bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies upon the copper fungicides: VII. The solution of copper from dressings on the pea seed
Authors: Wain Br R. L. , Wilkinson E. H.
Published: February 2008

During the process of swelling pea seeds yielded substances to water which were capable of dissolving the insoluble copper dressings normally applied to the seed to prevent ‘pre‐emergence damping off’. This occurred under conditions in which soil factors were eliminated and irrespective of whether the dressing was on the surface of the seed or treated separately. Copper was readily taken into solution from dried 4:4:50 Bordeaux Mixture by water in which peas had been soaked, a circumstance which proved that the formation of soluble complex forms of copper was involved.

A chemical investigation on the solution obtained by soaking peas in water showed that volatile acids or their salts were present together with a protein‐like material in colloidal solution. The occurrence of amino derivatives and other nitrogenous materials as well as carbohydrates was indicated and evidence of the presence of asparagine and citrate was also obtained.

The suggestion is made that both the fungicidal and phytocidal actions of insoluble copper dressings on pea seed depend largely on the effect of the pea seed exudates, notably colloidal protein‐like material and certain amino derivatives, in bringing copper into solution.
Studies upon the copper fungicides: VIII. The penetration of copper into germinating peas
Authors: Wain R. L. , Wilkinson E. H.
Published: February 2008

Three varieties of pea seed showed less damage when treated with solutions of simple cupric salts than with solutions of equivalent strength in which the copper could occur in complex form. On adding supplementary pea exudate to copper sulphate solution, thereby converting some cupric to complex copper, greater damage was caused. In spite of the greater phytotoxicity of complex forms of copper, the copper intake by the seeds was less. Sealing of the micropyle had little effect on the water and copper intake of peas.

Colorimetric tissue tests on treated peas indicated a high concentration of copper in the testa and the embryonic radical with only small amounts in the cotyledonary tissues. These observations were largely confirmed by chemical analyses‐on the test as, cotyledons and embryos of copper treated peas.

The results suggest that when copper dissolves from dressings on pea seeds much becomes fixed on the testa, so providing fungicidal protection. The soluble complex forms of copper produced by pea exudate are markedly phytotoxic and injury to the embryonic radical is regarded as the main cause of damage to peas.
The mode of action of sheep dips
Authors: Ph.D. E. T. Burtt, M.A.,
Published: February 2008

A study was made of the action on the tick (Ixodes ricinus L.) of some toxic substances used in dips. Methods are described of attaching ticks to limited areas on the sheep and of suspending ticks for individual tests.

Chemical potentials rather than concentrations should be used in comparing the toxicity of different solutions. Phenol is less soluble in P31 paraffin oil than in water, and a solution of phenol in P31 paralyses the tick more rapidly than the same concentration in water. Solutions of phenol in paraffin and water which are in equilibrium show the same effect on the tick. The potentials are the same, but the concentrations are different.

Each toxic substance tested acts more rapidly at a given concentration in a medium in which it is less soluble. Acid solutions of arsenious acid act more rapidly than alkaline. Solid arsenious oxide as crystals or as a deposit on wool acts more slowly than sodium arsenite under the same conditions, owing probably to its slow rate of solution. Sodium arsenite and arsenious oxide readily penetrate the tips of the feet, and sodium arsenite readily penetrates the dorsal surface of the tick.

Previous work on arsenical dips and the contact toxicity of wool dipped in sodium arsenite indicate that arsenic is a contact and not a stomach poison to ticks.

Phenols are toxic at low concentrations in water, but their greater solubility in wool fat and rapid evaporation from thin films explain their ineffectiveness as dips.

DDT (2, 2 bis‐p‐chlor phenyl 1, 1, 1, trichlorethane) penetrates the feet of the tick more readily than the rest of the body surface. DDT acts more rapidly at 1% in paraffin oil (solubility 1‐3%) than in sesame oil (solubility 10%). Saturated solutions have the same effect. Similarly, vaseline solutions are more effective than solutions in lanoline.

Rotenone penetrates the feet of ticks more rapidly than the back. Larval ticks are more rapidly intoxicated by 01% solutions in olive oil (solubility 0.2 %) than 0.1% solutions in castor oil (solubility 1‐2%). Saturated solutions have the same effect.

The importance of a knowledge of the site of entry of insecticides into the organism is stressed.

The less soluble the substance in the medium, the less is needed to give a high chemical potential and the more rapid will be the penetration of the organism. With low solubility, however, a small loss by diffusion causes a large fall in potential. Solubility is analogous to capacity. In practice, media will be needed in which the toxic substance is neither so soluble that a wasteful amount is needed to produce a high potential nor so insoluble that losses by diffusion cause large falls in potential.

The carrier activity of different oil bases for insecticides and the synergistic action of insecticides applied together may in part be due to changes in solubility and hence chemical potential.
The influence of periodic fallowing on the prevalence of viable weed seeds in arable soil
Authors: Brenchley Winifred E. , Warington Katherine
Published: February 2008

In view of the favourable reduction in the weed‐seed population on Broadbalk wheat field (Rothamsted Experimental Station) by the 2‐year fallows between 1925 and 1929 a cyclic fallowing of one section out of five per year was adopted to maintain control over the weeds. Annual samples for determining the weed seeds were taken from plots receiving farmyard manure, minerals and sulphate of ammonia together, and minerals and sulphate of ammonia in alternate years.

The numbers of seedlings obtained were grouped to show the reduction in weed‐seed population during fallow and the behaviour of various species in succeeding years. By this grouping the effect of the variable seasonal and cultivation factors is greatly reduced, as several years are included in each figure.

Most species are reduced by fallow, rise more or less rapidly during succeeding years, and are again reduced by a later fallow, usually to a lower level than by the first. Alopecurus agrestis showed the greatest variation from year to year. Papaver rhoeas was the outstanding exception to the general rule, as, once reduced by fallow, it failed to reassert itself except in a few cases, and was further reduced by the later fallow. These two species, with Alchemilla arvensis, Veronica arvensis and Medicago lupulina, contributed about 90% of the total seeds.

Alternate manuring with minerals and sulphate of ammonia greatly influenced the production of weed seeds. With most species nitrogen induced heavier seed production, as was shown by the average number per section compared with those produced with minerals. Alopecurus agrestis, Alchemilla arvensis, and usually Papaver rhoeas responded thus, Veronica arvensis was the only one of the main species to behave irregularly, whereas Medicago lupulina showed a reverse response, being more benefited by minerals than nitrogen.

In the first year after fallowing the crop and weeds alike were usually able to benefit by the stored fertility and did not appear to interfere with one another except where farmyard manure was used, when the competition of the crop at first prevented the weed‐seed population from rising. In the later years the crop tended to decrease, and the weeds to increase, until the balance was restored by another fallow.

Field observations, as well as laboratory samples, have shown a steady improvement in the cleanness of Broadbalk field, the most noticeable reduction being in poppies. The various weed species fall into definite groups, in two of which the reduction or increase in numbers induced by fallowing is maintained, while in the third there is an irregular increase and decrease in numbers over a period of years.

The general conclusion is that the fallowing of one section per year has fully justified itself, as the total weed‐seed population has not only been kept in check, but has also been gradually decreased during the 15 years the system has been applied.
A comparison of Fusarium avenaceum and Fusarium caeruleum as causes of wastage in stored potato tubers
Authors: Moore F. Joan
Published: February 2008

Fusarium avenaceum is reported for the first time as a cause of rotting of potato tubers in Britain. The progress of rotting in tubers infected with F. avenaceum has been compared with dry rot due to F. caeruleum in the laboratory, clamp and potato store. Of the four varieties, Majestic, King Edward, Doon Star and Arran Pilot, tested for susceptibility, King Edward was the most susceptible to F. avenaceum and Doon Star to F. caeruleum.

Optimum temperatures for growth on potato‐dextrose agar were 20‐25d̀ C. for F. avenaceum and 20d̀ C. for F. caeruleum; maximum temperatures were > 30 and 30d̀ C. respectively. For infection of wounded potato tubers, cardinal temperatures for F. avenaceum were similar to those on agar, but for F. caeruleum the optimum was 15d̀ C. and the maximum 25d̀ C. The optimum temperature for rotting tended, with both species, to be higher in the more susceptible potato varieties. At low temperatures F. caeruleum caused quicker rotting than did F. avenaceum, even though its rate of growth on agar was scarcely more than half that of the latter.

High humidity favoured rotting especially by F. avenaceum; F. caeruleum was more tolerant of relatively low humidity. Both species caused quicker rotting in the clamp than in store, even though there was no appreciable difference in mean temperature between the clamp and the store. This was attributed to the higher atmospheric humidity in the clamp.
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 of bruising and of disinfecting (‘dipping’) seed potatoes with a proprietary organo‐mercury preparation on the incidence of dry rot in them was tested in field trials during three seasons. The tubers used were of the susceptible variety Ninetyfold, taken from crops grown in contaminated soil, harvested immature in July to early August each year under farm conditions, and stored in boxes.

Seed tubers not deliberately bruised, whether dipped or not at lifting time, remained practically sound until planting time in the fallowing season, if left undisturbed in their boxes.

Tubers deliberately bruised, either at digging time or 1‐2 weeks later, but not dipped, developed severe dry rot with few exceptions. The disease had run its course by mid‐October. When undipped, sound tubers were bruised in October, they contracted severe dry rot, but dipping such tubers immediately before bruising reduced the loss satisfactorily in five out of six trials.

Tubers bruised at digging time and immediately dipped suffered little from dry rot in almost all cases. Delayed dipping of bruised tubers checked the disease in some trials but not in others. Seed tubers severely bruised 1‐2 weeks after being dipped remained practically sound except in one instance, whereas tubers severely bruised approximately 3 months after being dipped, subsequently developed severe dry rot in four out of six tests, unless they had been redipped immediately before they were bruised.

Inoculation of healthy tubers with soil samples showed that the fungus is widely distributed in potato fields in Cheshire. Dipping killed all, or almost all, of the fungus in the soil adhering to the seed tubers.

The results are discussed and suggestions are made for further investigations and for practical control measures.
Water plants in the Gezira canals: A study of aquatic plants and their control in the canals of the Gezira cotton area (Anglo‐Egyptian Sudan)
Authors: Andrews F. W.
Published: February 2008

The geographical position and climatic conditions of the Gezira cotton area are briefly described. A description is given of the Blue Nile river, and Sennar Reservoir. The common water plants of die latter are listed. It is shown in the case of five of these plants that they tend to be divided in those that occur in shallow water and those that prefer deeper water. Details of the annual rise and fall of the water of the Reservoir are also given.

The system of canalization in the Gezira is described and details given of the method of irrigation. A list is given of the common water plants in the Gezira canals, and their distribution over the canalized area is discussed. A comparison is made of the water flora of the canals of Egypt with those of the Gezira.

A system of small experimental canals was used to study the life history of the more important water plants in the Gezira canals. Details are given of the extent of the spread of the plants in these canals during a period of 14 months. It was found that abundant growth and seed formation occurred when clear water was entering the canals, but that the bulk of the vegetative part of the plants tended to die when turbid flood water arrived. Abundant seed germination occurred during the turbid water period. Drying the canal bed for 3 1/2 months had little effect on the final quantity of weed developed in the canals when they were refilled. Seed remained viable after 3 1/2 months' dry exposure. Removal of the surface soil from the dry canal bed produced no significant control of the water plants when water again entered the canals. A short flush of water was allowed to flow down the dry canal bed. It was hoped that the seed would germinate and the seedlings be killed by exposure after the flush had ceased. The effect of this treatment on the subsequent plant growth was negligible.

Laboratory experiments on the more important water plants showed that the vegetative part of the plants was killed after 8 days' dry exposure to the sun and that mercuric chloride, mercuric chloride‐iodide, and sodium arsenite in a concentration of 1/10,000 killed all plants after immersion in the poison solution for 5 days. At a concentration of 1/100,000 and immersion for 7 days none of these poisons was able to kill Potamogeton nodosus Poir. Work on poisons was discontinued for reasons stated in the text.

A short account is given of plants that invade the canals from the banks.

The problem of water plant control is discussed, and it is shown that the most hopeful method of control would be a system whereby all infested canals are cleared at regular intervals designed to prevent seeding during the clear‐water period and to remove seedlings during the flood‐water period. The application of this method in the Hag Abdulla Subdivision is described. The successful control that resulted reduced the weeding costs by half.
The suppression of one plant virus by another
Authors: Bawden F. C. , Kassanis B.
Published: February 2008

Severe etch virus prevents die multiplication of potato virus Y and Hyoscyamus virus 3 and replaces them even in plants in which they are established. Mild etch virus reduces the concentration of potato virus Y but does not suppress it completely. Cucumber virus 1 multiplies normally in mixed infections with any of the three other insect‐transmitted viruses. Possible implications of these results on the mechanism of virus multiplication are discussed; it is suggested that these viruses inactivate in cell sap at approximately the same rate as they denature in vitro.

No differences were found between the stability of antibodies to viruses with different properties.
The influence of crucifers and mustard oil on the emergence of larvae of the potato‐root eelworm, Heterodera rostochtensis Wollenweber
Authors: Ellenby C.
Published: February 2008

Hatching experiments were carried out with cysts of the potato‐root eelworm. The effect of solutions of potato‐root excretion mixed with root excretions of six types of crucifer seedlings was studied. With cress, white mustard, and black mustard, the emergence of larvae in the mixed excretions was very much less than that from control cysts in potato‐root excretion alone. On subsequent return to potato‐root excretion alone, larval emergence was found to be unimpaired in the case of white and black mustards; in the case of cress, however, the total emergence differed significantly from control. Similar effects, of both types, were obtained with certain dilutions of ally isothiocyanate, the mustard oil of black mustard seed, in potato‐root excretion.
The infected root‐hair count for estimating the activity of Plasmodiophora brassicae Woron. in the soil
Authors: Samuel G. , Garrett S. D.
Published: February 2008

A method is described for estimating the relative numbers of Plasmodiophora brassicae spores germinating in different soils, by counting infected root hairs. Cabbage seedlings are grown for 1 week at 25d̀C. in glass tumblers of the infected soils; after washing out, the tap roots are stained in 1% aceto‐carmine and a count is made of the number of root hairs containing zoosporangia of P. brassicae, along 2 cm. of root. It is shown that by this method it is possible to study, for example, the action of different bases in inhibiting root‐hair infection; the main inhibiting factor was found to be soil alkalinity, however produced. Other factors were found to influence infection in lesser degree; thus the number of infected root hairs was reduced in soils receiving N/10 sodium and potassium chlorides in place of distilled water. Root‐hair infection was also inhibited by low soil‐moisture content.
On the spread of crinkle in Royal Sovereign strawberries in south‐west England
Authors: Beaumont A. , Staniland L. N.
Published: February 2008

Observations at periodic intervals on marked plants in strawberry plantations in south Devon showed that the maximum appearance of crinkle symptoms occurs in June and July, in which months rogumg and inspections should be completed. The data suggest that infection in summer by apterous aphides passing on to neighbouring plants is probably the principal cause of spread.
Observations on the biology and experiments on control of the mangold fly (Pegomyta betae Curtis) on sugar beet
Authors: Roebuck A. , Baker F. T. , White J. H.
Published: February 2008

The fly (Pegomyia betae Curtis) was studied in its ecological and phenological aspects in central Nottinghamshire, and experiments on the lines of Continental workers, using sodium fluoride and molasses spray, were carried out.

It is shown that some pupae from the second generation‐ fail to emerge in the late summer but emerge in the spring of the following year, rather earlier than the pupae resulting from the third generation. The flies resulting from this early emergence are less fertile than those appearing later.

Methods of control discussed include cultural, biological and chemical means. Delayed drilling (not before mid‐May) helps to avoid the attack of the first generation. A rapid increase in number of parasites was observed and resulted in the annihilation of a large population of the fly. Treatment with molasses/sodium fluoride bait spray gave promise of control.
A simple automatic window‐opening device for temperature control in greenhouses
Authors: Heath O. V. S. , Whitcher E. J.
Published: February 2008

The apparatus described opens greenhouse windows within 2 min. of the closing of a thermostatically controlled electric circuit, and shuts them with a time lag of 12 min. after the circuit is broken. Power is consumed, during the time that the circuit is closed only, at about 250 W.; the apparatus can readily be extended to operate more windows or other similar devices and is easily adaptable to existing greenhouses.
Rhizomatous grass weeds and Ophiobolus graminis Sacc
Authors: Ph.D. Alan G. Walker,
Published: February 2008

An account is given of the infection of grass weeds by Ophiobolus granwm in a wheat crop affected by the disease. It was shown that the fungus was carried by the rhizomatous grasses, Agropyron repens and Agrostis spp. and also by Holcus lanatus. Examination of these showed the importance of Agrostis spp. in carrying over the mycelium under field conditions.
The nature and distribution of various forms of nitrogen in the potato
Authors: Street H. E. , Kenyon A. E. , Watson G. M.
Published: February 2008

The distribution of nitrogen fractions in the organs of King Edward potato plants harvested at intervals during the growing season has been determined. A general picture of the nitrogen distribution is presented and certain problems suggested by the data are discussed.

Each organ of the plant shows a uniformity in its nitrogenous composition during the whole season of active growth. The seed tubers are characterized by their high content of non‐protein nitrogen. This fraction yields the greater part of the nitrogen withdrawn from the seed tubers; the amide, amino and ‘other nitrogen’ fractions all being markedly depleted. The severely depleted tubers retain some 20% of their initial nitrogen content.

The roots are rich in non‐protein nitrogen, in which nitrate nitrogen is an important fraction. The roots from ammonium sulphate‐treated plots had a higher total nitrogen content than those from untreated plots, due to accumulation of ammonia nitrogen.

The ‘tops’ have a higher nitrogen content and a higher proportion of protein than the roots. There is an increase in protein content and a decrease in non‐protein nitrogen in passing from stems, to petioles, to leaf laminae. The depleted tubers and roots and stems have a uniform low‐protein content of the order 0.4‐0.6 mg. protein nitrogen per g. fresh weight.

Asparagine and glutamine occur in approximately equal amounts in the seed tubers and roots. Glutamine is more completely withdrawn than asparagine from the tubers, and in the ‘tops’ it constantly exceeds asparagine in amount.

A study of the concentration gradients, from leaves to petioles, to stems, to stem bases and new tubers, of the fractions of the non‐protein nitrogen focuses attention upon the ‘other nitrogen’ as containing the organic nitrogen most actively involved in translocation.

The concentration and total content of the glycoside solanine in the different organs has been determined at each sampling.
Varietal differences in susceptibility to potato virus Y
Authors: Bawden F. C. , Kassanis B.
Published: February 2008

In addition to giving different kinds of symptoms when infected with potato virus Y, individual potato varieties also differ in their susceptibility to infection, in the concentration of virus attained in their sap, and in their efficiency as sources of virus for aphides. Their relative susceptibility in the open when exposed to equal chances of infection is correlated with the ease with which they become infected when colonized with infective aphides, and can be assessed from tests made under glass. Methods for making such tests are described; these need few tubers and give reproducible results. It is considered that they could be applied in studying the inheritance of this type of resistance and to test the behaviour of new seedlings. The American variety Katahdin was the most resistant of those tested, but there were significant differences between commercial British varieties.

In the open, all varieties were equally colonized by aphides and resistance to infection with virus Y was not correlated with resistance to leaf roll.
Resolution of strawberry virus complexes by means of the aphis vector Capitophorus fragariae Theob
Authors: Prentice I. W. , Harris R. V.
Published: February 2008

Aphides (Capitophorus fragariae) were fed for periods of up to 24 hr. on strawberry plants infected with mild crinkle, severe crinkle or yellow‐edge and then transferred to plants of the wild strawberry, Fragaria vesca, or of the cultivated strawberry, variety Royal Sovereign. On F. vesca the symptoms produced were chlorotic speckling, distortion and dwarfing of the leaves, varying in intensity', and on Royal Sovereign scattered, inconspicuous, diffuse, chlorotic spots.

The symptoms from all three sources of infection were similar and were indistinguishable from those of mild crinkle of Harris & King. The virus thus selectively transmitted is tentatively concluded to be the mild crinkle virus.

The virus was transmitted after feeding periods of 1 hr. or more and did not generally persist in the vector for more than 3 hr.
Field trials of copper fungicides for the control of potato blight II. Spray retention
Authors: . E. C. Large , Beer W. J. , Patterson J.B.E.
Published: February 2008

Spray‐retention estimations were made during four seasons at Dartington in south Devon, on maincrop potatoes, twice‐sprayed, as in farm practice, with about 120 gal./acre for the first application and 160 gal. for the second.

Evidence is given concerning the limits of reliability of the disk method of leaf sampling; and an alternative method, batten.' washing, is described.

With from 2,1/2 to 3,1/2 in. of rain over test periods of 3‐4 weeks, 1% Bordeaux mixture showed about 40 % spray retention. Cuprous oxide and copper oxychloride sprays at the same copper dosage but compounded with sulphite lye or other water‐soluble dispersing agent showed less than 20% retention. Compounding of these materials with an insoluble sticker (bentonite) improved the adhesion.

The percentage retention of 1/2% Bordeaux mixture was found to be less than that of the usual 1 % mixture, but adequate spray deposits could be maintained with this and other low‐copper fungicides by more frequent applications.

A rapid method for determining total expanse of foliage in the field is described, and the importance of such determinations in connexion with spray‐retention trials, and practical spray timing, is stressed.

Experiments were made to determine whether any copper is absorbed by potato leaves from the spray deposits. Absorption, or acid‐resistant adsorption, of the order of 0.02 mg. Cu/120 sq.cm. of leaf area was indicated.
A method of estimating the numbers of soil Protozoa, especially amoebae, based on their differential feeding on bacteria
Authors: Singh B. N.
Published: February 2008

Cultural methods of estimating protozoal numbers in soil based on a dilution technique have suffered from two main sources of error: first, the use of too few replicate cultures and, secondly, the uncertain quality of the bacterial food supply. A method is described of using glass cells to set up 8 replicate cultures in one Petri dish, employing pure bacterial cultures spread over a non‐nutrient agar base to provide a standard and suitable food for the Protozoa. The selection and testing of suitable bacterial strains as food supply is described. Tests for the ‘recovery’ of counted suspensions of Protozoa added to sterilized soil were made; the results of these are given and the limits of experimental error in the method are discussed.
The analysis of a factorial series of insecticide tests
Authors: Finney D. J.
Published: February 2008

When a set of insecticidal toxicity tests yields parallel regression lines for the relationship between mortality probit and log dose, the potencies of the materials or conditions under test may be compared purely in terms of log L.D. 50's. The purpose of this paper is to suggest that, when tests have been made with all combinations of several different factors, standard methods for the statistical analysis of factorial experiments may be adapted to the examination of the relative potencies.

Data obtained by Potter & Gillham (1046), in a 2′ factorial experiment on alternative storage conditions for insects before and after spraying and the adjuvant action of terpineol in a pyrethrins spray, are used in an example of the computations. Details are given of the test of parallelism of the regression lines, the factorial analysis of the log L.D. ′50s, the estimation of the mean effects and interactions and their standard errors, the significance tests, and the preparation of summary tables.
Diseases of the gladiolus IV. Note on the incidence and control of scab disease {Bacterium marginatum McCull.)
Authors: Hawker Lilian E.
Published: February 2008

Stocks of imported gladioli which originally contained a proportion of scabbed corms showed very little carry‐over of the disease during the eight growing seasons 1938‐45. Carry‐over was greatest on ground where gladioli had been planted for several successive years.

The incidence of the disease was greatest in the hot summer of 1940.

Treatment with mercurial fungicides just before planting time gave good control. Two non‐mercurial fungicidal dusts were less effective.
Dry rot of potato (Fusarium caeruleum (Lib.) Sacc.) Effect of planting infected and contaminated sets on plant establishment
Authors: Small T.
Published: February 2008

The effect on plant establishment of planting infected and contaminated sets of susceptible varieties has been studied in field trials from 1942 to 1945.

Healthy whole sets, and whole sets inoculated internally 3 days before planting, yielded good stands, whilst whole sets with obvious dry‐rot lesions present at planting time produced gappy crops.

Healthy cut sets gave satisfactory stands except in one test with Doon Star, whilst sets cut with a contaminated knife at planting time yielded only a few misses in 1943 but many in the unfavourable 1944 season and in 1945.
The relation between the contamination of flax seed with Polyspora Lini Laff. and Colletotrichum linicola Pethybr. & Laff. and the incidence of disease in the crop
Authors: Colhoun John
Published: February 2008

Using naturally contaminated seed it is shown that the incidence of the seedling, stem‐break and browning phases of attack by Polyspora Lini Laff. in flax crops is related to the contamination of the seed with the parasite, the relationship being closer at low or moderate than at high levels of seed contamination. Heavy attacks of the disease did not occur when the number of contaminated seeds was less than 5%. A similar relationship was found to exist between the contamination of seed with Colletotrichum linicola Pethybr. & Laff. and the incidence of seedling blight in the crops.
Bionomics of the carrot fly (Psila rosae Fab.): II. Soil populations of carrot fly during autumn, winter and spring
Authors: Wright D. W.
Published: February 2008

The behaviour of the carrot‐fly population in the soil during autumn and winter has been investigated in East Anglia over the three seasons 1943‐5. The results show that the pest overwinters in both the larval and pupal conditions, and that the proportion of the individuals in each stage varies from crop to crop and from season to season. Samples taken from a May (1943) sown plot showed that pupation, which was 452% complete in October, rose to 742% in March and was not complete until late April. From a June (1944) sown plot of carrots samples showed a rise in percentage pupation from 8‐6% in October to 935% in March, the process probably being complete by early April. The changes in proportion of the soil larvae, carrot larvae and puparia in both the May and June plots were followed and are shown graphically. The changes in the size groups of the soil larvae and in the carrot larvae were also traced. The immature larvae persist longer in the carrots than in the soil. The size composition of the larvae from the soil of the June (1944) plot was recorded over the period September to April and the results are given graphically. Samples taken in October 1945 contained highly organized puparia from which flies emerged in a few days. These flies (third generation) gave rise to progeny which overwintered in the larval condition. The population in December 1945, composed chiefly of second generation puparia and third generation larvae, was very similar to that occuring in the previous two years. Mortality in the overwintering carrot‐fly larvae and puparia varied considerably but was frequently heavy. The principal agencies concerned were an hymenopterous insect, Dacnusa gracilis Nees., and fungus and bacterial diseases. Other insect parasites occasionally important were Loxotropa tritoma Thorns, and Aleochara sparsa Heer. Nematode parasites were also recorded.
The provision of supplementary food to hive bees
Authors: Butler C. G.
Published: February 2008

Sucrose syrup is less satisfactory than honey as a winter and spring food for bees: a mixture of approximately equal parts of honey and syrup is of almost the same value as honey alone.

Feeding confined to early autumn induced the strongest spring development of colonies; syrup feeding in the spring may retard colony development, and food supplied at this time is apparently wasted. Feeding with syrup and pollen is advantageous only when a colony is lacking in stores of carbohydrate and protein.

A total of four British Standard brood combs full of pollen provides sufficient protein for a colony on B.S. equipment from autumn until April: the best results were obtained by providing colonies on eleven B.S. combs, in early autumn, with 35‐40 lb. of honey, or honey and concentrated sucrose syrup, and four brood combs full of pollen.
Studies on Oscinella frit Linn: Notes on the resistance of cereals to infestation
Authors: Cunliffe Norman , Hodges D. J.
Published: February 2008

Resistance of the oat plant to infestation by the frit fly is not correlated with either carbohydrate or silica content. By increasing the number of eggs placed on an oat variety, proved to be resistant in the field, its resistance can be reduced below that of the most susceptible type, the inference being that resistance is indirect and due to some form of plant attractiveness which determines extent of oviposi‐tion. Oviposition studies in the held show that oviposition on susceptible varieties of oats, such as Victory and Star, is three times as great as on resistant types, such as Summer and Spet; selections from crosses between susceptible and resistant types, intermediate in resistance, receive a proportionate number of eggs, resistance being inherited. Some oviposition data for wheat and barley are included. Fly orientation is not controlled by either chemotaxis or hydrotaxis, but is influenced by stereotaxis; negative results have so far been obtained from phototaxis studies. Trie resistance to infestation in the field of twenty‐two named varieties of oats is compared with that of a standard variety; none is so resistant as Summer, while Richland Iowa 411 and Eagle approach Sandford in possessing moderate resistance. The marked difference between Victory and Summer in regard to stem infestation in spring is not extended to the grain infestation, no marked difference being observed. Susceptibility to sterility of grain shows significant differences, and there is an indication that segregation may be transgressive. Late nitrogenous dressings have no effect on extent of either grain infestation or sterility. The recovery capacity of Sandford almost equals that of Gris de Houdan, a good tillering variety. Maize exhibits varietal differences in extent of resistance to attack. The protective effect of D.D.T. is considerable, but not complete.

The essential statistical analyses have been lodged with the Librarian of the British Museum. A statement of significance of result means significance at the 1 % point of distribution.
The assimilation of ammonium and nitrate nitrogen by detached potato sprouts
Authors: Street H. E. , Kenyon A. E. , Watson G. M.
Published: February 2008

Detached potato sprouts have been grown successfully in ammonium and nitrate culture solutions for 5 weeks. The pH and concentration of each solution were such that a similar rate of nitrogen absorption took place from both. The general appearance, increase in fresh and dry weight and the nitrogen distribution in the shoots and roots of sprouts removed at intervals for analysis have been compared. Sprouts, previously grown in nitrate or ammonium culture solutions, have been transferred and grown for 8 days on a minus‐nitrogen culture solution, and the changes in appearance, growth rate and nitrogen distribution followed in a similar manner.

The importance of aerating the culture solution, of frequent solution renewal and of an adequate supply of soluble iron for successful solution culture of potato sprouts is stressed.

The ammonium sprouts developed more evenly and ultimately more rapidly than the nitrate sprouts. The nitrate sprouts were a lighter green, showed a tendency for the lower leaves to yellow and dry up and, when transferred to the minus‐nitrogen solution, rapidly developed symptoms of nitrogen deficiency. Evidence is presented that, in young potato sprouts, the rate of nitrate reduction and assimilation are a serious limiting factor to the availability of nitrate nitrogen for protein synthesis.

Ammonium assimilation takes place actively and mainly in the roots and stem bases. Nitrate assimilation takes place in both shoot and roots, but is more active in the shoot. Absorption of nitrate ions can take place even when a much higher concentration of nitrate ions is present in the root cells than in the external solution. The initial nitrate nitrogen present in the sprouts is not appreciably utilized during culture on ammonium solution.

The ammonium shoots as compared with the nitrate shoots have a higher content of total nitrogen, protein nitrogen, non‐protein organic nitrogen, amide and amino‐acid nitrogen, but a lower content of inorganic nitrogen. The nitrate roots as compared with the ammonium roots have a higher content of total nitrogen, protein nitrogen and inorganic nitrogen, but a lower content of non‐protein organic nitrogen, amide and other nitrogen.

The higher protein content of the nitrate roots is associated with a higher percentage dry weight and a lower content of ‘other’ nitrogen. The significance of this relationship is discussed.

During ammonium culture both asparagine and glutamine accumulate, particularly in the shoot.

Evidence is presented that asparagine is the amide primarily concerned in ammonia storage and also that it is formed during nitrate assimilation.

Knowledge of the absorption and assimilation of ammonium and nitrate ions by plants is of fundamental importance for an understanding of fertilizer practice, and the present investigation, in which detached potato sprouts have been successfully grown in ammonium and nitrate culture solutions, forms part of a study of this problem.
A note on the efficiency of a pyrethrum spray in controlling Ephestia elutella Hb. moths in a granary
Authors: Owen R. W.
Published: February 2008

A stowage in a London granary containing 500 tons of Manitoba wheat was sprayed with 0.8 % w/v pyrethrins in Shell oil P31, in an attempt to control an Ephestia elutella infestation. The mean deposit on the surface of the wheat was 1‐5 mg./sq.cm., of which one‐sixth was due to the settling of mist.

All the moths in the stowage at the time of spraying, estimated at 68,900, were killed or fatally affected within 24 hr., and those which emerged later, estimated at 7500, were killed by the insecticidal film.

The spray was not observed to have any marked effect on the size of the migrating larval population.
Experiments on the use of ethylene dibromide as a fumigant for grain and seed
Authors: Aman J. , Farkas L. , Ben‐Shamai M. H. , Plaut M.
Published: February 2008

The toxicity of ethylene dibromide to Calandra oryzae and Tribolium species was determined in the absence and presence of grain. Its toxicity by oral administration was studied on rats and guinea‐pigs. The quality of bread baked from flour fumigated with ethylene dibromide was found to be unimpaired. The germination capacity of wheat, barley, maize, peas and beans was not adversely affected by fumigation with ethylene dibromide. The results of large‐scale fumigations are reported and the conditions discussed under which ethylene dibromide can be used advantageously as a fumigant for grain and seed stores on a commercial scale. A concentration of 50‐75 g./m.2 was found satisfactory.
The use of toxic polynitro derivatives in pest control III. The stability of dinitro‐o‐cresol in compounded products
Authors: Bennett S. H. , Kearns H. G. H. , Martin H. , Wain R. L.
Published: February 2008

Under certain conditions dinitro‐o‐cresol (D.N.C.) is easily decomposed to reduction products devoid of ovicidal properties to eggs of apple sucker, winter moth and fruit tree red spider.

Because of this, corrosion of containers in which D.N.C. products are stored may be accompanied by a deterioration of the product.

At the concentration normally used in winter washes (0.1%), D.N.C. is equally effective whether present as cresol or as the sodium cresylate against eggs of apple sucker and of winter modi, but against eggs of fruit tree red spider the cresol is more ovicidal than the cresylate.
Studies upon the copper fungicides. IX. Investigations with the exudate from fungus spores
Authors: Wain R. L. , Wilkinson E. H.
Published: February 2008

Determinations have been made of the copper dissolved from pure copper compounds by water, by a standardized solution of the exudate ofNeurospora sitophilaspores, by standard solutions of malic and succinic acids and their sodium salts, and by glycine and mannitol.

The results compared with the known fungicidal performances of the copper compounds show that the amounts of copper yielded to water and to the standardized spore extract or glycine solution provide an indication of fungicidal properties.

Although soluble copper in excess of that dissolved by water can only appear from alkaline Bordeaux deposit by complex ion formation, results show that this is not necessarily the only means by which copper can dissolve from other copper compounds.

In a chemical investigation of the exudate ofN. sitophilaspores, mannitol, succinate and fumarate have been isolated. None of these materials can dissolve an appreciable amount of copper from alkaline Bordeaux deposit. Malate, found by other workers to be a constituent of the exudate of N. sitophila spores cultured on potato dextrose agar, has not been detected in such a solution from spores grown on malt agar. The quantity of mannitol in spore exudate has been shown to depend on the nutrient medium on which the fungus is grown.
The influence of potato variety on the cyst of the potato‐root eelworm, Heterodera rostochiensis Wollenweber
Authors: Ellenby C.
Published: February 2008

Experiments are described with eelworm cysts obtained from the roots of four potato varieties, Doon Star, Arran Banner, Redskin and Kerr's Pink. In a cyst‐type: excretion‐type hatching trial carried out in autumn, each group of cysts was stimulated by root excretions derived from the four types of plants. There were significant differences in the response to the root excretions from the different sources, and in the number of larvae emerging from the different cyst types, the number being highest for Arran Banner and practically nil for Doon Star cysts; but there was no correlation between cyst type and excretion type.

In experiments the following spring with the same cysts, emergence was heavy for all cyst types; but it began considerably later for Doon Star than for the other cyst types. The lack of emergence from Doon Star cysts in the previous autumn was, therefore, not due to the death of the contents of these cysts.

Fewer larvae emerged from Doon Star cysts than from either Arran Banner or Redskin (experiments with Kerr's Pink were discontinued). Doon Star cysts were smaller; however, comparing values for larval emergence and cyst volume for the different cyst types by the method of covariance, the larval emergence was found to be significantly lower for Doon Star cysts than for cysts of the other types, even after adjustment for cyst size.

The number of eggs in each cyst was determined. Analysis by the method of covariance showed that, after adjustment for cyst size, there were significantly fewer eggs in Doon Star cysts than in cysts of the other types.

A similar analysis was carried out of the relationship of larval emergence and egg number. The regression coefficients show that for each cyst type a constant proportion of eggs hatched; but the proportion is smaller in Doon Star cysts, for, after adjustment foreggnumber, the value for larval emergence is still significantly lower. Fewer larvae therefore emerged from Doon Star cysts partly because the cysts are smaller, partly because, for the same volume, they contain fewer eggs, and partly because a smaller proportion of these eggs hatched during the course of the experiments.

The results are discussed in relation to a recent paper by Gemmell (1943). While the differences may be due to resistance on the part of the host plant, as claimed by this worker, there are other possibilities; it is considered that these should be investigated before the hypothesis of ‘resistance’ is accepted. In particular, it is suggested that the differences in cyst size and egg number may be due to differences in the seasonal behaviour of the different potato varieties; differences in the hatching response of the cysts may then be due to the fact that the eelworm cyst responds to root excretions as a unit and that egg concentration is a factor affecting the nature of the unit.
OBSERVATIONS ON THE PATHOGENICITY OF CALONECTRIA RIGIDIUSCULA (BERK. & BR.) SACC. ON THEOBROMA CACAO L
Authors: CROWDY S. H.
Published: February 2008

Calonectria rigidiuscula has been found associated with an acute and a chronic form of dieback of cacao. It can also infect cankers caused primarily by Phytophthora palmivora, and the lesions following attack by the capsids Sahlbergella singidaris and Distantiella theobroma. The association with the capsid lesions is of great economic importance since it appears that capsids alone are capable of killing only green shoots, and that the severe damage caused to woody shoots follows C. rigidiuscula infection of the capsid lesions. Acute dieback occurs only in certain districts after exceptional drought and may be considered primarily the result of environmental conditions. The main importance of chronic dieback is that it prevents the recovery of cacao which has been seriously weakened from other causes. C. rigidiuscula infection retards the healing of P. palmivora cankers and also produces a lesion in the xylem tissue which may be extensive.

C. rigidiuscula has been established in wounded cacao stems of all ages without difficulty. The spread of the fungus is slow, but is more rapid in the xylem than in the cortical tissues. Spread is greatest in the unlignified tissues.
NOTES ON A VIRUS DISEASE OF CACAO
Authors: BAKER R. E. D. , DALE W T.
Published: February 2008

A virus disease of cacao, discovered in Trinidad towards the end of 1943, is apparently confined to the north‐western corner of the is land and does not occur in the main cacaogrowing areas of eastern, central and southern Trinidad; nor has it been found in Venezuela, Tobago or the Windward Islands of Grenada, St Vincent, St Lucia and Dominica. The symptoms resemble those of West African swollen shoot disease, consisting of vein‐clearing or mosaic of the leaves and red‐mottle of the leaves and pods. No swellings are formed, but recent observations indicate that the disease may cause both dieback and reduction in yield. There are two strains closely resembling each other. The spread of the disease under field conditions has been demonstrated, and although the rate of spread has varied somewhat, a mean increase of 41 % over the original number of infected trees has been found over a 10‐month period. As with swollen shoot disease, existing diseased areas have increased in size and new outbreaks at short distances have occurred. Both strains were readily transmitted by budding, the incubation period varying from 34 to 136 days, with a mean around 90 days, but no insect vectors have been found. There is at present little reason to believe that any varieties of cacao are immune to the disease or are even symptomless carriers. The question of eradicating this virus, while its distribution remains limited, should be seriously considered.