bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of high‐pressure sodium discharge lamps as an aid to obtaining clubroot infection
Authors: BUCZACKI S. T.
Published: February 2008

A high‐pressure sodium discharge lamp was more effective than a high‐pressure mercury discharge lamp of identical wattage in stimulating the production of clubroot symptoms on cabbage seedlings growing in infested soil in a glasshouse. Although the maximum total radiation from the sodium lamp was 3*2 times that from the mercury lamp, the differential effects were also observed on plants subjected to identical radiation from either lamp. It was considered that high‐pressure sodium discharge lamps could be a valuable aid to clubroot experiments made in glasshouses during the winter months or under conditions with restricted global radiation such as controlled‐environ‐ment cabinets.
Use of the plant growth regulator chlormequat chloride to control the aphid Hyperomyzus lactucae on black currants
Authors: SINGER M. C. , SMITH B. D.
Published: February 2008

A single application of chlormequat chloride at 2500 ppm reduced the density of Hyperomyzus lactucae on black currants below that at which damage was caused. This treatment had no short‐term effects on the aphid predators present, but did affect interactions between the aphids, their host and the predators. There were no effects on yield in the year of the experiment, but in the following year bushes which had been treated gave considerably higher yields. This increase was attributed both to direct action of the chlormequat chloride and to indirect effects through the reduction of aphid density. Prospects for the use of plant growth regulators as dual‐function compounds in integrated control programmes are discussed.
Stemphylium botryosum f. lactucae‐ its developmentjn vifro and its pathogenicity to lettuce leaves
Authors: SIVAN J. , BARKAI‐GOLAN R.
Published: February 2008

Stemphylium botryosum f. lactucae, incitant of a leaf‐spot disease of stored lettuce, was found to be relatively restricted in its host range. Cross‐inoculations with spore suspension of this fungus failed to induce symptoms in any of the host plants tested, except carrot. Among isolates of S. botryosum from various hosts, only the isolate from carrot induced slight symptoms on lettuce.

While mycelial growth of the lettuce isolate was confined to the range 13–37 oC spores germinated at more extreme temperatures. The optimum temperature for germination and for radial growth on PDA was found to be between 25 and 30 oC. Wet spores were quickly inactivated at 50 oC, whereas more than 40 % of dry spores withstood a 24 h exposure to that temperature.

Only the outer leaves of lettuce responded readily to inoculation with a spore suspension, the required incubation period being 3 days at 25 oC. Symptoms developed less readily on bruised leaves. Relative humidity approaching saturation was necessary for prompt and typical infection, notably during the 24 h following inoculation. Short dry periods (60 % r.h.) interposed at a later stage, while somewhat inhibitory, did not prevent infection.
The behaviour of Bretnia lactucae on cultivars of Lactuca sativa and on other composites
Authors: CRUTE I. R. , DICKINSON C. H.
Published: February 2008

The spores of an isolate of Bremia lactucae obtained from lettuce germinated equally well on Cellophane and on the surfaces of all plant species inoculated. The fungus penetrated the epidermal cells of both host and non‐host plants but extensively invaded only certain lettuce cultivars. Many of the species and cultivars inoculated showed no macroscopic symptoms but exhibited a hypersensitive response to invasion that was limited to a few cells and only visible microscopically. However, the hypersensitive response was not always so limited and in some species, fungal development and associated host cell necrosis was more extensive and visible macroscopically. In such instances, limited sporulation occasionally occurred. On some lettuce cultivars symptoms developed more slowly than on fully susceptible ones and less seedlings became diseased. This was due to the heterogeneity of the inoculum with respect to its ability to overcome certain race specific resistance genes. Such cultivars reacted hypersensitively to the majority, but not all, of the fungal propagules applied and the observed effect was thus due to a lower effective inoculum concentration. Without due care, both these types of ‘intermediate’ reaction could easily be misinterpreted as race non‐specific resistance particularly under field conditions. These observations emphasized the problems of categorizing cultivars and species rigidly as resistant or susceptible when inoculum could be heterogenous or when resistance reactions allowed some macroscopic symptom development.
Development of powdery mildew on leaves of several barley varieties at different growth stages
Authors: RUSSELL G. E. , ANDREWS CHRISTINE R. , BISHOP C. D.
Published: February 2008

On detached leaves and intact plants of several barley varieties at different growth stages, lower percentages of germinated conidia of Erysiphe graminis f.sp. hordei penetrated the host and initiated infection on the abaxial than adaxial surface. More and larger E. graminis colonies developed on the adaxial surface and these comprised more densely packed hyphae and produced more conidiophores than did colonies on the abaxial surface. These results are consistent with the observation that there is usually more powdery mildew on the adaxial than abaxial surface of barley leaves in the field.

Smaller proportions of germinated E. graminis conidia penetrated and infected the host on leaves of adult or near‐adult plants than on those of seedlings or juvenile plants. Older plants also supported fewer, smaller and less dense colonies with less sporulation than young plants. The effects of growth stage of the host plant on development of powdery mildew were much greater in some barley varieties, and with some E. graminis isolates, than others.
Effects of mildew (Erysiphe graminis) on green leaf area of Zephyr spring barley, 1973
Authors: JENKYN J. F.
Published: February 2008

A single spray of tridemorph on 1 June almost doubled leaf area index of Zephyr barley during much of the second half of June. Increases in leaf area duration before ear emergence seemed important in these plots, because they yielded much better than plots sprayed on 11 June although differing little from them in leaf area duration after ear emergence.
The incidence of rosette disease in groundnut in relation to plant density and its effect on yield
Authors: DAVIES J. C.
Published: February 2008

Trials are described in which the relationships between plant density, rosette disease incidence and the yield and quality of groundnuts were investigated on sprayed and unsprayed groundnut plants.

During growth, the number and percentage of sprayed and unsprayed plants showing symptoms of rosette disease was significantly greater at low plant populations than at high. At harvest, in general on unsprayed plots the numbers attacked were also greater at low plant populations, but on the sprayed plots the results were inconsistent. The percentage attack at harvest was much lower on sprayed plots at all plant populations.

Menazon used as a seed dressing did not affect the incidence of the disease but used as a spray it significantly reduced the amount of disease found. The spray was applied at a rate of 294 g a.i./ha, four times at 10‐day intervals, the first spray being applied 10 days from germination. Spraying controlled secondary spread of the virus within the crop and appeared to reduce the severity of early attack. There was a marked improvement of yields and quality of nuts from sprayed plots. Plant density did not affect quality of the groundnuts obtained, but yields per ha were highest on both sprayed and unsprayed plots at the highest plant densities (seed rate up to 134 kg/ha).
Purification and properties of sweet potato mild mottle, a white‐fly borne virus from sweet potato(Ipomoea batatas) in East Africa
Authors: HOLLINGS M. , STONE OLWEN M. , BOCK K. R.
Published: February 2008

A virus obtained from sweet potatoes in Kenya, Uganda and Tanzania was transmitted by inoculation of sap and by whiteflies (Bemisia tabaci). It infected forty‐five of 119 plant species in fourteen of thirty‐six plant families. It was propagated in Nicotiana glutinosa and N. tabacum, in which diagnostic symptoms of vein clearing, leaf curling and distortion developed. Cheno‐podium quinoa was a good local lesion host.

Different seedling lines of sweet potato differed greatly in their susceptibility to infection and in symptoms produced; some developed leaf mottling and were stunted, some were symptomless, and some appeared immune.

The virus was transmitted by dodder (Cuscuta campestris) but not by aphids, or through seed of Ipomoea nil or N. clevelandii. Sweet potato sap contained strong inhibitors of infection, and a low concentration of virus.

Virus‐free cuttings of sweet potato were obtained by thermotherapy (4–5 wk at 35 °C), or by meristem‐tip culture.

The virus remained infective in sap of N. tabacum after dilution to 10‐3, or after 10 min at 55 °C (but not 60 °C), 3 but not 7 days at 18 °C, or 42 but not 49 days at 2 °C. Infectivity was abolished by sonication or u.v. irradiation, by 2% formaldehyde or 2% tri‐sodium orthophosphate, and was greatly decreased by 20 % CHC13 or 20 % ether.

Purified virus preparations were obtained from N. tabacum by clarifying phosphate buffer extracts with n‐butanol, virus precipitation with polyethylene glycol, and differential centrifugation. The virus sedimented as one band in density gradients, and produced a single sedimenting boundary in analytical centrifugation (s°20, w = 1555)‐ It contained one polypeptide species of mol wt 37700, and preliminary digestion experiments suggested a single‐stranded RNA.

Antisera prepared against the virus reacted specifically in precipitin tube tests with titres of 1/16384, but no serological relationships could be found between the virus and fourteen viruses of the potato virus Y group.

Electron micrographs showed straight, filamentous particles c. 950 nm long when mounted in MgCla, but 800–900 nra long in EDTA. The present cryptogram is: (R/i):*/*:E/E:S/Al. This virus is probably the same as Sheffield's virus B.
Eradication of apple powdery mildew (Podosphaera leucotricha) with dormant season sprays of surface‐active agents
Authors: HISLOP E. C. , CLIFFORD D. R.
Published: February 2008

selection of surfactants (5%, w/v, a.i.) representative of the three main ionic types eradicated Podosphaera leucotricha from buds on dormant apple trees, cvs Cox's Orange Pippin, Jonathan and Michelin.

The pathogen was apparently killed without undue damage to buds, although a phytotoxic response in the form of staining of vascular tissue and some crop reductions were observed. Treatments applied with hand lances were equally effective at reducing infections of vegetative buds on terminals, on non‐flowering spurs and flower buds. Indication of a positive correlation between the eradication of mildew from Cox's Orange Pippin trees and an increase in the incidence of apple canker (Nectria galligena) was found at Long Ashton, but this effect was negligible at sites in the West Midlands region.

Efficacy of active formulations was reduced by rain soon after application or by a reduction in the concentration of applied material. Applications with a mist‐blower were effective on the cv. Cox's Orange Pippin, but less so on the cv. Jonathan, while on both cultivars efficacy of a spray containing 5 % a.i. decreased in the order 2240:1120:560 1/ha.

Anti‐mildew activity was not associated with any particular chemical or ionic type of surfactant, and there was an indication that eradicant activity of alkyl phenol ethoxylates was related to their HLB value.

The ecological and economic implications of the use of surfactants as fungicides are discussed.
Studies on plant growth‐regulating substances. XL. 2‐Chloro‐3‐phenylpropionitriles
Authors: KEMP M. S. , WAIN R. L.
Published: February 2008

The complete series of chloro‐, dichloro‐, methyl‐, dimethyl‐ and chloro‐methyl‐ring substituted 2‐chloro‐3‐phenylpropionitriles and several related compounds have been prepared. Their auxin activities have been assessed in the wheat coleoptile, pea segment and pea curvature tests, and the results, which are discussed in relation to molecular structure, support the suggestion by other workers that the observed activity is due to rapid uptake of the nitriles by the plant tissues, followed by metabolism to the corresponding phenylacetic acid.

The high growth promoting activity of 2‐chloro‐3‐(3‐chloro‐2‐methyl‐phenyl)propionitrile (orthonil) is confirmed but 2‐chloro‐3‐(2,3‐dichloro‐phenyl)propionitrile and 2‐chloro‐3‐(2,3‐dichlorophenyl)butyronitrile are shown to be the most active members of the series.
The effect of plant density on populations of the cabbage root fly on four cruciferous crops
Authors: FINCH S. , SKINNER G. , FREEMAN G. H.
Published: February 2008

To study the effects of plant density on populations of the cabbage root fly (Erioischia brassicae), cabbage, cauliflower, Brussels sprout and swede were each planted in plots with twenty‐four concentric circles of plants at spacings ranging from 10 to 90 cm between the individual plants. Plants treated with a root drench of chlorfenvinphos and untreated plants were each sampled at ten plant densities which ranged from 1–5 to 68‐3 plants/m2.

In the absence of insecticide, the numbers of overwintering cabbage root fly pupae produced ranged from c. four per m2 at the lowest plant density to 200 per m2 at the highest. The number of pupae per m2 was proportional to plant density to the powers 0–98,0‐77,0–69 and o‐6i for the swede, cauliflower, cabbage and Brussels sprout crops, respectively. The magnitude of each cabbage root fly population was determined mainly by plant density but also by the cultivar used as host plant.

The results suggested that, in a given locality, when changing from low to high plant density crops during a growing season it should be unnecessary to apply insecticide to control cabbage root fly; conversely, a change from high to low plant densities would necessitate an extremely efficient application of insecticide.
A seedling method for measuring the susceptibility of wheat cultivars to Pucdnia striiformis
Authors: PRIESTLEY R. H. , DOLING D. A.
Published: February 2008

The Wycombe seedling method for measuring the susceptibility of wheat cultivars to physiologic races of Puccinia striiformis involves determining the percentage of seedlings bearing uredosori at a fixed time after inoculation under controlled environment conditions. Each cultivar is classified statistically as either vertically or horizontally susceptible and this classification is utilized in expressing the susceptibility of each to a number of races as a single value.

The method has been used for three years to evaluate wheat cultivars and examples of significant differences in susceptibility between cultivars are given.

A highly significant correlation has been established between data collected using the Wycombe seedling method and field data from physiologic race test beds.
Properties and relationships of broad bean stain virus and Echtes Ackerbohnenmosaik‐Virus
Authors: JONES A. T. , BARKER H.
Published: February 2008

The sedimentation coefficients (s020, w) of the two sedimenting nucleoprotein components of broad bean stain virus (BBSV) were 92 S and 113 S, and of Echtes Ackerbohnenmosaik‐Virus (EAMV) were 93 S and 114 S. Particles from each of these sedimenting components contained a single RNA species and two polypeptides. Estimates of the molecular weights of these constituents obtained by electrophoresis in polyacrylamide gels were: 42000 and 22200 (BBSV) and 41400 and 21800 (EAMV) for the polypeptides; and 2–64 and 1·62 × 106 (BBSV) and 271 and 175 × 106 (EAMV) for the RNAs. In mixtures, the protein and RNA components of BBSV and EAMV were indistinguishable from those obtained from particles of the yellow strain of cowpea mosaic virus.

In freshly made virus preparations each of the sedimenting components of BBSV contained two, and those of EAMV contained three electrophoretic components. After storage for 7–10 days, BBSV preparations contained only the component migrating fastest towards the anode.

Both BBSV and EAMV are distantly related serologically to cowpea mosaic but, whereas BBSV reacted only with antiserum to the severe strain, EAMV reacted only with antiserum to the yellow strain.
Effects of daylength and day/night temperatures on growth and seed yield of cowpea cv. K 2809 grown in controlled environments
Authors: HUXLEY P. A. , SUMMERFIELD R. J.
Published: February 2008

The effects of climatic factors on the growth, reproductive development and seed yield of cowpea (cv. K 2809) were investigated in controlled environment cabinets. Plants were grown to maturity in eight environments comprising all combinations of two day lengths (11 h 40 min and 13 h 20 min), two day (27 and 33 oC) and two night (19 and 24 oC) temperatures. The plants were nodulated (Rhizobium strain CB 756) and received 197 ppm N throughout growth.

Treatments changed the time to the appearance of first flowers by a maximum of 6 days but the later‐flowering plants more than doubled their dry weight during this period, so that effects on plant form and, ultimately, seed production were considerable. Warm nights (24 oC) not only hastened the onset of flowering but also enhanced dry matter production during the pre‐flowering period; they did not extend the total growing period. Warm days (33 oC) did not enhance dry matter production but shortened the duration of the growing period by an average of 21 days (20%).

Variation in final seed yield was mainly due to differences in the number of pods borne on branches. Warm days markedly decreased the number of pods per plant (an overall average reduction of 49%) as did warm nights in conjunction with the long (13 h 20) daylength.

The number of seeds per pod was effected only by daylength (8.3 and 7.6 seeds in the long and short daylengths, respectively). Mean seed weight was decreased by 19% in warm as compared to cool nights but was increased by 18% in warm as compared to cool days.

These responses are compared with those obtained with soyabean cv. TK5 in a previous experiment and are shown, in general, to be similar.
Studies on nodulated and mycorrhizal peanuts
Authors: DAFT M. J. , EL‐GIAHMI A. A.
Published: February 2008

Yields of fruits, plant size and chemical content of shoots, roots and seeds were higher in peanuts infected with Glomus mosseae. Infection with Glomus and Rhizobium stimulated nodulation and acetylene reduction rates. Dually infected plants given various phosphorus treatments, produced more fruits, dry matter, and nodules and contained more phosphorus and nitrogen compared with nodulated‐only plants. Mycorrhizal infections were high in all treatments. Together these two endophytes contributed greatly to the vigour of the host.
Effect of different soil and nitrogen fertilizer conditions on 32P‐labelled phosphate uptake by two grass species
Authors: HUGHES D. M. , GOODMAN P. J.
Published: February 2008

In two years of trials, roots of ryegrass took up more 32P‐labelled phosphate than roots of fescue. Application of 672 kg N ha‐1 increased phosphate absorption compared with application of 112 kg N ha‐1. Roots in mineral soil absorbed more phosphate than those in peat soil. In both soils uptake decreased as depth of phosphate injection increased from 5 to 30 cm. An interaction occurred whereby roots in the intermediate depth (10–22‐5 cm) in peat absorbed less phosphate than in mineral soil and this was apparently unrelated to the exchange or sorption properties of the soil.
The translocation of 14C photosynthate from leaves and pods in Phaseolus vulgaris
Authors: LUCAS E. O. , MILBOURN G. M. , WHITFORD P. N.
Published: February 2008

Field experiments were undertaken to study the pattern of distribution of photosynthate produced by the leaves and the pods of Phaseolus vulgaris (cv. Purley King) by means of the 14C technique. It was found that the UC photosynthate produced by a trifoliate leaf (38 days after anthesis) was shared almost equally between the leaf and the pod at its axil with 33–50% of the fixed 14C finding its way to the seeds in that pod. However, during the early stages of pod development (10 days after anthesis) some 13–14% of the fixed 14C was detected in the stem, indicating the inadequacy of the pod as a sink at that stage. When the pod was treated, virtually no 14C was detected in other parts of the plant. Of the 14C fixed by pod photosynthesis in the later stages (38 days after anthesis), 55–60% was translocated to the seeds within the same pod. These results indicate the importance of current photosynthesis during the pod fill stage in P. vulgaris as has been suggested in other grain legume crops.
Temperature control in the rooting medium during propagation
Authors: WHALLEY D. N. , RANDALL R. E.
Published: February 2008

Control of rooting medium temperature by using electronic controllers with thermistor or semiconductor sensors is described and compared with electromechanical sensors. Electronic controllers are advantageous in that they are versatile, and can more accurately sense and control temperature in the rooting zone itself. Such improved control may often result in higher percentage of rooted cuttings and in better root systems.
The susceptibility of the elm bark beetle Scolytus scolytus to the DD‐136 strain of Neoaplectana sp.
Authors: FINNEY J. R. , MORDUE W.
Published: February 2008

Adults and larve of Scolytus scolytus were highly susceptible to the DD‐136 strain of Neoaplectana sp. in the laboratory.
The influence of the parasitic Striga species on the host crops sorghum and maize
Authors: Parker C.
Published: February 2008

The biology of the Striga species will be briefly described. Pot experiments indicate that damage to the host plant is very much greater than is explained by removal of photosynthates. A phytotoxin is almost certainly involved, which causes decreased shoot growth of the host plant but which also directly or indirectly encourages increased root growth. The significance of this change in root/shoot ratio will be discussed in relation to host resistance and various control measures.
Benomyl tolerance in Verticillium dahliae
Authors: TALBOYS P. W. , DAVIES MOIRA K.
Published: February 2008

In Verticillium dahliae isolates (‘wild type’) obtained prior to the advent of benzimidazole fungicides, growth of germ tubes and extension of mycelium were typically inhibited by benomyl at 0–3 ppm and 0.5‐1.0 ppm respectively. Culture of such isolates in the presence of increasing concentrations of benomyl resulted in the selection of variants able to grow at 12.0 ppm.

Conidia, and mycelium grown for 24 b, were each more sensitive to inhibition by benomyl than mycelium grown for 48 h. Mycelium of both wild‐type and selected variants was still viable after treatment with 20 ppm benomyl in a nutrient medium for 112 days. Long‐term treatments at 20 ppm caused the enlargement of mycelial cells and conidia, thickening of the cell walls and formation of large spherical inclusions apparently comprising or containing lipids.
The transmission and effect on yield of ryegrass mosaic virus in a filtered air environment
Authors: GIBSON R. W. , PLUMB R. T.
Published: February 2008

The eriophyid mite vectors of ryegrass mosaic virus (RMV) were excluded from ryegrass by covering plots with a polyethylene film house ventilated by filtered air. Initially plots were manually inoculated to give different levels of RMV. During two seasons no mites were found within the house so that all transmission of virus was by sap. Rolling and frequent cutting of uninfected plots decreased yields, but surprisingly, increasing virus infection did not decrease yields significantly. Cutting transmitted virus within infected plots but not from infected to healthy plots, whereas combined rolling and cutting did transfer virus to healthy plots.
Occurrence of plantago mottle virus in pea, Pisum sativum, in New York State
Authors: PROWIDENTI R. , GRANETT A. L.
Published: February 2008

Plantago mottle virus (RMV), a member of the tymovirus group, was identified as the causal agent of a disease of pea (Pisum sativum) in New York State. The pea virus isolates were identical in host range and serology to the type strain from Plantago major. In susceptible pea genotypes symptoms were strongly influenced by ambient temperature; high temperature (35°C) reduced infectivity and suppressed symptoms, whereas low temperature (15 and 25°C) prolonged the incubation period but favoured the development of conspicuous leaf veinal chlorosis, mottle and necrosis.

Resistance to P1MV was found in seventeen of twenty‐five domestic pea cultivars and in two of twelve foreign introductions. Many of the P1MV‐resistant lines were resistant also to bean yellow mosaic virus. The use of resistant cultivars and the apparent limited conditions for efficient transmission of this virus have minimized its importance to pea crops in New York State.
Fumigation with D‐D or Telone on soils prone to Docking disorder
Authors: COOKE D. A. , WINFIELD A. L. , ATKINSON KAY M. , JOHN MARGARET E. , WILSON W. R.
Published: February 2008

Field trials in 1970‐2 tested the effect on nematode numbers of pre‐sowing fumigation with c. 641 D‐D/ha or c. 43 1 Telone/ha injected behind coulters at the same spacing as the rows of beet (‘band treatment’), the same amounts of fumigant injected both beneath and between the rows, i.e. at half‐row spacing (‘overall‐low’, totalling c. 1281/ha or 851/ha respectively) and a double dose of these fumigants at half‐row spacing (‘overall‐high’, totalling c. 256 1/ha or 170 1/ha respectively). Numbers of Trichodorus and Longidorus in the sugar‐beet rows were decreased by 68 and 86% respectively by band treatment; by 83 and 94% by overall‐low and 92 and 97% by overall‐high treatments. Populations of Longidorus recovered slowly, especially following overall treatment; populations of Trichodorus recovered more quickly, but 16 months after overall treatment they were still fewer than in the unfumigated plots. There was no correlation between nematode numbers recorded before sowing sugar beet and either the response of the crop to fumigation or the final yield of sugar beet.
Respiration of maleic hydrazide treated and untreated onion bulbs during storage
Authors: WARD C. M. , TUCKER W. G.
Published: February 2008

Respiration rates were determined at a range of temperatures on onion bulbs cv. Rijnsburger sampled from a cool‐stored bulk over a period of 8 months. In the first 5 months of storage, respiration rates were low and showed a small increase with temperature. During this period there was little or no difference between untreated bulbs and those treated with maleic hydrazide (MH) prior to harvest. Subsequently there was a rise in respiration rates, which preceded sprouting, but this was not evident in MH‐treated bulbs. A relationship between respiration and dormancy was suggested by the correlation between respiration rate in January and sprouting in June for four cultivars.
Glandular hairs are a possible means of limiting aphid damage to the potato crop
Authors: GIBSON R. W.
Published: February 2008

Glandular hairs on leaves and stems stuck naturally‐occurring aphids to field grown plants of Solamim polyadenium, S. berthaultii, and first and second generation hybrid S. tuberosum cv. Pentland Crown ×berthaultii, but none became stuck on Pentland Crown. S. polyadenium had most glandular hairs, stuck most aphids and had fewest free aphids. In the glasshouse, the percentage of stuck aphids was positively correlated with the abundance of glandular hairs, especially on the leaves, so counting the hairs may be a simple preliminary method of screening for aphid‐trapping ability.
Prevention of potato top‐roll by aphicide and its effect on leaf area and photosynthesis
Authors: GIBSON R. W. , WHITEHEAD D. , AUSTIN D. J. , SIMKINS JANE
Published: February 2008

In a field of potatoes, top‐roll, which is induced by the aphid Macrosiphum euphorbiae feeding on the leaves, was restricted to two rows of plants which accidentally received no phorate aphicide granules at planting. The photo‐synthetic rate per unit leaf area and the ground cover of top‐rolled leaves were respectively 50% and 20% less than those of normal plants which may account for the smaller yields of affected plants observed in previous experiments.
Simple extraction and bioassay of the female sex pheromone of the citrus mealybug, Planococcus citri
Authors: ROTUNDO G. , TREMBLAY E.
Published: February 2008

The sex pheromone released by the females of the citrus mealybug was extracted from virgin females by ethanol, diethyl ether or petroleum ether but not by toluene, w‐hexane or w‐pentane. Extracts in ethanol, diethyl ether or petroleum ether placed on filter paper and hydrophilized polymethylmethacrylate disks elicited high attraction and copulation responses in the male mealybugs.
Influence of crop background on aphids and other phytophagous insects on Brussels sprouts
Authors: SMITH JUDITH G.
Published: February 2008

More Brevicoryne brassicae and other alate aphids were caught in yellow water‐traps in a weed‐free crop of Brussels sprouts than in a crop with a weedy background. More B. brassicae colonized Brussels sprout plants in bare soil than in weeds; very few alatae were attracted to cruciferous weeds in the crop. Results in 1 yr suggest that initially larger populations on the weed‐free sprouts became smaller than populations on the weedy sprouts because the larger aphid population attracted more natural enemies. Aleyrodes brassicae and certain Lepidoptera were also more abundant on sprout plants in bare soil than on sprouts surrounded by weeds; more adult A. brassicae were caught in water traps over the bare soil.

More A. brassicae were present on sprout plants surrounded by a green than by a brown cloth background but the differences were not significant (P < 0–05). Numbers of B. brassicae on sprout plants with green and brown backgrounds varied greatly and did not differ significantly.

In field cages, B. brassicae alatae were more attracted to potted sprout plants surrounded by bare soil than to ones surrounded by rings of living or cut grass or by artificial green rings. This effect was greater with small than with large sprout plants surrounded by grass rings.

The maintenance of a limited weed cover is considered potentially useful in integrated control of some brassica pests.
The effects of Cercospora leaf disease on the growth of groundnuts (Arachis hypogaea) in Nigeria
Authors: ELSTON J. , HARKNESS C. , McDONALD D.
Published: February 2008

Three experiments with five alternately‐branched and one sequentially‐branched cultivar of groundnuts are described. Spraying to control Cercospora leaf spot disease doubled the leaf area duration and increased the total weight of a plant by about 65 %. Spraying increased the weight of kernels per plant but in the alternately‐branched cultivars also increased the weight of stem and leaves. The proportion of the total dry weight in the kernels in the alternate cultivars was hardly changed by spraying. The sequentially‐branched cultivar gave the same increase in total dry weight when sprayed but spraying resulted in a larger increase in the dry weight of kernels. The sequentially‐branched cultivar, with few initials for vegetative growth, did not give the same increase in leaf growth.
Fungitoxicity of mineral oils against Rhizoctonia solani causing damping‐off of mung bean (Phaseolus aureus)
Authors: KATARIA H. R. , GROVER R. K.
Published: February 2008

Three mineral oils, BSO, EWOS and E9267 and one vegetable oil (mustard oil), did not appreciably inhibit the mycelial growth of Rhizoctonia solani. However, treatment of 100 g seeds of mung bean with 2 ml EWOS and E9267 oils controlled more than 90% of the pre‐ and post‐emergence damping‐off and protected seedlings in soil inoculated with R. solani 5 days after sowing. Soaking seeds in solutions of these oils or drenching the soil did not control damping‐off.

Mustard oil controlled only pre‐emergence damping‐off.
Effect of photoperiod on development and number of spikelets of a temperate and some low‐latitude wheats
Authors: ALLISON J. C. S. , DAYNARD T. B.
Published: February 2008

Four low‐latitude cultivars (two Mexican and two Rhodesian) and a Canadian cultivar were grown in controlled environments in four photo‐periods, 16, 13, 10 and 7 h, respectively. Plants of two of the low‐latitude cultivars were also transferred between long and short photoperiods during ear differentiation.

The intervals from sowing to successive stages of ear development up to the formation of the terminal spikelet, and to ear emergence, and the number of leaves, all increased as photoperiod decreased. The Canadian cultivar responded most and one of the Rhodesian cultivars least to changes of photoperiod in these respects. However, with all the low‐latitude cultivars, the interval between formation of the terminal spikelet and emergence of the ear responded similarly and relatively little to decreasing photoperiod except when photoperiod was reduced from 10 to 7 h. The mean rate of spikelet production decreased as the duration of the period of spikelet production (DSP) increased, i.e. as ear development slowed down with decrease in photoperiod. Accordingly number of spikelets per ear increased curvilinearly as DSP increased, suggesting a maximal number of spikelets of about thirty. Rate of spikelet production apparently differed between cultivars.

Development of the ear slowed down when plants were moved to a shorter photoperiod and accelerated when they were moved to a longer photoperiod, both at the time at which the shoot apex began to elongate and at the double ridge stage. Final number of spikelets per ear increased when ear development was slowed down and decreased when it was accelerated.
The loss of electrolytes from leaves treated with hydrocarbons and their derivatives
Authors: BOYLES D. T.
Published: February 2008

Indices of the effects on the leaves of a number of plant species of members of homologous series of hydrocarbons and certain of their oil‐soluble derivatives were based on changes in conductance of aqueous systems when hydrocarbon‐treated leaves were added. The results were compared with previous phytotoxicity studies where hydrocarbons were applied to plants in vapour and in aqueous treatments. A relationship between the conductance changes and the physical properties of the applied hydrocarbons is suggested. The presumed effects on cell membrane permeability indicated by the conductance changes agreed with known susceptibility of different plant species towards hydrocarbons of different homologous series applied in the liquid state.
Studies on plant growth‐regulating substances
Authors: PRICE D. N. , WAIN R. L.
Published: February 2008

Nitrophenols structurally similar to 4‐hydroxy‐3‐nitrobenzoic acid and 4‐hydroxy‐3‐nitrobenzaldehyde have been examined for their ability to inhibit chloroplast development in linseed and oat seedlings, and their activity has been estimated quantitatively in specifically designed clover and Lemna bioassays. Twelve compounds were found to be active and activity is considered in relation to chemical structure. A nitro group in the 3‐position and a hydroxyl group or ether linkage in the 4‐position were found to be essential for activity whereas the nature of the functional group in the 1‐position could vary considerably.

Possibilities in which activity might arise from metabolism of the applied compound were investigated using excised wheat and pea tissue, and compounds with various groupings in the 1‐position were shown to be converted to the corresponding active benzoic acid derivative.
The genetic relationship between races of Bremiae lactucae and cultivars of Lactuca sativa
Authors: CRUTE I. R. , JOHNSON A. G.
Published: February 2008

The reactions of lettuce cultivars to physiologic races of Bremia lactucae are interpreted in terms of a gene‐for‐gene relationship between pathogen and host. The hypothesis takes into account the parentage of cultivars and the origins of their resistance, the characteristics of the resistance reactions and data available from detailed genetical analysis of various race/cultivar combinations. Cultivars are classified with respect to ten postulated resistance genes and B. lactucae races are defined by the virulence genes present. The practical significance of these studies is discussed in relation to both future lettuce breeding programmes and to the choice of cultivars available to counteract any given local race situation.
Breeding for reduced seed coat fuzz in Upland cotton (Gossypium hirsutum)
Authors: INNES N. L. , WIMBLE R. H.
Published: February 2008

The inheritance of seed coat fuzz was studied in two half diallel sets of crosses of Upland cotton. One with F4 selections from an inter‐varietal cross showed a significant level of non‐additive variance attributable to dominance and non‐allelic interaction. In the other, using inbred varieties of diverse origin, the genetic control of seed fuzz was adequately accounted for by an additive‐dominance model with no interaction.

Genotypic correlations between seed coat fuzz, yield and lint quality characters, calculated for both diallel sets and for two other groups of breeding material, showed good agreement within each experiment between parents and hybrids or between parents and progenies but no consistent pattern between experiments. The results serve to emphasize the risks in extrapolating correlations from one group of breeding material to another.

A useful level of reduced fuzz has been obtained in selections from the AH breeding programme and the genetical investigations indicate that a further reduction may be possible, thereby leading to easier handling of seed, speedier and cheaper ginning, low levels of seed coat nep and better seed germination.
Post‐harvest chemical treatments for the control of storage disorders of apples
Authors: SHARPLES R. O. , JOHNSON D. S.
Published: February 2008

Immersion of apples of the varieties Cox's Orange Pippin and James Grieve for 1 min in solutions of calcium chloride or nitrate reduced the incidence of bitter pit and senescent breakdown that developed during air storage at 3 °C. Calcium nitrate treatments decreased the severity of superficial scald in both Bramley's Seedling and Cox apples probably by slightly delaying the rate of senescence. Calcium chloride caused unacceptable levels of damage when applied to Cox and Grieve at concentrations above 0.125 M; this injury was enhanced in Cox when benomyl was added to this strength of solution. Bramley's Seedling apples were more sensitive to calcium injury than Cox, especially in the presence of benomyl and the scald inhibitor, ethoxyquin; diphenylamine did not increase calcium injury. Calcium nitrate caused more damage to Cox than equimolar concentrations of the chloride without improving the control of bitter pit. Virtually no damage occurred when Cox and Grieve apples were immersed for 10 min in 0.125 M calcium nitrate at 45 °C. The incorporation of calcium in warm water treatments to control rotting and scald may delay sensecent breakdown in heat‐treated apples.
Observations on the effect of black root rot (Phomopsis sclerotioides) on the susceptibility of cucumber to powdery mildew (Sphaerotheca fuliginea)
Authors: EBBEN MARION H. , SEARLE LINDA M.
Published: February 2008

Powdery mildew (Sphaerotheca fuliginea) infection of cucumber leaves was earlier and increased more rapidly on plants with black root rot (Phomopsis sclerotioides) than on plants with healthy root systems in the same glasshouse.
Progress towards a biological control programme for glasshouse whitefly (Trialeurodes vaporariorum) on tomatoes
Authors: PARR By W. J. , GOULD H. J. , JESSOP N. H. , LUDLAM F. A. B.
Published: February 2008

During 1969/74 different methods of using the parasite Encarsia formosa to control whitefly infestations on tomatoes in glasshouses have been evaluated commercially. The most effective control was achieved by the Glasshouse Crops Research Institute (GCRI) programme of timed parasite introductions at rates totalling 120000 parasites per ha (48000/acre) following the pre‐establishment of a low, evenly distributed infestation of the pest throughout the crop. Other methods, including the regular introduction of parasites after planting in anticipation of a whitefly infestation or starting when the first whiteflies appear on the plants, are also described. These multiple introduction (‘dribble’) methods, gave mostly satisfactory control but were less predictable.

The efficiency of the parasite is greatly impaired during the short days and low light intensities of the late winter months and alternative methods of dealing with early whitefly infestations, including the use of chemicals, are discussed.
Strains of Colletotrichum coffeanum, the causal agent of coffee berry disease, tolerant to benzimidazole compounds in Kenya
Authors: COOK R. T. A. , PEREIRA J. L.
Published: February 2008

The detection of Colletotrichum coffeanum tolerant to methyl ester of benzimidazole 2‐carbamic acid (carbendazim) and a related benzimidazole compound, cypendazole, followed increases in levels of coffee berry disease observed on Coffea arabica in experimental plots sprayed for 2 yr with these compounds.

Sporulation by the pathogen on naturally infected berries removed from carbendazim‐, cypendazole‐ or benomyl‐sprayed plots was not checked by a further application of 0–05 % (a.i.) of any of the compounds. Nearly all the isolates from these berries were capable of some growth on agar media containing 1000 ppm (a.i.) of either carbendazim or cypendazole. However, only a few could tolerate 1000 ppm of benomyl and the inability of this compound to reduce sporulation on berries infected with tolerant strains was presumably due to its rapid conversion to carbendazim within the host tissue.

Less than 1 ppm of carbendazim, cypendazole or benomyl was needed to give 50% inhibition of conidia of the normal strain. Against the most tolerant strains, however, the LD 50 was > 100 ppm of carbendazim and about 30 ppm of benomyl.

Whether isolated from unsprayed or benzimidazole‐sprayed plots, all isolates of Colletotrichum acutatum, a saprophytic cohabitant of lesions initiated on berries by C. coffeanum, showed the highest degree of tolerance to benzimidazole compounds.

No tolerance of either fungus to the ‘conventional’ fungicide captafol was detected.
Overwintering of Sphaerotheca humuli, the cause of hop powdery mildew
Authors: LIYANAGE A. de S. , ROYLE D. J.
Published: February 2008

The ability of Sphaerotheca humuli to overwinter as cleistocarps in infected hop cones and leaves and in aerial buds on rootstocks was examined during the winters of 1970‐1, 1971‐2 and 1972‐3.

Periodical examination of cleistocarps, collected in October and overwintered in Terylene bags on the soil of a hop garden, consistently revealed two periods of maturation ending in November and in March, when over 50% contained eight, well‐defined ascospores. In laboratory tests cleistocarps, kept either in the hop garden or dry at 4, 8 or 18oC during the winter, could not be encouraged to dehisce earlier than April when naturally dehisced cleistocarps were first detected in the field. More ascospores were discharged from cleistocarps, and germination of ascospores in laboratory tests was greater, at 18 than at 4, 8 or 24oC. Colonies of S. humuli arose on leaves of potted plants exposed to overwintered cleistocarps in the hop garden and were observed microscopically to originate from ascospores. However, a Burkard spore trap, operated amidst the cleistocarps in this garden in 1972 and 1973, failed to detect ascospores. Ascospores, discharged onto susceptible leaves in the laboratory, germinated but failed to produce colonies.

It was demonstrated that S. humuli can perennate in aerial, dormant buds on hop rootstocks. Examination of buds in autumn revealed mycelium external to and between the bud scales. At budburst the mycelium was still present internally. Cleistocarps were occasionally associated with hibernating mycelium. Primarily infected shoots arose from plants bearing infected buds in conditions which precluded chance infection. Some evidence was obtained that conditions during the winter determine the success of survival in buds.

The fungus appeared to be incapable of infecting a selection of weeds common to hop gardens and their vicinity.
Tolerance to ryegrass mosaic virus, its assessment and effect on yield
Authors: WILKINS P. W. , HIDES D. H.
Published: February 2008

Symptom severity of eighteen populations of Italian ryegrass infected artificially in the glasshouse and naturally in the field with ryegrass mosaic virus (RMV) was strongly correlated. A smaller proportion of plants of the more tolerant populations showed symptoms in the field, but this was probably due to an association of tolerance with increasing incidence of symptomless infection rather than with resistance to infection.

Under sward conditions, the yield of a sensitive genotype was reduced by 27% and that of two more tolerant ones by 15 and 13 %. The percentage dry matter yield loss of the most sensitive genotype was similar in all cuts, despite the appearance of extensive necrosis at the time of one cut. With the more tolerant genotype the yield loss varied from 7 to 25 % according to cut. Over the period of the experiment RMV infection did not increase plant mortality.
The involvement of ethylene in the coiled sprout disorder of potato
Authors: CATCHPOLE A. H. , HILLMAN J. R.
Published: February 2008

Application of low concentrations of ethylene gas to the sprouts of Arran Pilot elicited many of the morphological and anatomical symptoms of the coiled sprout disorder. Similar effects were observed using 2‐chloroethyl‐phosphonic acid (Ethrel).

Obstruction of coil‐prone etiolated sprouts led to enhanced ethylene production for a period of two to three days but this pattern was not shown by non‐coil‐prone sprouts.
Some treatments affecting growth substances in developing wheat ears
Authors: WHEELER A. W.
Published: February 2008

Cytokinin, auxin and gibberellin‐like substances were bio‐assayed in extracts from developing ears of wheat plants grown in various conditions. Changes in cytokinin activity along the ears may be related to the earlier flowering in the middle of the ear. Ears on the main stems of plants from which all the tillers had been removed contained less cytokinin than the main‐stem ears of normal tillered plants. When grain development was stopped by preventing fertilization of the ovules the ear contained more cytokinin than normal ears. With de‐tillered plants, removing flag leaves before anthesis increased cytokinin, gibberellin and auxin in the ears; later removal of flag leaves did not affect cytokinin but decreased gibberellin in the ears. Conversely, removing ears before anthesis did not affect cytokinin or auxin in the flag leaves, but their gibberellin was less than that of flag leaves on intact plants. Treatment of wheat ears with zeatin did not affect grain weight or number per ear which supports the conclusion that the growth substances in the ear may be adequate for normal grain growth.