bluuebunny/crossref_metadata_2025 huggingface dataset:
Eyespot of wheat and barley in Scotland in 1944
Authors: Glynne MaryD.
Published: February 2008

In August 1944, eyespot (Cercosporella herpotrichoides Fron.) was found in ninety out of 121 autumn‐sown wheat crops distributed over twelve Scottish counties. It was abundant enough in forty fields to be likely to harm subsequent crops, and was causing obvious loss in eleven crops. The disease was found in seventeen out of eighteen spring‐sown barley crops, more than half the straws being infected in seven of them. About 4 % of the wheat inspected was lodged mostly by eyespot and about 38 % of the barley mostly non‐parasitically. Eyespot increased with the frequency of wheat and barley in the two preceding years, but a few infected crops occurred on fields where no wheat or barley had been grown for many years. In Scotland, where the atmosphere is more humid, eyespot tends to increase more rapidly than in similar rotations in England; lesions are found higher up the straw and the disease is much more prevalent on spring‐sown barley. The long rotations practised in Scotland prevent more extensive damage by eyespot.
Toxicity to rainbow trout and minnows of some substances known to be present in waste water discharged to rivers
Authors: Grindley J.
Published: February 2008

Toxicity to fish (rainbow trout or minnows) of solutions of several pure substances has been measured under controlled conditions. The substances (sodium arsenite, sodium arsenate, sodium picrate, sodium dinitrophenate, zinc sulphate, potassium chromate, potassium dichromate, ammonium chloride, and ammonium sulphate) were dissolved in distilled water, in Watford tap water, or in mixtures of distilled water and tap water.
Effects of atmospheric environment, before and after treatment, on the toxicity to insects of contact poisons. I
Authors: Potter C. , Gillham E. M.
Published: February 2008

Experiments were made on the effect of conditions before and after treatment on the toxicity to adult Tribolium castaneum Hbst. of the following contact poisons in the media stated: (i) pyrethrins, (2) lauryl thiocyanate, (3) nicotine‐all in aqueous medium, (4) dinitro‐o‐cresol in ethylene glycol, (5) Wakefield half‐white oil, (6) D.D.T. in Wakefield half‐white oil.

The difference in environment before spraying did not have any marked effect but, with the exceptions of nicotine and petroleum oil, all the toxicants used were more insecticidal when the beetles were kept under cool conditions after spraying. Nicotine showed little difference due to after‐treatment when an inverted filter funnel was used to confine the insects, but seemed markedly more toxic under cooler conditions of after‐treatment when the insects were confined in the dishes by means of muslin.

Wakefield half‐white oil, a non‐volatile petroleum oil, proved more toxic when the insects were kept under warm conditions after treatment than under cool conditions. The increase in toxicity of chemically active contact poisons under cool conditions of after‐treatment appeared to occur whatever the nature of the carrier, whether volatile or non‐volatile, water or oil.

In the substances tested, with the exception of nicotine under special circumstances, the increase in toxicity under cool conditions of after‐treatment occurred whatever the volatility of the poison.

The change in toxicity, when cool conditions were compared with hot, varied with the poison used. With nicotine in aqueous medium the change was relatively small, the toxicity under cold conditions throughout being 1‐23 times the toxicity under hot conditions throughout. At the other extreme with pyrethrins and terpineol in aqueous medium there was a large alteration, the toxicity under cold conditions throughout being about 7 times the toxicity under the hot conditions throughout.
Note on the effect of wireworms of the genera Agriotes and Corymbites on crop yields
Authors: Broadbent L.
Published: February 2008

Experiments were made to illustrate the regular falling off of yield of crops due to increasing wireworm populations under controlled conditions. The genus Corymbites was shown to cause as much damage as Agriotes; Athous was less harmful. The damage caused to various cereals by Agriotes is contrasted.
Simple laboratory and field apparatus for the production of accurate line drawings to scale
Authors: Staniland L. N.
Published: February 2008

Apparatus is described by the use of which accurate scale drawings may be made of plants or other biological material for the study of growth changes or the development of disease symptoms. The apparatus has other uses, e.g. enlargement of drawings, etc., and these are also described. Examples of drawings made with the apparatus are included.
The ecology of the larger fungi V. An investigation into the influence of rainfall and temperature on seasonal production of fungi in a beechwood and a pinewood
Authors: Wilkins W. H. , Harris G. C. M.
Published: February 2008

The present paper deals in a somewhat generalized way with the influence of environmental factors, particularly rainfall and temperature, on the seasonal production of fungus sporophores in a beechwood and pinewood, both situated near Newbury (Berks.), during a selected part of the seasons 1933‐6, and is intended to be complementary to the previous papers in the same series.
Investigation into the production of bacteriostatic substances by fungi Preliminary examination of more of the larger Basidiomycetes and some of the larger Ascomycetes
Authors: Wilkins W. H.
Published: February 2008

This paper may be regarded as an addendum to previous work along the same lines, more particularly the work which dealt with some 700 of the larger Basidiomycetes. Both Ascomycetes and Basidiomycetes were tested for their antibiotic properties by means of sporophore extract. Of the ninety‐nine fungi tested, twenty‐eight showed a positive and seventy‐one a negative reaction against the test bacteria, Bacterium coli and Staphylococcus aureus.
Diseases of the gladiolus III. Botrytis rot of conms and its control
Authors: Hawker Lilian E.
Published: February 2008

The probability that the three types of corm rot of gladioli, associated with Botrytis spp., described by Moore (1939) are phases of the same disease is discussed.

Control measures were of five types: (1) Measures to reduce the amount of active or dormant infection of the corms when lifted. Avoidance of heavy wet soil, ground in which gladioli had previously grown and shaded sites reduced the subsequent loss in storage. Relatively early lifting (during the first half of October) was beneficial. Rogueing of diseased plants during the summer and dusting of foliage with pentachloronitrobenzene dust (p.c.n.) gave some improvement, but further experiments are‐desirable. (2) Measures to reduce the development of the disease between lifting and storage. Early removal of adhering soil, cormels, roots, parent corms and old shoot and leaf bases (husks) gave good control. Rapid drying in warm, dry conditions was also beneficial, but washing the corms to remove soil was ineffective. Dusting with p.c.n. immediately after lifting and before cleaning gave a slight reduction in losses in two small‐scale experiments. (3) Pre‐storage fungicidal treatment of corms. Dusting with p.c.n. before storage gave good control, but almost complete control was obtained by steeping in a 01 % solution of mercuric chloride for 20 min. to 3 hr. This treatment has the advantage that it also controls hard rot (Septoria gladioli Passer.), scab (Bacterium marginatum McCull) and to a lesser extent dry rot (Sclerotinia gladioli Drayt.), but is liable to damage the corms. The safety limits are being worked out. (4) Conditions of storage. Corms should be stored in shallow trays in a dry, well‐ventilated shed, protected from frost. (5) Fungicidal treatment at planting time to protect the corm from soil infection. Mercuric chloride as a corm steep at this time gave only partial control, probably owing to rapid removal of the fungicide by leaching. Dusting with p.c.n. gave good results, not only in the protection of the old corm but in preventing infection of the new ones and the beneficial effect extended into the subsequent storage period. Soil treatment was not effective.
Further studies on the effect of disinfecting and bruising seed potatoes on the incidence of dry rot (Fusarium caeruleum (Lib.) Sacc.)
Authors: Small T.
Published: February 2008

The effect on dry rot of the potato of disinfecting seed potatoes with a proprietary organo‐mercury fungicide immediately before they were clamped on lifting, and on their removal from the clamps after 3 or 6 months' storage, has been tested in field trials during two seasons. The incidence of the disease in tubers stored in clamps has also been studied. The tubers used were of the susceptible varieties Ninetyfold and Doon Star, taken from crops grown in contaminated soil. In certain of the tests the natural contamination in the soil adhering to the tubers was reinforced by spraying each tuber with a spore suspension of the dry‐rot fungus.

Seed tubers not deliberately bruised on lifting, and whether dipped or not at that time, were practically sound after 3 and 6 months' storage in clamps except in one instance. On removal from the clamps, those not dipped on clamping continued to remain sound when carefully handled and stored for a further period in seed boxes, but they suffered either moderate losses if slightly bruised, or serious losses if severely bruised, at the time they were removed from the clamps. Tubers dipped immediately before being clamped yielded similar results, except that they remained sound when slightly bruised on removal from the clamps.

Tubers not dipped, but deliberately bruised either on lifting in July immediately before clamping or on reclamping in October, developed severe dry rot whilst stored in the clamps. The incidence of the disease was not influenced by the location of the tubers within the clamp.

In tubers not dipped at lifting and clamping time in July, but lightly bruised and immediately dipped on their removal from the clamps in October, the losses from dry rot were slight. Severe bruising followed immediately by dipping on their removal from the clamp in October, however, resulted in considerable losses.

Tubers not dipped at lifting and clamping time in July but, after 3 or 6 months' clamp storage, slightly bruised and immediately dipped, then severely bruised 2 days later, developed appreciable losses; but these losses were far less than in tubers treated similarly except that the dipping was omitted.

Tubers dipped on lifting immediately before clamping in July, and slightly bruised and immediately redipped on removal from the clamps in October, remained almost sound; but tubers severely bruised just before the second dipping in October developed a loss of 12%.

All the foregoing results were obtained with tubers taken from healthy clamps. Ostensibly healthy tubers taken carefully from clamps containing much dry rot became severely affected with the disease when further stored in seed boxes.
Molybdenum as a factor in the nutrition of lettuce
Authors: Warington Katherine
Published: February 2008

Lettuce grown in nutrient solution sometimes showed slight benefit on a dry‐weight basis from the addition of 0.1 p.p.m. Cr, Sr, Ti or V, while Zn was usually harmful. Addition of Mo at a similar concentration, however, exerted such a marked beneficial effect on both yield and appearance as to suggest that this element was essential for healthy growth. Confirmation of the response was not always obtained, and search was made for some factor which would account for the lack of uniformity in the results. Neither the season of the year, the variety, modifications in the nutrient solution, nor the addition of other trace elements appeared to be responsible, and further work is necessary for the elucidation of the problem.
Observations on the effects of browning (Polyspora Lini Laff.) of flax on seed production
Authors: Colhoun John
Published: February 2008

An account is given of observations made on the effects on seed production of the incidence of the browning phase of the disease of flax caused by Polyspora Lini Laff. The work was carried out during three seasons.

Disinfection of seeds before sowing exercises an effect on the average weight of the well‐developed seeds harvested, and the results obtained show that the intensity of the attack of browning in crops is inversely correlated with the weight of 1000 well‐developed seeds. When poorly developed seeds are separated from the remainder at harvest, evidence obtained in one year suggests that the percentage number of such seeds may be directly related to the incidence of browning in the crop. It was found in each of two years that more of the poorly‐developed than of the well‐developed seeds were contaminated with P. Lini. Evidence available for one year suggests that the viability of well‐developed seeds is not related to the incidence of browning.
The comparative toxicity of various contact insecticides to the louse (Pediculus humanus L.) and the bed‐bug (Cimex lectularius L.)
Authors: Busvine J. R.
Published: February 2008

A variety of substances has been tested by laboratory methods as insecticides against the bed‐bug and the body‐louse. The oil‐soluble samples were tested by the Potter tower method which gave the most accurate results. Certain liquids were tested by a simple dipping method, and solids insoluble in mineral oils were tested as aqueous solutions by the dipping method or as dusts.

Various organic thiocyanates were found to show similar relative toxicity to the louse and bug, but the pyrethrins were much more toxic to the latter. D.D.T. was highly toxic to both and Gammexane even more insecticidal, especially to the louse.

In the dipping tests, two types of toxic action were observed: an immediate physicochemical action and a delayed lethal action due to asphyxiation. Refined mineral oils kill lice by the latter method. Among the aqueous preparations, the emulsion of cresols known as Lysol was noteworthy for its ovicidal powers.

Some experiments were made with extracts of delphinium seeds, the insecticidal powers of which were shown to reside in the alkaloids.
Study of an infestation by Laemophloeus sp. (Coleoptera Cucujidae) in bulk wheat
Authors: Lucas C. E.
Published: February 2008

Physical and biological data are presented from an infestation by Laemophloeus sp. (unidentified but very near to L. minutus Oliv.) in bulk wheat contained in open‐topped silo bins. Much of the life history of this species is spent within the grains of wheat under the conditions of this infestation. It follows that the density of population of this species in whole wheat can be estimatedonly by breeding out or by determining the carbon dioxide output of the grain. Some larvae are free‐living for part of their lives. No regular relation has been found between the number of larvae free‐living at any time and the number of insects remaining within the grains. The proportion of the total population which is free‐living is least when the total population is greatest. There is some evidence that the grain contained a light infestation of Laemophloeus, fairly evenly distributed, before it was loaded into the silo bin. It is supposed that this was the source of the infestation studied. Factors which might be responsible for the uneven development of the population are discussed.
On making measurements in silo‐stored grain
Authors: Lucas C. E. , Glover R. S.
Published: February 2008

A sectional tubular steel sampler has been designed, with which samples of grain have regularly been obtained at 1 m. intervals to depths of 15 m. in normal grain. A new form of this sampler permits re‐closing of the sampling ports after filling, so that contamination of the samples can be avoided. Associated records of the grain temperatures and samples of the intergranular gases have been obtained at similar depths. Certain precautions to be observed in sampling from silo bins are emphasized. Observations are reviewed which show the extensive effects of granular segregation during movement. Material, such as extraneous seeds, holed grains, etc., segregates so that (a) it is delayed in the outfall whilst emptying bins, (b) it is more concentrated in the central column of the bin after filling, (c) in direct sampling it is scarcer in the first part of the sample to fall into the container, with the implication that the sample as whole is deficient in such material. Larger objects settle at the surface of the grain on a moving belt, whilst smaller ones sink between the grains. The consistency of the results suggests strong reasons for a reconsideration of the principles of sampling, either direct or indirect. Meanwhile, samples obtained by any one method are likely to prove fairly consistent inter se.
Further investigations on the value of electric heating of beehives
Authors: Butler C. G.
Published: February 2008

A set of twenty‐four colonies of honeybees was divided into three groups, two of which received different intensities of artificial heat, applied by means of specially designed heating frames placed in the middle of the brood chambers, from 2 Jan. to 16 Mar. 1942. Heating the colonies reduced the area of brood present at the beginning of May without noticeably affecting the consumption of carbohydrate stores and thus had an adverse effect on the colonies. This conclusion is in agreement with that reached as a result of earlier work (Butler & Cockbill, 1942.)

Colonies in hives fitted with top entrances were no stronger in the spring than colonies in hives with bottom entrances, nor did they show any significant difference in store consumption.

No significant brood chamber temperature differences were found in hives fitted with top entrances as compared with control hives which had normal bottom entrances.

During the period when heat was applied to the colonies by means of the heating frames the minimum brood chamber temperature was significantly higher in the heated hives than in the control, unheated, hives, this being especially marked in the case of the hives fitted with 6 W. heaters.

Throughout the experiment the minimum brood chamber temperature of all the hives showed a close dependence on screen temperature. During the preliminary period before the heat was turned on a change of 1d̀ C. screen temperature was associated with change of 0.92d̀ C. in the minimum brood chamber temperature in hives with top entrances, and a change of 0.86d̀ C. in hives with bottom entrances. After the heat was turned on the corresponding figures were 0.84d̀ C. for top entrance hives and 0.67d̀ C. for the bottom entrance hives.
The ecology and function of Protozoa in sewage purification
Authors: Neville A. , Barker M.Sc, Ph.D.
Published: February 2008

Seasonal recording of the Protozoa in various sewage disposal units has shown that, together with changes correlated with the degree of purification of the sewage, fluctuations occur as a result of the interplay of seasonal non‐specific factors and local specific factors. The incidence and abundance of Protozoa in each disposal plant would seem to be controlled by sewage ‘strength’ and characteristic local drainage. Fluctuations of the population, however, are limited by different factors in different seasons.

In the bacteria bed investigations a ‘weak’ sewage shows a decrease of a generally rich fauna during the periods of sloughing, a ‘strong’ acid sewage during sloughing shows an increase in an otherwise restricted fauna and where the sewage is medium in ‘strength’ and supports an abundant insect population the fluctuations of the Protozoa are dominated by the more active insect populations of summer and by temperature in winter. In this last‐named environment a significant inverse correlation between ciliate and insect frequency throughout the summer indicates the thoroughness with which the insect larvae devour the film; this may explain the summer reductions in certain groups of Protozoa.

In activated sludge channels conditions favour a uniform population which may vary in composition according to the purity of the sewage. Flocculation is most pronounced when protozoan populations comprise a restricted variety of ciliates and would seem to depend on a protozoan fauna since cultures of bacteria obtained from sewage did not flocculate unless Protozoa, free from or contaminated with bacteria, were added.

The protozoan populations of the two systems of disposal are compared in discussion.
Field trials of copper fungicides for the control of potato blight III. Low‐copper fungicides
Authors: Large E. C. , Beer W. J.
Published: February 2008

In trials at Beaford, north Devon, and at Galmpton, south Devon, in 1945. proprietary preparations of copper oxychloride, cuprous oxide, and cuprammonium, used at low‐copper dosage (0.063 % Cu), were compared with Bordeaux mixture at the same and at higher dosages for the control of potato blight under two commonly recurring conditions of disease incidence, respectively early and late, which were closely defined by foliage decay curves.

All the copper fungicides were tested with and without added adhesive of caseinate‐rosin soap type, and two sulphur fungicides: lime sulphur (1 in 50) and Dithane 14 (1 in 200) with zinc sulphate and lime, were also included.

The trials were made on four‐times replicated plots at both centres; special precautions were taken to avoid confusion of the observations by concurrent mineral deficiency and virus disorders; and the treatments were compared by three criteria: (1) direct foliage protection, (2) spray retention and (3) indirect effect on yield. The number of spray applications was reduced to a minimum to avoid masking the superiority of the better treatments, and timed as nearly as possible for maximum effect in relation to weather conditions. Thus two applications were given at Galmpton and three at Beaford.

None of the proprietary copper fungicides used at low‐copper dosage, with or without added adhesive, equalled plain (4.5.40) Bordeaux mixture in spray retention or direct protective effect; and none gave any significantly better protection than Bordeaux mixture at correspondingly reduced copper dosage (1.11/2.40).

With the few well‐timed and thorough sprayings given, however, the 1% Bordeaux mixture itself gave almost sufficient protection for the production of a full crop, and the trials indicated horticultural conditions under which low‐copper fungicides can be used with success, while pointing to the important factor of safety secured by using 1 % Bordeaux mixture in routine agricultural practice.

Both of the sulphur fungicides were less effective than i % Bordeaux mixture.
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.
A note on the relation of nematodes (Tylenchus tritici) to the development of the bacterial disease of wheat caused by Bacterium tritici
Authors: Cheo C. C.
Published: February 2008

Inoculation experiments using bacteria alone did not produce the bacterial disease of wheat: inoculations with mixed bacteria and nematodes were successful. The bacteria within the nematode galls retain their viability for 2 1/2 years. The bacterial disease is more damaging to the wheat plant than the nematode 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.
THIOCYANATE INSECTICIDES: THE RELATION BETWEEN KNOCK‐DOWN ACTIVITY AND CHEMICAL CONSTITUTION
Authors: GROVE J. F. , BOVINGTON H. H. S.
Published: February 2008

The results of an investigation into the relation between chemical constitution and the knock‐down activity and toxicity of thiocyanate insecticides are recorded. Linkage of the toxic thiocyano radical through a ketomethylene group to a lipoid soluble hydrocarbon residue gives rise to knock‐down activity. The most active α‐thiocyanoketones R.CO.CH2.SCN and thiocyanoacetates R. O. CO. CH2. SCN are too irritant to the eyes and nose for inclusion in domestic fly‐sprays. Thiocyanoacetates derived from saturated 10‐carbon alcohols, however, are non‐irritant to the mucous membranes while possessing moderately high activity. The mode of action of these compounds is 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.
OBSERVATIONS ON THE LIFE CYCLE OF XYLEBORUS FORNICATUS EICHOFF IN ARTIFICIAL CULTURE
Authors: GADD C. H.
Published: February 2008

The scolytid beetle, Xyleborus fornicatus Eichoff, which is an important pest of the tea bush in Ceylon, has been reared from egg to adult for the first time in artificial culture with its ambrosial fungus Monacrosporium ambrosium. Deaths in culture were numerous, yet sufficient data on the periods occupied in the different stages were collected to afford an opportunity for testing conclusions derived by the use of less direct methods. Results indicate that temperature materially affects the length of the life cycle and mainly controls the altitudinal distribution of the pest in Ceylon.
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.
A DIPPING APPARATUS FOR ESTIMATING THE TOXICITY OF INSECTICIDES IN LIQUID MEDIA
Authors: McINTOSH A. H.
Published: February 2008

An apparatus and a technique are described for the study of the effect of liquid insecticidal preparations by dipping insects in the toxic material. The method is applicable to quick‐settling suspensions and quick‐creaming emulsions as well as to solutions. Dipping is performed at constant temperature with end‐over‐end shaking; and the technique has the advantage over the other dipping methods that have been described in that handling of individual insects whilst wet is eliminated.
CALCIUM CHLOROACETATE AS A SOIL DRESSING AGAINST BEET EELWORM: HETERODERA SCHACHTH SCHMIDT, WITH CERTAIN ADDITIONAL OBSERVATIONS
Authors: JONES D. PRICE
Published: February 2008

Calcium chloroacetate at 3 and 6 cwt./acre produced significant increases in the yields of sugar beet (both washed beet and total sugar) in a trial on fen soil of the ‘skirt’ type infested with beet eelworm, Heterodera schachtii Schmidt. However, the material had no effect on the eelworm content of the soil whether measured by cysts, viable cysts or eggs and larvae. An instance is recorded of a significant drop in the level of the beet eelworm infestation in the presence of sugar beet.
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.
THE ROLE OF ANTIBIOTICS IN THE DECOMPOSITION OF SAWDUST: I. INHIBITION OF THE GROWTH OF CELLULOSE‐DECOMPOSING BACTERIA
Authors: JACOBS S. E. , MARSDEN A. W.
Published: February 2008

It has been shown that ‘deal’ sawdust contains substances which inhibit the growth of cellulose‐decomposing bacteria of the genera Sporocytophaga and Cellulomonas, the former being the more sensitive. The substances can be extracted with water or a mildly alkaline solution of inorganic salts, the latter being rather more effective. The extracted material is acidic but still exhibits activity even after neutralization, especially towards Sporocytophaga. Sawdust which has been extracted with water or the alkaline solution, or neutralized by admixture with calcium carbonate, no longer prevents the growth of Cellulomonas on added filter paper cellulose, although there is a delay before the attack becomes evident, but Sporocytophaga is still completely inhibited under all three conditions.
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.
THE ‘PHLOEM NECROSIS’ VIRUS DISEASE OF TEA IN CEYLON: III. FURTHER CHARACTERIZATION OF NECROSIS IN THE LEAF
Authors: BOND T. E. T.
Published: February 2008

Phloem necrosis due to the virus disease of that name in tea is fully described as it affects the leaf, on which diagnosis is chiefly based. Originating in the protophloem, it may extend inwards to the metaphloem and outwards to the pericycle, causing the breakdown and discoloration of the cells and their eventual death and obliteration, cell enlargement, and the production of new thin‐walled cells by hyperplasia. The condition is termed ‘true necrosis’ to distinguish it from the non‐pathogenic ‘false necrosis’, of unknown cause, which originates typically in the metaphloem but may have the same histological effects except for the absence of hyperplasia. In the petiole, the visual distinction between ‘true’ and ‘false’ necrosis on the basis of their position as seen in a transverse section of the bundle is relatively easy, and the continued use of this method of diagnosis is recommended. No such distinction can reliably be made in the midrib, where ‘false’ necrosis often occurs in the same position as ‘true’ necrosis, i.e. immediately within the pericycle. This is interpreted ontogenetically in terms of the smaller total width of the phloem in the midrib as compared with the petiole bundle; it effectively prevents the use of the midrib for diagnosis. The observations are discussed in terms of the inherent properties of the phloem, as affected by viruses and other agencies reported to have caused necrosis, among plants in general.
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.