bluuebunny/crossref_metadata_2025 huggingface dataset:
The pathogenicity and increase of Heterodera rostochiensis on tomato cultivars, self‐rooted or grafted on to rootstocks.
Authors: HESLING J. J. , ELLIS P. R.
Published: February 2008

Self‐rooted tomatoes ‘Ailsa Craig’ and ‘Kingley Cross’, and scions of ‘Ailsa Craig’ grafted on to different rootstocks, were grown in soil infested with different numbers of Heterodera rostochiensis (Mainly pathotype A). Three rootstocks (RS4, RSKN, ISKVF) tolerated damage from nematode populations of up to 125 eggs/g soil, but nematodes increased up to x45 on them. Two nematode‐resistant F1 hybrid rootstocks, B6633 (ex Lycopersicon pimpinellifolium B6173) and B6015 (ex L. hirsutum var. glabratum B6013), tolerated up to 125 eggs/g soil; nematode populations declined as much as 80% under B6633, and increased little under B6015. On the self‐rooted ‘Ailsa Craig’ and ‘Kingley Cross' the numbers of nematodes increased markedly (maximum increase x40), and greatly affected growth and yield so that initial populations greater than 62 eggs/g soil caused crop failure.
Chemosterilization of the cabbage root fly under field conditions
Authors: FINCH S. , SKINNER G.
Published: February 2008

Removing hedgerow feeding sites from within 40, 80 or 160 m of cauliflower plots, failed to reduce populations of the cabbage root fly (Erioischia brassicae (Bouché)). Oviposition on the plots was unchanged but the efficiency of yellow water‐traps was improved. Traps along‐side cleared hedgerows caught more gravid than non‐gravid females. In cages, 94% of the eggs laid were sterile when both sterilant baits containing tepa [tris‐(i‐aziridinyl) phosphine oxide] and hedgerow flowers were present.

In the field, maximum egg‐sterility rarely exceeded 30% when sterilant was present when natural sterility averaged 8%. Chemosterilization was an inadequate control since sufficient eggs and larvae survived to produce root‐damage indices of 49 % in contrast to 2 % on insecticide‐treated plants.

Most eggs were sterile when chemosterilant baits were placed 0.75 m apart and bait was most effective when placed around the crop during the pre‐oviposition period and through the crop at the time of maximum oviposition. Increasing the concentration of tepa failed to increase the effectiveness of the bait but a higher proportion of the eggs laid were sterile on large than on small plots. When chemosterilant treatments were stopped, egg‐fertility gradually reverted to the natural level.

Protracted immigration, an innate tendency for females to disperse, reductions in the competitiveness of sterile males, and the failure of males to re‐disperse once sterilized, appeared to be the main factors limiting the levels of sterility in root‐fly populations exposed to tepa‐baited lures in the field.
Further studies on seed transmission in the ecology of some aphid‐transmitted viruses
Authors: TOMLINSON J. A. , WALKER VALERIE M.
Published: February 2008

A small proportion (1–4%) of the seeds of Stellaria media extracted from fallow soil from three widely separated areas contained cucumber mosaic virus (CMV). S. media seeds buried for 21 months produced 5 % infected seedlings.

S. media plants from Britain, N. America and Australia were least severely affected by the CMV strain obtained from their country of origin and showed more severe reactions when infected with two alien strains.

Several weed species were experimentally infected with lettuce mosaic, turnip mosaic and cauliflower mosaic viruses but, although virus was detected in the seeds of some species, it was not transmitted to any of their seedlings.
Studies in vitro and in vivo with powdery mildew fungicides
Authors: CLIFFORD D. R. , HISLOP E. C.
Published: February 2008

Droplets of 4‐(i‐cycloalkylalkyl)‐2,6‐dinitrophenols often protect areas of leaf very much greater than that of the initial deposit against powdery mildew. For a given alkyldinitrophenol, this type of protection is greater on apple than on marrow leaves. This zonal protection is not correlated with vapour activity in vitro or in vivo, or with inhibition of conidial germination in vitro, but is correlated with the degree of protection obtained when leaves are sprayed to give good cover. By contrast, crotonic esters of these alkyl‐dinitrophenols do not show zonal activity, but nevertheless often exhibit protectant activity comparable with that of the parent phenols. These results suggest that exploitation of favourable hydrogen bonding characteristics in the fungicide molecule may lead to better control of fungal diseases in the field as a result of enhanced movement of fungicide in or on the leaf cuticle (zonal movement) or easier penetration of the fungal conidium.
An apparatus for the isolated propagation of foliar pathogens and their hosts
Authors: JENKYN J. F. , HIRST J. M. , KING G.
Published: February 2008

Epidemiological studies, especially of obligate pathogens, often require healthy test plants and the incubation of infections in isolation. Ventilation of glasshouses with spore‐free air is helpful but costly, and provides only a few discrete environments. The apparatus described is cheap and simple and enables many separate covered plant pots to be supplied with filtered air. It was designed to help measure the incubation time and frequency of viable conidia ofErysiphe graminis, but may also be useful for studying other pathogens and, with some modification, for plant breeding or quarantine.
Chemical investigations on resistance to coffee berry disease in Coffea arabica. An antifungal compound in coffee cuticular wax
Authors: LAMPARD J. F. , CARTER G. A.
Published: February 2008

Investigations have been made into the possibility of a chemical basis for resistance to coffee berry disease in certain Coffea arabica varieties. Chloroform extracts of the cuticular wax of berries, purified by fractionation and chromatography, proved toxic to a range of fungi including Colletotrichum coffeanum, the causal organism of coffee berry disease. Leaf cuticular wax also contained this fungitoxic principle, though at a lower level. The possible importance of this antifungal material in determining resistance to coffee berry disease is discussed.
The production of pure stocks of self‐pollinating cereal varieties
Authors: HANSON PETER
Published: February 2008

The method of cereal pure stock production used at the Plant Breeding Institute is described. Multiplication from fifty plants to commercial seed stocks takes 5 years; individual ears are inspected each year and an ear‐row/ear‐row progeny system is used. An accelerated system reducing the period of multiplication to 4 years is also described. The advantages and disadvantages of other multiplication methods are discussed.
Laboratory rearing, biology and chemical control of the mushroom sciarid Lycoriella auripila (Diptera: Lycoriidae)
Authors: BINNS E. S.
Published: February 2008

The mushroom sciarid was found to develop on a plant‐derived diet of oat or soya meal. Details of simple rearing techniques and insecticidal assays of treated casing are given. In laboratory tests using ten chemicals, chlorfenvinphos and pirimiphosethyl showed persistent activity against larvae when used at 15 ppm and are suggested as suitable for incorporation in peat‐chalk casing mixtures to give protection throughout cropping. The low figures obtained for phytotoxicity and residues in the crop suggest this technique would be acceptable in commerce. Diazinon remained active in casing for only a short time.
Bionomics of aphids reared on cereals and some Gramineae
Authors: DEAN G. J. W.
Published: February 2008

In controlled temperature, light and relative humidity, Metopolophium dirhodum and Sitobion avenae multiplied more on young Proctor barley than on Blenda oats, and less on Cappelle wheat. Rhopalosiphum padi increased in number fastest on barley and slowest on oats. More survived, and generation lengths seemed shorter, on barley for M. dirhodum and S. avenae and on wheat for R. padi.

Tests with young cereals outdoors generally agreed with those in controlled conditions. On mature plants, there were more M. dirhodum on barley, more R. padi on wheat and more S. avenae on oats than on the other cereals.

Given a free choice in large cages outdoors, most aphids were found on barley. When allowed to choose between grasses, more M. dirhodum were on Dactylis glomerata, Poa pratensis and Festuca pratensis, more R. padi on Lolium perenne and F. pratensis, and more S. avenae on D. glomerata and L. perenne. Most aphids of all species combined were on F. pratensis, Lolium and Phleum, and fewest on Festuca rubra and Holcus mollis.
Genetic determination of honeybee (Apis mellifera L.) foraging preferences
Authors: FREE J. B. , WILLIAMS INGRID H.
Published: February 2008

Progeny from different honeybee queens that were reared in, and foraged from, the same colony sometimes differed in their floral preferences, confirming that these are to some extent innately determined.
The effect of benomyl on the infection of tomatoes by Fusarium oxysporum f.sp. lycopersici and Botrytis cinerea
Authors: CHANNON By A. G. , THOMSON MOIRA C.
Published: February 2008

In glasshouse experiments at Auchincruive, drench applications of benomyl (100 or 142 mg per plant) to the soil surface around the stem bases of pot‐grown tomato plants before inoculation with Fusarium oxysporum f.sp. lycopersici reduced the penetration of the fungus up the stems and/or decreased the development of vascular discoloration and associated severity of wilting. Similar drenches applied after establishment of the fungus in the stems either halted or considerably retarded the growth of the pathogen up the vessels. This again was reflected in reduced vascular discoloration and wilt symptoms.

In experiments with benomyl over 2 years at a commercial holding in Argyll, the application of soil drenches (at the rates above) shortly after planting out and again 5 weeks later, coupled with a programme of stem and foliar sprays (at 0–05 % a.i.) during the summer, reduced the development of stem lesions caused chiefly by Botrytis cinerea and increased the general survival of plants more than did drench or spray treatments alone. There were indications that ‘ghost spotting’ of the fruit, particularly where spray applications were made, was also slightly reduced, but the magnitude of the effect was not consistent.
Studies on plant growth‐regulating substances: XXXV. Ethylene production by coleoptiles treated with auxin‐type chemicals
Authors: GOLDWIN G. K. , WAIN R. L.
Published: February 2008

Wheat coleoptile sections were treated with a range of auxins and with compounds of related chemical structure which do not exhibit auxin properties. Methods used for measuring the rates of elongation and ethylene evolution of these sections are described.

Ethylene was evolved some time after elongation in all cases and increased ethylene production occurred only with compounds showing auxin activity. The results indicate that ethylene evolution was related exponentially to growth.

Simultaneous applications of mannitol and 2, 4‐dichloro‐phenoxyacetic acid (2, 4‐D) to wheat sections markedly reduced ethylene evolution compared with the 2, 4‐D controls, even though the level of 2, 4‐D in the tissue apparently remained unchanged.

Ethylene significantly inhibited the elongation of wheat coleoptile sections, and it is suggested that ethylene is a natural plant growth inhibitor which becomes mobilised to limit excessive growth.
Aphid colonization of spring cereals
Authors: DEAN BY G. J.
Published: February 2008

In 1970‐1, Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae were the commonest alatae trapped from April/May to August, with most in July and early August. The first alatae appeared in the Rothamsted survey suction trap 0–34 days before aphids were found on the cereals, but during May and June no relationship was found between the numbers trapped and the number on the crop. Most species occurred first near the sheltered edge of the crop, but M. dirhodum was widespread over the field. Most infestations were quickly dispersed by the movements of older morphs; adults only stayed in one place for about 2 days. Alate M. dirhodum moved more often than apterae, but both morphs of S. avenae moved equally often and more frequently between larvipositions than did those of M. dirhodum. Apterae deposited more nymphs in a ‘group’ than alatae, and M. dirhodum deposited more than S. avenae. Few ‘groups’ persisted for more than a week. Although M. dirhodum occupied the crop area faster than S. avenae, all 0–3 m lengths of row sampled being infested within 2–5 wk of their first appearance, most or all of the tillers were colonized only in late July 1970.
The survival of Mycosphaerella pinodes on pea haulm buried in soil
Authors: SHERIDAN J. J.
Published: February 2008

Where haulm was left on the soil surface the mycelium of Mycosphaerella pinodes went through cycles of active saprophytic growth, followed by inactive phases during the earlier parts of the year. Burial at either 15 or 25 cm brought about a decrease in survival with time. The majority of the mycelium was on the outer portions of the stem pieces, with only a small amount of penetration into the plant remains. Experiments on root surface colonization showed that mycelium of M. pinodes was capable of growing saprophytically on the host roots in competition with the normal soil microflora.
Fungitoxic and phytotoxic effects of fungicides controlling powdery mildew on apple
Authors: BUTT D. J. , KIRBY A. H. M. , WILLIAMSON CYNTHIA J.
Published: February 2008

Benomyl, pyrazophos (HOE 2873), triarimol, triforine and the non‐systemic fungicide diethyl phthalimidophosphonothionate (Dowco 199) were sprayed at c. 200 gal/acre (2250 1/ha) at 14‐day intervals from pink bud (late April/early May) on seven apple cultivars including Cox's Orange Pippin, Golden Delicious and Jonathan. Compared with binapacryl or dino‐cap (and with elemental sulphur on the sulphur‐tolerant cv. Golden Delicious), these compounds were more phytotoxic without substantially or consistently improving the control of Podosphaera leucotricha; fruit russet was increased and the crop and fruit size of some cultivars were reduced in some trials. In 1969 the inclusion of bis(dimethylthiocarbamoylthio)‐methylarsine (44 ppm) as Urbacid(R) in the sprays reduced russeting by benomyl and Dowco 199 so that these fungicides became as safe as captan on several cultivars; Dowco 199 was also safened by captan (500 ppm). Urbacid(R) (88 ppm a.i.) safened benomyl and triarimol on fewer cultivars in 1970 when russet was less severe. The addition of Urbacid(R) did not prevent yield losses caused by sprays in either year.

The crop is most sensitive to spray damage from pink bud until late June. This is a crucial period for the control of mildew, and unless new fungicides are less phytotoxic, palliatives may become necessary adjuvants.
A self‐powered portable insect suction sampler and its use to assess the effects of azinphos methyl and endosulfan on blossom beetle populations on oil seed rape
Authors: ARNOLD A. J. , NEEDHAM P. H. , STEVENSON J. H.
Published: February 2008

A new portable insect suction sampler, powered by a small petrol engine, is described. It has been in use for three seasons, and examples given of samples taken from oil‐seed rape demonstrate that the suction method is more informative than visual counts or sweep‐net sampling for assessing blossom beetle populations.
Activity of six fungicides against cereal foliage and root diseases
Authors: JENKYN J. F. , PREW R. D.
Published: February 2008

During 1970 and 1971 six systemic fungicides were compared as seed dressings and sprays against foliage and root diseases of cereals. The fungicides differed greatly in effectiveness against mildew, loose smut, rusts and eyespot but none controlled take‐all. Effects were also noted on germination, seedling growth and leaf‐surface microflora.
Stomatal control of gas exchange in barley awns
Authors: BISCOE P. V. , LITTLETON E. J. , SCOTT R. K.
Published: February 2008

The gas exchange of barley ears and awns was measured in the field using a gas analysis system and a diffusion porometer. Awn stomatal resistance decreased with increasing irradiance but to a smaller extent than leaf stomatal resistance. Measurements on ears immediately before and after successively removing awns showed that awn transpiration and photosynthesis were proportional to awn area and that awns accounted for 73% of transpiration by the ear. Although the maximum rates of photosynthesis of which awns were capable declined with age, awns accounted for 80–115% of the net CO2 uptake of complete ears because the ears‐less‐awns could respire more CO2 than they absorbed. Ear photosynthesis accounted for 52% of the weekly increment in ear dry weight after ear emergence, but 5 weeks later photosynthesis by the ear balanced respiration. Overall photosynthesis by the ear accounted for 35 % of its final weight. Differences in the light response curves of leaves and ears can be fully accounted for by the different relationships between stomatal resistance and irradiance of the two organs.
Effects of population density on alienicolae of Aphis fabae Scop.: The expression of migratory urge among alatae in the field
Authors: SHAW M. J. P.
Published: February 2008

Alate Aphis fabae from field infestations on beans and sugar beet were tested for flight before parturition and divided into migrants, flyers and non‐flyers. More alatae were produced, fewer nymphs were deposited before flight and the proportions of migrants among alatae increased with population density on each of the three crops. After the population peak, proportions of migrants decreased, more interforms were produced and more nymphs were deposited before flight.
Effects of population density on alienicolae of Aphis fabae Scop.: V. Variations in size, relative wing length and numbers of antennal sensorla of field alatae
Authors: SHAW M. J. P.
Published: February 2008

Size, relative wing length and numbers of antennal sensoria of alate Aphis fabae caught in a suction trap 12.2 m above ground and of migrants, flyers and non‐flyers among alate A. fabae from field infestations on beans and beet are compared. The size of aphids in successive samples decreased throughout the period of colonization but, on average, beet aphids were bigger and broad bean aphids were smaller than field bean aphids. There were very few migrant alatae among the very large or the very small aphids from any of the crops, neither were aphids of these extreme sizes caught in the suction trap. Non‐flyers and beet aphids generally had relatively shorter wings than migrants and bean aphids respectively. The numbers of antennal sensoria differed more between aphids from the three crops than between classes of alatae from the same crop, although trap aphids, presumed to be migrating from field beans had more sensoria than alatae taken from that crop. The mean dry mass of flyers was usually less than that of migrants of a similar size, although if the mass of nymphs deposited before flight is added, it is apparent that a flyer would be heavier than a migrant of the same size at maturity. This additional mass is thought to be due to increased development of the embryos in the ovarioles of flyers at this time and indicative of their greater adaptation for reproduction.
Fluctuations in populations of wheat bulb fly (Leptohylemyia coarctata) at Rothamsted
Authors: BARDNER R. , FLETCHER K. E. , JONES MARGARET G. , LOFTY J. R.
Published: February 2008

Several field experiments at Rothamsted have rotations including plots fallowed before sowing to winter wheat each year, which provide ideal conditions for maintaining infestations of wheat bulb fly (Leptohylemyia coarctata). In eight consecutive years of one experiment, a mean of 13% of the eggs laid on fallows in these rotations eventually survived to become adults. There was a considerable variation between years, ranging from a maximum survival of 28 % to a minimum of 7%. Most deaths occur in the larval stage, and although previous work showed that survival of the larvae increases with the number of shoots available for infestation, much of the variability in survival rates between seasons was apparently caused by other factors, possibly climatic.

Eggs laid in fallows were sampled in most years from 1953 to 1972. They varied from 3.57 to 0.02 million/acre (8.81–0.05 million/ha), depending on the season and site; the mean was 1.08 million/acre (2.67 million/ha). Egg populations varied in synchrony at all the three sites studied; there were cycles lasting several years between peaks of abundance or scarcity but there was no consistent tendency for populations to increase or decrease. Fewest eggs were laid when the weather was cold and wet during July and August, i.e. when adults are active. Weather was more closely correlated with the number of eggs laid expressed as a fraction of those laid in the previous year (net reproductive rate) than with the number of eggs laid/acre.
The influence of powdery mildew (Erysiphe graminis) infection on the development of four spring wheats
Authors: LUPTON F. G. H. , SUTHERLAND JENNIFER
Published: February 2008

Infection with Erysiphe graminis reduced the weight of the roots and aerial parts of four wheat cultivars of contrasting susceptibility at the three‐leaf stage. It had little effect on the more resistant varieties at the five‐leaf and flag‐leaf stages. When 14C was supplied to the youngest fully expanded leaves at successive stages of growth, the proportion recovered from the roots, and that translocated to other tillers when present, was reduced, especially in the more susceptible cultivars.
Sites of contamination and numbers of Erwinia carotovora present in stored seed potato stocks in Scotland
Authors: PÉROMBELON M. C. M.
Published: February 2008

Forty‐eight bulk and crate stored commercial seed potato stocks from the east of Scotland were examined for contamination by Erwinia carotovora in 1967 and 1968. Both E. carotovora var. carotovora and E. carotovora var. atroseptica were present, the latter, the blackleg pathogen, being detected four times more frequently. Most contamination was located on the tuber surface and in the lenticels; it was rare in the vascular ring and the organism was never detected in the cortex. The level of contamination of lenticels was only slightly affected after winter storage, which, however, substantially reduced surface contamination. More than 103 cells were detected on the surface of tubers in over half the stocks and in half the stocks each lenticel sampled contained more than 102 bacteria.
Control of potato cyst‐nematode, Heterodera rostochiensis, in three soils by small amounts of aldicarb, Du Pont 1410 or Nemacur applied to the soil at planting time
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Aldicarb or Du Pont 1410 (S‐methyl 1‐(dimethylcarbamoyl)‐N‐[(methylcarbamoyl) oxy] thioformimidate) at 2.6–11.2 kg a.i./ha applied to the soil at planting time controlled potato cyst‐nematode, Heterodera rostochiensis, in sandy loam, peaty loam and silt loam and greatly increased tuber yields of susceptible potatoes. Nemacur (O‐ethyl‐O‐(3‐methyl‐4‐methylthiophenyl) isopropylamido‐phosphate) controlled potato cyst‐nematode in sandy loam at 2.9–10.3 kg a.i./ha and in silt loam at 11.2 kg a.i./ha but did not control the nematode well in peaty loam even at 22.4 kg a.i./ha. In peaty loam aldicarb and Nemacur were more effectively incorporated by rotavation than by a modified power harrow.
Growth regulatory effect of three benzimidazole fungicides on the germination of celery (Apium graveolens) seeds
Authors: THOMAS T. H.
Published: February 2008

Seeds of four celery cultivars did not germinate when incubated in buffered solutions in the dark at 22 °C. This high‐temperature‐induced dormancy was broken with either of the systemic fungicides benomyl or BAS 3460 F (mainly methyl‐2‐benzimidazole carbamate) when used in combination with a mixture of the gibberellins A4 and A7 (GA4/7). The fungicide thiabendazole was ineffective in these tests.
Observations on different methods of aphid trapping
Authors: A'BROOK JOHN
Published: February 2008

Cylindrical and horizontal sticky traps painted in a range of spectral colours were used to determine the flight and landing behaviour of aphids. Data are also presented on aphid catches in suction traps at two heights and in light traps. Apart from colour sensitivity (yellow versus white) there was apparently a separate response to colour which in some species varied with season. Within yellow‐sensitive species there was also a differential response to colour. With the experimental methods used, it was not possible to define mathematically the active and passive landing components on cylindrical traps. Though the active landing component was large it varied between aphid species. Most species caught on horizontal traps at ground level had been flying above 1 m. In some species the response of males to colour and their landing behaviour differed from that of viviparae and oviparae.

Four years data from suction traps suggest that aphid species can be divided into three categories on the basis of the height at which they normally fly. One group, mostly tree‐feeders, always show the greatest density at a high level (12.2 m) throughout the season. The second group always have the highest density at a low level (1 m) whilst a third group of species change at a specific date each autumn from a maximum density at 1–12.2 m. Attraction to light (moth trap) appeared to be linked with the grouping of species by height of flight. The interpretation of catch data is discussed in the light of these observations.
The field behaviour of seed‐borne Ascochyta fabae and disease control in field beans
Authors: HEWETT P. D.
Published: February 2008

In field sowings at Cambridge 2–15% of field bean seeds carrying Ascochyta fabae produced seedlings with leaf lesions. The fungus spread for distances up to 10 m in an average season and usually infected the new crop of seed. The amount of such infection arising from a single lot varied widely when samples were grown at different centres, presumably because of differences in local weather conditions.

Seed lots with approximately 1% infected seeds seem suitable for ware crop production but little or no A. fabae can be tolerated in seed intended for multiplication. Infection in British‐grown commercial seed has been greatly reduced by the selection of clean seed. Health standards adopted in the Field Bean Seed Scheme may have eliminated A. fabae from one cultivar.
The biology of Puccinia chondrillina a potential biological control agent of skeleton weed
Authors: HASAN S. , WAPSHERE A. J.
Published: February 2008

During investigations on the parasites of Chondrillajuncea in the Mediterranean region, the rust, Puccinia chondrillina, was found to be one of the most damaging. This macrocyclic and autoecious rust which is specific to the genus Chondrilla, remains active throughout the year and attacks all stages and all parts of the plant. In the Mediterranean region the rust appears to multiply solely by the uredo‐stages and the teleutospores produced at the end of the summer have no obvious role in the life‐cycle of the fungus. The uredospores germinated at temperatures of 0–36 °C and were used for inoculation of Chondrilla seedlings in the greenhouse.

The rust occurs from the cold continental climates of southern Siberia to the hot, Mediterranean ones of Portugal and North Africa. In many situations the rust has been found to play an important role in the reduction of C. juncea populations. Young seedlings were highly susceptible to attack and were often destroyed. Older rusted plants gave many fewer viable seeds than healthy plants and were also often unable to produce new rosettes from their roots.
Some properties of chrysanthemum stunt, a virus with the characteristics of an uncoated ribonucleic acid
Authors: HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Grafting to virus‐free Mistletoe chrysanthemums was the most reliable method of detecting the chrysanthemum stunt agent, but specific light and temperature conditions were required for the diagnostic ‘measles’ symptoms to develop. Although stunt agent was highly infectious, leaf‐rubbing inoculations with chrysanthemum sap gave erratic results. Colorimetric and electrophoretic tests were unreliable for indexing chrysanthemums.

Stunt agent infected eight of twenty‐nine species in the family Compositae, but none of 116 species in forty‐seven other families. Stunt spread rapidly by foliage contact and by handling plants, but dipping the hands in 2% trisodium orthophosphate when handling plants increased the amount of spread. Stunt agent was not transmitted by four species of aphids, the glasshouse redspider mite, dodder (Cuscuta campestris) or through chrysanthemum seed.

Stunt agent withstood 10 min at c. 98 °C and dilution to 10‐4, was not pelleted by ultracentrifugation, and was inactivated by RNase in weak, but not strong, buffer, suggestive of an uncoated RNA ‘viroid’. Partially purified preparations were made by homogenizing frozen chrysanthemum leaves in 0.5 m phosphate buffer with antioxidant at c. 2 °C, and clarification by n‐but‐anol and chloroform, followed by centrifugation. Highly infective RNA was precipitated from the supernant fluid by 2.5 vol. cold ethanol, and resuspended in a small volume of buffer.

The u.v. absorption spectra of infective preparations and the u.v. absorbance profiles of density‐gradients, were very similar to those of preparations from healthy chrysanthemum. Infective partially purified preparations of stunt agent withstood exposure to 2% formaldehyde or tri‐sodium orthophosphate, u.v. irradiation, and sonication. Stunt preparations contained no virus particles recognizable by electron microscopy, gave no distinct peak on analytical ultracentrifugation, and did not consistently contain any specific antigen. Although similar to the ‘viroids’ potato spindle tuber and citrus exocortis, stunt agent did not infect Citrus limon, Gynura aurantiaca or tomato.
Identification, purification and some properties of a mosaic virus of okra (Hibiscus esculentus)
Authors: GIVORD L. , HIRTH L.
Published: February 2008

In the Ivory Coast, an apparently undescribed virus was isolated from okra (Hibiscus esculentus) in which it caused mosaic and leaf vein banding. The virus was sap transmissible to a wide range of plants and had a thermal inactivation point of 80 °C. It was named okra mosaic virus (OMV). A purification procedure was developed. Electron microscopy and analytical and density gradient centrifugation showed that OMV was an isometric virus accompanied by empty shells (top component). Serological tests showed OMV to be a member of the tymovirus group.
Effect of sowing date on incidence of Sudanese broad bean mosaic virus in, and yield of, Viciafaba
Authors: SALIH H. S. ABU , ISHAG H. M. , SIDDIG S. A.
Published: February 2008

Delaying the sowing of irrigated field beans in the Sudan after October greatly lowered the yield of seed, and increased both infestation by aphids and the incidence of Sudanese broad bean mosaic virus (SBBMV). Yield per plant was positively correlated with number of pods, but negatively with percentage infection with SBBMV. In greenhouse conditions, SBBMV was readily acquired from diseased plants and inoculated to healthy plants in 5 min feeding periods by both Aphis craccivora and Acyrthosiphon sesbaniae.
The influence of seedling age and development on the infection of lettuce by Bremia lactucae
Authors: DICKINSON C. H. , CRUTE I. R.
Published: February 2008

Laboratory methods are described for the culture and observation of Bremia lactucae on lettuce.

Mycelial growth of the fungus within the cotyledons of the cultivar Cheshunt Early Giant progressed to a minimum density at which sporulation occurred, and then continued to a maximum density coinciding with peak sporulation. The timing and intensity of sporulation was influenced by the concentration of the inoculum. Seedlings often became systemically infected and this, together with intensity of sporulation, was a good indicator of fungal growth and hence host susceptibility.

The severity of disease development on four susceptible lettuce cultivars (Cheshunt Early Giant, Paris White, Trocadero Improved and Crackling Ice) decreased with age and development of the seedlings at inoculation. The reasons for this are discussed.
Moulding of sugar‐cane bagasse and its prevention
Authors: LACEY J.
Published: February 2008

When fresh sugar‐cane bagasse containing about 50% water and 3% sugar was baled and stacked, it quickly heated to over 50°C and remained hotter than 40°C for 50 days. The residual sucrose was utilized by microbial growth and the content of fungal, bacterial and actinomycete spores increased to more than 108/g dry wt. The spores in heated bagasse were mostly of thermophilic actinomycetes and fungi, and included two actinomycetes implicated in bagassosis. Thermoactinomycetes sacchari occurred in 40% of samples examined, some of which yielded up to 5 × 106 colonies/g, while T. vulgaris occurred in 80% of samples, but these rarely yielded more than 105 colonies/g. Other organisms were cellulolytic and caused fibre deterioration. Heating and moulding could be much decreased either by drying to about 25% water content, which halved the spore content after storage, mostly at the expense of the actinomycetes, or by adding 2% by weight of propionic acid, which decreased the spore content to 4 × 106 spores/g or less even after 18 months' storage. Sometimes adding only 0·6% of propionic acid or 2% of propionic acid applied as a 50% aqueous solution had a similar effect. Treatment with propionic acid thus decreased the deterioration of bagasse, permitted its storage between harvests and prevented the hazard of bagassosis to workers.
Notes for Speakers at Scientific Meetings
Authors: Keyworth W. G.
Published: February 2008

The Council of the Association of Applied Biologists is concerned about the standards of presentation and illustration of some papers at meetings of the Association. The following notes have therefore been drawn up to emphasize those points which are considered to require special attention and to assist speakers to present their talks effectively.

These notes may be copied in whole or in part without further permission.
The effect of nematicides, applied to the seed rows in spring, on growth and yield of sugar beet in Docking‐disorder‐affected fields
Authors: COOKE D. A. , DUNNING R. A. , WINDER G. H.
Published: February 2008

Both Trichodorus spp. and Longidorus spp. damage roots of sugar‐beet seedlings in sandy soil, causing Docking disorder. Trials in infested fields between 1969 and 1972 tested the effects of fumigation along the rows with different amounts of D‐D or Telone applied either two weeks before sowing or immediately before sowing, application of the systemic nematicide aldicarb (Temik) in the furrow with the seed during sowing, and top‐dressing with nitrogen. Seedling establishment was often decreased by fumigation immediately before sowing, especially when followed by excessive rainfall, but only rarely by earlier fumigation or by aldicarb; differences in numbers of roots harvested were smaller because hand‐singling removed excess seedlings. There was usually little difference between the yield increases given by the most effective treatments, which were aldicarb at 1·12 kg active ingredient/ha and 2·2–6·6 ml D‐D or Telone/m of row at either time of application. Nitrogen top‐dressing never affected sugar yield significantly. Longidorus spp. and Trichodorus spp. were both controlled well in the fumigated row but much less well at 13 cm, and not at all at 25 cm from the row (i.e. mid‐way between two treated rows).
Insect vectors of cowpea mosaic virus in Nigeria
Authors: WHITNEY W. K. , GILMER R. M.
Published: February 2008

A yellow strain of cowpea mosaic virus (CPMV) was transmitted in cowpea by two thrips, Sericothrips occipitalis and Taeniothrips sjostedti; two chrysomelid beetles, Ootheca mutabilis and Paraluperodes quaternus; a curculionid beetle, Nematocerus acerbus; and two acridid grasshoppers, Catantops spissus spissus and Zonocerus variegatus. Summarizing trials with single insects, the efficiency of transmission of CPMV averaged 18—21% for N. acerbus and the two grasshoppers, 55% for P. quaternus, and 71% for O. mutabilis. Twenty‐two and 40% of the plants exposed to large populations of S. occipitalis and T. sjostedti, respectively, were infected. In three trials with an aphid, Aphis craccivora, 4 of 49 plants were infected with CPMV, but these infections were considered spurious because no infections occurred in any of 63 plants exposed to this insect in four other trials. A coreid bug, Riptortus dentipes, did not transmit CPMV. Mosaic symptoms in infected plants appeared 5—39 days after they were exposed to vectors. Infective virus was recovered from fresh faecal pellets of each grasshopper vector.
Taxonomic patterns in the host ranges of viruses among grasses, and suggestions on generic sampling for host‐range studies
Authors: WATSON L. , GIBBS A. J.
Published: February 2008

Analyses of published host‐range data for certain viruses reveal correlations with taxonomic groupings of grasses. Barley yellow dwarf virus (BYDV), cocksfoot mottle and phleum mottle viruses are found to have infected greater proportions of the festucoid grasses than of the non‐festucoids to which they were inoculated. By contrast, all strains of sugarcane mosaic virus (SCMV) and of the closely related maize dwarf mosaic virus (MDMV) infected more non‐festucoids than festucoids. In addition, infected plants from grass groups containing higher concentrations of genera susceptible to BYDV, SCMV and MDMV usually show clear symptoms, whereas infected plants from less susceptible groups are frequently symptomless. Some viruses, such as barley stripe mosaic, brome mosaic, cocksfoot streak and ryegrass mosaic, show no apparent preferences for particular grass groups.

Samples of grasses employed in host‐range studies are usually strongly biased towards festucoids. It is suggested that viruses ought to be adequately tested against genera from all the major groups, and a classified list of grass genera suitable for host‐range studies is provided.
The four dimensions of cereal aphids
Authors: Dean G. J.
Published: February 2008

For most of this century, aphids have been known to infest cereals, but their potential importance does not seem to have been fully appreciated until the early 1950s when they were found to be vectors of barley yellow dwarf virus (Bruehl, 1961). Although this discovery initiated a great deal of research in many countries, especially in North America, very little was done, or thought necessary to be done, in Britain. In 1968, however, some of this complacency was lost when the large numbers of aphids found on the cereals in this country indicated how little was known about them and their effects. Aphids are part of a complex four‐dimensional continuum of time and space, and this paper briefly describes some of the results obtained since 1969.
Properties and isolates of barley yellow dwarf virus
Authors: Plumb R. T.
Published: February 2008

Barley yellow dwarf virus is persistently transmitted by a number of aphid species of which three, Rhopalosiphum padi, Sitobion avenae and Metopolophium dirhodum, are common in most years. Other aphids may be locally important. Isolates of the virus differ in their virulence and geographical distribution and are not transmitted equally well by all aphid vectors. Isolates with similar properties are grouped into strains according to their transmission by vectors and their severity. Changes in strain and aphid occurrence from year to year alter the incidence of virus and its effect on yield. These changes emphasize the need for detailed knowledge of cereal aphid biology and epidemiology of BYDV before effective control can be used.
Effects of gangrene (Phoma exigua) on potatoes
Authors: GRIFFITH R. L. , HIDE G. A. , HIRST J. M. , STEDMAN O. J.
Published: February 2008

Seed tubers of the varieties King Edward, Majestic and Pentland Crown selected as ‘clean’ (lesion‐free), moderately, or severely affected by gangrene lesions were planted in field experiments. Infection delayed plant emergence, increased the number of stems/plant, sometimes caused gaps in crops and was associated with increased blackleg. On average severely affected seed yielded 20% less than ‘clean’ seed. Seed infection also increased the proportion of tubers in smaller size grades so that crops from severely infected King Edward seed averaged 1·4 ton/acre (3·5 t/ha) less small ware and 2·5 ton/acre (6·3 t/ha) less large ware than ‘clean’ seed. With Majestic, small ware was increased (0·7 ton/acre (1·8 t/ha)) and large ware decreased (4·4 ton/acre(11·0 t/ha)); Pentland Crown was similarly affected (small ware increased 0·8 ton/acre (2·0 t/ha); large ware decreased 3·9 ton/acre (9·8 t/ha)). In eight of twelve experiments unselected diseased stocks yielded significantly less than ‘clean’ tubers.

Other experiments compared seed stocks with different proportions of gangrene‐infected seed tubers. Yields decreased as the proportion of diseased seed tubers increased, but differences were significant only when more than 60% were affected. Surprisingly, yields from ‘clean’ tubers also decreased as the proportion of diseased tubers increased in the stocks from which they were selected.

Gangrene on progeny tubers after storage was not always related to the amount of gangrene visible on the seed. It was increased by riddling or wounding and decreased by dipping tubers in organo‐mercury fungicide before or soon after wounding.
A rapid method for measuring production of yellow rust spores on single seedlings to assess differential interactions of wheat cultivars with Puccinia striiformis
Authors: JOHNSON R. , BOWYER D. E.
Published: February 2008

Uredospore production of Puccinia striiformis in single wheat seedlings was assessed by weighing spores on an electrical microbalance, by counting on a haemocytometer or by measuring turbidity of spore suspensions with a spectrophotometer and compared with production from groups of seedlings determined by weighing spores on an analytical balance. The data were used to assess differential interaction of wheat cultivars Hybrid 46 and Joss Cambier with two isolates of race 104 E137 of P. striiformis and cvs Maris Templar and Joss Cambier with two isolates of race 41 E136. A significant differential interaction was shown in both experiments by each method but most rapidly and with the minimum of materials by the single‐plant microbalance technique. Measurements of spore production demonstrated differences between isolates within races more clearly than the conventional visual assessment of yellow rust symptoms.
Intra‐racial variation in Phytophthora infestans and adaptation to field resistance for potato blight
Authors: CATEN C. E.
Published: February 2008

Strains of Phytophthora infestans of the same race (P4) isolated from a range of R0 potato varieties differed markedly in their rate of growth on agar but differences in growth rate were not related to variety of origin. Two isolates from each of the varieties Duke of York, Majestic and Arran Consul were grown for six successive subcultures on tubers of these three varieties. The six isolates differed in aggressiveness as shown by their growth on individual varieties. There was a marked difference in growth rate between alternate subcultures which is attributed to the use of too long an incubation period. Analysis of the data for subcultures 1, 3 and 5 revealed a significant interaction between isolates and varieties which reflected the enhanced growth of five of the isolates on the variety from which they had been obtained. Serial subculture on potato tubers of the same variety had no general or specific effect on the aggressiveness of the isolates. It is concluded that strains of P. infestans of the same race may be differentially adapted to the variety on which they are growing in the field. Differential interactions between pathogen biotypes and non‐immune hosts are considered to be widespread in host‐pathogen systems.
Association of different kinds of bacilliform particle with vein chlorosis and mosaic diseases of raspberry (Rubus idaeus)
Authors: JONES A. T. , ROBERTS I. M. , MURANT A. F.
Published: February 2008

Thin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)‐resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particles c. 430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner core c. 25–30 nm in diameter with cross‐banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV.

Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particles c. 125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the particles.
Purification of maize streak virus and its relationship to viruses associated with streak diseases of sugar cane and Panicum maximum
Authors: BOCK K. R. , GUTHRIE E. J. , WOODS R. D.
Published: February 2008

Maize streak virus (MSV) was purified by homogenising infected leaf tissue in 0·01 m pH 3·9 phosphate buffer and clarifying the extract with n‐butanol (7 ml/100 ml extract). Purified preparations contained particles 20 nm in diameter, some occurring singly, but most occurring in pairs, forming structures of 30 × 20 nm. The sedimentation coefficients of single and paired particles were 54 and 76 S respectively.

When centrifuged in sucrose density gradients preparations made by extracting leaves at pH 3·9 gave a single intense light‐scattering zone containing paired particles. Preparations made at pH 5·9 or 7·9 gave one or two additional upper zones containing single particles and fragmented material. Preparations treated with 0·05 or 0·1 m ethylene diamine tetra‐acetic acid, disodium salt, (EDTA) contained no paired particles, few single particles and much fragmented material. In immunoelectrophoresis, the major component in preparations without EDTA migrated to the cathode whereas that in EDTA‐treated preparations migrated to the anode.

Virus isolates from streak‐diseased sugarcane and guinea grass (Panicum maximum) were serologically related to MSV and had similar particles with identical sedimentation coefficients. No such particles were seen in purified preparations of healthy maize, sugarcane, or guinea grass. The viruses from sugarcane and guinea grass are probably host‐adapted and are referred to correctly as the sugarcane and guinea grass strains of MSV.

MSV probably contains single‐stranded RNA, and the cryptogram is (R)/1:*/*:S/S:S/Au.
Susceptibility of plants to attack by wireworms (Agriotes spp.)
Authors: GRIFFITHS D. C.
Published: February 2008

In laboratory tests, larvae of Agriotes spp. were presented with a choice between seedlings of test plants, and of wheat, which is known to be susceptible. Some plants, e.g. onion, were as susceptible as wheat to wireworm attack whilst others (mustard, cabbage, French marigold, clover and flax) were less often attacked, partly because they are small and are shallow sown. All pea and bean plants exposed to wireworms were attacked but most tolerated attack and continued to grow.