bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical techniques for control of stem canker and black scurf (Rhizctonia solani) disease of potatoes
Authors: HIDE G. A. , CAYLEY G. R.
Published: February 2008

Thiabendazole, iprodione and benodanil were tested for control of stem canker and black scurf disease of potatoes using seed tubers with or without black scurf planted in soil infested or not with Rhizoctonia solani. Dormant seed tubers were treated with fungicide dusts, dips or sprays and before planting dusts were applied to soil or to sprouts on seed tubers.

Plants grown from seed tubers with black scurf had more stem canker, stolon infection and Thanatephorus cucumeris and progeny tubers had more black scurf than from seed without black scurf. Infesting soil with R. solani increased black scurf but not stem canker or stolon infection.

Fungicide treatment of seed tubers controlled all phases of the disease and sprout and soil treatments also had significant effects. Numbers of tubers in July were usually increased by treatment although by harvest many small tubers (>3 cm) had been resorbed. Fungicide treatment substantially increased yield only when shoot tips were pruned by R. solani.

Regression analyses showed that stolon pruning, Thanatephorus and black scurf were significantly related to stem canker, and numbers of tubers in July but not in September were inversely related to stolon pruning.

The significance of sources of inoculum and the effects of controlling disease on tuber production are discussed in relation to methods of fungicide use.
Association of raspberry bushy dwarf virus with raspberry yellows disease; reaction of Rubus species and cultivars, and the inheritance of resistance.
Authors: Jones A. T. , Murant A. F. , Jennings D. L. , Wood G. A.
Published: February 2008

The agent of raspberry yellows disease is transmitted by grafting but not by aphids and is resistant to thermotherapy. Further studies showed that it is transmitted by inoculation of sap through seed; it is probably transmitted to plants by pollination. Raspberry bushy dwarf virus (RBDV) shares all these attributes and is known to infect all yellows‐sensitive raspberry cultivars except Puyallup and Sumner; however, neither of these cultivars has been tested by graft inoculation with RBDV. RBDV commonly infects plants symptomiessly, even those of yellows‐sensitive cultivars, but it induced yellows when inoculated either manually to Norfolk Giant raspberry or by grafting to a yellows‐sensitive raspberry selection. The evidence suggests that RBDV is the causal agent of yellows disease but that symptom expression is greatiy dependent on genetic and environmental factors. Many red raspberry cultivars are resistant, probably immune, to the type culture of RBDV and this character was shown to be conferred by a single dominant gene designated Bu.
Effects of aerial pollutants on the growth and yield of spring barley
Authors: BUCKENHAM A. H. , PARRYy M. A. J. , WHITTINGHAM C. P.
Published: February 2008

Open‐topped chambers were used to determine the effect of field concentrations of aerial pollutants on the growth and yield of spring barley. Experiments were conducted in the Marston Valley, Bedfordshire, where sulphur dioxide and fluoride are the major pollutants. The charcoal filtered chambers enabled pollutant concentrations to be reduced by 60–70%. Cleaning the air increased straw and grain yields. The filtration was non‐selective and did not identify the injurious agent. The chambers were found to accelerate the crop's development by 7–8 days and reduce yield by suppressing tillering.
Determination of firmness of field‐grown tomatoes during storage in controlled atmosphere or ripened at different temperatures
Authors: THOMAS T. H. , DREW R. L. K. , GOODENOUGH P. W.
Published: February 2008

Durometer readings indicated that although differences in firmness of maturegreen fruits were small, there were large varietal differences in red‐ripe fruit after preor post‐storage ripening treatment at different temperatures. Such differences were positively related to the performance of the different cultivars in controlled atmosphere storage. Thus the durometer provides a simple means of assessing the firmness of ripe tomato fruits and hence of predicting the long‐term storage potential of different cultivars.
The life‐history of the leaf‐curling plum aphid Brachycaudus helichrysi in Northern Ireland and its ability to transmit potato virus YC(AB)
Authors: BELL A. C.
Published: February 2008

The life‐history of leaf‐curling plum aphid, Brachycaudus helichrysi was studied in Northern Ireland from 1977–1980. It was shown that the life cycle differed in several respects from those of geographically distinct populations, reported by other authors, especially with regard to the timing of egg hatch. Body length and antennal segment measurements of the adult stages on Prunus spinosa and Trifolium pratense correlated well with published dimensions for the species.

Virological studies showed B. helichrysi to be capable of transmitting potato virus YC(AB) with a vector efficiency of 34%. This value is higher than previous estimates and enhances the significance of the species as a virus vector in potato crops early in the growing season.
Influence of temperature and duration of leaf wetness on infection of Acyrthosiphon kondoi with Erynia neoaphidis
Authors: MILNER R. J. , BOURNE JENNY
Published: February 2008

Bioassays were carried out to examine the influence of temperature and duration of leaf wetness on the infectivity of an isolate of Erynia neoaphidis for its aphid host Acyrthosiphon kondoi. Preliminary experiments demonstrated that primary spores produced in vitro were as infectious as those formed in vivo. No consistent effect of temperature on infectivity of primary spores could be detected. The time taken to kill an aphid increased as temperature decreased, from 3–5 days at 20 °C to 12–15 days at 8 °C, suggesting a threshold for disease development of 4 °C. Increasing duration of the period of leaf wetness up to 24 h after inoculation increased the final level of infection. At 20 °C, a minimum moisture period of 3 h was required for infection with maximum infection occurring after about 7 h. These times increased slightly at 15 °C but extending to 7 and 16 h respectively at 10 °C. The epizootiological implications of these results are discussed with reference to previously published data on in vivo production of primary spores of E. neoaphidis.
The effects of barley yellow dwarf virus, aphids and honeydew on Cladosporium infection of winter wheat and barley
Authors: AJAYI OLUPOMI , DEWAR ALAN M.
Published: February 2008

Prior infection of both wheat and barley plants by BYDV predisposed their ears to infection by Cladosporium spp. and Verticillium spp. Aphids and honeydew increased the incidence of Cladosporium on wheat ears but not on barley. This difference between crops was attributed to the larger number ot aphids on the wheat. In the glasshouse, aphids and honeydew, but not honeydew alone, increased Cladosporium populations.
Effects of delaying fungicide treatment on the incidence of gangrene in stored potato tubers
Authors: HIDE G. A. , CAYLEY G. R.
Published: February 2008

Potato titbers infested with Phoma exigua var. foveata were uniformly wounded and sprayed or dipped in fungicide suspensions either immediately or after periods of up to 21 days' storage at 5, 10, 15 or 20 °C. Tubers were then stored at 5 °C and gangrene assessed after 12 wk.

Incidence of gangrene on untreated tubers was progressively decreased by increasing the length of storage at 15 or 20° (curing) but was not affected by 3 days' storage at any temperature. Fungicide treatment immediately after wounding gave best control of the disease; treatment after 3 days' delay was less effective and after 14 or 21 days was usually ineffective. Gangrene was decreased by fungicides more on tubers stored for 3 or 7 days at 5 °C than at higher temperatures.

Control of gangrene by curing or fungicides diminished when the amount of inoculum on tubers was increased. Increasing the amount of fungicide applied improved control and fungicides were more effective in decreasing gangrene on cut and crush wounds than on cut wounds. At the arbitrary concentrations used in these experiments imazalil gave better disease control than thiabendazole, prochloraz, carbendazim plus quinolin 8‐ol or triadimefon.
Chenopodium necrosis: a distinctive strain of tobacco necrosis virus isolated from river water
Authors: TOMLINSON J. A. , FAITHFULL ELIZABETH M. , WEBB M. J. W. , FRASER R. S. S. , SEELEY N. D.
Published: February 2008

A distinctive strain of tobacco necrosis virus (TNV) of unknown source was repeatedly isolated from water of the River Avon (Warwickshire) and two of its tributaries (R. Swift and R. Alne) using a technique developed for the concentration and isolation of water‐borne bacteriophages. The same strain was isolated from the rivers Cam and Thames and from Lake Esthwaite (Cumbria) together with tomato bushy stunt virus.

The TNV strain, designated Chenopodium necrosis (TNV‐CN) was mechanically transmissible to C. amaranticolor and C. quinoa in both of which it caused local lesions and systemic infection. TNV‐CN caused no infection when inoculated to tobacco (Nicotiana tabacum cv. White Burley) plants.

The virus was not adsorbed to soil, could be isolated from leachate of soil in which systemically infected C. quinoa were grown and C. quinoa plants became infected when grown in soil watered with suspensions of the virus.

The virus was not transmitted by Myzus persicae but was vectored by the zoospores of a lettuce isolate of Olpidium brassicae.

TNV‐CN was infective after 10 min at 85 °C., 3 wk at 20 °C and when diluted to 10‐8 but not 10‐9. Purified virus preparations contained c. 26 nm isometric virus particles.

TNV‐CN contained single‐stranded RNA (mol. wt 1·5 × 106) and one protein (mol. wt c. 26·4 × 103) which co‐electrophoresed in polyacrylamide gels with the protein of the D strain of TNV (TNV‐D). Analytical centrifugation of TNV‐CN indicated a single component virus with the same sedimentation coefficient (s20, w= 115S) and buoyant density (1·385) in a CsCl gradient as those of TNV‐D. TNV‐CN and TNV‐D were indistinguishable serologically.
Micro sprayers for the laboratory application of pesticides
Authors: COGGINS S. , BAKER E. A.
Published: February 2008

The microtip nozzle assembly described by Uk (1978) has been modified to provide a reliable and versatile sprayer for the laboratory application of pesticide formulations. The improved performance has been achieved through the introduction of knurled thimbles giving controlled adjustment of needle and stylus settings and by the provision of an offset liquid reservoir (0·1–2 ml) either pressurised or non‐pressurised.

The device, which delivers monosize droplets (in‐flight diameter 50–500 μm) at velocities ranging from 0·5–20 m s‐1 has been used for aqueous and oil solutions, water dispersible powders and emulsifiable concentrates of varying concentration (0·1‐30g a.i. litre‐1) and is particularly suitable for the application of radiolabeled chemicals.
Characteristics of the common bean, Phaseolus vulgaris, associated with resistance to the leafhopper Empoasca kraemeri
Authors: GALWEY N. W.
Published: February 2008

Experiments were conducted using the common bean, Phaseolus vulgaris, and its most important pest in Latin America, Empoasca kraemeri, in order to assess the value of insect counts and various plant characteristics as selection criteria in a plant breeding programme. The combination of insect counts with measurements of damage symptoms should make it possible to distinguish tolerance from the resistance mechanisms of antibiosis and non‐preference. By this means, and by a knowledge of the plant characteristics associated with resistance, different forms of resistance may be combined in the progeny of crosses.

In a comparison of two contrasting genotypes the more severely damaged genotype was the more heavily infested at early stages of plant growth, but had the lower level of infestation at later stages. The association of high early counts with high subsequent damage was not confirmed in an experiment on six genotypes, but the association of high damage with low late counts was partially confirmed. These results indicate that the level of early infestation of E. kraemeri is not consistently reflected in the subsequent levels of damage which P. vulgaris genotypes display. This suggests that these two criteria represent distinct forms of resistance which can be combined in hybrid progeny.

Resistance was also associated with late maturity, indeterminate growth habit, purple flowers and black or beige seeds. However, consumer preferences and the requirements of agricultural systems place constraints upon the use of these relationships in resistance breeding.
Studies on death of deteriorated barley seeds in soil
Authors: PERRY D. A. , ELLERTON D. R.
Published: February 2008

Seeds of barley cv. Golden Promise which had been deteriorated by storing at 20% moisture content and 30 °C and which all had viabilities >85% were treated with a slurry of calcium peroxide and with dusts of a mercurial and a non‐mercurial fungicide. Calcium peroxide improved seedling emergence in wet soil conditions and deteriorated seeds benefited more than non‐deteriorated seeds. The fungicide dusts had no effects.

In controlled conditions at 20 °C, deteriorated seeds in wet soil died mainly within 2 days of sowing and they were more tolerant if they were placed in moist soil for 2 days before transfer to wet soil. Application of a mercurial fungicide and sterilizing the soil and the surface of seeds improved emergence but did not restore it to the level in moist soil.

Fusarium culmorum, F. equiseti, Mucor spp. and Mortierella spp. dominated the fungus flora isolated from surface sterilised dead seeds in wet soil. When the fungi were inoculated to seeds, they increased the proportion which died in wet soil but only at high inoculum levels. It was concluded that they acted primarily as saprophytes depriving seeds of oxygen and secondarily as seed colonisers.
The influence of anoxia and ethanol on barley seed death
Authors: ELLERTON D. R. , PERRY D. A.
Published: February 2008

Survival of deteriorated barley seeds in wet soil was improved by exposure to 70% oxygen compared with that in air and decreased by the imposition of anoxia. Deteriorated seeds were more sensitive to anoxia than non‐deteriorated seeds, the former died within 4 days, while the latter survived more than 7 days.

Ethanol accumulated in non‐deteriorated seeds in wet soil conditions during the first 24 h and thereafter declined, while it increased to higher concentrations over 3–4 days in deteriorated seeds. High concentrations of ethanol were recorded in seeds in anaerobic conditions regardless of the level of deterioration.

It was concluded that oxygen diffusion to the seeds was severely restricted in wet soil resulting in a switch to anaerobic respiration, the products of which, indicated by ethanol content, accumulated within the tissues. Non‐deteriorated seeds tolerated higher concentrations of ethanol than deteriorated seeds and the coleorhiza extruded through the covering layers more rapidly facilitating gaseous exchange, while in the latter, anaerobic products accumulated to toxic levels.
Movement, persistence and performance of fungitoxicants applied as pruning wound treatments on apple trees
Authors: GENDLE P. , CLIFFORD D. R. , MERCER P. C. , KIRK S. A.
Published: February 2008

The systemic fungicides triadimenol, fenpropimorph, furmecyclox and carben‐dazim, applied to pruning wounds as solutions in a non‐aqueous solvent containing N‐methyl–2‐pyrrolidone moved predominantly towards the trunk.

Coriolus versicolor, introduced deliberately, moved both proximally and distally irrespective of whether it was introduced in the dormant or growing season. Natural resistance to damage by chemical or C. versicolor appeared to be greater in the growing than in the dormant season and was inhibited when a cationic surfactant was used to aid penetration of fungitoxicant into the wood.

Against C. versicolor the non‐systemic fungicide captafol was ineffective, furmecyclox or fenpropimorph gave some protection and triadimenol was very effective. Carbendazim, although inactive against wood‐rotting basidiomycetes, moved extensively within the wood and persisted well, and so could be an effective treatment for ascomycete pathogens. It also stimulated callus formation.

The mercuric oxide preparation Santar was effective in these experiments and also stimulated callus formation.
Bioassay of a purified nuclear polyhedrosis virus against Heliothis armigera
Authors: FLATTERY K. E.
Published: February 2008

A precise bioassay method, which is not limited by lack of field applicability, as are peroral administration techniques, is described. Purified nuclear polyhedrosis virus (NPV) suspensions were assayed against third and fourth instar Heliothis armigera larvae to provide standards for additive and field testing. Third instar larvae proved to be approximately one hundred times more susceptible to the NPV disease than fourth instar larvae. The minimum time to mortality was 4 days.
The relation between cowpea golden mosaic and its vector, Bemisia tabaci
Authors: ANNO‐NYAKO F. O. , VETTEŃ H. J. , ALLEN D. J. , THOTTAPPILLY G.
Published: February 2008

Adult whiteflies (Bemisia tabaci) acquired the agent of cowpea golden mosaic (CGM‐A) within 7 min and transmitted during 2 min inoculation access. Nymphs also acquired CGM‐A and retained it through the pupal stage. Efficiency of transmission reached 90% when the acquisition period was increased to 36 h. The minimum latent period of CGM‐A in B. tabaci was 8 h, and the median latent period (LP50) about 12 h. Transmission was generally intermittent and declined throughout the period of 21 days which was the maximum time insects remained infective. Female whiteflies were more efficient vectors than males. B. tabaci acquired CGM‐A from plants inoculated only 60 h previously. The epidemiological implications of these findings are discussed.
Tolerance of potato to potato cyst nematodes (Globodera rostochiensis and G. pallida) in relation to the growth and efficiency of the root system
Authors: TRUDGILL D. L. , COTES L. M.
Published: February 2008

Potato cyst‐nematode (Globodera rostochiensis) was shown to damage potato plants in several ways. A major cause of damage, affecting all cultivars to a similar extent, was a reduction in the top to root weight ratio. Intolerant cultivars also suffered a reduction in the weight and length of their root systems when grown in heavily infested soil, the combined damage resulting in a marked decrease in nutrient uptake and top growth. In addition intolerant cultivars tended to senesce prematurely when heavily infested, further decreasing their leaf area duration and yield.

Cultivars tolerant of potato cyst‐nematode (PCN) differed from intolerant cultivars in that their root systems tended to grow larger in heavily infested soil than in lightly infested or nematicide‐treated soil, so partly compensating for the reduction in the top/root ratio. In a growth cabinet experiment Maris Anchor was more severely damaged at a soil temperature of 10 than at 15 °C. In a glasshouse, without temperature control, differences were obtained between cultivars in small pots (10 cm) in the effect of PCN on root growth which correlated well with differences in tolerance obtained in field trials.
The microflora of ripening barley grain and the effects of pre harvest fungicide application
Authors: HILL R. A. , LACEY J.
Published: February 2008

Newly‐emerged ears of barley soon became colonised by micro‐organisms with numbers increasing to 5·8 × 105 viable propagules/g dry weight by harvest. Bacteria were numerically predominant throughout. Yeasts and yeast‐like fungi were also numerous during the early stages of grain development but were exceeded by propagules of filamentous fungi during ripening, with Cladosporium spp., Alternaria alternata, Epicoccum purpurascens and Verticillium lecanii most abundant. Numbers of most micro‐organisms were greatest in a wet season but Alternaria was equally abundant in hot dry weather. Application of fungicides at or after anthesis modified the grain microflora. Captafol was most effective overall in decreasing numbers of fungi. However, benomyl decreased Cladosporium inoculum more than catpafol but was ineffective against Alternaria which became more numerous on benomyl‐treated grain than on untreated. Yield increases of up to 4% were obtained by late fungicide treatment, least in a hot, dry year. Germination was also increased by some treatments by up to 5%.
Necrosis in field beans (Vicia faba) induced by interactions between bean leaf roll, pea early‐browning and pea enation mosaic viruses
Authors: COCKBAIN A. J. , WOODS R. D. , CALILUNG V. C. J.
Published: February 2008

Mixed infections with two or three viruses ‐ bean leaf roll (BLRV), pea early‐browning (PEBV) and pea enation mosaic (PEMV) ‐ were detected in plants showing leaf curling, stunting and necrosis in a crop of field beans grown for seed in 1980. In glasshouse tests, field bean plants infected with any one of these viruses showed no necrosis, and plants infected with PEBV and PEMV together showed symptoms of PEMV only. However, mixed infection with BLRV and PEMV almost invariably induced severe stunting and leaf necrosis, and infection with BLRV and PEBV often induced both leaf and stem necrosis and sometimes caused early death. Thus it seems that the necrotic symptoms seen in the field were induced by interactions between BLRV and the other viruses.

No transmission of PEBV was detected through seed harvested from the crop, but up to 5% transmission was detected through seed from experimentally‐infected plants. The infected seedlings were symptomless.
Seed survival and periodicity of seedling emergence in ten species of annual weeds
Authors: ROBERTS H. A. , BODDRELL JUNE E.
Published: February 2008

Seeds or fruits of 10 species of annual weeds were collected in each of 3 years and mixed with the top 7 · 5 cm of sterilised soil (confined in cylinders sunk in the ground outdoors and cultivated three times yearly. The numbers of seedlings emerging were recorded for 5 yr and the numbers of viable seeds remaining then determined. Emergence of Anagallis arvensis, Anchusa arvensis, Chaenorrhinum minus and Euphorbia peplus was mainly in spring; Lamium amplexicaule and Myosotis arvensis also had a spring peak but emergence continued in summer and autumn. Seedlings of Aphanes arvensis appeared almost entirely in autumn and those of Lamium purpureum between May and October. Veronica arvensis had spring and autumn peaks, while Fumaria densiflora showed no definite pattern. Except for Anagallis arvensis and F. densiflora, in which there was apparent innate dormancy due to the seed coat, most seedlings appeared in the first year with a decrease, usually exponential, from year to year. This was most rapid in C. minus and E. peplus, of which few viable seeds remained after 5 yr. Seed survival for the other species ranged from 2·6% of those sown for Anchusa arvensis to 14·8% for F. densiflora.
Germinability and enforced dormancy in seeds of species of indigenous grassland
Authors: WILLIAMS E. D.
Published: February 2008

Germination of seeds of a range of species from indigenous grassland was tested at an alternating temperature regime in incubators, soon after they were shed in 1978 and also after various intervals of dry storage at outdoor ambient temperatures. Concomitant investigations were made of seedling emergence from and seed survival at different depths of soil in pots; Poa annua and Poa trivialis were investigated separately in 1979.

Almost all seeds of Lolium perenne, Cynosurus cristatus, Festuca rubra and Holcus lanatus germinated readily, but c. 30% of Deschampsia caespitosa seeds and c. 15% of fresh, early‐shed Agrostis capillaris did not germinate until they were also given gibberellic acid. However, more late‐ than early‐shed seed of the latter two species germinated and their seeds became more germinable with increasing length of storage. Of the dicotyledonous species tested, germination of Cerastium fontanum ssp. glabrescens was rapid and complete, but that of Ranunculus spp. was particularly protracted. All Ranunculus repens seeds and a large proportion of Ranunculus acris seeds were highly dormant.

Species differed greatly in their ability to emerge from and persist at different depths in pots. The most persistent species after 15 months were R. repens (69%), A. capillaris (39%), Luzula campestris (37%), C. fontanum ssp. glabrescens (30%), P. trivialis (8%), D. caespitosa (7%) and H. lanatus (3%). A mean of 42% of P. annua and 16% of P. trivialis seeds persisted from autumn 1979 until late spring 1980, but pre‐imbibing the seeds decreased seed persistence to 12% and 4% respectively.

The results are discussed in relation to previously published information on the germination biology of the species and to the different abilities of the species to become part of the soil seed population.
Cavity spot of carrots ‐ observations on a commercial crop
Authors: SCAIFE M. A. , TURNER MARY K. , BARNES A. , HUNT J.
Published: February 2008

A single field of commercially‐grown carrots was sampled in September at 16 points for cavity spot incidence. Carrot tops, root core and peel were analysed for N, P, K, Ca and Mg, and soils were analysed for organic C, total N, available P, K, Ca, Mg and Na, pH, conductivity and chloride.

The incidence of the disorder varied from 0–96% within a small area of field, thus tending to rule out explanations for cavity spot based entirely on weather, genotype etc.

Several types of lesion were recorded in addition to ‘typical’ cavity spot, and their incidence was found to be mutually correlated. Most of these (including splitting) were positively correlated with cavity spot, and tended to be positively related to concentrations of macroelements in the carrot peel (especially N and Ca): however, ‘scabs’ were very strikingly dissociated from cavities (both on a plot and individual root basis). This dissociation appeared to be connected with soil pH, in that scabs were most common above pH 6‐5, whereas cavities were most frequent below this pH.
Association of viruses with two protozoal pathogens of the honey bee
Authors: BAILEY L. , BALL BRENDA V. , PERRY J. N.
Published: February 2008

Undisturbed honey bee colonies near Rothamsted were commonly infected with a filamentous DNA virus (FV) which was usually associated with Nosema apis in infected adult individuals and occurred most frequently about June. No symptoms were caused by FV, which appeared less harmful than either black queen‐ceil virus (BQCV) or bee virus Y (BVY), two isometric RNA viruses also associated with N. apis. Bee virus X, another isometric RNA virus distantly related to BVY, was not associated with N. apis, but prevailed in winter and was then associated significantly with Malpighamoeba mellificae in dead individuals, although it frequently multiplied alone. Results of laboratory experiments supported conclusions made from the field observations about these relationships and their pathology.
Control of ergot in pearl millet through pollen management*
Authors: THAKUR R. P. , WILLIAMS R. J. , RAO V. P.
Published: February 2008

Four pearl millet F, hybrids, ICH‐118, ICH‐220, BJ‐104, and ICH‐206, which are highly susceptible to ergot, were grown one/season in isolation plots and in a demonstration plot during the four rainy seasons of 1978‐81, respectively, alone and mixed with an early flowering variety SC‐2(M)5‐4, which is less susceptible to ergot (less than 10% severity) to test the hypothesis that increased pollen availability at the early stages of flowering in hybrids protects the hybrids from ergot infection. In 1978, the hybrid was grown with the pollen donor in a seed mixture (4 parts hybrid and 1 part pollen donor) and in other years one row of the pollen donor was planted between two, four, or eight rows of the hybrid. Ergot inoculations were made 3–4 times at protogyny flowering stage of the hybrids. Significant reductions in ergot infection and considerable increase in grain yields occurred in the hybrids when grown with the pollen donor line. The possible application of this control measure in farmers' fields is discussed.
Infection of lucerne (Medicago sativa) by Fusarium species
Authors: PEGG G. F. , PARRY D. W.
Published: February 2008

A limited field survey of lucerne crops on four Kent farms showed infection by Fusarium species to be widespread. Plants selected at random were for the most part free from aerial symptoms, but 90–100% showed browning of the lower stem and tap root. Fusarium avenaceum was most commonly isolated exceeding Verticillium albo‐atrum in four out of six sites. Other species isolated included F. culmorum, F. equiseti, F. graminearum, F. oxysporum, F. solani and F. tabacinum. Phoma medicaginis and Cylindrocarpon destructans were also found in roots and stems.

Isolates of F. avenaceum were either pathogenic or non‐pathogenic on a range of lucerne cultivars, some reducing leaf area and shoot dry weight. One isolate showed differential pathogenicity to cvs Europe, Vertus, Sabilt and Dupuits. No evidence was found to suggest that natural infection by Fusarium spp. was limiting to growth. The possible significance of lucerne as a reservoir for cereal fusaria is discussed.
Interaction between the fungicide metalaxyl and soil microorganisms on survival of Phytophthora cinnamomi
Authors: MALAJCZUK N. , BOUGHTON T. J. , CAMPBELL N. A. , LITCHFIELD R. T.
Published: February 2008

In soil leachates the fungicide, metalaxyl, eliminated sporangia production by Phytophthora cinnamomi as well as enhancing hyphal lysis. There was a marked interaction between lytic soil microorganisms, fungicide application and hyphal lysis.
A comparison of Australian bean yellow mosaic virus isolates using molecular hybridisation analysis
Authors: ABU‐SAMAH NORANI , RANDLES J. W.
Published: February 2008

Twenty‐nine isolates of bean yellow mosaic virus (BYMV), obtained over 5 yr by sampling of a limited area in south‐eastern South Australia and western Victoria (Collection I), resembled each other in host range and symptomatology. Three reference isolates and nine other isolates (Collection E) from across southern Australia differed in host range and symptomatology from each other, and from the members of collection I.

Molecular hybridisation analysis (MHA) using 3H‐complementary DNA specific to the RNA of the three reference isolates of BYMV (BYMV‐G, ‐Q and ‐S) showed that the isolates of collection I were more closely related to BYMV‐S, which originated from the same region, than to ‐G, or ‐Q which came from outside the region. None of the isolates in collection E were related by MHA to BYMV‐S. Only one showed low but significant homology with Q, and none showed homology with G, despite some similarities in host range and symptomatology to the reference isolates.

Neither host of origin nor the propagation host influenced percentage homology to reference isolates. The percentage hybridisation values obtained with the RNA of isolates showed no significant variation in homology during regular transfer by mechanical inoculation for 2 yr. We conclude that percentage homology as determined by MHA has an advantage over assessments of biological properties for discriminating between strains or variants of BYMV; it appears to be a stable property which can be determined semiquantitatively.
Insecticidal control of aphids and the spread of potato leafroll virus in potato crops in eastern Scotland
Authors: WOODFORD J. A. T. , HARRISON B. D. , AVEYARD C. S. , GORDON S. C.
Published: February 2008

Field experiments were carried out in eastern Scotland in 1976‐78 to test the ability of granular insecticides, applied to soil at planting, and of insecticide sprays applied to the foliage, to control aphids and spread of potato leafroll virus (PLRV) in potatoes. The three years provided contrasting opportunities for virus spread. In 1976, the main vector of PLRV, Myzus persicae, arrived in early June and multiplied rapidly in untreated plots, and PLRV spread extensively. In 1977, M. persicae arrived 4–6 wk later than in 1976 and most spread of PLRV, which was less than in 1976, occurred after the end of July. In 1978, few M. persicae were recorded but the potato aphid, Macrosiphum euphorbiae, arrived early and very large populations developed in untreated plots. However, little spread of PLRV occurred in 1978, supporting other evidence that M. euphorbiae is an inefficient vector of PLRV in field conditions.

In each year, granular insecticides decreased PLRV spread to a quarter or less of that in control plots. Thiofanox gave somewhat better and longer‐lasting control of aphid populations than disulfoton, especially of M. persicae, but did not give greater control of PLRV spread. Application of three (1976) or five (1977) sprays of demeton‐S‐methyl to plots treated with granular insecticides further improved the control of M. euphorbiae but had less or no effect on M. persicae, especially where organophosphorus resistant aphids (R1 strain) were found. These supplementary sprays of insecticide did not further improve the control of PLRV but, in 1978, four sprays of demephion or pirimicarb to plots not treated with granular insecticide decreased PLRV spread.

These data, together with previous findings, indicate that the amount of virus spread depends on the date of arrival and rate of multiplication of M. persicae in relation to the timing and effectiveness of removal of PLRV sources in crops. It is concluded that in Scotland insecticide granules should be used routinely only in crops of the highest grade of seed potato. Their use for other grades need be considered only in years following mild winters, when aphids can be expected to enter crops earlier and in larger numbers.
Methods of analysing data to compare effects on populations of carrot fly (Psila rosae) larvae on carrots of treatments with exponentially‐increasing doses of granular insecticide formulations
Authors: PHELPS KATHLEEN , THOMPSON A. R.
Published: February 2008

Effects of insecticide treatments were assessed by comparing the percentages of undamaged carrot roots on insecticide‐treated and untreated check plots. A dose‐response relationship based on a log‐log transformation was derived and illustrated with data for six insecticides from two field experiments.

Formulae are provided for estimating doses corresponding to given levels of decrease in the numbers of carrot fly larvae. Guidance is given on sample sizes needed and constraints on the accuracy of the estimates are stated. Examples are given of the use of the dose‐response relationship to compare insecticide treatments within and between experiments.
Effects of heavy metal salts on susceptibility of rice seedlings to brown spot disease
Authors: GIRI D. N. , SINHA A. K.
Published: February 2008

Heavy metal salts, known to induce phytoalexin production in different plant species, were used at dilute concentrations (10‐3 to 10‐5 M) in different treatments to control brown spot infection in rice seedlings caused by Drechslera oryzae. Foliage sprays, root‐dips for 24 h at the time of transplanting, or seed soaking for 24 h provided moderate to substantial protection to rice seedlings, at different stages after treatment, against artificial inoculation with the pathogen or natural infection under field conditions and mostly caused significant reductions in symptoms. Of the three methods, greatest and most durable protection was achieved with the wet seed treatment. The number of successful infections was appreciably reduced in most treatments and some also inhibited lesion expansion. Ferric chloride and nickel nitrate were the most effective and mercuric chloride the least effective of the chemicals tested. There was no fungitoxicity in leaf diffusates from 3‐ and 5‐wk‐old seedlings that had been treated with heavy metal salts and only mild toxicity in that from untreated, inoculated seedlings. However, treated seedlings inoculated at the 3‐and 5‐wk stages produced leaf diffusates with significantly greater toxicities which were in proportion to their abilities to resist attack.
Olive latent ringspot virus, a newly recognised virus infecting olive in Italy
Authors: SAVINO V. , GALLITELLI D. , BARBA M.
Published: February 2008

A manually transmissible virus, for which the name olive latent ringspot virus (OLRV) is proposed, was isolated from a symptomless olive tree. The virus was mechanically transmitted to test plants. Purified preparations of OLRV contained three classes of isometric particle, c. 28 nm in diameter, with sedimentation coefficients of 525 (T), 975 (M) and 1325 (B) and containing 0, 30 and 43% nucleic acid respectively. At equilibrium in CsCl gradients, the buoyant densities of T and M components were 1–29 and 1–43 g/cm3 respectively, whereas B component separated into two sub‐components with buoyant densities of 1–51 g/cm3 (BJ and 1–52 g/cm3 (B2). Particle preparations contained two species of single‐stranded RNA with mol. wt 1–40 times 106 and 2–65 times 106, both necessary for infectivity. The coat protein of OLRV, dissociated under strong denaturing conditions, separated into four components in polyacrylamide gel electrophoresis. Over 75% of the protein was found in a band with mol. wt 57 600, but all four components were recognised as oligomers of a monomeric form with mol. wt 14 300. OLRV was serologically unrelated to 26 different isometric plant viruses including 17 recognised nepoviruses. Its properties strongly indicate that it is a hitherto undescribed member of the nepovirus group.
The identification of the potato cyst nematodes Globodera rostochiensis and G. pallida by isoelectric focusing of proteins on polyacrylamide gels
Authors: FLEMING C. C. , MARKS R. J.
Published: February 2008

Isoelectric focusing on thin layers of polyacrylamide gel was used to separate proteins from the potato cyst‐nematodes Globodera rostochiensis and G. pallida. General protein patterns could be used to identify the two species, even from. single cysts. Staining for the enzyme phosphoglucomutase (PGM) also produced species specific patterns and the presence of PGM variation among G. pallida populations was revealed. The potential of isolectric focusing as a routine research and advisory tool in nematology is discussed.
Control of stem nematode, Ditylenchus dipsaci Coat race‘), by aldicarb and resistant crop plants
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER J. E.
Published: February 2008

Aldicarb at 1.5 or 4.5 kg ha‐1 applied around the seeds at sowing greatly increased the yields of a range of crop plants in soil heavily infested with stem nematode (Ditylenchus dipsaci, ‘oat race’). Yield responses could be largely explained by stem nematode control in onions, field beans, peas, Manod oats and maize but not in wheat, Maris Tabard oats, lucerne or sugar beet. Aldicarb lessened stem nematode attacks and lessened stem nematode increase in host plants.

The supposedly resistant oat Manod was susceptible, whereas Maris Tabard was resistant, as were Peniarth, Pennal, Panema, Pennant, Maris Quest and Milford, whose resistances derive from Grey Winter. Maris Tabard outyielded resistant Panema, Peniarth and Pennal and susceptible Maris Osprey and Manod on infested soil. ‘Tulip root’ is not an infallible guide to susceptibility of oats to stem nematode. We advocate using a mixture of nematode populations in breeding for resistance to stem nematodes.
A novel bioassay for herbicides used in wild oat control and for the assessment of their interactions with other xenobiotics
Authors: TAYLOR H. F. , LOADER M. P. C. , NORRIS S. J.
Published: February 2008

A bioassay is described which uses young oat seedlings to determine the activity of wild oat herbicides alone and in mixtures with other xenobiotics.

Test solution (10 μl) was pipetted into the first leaf sheath of the oat seedlings, and 24 to 48 h later, basal shoot sections were removed and cultured for 24 h on agar. The inhibition of leaf growth from these sections, compared with control sections, was an assessment of herbicidal activity. Marked inhibition occurred when as little as 0–5 to 1 ‐0 μg of either diclofop‐methyl or diclofop had been applied to each plant. Wheat and barley seedlings were unaffected by 12 μg of these herbicides, reflecting their known selectivity in cereal crops.

The assay was used to evaluate the antagonisms of diclofop‐methyl and diclofop activity by 2,4‐D, MCPA, 2,3,6‐TBA and also related ‘non‐auxins’ (3,5‐dichloro‐phenoxyacetic acid and 2,3,5‐TIBA). Diclofop‐methyl was compatible with the 1‐methylheptyl ester of (4‐amino‐3,5‐dichloro‐6‐fluoro‐2‐pyridyl)oxyacetic acid (Dowco 433).

The test allows the simultaneous examination of herbicidal responses and related metabolic changes in the oat tissue. As the procedure uses small amounts of chemical, it is suitable for 14C tracer studies and other investigations for v/hich research chemicals are not freely available. The use of the test with other species and other herbicides is discussed, and possible applications for screening for crop safeners and investigations on crop tolerance are suggested.
Screening for resistance to potato cyst nematodes using bioluminescent photometry
Authors: STOREY R. M. J. , MARKS R. J.
Published: February 2008

The measurement of the adenosine triphosphate (ATP) content of cysts by bioluminescent photometry has been used as a screen for assessing the resistance of five potato clones to Globodera rostochiensis Rol and G. pallida Pa3. The multiplication rates (Pf/Pi) of the nematodes are based on the ratio of ATP levels for the cyst inoculum and their progeny. These have been compared to the corresponding ratios based on conventional visual counts of eggs and juveniles. The use of recoverable standard volumes of cysts to inoculate pots has allowed an assessment of the unhatched proportion (Cp) of juveniles from the parental cysts by both methods and an estimate of the corrected multiplication rate (P/P^l‐Cp)). This is an accurate assessment of resistance for a clone and the use of standard inocula and the ATP method will enable the criterion adopted for establishing resistance to be measured rapidly and precisely.
Bud‐eating by bullfinches, Pyrrhulapyrrhula in relation to the chemical constituents of two pear cultivars
Authors: GREIG‐SMITH PETER W. , WILSON MICHAEL F. , BLUNDEN CHRISTINE A. , WILSON GILLIAN M.
Published: February 2008

Damage to pear trees of the cultivars Conference and Doyenne du Cornice caused by Bullfinches feeding on the flower buds was measured during January‐April 1981. Bud‐eating was concentrated on trees near woodland, and occurred at a steady rate within each row, though progressively more rows were attacked. Levels of total soluble protein, free amino acids, starch, glyeeride‐glycerol, fructose, glucose and phosphorus were low until mid March, when the amounts per bud (and concentrations of starch and total soluble protein) rose sharply, coinciding with an increase in the size of buds. Sucrose did not occur at detectable levels. Conference buds contained significantly higher concentrations of fructose and free amino acids than Cornice. The implications for understanding bullfinches' bud‐feeding habits are discussed.
Alarm pheromone secretion by insecticide‐susceptible and ‐resistant Myzus persicae treated with demeton‐S‐methyl; aphid dispersal and transfer of plant viruses
Authors: RICE A. D. , GIBSON R. W. , STRIBLEY M. F.
Published: February 2008

The insecticides demeton‐S‐methyl and pirimicarb induced cornicle secretion, and thereby alarm pheromone release, in Myzus persicae. Secretion was earliest in young and insecticide‐susceptible aphids.

In laboratory experiments to assess the behavioural significance of this effect, demeton‐S‐methyl applied to colonies of R1 (moderately resistant) aphids killed the majority, but caused the remainder to disperse. The timing and degree of dispersal depended on the size and composition of the colonies. Beet yellows virus was transferred by dispersed aphids, but less frequently when recipient indicator seedlings were treated with demeton‐S‐methyl. R2 (strongly resistant) aphids soon dispersed from colonies containing susceptible nymphs (which secrete alarm pheromone early) and transmitted readily even to treated seedlings.

The non‐persistent potato virus Y was transferred by dispersed R: aphids and no protection was afforded by treatment of the seedlings.
Leafhopper transmission of Rhynchosia little leaf, a disease associated with mycoplasma‐like organisms in Jamaica
Authors: DABEK A. J.
Published: February 2008

Little leaf disease of Rhynchosia minima (RLL) in Jamaica is reported for the first time. The presence of phloem‐restricted MLO in diseased but not healthy plants, the remission of symptoms induced in RLL‐affected plants with soil drenches of tetracycline, but not penicillin, and the transmission of disease‐associated MLO to R. minima test plants, suggests that RLL has an MLO aetiology. RLL is vectored by the cicadellid leafhopper Ollarianus balli, for which R. minima represents the specific field host. Healthy colonies of O. balli produced from eggs oviposited on the RLL‐immune weed Asystasia gangetica suggest that RLL is not transovarially transmitted. O. balli acquired the RLL agent after access to infected plants for 5 days (shorter feeds were not tried), and there was a maximum latent period in the leafhopper of 21 days. Of the O. balli collected from heavily‐infected field stands of RLL, 35% transmitted the disease, while, of those reared on RLL in captivity for 14–16 days, 56% transmitted. Male and female O. balli transmitted equally efficiently, while nymphs were less frequent vectors. O. balli also infected Cajanus cajan, an important small scale subsistence crop in Jamaica, and Catharanthus roseus. It did not, however, transmit coconut lethal yellowing (CLY) disease to test palms after natural or deliberate acquisition‐feeding on RLL, acquisition‐feeding on CLY‐affected palms, or, after injection with CLY‐affected phloem exudate. There was thus no evidence that RLL is related to CLY or that O. balli can act as a vector of CLY.
A new plant virus from the high jungle of the Eastern Andes; Solanum apical leaf curling virus (SALCV)
Authors: HOOKER W. J. , SALAZAR L. F.
Published: February 2008

A previously undescribed plant virus, Solanum apical leaf curling virus (SALCV), was found in cultivated potato and indigenous wild solanaceous plants in an area of high jungle near San Ramon, Peru. Symptoms in potato consisting of red, purple or pink discoloration, curling, crinkling and dwarfing of apical leaves develop soon after infection. Symptoms from tuber‐borne infection may also include dwarfing and stunting, dormancy may be prolonged and sprouts may be filiform producing small plants with very thin stems. The virus is transmissible by grafting, but was not transmitted through seed, by aphids or leafhoppers tested, nor by mechanical inoculation of sap. Infected Datura tatula and D. stramonium, the most useful indicator hosts, developed yellowing of the small veins of newly formed leaves followed by distortion, dwarfing, and cupping of subsequently formed leaves. Tomato, Solanum nigrum, Nicandra physalodes and Nicotiana benthamiana were also infected experimentally. N. physalodes, Solanum basendopogon, D. tatula and Physalis peruviana were naturally infected in the field.

Antiserum produced in rabbits was suitable for ELISA which detected SALCV in a range of graft‐inoculated and naturally infected plants. Most virus particles in purified preparations and those trapped on antiserum sensitised grids treated with infective sap were c. 52 times 17 nm and consisted of three quasi‐isometric units in a straight chain. This particle morphology although novel, suggests possible affinities with geminiviruses.