bluuebunny/crossref_metadata_2025 huggingface dataset:
The relationship between nutrients in extracted xylem sap and the susceptibility of fruit trees to silver‐leaf disease caused by Stereum purpureum (Pers.) Fr.
Authors: BEEVER D. J.
Published: February 2008

Xylem sap was extracted from cut branches of stone‐fruit and pip‐fruit trees at different times of the year, and analysed for nitrogen and carbohydrate content. Growth of Stereum purpureum was measured in the different sap samples in vitro. Nitrogen and carbohydrate levels in xylem sap from peach trees were highest in late winter and early spring, and these samples supported most growth of S. purpureum. At full bloom the levels of nitrogen and carbohydrate in xylem sap from stone‐fruits (peach, nectarine, plum, cherry) were several times greater than in sap from pip‐fruits (apple, pear), and the growth of S. purpureum in sap from stone‐fruits was approximately ten times that in sap from pip‐fruits.

The results suggest that seasonal variations in susceptibility of stone‐fruits to silver‐leaf disease, and the greater susceptibility of stone‐fruits than of pip‐fruits, are due to differential ability of their xylem saps to support growth of S. purpureum.
Decline and other effects of five virus infections on three varieties of plum (Prunus domestica L.)
Authors: POSNETTE A. F. , CROPLEY R.
Published: February 2008

The effects of five different virus inocula on three varieties of plum (Prunus domestica L.) were studied in a field trial of 10 years duration. The viruses causing line pattern, ringspot, prune dwarf and bark split had no effect on the growth of Marjorie's Seedling and Cambridge Gage, and only that causing prune dwarf stunted Oullins Gage trees. However, these viruses diminished the fruit yield of one or more varieties, and prune dwarf virus seriously decreased the yield of all three. Decline disease, probably caused by a strain of Prunus necrotic ringspot virus, developed in Marjorie's Seedling but not in the other varieties. The symptoms first appeared after 5 years and then the trees declined progressively with necrotic ‘incompatibility’ between rootstock and scion.
Identification of viruses isolated from plum trees affected by decline, line‐pattern and ringspot diseases
Authors: SENEVIRATNE S. N. de S. , POSNETTE A. F.
Published: February 2008

Viruses obtained from plum trees infected with either decline, line‐pattern or ringspot diseases were characterized and identified. All the viruses were serologically related to Prunus necrotic ringspot virus (NRSV); those from trees with decline or ringspot were serologically indistinguishable from cherry strains of NRSV but differed in pathogenicity, whereas the virus from trees with line pattern was closely related to apple mosaic virus. When returned from herbaceous hosts to Prunus, line‐pattern and ringspot isolates reproduced symptoms characteristic of the diseased sources. One virus isolate from trees with decline diminished the vigour of young plum trees. Comparison with other investigations shows that at least two unrelated viruses cause plum line‐pattern disease in America and Europe.
Inheritance and effectiveness of genes in barley that condition tolerance to barley yellow dwarf virus
Authors: CATHERALL P. L. , JONES A. T. , HAYES J. D.
Published: February 2008

Tolerance to barley yellow dwarf virus (BYDV) in five Ethiopian barley genotypes was conditioned by major genes which apparently occurred at, or near, the same chromosome locus in each genotype. The genes or alleles differed in effectiveness, one providing a high, three an intermediate and one a low level of tolerance. In plants having a slow rate of growth, the effectiveness of the tolerance genes tended to be masked, but the effectiveness of the gene or allele which provided the highest level of tolerance was masked to a lesser extent than that of genes or alleles providing low or intermediate levels of tolerance.
Field experiments with spring barley resistant to cereal cyst nematode, 1965–1968
Authors: COTTEN J.
Published: February 2008

Two bulk populations of spring barley lines differing in respect of a single dominant gene for cereal cyst nematode (Heterodera avenae) resistance were used in trials over 4 years to assess the effect of the nematode on grain yield. On an infested site the resistant lines consistently and significantly out‐yielded the susceptible lines by an average of 9 % over the 4 years. On non‐infested sites, there was no difference in yield between the resistant and susceptible lines.

To measure changes in the cereal cyst nematode population under continuous barley cultivation, the resistant and susceptible lines were each sown at the infested site on the same plots for 4 consecutive years. The cereal cyst nematode population declined under both susceptible and resistant barley, but more rapidly under the latter. Migratory nematodes, mostly Pratylenchus minyus, were latterly prevalent on all plots.

There was no detectable change in the pathogenicity of the cereal cyst nematode population after 3 years of growing resistant barley.
Aggregation and the transformation of counts of Aphis fabae Scop, on beans
Authors: TAYLOR L. R.
Published: February 2008

In several sets of counts of Aphis fabae colonies on bean stems, obtained with different sampling methods, variance was always proportional to the same power of the mean; s2=amb where b= 1.72 and a differed by different sampling methods. The resulting standard transformation for A. fabae on beans, z=x0 2, is marginally more effective than z= log (x+1).
Effects of population density on alienicolae of Aphis fabae Scop.
Authors: SHAW M. J. P.
Published: February 2008

A technique for rearing aphids in dense populations is described. Apterae were reared in high (‘C’) and low (‘U’) population densities and the proportions of alatae among their progenies were compared. Proportions of alatae were larger among progenies of ‘C’ apterae, and the proportions also increased as the density of the population in which the progenies were reared increased. Progenies of alatae never became alatae.
Epidemiology and control of powdery mildew (Sphaerotheca pannosa) on roses
Authors: PRICE T. V.
Published: February 2008

In examinations between September 1966 and December 1968 of 741 specimens of rose species and cultivars, cleistocarps of Sphaerotheca pannosa were found on thirty‐two cultivars, mostly ramblers and old shrub roses, and on nine of these they were found in two or three successive seasons.

On stem pieces placed on soil in each of the winters 1966‐7, 1967‐8 and 1968‐9 the number of cleistocarps with asci and ascospores decreased during November and December and rose slightly in January, but none showed dehiscence.

Cleistocarps on rose bushes examined during the winters of 1967‐8 and 1968‐9 showed a progressive degeneration of ascospores, and by December none was found.

Perennation of S. pannosa in buds was demonstrated by field observations, by inducing bursting of dormant buds on surface‐sterilized shoots and by dissection of dormant apical buds.

In field studies in 1968 of the development of mildew, infected buds were noted on 22 March but secondary infections did not appear until 17 April, though viable conidia and susceptible leaf tissue were present during this period. Low temperatures appeared to be partly responsible for this lag. On detached leaves in the laboratory the fungus developed from germination to sporulation in 4 days at 20°, 7 days at 15°, 11 days at 10° and 28 days at 3°. Keeping inoculated detached leaves at 0° for 10 days apparently did not affect the viability of the conidia.

In both 1967 and 1968 there were two host growth periods, each culminating in flowering, between May and September; mildew did not develop on the shoots until the second growth phase, then the disease increased logarithmically on shoots and blooms during August and September.

The disease on the shoots was effectively controlled in the field during 1968 by applications of ‘Benlate’ (benomyl) or dinocap, but not by methy‐rimol; these fungicides were less effective in controlling mildew on pedicels.

Laboratory tests showed that ‘Benlate’ inhibited sporulation of S. pannosa by deforming the conidiophores.
The role of the sexual stage in the over‐summering of Erysiphe graminis DC. f.sp. hordei Marchal under semi‐arid conditions
Authors: KOLTIN Y. , KENNETH R.
Published: February 2008

The sexual stage of E. graminis f.sp. hordei was found to be functional in Israel, and adapted to the climate of the region. Cleistothecia serve as the principal, and perhaps the only means for persistence of the pathogen in the host‐less, hot and rainless summer, and induce initial infection on wild and cultivated barleys in late autumn. The cool and rainy weather, which induces germination of seeds of the host in the field, also permits ascospore differentiation and ejection. Details are given of the conditions favouring or delaying cleistothccial maturation during and after the growing season.
Seed treatments with benomyl and other fungicides for the control of Ascochyta pisi on peas
Authors: MAUDE R. B. , KYLE ANN M.
Published: February 2008

In three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl‐1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed‐gave complete control of Ascochyta infection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dressing.
Effects of temperature and rainfall on the incidence of wilt (Verticillium albo‐atrum) in hops
Authors: TALBOYS P. W. , WILSON J. F.
Published: February 2008

Wilt incidence in certain hop cultivars recorded during 15 years of experiments on a plot infested with a virulent strain of V. albo‐atrum, and over shorter periods on various infested farm sites, was studied by multiple regression analysis in relation to rainfall and soil temperature at various periods during the growing season. In the least‐resistant cultivar, Fuggle, the incidence of wilt was always high, and was independent of rainfall and soil temperature. Wilt incidence in other cultivars showed a negative correlation with mean soil temperature at 20 cm for the period mid‐April to late June; no other single or multiple regression was consistently significant. It was concluded that the commonly observed association of high wilt incidence with wet weather in early summer is attributable to low soil temperature rather than to high rainfall.
The effect of weather on the concentration of pollen within sugar‐beet seed crops
Authors: SCOTT R. K.
Published: February 2008

The concentration of pollen in the air within diploid open‐pollinated sugar‐beet seed crops at Broom's Barn Experimental Station increased between 05.00 and 09.00 G.M.T. as relative humidity became less than 90%, was greatest between 09.00 and 11.00, when relative humidity wasc.75%, and gradually decreased towards evening. The average pollen concentration during 24 h periods ranged from 170 to 12400/m3being greatest on fine, windy, dry days after periods of cooler weather. Rain during the morning washed pollen out of the air and damaged developing anthers, but rain in the late afternoon following a sunny morning seemed hardly to affect the pollen catch, while rain at night sometimes caused an immediate temporary increase in pollen concentration. Most pollen was released between 27 June and 31 July in all years (1965‐7); more in the first than in the second half of July. 1965 was cool and damp, 1967 warm and dry, 1966 warm and dry early, and cool and wet late. The total pollen catch in 1965 was 83% and in 1966 31% of that in 1967 but the percentage germination of seed harvested in the 3 years was similar.

The total pollen catch on a trap 230 m east of the 1965 crop was c. 1% of the catch within the crop on days with gusty westerly winds and the catch on a trap c. 46 cm above the 1966 crop averaged 78.6% of that at the level of most flowers.
Breeding for mature‐plant resistance to yellow rust in wheat
Authors: LUPTON F. G. H. , JOHNSON R.
Published: February 2008

In recent years several varieties of wheat, such as Rothwell Perdix and Maris Envoy, have shown good resistance to yellow rust when first produced, but because their resistance was determined by simply inherited major genes, they have later been severely attacked by newly arising physiologic races of the pathogen. Other varieties, such as Little Joss, Atle and Maris Widgeon, though slightly attacked by several races, have never suffered severe damage even when exposed to high levels of inoculum. The inheritance of this non‐race‐specific type of resistance was studied in a cross between Little Joss and a susceptible but shorter‐strawed variety, Nord Desprez. Resistance appeared to be under complex control. It was found possible to select short‐strawed resistant plants, using simple techniques in the field.
Sites of virus retention in the alimentary tract of the nematode vectors, Xiphinema diversicaudatum (Micol.) and X. index (Thorne and Allen)
Authors: TAYLOR C. E. , ROBERTSON W. M.
Published: February 2008

Electron microscopy of thin sections of Xiphinema diversicaudatum and X. index fed on plants infected respectively with arabis mosaic and grapevine fanleaf viruses showed that the viruses are retained as a monolayer of particles adsorbed on to the cuticle lining the lumina of the odontophore (stylet extension), anterior oesophagus and oesophageal bulb. During the moult of the nematode the cuticular lining is shed and together with the detached virus particles is ingested into the intestine through the oesophago‐intestinal valve; this supports the limited experimental evidence that viruses transmitted by X. diversicaudatum and X. index are not retained through the moult.
Bacteriophage and serological methods for the identification of Pseudomonas phaseolicola (Burkh.) Dowson
Authors: TAYLOR J. D.
Published: February 2008

Rapid phage and serological methods were compared with biochemical and bean‐pod inoculation tests for the identification of Pseudomonas phaseolicola. Phages II P, 12 P and 48 P were highly specific and did not lyse any of forty‐five other isolates from bean or the sixteen species of Pseudomonas tested. They were also, however, unable to lyse the rough colony forms of P. phaseolicola which were occasionally isolated. Phage 12 S lysed a wide range of Pseudomonas spp., including a proportion of P. phaseolicola isolates, the majority of which were race 2. Serological tests showed that the heat‐labile antigen possessed by P. phaseolicola was common to twelve other species of plant pathogenic pseudomonads. The heat‐stable antigen was more specific and was detected only in P. mors‐prunorum and P. primulae, neither of which occurs on bean. The two races of P. phaseolicola were indistinguishable in serological tests. It was concluded that both phage and antiserum tests provide specific, rapid and easily applied methods for the routine identification of P. phaseolicola isolates from plant and seed material.
The control of common scab of potatoes by irrigation
Authors: LAPWOOD D. H. , WELLINGS L. W. , ROSSER W. R.
Published: February 2008

Irrigation applied early during tuberization significantly decreased scab on tubers of Majestic, King Edward and Record, but not on Pentland Crown, a resistant cultivar, where tubers had little scab even from the driest soil. There was little benefit from keeping soils wetter than 0.6 in (15.24 mm) soil moisture deficit (S.M.D.) for more than 3 weeks after tuber initiation, and irrigation to 0.8 in (20.32 mm) S.M.D. gave economic control. Irrigating only after the ‘marble stage’ increased yield but the tubers were scabbed. Irrigation did not alter the rate eyes (nodes) separated from the apical bud but speeded the swelling of tubers.
The biology of Peronospora viciae on pea: laboratory experiments on the effects of temperature, relative humidity and light on the production, germination and infectivity of sporangia
Authors: PEGG G. F. , MENCE M. J.
Published: February 2008

Germination of Peronospora viciae sporangia washed off infected leaves varied from 20% to 60%. Sporangia shaken off in the dry state gave 11–19% germination. Most sporangia lost viability within 3 days after being shed, though a few survived at least 5 days. Infected leaves could produce sporangia up to 6 weeks after infection, and sporulating lesions carried viable sporangia for 3 weeks.

Sporangia germinated over the range 1–24 °C, with an optimum between 4 and 8 °C. Light and no effct.

The temperature limits for infection were the same as for germination, but with an optimum between 12 and 20 °C. A minimum leaf‐wetness period of 4h was required, and was independent of temperature over the range 4–24 °C. Maximum infectivity occurred after 6h leaf wetness at temperatures between 8 and 20 °C. Infection occurred equally in continuous light or in darkness.

After an incubation period of 6–10 days sporangia were produced on infected leaves at temperatures between 4 and 24 °C, with an optimum of 12–20 °C. Exposure to temperatures of 20–24 °C for 10 days reduced subsequent sporulation. Sporangia produced at suboptimal temperatures were larger, and at 20 °C. smaller, than those produce at 12–16 °C. Viability was also reduced. No sporangia were produced in continuous light, or at relative humidities below 91%. For maximum sporulaiton an r.h. of 100% was required, following a lower r.h. during incubation.

Oospores wre commonly formed in sporulating lesions, and also where conditons limited or prevented sporulation.

The results are discussed briefly in relaiton to disease development under field conditions.
Distribution of aphids in cereal crops
Authors: DEAN G. J. , LUURING B. B.
Published: February 2008

Cereal crops were examined weekly for aphids during 1969. Plants in twenty samples of row 0.3 m long were examined in a sheltered perimeter of a crop and along a transect 36.6 m into the crop. Aphids were usually first found within 1–4 weeks of the first alatae caught in a suction trap operating 12.2 m above ground. When first alatae caught in a suction trap operating 12.2 m above ground. When the first found from 10 to 27% of the 0.3 m lengths sampled contained aphids.

Rhopalosiphum padi, first found late in May, were scarce (< 0.53/0.3 m) throughout June and July. Sitobium spp. and Metapolophium dirhodum, which appeared in mid‐June, were more numerous than R. padi; most occurred during the second half of July, and populations decreased just before harvest in early August. Sitobium avenae was more abundant (max. 19.3/sample) than either S. fragariae (0.91) or M. dirhodum (2.51).

More aphids occurred in oats (max. 52/0.3 m) during July than in wheat (45), and barley had fewer (6.8). S. avanae was more abundant than M. dirhodum in sheltered areas of barley and wheat, and in exposed areas of the same crop M. dirhodum was commonest. Along sheltered perimeters, the ratio of S. avenae to M. dirhodum was largest in barley (11:1), intermediate in oats (6:1) and smallest in wheat (3.7:1). Sitobium spp. were most numerous on the ears, when most M. dirhodum were on the leaves.

Regression analyses of log. S2 on log. m suggested that S. avenae was more evenly distributed within (36.6 m) the field (b = 1.056 + 0.109) than along the sheltered perimeter (b = 1.432 + 0.132), though it seemed similarly distributed along perimeters of barley, oats and wheat. The distributions of M. dirhodum and Sitobium spp. along sheltered perimeters of all crops were apparently similar.
Preliminary studies of an integrated control programme for cucumber pests and an evaluation of methods of introducing Phytoseiulus persimilis Athias‐Henriot for the control of Tetranychus urticae Koch
Authors: GOULD H. J.
Published: February 2008

Preliminary investigations suggest that, when Phytoseiulus persimilis is used to control Tetranychus urticae, the major pest of cucumbers, the control of other pests and powdery mildew can be effected by means of Encarsia formosa for the control of whitefly (Trialeurodes vaporariorum), bed drenches of gamma‐BHC for thrips control and dimethirimol for the control of cucumber mildew (Erysiphe cichoracearum). The parasite Aphelinus flavipes failed to control an infestation of Aphis gossypii in one trial. A comparison of different methods of introducing Phytoseiulus confirmed that the best results were obtained when an even, artificial infestation of Tetranychus urticae was established on the crop before the introduction of the predator.
The behaviour of populations of potato cyst eelworm Heterodera rostochiensis Woll. Towards resistant potato varieties derived from Solarium tuberosum ssp. andigena Juz & Buk
Authors: BROWN E. B.
Published: February 2008

Many populations of Heterodera rostochiensis mostly from the main potato growing areas of England and Wales, were tested with eelworm‐resistant potato varieties (andigena hybrids). Except in the Eastern Region, where resistant varieties were planted alongside commercial varieties in infested fields, tests were done in pots inoculated with a standard number of cysts extracted from a single soil sample from each field. The tests showed that England and Wales could be divided into areas according to the percentage of cysts(< 10%, 11–70%,> 70%) produced on the resistant compared with a commercial non‐resistant variety. On the peat soils of the East Anglian fens and in Bedfordshire, Essex and Kent (area A) most populations produce few cysts on resistant varieties. In much of the East Midlands and Yorkshire (area D), populations produce many cysts on resistant varieties which behave much as ordinary susceptible potatoes. Populations in the rest of England and Wales (areas B, C) vary and in many districts every field must be tested separately.

If the pathotypes occurring in Britain had separate origins in South America, the present distribution in England and Wales is probably due to chance introductions dispersed with seed and following the patterns of trade in seed potatoes. As all commercial varieties, before the release of eelworm‐resistant ones, were about equally susceptible to the different pathotypes, the varieties themselves probably played little part in determining the present distribution of pathotypes.
Methods for assessing the tolerance and resistance of different types of cocoa to cocoa swollen‐shoot virus
Authors: KENTEN R. H. , LEGG J. T.
Published: February 2008

Different types of cocoa were compared for their resistance to infection and tolerance of infection with the virulent strain A of cocoa swollen‐shoot virus, inoculated either by mealybugs or manually. The method of infection did not affect the ranking of the cocoa types for resistance, except at high percentages of infection, or for tolerance. In comparison with other methods, manual inoculation simplifies the screening of cocoa types for resistance and tolerance to virus infection, and provides a more sensitive test for resistance.
The fumigant effect of metaldehyde on slugs
Authors: HENDERSON I. F.
Published: February 2008

The fumigant effect of metaldehyde on slugs is confirmed and shown almost certainly to be caused by impure metaldehyde breaking down to the volatile parent monomer, acetaldehyde. Acetaldehyde was slightly more toxic to Agriolimax reticulatus than to Arion hortensis.
Changes in the resistance of tobacco leaf to Erysiphe cichoracearum DC. induced by topping, cytokinins and antibiotics*
Authors: COLE J. S. , FERNANDES DESIRÉE L.
Published: February 2008

Treatments that produced different rates of growth in attached tobacco leaves and leaf discs, also affected the growth of powdery mildew on them.

Topping (removal of flower head) increased the resistance of upper leaves, and attached leaves of topped and intact plants were more susceptible than leaf discs from them incubated on water.

Hyphal growth increased on leaf discs incubated on water at increasing light intensities, as did dry and fresh mass of healthy discs. On kinetin, dry and fresh mass also increased with light intensity but hyphal growth decreased slightly. Discs incubated at all light intensities on kinetin had less hyphal growth than those on water at the lowest intensity (< 50 lx).

Floating leaf discs on chloramphenicol at 500 μ/ml restricted fungal growth but not quite as much as kinetin (10 μ/ml); kinetin inhibited the fungus in the presence of chloramphenicol. Actinomycin D (2.μ5 μ/ml) and puromycin (5.0 μml) had little effect on the fungus.
Observations on the infection and rotting of apples var. Bramley's Seedliong by Diaporthe perniciosa
Authors: AYUB A. NAWAWI BIN HOJI , SWINBURNE T. R.
Published: February 2008

In N. Ireland Diaporthe perniciosa March is a common inhabitant of the dead wood of Bramley's Seedling apple trees, and its pycnospores, extruded throughout the growing season, are responsible for fruit infections which result in stalk‐end rots during storage.

Pycnidia were produced in culture only after exposure to light, near‐UV radiation being particularly favourable. The carbon source in the medium influenced pycnidia production: high yields were obtained where mannitol was used. Only a‐spores germinated under the conditions tested, giving optimum germination at 25 d̀C. in a water film. No germination occurred at less than 98% R.H. Germ tubes and hyphae developed appressoria after germination on artificial surfaces but on apple skin most spores produced only a protuberance from which penetration hyphae developed directly. The cuticle and epidermal cells of apples of all ages were penetrated within a few days of inoculation. Intact surfaces and lenticels were penetrated equally. Susceptibility to further rotting increased with age of the fruit. Apples loaded with spores early in the season rotted later than similar apples loaded just before picking. Polygalacturonase was detected in sap expressed from rotted apples of various ages, the level of activity being correlated with the susceptibility of the fruit.
Pathogenic behaviour of Cephalosporium maydis and C. acremonium
Authors: SABET K. A. , ZAHER A. M. , SAMRA A. S. , MANSOUR I. M.
Published: February 2008

Cephalosporium maydis infects young maize plants easily, but as plants age fewer are infected and none after approx. 50 days from sowing. The mesocotyl and seminal, fibrous and adventitious roots are attacked, especially when there is damage or much inoculum. Most penetration occurs where roots are elongating and emerge from the mesocotyl or from fibrous roots. At first the fungus grows superficially on roots, producing hyphae with short, brown, thick‐walled, and swollen cells. After penetrating, the fungus spreads towards the xylem, where it grows slowly at first but after 5 weeks grows faster upwards.

C. acremonium causes black‐bundle disease of maize. It seems to infect plants growing in unfavourable conditions but the details remain uncertain. The percentage of plants infected was not related to the amount of inoculum and the fungus may not be a primary parasite. The sterile culture filtrate of the fungus produces vascular discoloration and wilt of maize seedlings.
Spraying bananas in Fiji to control black leaf streak disease
Authors: FIRMAN I. D. , HOSKIN P.
Published: February 2008

Three sprays, maneb in water applied by hydraulic knapsack sprayer and maneb in an oil/water emulsion or an oil/water emulsion alone applied by mistblower were compared for the control of black leaf streak disease of banana caused by Mycosphaerella sp.

Although there were no differences in yield in the ‘plant’ crop, maneb, especially as a water‐based spray, resulted in much better disease control and leaf survival. Oil seemed to have an adverse effect on fruit quality but not on plant growth.

Since it is unlikely that oil alone will adequately control the disease in ratoon crops fungicides may be necessary.
The effects of soil sterilants on the cereal cyst‐nematode (Heterodera avenae Woll.), take‐all (Ophiobolus graminis Sacc.) and yields of spring wheat and barley
Authors: WILLIAMS T. D. , SALT G. A.
Published: February 2008

In a 3‐year field experiment on sandy loam at Woburn, methyl bromide, chloropicrin, D‐D mixture, dazomet, formalin and mercury salts were applied in the first year only, or in the first and second years, before drilling spring wheat. In the third year, their residual effects on spring barley were measured. All sterilants except mercury decreased cereal cyst‐nematode (Heterodera avenae) numbers and take‐all (Ophiobolus graminis) incidence, and increased crop yields in the year they were applied. Dazomet gave the best control of H. avenae in the first year and controlled O. graminis best in both years of application. In the third year, O. graminis increased in all plots previously treated (except after two successive D‐D treatments), but H. avenae increased only after formalin. Two formalin applications more than trebled the H. avenae egg count by the end of the third year and depressed the yield of barley. Two successive applications of chloropicrin gave the best nematode control.

Other fungus diseases, Fusarium foot rot, Pythium root rot, eye‐spot (Cercosporella herpotrichoides Fron.) and sharp eye spot (Rhizoctonia solani Kühn), were uncommon and sterilants had no detectable effects on them. The largest aggregate straw yield (3‐year total) was obtained from two applications of dazomet, but the best yields after treatment in the first year only were given by D‐D and methyl bromide.
Observations on the effects of distribution and numbers of slug pellets on the catch of slugs
Authors: WEBLEY D.
Published: February 2008

Thirty comparisons were made of the catch of different numbers of slug pellets and the effect of meteorological factors on them. Ten pellets/2 1/2 ft (0.75 m) gave the greatest catch although, economically, the best treatment was from two to five pellets for Agriolimax reticulatus; for Arion hortensis and Milax budapestensis the return per pellet was low. Throughout the year only 16.6% of the catch variance was removed by meteorological factors.
Seasonal and geographical variation of powdery mildew on susceptible cereal cultivars, 1958‐68
Authors: DOLING D. A. , SAUNDERS P. J. W. , DOODSON J. K.
Published: February 2008

Annual patterns of mildew on winter and spring barley, wheat and oats at NIAB trial sites for 1958‐68 are reported. High intensities of mildew were preceded by early infections, particularly at sites where both winter and spring crops were infected early. Relative earliness and severity of infections in all six crops of cereals were generally similar at any site. This pattern was repeated within denned mildew ‘regions’, i.e. north, east and west. Sprowston (Norfolk) was atypical of the eastern sites, showing patterns of mildew infection more characteristic of sites in the west, where mildew values were 50 % higher than elsewhere.

Dates of first visible infection became later further eastwards and northwards, particularly in winter cereals. This suggested the possibility of dispersal of inoculum by prevailing winds to the north, north‐east and east, or a similar progression in climatic factors favourable to mildew development.

Estimates of loss of potential yield in the trial plots of sites in each region and over the whole country were calculated for winter wheat, spring barley and spring oats using the formulae of Large and Doling, for which supplementary confirmation was provided.
Pre‐selection for Phytophthora cactorum (Leb. &Cohn) Sehroet. resistance in apple seedlings
Authors: WATKINS R. , WERTS JULIE M.
Published: February 2008

Inoculation of apple seedlings at the two‐leaf stage with a Phytophthora cactorum zoospore suspension provided a rapid method of pre‐selecting for collar rot resistance, since the susceptible plants died within 2 weeks of inoculation while the resistant plants continued to grow satisfactorily. The presence of the resistance gene Pc was not alone sufficient to explain the observed segregation.
Quantitative isolation of Verticillium spp. from soil and moribund potato haulm
Authors: ISAAC I. , FLETCHER P. , HARRISON J. A. C.
Published: February 2008

A technique to isolate a high proportion of the propagules of important Verticillium spp. from soils is described with modifications for quantitatively distinguishing between the microsclerotial and conidial fractions of V. dahliae and estimating the microsclerotial population and its viability in dried potato stems.

In pots, soil populations of V. dahliae with less than c. 40 propagules/g failed to induce disease in potato plants; with larger populations there was some relation between disease severity and fungal population. In soils artificially infested with V. dahliae (c. 50000 propagules/g dried soil) the viable population decreased within 6 months to c. 100 propagules/g and then remained stable for more than a year. From fields in South Wales and East Anglia large populations of V. nigrescens and V. lateritium and small populations of V. dahliae were obtained.
Association between the potato cyst‐nematode, Heterodera rostochiensis Woll., and Verticillium dahliae Kleb. in the early‐dying disease of potatoes
Authors: HARRISON J. A. C.
Published: February 2008

Investigation of a possible association between Verticillium dahliae and H. rostochiensis (pathotype E, British notation) was based on field observations and an examination of disease development in single‐stemmed potato plants grown in pots. An association was found in the distribution of the nematode and the fungus in the field, and the disease was far more severe with a combined infection than with either pathogen alone. Studies on leaf‐area development and yield reduction suggest there is synergism between fungus and nematode, the reductions produced by the combined infection exceeding the sum of those produced by either pathogen alone. Fungal mycelium and the extent of host colonization by V. dahliae were greatly increased by the presence of the nematode. The possible benefits to V. dahliae in the fungus‐nematode complex are discussed.
Serological relationships of some viruses from cocoa (Theobroma cacao L.) in Ghana
Authors: KENTEN R. H. , LEGG J. T.
Published: February 2008

Strains A and Anibil of cocoa swollen‐shoot virus are serologically closely related. They are more distantly related to strain M and cocoa mottle‐leaf virus (Kpeve isolate), which are distantly related to one another. Strains A and Anibil protected against one another in cocoa seedlings, but no protection was found with any other combination between these four virus isolates. All mealybug‐transmitted cocoa viruses in West Africa are probably best considered as strains of cocoa swollen‐shoot virus.
Testing the effects of liquid eradicants on emergence of Anobium punctatum (Deg.)
Authors: TAYLOR JEAN M.
Published: February 2008

A laboratory method is described for evaluating the effectiveness of insecticides in preventing the emergence of furniture beetles (Anobium punctatum (Deg.)). Composite blocks of Scots pine were prepared consisting of an untreated core containing larvae and two treated outer veneers from which all solvent had evaporated and through which beetles had to emerge.

Dieldrin and gamma‐BHC prevented emergence of beetles, dieldrin being the more effective material. The following did not prevent emergence at the concentrations tested: pentachlorophenol, zinc naphthenate, polychlor‐naphthalene, copper‐chrome‐arsenate, tri‐butyltin oxide.
The toxicity of some soil‐applied systemic insecticides to Aphis gossypii (Horn. Aphididae) and Phytoseiulus persimilis (Acarina: Phytoseiidae) on cucumbers
Authors: BINNS E. S.
Published: February 2008

Tests with potted cucumber plants confirmed that granular or soil drench treatments applied against Aphis gossypii Glover may limit the performance of a predaceous species introduced to control another pest. Soil applications of thionazin, methomyl, demeton‐S‐methyl and aldicarb in equal amounts caused deaths, in descending order of toxicity, of the predatory mite Phytoseiulus persimilis Athias‐Henriot. This effect was not demonstrated for pirimicarb, menazon or isolan on whole plants at rates up to 10 mg a.i. nor in laboratory tests on detached plant portions. Methomyl and thionazin, but not aldicarb, were relatively more toxic to P. persimilis than to its prey, Tetranychus urticae Koch. Some survival of P. persimilis occurred on plants treated with demeton‐S‐methyl, but this material was inferior to pirimicarb in both selectivity and persistence. Pirimicarb offers practical control of A. gossypii on cropping cucumbers, without phytoxicity or residues, when applied at 125 mg a.i./plant. It is therefore preferable to other aphicides for use on cucumbers during propagation or cropping, especially where the favoured means of control of T. urticae is by introductions of P. persimilis. Qualitative evidence of in vitro tests suggested that those systemic materials which affect P. persimilis do so by ‘food‐chain’ toxicity, but that vaporization from the leaf may also be a factor.
Effects of soil fumigation on soil nitrogen and on disease incidence in winter wheat
Authors: EBBELS D. L.
Published: February 2008

Winter wheat was grown in soil fumigated with D‐D, 85% dazomet dust or formalin, and top‐dressed with o or 125 kg nitrogen/ha. Six weeks after fumigation, there was much more ammonium nitrogen in fumigated than in unfumigated soil. Nitrate was also more after fumigation with dazomet, but less after D‐D and formalin. After 5 months, only D‐D plots had less nitrate and more total mineral nitrogen than unfumigated plots.

Take‐all (Ophiobolus graminis) was less prevalent in the first crop after dazomet or formalin, but was more prevalent in the second crop than after other treatments. Eyespot (Cercosporella herpotrichoides) was decreased only by formalin and only in the first crop after applying it. Fumigation had little effect on the incidence of other diseases recorded or on grain yield, except that yields were light on D‐D plots in the first crop after fumigation, when ears were severely deformed.
Reproduction of Lumbricillus rivalis (Levinsen) in laboratory cultures and in decaying seaweed
Authors: KIRK R. G.
Published: February 2008

The cocoon production of 144 Lumbricillus rivalis cultured in pairs at 10 ± 1 °C was high over the first 2 weeks of breeding activity and then declined, chiefly because of high mortality. Cocoon deposition lasted for between 1 and 16 weeks, eight pairs of worms producing cocoons for 9 weeks and one pair for 16 weeks. During the total period of cocoon deposition over 9000 eggs (mean 17·4 per cocoon) were deposited.

Two decaying wrack bed populations of L. rivalis showed a low level of cocoon and egg production in autumn, rising to an annual maximum in late winter/early spring. In these populations the mean egg content varied seasonally from 17·1 to 47·8 eggs per cocoon.

When cocoons in the laboratory were transferred from the site of deposition to incubation dishes 31% hatched, but those left in the substrate showed a 92% hatch. In the naturally occurring populations 19% of the cocoons detached from seaweed fronds hatched, but 62% of those left in situ.

Eggs and worm embryos developed to relatively late stages in most cocoons, whatever the rate of hatching; development often continued for up to 2 months after deposition without hatching.

Over 50% of the fertile eggs in cocoons from decaying wrack hatched and developed to 5 mm worms.
Some hosts and properties of dahlia mosaic virus
Authors: BRUNT A. A.
Published: February 2008

Dahlia mosaic virus (DMV) infected twenty‐five of the eighty‐five plant species from four of eighteen families inoculated, but only dahlias were found naturally infected. DMV infected fourteen members of the Solanaceae, Amaranthaceae and Chenopodiaceae, and eleven of twenty‐nine Compositae. Verbesina encelioides was the best plant for diagnosis, assay and source of virus. Systemically infected hosts contained ovoid intracellular inclusions 2–5–10 μm in diameter which were shown by electron microscopy to consist of a finely granular, vacuolated matrix containing numerous virus particles. V. encelioides sap was sometimes infective after dilution to 1/2000 but not 1/3000, after heating for 10 min to 75 °C but not 80 °C, and after 4 days at 18 °C or 32 days at 2 °C. Sap from infected dahlia, Zinnia elegans or Ageratum houstonianum rapidly became non‐infective, but extracts made with 0·05 M sodium thioglycollate or 0·03 M sodium diethyldithiocarbamate remained infective for 24–48 h at 18 °C. Some purified preparations remained infective for up to 3 years at 2 °C.

DMV was best purified from V. encelioides by one or more cycles of differential centrifugation, followed by density‐gradient centrifugation and further concentration. Composition, molarity, and pH of the extracting buffer had little effect on yield of virus. Best yields were obtained from extracts stored with 8‐5% (v/v) n‐butanol at 2 °C for 10–14 days. Purified preparations were infective at dilutions up to 1/5000, had ultraviolet absorption spectra typical of a nucleoprotein (Å 260/280 = 1·47), probably contained DNA, and had a single sedimenting component having isometric particles c. 50 nm in diameter with a sedimentation coefficient of 254 S. The cryptogram of DMV is (D)/*:*/(16):S/S:S/Ap.

DMV is serologically closely related to cauliflower mosaic virus, but the viruses are distinct pathogens. The two viruses have similar properties, size, shape and other characteristics, and together with at least three others form a small but apparently homogeneous group of aphid‐borne viruses.
Field experiments on the resistance of cocoa to cocoa swollen‐shoot virus
Authors: LEGG J. T. , KENTEN R. H.
Published: February 2008

Progenies from crosses between different Upper Amazon cocoa types and between Upper Amazon and Amelonado were compared for their field resistance to infection with cocoa swollen‐shoot virus (CSSV) virulent strain A. Among the intra‐Amazon progenies, those from crosses of Scavina, Iquitos and Nanay groups showed most resistance. Progenies from crosses within these groups may have sufficient resistance to be of immediate practical value in reducing crop losses in areas where CSSV is widespread. Some Nanay progenies were more resistant than others and this provides scope for improvement by breeding. Progeny of crosses between Upper Amazon and Amelonado parents were less resistant than those from intra‐Amazon crosses.

The present results confirm those previously obtained in gauze‐house tests on young plants.
Effects of light and temperature on symptom development and virus content of tobacco leaves inoculated with potato mop‐top virus
Authors: HARRISON B. D. , JONES R. A. C.
Published: February 2008

Necrotic spots or small rings develop after 3–4 days in leaves of Nicotiana tabacum cv. Xanthi‐nc inoculated with potato mop‐top virus and kept at 14 °C in continuous light (4320 lux); a series of concentric necrotic rings of increasing diameter then form at 2‐ to 3‐day intervals around each initial lesion. Successive rings take longer to appear when either the light intensity or the photoperiod is decreased. Virus accumulation is much decreased and lesions rarely develop either at 14· in darkness or at 22° in light. Virus accumulates rapidly when plants are transferred from these conditions to 14° in light (4320 lux), and necrotic spots or rings develop whose size depends on the interval between inoculation and transfer, and on the conditions during this period. In such plants, necrosis seems to occur only when conditions become favourable for virus synthesis, it is confined to recently infected cells and it does not prevent virus spread to further healthy cells. From the sizes of the necrotic rings, the virus is estimated to invade tissue in light (4320 lux) at c. 38 μm/h at 22° and c. 16 μm/h at 14°. Invasion in darkness at either temperature is very slow.

Necrotic rings develop, and the rate of virus accumulation increases when inoculated plants are transferred from 22° in light (4320 lux) to 14° in darkness, but no lesions appear when the order of the treatments is reversed. The process of lesion formation thus includes an early phase requiring light and a later phase requiring low temperature. The light‐requiring phase takes about a day at 14° but less at 22°. The later phase takes about 2 days in light (4320 lux) or 3 days in darkness.
Mycoplasma‐like bodies associated with Rubus stunt disease
Authors: MURANT A. F. , ROBERTS I. M.
Published: February 2008

Mycoplasma‐like bodies were found by electron microscopy in the sieve tubes of blackberry, loganberry and raspberry plants showing symptoms of Rubus stunt disease, but not in those of normal plants. Watering diseased blackberry plants with aureomycin caused remission of the symptoms and greatly decreased the number of mycoplasma‐like bodies.
Studies on plant growth‐regulating substances
Authors: HARPER D. B. , WAIN R. L.
Published: February 2008

The metabolism of certain 2,6‐disubstituted phenols that possess high auxin activity in the pea segment, pea curvature and tomato‐leaf epinasty tests, but are much less active in the wheat cylinder test, has been investigated in wheat, pea and tomato tissue. Metabolites were identified by thin‐layer chromatography and a semi‐quantitative assay method was developed.

The low activity of 2,6‐dihalogenophenols and inactivity of 2‐halogeno‐6‐nitro‐phenols and 3‐halogeno‐2‐hydroxybenzonitriles in the wheat cylinder test was caused by rapid metabolic conversion of the compounds in this tissue to inactive compounds by a process involving hydroxylation of the aromatic ring in the para‐ position. No such inactivation occurred in pea and tomato tissues.

Evidence for a novel detoxification of nitrophenols within both pea and wheat tissue was obtained; 2‐bromo–6‐nitrophenol was converted via 2‐bromo‐6‐aminophenol to N‐acetyl‐2‐bromo‐6‐aminophenol.

Certain 3‐halogeno‐2‐hydroxybenzaldehydes and corresponding aceto‐phenones, although fulfilling the necessary structural and electronic criteria for auxin activity, are inactive. Metabolic studies indicate that this is because they are metabolized in wheat, pea and tomato tissues to compounds not possessing the structural requirements for auxin activity.
The effect of sowing date on adult plant resistance to Erysiphe graminis f.sp. avenae in oats
Authors: JONES I. T. , HAYES J. D.
Published: February 2008

A technique developed for detecting small differences in mildew infection under glasshouse/laboratory conditions is described. A satisfactory correlation was found between results obtained by this method and infections in the field.

Detailed examination of the levels of infection in cultivars Maldwyn and Milford showed that the upper and more recently developed leaves of Maldwyn had a significantly smaller area infected than those of Milford, although seedling leaves of both genotypes were very susceptible. This was most marked when plants were in the 6‐ to 7‐leaf stage.

Comparison of host plants sown on successive dates during the spring and early summer showed that with the acceleration of the rate of growth occurring in later‐sown plants, resistance was expressed progressively earlier in the life of the plant.

Newly expanded leaves which show very low level of infection at the 6‐ to 7‐leaf stage become susceptible as they age, resistance being then expressed in the younger leaves.