bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of beet cyst nematode, Heterodera schachtii, on the yield of sugar beet in organic soils
Authors: COOKE D. A.
Published: February 2008

In ten experiments on commercial sugar‐beet crops grown on organic soils in 1984–86, a Genstat programme was used to examine the relationship between the initial population of Heterodera schachtii and sugar‐beet root yield using the equation

Y = Ymin + (Ymax ‐ Ymin) Zpi‐T

Fixing T = 200 eggs + juveniles 100 g‐1 soil and ZT= 0.95, estimated values of Ymax varied from 49.2–67.1 t ha‐1 (129– 155% of the national average root yield for the years in which the experiments were carried out) and estimates of Ymin varied from 14.5–53.9 t ha‐1 (27–94% of Ymax). The estimated average root yield loss caused by the nematode was 6.95 t ha‐1.
Improved germination in seeds of guayule (Parthenium argentatum Gray) following polyethylene glycol and gibberellic acid pretreatments
Authors: HURLY R. F. , STADEN J. VAN , SMITH M. T.
Published: February 2008

Suitable conditions for the pretreatment of seeds of guayule were determined with a view to improving germination. These included the addition of thiram (500 mg litre‐1), and applications of GA4+7 alone, or in combination with polyethylene glycol. Significant improvements in the seed germination were seen following applications of PEG at ‐0.10 MPa. Simultaneous application of GA4+7 with priming improved soil emergence and germination over a wide range of temperatures. No beneficial effects of PEG priming were evident on seed storage.
Glucosinolate responses of oilseed rape, mustard and kale to mechanical wounding and infestation by cabbage stem flea beetle (Psylliodes chrysocephala)
Authors: KORITSAS V. M. , LEWIS J. A. , FENWICK G. R.
Published: February 2008

Mechanical wounding of the petioles of six laboratory‐grown rapeseed (Brassica napus) cultivars induced physiological changes in the plant, markedly affecting the levels of individual glucosinolates. Greatest increases were observed for the indole glucosinolates, glucobrassicin and neoglucobrassicin. Such changes were usually associated with large decreases in the levels of aliphatic glucosinolates. The total glucosinolate content of the wounded plant was thus a reflection of these two opposing trends and wounding produced a greater relative indole glucosinolate content in this total figure. Thus increasing wounding was associated with an increase in indole glucosinolates and a decrease in aliphatic compounds.

Infestation of field‐ and laboratory‐grown rapeseed with cabbage stem flea beetle (Psylliodes chrysocephala) produced similar effects, which were observed in various parts of the plant. Differences in response between field‐ and laboratory‐grown infested plants are attributed to the different physiological ages of the harvested material.

Laboratory‐grown kale and mustards also showed wound‐induced glucosinolate changes. The kale, cv. Fribor, produced elevated levels of both indoles and aliphatics after wounding. Total glucosinolate content in the mustards, which, unlike rape and kale, normally contain only traces of indole glucosinolates in the unstressed state, was increased following wounding. This was, however, not associated with elevated levels of indole glucosinolates, but with accumulation of aliphatic (Brassica nigra, B. juncea) and aromatic (Sinapis alba) glucosinolates. The significance of these findings is discussed.
Hydroxamic acid levels in Chilean and British wheat seedlings
Authors: COPAJA S. V. , NIEMEYER H. M. , WRATTEN S. D.
Published: February 2008

Fifty‐two cultivars of Chilean wheats were screened, using high pressure liquid chromatography, for hydroxamic acid levels at the seedling stage when maximal levels occur. DIMBOA levels ranged from 1.4 to 10.9 mmol/kg fr. wt and DIBOA levels ranged from 0 to 1.1 mmol/kg fr. wt. The family of wheat cultivars leading through breeding to the British cultivar Maris Freeman was examined. While DIMBOA and DIBOA levels in the ancestors ranged from 1.6 to 3.8 mmol/kg fr. wt and 0.16 to 0.34 mmol/kg fr. wt, respectively, DIMBOA and DIBOA levels in Maris Freeman were 2.39 and 0.24 mmol/kg fr. wt, respectively. The results are discussed in terms of the possibility of breeding for aphid resistance by making use of hydroxamic acids.
Control of the Indian mole rat with alpha‐chlorohydrin: laboratory studies on bait acceptance and antifertility effects
Authors: SAINI MANJIT S. , PARSHAD V. R.
Published: February 2008

Toxic and antifertility effects of feeding poison baits of a toxicant‐sterilant, alpha‐chlorohydrin, were studied against the Indian mole rat Bandicota bengalensis. It was found that 0.5% alpha‐chlorohydrin bait was the most palatable formulation which delivered the amount of active ingredient equal to or more than MLD (82 mg/kg) to B. bengalensis in a single day's feeding. The rats suffered maximum mortality with this bait concentration both in no‐choice and bi‐choice feeding trials. Male survivors of 0.5% and 1.0% alpha‐chlorohydrin baits showed functional abnormalities of their testes as revealed by loss in testicular weight, decrease in the diameter of seminiferous tubules and thickness of seminiferous epithelium and abnormally low levels of spermatogenic cells. Effect of the poison on epididymis became apparent by the presence of epididymal lesions in caput epididymides and low levels of sperm concentration, live sperms and sperm motility in the cauda epididymal fluid. Our findings on the acceptance and toxiccum‐antifertility effects of feeding alpha‐chlorohydrin baits suggest field evaluation of this poison for the management of B. bengalensis would be appropriate.
Effects of the neem product, RD‐Repelin, on settling behaviour and transmission of zucchini yellow mosaic virus by the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae)
Authors: HUNTER WAYNE B. , ULLMAN DIANE E.
Published: February 2008

The botanical product RD‐Repelin® was highly repellent to pea aphids at concentrations of 1%, 4% or 10%. Repellency occurred prior to leaf contact by aphids at all three concentrations. RD‐Repelin® delayed symptom expression of zucchini yellow mosaic virus (ZYMV) in 81% of plants treated with 1% concentration, although virus transmission was not prevented. The effects of RD‐Repelin® on aphid settling behaviour, symptom expression and potential for pest management are discussed.
The effects of deep cultivation and oxamyl on control of potato cyst‐nematode, Globodera rostochiensis
Authors: WHITEHEAD A. G. , NICHOLS A. J. F.
Published: February 2008

Soil compaction associated with frequent cultivation of potatoes was partly removed with a deep winged‐tine coulter. This increased the yield of tubers of cv. Cara in 1987 and 1988 and of cv. Désirée in 1987 in soil which was heavily infested with potato cyst‐nematode, Globodera rostochiensis (Woll.), and which was treated with oxamyl at 5.6 kg ha‐1. In 1988, in soil not treated with oxamyl, deep cultivation significantly decreased the yield of cv. Cara. In both years, oxamyl decreased numbers of G. rostochiensis eggs in the soil following cv. Désirée potatoes but not following cv. Cara which were resistant to the nematode.
Sources of resistance to stem nematode, Ditylenchus dipsaci (Kühn) Filipjev, in species of Medicago and Trifolium
Authors: WHITEHEAD A. G.
Published: February 2008

The putatively resistant lucerne cv. Euver was as susceptible to 11 English and 11 French populations of ‘lucerne race’ stem nematode, Ditylenchus dipsaci, as the susceptible cv. Europe. The ‘resistant’ cv. Vertus showed some resistance to five of the English and four of the French populations but was just as susceptible as Europe to three English and four French populations. Twelve annual species of Medicago were very resistant to a mixture of two English and two French populations of the nematode. None of 13 perennial spp. of Medicago was very resistant to the same mixture of nematodes but resistant plants were identified in M. borealis, M. dzhawakhetica, M. glutinosa and M. romanica. Twenty six spp. of Trifolium were resistant to a mixture of two English and two French populations of ‘red clover race’ stem nematode.
Surveys of beet cyst nematode (Heterodera schachtii Schmidt) in England
Authors: COTTEN J. , COOKE D. A. , DARLINGTON P. , HANCOCK M.
Published: February 2008

In 1977, all restrictions on cropping imposed by successive Beet Eelworm Orders, in force since 1943, were removed. To monitor the effect of this relaxation, surveys for beet cyst nematode (Heterodera schachtii), were undertaken annually between 1977 and 1988 in seven sugar‐beet‐growing areas thought to be most at risk from the nematode. In Area 1 (approximately the “Scheduled Area” of the Beet Eelworm Orders, comprising mainly the East Anglian fens), detectable infestations increased from 8.3% of fields sampled in 1977 to 34.0% in 1985, and thereafter stabilised at about 30% of fields sampled. Detectable infestations increased in only one other Area (West Norfolk and West Suffolk, adjacent to Area 1). The incidence of detectable infestations was directly related to the length of the break between host crops. Soil‐applied pesticides, principally targetted at arthropod pests, had no apparent effect on the incidence of detectable infestations of H. schachtii.
Seedbank persistence and seedling emergence of seven weed species in autumn‐sown crops following a single year's seeding
Authors: WILSON B. J. , LAWSON H. M.
Published: February 2008

Seedbanks and seedling emergence, resulting from seeds shed in wheat crops and ploughed in, were monitored in two experiments for 3–4 years in successive autumn sown crops, in which herbicides were used to prevent re‐seeding. Populations of Galium aparine, Papaver rhoeas, Lamium purpureum, Myosotis arvensis, Veronica persica, Viola arvensis and Veronica hederifolia were studied in separate plots. The numbers of viable seeds in the soil declined exponentially; G. aparine and V. hederifolia declined most, and P. rhoeas and V. arvensis least rapidly. Total weeds (all species) over the 3–4 years, (obtained by adding successive numbers of seedlings recorded in each autumn or winter), represented 3–4% of the first year seedbank for the combined species. Few seedlings emerged in the first year after seeding due to effective burial by the initial ploughing. The species showing the greatest emergence in the first year, relative to seedbank size, were G. aparine and V. hederifolia. Other, smaller seeded, species produced their main seedling flushes in the second and third years after seeding. It is concluded that poor weed control in one year is likely to result in large weed infestations for up to four years and probably longer for some species.
The complementary effects of plant resistance and reduced pesticide dosage in field experiments to control the turnip root fly, Delia floralis, in swedes
Authors: TAKSDAL GUDMUND
Published: February 2008

The integration of different doses of chlorfenvinphos with plant resistance to different levels of Delia floralis attack in swedes was investigated at Saerheim Research Station in field experiments during 1987, 1988 and 1989. The indices of damage and grade 1 yields indicated different levels of resistance ranging from the partially resistant cvs Melfort, Angus and Vige down to the susceptible cvs Gry and Ruta. The relative resistance of the cvs changed with increasing levels of damage. Cvs Melfort and Angus were consistently the most resistant, while the resistance of Vige seemed to break down at high levels of attack. At these levels and in the absence of chemical treatment Gry was as resistant as Melfort and Angus. At the lowest level of attack, the resistance alone gave satisfactory control with Melfort, Angus and Vige. A half dose of chlorfenvinphos was sufficient to protect Melfort and Angus at higher levels of attack. Damage levels recorded in October showed that the different cultivars expressed widely different levels of resistance to D. radicum than to D. floralis.
Race non‐specific resistance to Bremia lactucae
Authors: GUSTAFSSON INGRID
Published: February 2008

Three ways of measuring race non‐specific resistance to Bremia lactucae in lettuce were studied to determine the most important components of this form of resistance. Tests were conducted on leaf discs from 4–6 wk‐old plants that were quantitatively inoculated and incubated under controlled conditions. Observations were made of disease intensity, latent period and production of conidia. Inoculum concentration markedly influenced disease intensity and latent period. Cv. Iceberg exhibited race non‐specific resistance and this was characterised by a longer latent period, a lower disease intensity and reduced production of conidia compared to the susceptible control cv. Cobham Green. On older, intact plants, the differences in latent period and disease intensity between cultivars were even greater. Production of conidia was a particularly good criterion for discriminating levels of resistance.
Habitat factors influencing the distribution of polyphagous predatory insects between field boundaries
Authors: THOMAS M. B. , SOTHERTON N. W. , COOMBES D. S. , WRATTEN S. D.
Published: February 2008

The winter distributions of a range of polyphagous predators were investigated in relation to field boundary structure. The distribution of Demetrias atricapillus was significantly positively correlated with the density of cocksfoot (Dactylis glomerata) tussocks, and Forficula auricularia and Tachyporus chrysomelinus were significantly positively correlated with percentage cover of deciduous leaf litter, However, although densities of predators varied significantly between field boundaries, no further relationships were identified to explain the observed predator distribution patterns. It is suggested that detailed intensive investigations rather than the extensive approaches of the present study, are required to address questions relating to successful over wintering and selection of over wintering site.
The effect of plant phenology on the induction of alatae and the development of populations of Metopolophium dirhodum (Walker), the rose‐grain aphid, on winter wheat
Authors: HOWARD M. T. , DIXON A. F. G.
Published: February 2008

In field experiments apterous Metopolophium dirhodum produced significantly more alatae when reared on mature plants (milky ripe stage) than on young plants. Nymphal and adult survival and relative growth rate were little affected by the developmental stage of the host plant. Relative growth rate and fecundity were strongly related to temperature.

Laboratory experiments confirmed that the developmental stage of wheat had no significant effect on survival or relative growth rate of the aphids. However, laboratory grown plants did not produce the levels of alate production seen in field crops and in the field experiments. It is suggested that in investigations into the effects of the host plant on cereal aphids field grown plants should be used whenever possible.

Alate production is proposed as the major plant induced factor affecting the development of M. dirhodum populations on wheat in the field. Alatae developed on mature plants even when the number of aphids was very low.
Mango stem end rot pathogens ‐ Fruit infection by endophytic colonisation of the inflorescence and pedicel
Authors: JOHNSON G. I. , MEAD A. J. , COOKE A. W. , DEAN J. R.
Published: February 2008

The stem end rot pathogens of mango (Mangifera indica), (Dothiorella dominicana, Dothiorella mangiferae, Lasiodiplodia theobromae (Syn. Diplodia natalensis Phomopsis mangiferae, Cytosphaera mangiferae, Pestalotiopsis sp. and Dothiorella‘long’), as well as other fungi (including Alternaria alternata), were found to occur endophytically in the stem tissue of mango trees prior to inflorescence emergence. On samples from trees with a record of low stem end rot levels, colonisation did not extend into the most recently produced flush of stem tissue. At a site with a history of high stem end rot levels, sequential monitoring of inflorescence tissue between flowering and harvest by plating out small (c. 8 mm3) tissue pieces revealed, that at least some of the pathogens ‐ Dothiorella spp., P. mangiferae, Pestalotiopsis sp. and C. mangiferae gradually colonised the inflorescence, reaching the pedicel tissue of young fruit ‐ 8 wk after flowering. Subsequently, detection frequency of the pathogens in inflorescence tissue declined, possibly because of interference from copper residues (from field sprays) accumulating on tissue samples. The detection frequency of A. alternata also increased as Dothiorella spp. declined, however these changes could not be attributed to antagonistic interactions between the two fungi.

Using larger tissue pieces (1–2 mm thick transverse sections, or a square of tissue 25 mm2× 3 mm thick) in isolations, endophytic colonisation by Dothiorella spp. and P. mangiferae was detected in stem, inflorescence and pedicel tissues of mature‐fruit‐specimens from two different sites, one unsprayed, and the other regularly sprayed with copper. The fungi were detected more frequently in the samples from unsprayed trees. Fruit from the sprayed orchard subsequently developed a high level of stem end rot caused by D. dominicana, while a lower level of stem end rot developed in unsprayed fruit, possibly because the latter fruit were also extensively diseased by anthracnose (Colletotrichum gloeosporioides Penz.). Endophytic colonisation of inflorescence and pedicel tissue was found to be a primary route of infection for fruit which develop stem end rot during ripening.
The effect of the systemic fungicide benomyl on survival and reproduction of the bird cherry aphid (Rhopalosiphum padi)
Authors: AKHTAR S. , EMDEN H. F. VAN.
Published: February 2008

Weight gain and intrinsic rate of population increase (rm) of Rhopalosiphum padi were measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity and rm became statistically significant by 25 ppm.

Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm.

A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.
Plant resistance to fungal diseases induced by the infection of cucumber mosaic virus attenuated by satellite RNA
Authors: QIN BINGYI , ZHANG XIUHUA , WU GUSUI , TIEN PO
Published: February 2008

Biological control agents (BCAs) composed of attenuated cucumber mosaic (CMV) and its satellite RNA for controlling CMV diseases were found to induce plant resistance to a number of fungal diseases. Tests conducted in both the field and greenhouse showed evident protective effects against fungal infections by the BCAs. Artificial inoculation with a fungal spore suspension using BCA‐treated plants, satellite transgenic plants and plants infected with CMV alone indicated that the resistance to fungi was induced by the virus infection, not by the presence of satellite RNA.
The use of tracers to estimate the exposure of beneficial insects to direct pesticide spraying in cereals
Authors: ÇILGI TAMER , JEPSON PAUL C.
Published: February 2008

A fluorescent spray tracer was used to measure the profile of spray deposits through winter‐wheat crop canopies and upon beneficial insects, placed in fixed positions which approximated to their natural distributions. Tracer deposition profiles were recorded on a series of occasions between G.S. 47 to G.S. 90. Deposition levels declined through the canopy on each occasion but the proportion of the spray reaching the ground varied between growth stages. Deposition rates upon insects followed the same trends but insects on the aerial parts of the plant received a higher volume of tracer per unit area than the part of the crop that they were placed upon. Insects placed on the ground received a dose equivalent to their ground area. For a given distribution of insects, these data permit direct spray exposure to be estimated. The general application of the method to a wide range of crops, to the calculation of risk indices, to the standardisation of field tests and to the development of selective spray placement methods are discussed.
Genome affinities and epitope profiles of whitefly‐transmitted geminiviruses from the Americas
Authors: SWANSON M. M. , BROWN J. K. , POULOS B. T. , HARRISON B. D.
Published: February 2008

The relationships among fifteen isolates of whitefly‐transmitted geminiviruses (WTGs) from North, Central and South America and six from other continents were assessed (a) in nucleic acid hybridisation tests with sulphonated DNA probes for eight of the viruses, and/or (b) in triple‐antibody‐sandwich ELISA with panels of monoclonal antibodies (MAbs) to particles of African cassava mosaic virus (ACMV) and Indian cassava mosaic virus (ICMV). Probes specific for DNA‐A of four American viruses, abutilon mosaic (AbMV), bean golden mosaic (BGMV), squash leaf curl (SLCV) and tomato golden mosaic (TGMV), detected virtually all the American viruses but reacted weakly if at all with ICMV, ACMV or tomato yellow leaf curl virus from Thailand (TYLCV‐T). Conversely, the probe for ACMV DNA‐A did not detect any of the American viruses, and that for TYLCV‐T DNA‐A reacted weakly with SLCV and TGMV0020but did not detect the others. In contrast, probes specific for DNA‐B of the four American viruses or ACMV detected only the homologous virus, except for slight reactions between the AbMV DNA‐B probe and both chino del tomate virus (CdTV)‐DNA and SLCV‐DNA. However, a probe for DNA‐B of bean calico mosaic virus (BCMoV) reacted weakly with BGMV‐PR DNA, and a probe for DNA‐B of CdTV from Mexico detected several American viruses.

Six out of 17 MAbs specific for ACMV and six out of 10 MAbs specific for ICMV reacted with one or other of the 14 American virus isolates tested. Two and‐ACMV MAbs reacted with all, and one anti‐ACMV MAb and two anti‐ICMV MAbs reacted with nearly all the American viruses, one anti‐ACMV MAb reacted with about half the American viruses and six other MAbs reacted with only one or two of them. Of the American viruses, CdTV and AbMV were the least closely related to the others. The epitope profiles of BCMoV, BGMV, cotton leaf crumple virus, serrano golden mosaic virus and SLCV were virtually indistinguishable. TGMV, potato yellow mosaic virus (PYMV) and an euphorbia virus had profiles intermediate between those of the BGMV cluster and AbMV‐CdTV. In general, the epitope profiles and the results of hybridisation tests with DNA‐A probes show that the similarities among the American viruses are greater than those between the American viruses and the viruses from other continents; the hybridisation tests with DNA‐B probes show that substantial differences exist between individual American viruses. In America, geminivirus evolution seems to have proceeded convergently from different progenitor viruses, or divergently from one ancestral form, with DNA‐B diverging to a greater extent than DNA‐A and its particle‐protein gene.
Development of pepper (Capsicum annuum) seed quality
Authors: DEMIR I. , ELLIS R. H.
Published: February 2008

Changes in seed quality in pepper (Capsicum annuum L.) were monitored during seed development and maturation in two seasons. Seed quality was assessed by a number of different tests, but principally by determining seed storage longevity in laboratory tests and seedling growth in glasshouse tests. Mass maturity (defined as the end of the seed‐filling phase) occurred 49–53 days after anthesis (DAA) in 1989 (varying among fruit layers) and 53 DAA in 1990 when seed moisture contents were 51–53%. The onset of both germinability and desiccation tolerance occurred either just before or at mass maturity. Maximum potential longevity (assessed by the value of the seed lot constant Ki) was achieved 63–65 DAA, i.e. not until 10–12 days after mass maturity (DAMM), in both years. Seedling dry weights in the glasshouse growth tests were maximal later still ‐ for seeds harvested 17–21 DAMM in 1989 and 17 DAMM in 1990; the effects on seedling weight arose from differences in times from sowing to emergence (P < 0.005) among different seed harvests, with no significant differences in subsequent relative growth rates (P > 0.25). Seed priming reduced mean germination times for seeds harvested at all stages of development, but had little effect on germination capacity and potential longevity, and did not affect the pattern of changes in potential longevity during seed development and maturation. The results contradict the hypothesis that seed quality is maximal at the end of the seed‐filling phase and that viability and vigour begin to decline immediately thereafter.
Non‐target effects of repeated methiocarb slug pellet application on carabid beetle (Coleoptera: Carabidae) activity in winter‐sown cereals
Authors: PURVIS GORDON , BANNON JAMES W.
Published: February 2008

The effects of repeated annual application of methiocarb‐based slug pellets, broadcast on the soil surface and drilled into the seed bed, on carabid beetle activity were investigated over a four year period on a winter‐sown cereal field using pitfall traps in barriered plots. Following applications in late autumn all winter‐active carabid populations were severely depressed; total carabid activity falling to less than 5% and 10–15% following broadcast and drilled applications, respectively, compared with untreated plots. Spring and summer‐active species, not active at the time of application, were largely unaffected by applications and were responsible for a gradual recovery of total activity from early spring onwards. Activity of all affected winter species remained demonstrably depressed on treated areas for the remainder of their seasonal incidence. However, all except one species, Bembidion obtusum, recovered to normal activity levels in the following season prior to reapplication. Recovery patterns are discussed in terms of the known biology of the species involved. Evidence that a minority of summer‐active species were also affected by treatments, sometimes positively and sometimes negatively, were attributed to indirect effects possibly involving prey availability and foraging behaviour. The long‐term ecological and short‐term agronomic implications of methiocarb effects on carabid populations in winter‐sown cereals are discussed.
The role of annual grasses in the phenology of Rhopalosiphum padi in the low rainfall belt of South Australia
Authors: BARRO PAUL J. DE. , WALLWORK HUGH
Published: February 2008

Rhopalosiphum padi (L.) (Hemiptera: Aphididae) was the first species of cereal aphids to colonise annual grasses across the state each year. Numbers were higher in the Lower Murray Valley than in the Mount Lofty Ranges or Adelaide Plains. At all locations, numbers generally increased until grasses reached the boot stage after which they declined. Alatoid production commenced in late July in response to crowding, but thereafter plant age and photoperiod were more important determinants. Metopolophium dirhodum (Walker) (Hem‐pitera: Aphididae) and Sitobion nr fragariae (Hemiptera: Aphididae) first appeared in annual grasses in late July.
The influence of weather and microclimate on Dalbulus maidis (Homoptera: Cicadellidae) flight activity and the incidence of diseases within maize and bean monocultures and bicultures in tropical America
Authors: CASTRO VILMA , RIVERA CARMEN , ISARD SCOTT A. , GÁMEZ RODRIGO , FLETCHER JACQUELINE , IRWIN MICHAEL E.
Published: February 2008

Mixed cropping systems in tropical America have been shown to be less prone than monocultures to damage from pathogens carried by insects. This finding formed the basis for a series of experiments conducted in Costa Rica to evaluate the hypothesis that mixed cropping systems create a physical environment that influences vector movement and consequently the spread of leafhopper‐borne pathogens.

The principle finding of the study is that both the mixture of plants and planting density have little influence on the spread of pathogens by Dalbulus maidis, an oligophagus leafhopper which prefers maize, within maize and bean single and mixed cropping systems. Leafhopper flight activity proved similar for high and low density monocultures and bicultures. The number of leafhoppers immigrating to and emigrating from a field appears dependent on the size of the field, not the density of maize plants. Single and mixed crops with the same density of maize plants were equally prone to damage by pathogens carried by leafhoppers. The lower percentage infection in high density than in low density maize treatments resulted from fewer vectors per plant in the former.
Validation of the European corn borer damage model on maize using X rays
Authors: LABATTE J. M. , GOT B. , CHARTIER M. , RUGET F.
Published: February 2008

In order to explain and predict yield losses caused by European corn borer larvae, Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), a mechanistic model was proposed to describe cavity appearance, their lengthwise extension, and their within‐plant distribution. It integrates main dynamical processes of larvae: mortality, development and within‐plant distribution. After its estimation and test under field conditions in 1988 and 1989, its validation, based upon X‐ray photographs, is presented. This method allows cavity appearance and lengthwise extension to be followed without damaging the plants. This study confirms the relevance of the damage model and the rate of cavity lengthwise extension estimated with it.
Effect of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates of Phoma bakeriana
Authors: NEBANE C. L. N. , EKPO E. J. A.
Published: February 2008

The effects of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates (PB1, PB2, PB3) of Phoma bakeriana were investigated in vitro. There was no isolate effect on growth and pycnidium production but some evidence of a medium effect. Exceptionally high growth rate on two media corresponded with high pycnidium production; while low growth rates on other media were generally associated with high sporulation.

There was a large temperature effect and an isolate effect on growth with a significant temperature by isolate interaction. Temperatures of 5°C, 10°C and 35°C inhibited pycnidium formation completely while the range 15–30°C had no effect on sporulation. Maximum growth and pycnidium production occurred at 25°C.

Near‐ultraviolet radiation seemed to have caused higher pycnidium counts than the other light sources.
Interpretive value of symptoms of infection by Gaeumannomyces graminis in wheat seedlings grown in sand culture
Authors: PENROSE L. D. J.
Published: February 2008

Symptoms of infection by the fungal pathogen Gaeumannomyces graminis were studied in roots of wheat seedlings grown in sand culture in order to assess resistance. Three sets of wheat were studied, 10 cultivars previously thought to differ in infection, and 44 and 54 segregating families from two crosses between four of these wheats, Aus1080 × Condor and Termu89–72 × Bayonet respectively. The isolates of G. graminis employed had previously been selected for differences in virulence.

The interpretive value of symptoms of infection were considered, by comparison with direct measurement of the spread of hyphae from a fixed point of inoculation, and by repeatability of measurements over experiments. Two symptoms of infection, cortical browning and stelar blackening, are thought to be host mechanisms to resist hyphal invasion and were suppressed by rapid colonisation of root tissues. A third symptom, general discolouring of tissue, appeared to be a necrotic symptom of aggressive colonisation.

Since only root segments distal to the point of infection were studied, stelar blackening appeared the least flexible measure of severity of infection. Cortical browning appeared to be influenced by nutritive status of seedlings, and was negatively associated with the incidence of necrotic discolorations. Wheats differed consistently and mostly in cortical browning, and while also differing in extent of necrotic discoloration, difficulty in quantifying the latter character limited its value in assessing resistance to G. graminis in this study.
Interference between viroids inducing exocortis and cachexia diseases of citrus
Authors: SEMANCIK J. S. , GUMPF D. J. , BASH J. A.
Published: February 2008

Systemic interactions of long duration among the Group I] Citrus Viroids, CVd‐IIa and CVd‐IIb were investigated by grafting buds from established citron (Citrus medica L.) sources containing single viroids to a common healthy seedling. In healthy tissues, the two viroids became established in approximately equal titres as a mixed infection. By contrast, tissues that grew from the CVd‐IIa or CVd‐IIb source buds contained only trace amounts of the heterologous invading viroids.

This interference between CVd‐IIa, a mild exocortis agent, and CVd‐IIb, the cachexia agent, was also demonstrated in the presence of CEVd, the severe exocortis agent but not a Group II viroid. When a CVd‐IIb bud was propagated on a citron containing CVd‐IIa, a dramatic reduction in the titre of CVd‐IIb was observed.

The interference between CVd‐IIa and CVd‐IIb indicates that the mild and relatively innocuous isolate, CVd‐IIa, can interfere with the replication and/or accumulation of the severe cachexia agent, CVd‐IIb, in citrus. This offers a potential practical approach for the control of cachexia in commercial plantings by “viroid interference”.
The comparative effects of three formulations of diazinon on cropping of a hybrid and a non‐hybrid strain of the cultivated mushroom Agaricus bisporus
Authors: WHITE P. F.
Published: February 2008

Three formulations of diazinon: flowable granules (FG); wettable powder (WP); and emulsifiable concentration (EC), which are used for the control of mushroom pests, were compared for toxicity towards a hybrid and non‐hybrid strain of the cultivated mushroom, Agaricus bisporus. With all formulations, yield and number of mushrooms were reduced according to dosage (linear trend). The EC was the most toxic and persistent formulation – equally so to both mushroom strains – and produced the most severe responses in all the parameters considered. The WP was the least toxic formulation. The hybrid strain was more susceptible to diazinon than the non‐hybrid, but not markedly so.
A screen of worldwide wheat cultivars for hydroxamic acid levels and aphid antixenosis
Authors: NICOL D. , COPAJA S. V. , WRATTEN S. D. , NIEMEYER H. M.
Published: February 2008

In a screen of seedlings of a worldwide range of 47 cultivars of Triticum (mainly T. aestivum) the concentration of the hydroxamic acid DIMBOA ranged between 1 and 8 mmol/kg fresh wt. In a bioassay in which alatae of the aphid Sitobion avenae were released among replicated test seedlings, there were highly significant correlations between aphid ‘preference’ and DIMBOA levels in the seedlings. The value of these results in work leading to the production of aphid‐resistant cultivars is discussed.
The impact of spiders and high temperatures on cereal aphid (Rhopalosiphum padi) numbers in an irrigated perennial grass pasture in South Australia
Authors: BARRO PAUL J. DE
Published: February 2008

Spiders were the most important group of aphid natural enemies in an irrigated perennial grass pasture. The Lycosidae and Linyphiidae were the only families encountered. An exclusion experiment found predation by spiders to be an important factor in controlling aphid numbers. Together with high temperatures, they maintained aphid numbers at a lower than expected level.
Effect of leaf age and nitrogen fertilisation on sporulation of crown rust (Puccinia coronata var. lolii) on perennial ryegrass (Lolium perenne L.)
Authors: PLUMMER ROSETTA M. , HALL R. L. , WATT TRUDY A.
Published: February 2008

Individual leaves of perennial ryegrass cv. Aberystwyth S23 of two leaf ages and at two levels of nitrogen fertilisation were point inoculated with Puccinia coronata f.sp. coronata in a growth chamber. In general, there was no significant difference in the lifespan of inoculated versus control leaves. However, the higher rate of nitrogen extended leaf lifespan more markedly in rusted than in control leaves.

Uredospore production varied according to leaf age: colonies on juvenile leaves produced three times as many spores as those on mature leaves.
The influence of primary infection date and establishment of vector populations on the spread of yellowing viruses in sugar beet
Authors: WERF W. VAN DER , WESTERMAN P. R. , VERWEIJ R. , PETERS D.
Published: February 2008

In three field experiments in 1985 and 1986, we studied the effect of the date of primary infection on the spread of beet yellows closterovirus (BYV) and beet mild yellowing luteovirus (BMW) from artificially inoculated sugar beet plants. Laboratory‐reared vector aphids, Myzus persicae, were placed on these sources of virus. There was no substantial natural immigration of vectors or viruses. In two experiments, one with BMYV in 1985 and the other in BYV in 1986, populations of vector aphids remained low and there was little virus spread, i.e. c. 50 infected plants from one primarily infected source. The cause of this small amount of spread was the low number of vector aphids. In the third experiment, with BYV in 1986, large populations of M. persicae developed and there was substantial virus spread: c. 2000 infected plants in the plots which were inoculated before canopy closure. In later‐inoculated plots in the same experiment, there was much less spread: c. 100 infected plants per virus source plant. Differences between fields in predator impact are implicated as the most probable factor causing differences in vector establishment and virus spread between these three experiments. Virus spread decreased with later inoculation in all three experiments.

A mathematical model of virus spread incorporating results from our work has been used to calculate how the initial proportion of infected plants in a crop affects the final virus incidence. This model takes into account the effect of predation on the development of the aphid populations. The processes underlying the spread and its timing are discussed.
Transmission of barley yellow dwarf virus by field collected aphids (Homoptera: Aphididae) and their relative importance in barley yellow dwarf epidemiology in southwestern Idaho
Authors: HALBERT SUSAN E. , CONNELLY B. JUNE , BISHOP G. W. , BLACKMER JACQUELYN L.
Published: February 2008

Populations of cereal aphids were sampled from 1985–1988 and assayed for transmission of barley yellow dwarf virus (BYDV), Rhopalosiphum padi, Rho‐palosiphum maidis, Sitobion avenae, Metopolophium dirhodum, Schizaphis graminum and Macrosiphum euphorbiae collected from host plants transmitted BYDV in bioassays. Of the 1028 Diuraphis noxia collected from plants, one may have transmitted BYDV. The isolate involved resembled SGV in serological and biological characteristics, but since it was not recoverable by any of more than 800 D. noxia subsequently tested, we suspect it may have been a contaminant.

Among those aphids collected during the autumn from a suction trap adapted for live collection, R. padi transmitted BYDV most frequently. Other trapped species which transmitted BYDV included: R. maidis, Rhopalosiphum insertum, Macrosiphum euphorbiae, Metopolophium dirhodum and Ceruraphis eriophori. An adapted Infectivity Index indicated that R. padi is by far the most important vector of BYDV during the autumn sowing season in southwestern Idaho. Male R. padi consistently transmitted BYDV more frequently than did females collected during the same period.
Wild Narcissus species as a source of resistance to Fusarium oxysporum f.sp. narcissi
Authors: LINFIELD CHRISTINE A.
Published: February 2008

Thirty three species and varieties of Narcissus plus seventeen cultivars with recent species parentage were screened for resistance to Fusarium oxysporum f.sp. narcissi. Accessions were either wholly resistant (bulbs remaining uninfected), partially resistant (a variable portion of the bulbs infected) or susceptible (all of the bulbs infected). Although a pattern of resistance was found among the species tested the genetic basis of the resistance is not known.
Ploidy doubling by callus culture of potato dihaploid leaf explants and the variation in regenerated plants
Authors: FLEMING M. L. M. H. , DE M. J. , POWELL W.
Published: February 2008

Somatic chromosome doubling of potato dihaploids was achieved by culturing callus from leaf pieces derived from glasshouse and in vitro grown plants. The glasshouse‐grown leaves produced better callus on average but there was no significant difference between the average number of plantlets per callus regenerated from the two types of material.

Mixtures of 2x and 4x plants were obtained from callus culture and the proportions of each ploidy type varied with the dihaploid genotype. Leaflet length/breadth ratios were chiefly determined but ploidy but there was variation within ploidy groups. There were also differences in blight and cyst nematode resistance between tetraploids derived from the same dihaploid.
Chilling tolerance in February seeded Chaite rices (Oryza sativa) of Nepal
Authors: STHAPIT B. R. , WILSON J. M.
Published: February 2008

Five Chaite and three main season rices Oryza sativa genotypes were examined to assess the effect of low temperature on the germination and growth of roots and shoots, root regeneration capacity, the extent of chlorophyll synthesis of etiolated seedlings, total chlorophyll content and photo‐chemical efficiency (Fv/Fm) of chilled plants. Cultivated differences in the ability to germinate and grow at low temperatures have been found. The poor ability of Chaite rices to tolerate photo‐oxidative tissue damage during January and February seemed to be the major factor resulting in poor seedling growth.
The description of the growth stages of annual grass weeds
Authors: LAWSON H. M. , READ M. A.
Published: February 2008

The decimal code for the growth stages of cereal crops, devised by Zadoks, Chang & Konzak (1974) and expanded by Tottman & Makepeace (1979) and Tottman (1987) was found to be generally applicable to annual graminaceous species encountered as arable weeds in the United Kingdom. For the great majority of growth stages no difficulties were found in using the Zadoks code, but agronomists, crop protection advisers and farmers identified practical problems in assessing the transition from tillering to stem elongation to node development in certain species. It is recommended that these problems could be minimised if label and advisory statements avoided the use of GS30 ‐ pseudostem (leaf sheath) erection ‐ as a growth stage description for annual grass weeds. The benefits of being able to use one key for graminaceous crops and weeds in the United Kingdom considerably outweigh any inconvenience caused by the need to amend herbicide labels to achieve this objective.
Resistance in sorghum to the shoot fly, Atherigona soccata: epicuticular wax and wetness of the central whorl leaf of young seedlings
Authors: NWANZE K. F. , PRING R. J. , SREE P. S. , BUTLER D. R. , REDDY Y. V. R. , SOMAN P.
Published: February 2008

Sorghum genotypes known to be resistant or susceptible to shoot fly, Atherigona soccata Rondani were examined by scanning electron microscopy for differences in epicuticular wax structure and wetness of the central leaf whorl. Two major types of wax structures were observed: shoot fly resistant and moderately resistant genotypes were characterised by a smooth amorphous wax layer and sparse wax crystals while susceptible genotypes possessed a dense meshwork of crystalline epicuticular wax. The density of wax crystals decreased from the third leaf to the seventh leaf stage and was related to both seedling age and leaf position. Water droplets on susceptible genotypes with dense wax crystals showed spreading at the edges indicating a tendency to wet easily. In resistant genotypes with less dense wax crystals the droplets remained intact and did not spread.
The effects of temperature on development of the large narcissus fly (Merodon equestris)
Authors: COLLIER ROSEMARY H. , FINCH S.
Published: February 2008

Eggs, larvae, pupae and adults of the large narcissus fly (Merodon equestris) were reared at a series of constant temperatures between 9–24°C. Egg development required from 37 days at 9°C to 7 days at 21.5°C. The low‐temperature threshold for development was 6.7°C. Larvae reared at 1424°C were fully‐grown after 18 weeks, but it took much longer for such insects to pupate, and adult flies emerged only after about 45 weeks of development. Large narcissus flies enter diapause during the larval stage and overwinter as fully‐fed larvae, forming pupae in the following spring. Post‐winter pupation and pupal development took from 169 days at 10°C to 36 days at 21.5°C. Of this, pupal development required from 91 days at 10°C to 19 days at 21.5°C. The low‐temperature threshold for post‐winter pupation and pupal development was 7.1°C, and for pupal development alone, 7.2°C.

Females maintained at or below 19°C laid few eggs, whereas some females kept at or above 21.5°C laid more than 100 eggs (mean 69 ± 36). Approximately 50% of females maintained at or above 21.5°C laid less than 10 eggs during their lifetime. The mean egg‐laying time was 6 to 9 days. Although temperatures at or below 19°C inhibited mating, once a female had mated, such temperatures did not prevent oviposition.
Rottboellia yellow mottle virus, a new sobemovirus affecting Rottboellia cochinchinensis (Itch grass) in Nigeria1
Authors: THOTTAPPILLY G. , van LENT J. W. M. , ROSSEL H. W. , SEHGAL O. P.
Published: February 2008

A hitherto undescribed virus, termed rottboellia yellow mottle virus (RoYMV), affecting Rottboellia cochinchinensis (syn. R. exaltata, itch grass) at Ibadan, Nigeria, was investigated.

RoYMV virions are isometric, c. 29 nm in diameter, and sediment homogeneously at 114s. In isopycnic CsCl gradients, RoYMV virions band sharply at a buoyant density of 1.379 g cm‐3, but in Cs2SO4 gradients, virions band at two zones, at the densities of 1.300 g cm‐3 and 1.325 g cm‐3. Treatment with EDTA at pH 8.0 reduced the sedimentation value of RoYMV to c. 87s and rendered it susceptible to proteinase‐K, SDS and NaCl. The apparent molecular weight of RoYMV coat protein was c. 27 000. Virions encapsidate a single‐stranded RNA of mol. wt 1.4 × 106 Da. Besides R. cochinchinensis, RoYMV was mechanically transmissible only to maize (Zea mays). No reaction occurred when RoYMV was tested against antisera to 44 isometric plant viruses (belonging to 12 groups), including several that affect Gramineae.

RoYMV exhibits striking similarities with other viruses belonging to the sobemovirus group, and it is tentatively designated as a new member of the sobemovirus group.
Survey of two beet viruses in South Kazakhstan and Central Asia
Authors: ROGOV V. V. , SOLOMYAKINA S. N. , KARASEV A. V.
Published: February 2008

During two surveys of beet root crops in South Kazakhstan and Central Asia conducted in 1988 and 1989, 465 of 990 samples were found to contain beet mosaic virus (BMV) by double‐antibody sandwich (DAS) ELISA. BMV infection was widely scattered in the area surveyed, and its incidence varied considerably, reaching 100% in some fields adjacent to beet seed crops. BMV isolates from Kazakhstan, Kirgizia, Uzbekistan and Ukraine were found to be serologically closely related in DAS‐ELISA test. Beet yellows virus (BYV) was not detected in any location surveyed in South Kazakhstan and Central Asia. BYV spread into the area is probably prevented by its geographical isolation.