bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further experiments on the control of white rot (Sclerotium cepivorum Berk;) in onions, shallots and leeks
Authors: Booer J. R. 
Published: February 2008

Trials in 1945 confirmed earlier work on the efficacy of mercurous chloride (calomel) for the control of Sclerotium cepivorum in spring‐sown onions. The application of 1 lb. 4% calomel dust to 50 yd. of seed drill at sowing time gave sufficiently good control of the disease in salad onions. Broadcast application of 1 oz. 4% calomel dust per sq.yd. before sowing was less effective but promising. Post‐emergence application of the dust was useless. In autumn sowings, seed‐drill treatment at 1 lb./so yd. controlled the disease in the following spring, but caused severe retardation and loss of crop.Onion seedlings raised in heat and dipped in an aqueous paste of calomel dust before transplanting showed a high degree of resistance to a severe attack. Similar treatment of shallot bulbs was also effective. In both cases, the treatment substantially increased the yield and somewhat reduced storage losses.Leek seedlings transplanted into dibber holes did not develop the disease.
Distribution of violet root rot (Helicobasidium purpureum Pat.) of sugar beet and preliminary experiments on factors affecting the disease
Authors: Hull R. , Wilson A. R. 
Published: February 2008

Examination of sugar beet grown in eastern England over the period 1936‐43 has shown that up to 5% of factory tarehouse samples contain roots infected with violet root rot. The results of the survey suggest that there are considerable areas where light attacks of the disease occur, as well as fields in which severe attacks develop when susceptible crops are grown. The disease occurred on roots grown in many types of soil but most frequently on those from light alkaline soils. It was found to reduce the sugar content and increase the dirt tare of sugar beet.The causal fungus, Helicobasidium purpureum, has a wide host range and observations suggest that it persists in the field on weeds, as severe attacks on cultivated crops often occur in weed‐infested fields. It also survives as sclerotia, which develop freely on the roots of susceptible crops. While the undisturbed soil conditions of leys and uncultivated land favour increase in infectivity, good cultural practices, trap cropping and application of nitrogenous fertilizers act as a check. These control measures will reduce infectivity even when applied to soil in which consecutive, susceptible crops are grown. Wet soil conditions did not favour the development of infection, and the frequent occurrence of the disease in wet places may be due to such soil conditions favouring survival of sclerotia.Experiments with compost made from factory waste showed that although the fungus can survive the process, its virulence was so reduced that there is no likelihood that use of such compost would lead to severe violet root rot infection.
WIREWORM POPULATIONS IN RELATION TO CROP PRODUCTION: III. POPULATION CHANGES AFTER SUMMER PLOUGHING
Authors: COCKBILL G. F. , ROSS D. M. , STAPLEY J. H. 
Published: February 2008

Six permanent pastures broken up in the summer of 1943 were sampled once a fortnight after ploughing in order to study changes in the wireworm populations.The graphs of the running means of four consecutive counts showed the chief trends in population. On four of the fields, a slight increase in population was apparent up to December. Only in February and March was a definite decline apparent. On the other two fields, the counts declined by about 30 % during the autumn and winter.A marked fall in population (from 30 to 70%) was evident on all the fields only after the first crop had been harvested. The new population at this time was characterized by an absence of larvae less than 4 mm. in length.The results considered alone indicate that after summer ploughing the wireworm population remains unaffected until the following spring and summer during the cropping period. When the results are considered in relation to the grass ‘controls’, it appears that a net decline in population occurs during the autumn and winter and that the decline in spring and summer is not more marked than that which normally occurs at this time in grass fields. Unlike the grass fields, however, the reduction is permanent.
WIREWORM POPULATIONS IN RELATION TO CROP PRODUCTION: IV. POPULATION CHANGES DURING A BARE FALLOW
Authors: STAPLEY J. H. , ROSS D. M. , COCKBILL G. F. 
Published: February 2008

Changes in wireworm populations during a bare fallow were studied on twenty‐three fields in 1943 and 1944. In every case populations were much reduced, sometimes to less than 10% of the original level. Wireworms of all sizes were affected, but the larvae less than 5 mm. in length were practically eliminated from the populations.Evidence is presented that the reduction achieved is greater in fields ploughed in February and March than in fields ploughed in May.As the populations in the grass ‘controls’ decline during the same period the entire reduction cannot be attributed to the fallow. The reduction in the bare fallow, however, differs from that in the controls in that it is permanent and continues through the autumn when the counts on the ‘controls’ are rising.The practical implications of the results are discussed.
PRIMULA OBCONICA, A CARRIER OF TOBACCO NECROSIS VIRUSES
Authors: BAWDEN F. C. , KASSANIS B. 
Published: February 2008

A tobacco necrosis virus has been isolated from the leaves and flowers of naturally infected Primula obconica plants. Although the virus produces no necrotic symptoms, it is not distributed uniformly through primulas, but occurs only in isolated regions, most of the tissues being apparently virus‐free.When inoculated to healthy primulas, three tobacco necrosis viruses were found to behave similarly. They all enter and multiply locally, but produce no symptoms; movement from the inoculated areas occurs only rarely and then does not cause a full systemic infection but only further localized infections. Multiplication of the viruses in primula is slower than in tobacco or French bean, which react necrotically.The uncertainties in interpreting results of tests for tobacco necrosis viruses are described and possible explanations of natural infections are discussed.
THE PROTECTIVE EFFECT OF ARSENIC AND DERRIS DIPS AGAINST THE SHEEP TICK, IXODES RICINUS L
Authors: MacLEOD J. 
Published: February 2008

Sodium arsenite used at a bath strength of 0.2% As2O3 is shown to protect sheep to a large extent from infestation for periods of from 1 to 2 weeks. Coal‐tar creosote dips, though usually effective in killing attached ticks, have no protective effect against reinfestation. Derris, either as ground root or as extract, kills all attached ticks at dilutions down to the order of I part extract in 15,000 of water. At a concentration of 1 part in 5000 it has an effective duration comparable to that of arsenic at 0.2% As2O3. Its maximum effective duration, when applied as an emulsion wash, appears to be 14–17 days.The addition of wool grease enhances the effective duration of arsenic, but not of derris. The effect of immersion time is important for both arsenical and derris dips, but is especially important for the latter. For full effect with derris washes sheep must be immersed for at least half a minute.A protective dip is described which markedly lowers the infestation of dipped sheep for about 3 weeks.
THE PARASITISM OF STRIGA HERMONTHICA BENTH. ON LEGUMINOUS PLANTS
Authors: ANDREWS F. W. 
Published: February 2008

Pot experiments at the Gezira Research Farm showed that Striga hermonthica Benth. is not confined to the Gramineae but can also parasitize groundnuts, cowpea, dolichos bean and soya bean, causing a loss in yield in all but the last‐named. The Striga plants developing on the roots of these hosts were small, apparently ill‐nourished and did not grow more than 1 cm. above the ground, in contrast to the vigorous, flowering Striga plants that develop on sorghum. The greatest reduction in yield in these experiments was in dolichos bean, where the aerial growth was reduced 60%; no significant reduction in root weight was found in groundnuts, cowpea or soya bean. The last‐named plant appeared to be feebly parasitized by S. hermonthica. A reduction in total nodule weight, but not in number of nodules, was obtained in groundnuts and cowpea. Parasitized dolichos bean showed a reduction in both the number of nodules and in nodule dry weight; in groundnuts, the later fruit production was seriously reduced.The use of these leguminous crops to clean Striga‐infested soil is discussed.
AN ECOLOGICAL STUDY OF THE ENCHYTRAEID WORM POPULATION OF SEWAGE BACTERIA BEDS LABORATORY EXPERIMENTS
Authors: REYNOLDSON T. B. 
Published: February 2008

This paper records the results of the experimental phase of an ecological study of the enchytraeid population of the sewage beds of the Huddersfield Corporation. The sewage in this drainage area is heavily charged with chemical wastes which have a marked effect on the fauna. Enchytraeus albidus Henle was the dominant worm while Lumbricillus lineatus Mull., the common bacteria bed‐worm, was relatively scarce. The ability of these two worms to complete their life cycles in the sewage before and after treatment in particular beds was examined.The crude Huddersfield sewage proved toxic to both E. albidus and L. lineatus but the former was much more resistant. After treatment in the beds the degree of toxicity was much reduced and the final sewage was harmless to all stages of E. albidus but the eggs of L. lineatus were still unable to develop in it.The eggs of both species were less resistant to the toxic substances than the young worms; the adults were most resistant. High temperatures lowered toxicity by reducing the duration of the more susceptible early stages.There was no evidence of physiological adaptation of L. lineatus to conditions in the Huddersfield beds. Wastes from both the main chemical works in the drainage area were examined and shown to be toxic; the domestic sewage was non‐toxic. Both the distillate and residue of one of the chemical wastes proved toxic, especially the latter.The toxicity could be entirely removed from the treated sewage by standing it over activated carbon for a few hours, or permitting slow oxidation for some weeks. The eggs of L. lineatus were used for these tests.The Huddersfield sewage was very acid from time to time and the acidity reached was sufficient to kill young worms and adults of both species. But this factor was not considered important in the beds owing to the persistent effects of the toxic sewage.
THE RELATION BETWEEN THE SIZE OF PLANT AND THE SPREAD OF SYSTEMIC DISEASES: I. A DISCUSSION OF IDEAL CASES AND A NEW APPROACH TO PROBLEMS OF CONTROL
Authors: Van der Plank J. E. 
Published: February 2008

it is implicit in the concept of systemic disease that there should be a connexion between the size of the plant and the spread of infection.a first, general theorem, thought to be universally valid, is: the spread of an infectious systemic disease increases with the size of the plants, size being appropriately determined and other factors being constant.a second theorem for infections which enter a crop from without (e.g. from the soil or from another field) is: when a systemic disease enters a crop from some uniform outside source, the logarithm of the proportion of healthy plants is directly proportional to the size of the plants, other factors being constant; as an approximation, the proportion of infected plants is directly proportional to their size, provided that the proportion is small. a corollary to this theorem is that if the proportion of infected plants is small and if the size is inversely proportional to the density of planting, the number of infected plants per unit area will be approximately constant, factors other than size and number being constant.a third theorem for the spread of infection within a crop is: when a systemic disease spreads within a crop, the rate of infection is proportional to the size of the healthy plants, other factors being constant. if factors other than size, time and the proportion of infected plants are constant, the expression for the rate takes one of the three forms: dx/dt=ks (i‐x), (i) dx/dt=ks (i‐x)x, (ii)or dx/dt=ks (i‐x) f (s, t, x), (iii)in which x and 1‐x are, respectively, the proportions of infected and healthy plants, s is the size, and k is a constant. the second part of this theorem is tentative.in these theorems we take by definition a disease to be systemic if a single effective transmission suffices to bring about maximum infection of the plant. size refers to that part of the plant which can receive infection. this definition, with the size of the receiving part having its colloquial meaning, serves for the first, general theorem. for quantitative relations, the guise but not the substance of the definition is changed: size is proportional to the probability that the plant receives infection at any instant from a uniform source in appropriate circumstances. both for general and quantitative relations there is a special case when disease is introduced into a crop by insects or other vectors. size, then, is the catchment zone of the plant for the insects. this accords with the meaning assigned to size in other circumstances; size is here a convenient fiction, the use of which gives precisely the same results as the use of numbers, which are a reality.reduction of size is discussed as a measure of control peculiar to systemic diseases.
STUDIES ON DANDELION YELLOW MOSAIC AND OTHER VIRUS DISEASES OF LETTUCE
Authors: KASSANIS B. 
Published: February 2008

The symptoms caused by dandelion yellow mosaic virus on cultivated lettuce, Lactuca serriola and L. virosa, are described and compared with those caused by lettuce mosaic virus. Lettuce is much more susceptible than dandelion to the yellow mosaic virus; no infections of dandelion were obtained by mechanical inoculation and only three by aphides, whereas infection of lettuce is regularly obtained by aphides and by inoculation provided an abrasive is used. Myzus ornatus, M. ascalonicus and Aulacorthum solani transmitted dandelion yellow mosaic virus but not lettuce mosaic virus, whereas Myzus persicae transmitted the latter but not the former. Nasonovia ribicola, the common lettuce aphis, transmitted neither. Aphides became infective only after feeding periods of some hours on the diseased plants and ceased to be infective within an hour of the infective feeding. Their efficiency as vectors was not increased by a preliminary starving period, as happens with Myzus persicae and lettuce mosaic virus. Lettuce mosaic virus was found in most samples of commercial seed, which explains its prevalence; no evidence was found for the seed‐transmission of dandelion mosaic virus and it is doubtful if it occurs, for infected lettuce are so severely affected that they rarely set seed.Cucumber mosaic virus was isolated from naturally infected lettuce.
EXPERIMENTS ON THE EFFECT OF CENTIMETRE‐LENGTH ELECTROMAGNETIC WAVES ON WOOD‐DESTROYING FUNGI
Authors: MACDONALD J. A. 
Published: February 2008

In an attempt to devise a practical method of killing wood‐destroying fungi, mycelia of Coniophora puteana and Merulius lacrymans were exposed to the beamed radiation from a standard Service radar transmitter transmitting pulses of radiation of wave‐length 9.1 cm. Growth of Coniophora puteana on malt agar films on glass slides was checked. Many superficial hyphae were killed. Exposures up to I hr. did not kill the mycelium of either fungus when growing on malt agar slopes or plates, or wood blocks. The only obvious effect was a check in growth whenever drying of the mycelium occurred.It is concluded that the rays have no lethal effect and injure the fungi only through drying of the mycelium due to the increase in temperature which they bring about.
THE BEHAVIOUR OF SOME NATURALLY OCCURRING STRAINS OF POTATO VIRUS Y
Authors: BAWDEN F. C. , KASSANIS B. 
Published: February 2008

Potato virus Y was obtained from field crops of potatoes in many strains which differed widely in virulence and caused diseases in the variety Majestic ranging from severe leaf‐drop streak to mild mosaic. The symptoms caused by these strains in seven potato varieties and tobacco are described and compared with those caused by the serologically related potato virus C. No changes were noted in the behaviour of any of the strains over three years, during which they were transmitted to many different plants.Potato virus C was not transmitted by Myzus persicae, the most efficient vector of other strains of virus Y. Nor was virus C transmitted by eleven other species of aphides, eight of which transmitted virus Y. The efficiency with which different species acted as vectors of virus Y varied greatly, and it is suggested that in some species only occasional individuals can transmit.Possible mechanisms for the evolution of viruses C and Y are indicated, and the effects of changes in virus, vector, and host on the prevalence of insect‐transmitted viruses are discussed.
OBSERVATIONS ON TAKE‐ALL AND EYESPOT DISEASES OF WHEAT IN YORKSHIRE
Authors: STOREY I. F. 
Published: February 2008

Wheat crops were surveyed in Yorkshire from 1944 to 1946 on farms where crops were reported to be unsatisfactory. Take‐all (Ophiobolus graminis (Sacc.) Sacc.) and eyespot (Cercosporella herpotrichoides Fron.) were both found to be present; the latter is the most serious trouble on the better wheat lands.The variation in the incidence of these diseases on selected farms during the three seasons has been compared.The effect of rotation has been examined; both diseases were found to be encouraged by too frequent cropping with wheat or barley. The incidence of disease in wheat crops following a 1‐year seeds ley was found to be influenced by the nurse crop used to undersow the seeds, and also by the time at which the ley was ploughed up. Oats were found to be preferable to either wheat or barley as a nurse crop, and in 1946 late ploughing considerably reduced the amount of eyespot disease present in the following wheat crop.A 1‐year ley is considered to be of too short a duration to ensure the disappearance from the soil of Ophiobolus graminis and Cercosporella herpotrichoides surviving from the previous crop, and a period of 2–3 years is suggested as being desirable.
WIREWORMS AND THE SUGAR‐BEET CROP: FIELD TRIALS AND OBSERVATIONS
Authors: JONES D. PRICE , JONES F. G. W. 
Published: February 2008

Observations on wireworms in the sugar‐beet crop during 1937–40 indicated the importance of alternative food, such as buried turf, weeds, excess seedlings and interdrilled wheat in determining the degree of injury to the crop.In 1938, out of thirty‐six recorded fields growing sugar beet after ploughed‐up grass only one suffered severe wireworm damage. Six of these fields were selected for resowing with sugar beet in 1939, and all suffered moderate or severe attacks. Several other fields in their first year from grass showed only slight damage. These observations were supported by an analysis of the Norfolk War Agricultural Committee crop records for 1940.Seven trials were carried out in 1939 to determine the effect of increasing the seed rate from normal (about 14–16 lb./acre) to 17–25 lb., and of interdrilling with wheat. In three trials, increasing the seed rate gave significantly higher plant populations before singling. It gave significant increases after singling in one out of two trials. However, in the one trial harvested the increase in ‘washed beet’ was only 7.6% and ‘total sugar’ 15%. Interdrilling with wheat at 40–70 lb./acre gave significant increases in the plant population before singling in three out of five trials, and after singling in three out of four trials. Increased plant populations both before and after singling were obtained in two other trials with alternating treatments. Increased seed rate and interdrilled wheat together gave greatly improved plant populations before singling in each of two trials and after singling in the one trial where such an observation was possible.
THE TOXICITIES OF THREE PETROLEUM OILS TO THE GRAIN WEEVILS
Authors: HEWLETT P. S. 
Published: February 2008

The toxicities of three petroleum oils to Calandra granaria L. and C. oryzae L. have been determined. The oils were Shell oil P31, Odourless Distillate (O.D.), and Pool burning oil (P.B.O.). At 20 and 25° C. C. oryzae was more resistant than C. granaria to a direct spray of P31. At 20° C. C. oryzae was more resistant than C. granaria to direct sprays of O.D. and P.B.O. The relative toxicities to both species of direct sprays of the three oils could be expressed as: P.B.O. < P31 ≥ O.D. ≥ P.B.O. C. oryzae was the species more resistant to films of P31 on Whatman no. 544 filter‐paper.Films of P31 or a P31/water emulsion on brick, and films of P31 on sacking and cement, were non‐toxic to C. granaria, but films of P31 on cement pretreated with gelatin were highly toxic to this species.Beetles that received doses of P31 a little in excess of those sufficient to knock them down rarely recovered completely. P31 probably suffocates the beetles by blocking their spiracles and/or tracheae.P31 appears to be the most useful of the three oils for the control of C. granaria. In practice it should be effective as a direct spray, though not as a film, and could therefore be used to control infestations in which beetles were exposed. Films of P31 on surfaces suitably pretreated might, however, be used for control.
RELATION BETWEEN PARTICLE SIZE AND SHAPE OF INSECTICIDAL SUSPENSIONS AND THEIR CONTACT TOXICITYL: I. D.D.T. SUSPENSIONS AGAINST TRIBOLIUM CASTANEUM Hb
Authors: McINTOSH A. H. 
Published: February 2008

Fairly coarse aqueous D.D.T. suspensions can be made by the exchange of solvent method. By varying the method of preparation the mean size of crystal in suspension can be altered. The principles involved are outlined, and methods and apparatus are described for the preparation of the following suspension types: colloidal D.D.T., a suspension containing elongated hexagonal plates, a suspension of somewhat elongated two‐dimensional aggregates of plate‐like crystals, and three suspensions of needle‐shaped crystals of different lengths. All the D.D.T. crystals are of the same fundamental crystal habit. These suspension types were selected to study the effect of both crystal size and shape on toxicity.The suspensions were tested against Tribolium castaneum Hb., using a recently developed dipping technique. It was shown that the results obtained were independent of any operation peculiar to the technique.Suspensions tested by a spraying method gave data similar to those obtained by dipping, except for certain anomalous results obtained where the crystals were considerably broken up in passing through the spray nozzle.Toxicity differences were assessed by the probit method. The lines obtained for the crystalline suspensions were generally parallel to one another, but the colloidal D.D.T. gave a line differing in slope from the others.The dipping tests showed that, within the range of crystal sizes up to about 400 μ, toxicity increased with increasing needle length; breadth was less important, but a suspension of needle‐shaped crystals was as toxic as one containing considerably larger plate‐shaped crystals at the same weight/volume concentration. Colloidal D.D.T. was less toxic than any crystalline suspension. Thus, taking the median lethal concentration for 400 μ needles as 100, the values for the other types were: for 120μ needles, 210; for plate aggregates (240 × 140 μ), 260; for 40μ needles, 390; for 60 × 15 μ plates, 510; and for colloidal D.D.T., 1700.These differences in toxicity were largely paralleled by retention of greater amounts of D.D.T. from the coarse suspensions than from finer ones; two extreme types were of almost identical toxicity, comparing the percentage kills produced by equal amounts of poison retained, and not by equal concentrations in suspension. The methods of carrying out these retention tests are described.