bluuebunny/crossref_metadata_2025_split huggingface dataset:
STUDIES OF THE CLOVE TREE
Authors: SHEFFIELD F. M. L. 
Published: February 2008

A detailed study was made of the histology of apparently healthy clove trees and of trees expected to die from sudden death disease, in an attempt to find either a diagnostic character of the disease or some indication of a possible pathogen.The apparently healthy clove tree differs from a typical dicotyledon in a number of ways. This is especially true of the vascular system where, not only are the bundles bicollateral, but, in the stem, secondary thickening occurs in the internal phloem, necrosis of the first formed cells keeping pace with the production of new cells. A definite cambium is found only to the exterior of the xylem and this is exceptionally narrow and the cells have very delicate walls. Phloem necrosis may occur in any part of the tree. The development and lignification of the xylem is very uneven, but this seems to bear no relation to the season. Tyloses are formed in the vessels of the root and, to a less extent, in those of the stem. Starch reserves are usually small, but large quantities of tannins, oils and calcium oxalate are secreted in all tissues. The oil may be contained in special schizogenous glands which are abundant in the aerial parts of the tree. Much mechanical tissue, consisting of fibres and stone cells, is formed in the pith and cortex of the stem and in the phloem in all parts of the tree, but lignification of this tissue is very uneven. Occasional dead cells are found in all tissues, even in the primary meristem. In the leaf, the plastids develop very unevenly; this is followed by retarded development of the pigment in some parts, resulting in a flecked appearance. Stomata are exceptionally numerous; in the leaf, they are confined to the lower surface and always communicate with very small cavities. Air spaces in the mesophyll are very small and are almost non‐existent in other tissues. Bodies, morphologically similar to the amorphous intracellular inclusions due to some viruses but differing chemically from them, are abundant in the leaves.Some of these characters are usually associated with a diseased condition, but they occur in both healthy and diseased cloves in the Zanzibar Protectorate. In the sudden death suspect, some may occur earlier or be more accentuated than in the healthy tree. This evidence alone might suggest that sudden death is merely the culmination of a long period of adverse conditions, but other evidence suggests very strongly that the disease is due to a pathogen. Of the groups of organisms which may cause disease, only fungi were found. These occurred in the absorbing roots but are unlikely to be the pathogens causing sudden death, for, until the tree has actually wilted, very few hyphae are present, and no more than are found in healthy trees. Nothing incompatible with the suggestion that sudden death is caused by a virus was found.
SOME EFFECTS OF HOST NUTRITION ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION BY CERTAIN VIRUSES
Authors: BAWDEN F. C. , KASSANIS B. 
Published: February 2008

Fertilizer treatments that greatly influenced the growth of tobacco and potato plants in pots had little effect on the number that became infected with potato virus Y when the plants were colonized by equal numbers of infective aphids, though the number was slightly decreased by nitrogen and increased by phosphorus.The number of local lesions produced on leaves of tobacco and Nicotiana glutinosa by tomato aucuba mosaic and tobacco mosaic viruses was increased by additions of both nitrogen and phosphorus, provided that these also increased growth. The predominant effect of both nutrients in increasing susceptibility was indirect by increasing plant size, but over certain critical ranges both elements also increased the numbers of lesions produced per unit leaf area. Conditions of maximum susceptibility approximated closely to those producing optimal growth, and susceptibility, whether measured by lesions per half‐leaf or per unit area, was decreased by a deficiency or excess of either element. Sometimes the addition of nitrogen reduced susceptibility when still increasing plant growth.
STUDIES ON LUCILIA SPECIES (DIPTERA) UNDER DANISH CONDITIONS
Authors: CRAGG J. B. 
Published: February 2008

Whilst sheep myiasis caused by Lucilia sericata is a severe economic problem in Great Britain, it rarely reaches such proportions in countries bordering Western Europe. Possible reasons for this relative absence of myiasis were investigated in Denmark.During the period 19 July‐15 August 1948, trapping studies showed that blowflies normally associated with myiasis in Great Britain, and particularly L. sericata, occurred fairly abundantly in the Mols area of Jutland.The reactions of Danish L. sericata to attractive materials placed on sheep were similar to those shown by the species under British conditions. The number of egg batches laid on sheep in response to chemical stimuli were fewer than would have been expected in Great Britain.Studies on the fleece microclimate showed that relative humidities of 50 % or more frequently occurred on the skin surface. Humidities 3 cm. above the skin were markedly lower. Except during or immediately after rain, humidities high enough to ensure the hatching of blowfly eggs were never recorded.It is concluded that the absence of myiasis in Denmark and its relatively low incidence in other countries is not due to the existence on the Continent of a strain of L. sericata differing in oviposition habits from the British species.
STUDIES ON TWO APHID‐TRANSMITTED VIRUSES OF LEGUMINOUS CROPS
Authors: CHAUDHURI R. P. 
Published: February 2008

Pea mosaic virus was transmitted by Myzus persicae Sulz., Macrosiphum pisi Kalt., M. solanifolii Ash. and Aphis fabae Scop., but not by Hyperomyzus staphyleae Koch. It is a ‘non‐persistent’ virus (Watson & Roberts, 1939), and is most readily transmitted when vectors are fasted and then given a short infection feeding. Vector efficiency was not increased by increases in preliminary fasting beyond 15 min. or with increasing infection feeding beyond 1 hr. Most aphids became non‐infective within 15 min. when feeding, but fasting aphids remained infective for 3 hr. Species that fed readily on the infected plants were less efficient vectors than those which did not. Seed set by infected plants produced healthy seedlings.Pea enation mosaic virus persisted in Myzus persicae and Macrosiphum pisi for more than 140 hr.; its transmission was unaffected by preliminary treatments of aphids. No transmission was obtained until at least 4 hr. after aphids had left infected plants; usually the ‘latent’ period exceeded 1 day and its duration was apparently unaffected by the length of the infection feeding.
VIRUS DISEASES OF CACAO IN WEST AFRICA
Authors: POSNETTE A. F. , ROBERTSON N. F. 
Published: February 2008

Increasing the number of Pseudococcus njalensis per test plant increased the infection rate with cacao virus 1A and 1M to 95 % with twenty‐five insects. Young leaves with the red vein‐banding symptoms were better sources of virus than mature leaves, and there was evidence of virus localization in the plant. It was estimated that Ps. njalensis nymphs took about 16 min. to penetrate plant tissues with their stylets.Infection rates increased with time of test feeding up to 50 min. The virus was non‐persistent in the feeding insect, but persisted up to 36 hr. in insects starved after the infection feed. Starvation before the infection feed increased the infection rate with infection feeds up to 10 hrs., after which the infection rate with pre‐starved insects declined to the level attained by unstarved insects.
FIELD METHOD FOR THE DETERMINATION OF THE PARTICLE SIZE OF OIL MISTS
Authors: JONG J. R. de 
Published: February 2008

For the control of plant pests, e.g. insects, spraying machines have of late been developed, especially in the U.S.A., with which low dosages of fairly concentrated solutions of toxicants in mineral oils are sprayed. The efficiency of such products is no doubt influenced by the fineness of the spray. An accurate method of determining this fineness was desirable both for the control of the spraying operation and for evaluation of the merits of spraying apparatus.Knowledge of the average drop size is inadequate in this respect; it is necessary to know the distribution of the oil in droplets of different sizes. A reliable impression of this percentage can be obtained only if a large number of particles are measured. These measurements can be used to plot frequency curves based on number or volume distribution.A simple microphotographic method is described whereby these measurements can be made both in the laboratory and in the field. The procedure makes it possible to obtain, shortly after spraying, a good idea of the size of the oil drops in the deposit.An apparatus was designed and constructed to determine the diameter frequency curve and the volume distribution curve of oil droplets deposited in field spraying on coated glass plates.The method gave characteristic results for field sprayings with the Strawsonizer and a helicopter fitted with a spraying boom and also in the laboratory when using a spraying apparatus with different arrangements of the nozzle.
STATISTICAL ASPECTS OF THE INDEPENDENT JOINT ACTION OF POISONS, PARTICULARLY INSECTICIDES
Authors: HEWLETT P. S. , PLACKETT R. L. 
Published: February 2008

Methods are described for discovering whether a mixture of two poisons is as toxic as predicted on the hypothesis of independent joint action. These include X2tests and a procedure for finding the maximum likelihood estimate of the coefficient of correlation in resistance to the poisons. The methods are illustrated using data from insecticidal tests.In the insecticidal tests, flour beetles, Tribolium castaneum Herbst, were sprayed with, or exposed to films of, different insecticides in solution in Shell oil P 31. The insecticides were pyrethrins, D.D.T., and B.H.C., singly and in pairs. The statistical analysis of the results showed that pyrethrins and D.D.T. could have acted independently both as films and as direct sprays; D.D.T. and B.H.C. could have acted independently as films but not as direct sprays; and B.H.C. and pyrethrins could not have acted independently either as films or as direct sprays.These findings are discussed, and it is concluded that independent action should be regarded as a special case of a more general type of joint action for which the term dissimilar is proposed. A general method of approach is suggested for the conception and development of hypotheses of the joint action of poisons.
ON THE BACTERIA RESPONSIBLE FOR SOFT ROT IN STORED POTATOES, AND THE REACTION OF THE TUBER TO INVASION BY BACTERIUM CAROTOVORUM (JONES) LEHMANN & NEUMANN
Authors: JONES D. RUDD , DOWSON W. J. 
Published: February 2008

Bacterium carotovorum (Jones) Lehmann & Neumann and Pseudomonas syringae van Hall were the only two species of Gram‐negative bacteria isolated from rotting potatoes collected from clamps in England in 1945‐7. Both were found capable of producing a rot under known conditions, and both were isolated on plates of a pectate‐gel medium which is liquefied by these bacteria. Ps. syringae has not been recorded before as causing a rot of stored potatoes. In a slightly different type of rot which was ropy or gassy and often pink in colour, Gram‐positive spore‐forming bacilli were found, generally associated with Bacterium carotovorum. These bacilli proved to be anaerobes–species of Clostridium–one of which, when inoculated together with Bacterium carotovorum, produced a gassy rot pink in colour.On infection by Bad. carotovorum the tuber reacts to form a barrier of suberized cells, the extent and efficiency of which depend on temperature and relative humidity. Low temperatures and a low humidity favour the formation of the barrier and eventually of periderm; high temperatures favour the multiplication of the bacteria the advance of which is limited by humidities not reaching saturation. Fluctuations of temperature or humidity may promote a succession of barriers.
THE IDENTITY OF THE SWEDE MIDGE, WITH NOTES ON ITS BIOLOGY
Authors: BARNES H. F. 
Published: February 2008

A brief historical summary is given of the literature concerning Contarinia nasturtii Kieffer, C. torquens de Meijere and C. geisenheyneri Riibsaamen, three gall midges (Cecidomyidae) which have been associated respectively with leaf damage on Brassica spp. in England, identical malformation on the Continent and swollen and closed flowers of Brassica spp. in Europe.Following the discovery in England of the true Contarinia nasturtii causing swollen and closed flowers oiRorippa amphibia, preliminary experiments have shown that midges from this source will also cause similar damage to swede flowers and that they are the same species as those attacking R. amphibia blossom in the Netherlands.Further preliminary experiments have shown that swede midge derived from rape leaf axils will also cause identical damage to radish flowers in addition to breeding successfully on the leaves of turnip, swede, cabbage and radish.Male midges derived from Rorippa blossom have been mated with females from rape leaf axils, and their offspring have been reared on Rorippa flowers and on turnip leaves.This biological evidence confirms the previous supposition based on morphological grounds that the swede midge is Contarinia nasturtii Kieffer and will cause either flower or leaf damage. Consequently, C. torquens de Meijere and C. geisenheyneri Riibsaamen must remain synonyms.The shortest time for a generation (from parent to first offspring midge) to develop was 24–39 days in an unheated open glasshouse during June‐July in 1949 at Harpenden. Under the same conditions, the shortest time for the next generation from late July to August was 29–32 days. C. nasturtii is the first Contarinia species in which unisexual families have been discovered.
THE STRUCTURE AND FORMATION OF THE EGG OF THE FRUIT TREE RED SPIDER MITE, METATETRANYCHUS ULMI KOCH
Authors: BEAMENT J. W. L. 
Published: February 2008

The summer egg, and the overwintering diapausing egg of the fruit tree red spider mite, Metatetranychus ulmi Koch are described in detail; there is no reliable factor by which these two may be distinguished on inspection.Both types of egg have a common basic shell structure, consisting of an outer thick wax layer of very high melting point and a cement layer of oil and protein which attaches the wax to the underlying ‘shell’ layer enclosing the living material. The shell layer is extremely resistant to penetration and to attack by chemicals or solvents; it appears to be composed of a material similar to keratin. This layer is formed in the ovary, towards the end of yolk accumulation. The egg is apparently fertilized precociously, and there are no associated nurse or follicle cells; only one egg is matured at a time.The female reproductive system is described in some detail; the egg receives its shell layer in the simple sac‐like ovary, and then passes into a glandular ovipositing pouch which is evaginated through the genital aperture at oviposition. The shell layer makes contact with the substrate, and the pouch secretes the cement over the rest of the shell layer so that the egg adheres to the substrate by a ring of cement around the base. The outer wax is then secreted over the cement, and it also leaves large hole at the base of the egg, bordered by the cement.The female leaves the egg by rotating into an almost vertical position. In this process the ovipositing pouch is drawn off the egg, and withdrawn into the female; consequently, the wax, which is plastic when first secreted, is drawn up into the characteristic spike which surmounts the egg. The spike is of no further physiological significance to the egg.Owing to the hole in the egg‐coverings at the base, the shell structure is not waterproof. The developing organism waterproofs the summer egg by secreting wax layer into the inside of the shell about 6 hr. before laying, previous to which the egg will only survive in humidities greater than 85 yo R.H. After waterproofing, the egg readily develops in humidities of 30 yo R.H.The waterproofing wax has a transition point of 68°C. The shell of the winter egg is similarly composed and waterproofed, but winter eggs are held up in the female until a later stage of embryonic development, so that they are waterproofed when they are deposited on the bark.Some discussion is made of the importance of leaf and bark humidities in relation to the different times at which summer and winter eggs are waterproofed.
INVESTIGATIONS ON THE SYSTEMIC INSECTICIDAL ACTION OF SODIUM FLUOROACETATE AND OF THREE PHOSPHORUS COMPOUNDS ON APHIS FABAE SCOP.
Authors: DAVID W. A. L. , GARDINER B. O. C. 
Published: February 2008

The general insecticidal properties of bis (bis‐dimethylamino phosphonous) anhydride (anhydride), bis (dimethylamino) fluorophosphine oxide (oxide), diethyl paranitro‐phenyl phosphate (E600), and sodium fluoroacetate (acetate) are described. All are toxic to aphids when infested plants are dipped in solutions. Although this is thought to be a contact action the possibility that the materials are first absorbed by the leaves and that the aphids are killed by imbibing toxic sap is not excluded. The order of decreasing toxicity by dipping is E 600 > acetate > anhydride = oxide. At the lowest concentration giving a complete kill of aphids, the anhydride is the most persistently effective of the four compounds. E600 is the most phytotoxic compound.When applied to the roots the order of decreasing toxicity is acetate > oxide > anhydride > E600 in sand and soil, and acetate > oxide > anhydride = E600 in culture solution. The anhydride and acetate are more persistent in the plants than the oxide and E600. The margin of safety between insecticidal dosage and phytocidal dosage is appreciably larger with the acetate than with the other three compounds.When equal dosages are administered to plants by the cut tap root technique the order of decreasing toxicity to aphids is seen to be acetate > oxide > E600 > anhydride. All compounds, except possibly E600, appear to be absorbed by the intact roots of the plants.Systemic insecticidal action following application made to the leaves of the broad bean is easy to demonstrate with the acetate, demonstrable with difficulty with the anhydride and not at all with E600 and the oxide.Only the oxide is sufficiently volatile to kill insects by a fumigant effect either as the pure substance or after absorption into the plant. Plants treated with it give off a toxic vapour which may be collected by condensation and shown to be systemically active. The material concerned is presumed to be the unchanged oxide.Sodium fluoroacetate is an extremely effective systemic insecticide whether applied to the leaves or the roots of the broad bean. It is apparently not phytotoxic at several times the concentration necessary for insecticidal action but may prove to be too generally toxic or persistent for practical use.
MICROBIOLOGICAL CONTROL OF BOTRYTIS CINEREA PERS. II. ANTAGONISM BY FUNGI AND ACTINOMYCETES
Authors: NEWHOOK F. J. 
Published: February 2008

Botrytis cinerea has been inhibited by pure cultures of many fungi and actinomycetes on lettuce extract agar and by these and by the mixed flora of soil suspensions on wounded detached lettuce leaves and on wounded leaves of living plants under conditions of high moisture and humidity. Control was exhibited in many cases at 4° C. though this was less marked than that at 15–25° C. Most fungal activity raised the pH to 7.8–8‐4 but the use of buffered media showed that most species were antagonistic because of the production of antibiotic substances independently of the high pH. Prior inoculation with soil suspensions was necessary to obtain control of B. cinerea on wounded leaves of living plants although such suspensions and several fungi had given control on simultaneous inoculation with B. cinerea on wounded detached leaves.Saprophytic antagonism is responsible for some of the natural control of B. cinerea in the field. The amount of available moisture, which in turn is affected by the relative position of the dead tissue on the plant as well as by climatic factors, greatly influences the establishment and growth of B. cinerea and the amount of microbiological antagonism likely to be exerted.Three‐weekly applications of suspensions of Cephalosporium sp., Fusarium flocciferum and Phoma eupyrena failed to give a significant increase in the final survival of lettuce in the field. On the other hand, 3‐weekly applications of a dust containing tetrachloronitrobenzene gave a highly significant increase in survival, efficiency being greatly increased by the use of cloches.Earthing up induces early rotting of the petioles of ageing leaves and so probably prevents entry of Botrytis cinerea into the stem. Increased survival in hollows as compared with ridges is apparently due largely to this earthing up effect and possibly also to increased microbiological activity on dead tissue under the wetter conditions. B. cinerea can enter the soil by invasion down the root systems of attacked plants and can attack other root systems in contact with these. Furthermore it has been recovered from the soil over 6 weeks after the disappearance of infected plants from above ground, despite the antagonism shown to be exerted by soil organisms.Control of B. cinerea on Epilobium sp., Ranunculus repens, R. flammula and Lamium amplexicaule was obtained by prior inoculation of killed tissue with soil suspensions.
THE CONFIRMATION OF THE VARIETY FABAE KEAY OF SCLEROTINIA TRIFOLIORUM ERIKSSON
Authors: LOVELESS A. R. 
Published: February 2008

There is confusion as to whether the Sclerotinia on Vicia faba is a normal strain of Sclerotinia trifoliorum as found on clover and related legumes or a distinct variety (var. fabae). Pathologically the two fungi appear to be the same, and field observations indicate that beans in the rotation may aggravate the incidence of clover rot. A re‐investigation of the morphology of the two fungi is made to assess the status of var. fabae.The two fungi could not be distinguished by apothecial characters or cultural behaviour. Ascospore measurements confirm the existence of S. trifoliorum var. fabae, although 5. trifoliorum proper also occurs on beans. Var. fabae has not been found on any legume besides beans. Isolates from trefoil and sainfoin agree in spore size with S. trifoliorum on clover.When isolates of S. trifoliorum are co‐inoculated on the same Petri plate, they either do not react, or react to form a ‘demarcation line’. Although a demarcation line is assumed to imply a genetic difference, non‐reaction does not necessarily imply genetic identity. Non‐reaction and the formation of a demarcation line also occur when var. fabae strains are co‐inoculated together. When an isolate of S. trifoliorum is co‐inoculated with an isolate of S. trifoliorum var. fabae an ‘incompatibility line’ is formed. Use can be made of this fact in identification.On the basis of co‐inoculations 5. trifoliorum and S. trifoliorum var. fabae are both shown to constitute a diverse range of biotypes. Segregation of biotypes in the ascus as a result of heterokaryosis in the ascus‐initial is demonstrated. The view is expressed that heterokaryosis is the mechanism underlying the production of new biotypes.