bluuebunny/crossref_metadata_2025 huggingface dataset:
SKIN SPOT (OOSPORA PUSTULANS OWEN & WAKEF.) OF THE POTATO, AND ITS CONTROL BY TUBER DISINFECTION
Authors: GREEVES T. N. , MUSKETT A. E.
Published: February 2008

Summary

Experiments carried out during 1933‐8 with the object of investigating the control of skin spot (Oospora pustulans Owen & Wakef.) by seed‐tuber disinfection are described.

Compounds of mercury were effective when used in solution as steeps. Formalin and a proprietary dusting compound proved to be non‐effective. Proprietary organo‐mercury compounds gave the most promising results, and were satisfactory when used as “instantaneous” dips (0·5‐1·0 min.); mercuric chloride solution was efficient but the 90 min. dipping period employed made the method too tedious.

The time at which the treatment is carried out is of great importance in determining the measure of control obtained. Disinfection of the seed at the time of digging was far more effective than immediately before planting. If too long an interval (more than 8 weeks) is allowed to elapse between digging and disinfection, the value of the treatment is substantially reduced.

A study of the time of digging the crop upon the incidence of the disease, made during one year only, indicated that for that year early digging did not reduce the amount of the disease which developed during subsequent storage. Disinfection carried out at each of the five diggings gave satisfactory control in each case.

The method of treatment recommended is the same as that previously suggested for the control of common scab (Actinomyces scabies (Thaxt.) Güss.) and blight (Phytophthora infestans (Mont.) de Bary). Some evidence was obtained of its also being effective against storage diseases. It would, therefore, appear that disinfection of seed tubers at the time of digging may prove effective against a group of tuber diseases many of which are transmissible to the resultant crop.
INVESTIGATIONS UPON THE PEA STRAIN OF HETERODERA SCHACHTII SCHMIDT AND ITS RÔLE IN THE CAUSATION OF PEA SICKNESS
Authors: POWELL A. K.
Published: February 2008

Summary

A series of experiments was carried out upon the etiology of pea sickness, a disease which is invariably associated with Heterodera schachtii.

In addition to this eelworm, a fungus, Aphanomyces euteiches, was found to be concerned in the production of the diseased condition of the plants in the soil studied.

Both Heterodera schachtii and Aphanomyces euteiches can singly produce a pathological condition of the host in the absence of any other pathogenic factor.

The effects upon the plants of attack by Heterodera schachtii alone indicate that it is the primary cause of pea sickness.
FURTHER OBSERVATIONS ON ANGUILLULINA DIPSACI IN RHUBARB
Authors: JOHNSON L. R.
Published: February 2008

Summary

Continued field observations on disease in rhubarb accompanied by infection by Anguillulina dipsaci are recorded. The symptoms, both in the foliage and in the root stock, are similar to those described for bacterial crown rot by Millard.

In infection experiments using the rhubarb strain of A. dipsaci symptoms of disease similar to those found in the field were reproduced in rhubarb seedlings and setts. The course of eelworm infection in the young leaves and in the crown in these experiments is recorded.

Host transference experiments have shown that the rhubarb strain of A. dipsaci is not rigidly restricted in its feeding habits for it is capable of producing persistent infection in oats, pea and chickweed. It is also capable of producing only temporary infection in cabbage and mangold. Infection is also recorded in Rumex spp. but insufficient evidence is available as to its persistence on these hosts.

Incidence of A. dipsaci is recorded in rhubarb from Scotland and southern England in addition to Yorkshire.
THE GROWTH AND ANATOMICAL STRUCTURE OF THE CARROT (DAVCUS CAROTA) AS AFFECTED BY BORON DEFICIENCY
Authors: Warington Katherine
Published: February 2008

carrots grown in nutrient solution without the addition of boron were unable to complete their normal development and exhibited both external and internal deficiency symptoms:

I pnrt boric acid in 2 million was sutticient to maintain healthy growth when the culture solutions were renewed regularly.

The effect of a lack of boron at late stages of growth was determined by transferring plants to a boron‐free solution after they had received an initial supply.

The chief deficiency symptom were:

E x t d. The leaves curled back, pointed downwards and often turned red or yellow. The laminae of the youngest leaves were much reduced and the growing apex of the shoot died. The flowering stage was not reached. A small tap root was formed but the laterals were abnormal m appearance, being short and thickened in places. When the boron de‐ ficiency only arose in the later stages of development, certain additional symptoms appeared, viz. the flowering heads bent over and died, those of the side shoots succumbing first. In some cases small wart‐like excrescences arose on the outside of the tap root.

Intmrol. Although no marked degeneration within the tap root was evident to thenaked eye, microscopic investigation showed that most of the tissues of the shoot and root were af ected by a lack of boron. Breakdown began in the region of the growing point of the shoot, patches of irregular and blackened tissue appearing in the young leaves and in the vascular tissue close behind the tip, though the meristematic apex itself was not necessarily h t involved. Later, similar patches were found in the cortex and occasionally also in the pith. Hypertrophy usually preceded or accompanied the formation of these lesions. All cmponents of the vascular bundles were affected, blocking occurring in the xylem and phloem, and hypertrophy and breakdown in the thin‐walled tissues. The formation of the wart‐like growth on the tap roots and the swellings on the laterals was explained by the fact that in the absence of boron, repeated branching and radial extension of lateral roots contin, when elongation and emergence were prevented through death of the apices.

Recovery took place in both shoot and root when boron was supplied, even after prolonged growth in its absence. Traces of the earlier deficiency period could be detected in the anatomical structure of the older parts of the plants although the external appearance was quite normal.
THE IDENTIFICATION OF CERTAIN VIRUSES FOUND INFECTING LEGUMINOUS PLANTS IN GREAT BRITAIN
Authors: Ainsworth G. C.
Published: February 2008

In a survey of the virus diseases of leguminous plants in Great Britain, it was not found possible to relate the virus of lettuce mosaic, which Ainsworth & Ogilvie (1939) found able to infect both culinary and sweet peas, to any other virus but, in the course of examining about seventy‐five samples of material, a number of different viruses were identified. These, with possibly one exception, appear to have been described in other parts of the world, but the following notes include several new records for this country.
FACTORS INDUCING MINERAL‐DEFICIENCY SYMPTOMS ON THE POTATO PLANT
Authors: Cowie G. A.
Published: February 2008

The data are based upon observations derived chiefly from twenty‐four replicated manurial trials made on the potato crop in 1937 and from twenty‐five further trials of a different design in 1938. They deal with the manurial and other factors that induce deficiency symptoms relating to potash, phosphates and calcium respectively on the potato plant. Leaf scorch, and the other potash‐deficiency symptoms on the aerial part of the plant are normally induced by NP and not by nitrogen treatment. The presence of leaf scorch on the nitrogen plots in a number of trials has been satisfactorily correlated with a high level of available phosphates in the soil, as indicated both by a chemical test for phosphate solubility and the degrees of response to phosphate applications. An increase in the level of nitrogen in the NP treatment results in the intensification of potash‐deficiency symptoms. A certain interaction between nitrogen and phosphates is shown to be the primary factor in inducing potash‐deficiency symptoms on the part of the plant above ground. The blackening of cooked tubers which has hitherto been assumed to indicate potash deficiency has been found to result from a combination of high nitrogen with low potash in the soil. Phosphate deficiency is induced by nitrogen and NK treatments, but more strongly by the latter. Phosphate‐deficiency symptoms and not potash‐deficiency ones become evident on the nitrogen plants under conditions of low phosphates and low potash in the soil. Calciumdeficiency symptoms appeared at three centres on poor sandy soils with pH values ranging between 45 and 5. Observations failed to detect signs of magnesia deficiency on the plants at any centre and in either season. The results of this observation were borne out by the absence of significant yield responses to magnesia with one exception in each season.
SOME NOTES ON THE BIOLOGY OF THE CLICK BEETLES AGRIOTES OBSCURUS L. AND A. SPUTATOR L.
Authors: Gough H. C. , Evans A. C.
Published: February 2008

Wire‐worms rarely occur in permanent arable land in sufficient numbers to cause serious damage to crops. Various workers (e.g. Roebuck, 1924; Hawkins, 1936; Miles & Cohen, 1941) have noted the reduction in numbers of wireworms in successive years on ploughed‐out grassland. At Rothamsted reductions of 62 % in one year and 85 % in two years were recorded on plots on Highfield. This reduction is certainly due in part to the exposure of wireworms to their natural enemies and to the direct effect of disturbance by implements of cultivation. It has also frequently been suggested that the beetles prefer to oviposit on grassland or clover leys and to a lesser extent on cereal crops (Bryson, 1930; Rawlins, 1934; Balachowsky & Mesnil, 1935; Miles & Cohen, 1938). A laboratory experiment to test this point was accordingly carried out in June 1940.
The nutrition of the carrot
Authors: Woodman R. M.
Published: February 2008

In sand‐culture experiments with carrots, it was shown that a moderate quantity only of nitrogen was necessary for optimum growth compared with, for example, the turnip root. A moderate amount of (available) phosphorus was also sufficient for this purpose, as with the turnip, but contrary to experience with lettuce roots and tops. The greatest concentration of potassium applied, however, was probably the best for root development. Deficiency of phosphorus caused bronzing of the leaves, and absence of potassium, serious scorch; absence of boron resulted in a small, immature plant. Initial field trials on an old river gravel during experiments throughout the last 7 years indicated that dung gave no advantage over artificials, that artificials were possibly not needed on dunged land or land in good heart, and that land out of good heart, undunged and unfertilized throughout the 7 years, responded well to artificials, particularly phosphate and potash. The incidence of carrot fly, according to preliminary experiments, seemed to depend greatly on the nutrition of the carrots.
Effect of seed treatment on emergence of peas
Authors: Bayus G. T. S. , Deshpande R. S. , Storey I. F.
Published: February 2008

Experiments carried out during the carry months of four consecutive years lead to the following conclusions: (1) high soil moisture accentuates the pre‐emergence damping‐off of peas; (2) a useful measure of disease control is obtained by dressing the seed with red cuprous oxide or an organic mercurial preparation. The addition of a sticker is undesirable with both fungicides; (3) whereas cuprous oxide has, more often than not, exceeded the mercurial preparation in giving increased emergence, the latter has the advantage of reducing the amount of seed‐borne (Ascochyta) disease. In addition, the danger of an overdose is less with the mercurial preparation than with cuprous oxide; (4) the presence of a growth‐promoting substance in a mercurial preparation gave no increased beneficial effect, as regards emergence, vigour of growth, or reduced liability to phytoddal damage.
A survey of potato aphides in the South‐Western Agricultural Advisory Province
Authors: Staniland L. N.
Published: February 2008

The results of a survey of aphis populations on potatoes in Devon and Cornwall; with special reference to Myzus persicae Sulz., during the years 1937‐41 are given. One or more counts were made by the standard method at 107 centres to determine population index figures. The results are summarized in the form of a map. The highest index figure obtained during the 5 years was 609, and only on six other occasions was the figure of 100 exceeded; of these centres only one was situated in the area considered to be especially favourable to seed production, and this centre was a market garden. The distribution of the various species of potato aphides is discussed, together with their fluctuations from year to year; special reference is made to M. persicae and M. ornatus. Observations on the parasitism of M. persicae are described. The relationship of the proximity of winter hosts, altitude and of meteorological conditions, to the populations of M. persicae is discussed. The conditions for the production of seed potatoes in Devon and Cornwall are summarized. An account is given of those areas in Devon and Cornwall deemed suitable for seed production. A short account of the formation of a ‘Seed Potato Growers' Association’ in Devon and Cornwall has been added.
The mode of action of pyrethnxm on the cockroach, Periplaneta americana L
Authors: Roy D. N. , Ghosh S. M. , Chopra R. N.
Published: February 2008

Pyrethrin, the active principle of pyrethrum powder, is insoluble in water but is soluble in, the body fluid of the cockroach. It has a selective action on nerve ganglia, and the destruction of their cells is responsible for the death of the insect. Whereas pyrethrum, when used ‐either in the powdered form or in a fluid state mixed with kerosene and introduced directly into the body cavity reaches the ganglion with the circulation, its mode of action when it acts through the spiracles is different. Kerosene‐pyrethrum mixture when introduced into the tracheal trunks through the spiracles is quickly diffused into the haemocoele. When the dry powder is inserted into the trachea, its mode of action is analogous to a fluid preparation. As the conversion of pyrethrum from a dry into a fluid state is alone possible in the interior of the trachea, the natural conclusion is that a fluid analogous to the body fluid is present in the same situation. As soon as the pyrethrin is dissolved, it is quickly diffused into the haemocoele and thus reaches the nearest ganglion.
A comparative account of the life cycles of Lumbricillus lineatus Mull. and Enchytraeus albidus Henle in relation to temperature
Authors: Reynoldson T. B.
Published: February 2008

Compared with Lumbricillus lineatus the cocoons of Enchytraeus albidus are smaller and contain fewer eggs whilst the egg production per worm is higher and sterility among the eggs lower. The fecundity of E. albidus is greater over a temperature range 1–25d̀ and is not so adversely affected at the higher or lower temperatures as L. lineatus. Incubation in E. albidus is longer than in L. lineatus but the time required for maturation is much shorter, the periods depending upon the temperature. There is a similar relation to temperature as in the case of fecundity, with E. albidus again more tolerant to heat and cold. There is no relation between size and temperature but unlike L. lineatus, growth occurs after maturation in E. albidus and its cocoons (after the first) and their egg content are larger. There is no apparent relation between the setae length and temperature. The temperature relations favour a more rapid increase of E. albidus in the bacteria beds than of L. lineatus but they are well suited to the distribution of the species under natural conditions, E. albidus favouring a terrestrial habitat whereas L. lineatus exists in moister places. Further, they show specific physiological differences distinguishing the two species of worms.
The statistical treatment of toxicological data relating to ore than one dosage factor
Authors: Finney Br D. J.
Published: February 2008

Experiments on the biological measurement of toxicities, and others requiring the use of the probit transformation in the statistical analysis, have in die past been largely of a unifactorial nature. In order to reach a fuller understanding of the action of insecticides and other poisons it is necessary that experiments be performed in‐which two or more factors relating to the dosage are subjected to variation. Bliss has recently described methods for the analysis of two‐factor experiments, but his technique is not a direct extension of the simple case for the fitting of a probit regression line, nor will it generalize easily when more factors are involved.

In the present paper it is shown that probit regression planes and hyper‐planes can be fitted in a way exactly analogous to that used for the regression line. Tests of heterogeneity and of parallelism, and standard errors of parameters are readily derived. The notion of relative potency of two poisons does not extend so easily, and it is suggested that the mean probit difference should be used in its stead as a measure of their relative effectiveness. As in the unifactorial analysis, the routine of fitting the. regression equations may be repeated until satisfactory accuracy in the estimation of the parameters is attained, but usually one, or at the most two, cycles of the process gives values sufficiently near to the maximum likelihood solution for practical purposes.

A more general class of equations is introduced for use when the probit mortality is linearly related to each dosage factor separately, but the individual effects are not additive. The suggestion made by Bliss (1040) for this case lacks symmetry and does not completely fulfil the linearity conditions, but the present proposal avoids these defects and permits the making of tests for the significance of the im‐proval in fit effected by the additional parameters.

The arithmetical procedure for the fitting of a probit plane is described in detail for data on the toxicity to Tribolium castameion of a pyrethrin oil spray at various levels of concentration and deposit weight. Two methods of applying the poison were compared in this experiment, and the two series of results were excellently fitted by parallel probit planes. Direct spraying gave slightly, but not significantly, higher kills than the film method of application, and under the particular conditions obtaining, increasing the concentration of pyrethrin in the spray was a far more effective means of increasing kill than was a proportionate increase in the total amount of spray available to the insects. Numerical examples used by Bliss are also discussed in relation to die methods of fitting and forms of equation given in this paper.
Observations on the biology of the potato‐root eelworm, Heterodera schachtii Schmidt
Authors: Boyd A. E. W.
Published: February 2008

Results are presented of experiments on the effect of low temperature and of soil type upon the potato‐root eelworm, Heterodera schachtii.

In some experiments exposure of cysts, to low temperatures had a definite lethal effect, but in others the cysts were unharmed. The reason for this variation was not apparent. Exposure of the larvae of die nematode to even a relatively slight degree of frost resulted in the death of the larvae, provided mat die surrounding medium was completely frozen. In this respect the larvae appear to differ markedly from those of the beet strain of H. schachtii. That the larvae had actually been killed was shown by the fact that they produced no cysts on the roots of potato plants and also by their almost immediate absorption of iodine.

It was confirmed that H. schachtii cysts produced on the roots of potato plants grown in a heavy medium are smaller in size and fewer in number than those formed on the roots of plants grown in a light medium. The heavy medium used was pure clay, the light one pure sand, while equal numbers of eelworm larvae served in each case as inoculum. The difference in cyst size was significant, and fewer larvae emerged from the cysts formed in clay than from those produced in sand.
Stimulation of larval emergence in Heterodera schachtii Schmidt, by certain concentrations of silver compounds
Authors: Boyd A. E. W.
Published: February 2008

Certain dilute solutions of organic silver compounds, e.g. 0.001% silver proteinate, acting for a short time on cysts of the potato strain of Heterodera schachtii, cause increased numbers of larvae to emerge from the cysts when the latter are transferred to potato root excretion. More prolonged exposure of cysts to these solutions tends to result in a toxic effect which is also produced by more concentrated solutions. It is concluded that many more eggs in H. schachtii cysts are mature and capable of hatching than can be accounted for by ordinary larval liberation brought about by means of root excretion alone. Increasing periods of pre‐treatment of cysts in tap water tend to produce increases in larval emergence, although this stimulation is probably of a different type from that given by silver compounds.
Preliminary experiments on the use of oil‐soluble copper compounds as fungicides
Authors: Hickman C. J. , Marsh R. W. , Wilkinson E. H.
Published: February 2008

Tests were made of the solubility of a number of copper compounds in mineral and vegetable oils. Phytocidal tests on onion foliage showed that turpentine, pine oil and white spirit were damaging whereas cottonseed oil and white oil were innocuous. Copper salts in white oil, white spirit, turpentine or pine oil showed a higher fungicidal value than in cottonseed oil. In laboratory tests, a solution of copper 3:5‐di‐isopropyl salicylate was more fungicidal than Bordeaux mixture of the same copper concentration. In a small field trial, copper 3:5‐di‐iospropyl salicylate dissolved in white oil to give a concentration of 0.01% Cu was atomized three times at monthly intervals on to onion foliage without damage. The same material at 0.1% Cu in white oil was phytocidal. No control of onion downy mildew (Peronospora schleideniana) was obtained in this trial. The method of atomization was convenient and practicable for small‐scale operation. It gave perfect wetting of the foliage and was very economical of material.
Experiments on the rate of spread of narcissus stripe in the field
Authors: Hawker Lilian E.
Published: February 2008

Striped and healthy bulbs of several varieties of narcissus were interplanted: the amount of spread of the disease was greatest when the bulbs were planted close together. The results obtained are in accordance with McWhorter's view that transmission takes place through injured roots.
Notes on Thysanoptera found on flax (Linum usitatissimum L.) in the British Isles
Authors: Morison G. D.
Published: February 2008

The following eighteen species of Thysanoptera Terebrantia have been found on flax in the British Isles: Melanthrips fuscus (Sulzer), Aeolothrips fasciatus (L.), Anaphothrips obscurus (Müler), Aptinothrips rufus (Gmelin), Chirothrips manicatus Hal., Limothrips cerealium Hal., L. denticornis Hal., Stenothrips graminum Uzel, Taeniothrips atratus (Hal.), T. vulgatissimus (Hal.), Thrips angusticeps Uzel, T. discolor Hal., T. flavus Schrank, T. fuscipennis Hal., T. major Uzel, T. minutissimus L., T. physapus L., T. tabaci Lindeman. Each species is described briefly with notes on habits of adults and larvae, place of pupation, number of generations in the year, hibernation, time of occurrence on plants, plants and objects on which found, host plants of larvae and adults, importance to flax, record of locality and collector on flax, distribution, including altitudes, in the British Isles. More species occur in the south than in the north of Great Britain, and species common to both regions usually occur in greater numbers in the south. The insects breed on certain species of crop plants, weeds or trees of arable land. No damage of economic importance to flax by Thysanoptera has been proven in the British Isles, and the flax thrips, Thrips lini Ladureau, has not been found. Taeniothrips vulgatissimus (Hal.) may breed on flax and its adults, and those of T. atratus (Hal.) may cause superficial damage to petals of flowers. Thrips angusticeps Uzel and T. tabaci Lindeman will probably breed on flax.
Biological methods of determining the insecticidal values of pyrethrum preparations (particularly extracts in heavy oil)*
Authors: Tattersfield F. , Potter C.
Published: February 2008

Pyrethrum extracts in non‐volatile oil carriers are effective insecticides in the field because they act as a direct spray killing the insect and also form a toxic film over which the insect crawls: it is necessary to study both these effects for a complete laboratory assessment of toxicity. Suitable laboratory techniques and methods for the assessment of results are described together with an account of experiments on the effect of various factors on the insecticidal efficiency of pyrethrum‐in‐oil preparations, both as direct sprays and as toxic films.

The programme necessitated some duplication of work, but discussions that took place from time to time between the workers concerned at the two laboratories during the progress of the investigations reduced this to a minimum.
The nutrition of the radish
Authors: Woodman R. M.
Published: February 2008

Sand‐culture experiments with the radish demonstrated that the optimum concentrations of nitrogen for root development were the highest employed, 32.96 and 65.92 p.p.m. Deficiency of nitrogen led to poor growth and to a characteristic outlining of the cotyledons in red, with red petioles. As with the carrot and turnip, a low concentration of available phosphorus, here 2.05‐4.09 p.p.m., gave the best root growth; and a marketable radish was obtained with so little as 0.10 p.p.m., suggesting that the relatively large radish seed contains a considerable quantity of phosphorus. The highest concentration of potassium used, 22.44 p.p.m., yielded the largest roots, and a diminution in this amount led to loss of yield and eventually to serious scorch of the foliage. There is possibly some boron in the radish seed; for though absence of this from an otherwise satisfactory solution resulted in diminished yields, the foliage was normal in appearance, and the radish of eatable size; the radishes apparently lacked ability to swell.
Notes on basal rot of narcissus
Authors: Hawker Lilian E.
Published: February 2008

Control of basal rot of narcissus following hot‐water treatment against eelworm was equally good when 0.5% formalin was included in the bath or was used as a cold or warm steep immediately afterwards. When the formalin steep was delayed control was less good. All methods of applying formalin in connexion with hot‐water treatments used in these experiments were equally harmless to growth and flowering of the bulbs.
Factors influencing infection of the tomato by Verticillium albo‐atrum
Authors: Roberts F. M.
Published: February 2008

Infection of tomato plants by Verticillium albo‐atrum was encouraged by application of nitrogenous manures. Application of phosphate had no significant effect on the progress of the disease, but a deficiency of potash tended to encourage it. Steam‐sterilized soil inoculated with Verticillium immediately after treatment produced a very high total of infected plants. When inoculation of the steamed soil by Verticillium was delayed for 17 days or longer after steaming, the steamed soil was no more favourable for development of the disease than untreated soil. Spread of Verticillium from the roots of an infected plant to those of neighbouring healthy plants was hastened by killing the infected plant.
The appearance and spread of mosaic infection in the tomato crop and the relation to seed transmission of the virus
Authors: Selman Ireson W.
Published: February 2008

Appearance and spread of infection with mosaic‐inducing viruses were studied for three seasons in tomato crops under glass. Comparison was made between the reactions of plants raised from virus‐free seed and those of plants raised from virus‐infected seed, on plots distributed at random in a house in which no precautions against entry and spread of virus were taken. Freedom from mosaic infection was maintained longest in plants raised from virus‐free seed. An experiment was carried out after steam sterilization of the soil and under exceptionally favourable weather conditions. Appearance of mosaic symptoms occurred later in the life of the plants in this season and plants raised from virus‐free seed did not react differently from other plants.

The location of plants first showing mosaic symptoms was related to the depth and texture of soil beneath those plants.

Tests were made of the apparent virus content of infected tomato seed during germination and differences were found in the persistence of virus during germination in seeds of differing origin.

Apparent, ‘delayed’ seed transmission of mosaic‐inducing viruses occurs in the tomato crop, but as yet, this condition can only be interpreted in terms of differences in the resistance of plants raised from seed of differing origin to the multiplication and systemic spread of those viruses. The use of virus‐free seed taken from well‐nourished vigorous plants is essential to the production of a virus‐free tomato crop under commercial conditions.
Studies upon the copper fungicides
Authors: Wain R. L. , Wilkinson E. H.
Published: February 2008

The soluble copper in freshly prepared 4:4:50 Bordeaux mixture was of the order of 7 p.p.m. but on standing in absence of air this fell to 0.7 p.p.m. after 10 days. The dried deposit on glass plates yielded about 0.5 p.p.m. of copper to water. With increasing alkalinity, the soluble copper in freshly prepared Burgundy mixtures decreased to a minimum of about 3 p.p.m. and then rose again. This effect was not observed using dried deposits which yielded consistently less copper to water. The amounts of copper dissolved by water from dried 4:4:50 Bordeaux deposit on runner bean leaves were slightly greater than from the same deposit on glass plates. The results cannot be taken as positive evidence that leaf excretions are involved in the liberation of soluble copper since detached leaves were used and the influence of bacteria could not be eliminated.

Suspensions of Neurospora sitophila spores and the nitrates therefrom dissolved copper from dried 4:4:50 Bordeaux deposit in excess of the amount dissolved by water, though these quantities, as well as the amounts of soluble solids in spore filtrates, were appreciably less than were found by other workers in a similar investigation. Steam sterilization of spore filtrates had little effect on their capacity to dissolve copper from dried 4:4:50 Bordeaux. The temperature at which spores were suspended in water was a factor, though the substances capable of dissolving copper were rapidly yielded to water. The nutrient agar on which the fungus was grown influenced the amount of soluble solids in the spore filtrate and the capacity of these nitrates to dissolve copper from dried Bordeaux deposit.

Study of the solvent properties of solutions of pure chemical substances of many types showed that copper could only dissolve from dried 4:4:50 Bordeaux deposit by a mechanism involving complex formation. Active substances included amino‐, hydroxy‐, and certain dicarboxylic acids and their salts, all possible constituents of spore exudate. The results obtained with carbohydrates indicated that such substances are not involved in the liberation of soluble copper from this fungicide.

A hypothesis on the mechanism of the fungicidal action of copper, based on the results obtained, is presented. This assumes that copper dissolves from the deposit under the influence of excretions from the fungus spore and that the cupri‐complexes produced are the means by which soluble copper is transported to the spore wall. Dissociation of these complexes then make it possible for the active toxicant to be removed by the spore, thus enabling any reversible reactions involved to continue.
Physiological cotton wilt in the Sudan Gezira
Authors: Boughey A. S.
Published: February 2008

Cotton wilt of physiological origin appears to have been present in the Gezira area of the Anglo‐Egyptian Sudan since 1924 if not previously. The present investigations showed that between mid‐October and mid‐December three factors occur which cause water stress in the crop. At some time during this period there is marked reduction in the size of the absorbing system of the plant, correlated with maximum boll development. Greatly increased day temperatures and higher evaporation prevail, while during the whole period available water in the soil declines. The hypothesis is put forward that when all three factors occur at the same time at their maximum intensity, permanent wilting and death of the plants result; at lesser intensities, wilting is followed by recovery, but with reduction of yield. Experiments are described, the results of which appear to confirm this view. In the author's opinion a return to the earlier sowing date formerly favoured locally would lead to considerably increased losses.
The nutrition of vegetables in sand
Authors: Woodman R. M.
Published: February 2008

The yield data available from the author's series of investigations on vegetable nutrition in sand have been plotted against the concentrations of the elements concerned (nitrogen, phosphorus, and potassium), and the curves so obtained have been discussed. Within the ranges of concentrations employed, it is observed that too much available nitrogen or, especially, available phosphorus, causes depressions in yields with the tops and/or roots of certain vegetables, turnip roots being particularly susceptible to too much available phosphorus; no case of over‐employment of available potassium, however, is noted. The turnip is recommended as a type plant for indicating the state of soil fertility as regards available (nitric) nitrogen.
The ‘phloem necrosis' virus disease of tea in Ceylon
Authors: Bond T. E. T.
Published: February 2008

A virus disease of tea in the up‐country districts of Ceylon is described which is known as ‘phloem necrosis’ from the characteristic internal symptoms. External symptoms including leaf curl and zigzag and dwarfing of the shoots are of less constant occurrence and appear to be much influenced by climatic and growth conditions generally. Severely affected bushes are rendered entirely unproductive. The disease is shown to be transmissible by grafting to certain types of tea, nine clones of various origin having been infected so far. In others, of the type commercially favoured for replanting, no symptoms are produced. These have proved to be symptomless ‘carriers’ capable of transmitting the disease to further susceptible scions. The theoretical aspects of the results are discussed, considerations of control and the practical significance of the ‘carrying’ capacity being left for a further paper.
The characteristics of certain varieties of potato with special reference to their suitability for drying
Authors: Burton W. G.
Published: February 2008

There is considerable varietal variation in the characteristics of the potato. The characteristics of any one variety of potato may be very greatly modified by environmental conditions. Rainfall and percentage dry matter may be inversely correlated, as may rainfall and yield in localities with a medium or high precipitation. There is an apparent correlation between time of maturity, percentage dry matter, and texture when cooked, late varieties having a higher percentage dry matter and a more floury texture than early varieties. It is a fundamental requirement of potatoes for drying purposes that they should not discolour on cooking. In addition the texture of the cooked potato should be suitable for the method of drying employed, and for the type of reconstituted product desired, and the percentage dry matter should be as high as is compatible with the foregoing conditions.
Serological studies on sugar‐beet yellows virus
Authors: Kleczkowski A. , Watson M. A.
Published: February 2008

Specific antisera have been prepared against the sap expressed from beet plants infected with beet yellows virus.

The antigen is unstable. In the sap it is destroyed by keeping for 2‐3 days at room temperature or by heating for 10 min. at 52d̀C. It is unaffected by pH changes between 5 and 9. In detached leaves at room temperature it remains unchanged for at least 6 days, whereas the ability of aphides to transmit from these leaves fell considerably in 4 days.

The antigen can be reversibly precipitated by ammonium sulphate or sedimented by high‐speed centrifugation. However, all the attempts to isolate it from other sap constituents or concentrate it have failed.

The precipitin reaction is of value for diagnosis, and works successfully with crude sap.
Soil conditions and the take‐all disease of wheat: VIII. Further experiments on the survival of Ophiobolus graminis in infected wheat stubble
Authors: Garrett S. D.
Published: February 2008

Assimilable nitrogen in various forms prolonged the life of Ophiobolus graminis in infected wheat straw, whether added directly to the straw or to the surrounding soil. When the infected straws were buried in washed quartz sand, 0.5 g. nitrogen per 100 g. air‐dry straw was the optimum dressing for longevity of Ophiobolus. Addition of sodium phosphate did not significantly increase longevity.

Nitrogen is considered to prolong the life of Ophiobolus by enabling the mycelium to form new branch hyphae, which can explore unexhausted parts of the substrate; it is suggested that aged mycelium dies from carbohydrate starvation, through exhaustion of the zones of enzymic erosion around the hyphae. This hypothesis is supported by the extended life of the fungus in infected straws that were shaken twice weekly in 3 % dextrose solution.

Ophiobolus was found to survive longer in infected straws buried in a fallow soil than in the same soil under oats, mustard or trefoil; this finding suggests the use of catch crops as competitors with Ophiobolus for soil nitrogen.
The short wet method of seed disinfection
Authors: Muskett A. E.
Published: February 2008

An account is given of the use of the short wet method of seed disinfection for the prevention of Helminthosporium disease of oats. Equally good results were obtained by its use as those given by the dusting method. A soluble organo‐mercury preparation (Ceresan, U. 564) was employed as the disinfectant. Suitable machinery is necessary for carrying out the short wet method of treatment, and two of the machines manufactured for this purpose are described. They are the ‘Primus’, a hand‐operated machine for dealing with small quantities (3/4 cwt. lots) of seed, and the ‘Kontramix’, a power‐driven machine designed for carrying out continuous seed treatment at rates varying from 5 to 16 cwt./hr.
Observations on the biology and physiology of wireworms of the genus Agriotes Esch
Authors: Evans A. C.
Published: February 2008

Detailed studies of the growth of wireworms kept at a constant temperature of 15d̀ C. for 3 years and at natural soil temperatures for 2 years are presented. It is shown that small wireworms grow rapidly and moult frequently, but large wireworms grow slowly or remain constant in weight and moult infrequently. A basic pattern to account for the decreasing frequency of moulting during the life cycle is presented.

The feeding activity and moulting frequency of a population of wireworms has been studied in detail throughout the season. Definite peaks in feeding activity and moulting frequency occur during the season. A suitable method for the analysis of such activity in a population has been found by dividing the population into groups on a basis of the number of annual moults.

It is shown that increase in dry weight is a more valid estimate of growth than increase in fresh weight. The rate of growth of wireworms is strongly influenced by the food on which they feed: some plants (wheat and carrots) permit rapid growth; other plants (grass and clover) permit slower growth; while certain other plants (mustard and potatoes) allow the wireworm to maintain its weight. Wireworms reared on flax actually decrease in dry weight.

In a field experiment it was found that the type of crop grown after breaking up old pasture had a distinct effect on the wireworm damage done to the following cereal crop. Beans had the effect of reducing the population to a level at which a very successful crop was grown. Better yields were obtained after wheat and grass than after the other crops, excepting beans, at similar levels of population.

The cuticle of wireworms is permeable to water, and it is shown that in its relations to soil moisture the wireworm may be regarded as an osmotic system. The pF scale of soil moisture is shown to be of value in expressing the soil‐moisture relations of wireworms. Wireworms feed more actively in moist soil than in dry or wet soil.
The prevention of seed‐borne diseases of flax by seed disinfection II. Comparison of the dusting, short wet and fixation methods of treatment
Authors: Muskett A. E. , Colhoun J.
Published: February 2008

Suitable organo‐mercury preparations applied by the short wet method of seed treatment and organo‐mercury powders, of the type used for treating cereal seeds, fixed to the seed with water by the fixation method of treatment, gave as satisfactory control of seedling blight and better control of stem break and browning than a proprietary dry fungicide containing tetra‐methyl thiuram disulphide (Nomersan) applied at the rate of 12 oz./cwt. of seed.

Treatment of seed heavily infected with Polyspora Lint using an efficient fungicide resulted in highly significant increases in crop and fibre yields, while in the case of seed heavily infected with Colletotrichum Lini similar treatments significantly increased the yield of fibre but not the crop yield. Some treatments significantly increased the crop and fibre yields even when the seed used was only slightly contaminated with P. Lini and C. Lini. The results presented support the suggestion that effective treatment of the seed may produce an increase of fibre not directly attributable to the prevention of seedling blight or stem break and browning but which may be explained by a general beneficial effect due to seed disinfection.

The results obtained suggest that no treatment consistently affected crop establishment in the field.
A two years' survey of the potato aphides in the Northern Agricultural Advisory Province
Authors: Jacob F. H.
Published: February 2008

The role of aphis vectors in the deterioration of potato stocks is well known, and any effort to maintain healthy (virus‐free) stocks of potatoes depends on the degree of their isolation from these vectors. In practice this isolation depends on geographical, climatic, and biological factors; of these the biological factors are fundamental, as it is only from their study that the significant geographical and climatic factors can be determined.

The present work consists of a survey made during 1942 and 1943, in the Northern Agricultural Advisory Province. Special attention is paid to overwintering, and the prevailing weather conditions at the time of the spring migration.
Beet eelworm (Heterodera schachtii Schm.) in East Anglia, 1934‐1943
Authors: Petherbridge F. R. , Jones F. G. W.
Published: February 2008

Observations made on the beet eelworm (Heterodera schachtii Schm.) between 1934 and 1943 are described. This eelworm confines its attacks to crop plants of the families Chenopodiaceae and Cruciferae. Cysts similar to those of the beet eelworm have been recorded on many weeds. Records of beet eelworm on weeds of the above families are probably authentic, but those of other families require confirmation. In the field, the four so‐called strains of Heterodera schachtii (viz. the beet, oat, pea and potato strains) behave as distinct species. Some evidence is given for the possible existence of a cruciferous strain.

Attempts were made to ascertain the distribution of beet eelworm in East Anglia. A general search was conducted throughout the area and special attention paid to beet‐sugar factories, beet‐loading sites, sewage farms, and to certain important beet‐growing areas located in the Isle of Ely and neighbouring counties. Throughout the search, diagnosis was based on the finding of lemon‐shaped cysts on the roots of sugar beet, red beet or mangolds. Details of our present knowledge of the distribution of beet eelworm are given. It appears to have been present in Britain for a considerable time but is not yet widely disseminated.

The spread of beet eelworm is considered in detail, and it is concluded that the establishment of the beet‐sugar industry has led to a considerable increase in the rate of spread.

Measures for the control of beet eelworm are described. In the early days of the industry, beet was grown without regard to rotation, thus providing conditions similar to those existing in Germany before 1870 when 'beet‐sickness was becoming a serious problem. The first control measure was the introduction of a clause into contracts forbidding the growing of beet after beet or mangolds. More effective measures, which were adopted in 1939, are described. In 1943, the Sugar‐Beet Eelworm Order was issued enforcing these measures over a wide area and extending them to cover all susceptible crops.

Effective control measures may result in a reduced rate of spread of the beet eelworm but cannot eliminate it.
Gliotoxin, a fungistatic metabolic product of Trichoderma viride
Authors: Brian P. W. , Hemming H. G.
Published: February 2008

Gliotoxin is shown to be a metabolic product of Trichoderma viride, and a semi‐continuous apparatus for its production is described. Ammonia nitrogen is preferable to nitrate nitrogen, but a wide range of carbon sources, and organic or inorganic sulphur sources, are suitable for gliotoxin production. No organic supplements to a glucose‐mineral medium have been found to affect gliotoxin production beneficially.

Data are presented showing gliotoxin to be moderately toxic to a wide range of bacteria, actinomycetes and fungi. T. viride itself is resistant to its toxic effects. It shows fungicidal activity when applied as a dust to cereal seeds bearing various seed‐borne diseases, but is inferior to organomercury compounds for this purpose. Its value as a fungicide for control of plant or animal infections is reduced by the instability of aqueous solutions, except at low pH.
The use of abrasives in the transmission of plant viruses
Authors: Kalmus H.
Published: February 2008

The effect of different abrasives on the transmissibility of several plant viruses was tested. Celite and animal charcoal were as effective as carborundum in increasing the number of lesions produced by a given inoculum: 400‐mesh carborundum was the most effective among the different sizes which were tested; this gave a result equivalent to increasing the virus content a hundred times. Some preparations of carborundum and charcoal reduced infectivity.

Uninjured plants resisted infectivity when virus solutions were sprayed over them. Leaves previously nibbed without abrasives developed only few lesions whereas leaves rubbed with abrasives developed large numbers. Three hours after rubbing with abrasives leaves had regained their resistance to sprayed virus solutions.

The effects of rubbing leaves with abrasives are described and their significance discussed.
Control of the potato‐root eelworm, Heterodera rostochiensis Wollenweber, by allyl isothiocyanate, the mustard oil of Brassica nigra L
Authors: C. Ellenby, B.Sc., Ph.D.
Published: February 2008

Previous work showed that, in the presence of root excretioci of certain crucifen, larvae of the potato‐root eelworm do not emerge from the cysts when stimulated by potato‐root excretions; a similar lack of response is also shown in the presence of dilute solutions of allyl isothiocyanate, the mustard oil of black mustard. The present paper describes a small‐scale field trial in which this mustard oil is applied with peat to the drills at the time of planting. An increase in yield of about 100% resulted from a dressing of the oil equivalent to o.1 cwt/acre.