bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of potassium chloride on the infestation of sugar beet by beet eelworm, Heterodera schachtii Schmidt
Authors: CURTIS GODFREY J.
Published: February 2008

A high‐potassium compound fertilizer (N, 9 parts; P, 4 parts; K, 15 parts) increased sugar‐beet size and reduced the number of cysts of Heterodera schachtii on the roots: the same effects were induced by potassium chloride, and a smaller reduction in cyst number occurred after application of a standard compound fertilizer (N, 7; P, 3; K, 5·8 parts).

Application of 0·1M potassium chloride solution 2 weeks before inoculation brought about the greatest reduction in infestation; the optimum invasion by eelworm occurred after KCl application at strengths between 0·01 and 0·001M.

Larvae stimulated to emerge by leachates from potassium‐treated plants were more infective than those stimulated by control leachates. Leachates from potassium‐deficient plants induced quicker and cumulatively greater hatching of cysts than did leachates from plants receiving potassium. Where only part of the root system was grown in 0·1 m KCl solution, larval invasion in the untreated portion was lower than in controls. No indication of a relationship between potassium content and infestation was observed among lines of beet selected for high and low potassium content of ‘roots’ for processing, although there was a significantly reduced population of cysts in the high‐potassium plants. In the field, large doses of potassium chloride applied as top dressings reduced the reproduction of the eelworm to below the maintenance level: sugar content and yield of the marketable ‘roots’ were unaffected: potassium content was increased.
Purple blotch (Alternaria porri) of onion in Kenya
Authors: BOCK K. R.
Published: February 2008

In 1961 an epidemic attack by Alternaria porri occurred on irrigated onions at Baringo in the Rift Valley, Kenya. Two distinct lesion types appeared: (1) typical purple or brown blotches; (2) white, irregular spots or flecks. These were present in varying proportion, depending on the duration of conditions favourable to infection, and subsequent relative humidity. High R.H. favoured the development of purple blotches; low R.H. for prolonged periods after infection usually resulted in white flecking only. These flecks were often sterile, making diagnosis difficult.

Germination, appressorial and lesion formation displayed a broad optimum temperature (21–30° C). Resistance to the disease shown by a number of American hybrid onions was governed by cuticle thickness; this resistance was reduced by wounding—such as is associated with sand‐storm blast—or by incubation after infection for prolonged periods at high R.H.

Two fungicides, mancozeb and dicloran, effectively controlled the disease in the field.
The effect of the composition of the storage atmosphere on the development of rotting of Cox's Orange Pippin apples and the production of pectolytic enzymes by Gloeosporium spp
Authors: EDNEY K. L.
Published: February 2008

Storage of Cox's Orange Pippin apples in 5% CO2+ 3% O2 or 0% CO2+ 3% O2 at 3·3° C. reduced rotting by Gloeosporium spp., as compared with storage in air. 5% CO2+ 16% O2 was less effective and reduced rotting on fewer occasions. In some years no reduction of rotting was obtained by storage in these gas mixtures. Retardation of rotting was sometimes achieved during the early part of the storage period by treatments which did not control rotting over the whole period. Production of pectolytic enzymes was reduced by incubation in these atmospheric conditions; the effect on G. album was greater than on G. perennans.
The effects of D‐D treatments applied during a five‐course rotation on the soil population of Heterodera rostochiensis Woll
Authors: DONCASTER C. C.
Published: February 2008

A field cropped with potatoes in the 1st and 6th years and with non‐host crops in the 2nd to the 5th years was divided into plots for D‐D injection, each at 400 lb./acre. Before the final potato crop, untreated plots showed a 50% mean annual decline of the population of potato‐root eelworm. Single injections in different years left populations not materially different. With repeated injections there was a progressive decrease in the proportion of nematodes killed. However, injections for 4 or 5 consecutive years decreased the populations by spring of the 6th year enough to affect them after the final host crop was grown. Under this crop, all populations increased to about the same extent.
The effect of temperature in a sack‐drier on survival of insects (Oryzaephilus surinamensis (L.) (Col., Silvanidae)) and weed seeds (Avenafafua L. and A. ludoviciana Dur.)
Authors: WILLIAMS GWYNETH C. , THURSTON JOAN M.
Published: February 2008

Three kinds of damp sacks, taking 10 min. to pass through a drying plant, the heating panels of which averaged approximately 200°C., were heated to temperatures ranging from 46 to 95°C. and remained above 60°C. for not more than 5·5 min. All insects (Oryxaephilus surinamensis) attached to the sacks were killed. Seeds of Avena fatua and A. ludoviciana were more heat‐resistant than insects. Even when similar dry sacks with Avenu seeds attached were passed through the drier at its slowest rate (18 min.) with the heaters set as hot as possible without damaging the sacks, not more than 40% of the seeds were killed, although temperatures reached 81–135°C., and 105°C. was maintained or exceeded for 4–7°5 min. on the sides and faces of the sacks.
Purification and properties of lettuce mosaic virus
Authors: TOMLINSON J. A.
Published: February 2008

Lettuce mosaic virus (LMV) was partially purified from homogenates of infected lettuce leaves in 0·5 M sodium borate buffer (pH 7·5) containing 0·1% thioglycollic acid. The filtered homogenate was clarified by adding butanol and the virus was concentrated and partially purified by differential centrifugation. Such preparations were infective at dilution up to 10‐3. Comparable preparations made in potassium phosphate buffer were not infective.

Electron‐micrographs showed the virus preparations to contain long, flexuoiis particles with a mean length of 746 and width of 13 mμ. Antisera made by injecting such preparations intravenously into rabbits precipitated specifically with the preparations and with extracts from infected leaves.
Some factors affecting the rotting of stored apples by Gloeosporium spp
Authors: EDNEY K. L.
Published: February 2008

The susceptibility to rotting by Gloeosporium spp. of fruit from sixty‐two Cox's Orange Pippin apple trees on two plots has been found to vary from tree to tree and from year to year. There are indications that the level of inoculum released each year also varies. Examination of pruning snags and old fruiting spurs from one of these plots showed that 6% were infected with either G. perennans or G. album. Of 650 pruning cuts made in the winter of 1957‐58, 19 % subsequently became infected with Gloeosporium spp. Changes in the susceptibility of apples during a 2‐week period at harvest time markedly affected the incidence of rotting in store. No differences were found in the rates of spread of G. perennans in the cortical tissues of Cox's Orange Pippin apples of different sizes following inoculation.

Germination of G. album on the surface of the apples is followed by a slight swelling of the tip of the tube germ, but no evidence has been obtained that this swollen tip functions as an appressorium. Inoculations of single lenticels with suspensions of spores of G. album in apple juice were relatively more successful than inoculations using aqueous suspensions, but little more than half of the inoculations were successful. Inoculations of the cortical tissues were also only partly successful and, for either method, the ease of infection was not found to increase with increasing maturity of the fruit.
Studies on the application of a copper fungicide for the control of coffee leaf rust
Authors: PARK P. O. , BURDEKIN D. A.
Published: February 2008

A proprietary cuprous oxide fungicide was applied to unshaded single‐stem coffee as both a high‐ and a low‐volume spray. Initial deposition of fungicide was not affected by the volume of application. An improved sampling method, used in the second year of the trial, showed that despite efforts to direct the spray on to the under leaf surface, more fungicide was applied to the upper.

The deposits arising from high‐volume applications were more susceptible to weathering and this weathering was most marked from the upper leaf surfaces. It was noted that irrigation within 48 hr. of spraying caused a considerable reduction in fungicide deposit.

A visual scoring technique indicated that a large proportion of the leaves received no fungicide at all and it was concluded that subsequent redistribution may occur.

The biological assessments indicated that high‐ and low‐volume application of copper fungicide gave equally good leaf rust control and leaf retention. Reducing the fungicide application from 5 to I lb./acre resulted in reduced fungicidal efficiency.

A ‘disease control index’ was developed to show the relationship between the level of fungicide deposit and the degree of leaf rust control. A mean total deposit of approximately 60 mg./m.2 leaf area was required for satisfactory protection.
Review
Authors: COOPER K. E.
Published: February 2008

The Collected Papers of Paul Ehrlich. (in four volumes). Compiled and edited by F. Himmelweit with the assistance of Martha Marquardt, under the editorial direction of Sir Henry Dale.
Transmission of beet yellows virus by alate and apterous aphids
Authors: HEATHCOTE G. D. , COCKBAIN A. J.
Published: February 2008

Myxus pusicae alatae and apterae were consistently better vectors than Aphis fabae of beet yellows virus, but there was little difference between the ability of alatae and apterae of each species to transmit.

Alatae born and reared on infected plants transmitted no more readily than alatae that had fed on infected plants for only one day. No individual became infective after feeding on the plants for only 5 min., and few were infective after feeding for 30–60 min. Alatae and apterae were about equally infective after similar feeding times on infected plants.

Apterae kept from feeding and at various temperatures up to 30°C. for 4 hr. after their infection feed, all transmitted equally often. Alatae transmitted as readily after a 4 hr. flight as after a 15 min. one. Some alatae of M. persicae remained infective longer than apterae, but most individuals of both ceased to be infective within 2 days of leaving infected plants. Most alatae ceased to fly 3–5 days after the final ecdysis because their flight muscles autolysed.

A. fabae and Rhopalosiphoninus staphyleae transmitted BYV rather less than half as often as did M. persicae. Macrosiphum euphorbiae and Aulacorthum solani transmitted only rarely and transmissions were not obtained with Megoura viciae, Metopolophium festucae and Rhopalosiphoninus latysiphon.
Death of maiden apple trees caused by Phytophthora syringae Kleb. and a comparison of the pathogen with P. cactorum (L. & C.) Schroet
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

Phytophthora cactorum and the closely related (but only recently implicated) species, P. syringae, cause collar rot of mature apple trees, but infection of young trees is uncommon. In a Kent orchard, 279 maiden trees of Cox's Orange Pippin, Worcester Pearmain and Tydeman's Early Worcester were infected by P. syringae whilst heeled‐in prior to planting, and subsequently killed.

These two paragynous antheridial species can readily be distinguished in agar culture. P. cactorum grows best at 25° C. and forms a diffuse, azonate colony with abundant reproductive structures; sporangia are uniformly obpyriform, markedly papillate, and occur in terminal clusters on the sporangiophores. P. syringae grows best at 20° C., very slightly at 25°C., and forms a compact, radially zonate colony with sparse reproductive structures; sporangia are irregular in size and shape, have a broadly flattened apex, and occur singly on the simple sporangiophores.

Inoculation studies demonstrated that young trees are particularly susceptible to P. syringae during the period of low temperature and tree dormancy: the rate of lesion extension for P. syringae was inversely related to the mean accumulated air temperature while the reverse was true for P. cactoriim.

Measures recommended for the protection of young trees during the pre‐planting period aim at preventing contact of scion variety stems with wet soil.
Investigations on fungicides
Authors: CARTER G. A. , WAIN R. L.
Published: February 2008

The systemic therapeutic activity of eighty‐eight inorganic salts was assessed by determining their ability to protect broad bean seedlings from Botrytis fabae, tomato plants from Alternarin solani and wheat seedlings from Erysiphe graminis following root application to the host plants. Lithium sulphate, when applied to wheat seedlings, showed marked systemic activity against E. graminis. The toxicity of the salts towards Botrytis fabae was determined using the standard spore germination test and their toxicity towards broad bean and wheat seedlings was also assessed. Further tests were performed to ascertain the effect of bean sap upon the fungistatic activity of the salts. The degree of systemic activity shown by the salts is discussed in relation to such factors as their fungitoxicity, mode of action, fungitoxicity/phytotoxicity ratios, uptake by the plant and the degree to which plant sap inactivates them.
Hop line‐pattern virus in relation to the etiology and distribution of nettlehead disease
Authors: LEGG J. T.
Published: February 2008

Hop line‐pattern virus (HLPV) was transmissible by mechanical inoculation to hop plants; it induced characteristic severe symptoms in Humulus lupulus L. var. neo‐mexicanus Nels. & Cockerell and the commercial derivatives College Cluster and Keyworth's Midseason, but none in the traditional English varieties of H. lupulus (e.g. Fuggle).

Mechanical transmission of hop nettlehead virus (HNV) was facilitated by the presence of HLPV in the test plants; hop seedlings and clonal plants escaped infection by sap inoculum that infected plants of two varieties already infected with HLPV. HNV was also transferred by stem contact and by knife cuts to plants carrying HLPV.

Infection with HLPV was latent in twelve nettlehead‐diseased Fuggle plants from different fields, and in diseased and symptomless plants in a nettlehead outbreak in W.G.V., a variety that previously had escaped infection. It is suggested either that HLPV predisposes hop plants to infection with HNV or that nettlehead disease is caused by dual infection with both viruses.

Localized and scattered patterns of nettlehead spread were observed in hop plantations; these two types are usually attributed to different modes of spread which would be compatible with a complex etiology of the disease.
The uptake of phorate, a systemic insecticide, applied as a slurry to wheat and mustard seeds
Authors: BARDNER R.
Published: February 2008

The absorption by plants of wheat and mustard of a systemic organophosphorus insecticide (phorate), applied as a slurry seed dressing, was studied by caging the aphid Rhopalosiphum padi (L.) on the foliage of wheat, and the aphid Brevicoryne brassicae (L.) and the Chrysomelid beetle Phaedon cochleariae (F.) on white mustard, grown from phorate‐treated seed.

Wheat and mustard plants quickly lost their toxicity to insects when they were transplanted, suggesting that most of the insecticide from a slurry seed treatment passes into the soil and is picked up by the roots. That phorate or its derivatives occur in the soil was shown by tests of anticholinesterase activity. Insecticide can also pass into the seed of wheat and move to the growing embryo. Phorate becomes closely bound to the testa of mustard, but does not penetrate it to reach the cotyledons or other parts of the embryo. Mustard cotyledons can become contaminated by insecticide as they emerge through the soil.

Young and old leaves of both wheat and mustard depend on continued absorption of insecticide from the soil to maintain their toxicity. No insecticide moves from old to young leaves. Old leaves lose their toxicity to insects more slowly than young ones. When treated seeds are sown close together, the overlapping zones of insecticide round each seed can increase strength and persistence of insecticidal effect. This happens more with dimethoate, which readily dissolves in water, than with phorate, which is almost insoluble. At normal sowing rates the zones of insecticide round each seed would rarely overlap.

Roots of wheat and mustard from treated seed did not excrete insecticide, and the roots did not carry insecticide through the soil.
The effects of rates of supply of nitrogen, phosphorus, potassium and magnesium on leaf and stem growth, flowering and ‘topple’ of Golden Harvest and Elmus tulip
Authors: CHEAL W. F. , HEWITT E. J.
Published: February 2008

In factorial nutrition experiments with three rates of nitrogen, phosphorus and potassium—with some additional treatments with magnesium—on two bulb sizes of Golden Harvest and Elmus tulip, the effect of nitrogen was outstanding. Flowering was retarded by low and high rates of nitrogen supply. Increased nitrogen decreased the length of the first internode of Elmus. Mineral deficiency symptoms in leaf and stem showed minor varietal differences.

Elmus tulips receiving amounts of calcium normally considered adequate developed ‘topple’ when given no nitrogen especially when combined with high potassium: these treatments also induced stem contortion in Golden Harvest, which appeared to be an analogous disorder to ‘topple’.
The structure of the egg‐shell of the cabbage root fly, Erioischia brassicae
Authors: HINTON H. E. , COLE S.
Published: February 2008

The structure of the egg‐shell of Erioischia brassicae (Bouché) (Muscidae, Anthomyiinae) has been investigated with the aid of an electron‐microscope. The shell outside the hatching lines consists of three layers. The middle layer is a coarse meshwork, the struts of which are about 1–2μ thick. The upper layer consists of vertical columns that arise from the middle layer. These vertical columns or struts branch and anastomose at their apices in the plane of the shell and form a network that is the outermost wall of the shell. The struts of this outermost network are 0.01‐0.1μ thick and thus little of the outermost wall of the shell can be resolved with the light microscope. The inner layer consists of vertical columns usually 2–5μ long. These branch and anastomose at their apices in the plane of the shell and form a network that is the innermost wall of the shell. The median strip between the hatching lines lacks an outer network. The meshworks of the shell offer little protection against desiccation, and water, alcohols, and relatively mobile oils pass readily through the shell.
Further experiments on the effect of beetle predators on the numbers of the cabbage root fly, Erioischia brassicae (Bouché), attacking brassica crops
Authors: COAKER T. H.
Published: February 2008

Further experiments to determine the importance of beetle predators were carried out at Wellesbourne during the three years 1960‐62. By using barriers to restrict the movement of adult carabids into and out of plots of brassica crops it was shown that the survival of the immature stages of the root fly was inversely related to the population level of predatory carabids. After excluding adult carabids almost entirely from the plots it was estimated that they had been responsible for up to one‐third of the total egg mortality, although this varied with the species composition of the carabid population. Initial differences in egg survival resulting from predation by carabids were reduced as the cabbage root fly life‐cycle progressed and were due to other losses of which predation by adult Staphylinidae was important. Such differences in egg survival, however, led to substantial crop yield reductions, particularly in dry weather.
The genetic relationships of pathotypes of Heterodera rostochiensis Woll. which reproduce on hybrid potatoes with genes for resistance
Authors: JONES F. G. W. , PARROTT DIANA M.
Published: February 2008

The hypothesis is advanced that the major genes for resistance to Heterodera rostochiensis in potatoes bred from Solanum tuberosum ssp. andigena (Ab), from S. multidissectum (aB) and from both (AB) are matched by recessive genes in the nematodes able to overcome resistance, The hypothesis postulates the existence of a pathotype that multiplies only on ab plants (susceptible commercial potatoes) and of one that multiplies on plants with both genes (AB). Evidence for the first is of a negative kind but there is positive evidence for the second. When the results of pot tests were combined with tests previously made by Jones & Pawelska (1963), and the forty populations were divided into four groups, the proportions of pathotypes in two groups fitted expectation. Proportions also fitted expectation for the other two groups and for the means of all forty populations when an adjustment was made to allow for the excessive number of cysts formed on plants ex andigena (Ab). The three groups of populations with appreciable numbers of the pathotype able to reproduce on AB plants discriminated between AB plants with and without an additional factor for resistance derived from S. multidissectum. This indicates the existence of yet another pathotype. AB plants with the additional resistance were about equally as resistant as S. vernei to all forty populations.

Assuming that males of all genetic constitutions (AA, Aa, aa) can mature in the roots of resistance plants but only recessive females (aa) can mature, the proportion of aa progeny should rise to 50 % at the end of the second generation. Pot experiments fit expectation but, in field plots, persistence of the old population delays increase in the proportions of recessive individuals. The growing of plants with one dominant gene for resistance increases the proportions of the pathotype that can reproduce upon them and also that which can reproduce on plants with both genes.

The hypothesis parallels the gene‐for‐gene theory advanced to explain the inheritance of the ability of certain rust fungi to overcome the resistance of their hosts but, when applied to Heterodera rostochiensis, has to take into account the faculty of larvae to become either male of female according to circumstances.
Growth of Cucumis sativus, variety Butcher's Disease Resister, with two concentrations of carbon dioxide
Authors: NEWTON PETER
Published: February 2008

Supplementary carbon dioxide increased the growth rate of cucumber (Cucumis sativus, variety Butcher's Disease Resister) in pots in a glasshouse, by increasing both net assimilation rate and leaf expansion. It increased areas of individual leaves by increasing their growth rate before they emerged from the terminal bud. Growth rate after emergence was unaffected by CO2 concentration. When the pots became full of roots, increasing CO2 concentration had less effect on leaf growth, probably because of indirect effects of restricted root growth.
Investigation of carnation viruses
Authors: HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Carnation ringspot virus (CRSV) was isolated from twenty‐three carnation cultivars, was readily transmitted by grafting and sap‐rubbing inoculation, and was spread among carnations by handling. CRSV was cultured in Nicotiana clevelandii or carnation and assayed in Chenopodium amaranticolor; Gomphrena globosa was the best diagnostic indicator plant.

CRSV was not transmitted by Myzus persicae or through seed of Dianthus barbatus. The virus infected sixty‐two out of ninety‐six plant species tested, but carnation is the only plant likely to be a virus source for commercial stocks. The concentration of CRSV decreased greatly in the terminal 1–2 mm. of the carnation shoot apex and, unlike carnation mottle, CRSV was not detected in the meristem dome; it was, however, present in some first leaf primordia. Clones free from the virus were obtained by aseptic culture of excised meristem‐tips, but more easily by growing infected carnations at 38–40d̀ C. for 4 weeks, followed by striking small cuttings or culturing meristem‐tips.

N. clevelandii sap was infective after dilution to 1/100,000, heating for 10 min. to 85d̀ C. but not 90d̀ C., and storage for 16 days at 20d̀ C. or 3 months at 0d̀ C. Purified and concentrated preparations of CRSV from carnation, D. barbatus or N. clevelandii were highly infective, contained polyhedral particles about 29 mμ diameter, were antigenic, and produced a specific light‐scattering zone in density‐gradient centrifugation. The S20, w at infinite dilution was 140. CRSV shares many in vitro properties with eleven other viruses having similar particle shape, but it was not serologically related to any of them.
Some properties of clover yellow vein, a virus from Trifolium repens L.
Authors: HOLLINGS M. , NARIANI T. K.
Published: February 2008

A virus differing from those previously described from leguminous plants was obtained from Trifolium repens in Surrey, and named clover yellow vein virus. It was transmitted by Myzus persicae and Acyrthosiphon pisum (not by Aphis fabae) in the non‐persistent manner, but not through seed. The virus infected nineteen out of sixty‐one plant species inoculated with sap: it was cultured in Nicotiana clevelandii, which reacted diagnostically and developed intracellular inclusions, and assayed in N. tabacum or Chenopodium quinoa. N. clevelandii sap was still infective after dilution to 1/10,000, heating for 10 min. at 55d̀ C. but not 60° C., and storing for 8 days at 18° C. or 75 days at 0° C. Infectivity, but not serological activity, was abolished by 0.2 or 2.0 % formaldehyde.

Symptoms of clover yellow vein virus (CIYVV) were suppressed, and the virus was not detected, in infected N. clevelandii plants grown for 4 weeks at 38° C. Symptoms and detectable virus returned 5–6 weeks after heat‐treatment ceased. The virus had particles of normal length 670 mμ, and was partially purified and concentrated by several methods. Virus preparations gave specific zones when centrifuged in density gradients. CIYVV shares many properties with the aphid‐transmitted, slightly flexible rod‐shaped viruses in group 8 of Brandes & Wetter, but no relationship was detected serologically to those tested or to four other viruses with particles of similar dimensions.
Studies on parsnip canker
Authors: CHANNON A. G.
Published: February 2008

Cankers of parsnips growing in the East Anglian fens were caused by a species of Centrospora. Comparison of the morphology and pathogenicity of isolates from infected roots with those of isolates from carrot and celery and also with published information, indicated that the fungus from parsnips was C. acerina. One of the parsnip isolates saltated to give sectors resembling a culture received from the Centraalbureau voor Schimmelcultures, Baarn as C. macrospora, confirming that, as reported previously, this fungus is a form of C. acerina.

The foliage of a wide range of seedling hosts was susceptible to artificial infection.

In a laboratory test, wounding of parsnip roots before inoculation with Centrospora did not increase lesion development. Lines of parsnip bred for resistance to Itersonilia and Phoma were also resistant to attack by Centrospora.

In view of the susceptibility of parsnips, carrots and celery to infection by C. acerina, adequate rotation on fen soils, where these crops are frequently grown, is advisable.
The epidemiology of tomato mosaic
Authors: BROADBENT L.
Published: February 2008

A tomato strain of tobacco mosaic virus infected, on average, about half the cleaned seeds from infected fruits. The proportion differed with tomato cultivar, time of infection and truss. Virus content also varied; seeds usually carried TMV externally, in low concentrations, but about a quarter also carried it within the testa or the endosperm. High virus concentrations sometimes occurred internally, usually when the endosperm was infected. Internal infection decreased, mainly by absence of virus in the testa, as the plant age at the time of infection increased. Endosperm infection occurred mainly in fruits from flowers that set after the plants were infected. The proportion of fruits with seeds was smaller in early infected plants than in those infected later. Fewer necrotic, blackened seeds were obtained from late‐infected plants than from those infected earlier, and more necrotic seeds were infected with TMV than normal ones, especially in the endosperm. Although the embryo was sometimes contaminated during dissection, virus within it was never confirmed. Necrotic seeds often failed to germinate.

Treating the fruit pulp with one‐quarter of its volume of conc. hydrochloric acid for 30 min. was the best means of cleaning seeds and of eliminating TMV carried externally. Fermentation and sodium carbonate extraction did not eliminate external TMV. Soaking previously cleaned seeds in 10% Teepol (Shell non‐ionic detergent) solution for 2 hr., or in a 10% tri‐sodium orthophosphate solution for 20 min. also inactivated external virus. The only treatment that often eliminated TMV carried internally was heating dry seeds in an oven at 70d̀C; treatment for 3 days was usually enough to free seeds completely but sometimes 3 weeks would not eliminate all virus, particularly that carried by the endosperm. Such treatments did not affect percentage germination of seeds other than recently harvested ones, but heated seeds sometimes took longer to germinate than unheated ones.

TMV was lost within a few months in some stocks of seeds but persisted for at least 9 years in others with endosperm infection. Virus content of seeds fell rapidly for 2 weeks after sowing but then remained at a low level for many weeks. Plants never became infected when allowed to grow undisturbed after the seeds were sown. ‘Seed‐infectio’ occurred only when the seedlings were pricked out (transplanted) and the testas or remaining endosperm were rubbed against the seedlings. The proportion of plants thus infected was usually small because (1) many seeds did not carry virus; (2) virus was rapidly inactivated after sowing; (3) after normal sowing 65% of testas were left behind in the soil when the seedlings were pricked out; (4) very young seedlings resisted infection: and (5) infection was more likely with recently harvested than with older seeds, probably from TMV remaining on the testas. However, all seedlings which were infected, even with dilutions of TMV‐infected leaf sap leaf in water as low as one part in five millions, showed symptoms within 3–5 weeks.
Studies on resistance and tolerance to cocoa viruses in Ghana
Authors: ATTAFUAH ALEX. , GLENDINNING D. R.
Published: February 2008

Cuttings of twenty‐seven cocoa selections were infested with mealybugs (Planococcus njalensis) which had fed on plants infected with the New Juaben strain of cocoa swollen shoot virus. Susceptibility to infection with CSSV seemed to vary, and in general those selections which had appeared relatively resistant in earlier studies again appeared resistant. There were great differences in reaction to infection, clones from Scavina × unknown progenies being least affected while various other Amazon selections, particularly some from Iquitos × unknown and Nanay × Iquitos progenies, were also very tolerant. Some local Trinitario selections displayed a measure of tolerance. The tolerance results were similar to those previously obtained in Ghana with the same virus and using beans or seedlings, and also to those obtained in field trials and with budded material infected with Nigerian virus isolates.
The biology of Sclerotinia trifoliorum Erikss. and other species of sclerotium ‐forming fungi
Authors: WILLIAMS G. H. , WESTERN J. H.
Published: February 2008

The survival in soil of sclerotia of Sclerotinia trifoliorum, S. sclerotiorum, Sclerotium delphinii and S. rolfii was studied. Those of S. rolfsii disintegrated in less than 1 month, while 95% of those of S. delphinii and Sclerotinia sclerotiorum were recovered after 2 years.

Sclerotia of S. trifoliorum placed in soil in March slowly diminished in numbers over the summer months, and in late autumn there was a rapid decrease in those near the surface, as a consequence of apothecial formation. This rapid fall did not occur when sclerotia were buried under clover. Over the winter, sclerotia 1 and 2 in. deep increased in numbers by the formation of secondary sclerotia. Secondary sclerotia also occurred in samples of Sclerotinia sclerotiorum.

Soil moisture content affected sclerotial survival, an accelerating decline in numbers being noted up to a soil moisture‐holding capacity of 30%. Above this level, increasing numbers of secondary sclerotia were formed, so that the numbers of sclerotia recovered were sometimes greater than those originally buried.

Sclerotia became more liable to decay after producing apothecia, but they did not invariably disappear, and some were capable of forming two or possibly three crops of apothecia in successive years.
The detection of antifungal substances before and after infection of beans (Vicia faba L.) by Botrytis spp.
Authors: PURKAYASTHA R. P. , DEVERALL B. J.
Published: February 2008

Previous work showed that germ‐tube growth of Botrytis cinerea, but not of B. fabae, is inhibited several hours after germination on the leaves. This study concerns the detection of substances in leaves and pods which could explain the different responses of the two fungi.

Ether and methanol extracts of leaf surfaces were not inhibitory to either fungus. Drops of water which were incubated for periods up to 48 hr. on healthy leaf surfaces became slightly inhibitory to germ‐tube growth of both fungi. However, drops of water containing spores of B. cinerea became highly inhibitory after incubation on surfaces of leaves or in seed cavities of pods for 72 or 24 hr. respectively. Drops containing spores of B. fabae and water controls became stimulatory to test spores after incubation for 24 hr. in pods but slightly inhibitory after 72 hr. on leaves. The inhibitory substances were partially extracted from collected drops into petroleum ether. Substances soluble in petroleum ether extracted from the endocarp of pods were highly inhibitory to test spores 24 hr. after infection by B. cinerea but stimulatory before infection or 24 hr. after infection by B. fabae.
The effect of some fungicides and herbicides on ascospore production of Venturia inaequalis (Cke.) Wint.
Authors: HUTTON K. E. , BURCHILL R. T.
Published: February 2008

The ascospore productivity of severely scabbed apple leaves was reduced by 93.7–99.9% by a single autumn application of phenylmercuric chloride (PMC) over a concentration range of 0.0025–0.1%. Phenylmercury dimethyl‐dithiocarbamate (PMD) was slightly less effective at equivalent concentrations of mercury. Of the non‐mercury compounds tested, only high concentrations of didecyldimethylammonium bromide and the herbicide diuron approached PMC in effectiveness. Low concentrations of PMC applied in the spring reduced the numbers of ascospores released from leaves bearing mature perithecia.

A new technique for estimating the ascospore productivity of overwintered apple leaves is described.
Studies on two races of Bremia lactucae Regel
Authors: CHANNON A. G. , WEBB M. J. W. , WATTS L. E.
Published: February 2008

Two races of Bremia lactucae are described; race W.1, which can attack various lettuce varieties now being grown commercially but cannot attack the resistant lettuces bred at Wellesbourne, and race W.2, which can infect not only the market varieties but also some of the W.1‐resistant lines. Race W.2 was shown to arise directly from race W.1, possibly by mutation.

The length of incubation time from inoculation to sporulation of the mildew in lettuce leaves decreased as the number of spores applied in the inoculum increased. This fact was used to assess the concentration of race W.2 spores in naturally occurring spore populations, by comparing the effects on W.1‐resistant plants of graded dilutions of spores from the field with those of known concentrations of race W.2. These tests showed that race W.2 was most prevalent where W.1‐resistant lettuces had been grown for some years. Race W.2 spores were found, however, where no W.1‐resistant lettuces had been grown, and it appears that race W.2 may be a normal constituent of most Bremia populations. The importance of these findings in relation to future breeding for downy mildew resistance is discussed.
The influence of volatility and water solubility of systemic insecticides on their movement through soil and absorption by plant roots
Authors: BURT P. E. , BARDNER R. , ETHERIDGE P.
Published: February 2008

When applied in the soil at the time potato tubers were planted, phorate and disulfoton were more effective than dimethoate and menazon in controlling aphids on the foliage of the crop in dry years, but all four were equally effective in wet years. The reason was sought by comparing the ability of the roots of wheat seedlings to absorb these systemic insecticides from air and from water. When absorbed from solution in water, all four insecticides were almost equally effective in killing Rhopalosiphum padi fed on the leaves, but when the roots were in contact only with the vapours of the insecticides, phorate and disulfoton were much more effective than dimethoate or menazon. This is thought to be the first demonstration that sufficient of the vapours of systemic insecticides can be absorbed by the roots of a plant to render the leaves toxic to insects feeding on them.

These results and the physical properties of the insecticides suggest that only insecticides as volatile as phorate and disulfoton can move through dry soil to the roots of plants, and that even in moist soil phorate and disulfoton probably move mainly through the air rather than through the soil water. The more soluble and less volatile dimethoate and menazon are probably absorbed in amounts able to make the foliage toxic to aphids only when they can move to the roots through water.
The movement of 32 phosphorus ‐ labelled dimethoate in the cacao tree, Theobroma cacao L.
Authors: DUNN E. , WARD A. H.
Published: February 2008

The movement and persistence of the systemic insecticide dimethoate and its metabolites in the cacao tree have been studied by the use of radio‐phosphorus in Rogor 40.

In trunk‐injection experiments only 11% of the insecticide entered effectively into the tree and of this 83% remained within 1 ft. of the point of injection. The remainder was quickly translocated upwards but was unevenly distributed in the canopy.

Uptake of dimethoate from soil into the stem and branches proceeded continuously but slowly and was much less than from injections.

In mature pods, over 86% of the dimethoate was found to be degraded into non‐toxic metabolites: thus there is little hazard from dimethoate residues in cacao beans.
The distribution of Myzus persicae (Sulz.) on year‐round chrysanthemums
Authors: WYATT I. J.
Published: February 2008

Four cultivars of chrysanthemum (B.G.A. Tuneful, Giant No. 4 White Indianapolis, Bluechip and Yellow Princess Anne) were infested with Myzus persicae (Sulz.) in an insect‐proof glasshouse. Four weeks of rapid reproduction led to temporary overpopulation, but the mean density was soon regulated to a constant level by the production of alatae. When the density was highest, the same proportion of alatae was produced in all regions of the plants and on all cultivars, regardless of population density at the site of eclosion. This was thought to be due to the rapid state of flux in the entire population.

Pronounced varietal differences developed in the size and distribution of populations, Tuneful supporting six times as many aphids as Princess Anne. Vertical distribution of aphids on the plants differed not only with cultivar, but also according to the population density and the developmental stage of the plant. A complete redistribution occurred as the density stabilized, revealing further varietal characteristics. The youngest leaves were always the most attractive to the aphids, and preference was frequently shown for their upper surface, particularly on Princess Anne.

Short days had little direct effect on the behaviour of the aphids. The induced flowering, however, brought inevitable changes in aphid distribution; populations tended to move upwards towards the flowers, resulting in small, damaged and infested blooms.
The influence of temperature on the spread of aphid‐borne potato virus diseases
Authors: GABRIEL W.
Published: February 2008

Air temperature is one of the most important factors influencing the spread of potato viruses in Poland. High correlations of leaf‐roll infection with accumulated air temperatures for the period I January‐30 April, and of infection with virus Y with accumulated air temperatures for the period 1 January‐10 July were obtained. On this basis the expected areas of different incidence of potato virus diseases were delimited in Poland. The correlation of mean infection for 4 years and mean accumulated temperatures for 15 years was higher than for the particular years, and the proportion of the total variance accounted for by regression exceeded 60%.

The differences in the spread of both the viruses are discussed.
Contrasting effects of resistant and susceptible tomato plants on tomato mosaic virus multiplication
Authors: DAWSON J. R. O.
Published: February 2008

Multiplication of tomato mosaic virus (strain of tobacco mosaic virus) in susceptible and in resistant tomato plants was studied by assaying the infectivity and virus content of sap from non‐inoculated leaves on infected plants. In susceptible plants, infectivity and virus particle number increased rapidly to a maximum at about 14 days after inoculation; leaves produced subsequently contained less virus. In resistant plants, no virus was detected in non‐inoculated leaves until 5 weeks after inoculation. Infectivity then gradually increased at a somewhat higher rate than did numbers of virus particles. The concentration of virus in resistant plants remained lower than in susceptible ones. At first the ratio of infectivity to particle number was larger for samples from the susceptible than the resistant line, but the ratio from the resistant line increased slowly until it eventually equalled that from the susceptible one.

Virus cultured in either of two lines of tomato with different types of resistance invaded healthy plants of either line more readily than virus cultured in the susceptible variety. Resistant lines seem to select self‐invasive new forms of tomato mosaic virus.
The assessment of populations of Thrips nigropilosus Uzel. on pyrethrum
Authors: BULLOCK J. A.
Published: February 2008

A satisfactory method of collecting samples of Thrips nigropilosus was developed in which only the mature leaves were collected, and a number of plants were sampled across several rows of the plot. This give a reproducible and representative estimate of the population within the plot.

Despite the development of this technique, very great differences remained between counts on plots of a Latin square experimental design. The use of covariance analysis considerably reduced the residual variance when populations were increasing arithmetically or at only slightly increased rates. When the increase became more rapid, the value of covariance diminished rapidly while simultaneously positional effects became more significant, suggesting that restraining influences were operating unequally in different parts of the experimental area. It is considered that this phenomenon is widespread in populations of T. nigropilosus and that, as expanding populations are the most likely to be subject to experiment, a more complex design, probably of the incomplete block type, should be used in future.
A comparison of some quantitative methods of extracting small vermiform nematodes from soil
Authors: WHITEHEAD A. G. , HEMMING J. R.
Published: February 2008

When 200 ml. dispersed soil is sedimented from an obliquely rising water current in a simple compartmented tank about three‐quarters of the nematodes are extracted. About 95% of the nematodes in the concentrated suspension can be separated finally from mineral and heavy organic particles by centrifugal notation. When mobile nematodes were finally separated from soil particles by paper tissue, this sedimentation method extracted as many nematodes from sand and loam as Seinhorst's two‐flask and elutriation methods, but in one test extracted fewer Tylenchorhynchus from clay and in another fewer Paratylenchus from clay than the elutriation method. The method is quicker (4 or 6 instead of 30–45 min.) and easier.

Mobile nematodes can be extracted from 300 ml. soil spread out on paper tissue in 23. 33 cm. trays of 8 mesh/cm. phosphor‐bronze gauze, just resting on shallow water. The suspension obtained after 24 hr. at 16–18°C. was concentrated to 10–15 ml. without loss by sedimentation in two tapered cylinders, one of 8 cm. bore, the other of 2.6 cm. bore. This method usually extracted significantly more nematodes than the sedimentation, two‐flask and elutriation methods.
The epidemiology of tomato mosaic IX. Transmission of TMV by birds
Authors: BROADBENT L.
Published: February 2008

House sparrows (Passer domesticus L.), confined in a cage with separate groups of TMV‐infected and healthy tomato plants, infected fifty of the 262 healthy plants by flying between the groups and perching on the plants. None of 191 healthy plants in an adjoining or the same cage without birds was infected. Thus birds could possibly spread TMV within crops and from one crop to another.
Effect of soil amendment with chitin on pea wilt caused by Fusarium oxysporum f. pisi
Authors: BUXTON E. W. , KHALIFA O. , WARD V.
Published: February 2008

Chitin applied to soil naturally infested with F. oxysporum f. pisi greatly lessened the severity of wilt in Onward peas, sown at the time the chitin was applied to the field. In the glasshouse, different pea varieties sown in the field soil 8 months after the chitin was applied were protected equally against infection by any of the three races of the fungus. The severity of wilt decreased with increasing amounts of chitin added to the soil.

Applying chitin to artificially inoculated soil a month before pea seedlings were planted in pots also greatly diminished the severity of wilt.

Adding chitin to soil decreased the population of Fusarium and increased the number of actinomycetes. Many of the actinomycetes were antagonistic towards Fusarium.
Further studies on the effect of aldrin and three other chlorinated hydrocarbons on clubroot of summer cabbage
Authors: CHANNON A. G. , FLINT ANNE E. , HINTON R. A. L.
Published: February 2008

Field tests were made of the four chlorinated hydrocarbon insecticides, aldrin, dieldrin, endrin and telodrin, applied as pre‐planting root dips with a methyl cellulose sticker. None of the treatments controlled the disease as effectively as a root dip in a 10% suspension of pure calomel, but they generally caused less initial growth check, resulting in some instances in significantly higher yields at maturity.

Evidence that dieldrin and endrin had greater activity against clubroot than aldrin and telodrin was obtained in glasshouse experiments. This was confirmed in laboratory tests where it was also shown that the first two chemicals either eliminated or markedly reduced root hair infection of cabbage seedlings at a concentration as low as 0.1 p.p.m.