bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of permethrin sprays on the mite fauna of apple orchards
Authors: KAPETANAKIS E. G. , WARMAN T. M. , CRANHAM J. E.
Published: February 2008

In two apple orchard trials, single high volume sprays of 25–50 mg permethrin/ litre greatly reduced numbers of the phytosend predatory mite Typhlodromus pyri whether the spray was timed pre‐bloom at growth stages from ‘bud‐burst’ to ‘late green cluster’ or post‐bloom in June. At ‘bud‐burst’T. pyri were partially protected in hibernating sites on the bark, but the lethal effect of the spray was only delayed; no appreciable selectivity could be obtained by this early timing. Bioassays showed that the persistent toxicity of permethrin residues on bark or on leaves declined to a low level within 20 days, and was related to the decline in residue levels determined by G.C. analyses. Residues were detectable for 3 months or longer. Resurgence of spider mites, Panonychus ulmi, occurred within 2 months after all spray timings, and effective predation by T. pyri was only fully re‐establised after several months. In one trial, apple rust mite, Aculus schlechtendali also increased when T. pyri was reduced by spraying. Tydeid mites were killed by permethrin.
Transmission characteristics and some other properties of bean yellow vein‐banding virus, and its association with pea enation
Authors: Virus Mosaic , COCKBAIN A. J. , JONES P. , WOODS R. D.
Published: February 2008

Bean yellow vein‐banding virus (BYVBV) has been found occasionally in mixed infection with pea enation mosaic virus (PEMV) in spring‐sown field beans (Vicia faba minor) in southern England. Glasshouse tests confirmed that, like PEMV, BYVBV is transmissible by manual inoculation and by aphids in the persistent manner. However, BYVBV can be transmitted by aphids only from plants that are also infected with a helper virus, usually PEMV. Thus after separation from PEMV by passage through Phaseolus vulgaris it was no longer aphid‐transmissible. It became aphid‐transmissible again only after re‐mixing in plants with PEMV or with a substitute helper, bean leaf roll virus (BLRV). It was not transmitted by aphids that fed sequentially on plants singly infected with PEMV and BYVBV. Thus the interaction between BYVBV and PEMV (or BLRV) that enables BYVBV to be transmitted by aphids seems to occur only in doubly infected plants. However, it was not transmitted by aphids from plants doubly infected with BYVBV and broad bean wilt virus (BBWV). BYVBV and PEMV were transmitted more readily by Acyrthosiphon pisum than by Myzus persicae; neither virus was transmitted by Aphis fabae.

Phenol extracts of BYVBV‐infected leaves were more infective than phosphate buffer or bentonite‐clarified extracts and were sometimes infective when diluted to 1/1000. The infectivity of BYVBV in phosphate buffer extracts of leaves singly infected with BYVBV, unlike that in extracts of leaves doubly infected with BYVBV and PEMV (or BLRV), was destroyed by treatment with organic solvents. BYVBV infected 11 of 28 plant species that were inoculated with phenol extracts; seven of the infected species were legumes. No transmission of BYVBV was detected through seed harvested from infected field bean plants. Isometric particles c. 30 nm in diameter were seen in extracts of plants doubly infected with BYVBV and PEMV but not in extracts of plants infected with BYVBV alone. Leaves of plants infected with BYVBV, alone or with PEMV, contained membrane‐bound structures c. 50–90 nm in diameter associated with the tonoplast in cell vacuoles. These structures were not found in healthy leaves.

BYVBV has several properties in common with other known aphid‐borne viruses that are helper‐dependent and transmitted in a persistent manner. Possibly, as suggested for some of them, aphid transmission of BYVBV depends on the coating of its nucleic acid with helper virus coat protein.
Studies on melon necrotic spot virus disease of cucumber and on the control of the fungus vector (Olpidium radicale)
Authors: TOMLINSON J. A. , THOMAS B. J.
Published: February 2008

Melon necrotic leaf spot virus (MNSV) caused a major outbreak of a leaf necrosis disease of hydroponically‐grown cucumber plants at Humberside in 1983. The virus had c. 33 nm diam. particles which reacted serologically with MNSV antiserum of Dutch or American origin. Virus particles, which contained a single polypeptide (mol. wt 45 × 103) and a presumed RNA species (mol. wt 1.5 × 106), had a sedimentation coefficient (s20.w) of 134 S and a buoyant density in caesium chloride of 1.35 g/cm3. The virus was mechanically transmissible, confined to species of Cucurbitaceae, transmitted by zoospores of Olpidium radicale and retained in the resting spores of the fungus. MNSV is thus both water‐borne and soil‐borne.

O. radicale zoospores were killed in <5 min in suspensions containing 20 μg/ml of the surfactant Agral (alkyl phenol ethylene oxide). The disease did not reappear in 1984 when the cucumber crops were fed with nutrients containing 20μg/ml Agral.
The effect of resistant potato cultivars on a field population of Globodera pallida Pa2 over three years of cropping
Authors: ANDERSON J. A. D.
Published: February 2008

Six potato cultivars with different levels of resistance to the white potato cyst nematode (PCN) Globodera pallida Pa2 were grown for three seasons in field plots to which G. pallida Pa2 cysts had been introduced earlier. There were two planting times, corresponding to early and maincrop commercial planting times, and two initial PCN population densities, high and low.

The effect of cultivar on PCN population density was far greater than the effect of planting time or initial nematode population. The final PCN populations for the cultivars Ilam Hardy, Wha, 4696A(2), Sovereign, D40/6 and V390 were 151, 74, 27, 1.4, 0.2 and 0.06 eggs per g of soil respectively.

It is concluded that resistant potato cultivars can be very effective in controlling G. pallida Pa2 in the field.
The effect of Heterodera avenae, on the root system of susceptible and resistant oat seedlings
Authors: RAWSTHORNE DENISE , HAGUE N. G. M.
Published: February 2008

The effects of invasion by the cereal cyst nematode, Heterodera avenae, on the root growth of susceptible and resistant oat seedlings were similar. Nematode invasion directly inhibited root extension and lateral root production, which was dependent upon the developmental status of the invaded root tissue and the nematode density cm‐1 root. Both responses are caused by mechanical damage due to nematode invasion leading to decreased top growth in the host. Reduced root development, decreased efficiency of water and nutrient uptake in invaded plants being indirect effects of nematode invasion.
Superoxide dismutase polymorphism in field populations of the potato cyst nematodes Globodera rostochiensis and G. pallida
Authors: FOX P. C. , FINNEMORE T. W. , ATKINSON H. J.
Published: February 2008

Superoxide dismutase (SoDase) polymorphism in reference populations of potato cyst nematodes (PCN) was studied by isoelectric focusing and compared with the banding pattern obtained from 26 English field populations of PCN. Qualitative and quantitative differences were found between the reference populations: a band detected only in the G. rostochiensis Ro4 and Ro5 reference populations was found in four field populations of varying pathotype composition and two field populations of G. rostochiensis Rol possessed extra bands that were not detected in the other field populations. Analysis of the band differences showed little correlation between pathotype and banding pattern in the field populations.
The relationship between the rate of entry of ioxynil and effects on photosynthesis in normal and drought‐stressed Stellaria media
Authors: MERRITT C. R.
Published: February 2008

The entry of 14C‐labelled ioxynil octanoate into leaves of Stellaria media has been measured for plants grown in dry or moist soil. Of the total herbicide applied, 1–3% entered the leaf by 24 h and 2–5% by 72 h after treatment. Entry into moist‐grown plants proceeded at about twice the rate of that into drought‐stressed plants. Despite the limited rate of entry, the inhibitory action of ioxynil octanoate on photosynthetic carbon dioxide exchange was rapid, inhibition within 24 h reaching 70–90% in moist‐grown plants, and 30–70% in dry‐grown plants. Plants grown under moisture stress contained greater concentrations of the pigments chlorophyll a, carotene and lutein (a xanthophyll) than did moist‐grown plants, and ioxynil‐induced breakdown of these pigments was more rapid in moist‐grown plants. It is suggested that these factors contribute to the greater tolerance of drought‐stressed S. media to applications of ioxynil octanoate.

The importance of continuous measurements of herbicide action is discussed in relation to the value and interpretation of 14C uptake data.
Interactions between fungicide, plant growth regulator, nitrogen fertiliser applications, foliar disease and yield of winter barley
Authors: JORDAN V. W. L. , STINCHCOMBE G. R.
Published: February 2008

Leaf size and foliar disease in winter barley increased with increasing total amounts of nitrogen applied to the crop: flag leaf areas increased at an average of 10% per 35 kg N ha‐1 Nitrogen top dressing applied in mid‐March (G.S. 31) resulted in larger leaves, more foliar disease, more straw, delayed ear emergence, fewer grains ear‐1 and less grain yield than nitrogen applied in mid‐April (G.S. 31). Application of chlormequat at G.S. 30 gave a variable response, but overall it increased fertile stems m‐2 and crop yield and decreased crop height but had no significant effect on straw yield. Fungicide treatments suppressed foliar disease and improved yield. Yield responses were greater when plant growth regulator and mid‐March nitrogen had been applied at sites where more disease prevailed than with April‐applied nitrogen. In one of the field experiments, on cv. Sonja, delaying the main nitrogen application until April, without fungicide treatment, gave a similar yield to that provided by nitrogen in March with two or three fungicide sprays.
Longevity, fecundity, change in degree of gravidity and lipid content with adult age, and lipid utilisation during tethered flight of alates of the corn leaf aphid, Rhopalosiphum maidis
Authors: LIQUIDO NICANOR J. , IRWIN MICHAEL E.
Published: February 2008

The longevity, daily fecundity, degree of gravidity and lipid content of alates of varied ages, and lipid utilisation during sustained tethered flight of the corn leaf aphid, Rhopalosiphum maidis, were studied. Alates had a mean longevity of 9.7 days and a mean fecundity of 14.9 nymphs. A significant increase in the lipid content of alates before emerging as adults was observed. Newly emerged and half‐day‐old alates had more lipid reserve and embryos than 1‐, 2‐, 4‐, 8‐, and 16‐day‐old specimens. The lipid content of alates decreased significantly with age. The alates' degree of gravidity and lipid content had a low but significant correlation.

Half‐ to 1‐day‐old alates flew readily and could fly for much longer durations than 2‐ and 4‐day‐old. Eight‐day‐old alates were not capable of flight. R. maidis utilised lipid during prolonged tethered flight. Our data suggest that there is a threshold point when alates cease utilising stored lipid as the energy source and start utilising non‐lipid sources as flight fuel energy.
Modelling adult survival in the laboratory of diapause and non‐diapause Colorado beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) from Normandy, France
Authors: BARTLETT PAUL W. , MURRAY ALISTAIR W. A.
Published: February 2008

Adult Leptinotarsa decemlineata from a culture originally from Normandy, France were kept in a controlled environment and fed daily on potato foliage. Dead beetles were scored and removed. Setting up the experiment was spread over 212 days and 1135 beetles were used. After 21 days each group was divided into two, some remained active and others were induced to diapause for 221 days before becoming active once again. Life span varied from 1 to 504 days and could be extended to 770 days by diapause. A model was derived which describes the mortality over time by assuming that a proportion of the population had an exponential distribution of lifetime and the remainder had a Weibull distribution which allowed for a hazard rate increasing with time. In the model 17% were short‐lived, having a mean lifetime of 8 days, and the remainder were long‐lived having a mean lifetime of 139.5 days. An exponential survivor function describes the post‐diapause cohort, which had a mean lifetime of 129 days after diapause.
Prevention of rice tungro virus disease and control of the vector with granular insecticides
Authors: SATAPATHY M. K. , ANJANEYULU A.
Published: February 2008

Thirteen granular insecticides were screened under glasshouse conditions for their ability to kill the vector, Nephotettix virescens, and to prevent tungro virus infection. Carbofuran, bendiocarb, isoprocarb, BPMC, disulfoton, mephosfolan and phorate caused 100% vector mortality, but only the first four reduced virus infection to an acceptable level; the remainder killing the vector too slowly to prevent virus transmission. Seven of these compounds were evaluated in the field on two test cultivars, Traichung Native 1 and Pankaj. Carbofuran, isoprocarb and BPMC gave acceptable control of the disease on both cultivars and diazinon on cv. Pankaj only.
Characterisation of populations of Sclerospora graminicola
Authors: BALL S. L. , PIKE D. J. , BURRIDGE C. Y.
Published: February 2008

Nine cultivars of pearl millet were inoculated with 12 collections of Sclerospora graminicola from various locations in Africa and India in a series of experiments which constituted an almost balanced incomplete block design spanning an entire growing season. The character of each pathogen population was defined in terms of incidence of disease on the hosts. Generally the pathogen collections from the sub‐Sahel regions of West Africa were more pathogenic than those from Senegal, Zambia or India. All but one host cultivar possessed relative resistance which decreased as the overall pathogenicity of the collections increased. There was one notable exception which exhibited stable resistance to all the pathogen collections tested and may have potential for future resistance breeding programmes.
Multiplication of corn stunt spiroplasma in Dalbulus maidis and transmission in vitro, following injection
Authors: ALIVIZATOS A. S. , MARKHAM P. G.
Published: February 2008

Corn stunt spiroplasma (CSS) multiplied in all injected Dulbulus maidis, reaching titres of over 1 × 106 colony forming units (cfu)/insect and 1 × 104 cfu/salivary gland of each insect. Spiroplasmas could be isolated from the haemolymph and from the salivary glands 1 h after injection and at any time subsequently. Insect extract at a concentration greater than the equivalent of 0.1 insects/ml was inhibitory to the growth of CSS in cultures.

Helices could be seen in the haemolymph at any time after injection. However, distorted or partially deformed cells and small aggregates were not present until 2–3 wk after injection. The salivary gland cells of injected insects contained membrane‐bound ‘pockets’ or ‘colonies’ packed with pleomorphic organisms, which included some filamentous forms. Intracellular colonies were always on the periphery of cells and were easily detectable by fluorescent microscopy. Both pleomorphic and filamentous forms were also seen intercellularly in the salivary glands.

Following injection, transmission of CSS to maize and to sterile feeding solution were compared using 1 day feeding periods. A proportion of injected leafhoppers began to transmit to maize by the third day following injection (5%) and reached a maximum of 72% by day 14. By day 9, 82% of the population had transmitted at least once to plants and by day 12, 100% had transmitted. Similar insects transmitted through membranes to sterile feeding solution on day 4 (3%) reaching a maximum of 62% by day 14.
Interaction of vesicular‐arbuscular mycorrhizal fungi and root knot nematode on cultivars of tomato and white clover susceptible to Meloidogyne hapla
Authors: COOPER KAREN M. , GRANDISONS G. S.
Published: February 2008

The interactive effects of vesicular‐arbuscular mycorrhizal (VAM) fungi and root‐knot nematode (Meloidogyne hapla) were studied on nematode‐susceptible cultivars of tomato (cv. Scoresby) and white clover (cv. Huia) at four levels of applied phosphate. The relative merits of simultaneous inoculation with mycorrhizal fungi and nematodes and of inoculation with mycorrhizal fungi prior to nematode inoculation were evaluated. Mycorrhizal plants were more resistant than non‐mycorrhizal plants to root‐knot nematode at all phosphate levels and growth benefits were generally greater in plants preinfected with mycorrhizal fungi. Nematode numbers increased with increasing levels of applied phosphate. In mycorrhizal root systems, nematode numbers increased in the lower phosphate soils; at higher phosphate levels nematode numbers were either unaffected or reduced. The numbers of juveniles and adults per gram of root were always lower in mycorrhizal treatments. Mycorrhizal root length remained unaffected by nematode inoculation.

Mycorrhizal inoculation thus increased the plants' resistance to infection by M. hapla. This was probably due to some alteration in the physiology of the root system but was not entirely a result of better host nutrition and improved phosphorus uptake by mycorrhizal plants.
Resistance to the aphid Metopolophium festucae cerealium: effects of the host plant on flight and reproduction
Authors: DENT D. R.
Published: February 2008

The levels of resistance present in two cereal and four grass hosts of M. f. cerealium were assessed in terms of the percentage of alatae flying from the host and reproductive rates of alatae. Festuca rubra and F. arundinacea exhibited highest levels of resistance, inducing a greater proportion of the alatae to fly (94% and 84% respectively) after producing only a few nymphs. Although between 38% and 64% of alatae flew from L. multiflorum, oats, L. perenne and wheat these alatae deposited more nymphs on the hosts before flight than occurred on Festuca. The weight of alatae did not influence the flight response.

The differences in the flight/reproductive response of M. festucae to various host plants are discussed in relation to possible host selection strategies of this species and to antixenotic/antibiotic host resistance experiments in general.
The use of multivariate morphometric methods in the separation of alate morphs of the rose‐grain aphid, Metopolophium dirhodum
Authors: HAND S. C.
Published: February 2008

A preliminary morphometric analysis of alate Metopolophium dirhodum was carried out. The alate morphs studied were: gynoparae and alate emigrants (collected from Rosa), summer exules (collected from maize in the field and from wheat in the laboratory) and winter exules (collected from grasses). Comparing the different morphs using canonical discriminant function analysis gave good separations (always in excess of 80% and often 100%). If this result is found to hold for specimens from a wider temporal and geographical range, it may be used to determine the sources of flying alatae, particularly spring colonists.
The movement and dispersal of Liriomyza trifolii (Diptera: Agromyzidae) in a chrysanthemum greenhouse
Authors: JONES VINCENT P. , PARRELLA MICHAEL P.
Published: February 2008

Investigation of the dispersal of Liriomyza trifolii in a 1–2 ha chrysanthemum greenhouse indicated that the average distance flown by female flies was greater than that flown by male flies. However, flies of both sexes were found at the furthest distance from the release point (102 m) which indicates that flies in the greenhouse could be considered to be a single inter‐breeding population. When the data were fitted to a generalised distance‐dispersal model, examination of the parameters revealed density decreased with distance more rapidly for males than females. Also, the model showed that males tended to be slightly more attracted to each other than were females. The applicability of these results to the development of pest management systems for L. trifolii is discussed.
Virulence of Bremia lactucae in Sweden and race‐specific resistance of lettuce cultivars to Swedish isolates of the fungus
Authors: GUSTAFSSON INGRID
Published: February 2008

Virulence surveys of Swedish Bremia lactucae populations confirmed that the virulence factors vl to v12 were present in high or very high frequencies. Virulence associated with recently defined new resistance genes was also present. Laboratory tests of lettuce cultivars and Lactuca accessions using different Bremia isolates and field tests with natural inoculum showed that previously undetected virulence factors were present.

Due to a lack of highly effective genes for specific resistance and the frequent sexual recombination of virulence genes it is suggested that any future breeding programmes concentrate on non‐specific resistance.
The phylloplane microflora of ripening wheat and effect of late fungicide applications
Authors: MAGAN N. , LACEY J.
Published: February 2008

Flag leaves and ears of spring wheat cv. Timmo (in 1980) and winter wheat cv. Maris Huntsman in 1981 and 1982 were colonised by a variety of micro‐organisms whose numbers increased rapidly between anthesis and harvest. The predominant mycoflora were yeasts, yeast‐like fungi and filamentous fungi which included Cladosporium spp., Verticillium lecanii, Alternaria alternata, Fusarium spp. and Epicoccum nigrum. Although similar species were isolated, their relative abundance on flag leaves and ears differed. The fungicide captafol was most effective as a protectant and significantly decreased populations of fungi on flag leaves and ears for 6 and 4 wk respectively, compared to untreated controls. Benomyl and Delsene M (carbendazim + maneb) were the most effective of the systemic sprays and formulations. In general, fungicides affected populations of yeasts, yeast‐like fungi and Cladosporium spp. most while Alternaria was tolerant of all treatments. Yields of winter wheat were increased in two seasons by an average 0–2 t ha‐1 (2–4%) following a single late fungicide treatment at G.S. 50 or 60 and 0–41 t ha‐1 (5‐1%) when this was combined with an early spray against foliar diseases (G.S. 38–40). Individual treatments increased yield by up to 12% with little difference between applications at G.S. 50 or 60. The yield benefit came mainly from increased 1000‐grain weights. Germination of the treated grain was increased only slightly.
Factors affecting bacterial black spot of mangoes caused by Xanthomonas campestris pv. mangiferaeindicae
Authors: MANICOM B. Q.
Published: February 2008

Bacterial black spot of mango caused by Xanthomonas campestris by. mangiferaeindicae was found to be essentially a wound pathogen of leaves under glasshouse conditions, with maximum infection occurring at a temperature regime of 22/26 oC (night/day). There were significant differences in leaf susceptibility among cultivars, cv. Sensation being less, and cv. Haden more susceptible than cvs Zill and Kent, which agrees with field observations of fruit infection.

The organism is a phylloplane resident year round in the field and inoculum levels in the tree canopy affect ultimate fruit infection. The major weather factor affecting fruit infection was rainfall which showed a significant correlation (r = 0–77) with levels of infection after allowing for an approximate 2 wk latent period.

Other significant correlations were with a wind/rain index (r = 0–73) and a storm index (r = 0–66). The correlation of disease with the duration of free water was non‐significant (r = 0–22).
Detection and characterisation of bean yellow mosaic virus in corms of Gladiolus grandiflorus
Authors: STEIN ADINA , SALOMON R. , COHEN J. , LOEBENSTEIN G.
Published: February 2008

Bean yellow mosaic virus (BYMV) could not be detected in corms of infected gladioli unless they were cut 6–60 days before testing. Detection after cutting was time‐ and temperature‐dependent, was restricted to the cut area, and varied among cultivars. Virus could be recovered from uncut corms after storage for over 2 yr at 6 oC. BYMV in corms could be detected by enzyme‐linked immunosorbent assay and by immunosorbent electron microscopy with antisera against a gladiolus isolate purified from gladiolus leaves or corms. It could not be detected in corms with antiserum against a lupin isolate which readily detected BYMV in gladiolus leaves. Protein subunits of corm‐BYMV banded in SDS‐PAGE as a single 31 000 dalton polypeptide, while leaf‐BYMV produced a major 34 000 and several smaller polypeptides. Both major polypeptides retained the different serological properties of their source virions but their peptide maps indicated a common origin. It is suggested that the smaller polypeptide from corm‐BYMV is a stable cleavage product of the intact leaf‐BYMV coat subunits. Corm‐BYMV, although lacking some of the antigenic properties of leaf‐BYMV, was still infective.
Hatching from cysts and egg sacs of Heterodera cruciferae and effects of temperature on hatching and development on oilseed rape
Authors: KOSHY P. K. , EVANS K.
Published: February 2008

Juveniles hatched readily from field cysts and very readily from eggs in egg sacs of Heterodera cruciferae, when exposed to oilseed rape root diffusate. They hatched very poorly, however, from white or brown females from which the above egg sacs had been removed. Some hatching occurred at 8 oC but much more occurred at12, 16, 20 and 24 oC, with most at 16 oC.

Development of juveniles in roots of oilseed rape occurred throughout the range 8–24 oC, and proceeded faster the higher the temperature. The basal development temperature was taken as 5 oC and the number of day degrees above this temperature required to reach each stage of development was calculated. From invasion of roots to the hatching of F1 juveniles required an average of 680 day degrees, but only 210 day degrees were required for the first appearance of egg sacs on adult females. On this basis, two consecutive generations of H, cruciferae would be possible on autumn‐sown oilseed rape in southern England, but the second would mature fully only after the crop was harvested. In Scotland, two consecutive generations could also occur but the second would be much less mature by harvest: only about 850 day degrees are available compared to almost 1100 in southern England. In practice, however, overlapping generations probably occur due to flushes of hatching of juveniles (i) at sowing, (ii) when soils warm up after winter and (iii) when the first generation completes its development.

The proportion of eggs found in egg sacs was never more than 37% and some field cysts contained about 220 eggs; their egg sacs may, therefore, have contained as many as 150 eggs. Any study of population dynamics or damage assessment will require a quantification of the contribution of eggs in egg sacs to population density. Oilseed rape is direct drilled and may, therefore, be more sensitive to a given population density of the nematode than host crops which are transplanted.
The effect of cold treatment during seed imbibition on lettuce radicle length and the uniformity of seedling emergence
Authors: FELLOWS JANE R. , WURR D. C. E.
Published: February 2008

Two experiments were conducted to determine how a period of exposure to 0 oC, between two periods of imbibition at 20 oC, affected radicle development and the uniformity of seedling emergence.

In both experiments cold treatments, given 12 h after seed imbibition began, produced shorter radicles than those given at 0, 4, 8, 16 and 20 h. Increasing the duration of exposure to 0 oC gave longer radicles and reduced the spread of seedling emergence. It is concluded that lettuce seeds are particularly sensitive to a temperature change about 12 h after seed imbibition starts.
The combined use of mineral oils and pyrethroids to control plant viruses transmitted non‐ and semi‐persistently by Myzus persicae
Authors: GIBSON R. W. , RICE A. D.
Published: February 2008

A mixture of the pyrethroid WL85871 (an enriched form of cypermethrin) and the mineral oil SC811 intoxicated adult apterae of an insecticide‐susceptible clone of the peach‐potato aphid Myzus persicae at a similar rate to a treatment containing only WL85871, but the mixture killed more. Mixtures of WL85871 andSC811 also gave better control of both acquisition and inoculation by M. persicae of the non‐persistent potato virus Y (PVY) than either component alone. A mixture of the pyrethroids deltamethrin, cypermethrin and PP321 with SC811, or a mixture of WL85871 with the mineral oil Bayol 52 also decreased acquisition of PVY, and a mixture of WL85871 with SC811 decreased acquisition of another non‐persistently transmitted virus, beet mosaic virus. Control with mixtures was generally better than that provided by each component applied separately. When testing acquisition or inoculation of the semi‐persistent beet yellows virus, fewest plants were infected in treatments incorporating both WL85871 and SC811.
The effect of previous host plant on the fecundity of Myzus persicae and its ability to transmit beet yellows virus
Authors: GLADDERS D. W. , PETERS D.
Published: February 2008

Myzus persicae transferred to rape produced offspring with higher survival, larger weight and faster development than aphids transferred to beet, irrespective of whether they had been reared on rape or beet. Aphids transferred from rape to beet produced fewer offspring than those reared continuously on rape. On beet, rape‐reared adults produced progeny with lower survival, slower development, smaller adult size and lower fecundity than the progeny of beet‐reared individuals, but there were no differences in these characteristics associated with host plant after one generation. Aphids from rape were less than half as efficient in transmitting beet yellows virus as aphids reared continuously on beet but after one subsequent generation on beet this difference had disappeared completely. These results are discussed in relation to field conditions.
Microorganisms associated with the retting of flax treated with the herbicide glyphosate
Authors: MERCER P. C. , FRASER T. W.
Published: February 2008

Greater numbers of fungi were isolated from stems of flax following treatment with the herbicide glyphosate than from untreated stems although there was also a general increase in numbers with time. The fungal genera isolated were the same from both treated and untreated plants, the most common being Cladosporium, Aureobasidium, Epicoccum and Botrytis with Cladosporium being predominant. Populations of bacteria were generally not enhanced after glyphosate treatment. Partial dew‐retting of crops resulted in the reduction in numbers of Cladosporium compared with conventionally‐treated flax.

The increase in numbers of fungi was associated with an increase in retting. Overretting also occurred, particularly in discrete pale areas on the stem. These were associated with colonisation by Botrytis cinerea and the tensile strength of fibres from these areas was 15 times weaker than from surrounding darker areas of the stem.

Light microscopy showed death of cells after glyphosate application, followed by invasion and degradation of the epidermis and cortex by fungi and other microorganisms. Fibre bundles were partially dissociated but the individual fibres remained largely intact as did the xylem and medulla.
Sudden death of cocoa in Papua New Guinea associated with Phytophthora palmivora cankers invaded by bark beetles
Authors: PRIOR C.
Published: February 2008

An extensive survey in 1976‐82 indicated that sudden death of cocoa was widespread in Papua New Guinea with losses up to 1% per month in trees over 10‐yr‐old, especially in neglected plantations. Over 95% trees affected had large Phytophthora palmivora canker lesions and over 90% of the cankers were invaded by bark beetles. In an intensive single year survey of one plot 18‐8% of 69 healthy trees died. Ambrosiella spp., P. palmivora and Fusarium solani were isolated from wood surrounding beetle tunnels but only the last two caused extensive lesions when inoculated into the xylem of healthy trees. The evidence obtained indicated that the sudden death syndrome is initiated by P. palmivora cankers on trunks and main branches but bark beetles are a major contributory factor and fungi associated with their tunnels may contribute to the problem. There is a risk of further outbreaks of the disease as cocoa cultivars susceptible to P. palmivora continue to be planted.
The susceptibility of barley cultivars to barley yellow mosaic virus (BaYMV) and its fungal vector, Polymyxa graminis
Authors: ADAMS M. J. , SWABY A. G. , MACFARLANE I.
Published: February 2008

In glasshouse experiments, barley seedlings were inoculated with barley yellow mosaic virus (BaYMV) either mechanically or by using zoospores or cystosori of a viruliferous isolate of the vector, Polymyxa graminis, maintained on barley in sand culture.

Experiments using mechanical inoculation showed that seedlings became more resistant with age. Consistent cultivar differences were obtained: cvs Maris Otter and Halcyon were very susceptible and cv. Athene seemed immune. Symptoms developed more rapidly at 23 than at 17 or 11 oC. After vector inoculation, symptoms developed more slowly than after mechanical inoculation but cultivar ranking was similar. Cultivars did not differ in susceptibility to the vector, as measured by zoospore production on their roots. Spring barley cultivars supported the growth of the vector which remained viruliferous and some showed symptoms although, in the field, symptoms do not appear on spring‐sown crops.
Yield in spring barley at contrasting sites in England and Scotland
Authors: ELLIS R. P. , BROWN J.
Published: February 2008

The yield and yield components of tall and short genotypes derived from the cross between two spring barley cultivars, Ark Royal and Golden Promise were examined. The genotypes were grown at two locations in England and two in Scotland. The highest yields were observed at two English sites (in East Anglia) rather than, as expected, in Scotland (East Lothian). Higher yield at the English sites was related to the greater means recorded for all the components of yield. The tall genotypes produced higher yields than the short genotypes, particularly at sites affected by drought. There were significant interactions between genotypes and environments for plot yield. Selection for increased yield would have been possible within either tall or short lines.
The effect of elevated temperatures and their duration on the incidence of hollow heart in pea seeds
Authors: HALLIGAN E. A.
Published: February 2008

Plants of Pisum sativum cv. Pania were exposed to high temperature (35 oC day/25 oC night) at three stages in development. These were: (i) at process crop maturity, when the seed moisture content (m.c.) was 80%, i.e. about 10 days prior to pod wrinkle, (ii) at a seed m.c. of 70 to 80%, about the onset of pod wrinkle, and (iii) when the seed m.c. was 50 to 60%, 10 days after the onset of pod wrinkle. At each stage of development the high temperature treatment was imposed for 2,4,6, 8 or 10 days. Plants exposed to high temperature at seed m.c. of 70 to 80% produced seed with the highest incidence of hollow heart and at all stages of development the incidence increased with the length of exposure to the high temperature. Where plants at the development stage of pod wrinkle (seed m.c. 70–80%) were exposed to a range of temperature regimes for 5 days, over 20% of the seeds had hollow heart when the mean day/night temperature was 25 oC. Above a mean temperature of 25 oC, the percentage of affected seed increased with increasing day or night temperature. Over 80% of the seeds had hollow heart symptoms after 5 days exposure to a daily mean temperature of 32‐5 oC. The severity of symptom development was not related to the proportion of seeds with the disorder and, under laboratory conditions, seed germination was not affected.
Chemical control of wheat bulb fly (Delia coarctata) attacking winter wheat in Eastern England, 1969–1981
Authors: MASKELL F. E. , GAIR R.
Published: February 2008

Dry powder, liquid and microencapsulated formulations of organophosphate and synthetic pyrethroid insecticidal seed treatments were tested as possible alternatives to the standard organochlorine seed treatments for autumn‐sown wheat in mineral and organic soils heavily infested with wheat bulb fly eggs and (subsequently) larvae. Retention of insecticides on the seed coat varied from 40% to 120% of the target dose; it was usually good when microencapsulated formulations were used.

Chlorfenvinphos, fonofos, isofenphos and triazophos, each applied at 2‐0 g a.i./kg seed, were phytotoxic, the symptoms varying from a slight delaying effect upon germination to an adverse effect upon grain yield. Chlorfenvinphos at 0–2 to 2‐0 g a.i./kg seed was consistently effective against wheat bulb fly larvae in both mineral and organic soils. Athidathion 0–8 g a.i./kg, carbophenothion 1–2 g a.i./kg, ethion 1–7 g a.i./kg and fonofos (microencapsulated formulations) at 1‐0 or 2‐0 g a.i./kg were also effective in mineral and organic soils. Of the synthetic pyrethroids tested as seed treatments, permethrin gave excellent results in mineral soils at 1‐0 g a.i./kg or in synergised formulations at 0–12 or 0–24 g a.i./kg but was disappointing in organic soils.

In a single comparison of seed treatments applied to wheat sown early (14 October) and late (20 November), chlorfenvinphos was effective at both sowing dates whereas athidathion, ethion and pirimiphos‐ethyl gave better results in late‐sown wheat.

A single trial compared deep with shallow sowing of treated seed. Most insecticides performed better on shallow‐sown wheat, but chlorfenvinphos was equally effective against the pest at both sowing depths.

Most insecticides restricted the numbers of larvae entering host plants but had little or no subsequent effect upon larval survival within attacked shoots. Fonofos and isofenphos, and to a lesser extent chlorfenvinphos, seed treatments additionally killed many larvae within plant shoots.
Response of subterranean clover cultivars to root rot fungi
Authors: BARBETTI M. J. , WONG D. H. , SIVASITHAMPARAM K. , D'ANTUONO M. F.
Published: February 2008

Twelve widely grown cultivars of subterranean clover (Trifolium subterraneum) were screened both under controlled environment conditions for their resistance to five fungi commonly associated with root rot and under field conditions for their resistance to natural root infections. All cultivars showed decreased seedling survival (particularly from Pythium irregulare and Rhizoctonia solani), tap and lateral root rot (particularly from Fusarium avenaceum, P. irregulare, and R. solani) and reduced plant size (particularly from R. solani and P. irregulare). Individual cultivars generally differed in their response to the five pathogens and for any one pathogen there was generally a range of cultivar susceptibilities. Cultivars with the best resistance to individual root pathogens were identified. The results for the five individual pathogens under controlled conditions only showed correlation with field data for some of the parameters compared.
Control of pre‐ and post‐emergence damping‐off of potato seedlings caused by Rhizoctonia solani in Peru
Authors: ELANGO FRITZ
Published: February 2008

Fungicide treatment of soil and true potato seed and the use of subsoil as a growth medium significantly reduced pre‐emergence damping‐off caused by Rhizoctonia solani. Attempts were made to determine safe levels of fungicides for soil and seed treatments. For seed, safe levels varied between 0–9% a.i. for pentachloronitrobenzene (PCNB) and 3‐0% a.i. for mancozeb (dithane M‐45).

Fungicides only marginally reduced post‐emergence damping‐off of transplants raised from true potato seed but gave significant increase in yield. The prospects of using fungicide treatment of true seed to control damping‐off in seed beds and in direct field sowing are discussed.
An association of carbohydrates with particles of arabis mosaic virus retained within Xiphinema diversicaudatum
Authors: ROBERTSON W. M. , HENRY CAROL E.
Published: February 2008

Sections through the odontophore of Xiphinema diversicaudatum showed two types of staining for carbohydrates using the periodic acid ‐ thiosemicarbazide ‐silver proteinate (PA‐TSC‐SP) reaction. The first consisted of thin, localised, intensely‐stained patches on the lining of the food canal of all the specimens examined. The second type, found only in nematodes exposed to AMV‐infected plants, revealed cloud‐like areas of carbohydrate ‐ containing material associated with the stained patches on the lining of the food canal. By staining alternate sections with uranyl acetate/lead citrate, these carbohydrate clouds were shown to contain virus particles. Although the cloud material could have originated from either the plant or the nematode, sections through a pellet of partially purified virus particles prepared from plants did not stain for carbohydrate. The possible role of carbohydrate in virus retention and transmission is discussed.
Production of monoclonal antibodies for the detection of potato virus Y
Authors: ROSE D. G. , HUBBARD A. L.
Published: February 2008

Monoclonal antibodies (McAb) were obtained to potato virus Y (PVY) after immunisation of BALB/c mice with purified PVY, tobacco necrotic strain (PVYn). Spleen cells from a mouse showing a high serum titre were used for fusion with X63NS1 myeloma cells. Hybridomas were selected in medium containing HAT. Culture supernatants were screened for antibody production against PVY, ordinary strain (PVY0) and PVYn using indirect ELISA.

Clones of interest were further cross‐reacted with 12 isolates each of PVY0 and PVYn and two isolates of potato virus A (PVA) and healthy sap.

For further trials, two clones which reacted specifically with PVYn isolates and one which detected all PVY isolates except two of potato virus C (PVC) were selected.
The role of awns in the resistance of cereals to the grain aphid, Sitobion avenae
Authors: ACREMAN T. M. , DIXON A. F. G.
Published: February 2008

Six genotypes of awned spring wheat were more resistant to Sitobion avenae than de‐awned wheat. Aphids that fed on awns were up to 22% less fecund and were more likely to be dislodged than aphids that fed elsewhere on an ear. These two factors reduced aphid population growth on awned earing plants in the field to a third of that observed on awnless plants. As awns may also benefit yield and are easy to select for it is recommended that awned winter wheats could be bred and used to reduce the incidence of outbreaks of S. avenae.
The effects of storage atmosphere and temperature on the keeping quality of Spartan apples
Authors: STOW J.
Published: February 2008

The rate of softening of apples of the variety Spartan was reduced by addition of 6 or 8% CO2 to a storage atmosphere of 2% O2 at 1 ‐5 oC. This effect was observed in three seasons and in samples from five sources. Sensory assessments suggested that addition of carbon dioxide to the storage atmosphere had no adverse effect on eating quality.

Storage in 2% O2 at – 1 oC was as effective in maintaining flesh firmness as 8% CO2+ 2%O2 at 1–5 oC.

Strategies for further reductions in firmness loss during storage of Spartan apples are discussed.
Bulbil production in Narcissus: the effect of temperature and duration of storage on bulb unit development and subsequent propagation by twin‐scaling
Authors: HANKS GORDON R. , SHAIK G. , JONES S. K.
Published: February 2008

The growth of bulb components and carbohydrate content of Narcissus bulbs was followed during storage at 5–30 oC, and the productivity of twin‐scale propagules cut from bulbs after these storage treatments was studied. Growth of daughter bulb unit components was greatest during storage at 9–15 oC, and greatly inhibited at 30 oC. Concentrations of soluble sugars were highest following 30 oC storage, and higher in intermediate bulb scales than in outer or inner scales. Bulbil production on twin‐scales was greatest on propagules cut from the intermediate scales, and in bulbs previously stored at 15 or 30 oC.
Failure of British isolates of beet western yellows virus to infect potato
Authors: BARKER H.
Published: February 2008

Potato cultivars were tested for susceptibility to two British isolates of beet western yellows virus originally obtained from sugar beet and oil seed rape. Neither isolate was transmitted by Myzus persicae to virus‐free potato plants, either by itself or in association with potato leafroll virus.
Spectral reflectance of healthy and diseased watermelon leaves
Authors: BLAZQUEZ CARLOS H. , EDWARDS GEORGE J.
Published: February 2008

Significant differences in reflectances were found between healthy and diseased watermelon leaves in the 500–640 nm visible region and 740–900 nm near infrared regions of the electromagnetic spectrum. Spectrophotometric reflectance measurements were made to determine differences between healthy and diseased watermelon (Citrullus vulgaris) leaves over the 500–2700 nm wave length interval. Plants with Fusarium wilt, downy mildew (Pseudoperonospora), and watermelon mosaic were observed during the growing season. Early symptoms of the diseases had significantly greater reflectance values than the advanced stages of the diseases. A ratio of two wavelength bands, 500–640 nm and 660–900 nm gave an accurate index for determining stages of disease, both early and advanced. There were greater differences in reflectance between all three diseases and healthy leaves in both early and advanced stages in the 900–1400 nm, 1500–1900 nm, and 2000–2400 nm middle infra‐red wavelengths of the electromagnetic spectrum than in the visible 450–740 nm range. All three diseases had significant differences in the 700–900 nm near‐infra‐red range.
The association of Pythium spp. with cavity spot and root dieback of carrots
Authors: WHITE J. G.
Published: February 2008

The possibility of an association between cavity spot and root dieback of carrots has been demonstrated, along with control of both disorders by soil sterilisation with methyl bromide or seed and soil treatment with metalaxyl. When carrots were grown in sterilised soil into which five Pythium spp. were introduced individually, cavity spot occurred and the Pythium spp. were re‐isolated from cavities. The relatively slow growing Pythium violae gave the highest percentage of carrots with cavities.

In a laboratory test a range of Pythium spp. produced cavities on carrots previously grown in sterilised soil, and with one exception were re‐isolated from those cavities.
The manipulation of white clover ‘host preference’ for strains of Rhizobium trifolii in an upland soil
Authors: RENWICK ANNABEL , JONES D. GARETH
Published: February 2008

The nodule occupancy of white clover cv. Milkanova three months after inoculation in an upland soil with a 1:1 mixture of an effective (CP3B) and an ineffective strain (R4) of R. trifolii, differed significantly depending on the lime level. The percentage of nodules occupied by the effective strain decreased from 64% to 29% with increasing lime level whilst the ineffective strain nodules increased from 4% to 24% with mixed nodule infections also increasing from 9% to 22% There was no such difference after 14 months with this cultivar nor with cv. S184 at either harvest. Inoculation with a higher ratio of the less preferred strain (R4) resulted in this strain dominating the nodules and significantly reducing the dry weight of the plants (first harvest) and clover cover of plots (second harvest). Where antibiotic resistant mutants of these strains were used, with one exception, there were no significant differences between the wild‐type strains and their mutant derivatives for any of the parameters measured. In a comparison of the two marker techniques used, fluorescent ELISA was less sensitive than the antibiotic resistance technique for the identification of the occupants of small ineffective nodules. The use of both techniques in large field experiments is discussed. Clover establishment was affected by lime level during the establishment phase but the beneficial effect of lime had disappeared by the second harvest year.