueous DDT suspensions containing particles of different sizes gave different temperature coefficients of mortality in dipping tests against adult Oryzaephilus surinamensis and Tribolium castaneum. In the range 12–30°C., colloidal DDT showed a large negative coefficient, but the coefficient for a suspension of DDT crystals of 400μ was smaller (T. castaneum) or negligible (O. surinamensis). Thus, although a suspension of crystalline DDT was more toxic than colloidal DDT to warm insects, it was less toxic than the colloid to cool insects.A test was made of rotenone suspensions against adult milkweed bugs (Oncopeltus fasciatus Dall.) by application of measured droplets under the wings. Colloidal rotenone was more toxic than a crystalline suspension. Milkweed bugs could not be killed in this way by DDT suspensions.Tests were also made by injecting suspensions of rotenone, DDT and its fluorine analogue (DFDT) into milkweed bugs. A suspension of rotenone crystals was equitoxic with colloidal rotenone against insects kept for 3 days at 27°C. after treatment. The same was true of crystalline and colloidal DDT suspensions. If the bugs were kept at 10°C., colloidal rotenone was much more toxic than crystalline rotenone 2 days after treatment. But if the insects were kept for about 3 weeks and inspected at intervals, the first apparent difference in toxicity grew smaller, and in the end it nearly disappeared. With DDT the time for this to occur was about 10 days; and suspensions of colloidal and crystalline DFDT were equitoxic after only 2 days, even at 10°C.In the application test, the difference between colloidal and crystalline rotenone was a real difference in toxicity. It did not disappear with the lapse of time; but in the injection tests the two forms of each poison differed only in speed of action, and not in ultimate toxicity.
SOME INTERRELATIONSHIPS BETWEEN MANGANESE, MOLYBDENUM AND VANADIUM IN THE NUTRITION OF SOYBEAN, FLAX AND OATS
Authors: WARINGTON KATHERINE 
Published: February 2008

Soybean and flax were grown in nutrient solutions containing high and low levels of molybdenum and vanadium, in combination with toxic (10–25 p.p.m.) and non‐toxic (1 p.p.m.) manganese. Molybdenum (20 and to a less extent 10 p.p.m.) intensified the chlorosis induced by manganese excess, though these concentrations were harmless in the presence of 1 p.p.m. Mn. Vanadium (= 1.0, 5 and 10 p.p.m. Mo) counteracted some of the symptoms of manganese toxicity, but the two higher rates were harmful to growth irrespective of the manganese supply. Toxic concentrations of vanadium at first deepened the green colour of the shoot, though apical iron‐deficiency chlorosis was generally induced later. Low molybdenum (0.1 p.p.m.) or equivalent vanadium had no influence on growth or iron nutrition at either level of manganese. Visual differences were corroborated by changes in the nitrogen, phosphorus and iron contents of the plants. There was no evidence of replaceability of molybdenum by vanadium.Oats were grown in nutrient solutions containing various combinations of manganese (nil–400 p.p.m.) and molybdenum (nil–20 p.p.m.). The appearance of manganese‐deficiency symptoms was not affected by the quantity of molybdenum provided, and the manganese and molybdenum contents of the leaves were mutually independent of the quantity of each element supplied.
OBSERVATIONS ON THE BIOLOGY OF CLOVER ROT
Authors: LOVELESS A. R. 
Published: February 2008

The field behaviour of clover rot in eastern England indicates that infection takes place by ascospores, and not by soil‐borne mycelium developing directly from the sclerotia. To support this view, experimental evidence is presented to show that cutting of red clover at the time when the ascospores are being shed, reduces the percentage infection in the following spring.Ascospore infection of clover causes a ‘non‐aggressive’ spotting which may develop into an ‘aggressive’ infection. Sclerotinia trifoliorum has been shown to remain viable in non‐aggressive spots for at least 16 weeks. Similar symptoms occur when beans are infected with S. trifoliorum var. fabae. Non‐aggressive and aggressive infections are two phases of a sequence in time, and not two alternative types of infection dependent on the initial spore load. The occurrence of non‐aggressive and aggressive phases in nature explains (1) the observed delay between ascospore discharge and the appearance of obvious disease symptoms, and (2) the seasonal nature of the disease.Aggressive infection develops only in a saturated atmosphere and within a temperature range of 5–20° C., and its establishment is favoured by a heavy dosage of inoculum. In most seasons humidity is the main ‘limiting’ factor; over the 18‐year period, 1930–47, there is a significant regression between the severity of clover rot and the previous December plus January rainfall.Crop rotation and autumn grazing check the disease, but the latter must be practised with discretion because, under certain conditions, its effects are more drastic than those of the disease. The only hopeful method of effective control is the breeding of resistant strains of legumes.
THE SPREAD OF LETTUCE MOSAIC IN THE FIELD
Authors: BROADBENT L. , TINSLEY T. W. , BUDDIN W. , ROBERTS E. T. 
Published: February 2008

The epidemiology of lettuce mosaic was studied on two farms in Buckinghamshire during 1947–50. Two patterns of spread were obvious on Farm A during 1947–8: (1) spread within a crop from sources initiated by seed‐borne virus; and (2) spread into a crop from nearby infected old plants. The first type caused serious losses only when aphids were unusually numerous and the incidence of seed‐borne infection was high; serious losses more often resulted from the second type. Winter crops usually suffered severely, and they initiated a cycle of infection in the spring which continued from crop to crop throughout the year when aphids were sufficiently numerous. Spread from crop to crop was much reduced during 1949–50 by planting or drilling lettuce in large blocks, well separated from each other, and by omitting a winter crop. Killing the infesting aphids with an insecticide did not prevent the introduction of virus from nearby diseased crops. The insecticidal treatment of old diseased and aphid‐infested crops (but before alatae are produced) is recommended.More diseased plants often occurred near hedges, woods, trees or buildings than in the open field, presumably because such barriers halted flying aphids.Three species of aphids were common on lettuce: Nasonovia ribis‐nigri (Mosley), which infests the heart leaves; and Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer), which infest the outer leaves. M. euphorbiae and M. persicae are vectors of lettuce mosaic, but the former is less effective than M. persicae which, although rarely as numerous as the other two species, is the most important vector. All three species overwintered on lettuce, and migrated from the winter crops during April–May.One obvious need to control lettuce mosaic is the production of virus‐free seed. Without this, however, the disease can be ameliorated by adopting these measures whenever practicable: lettuce crops should be planted or drilled in large blocks, well separated from each other; diseased crops and crop‐remains should be destroyed as soon as possible; winter crops should be treated with an insecticide in late November, and insecticides should be used to prevent the production of large aphid populations, especially on old crops.
THE SPREAD OF BEET YELLOWS AND BEET MOSAIC VIRUSES IN THE SUGAR‐BEET ROOT CROP I. FIELD OBSERVATIONS ON THE VIRUS DISEASES OF SUGAR BEET AND THEIR VECTORS MYZUS PERSICAE SULZ. AND APHIS FABAE KOCH
Authors: WATSON MARION A. , HULL R. , BLENCOWE J. W. , HAMLYN BRENDA M. G. 
Published: February 2008

A survey of aphids and virus diseases of sugar‐beet root crops in eastern England was made between 1940 and 1948. Prior to 1943 the observations were made on fertilizer experiments; from 1943 onwards they were made on commercial fields selected for position in relation to beet and mangold seed crops. The incidence of beet yellows increased with increasing numbers of Myzus persicae, but not of Aphis fabae. The relation with M. persicae was sufficiently close to suggest that it is the most important, possibly the only important, vector of beet yellows virus. Beet mosaic virus also increased with increasing numbers of M. persicae, but the relation was not close enough to exclude the possibility of other vectors.Numbers of A. fabae on sugar beet were slightly, but consistently, depressed by the use of salt as a fertilizer. Other fertilizers had variable effects. Neither aphids nor virus are likely to be greatly affected by fertilizers.Beet yellows is most prevalent in areas where seed crops are grown, but within these areas nearness to individual seed crops did not appear to increase its incidence. M. persicae were more numerous on sugar beet in seed‐crop areas than elsewhere, and this alone might account for the prevalence of yellows. Beet mosaic virus is more closely associated with seed crops than is beet yellows. It is most prevalent near to seed crops within the seed‐crop areas.
SOME EXPERIMENTS AND FIELD OBSERVATIONS ON THE GERMINATION OF WILD OAT (AVENA FATUA AND A. LUDOVICIANA) SEEDS IN SOIL AND THE EMERGENCE OF SEEDLINGS
Authors: THURSTON JOAN M. 
Published: February 2008

The distinguishing characters of Avena fatua and A. ludoviciana are described.Pot experiments and field observations showed that most seeds of A. fatua germinated in spring and a few in autumn; hardly any germinated in summer or winter. Seeds of A. ludoviciana germinated in winter only. The greatest depth of sowing from which seedlings of either species reached the surface was 9 in., but seedlings from this depth were weak and yellow when they first appeared. A. ludoviciana gave more and sturdier seedlings than A. fatua from 6 and 9 in. There was no evidence of induced dormancy in seeds of A. fatua buried at depths down to 20 in. Germination of this species was hastened by monthly cultivation of the soil. The maximum survival of A. fatua was 3 years in pots and slightly longer in the field; seeds of A. ludoviciana in pots survived only 2 years. The two or three seeds of each spikelet of A. ludoviciana germinated in turn, starting with the largest, but the interval between germination of successive seeds varied.Seedlings from freshly sown seeds of both species were more vigorous than seedlings from seeds which had been buried for a year or more. Germination and subsequent growth of both species took place in soil of pH 4.5 to 7.0 approx.
OBSERVATIONS ON BROWN ROT (SCLEROTINIA FRUCTIGENA) OF APPLES IN RELATION TO INJURY CAUSED BY EARWIGS (FORFICULA AURICULARIA)
Authors: CROXALL H. E. , COLLINGWOOD C. A. , JENKINS J. E. E. 
Published: February 2008

Observations in West Midlands orchards in 1947–50 on the apple varieties Cox's Orange Pippin and Laxton's Superb showed that brown rot was often associated with shallow holes in the fruit. Laboratory experiments with undamaged apples proved that earwigs (Forficula auricularia) could cause this type of injury.Bands of sacking soaked in BHC placed around trunks of Laxton's Superb trees in 1949 and 1950 trapped many earwigs; less brown rot occurred in the banded than on control trees. A survey of picked fruit in 1950 showed close correlation between degree of earwig damage and amount of brown rot.Earwig damage was appreciable in fruit from ten out of thirteen grass orchards, but was negligible in fruit from nine arable plantations.
OBSERVATIONS ON THE LIFE HISTORY AND BIOLOGY OF TIPULA LATERALIS MEIG.
Authors: WHITE J. H. 
Published: February 2008

The occurrence of large numbers of larvae of Tipula lateralis Meig. in watercress beds has not hitherto been recorded. Observations on commercial beds and laboratory experimental work show this species to be primarily a saprophyte feeding on rotting submerged cress leaves, though it can develop during the final instar on green cress. Populations as high as 250,000/acre do not affect cress beds adversely.There are two generations a year and probably a partial third. The life cycle can be completed in 63 days. Mating and oviposition are described, the preferred site for egg laying being on wet soil. The average number of eggs is over 500. The egg and first‐instar larva are described for the first time. There are four instars, the anal segment of the first being radically different from that of the remainder. It has been shown that pupation cannot take place under water as previously stated.
SOME FACTORS AFFECTING THE TRANSMISSION OF LEAF‐ROLL VIRUS BY APHIDS
Authors: KASSANIS B. 
Published: February 2008

Datura tatula is a more suitable host than potato for studying the factors influencing the transmission of potato leaf‐roll virus by Myzus persicae; it is more easily infected, provides a better source of virus for feeding aphids, produces symptoms more quickly and over a longer period of the year.Loughnane's (1943) claim that leaf‐roll virus is transmitted by starved aphids that feed for only 5 min. on infected potato plants was not confirmed. The shortest infection‐feeding time in which M. persicae aphids became infective was 2 hr.; such aphids did not infect healthy plants in the first 2 days and, when transferred to a series of healthy plants at intervals, infected only few. The ability to cause infections was increased by increasing the length of infection feeding. Aphids fed for many days on infected plants could infect healthy plants in the first 15 min. of test feeding, and they continued to cause infections for long periods.Aphids became infective more readily when feeding on recently infected Datura tatula, showing only slight symptoms, than on older plants with pronounced chlorosis; similarly, young potato sprouts showing no symptoms were better sources of virus for aphids than older plants showing severe leaf roll.The differences in severity of symptoms shown by potato plants with leaf roll in the field mainly occur because of differences in virulence of accompanying strains of potato virus X, but isolates of leaf‐roll virus were found that also varied in virulence.
STUDIES IN THE MODE OF ACTION OF INSECTICIDES
Authors: HOPF H. S. 
Published: February 2008

Acetylcholine, choline chloride, acetyl‐β‐methylcholine, benzoylcholine, carbamyl choline, adrenaline and d‐tubocurarine are non‐toxic when injected into the locust. Prostigmine is also non‐toxic, and eserine considerably less toxic to the locust than to man.The toxic effect of tetraethyl pyrophosphate (TEPP) cannot be antagonized by injection of atropine or enhanced by d‐tubocurarine.The injection of acetylcholine chloride following injection of TEPP does not affect subsequent mortality.These findings are discussed, and it is suggested that the physiology of the nervous system of the insect is unlike that of the mammal, neither cholinesters nor adrenaline being concerned in it. Phosphorus insecticides are thought to inhibit a general esterase not specifically connected with cholinesters.