bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for pre‐harvest assessment of latent infections in fruits
Authors: PRUSKY D. , FUCHS Y. , ZAUBERMAN G.
Published: February 2008

A method was developed for the assessment of latent infections of Alternaria alternata in mango fruits. Fruit discs were sampled and assayed for fungal contamination under suitable growth conditions. By this method it was possible to evaluate the percentage of infections and the relative surface infected by Alternaria in mango fruits before harvest. The percentage of infections increased during the growing season but fungicide treatments prevented this increase. A significant positive correlation was found between the relative surface infected by latent Alternaria at harvest time and the incidence of black spots that developed on the fruit during storage.
Duration of cereal aphid populations and the effects on wheat yield and breadmaking quality
Authors: LEE G. , STEVENS D. J. , STOKES SUZANNE , WRATTEN S. D.
Published: February 2008

Field‐caged and open‐plot populations of the aphid Sitobion avenae on winter wheat (cv. Maris Widgeon) were sampled approximately twice‐weekly in the summer of 1978. Cage populations began at growth stage 10.2 (Feekes scale) (Zadoks, G. S. 52); they were removed by spraying with pirimicarb at growth stages 10.54 (71), 11.1–11.2 (77) and 11.2–11.3 (85) respectively. All cage populations reduced mean weight per grain but the effect per aphid unit was lowest in the population of longest duration. Although the aphid index in the open plots was higher than that in the early cage treatment, yield was unaffected. Cage infestations affected the breadmaking quality of the grain: percentage flour extraction was reduced and there was an increase in colour, nicotinic acid content and thiamine (vitamin B1) content of the flour; percentage nitrogen in the flour was unaffected but there was a reduction in baking value and in the high molecular weight glutenin content; infestation also reduced α‐amylase activity. Different aspects of grain quality did not change in parallel with one another or with yield changes and thus damage thresholds will vary according to the yield/quality measure under consideration.
Effects of common scab (Streptomyces scabies) on potatoes
Authors: ADAMS M. J. , HIDE G. A.
Published: February 2008

Seed tubers with severe (71% cover) or slight (12% cover) common scab selected from a badly infected crop of cv. Maris Piper were boxed for sprouting in November and February and planted in field experiments at Woburn and Rothamsted in 1980.

The severely scabbed seed lost more moisture than the slightly scabbed seed during sprouting and sprouted from a larger number of eyes but total stem numbers were greater on plants from the slightly scabbed seed. Plant growth during the first 6–9 wk after planting was less from the severely scabbed than from the slightly scabbed seed. This was shown by records of ground cover, leaf area index, fresh weights of stems and leaves, total tuber yield (18% lower at 9 wk) and tuber number. Subsequently these differences became non‐significant. Seed with slight scab boxed in November produced smaller numbers of progeny tubers than that boxed in February but there were no other consistent effects of boxing date on growth and yield. Scab incidence on progeny tubers was very slight and unrelated to the severity of disease on the seed tubers.

It seems unlikely that severe scab infection of seed tubers would significantly decrease tuber yields except perhaps in early potato production.
Peanut green mosaic virus — a member of the potato virus Y group infecting groundnut (Arachis hypogaea) in India
Authors: SREENIVASULU P. , IIZUKA N. , RAJESHWARI R. , REDDY D. V. R. , NAYUDU M. V.
Published: February 2008

A virus, now named peanut green mosaic virus (PGMV), was isolated from groundnut (Arachis hypogaea) in India and identified as a member of the potato virus Y group by electron microscopy, aphid transmission, and its chemical properties. It was sap transmissible to 16 species of the Leguminosae, Solanaceae, Chenopodiaceae, Aizoaceae and Pedaliaceae; Phaseolus vulgaris was a good local lesion host. PGMV remained infective in buffered groundnut leaf sap at dilutions of 10‐3 after 3 to 4 days at 25 °C, or heating for 10 min to 55 °C but not 60 °C. PGMV was transmitted in the non‐persistent manner by Aphis gossypii and Myzus persicae but was not seed‐borne.

Purified virus preparations contained flexuous filamentous particles c. 750 nm long which sedimented as a single component with a sedimentation coefficient (S°20w) of 171S, and contained a single polypeptide (mol. wt 34 500 daltons) and one nucleic acid species (mol. wt 3.25 × 106 daltons). PGMV is serologically unrelated to peanut mottle virus (PMV) and other viruses infecting leguminous crops. Infected leaves contained cylindrical, cytoplasmic inclusions.
Garlic yellow streak virus, a potyvirus infecting garlic in New Zealand
Authors: MOHAMED N. A. , YOUNG B. R.
Published: February 2008

In New Zealand, all garlic (Allium sativum) plants tested were infected by a virus with flexuous filamentous particles 700–800 nm long. This virus, called garlic yellow streak virus (GYSV), infected only two of 12 species tested and was transmitted to garlic by the aphid Myzus persicae in a non‐persistent manner. In garlic sap, GYSV was infective at a dilution of 10‐4 but not 10‐3, after heating for 10 min at 60°C but not 65°C, and after 2 days but not 3 days at 25°C.

The yield of virus, purified from naturally infected garlic, was 3–4 mg/kg fresh leaf. Preparations had A260/A280= 1.28 and Aman/Amin= 1.08. The virus particles had a sedimentation coefficient of 149S and a buoyant density in CsCl of 1.334 g/cm3. Mol. wt estimates for the virus nucleic acid were 2.95 × 106 by electrophoresis in polyacrylamide gels and 3.46 × 106 from the sedimentation coefficient (41.4S) in linear‐log sucrose density gradients. Two polypeptides were detected in virus preparations; one (mol. wt 30 500) was possibly a breakdown product of the other (mol. wt 33 000). GYSV was serologically distantly related to onion yellow dwarf and leek yellow stripe viruses but was considered to be a separate virus because it differed from them in host range.
Further properties of peanut clump virus and studies on its natural transmission
Authors: THOUVENEL J. C. , FAUQUET C.
Published: February 2008

Purified preparations of particles of peanut clump virus (PCV) had A260/A280 values (corrected for light scattering) of 1.00. They contained rod‐shaped particles with sedimentation coefficients of 183 S and 224 S, and a density in CsCl of 1.32 g/ml. PCV infected 36 species in 8 plant families. No serological relationship was detected between PCV and barley stripe mosaic, beet necrotic yellow vein, Nicotiana velutina mosaic and tobacco mosaic viruses.

PCV was seed‐borne for two generations in groundnut (Arachis hypogaea) but was not seed‐borne in great millet (Sorghum arundinaceum), Phaseolus mungo or Nicotiana benthamiana.

Seedlings of groundnut, great millet and wheat (Triticum aestivum) became infected when grown in soil from groundnut fields with outbreaks of clump disease, and the infectivity of soil survived air‐drying at 25°C for 3 months. Groundnut seedlings became infected when grown in sterilised soil contaminated with washed roots of naturally‐infected S. arundinaceum but not in soil to which roots of naturally infected groundnut or shoots of infected groundnut were added, or in which mechanically inoculated groundnut seedlings were grown at the same time. The patchy distribution of PCV in a crop was related to the infectivity of the soil for groundnut and to the presence of Polymyxa graminis resting spores which could be detected in the roots of S. arundinaceum bait seedlings, but not in those of groundnut.

The results indicate that PCV is transmitted by a vector that is resistant to air‐drying and closely associated with S. arundinaceum roots. For these reasons P. graminis is thought to be the vector of PCV.
A dispenser for the rapid delivery of standard inocula of the cyst nematode Globodera rostochiensis
Authors: MARKS R. J. , McKENNA L. A.
Published: February 2008

A simple machined dispenser is described, capable of providing rapid repetitive delivery of standard volumes of potato cyst nematode cysts. Standard volumes of cysts of mixed sizes, drawn from unsieved populations of G. rostochiensis, contain titres of infective eggs and larvae which are largely independent of cyst numbers; the method reduces inoculum variability compared with other cyst inoculation techniques. Standard volumes of cysts of mixed sizes may be used directly as the inoculum for plant resistance testing programmes without the operator error associated with hand‐held scoops or the need for the subjective and time consuming selection of groups of individual cysts.
Observations on the trapping of the whitefly Bemisia tabaci by glandular hairs on tomato leaves
Authors: KISHA JENNIFER S. A.
Published: February 2008

Observations were made on the role of glandular leaf hairs of four tomato cultivars in trapping cotton whitefly, Bemisia tabaci, adults. Dead, trapped whitefly occurred in similar numbers on both the upper and lower surfaces of leaves even though glandular hairs were denser on the former. Females constituted 58% of untrapped but 86% of trapped adults, many becoming trapped during oviposition which occurred mainly on the lower surfaces. Of the four cultivars studied, Strain B trapped more whitefly than Ace, Marglobe or Moneymaker.
Aspects of the biology of the black cowpea moth, Cydiaptychora (Lepidoptera: Tortricidae) related to host plant phenology
Authors: OLAIFA J. I. , AKINGBOHUNGBE A. E.
Published: February 2008

Females of Cydia ptychora oviposited on cowpea, Vigna unguiculata ssp. unguiculata in the field between 18.00 and 19.00 h commencing about 30 days after planting with a few eggs laid on the leafbuds and the undersides of leaves. Oviposition increased as the host plant developed the preferred sites, floral sepals and their remains on pods, and peaked at about 58 days after planting regardless of planting date. First instar larvae were found wandering on the plant between 06.45 and 11.15 h but other larval instars were rarely encountered outside the pod except when changing pods or leaving pods to pupate in the soil. Contrary to previously reported observations, larval development occurred in leafbuds and inside flowers both in the field and in laboratory rearing. Development was optimal on pods, and mortality was high in leafbuds.
The effect of chlormequat chloride formulated with choline chloride on the height and yield of winter wheat
Authors: MATHEWS P. R. , CALDICOTT J. J. B.
Published: February 2008

Twenty‐one field trials were conducted on commercial crops of winter wheat from 1976 through to 1978, with a mixture of 460 g chlormequat chloride and 320 g choline/litre at rates ranging from 0.67 kg to 2.07 kg of chlormequat chloride/hectare.

The mean increase in grain yield in the absence of lodging following treatment with chlormequat chloride was 0.31 t/ha, with a greater yield increase where lodging occurred on untreated controls. Chlormequat chloride when applied in mixture with carbendazim fungicide usually resulted in yield increases which were less than the sum of the increases from the two products applied separately. Yield increases following the use of chlormequat chloride were usually greater when used in a traditional system of wheat growing than when used in the Laloux system.

Effects of chlormequat chloride on crop height were poorly determined in the dry season of 1976 but there were consistent reductions up to 1.15 kg a.i./ha in 1977. Crop height was reduced by 1.61 kg of chlormequat chloride/ha in 1978.
Use of a nematode, Heterorhabditis heliothidis, to control black vine weevil, Otiorhynchus sulcatus, in potted plants
Authors: BEDDING R. A. , MILLER L. A.
Published: February 2008

Application of aqueous suspensions of infective juvenile Heterorhabditis heliothidis, isolate T327, to the soil resulted in up to 100% parasitisation of larvae of the black vine weevil, Otiorhynchus sulcatus, in potted yew, raspberries and grapes in nurseries, and over 87% parasitisation on potted cyclamens and strawberries. Pupae and newly emerged adults on grapevines were also parasitised. Another isolate, T310, produced 92.5 to 98.5% parasitism of O. sulcatus larvae on potted cyclamens in glasshouse, but was less effective on strawberries. Neoaplectana bibionis was found to be less effective than H. heliothidis T327 strain.

The use of these nematodes provides an economical and effective method for controlling O. sulcatus on potted plants in glasshouses and nurseries.
A method for mass rearing the aphid predatorAnthocoris nemorum
Authors: PARKER N. J. B.
Published: February 2008

Anthocoris nemorumis currently under investigation as a potential agent for the control of damson‐hop aphidPhorodon humulion hops. Detailed here is a method of rearingA. nemorumto provide a large number of insects with a predetermined age structure for mass release in the field. It is designed to minimise culture maintenance, with components and materials which are readily obtained as, or can be modified from, stock items. Initial cultures are collected from the field, as adults, in early autumn and artificially overwintered. These are recovered in early spring, with females being placed in oviposition chambers, and the harvesting of ova regulated to provide synchronisation of eclosion within batches. Larvae are reared until they reach the desired instar for mass release and then held in controlled cold storage until required.
Fertility of the polyembryonic parasite Copidosoma koehleri, effect of humidities on life length and relative abundance as compared with that of Apanteles subandinus in potato tuber moth
Authors: KFIR KAMI
Published: February 2008

Males and females of Copidosoma koehleri were kept separately in desiccators producing relative humidities of 20, 40 and 70% at 24 and 28°C and found to be very susceptible to low relative humidity. They lived less than 1 day at 20%, about 2 and 4 days at 40% and about six times longer than these respectively at 70% r.h. When kept at 26°C and 70% r.h. females of C. koehleri parasitised 98.8 hosts. The number of parasites that emerged from a male brood was 21.2 and from a female brood 33.2. Mated females produced 3026 progeny and unmated 2289. The sex ratio of broods produced by mated females was 1:1 and the female percentage among progeny was 59. It is known that C. koehleri is rare at the beginning of the potato‐growing season and becomes the predominant parasite later on. It is known also that in potato crops when the plants are small at the beginning of the season the air within the crop is less humid but as the canopy of foliage develops, relative humidity rises and becomes higher than at 1.2 m above ground. It is suggested that relative humidity in the potato crop is the major factor affecting the relative abundance of C. koehleri and Apanteles subandinus in South Africa.
The effect of insecticides on Bemisia tabaci, tomato leaf curl virus disease incidence and yield of tomatoes in the Sudan
Authors: KISHA JENNIFER S. A.
Published: February 2008

The whitefly Bemisia tabaci infested winter‐sown tomatoes immediately after germination. Soil‐applied granular insecticides and foliar sprays of a synthetic pyrethroid reduced the number of nymphs and adults, but insecticides failed to reduce the incidence of tomato leaf curl virus disease which is transmitted by this insect. Results from pot experiments using aldicarb granules to tomato and to cotton plants indicated that the time and rate of application influence whitefly mortality and reproduction.
Relationship between powdery mildew infection, green leaf area and grain yield of barley
Authors: CARVER T. L. W. , GRIFFITHS ELLIS
Published: February 2008

Barley plants (cv. Julia), grown in a greenhouse in large boxes of John Innes compost at a spacing equivalent to 300 plants/m2, were exposed to powdery mildew from growth stage (G.S.) 2 (Feekes scale) until maturity. Treatment with ethirimol was used to provide five different epidemic patterns, viz. (i) no mildew, (ii) early mildew, (iii) late mildew, (iv) continuous mildew and (v) continuous mildew but delayed by seed dressing.

None of the treatments affected the number of spikelet primordia differentiated on primary shoots, nor were the numbers and sizes of leaves affected.

From graphs of mildew and green leaf area (GLA), plotted from G.S. 2 to G.S. 10.5, areas under the curves were determined. There was a strong negative correlation (r= ‐0.926) between areas under the mildew and GLA curves and it was also clear that reduction in GLA lagged behind disease. Grain yield was strongly correlated with total area under the GLA curve (r= 0.994 for primary shoots and 0.986 for tillers). For values of GLA at specific growth stages the best correlations were found at G.S. 9 (r= 0.967 for primary shoots and 0.992 for tillers). The correlation between total yield of primary shoots and area under the mildew curve was also high (r= 0.953) but for mildew estimates at specific times only those at G.S. 7 were significant (r= 0.980); at G.S. 10.5 there was no significant correlation.

It may be postulated from the data that retranslocation of stored photosynthate, produced before anthesis, plays an important role in grain filling and that mildew post anthesis may have little effect on yield. The implications of the results are discussed in relation to methods of loss appraisal and strategies for mildew control.
Field resistance in cowpea, Vigna unguiculata to the cowpea moth, Cydia ptychora
Authors: EZUEH M. I. , TAYLOR T. AJIBOLA
Published: February 2008

Field evaluation of 26 selected cowpea cultivars showed that several of them had good levels of resistance to Cydia ptychora; TVu 946, Adzuki, ‘Vita 5’ and Igbirra were the most resistant. Percentage seed damaged by the larvae was positively correlated with days to 50% flowering (r= 0.39*), days to 50% pod ripening (r= 0.48*) and weight of 100 seeds (r= 0.56**). All four cultivars were early maturing, had semi‐determinate or determinate plant types and carried their pods above the leaf canopy.

No single morphological character could be related to the degree of seed damage but some association with phenological characteristics was indicated. Earliness, determinacy and uniform pod maturity were important plant characters associated with the expression of field resistance. Even if these characters are not causative, they provide a rational basis for screening of a large germplasm to identify or synthesise materials with greater resistance to this moth.
The biological bases of resistance in cowpea to the cowpea moth, Cydia ptychora (Lepidoptera: Olethreutidae)
Authors: EZUEH M. I.
Published: February 2008

Intensive greenhouse screening using potted plants demonstrated a high level of resistance in the wild cowpea, Vigna unguiculata (ssp. mensensis), to the cowpea moth, Cydia ptychora. Two closely related cvs (TVu 946 and TVu 2994) also showed some resistance. Further investigations in the laboratory and in the greenhouse indicated that resistance was due mainly to oviposition preference and to antibiosis. Pods of the wild cowpea, and those of cvs TVu 946 and TVu 2994, were not attractive to egg‐laying females whereas no oviposition preference was seen among the genetically improved cultivars. Pronounced antibiosis was detected in the wild cowpea, and to a lesser extent in the closely related cvs, when pods were infested with first‐instar larvae. Fecundity of females was also significantly reduced. These effects were thought to be partly due to nutritional deficiencies in the resistant cvs but there may also be an antibiotic factor in the wild cowpea progenitor. Apparently, pod‐wall thickness was not related to resistance although differences in successful penetration of pods by larvae were observed.
A rapid method to estimate the resistance of cold stored carrot roots to Botrytis cinerea
Authors: HARDING V. K. , HEALE J. B.
Published: February 2008

Inoculating whole carrot roots at 4°C with mycelial/agar discs of the grey mould fungus Botrytis cinerea gives a measure of their resistance and hence storage potential to this pathogen, but results are not obtained for at least 33 days. In the present investigation a more rapid method was used which involved inoculating root slices with spore suspensions containing 5 × 103–5 × 106 spores/cm3 at 24°C. Resistance was assessed visually and by a chitin estimation 48 h after inoculation.

Both methods were used to measure the resistance of cold stored carrot roots during two storage seasons, 1976/77 and 1977/78. In each season there was a particular inoculum level which most clearly recorded the increasing susceptibility of roots with time in store. In 1976/77 this was 1 × 105 spores/cm3 whereas in 1977/78 it was the lower inoculum concentration of 5 × 104 spores/cm3, suggesting the roots were generally more susceptible in 1977/78 than the previous season. This was in accord with the results from the whole root method of assessment. A chitin estimation proved to be the more sensitive method of assessment for inoculum potential experiments.
The effect of seed and stem base spray treatment with iprodione on white rot disease (Sclerotium cepivorum) in autumn‐sown salad onions
Authors: ENTWISTLE A. R. , MUNASINGHE H. L.
Published: February 2008

Iprodione applied to seed at 250 g a.i./kg controlled white rot in autumn‐sown salad onions until July the following year, and reduced losses during the winter caused by Botrytis spp. At 25–150 g a.i./kg seed, iprodione controlled autumn and spring infections but it was less effective later in the summer.

Treatment of autumn‐sown onions at 50 g a.i./kg seed followed in March by a single stem base spray at 0.031 g a.i./m row (total rate c. 2.4 kg a.i./ha) gave complete control; seed treatment at 25 g a.i./kg followed by a stem base spray at 0.125 g a.i./m row (c. 4.5 kg a.i./ha) was equally effective.

Four stem base sprays of iprodione at 0.075 g a.i./m row/spray (9 kg a.i./ha) applied in spring to plants raised from untreated seed, controlled spring and summer infections but yields were low because of losses caused by infection in the previous autumn. A single stem base spray of iprodione at 0.125 g a.i./m row applied in spring to plants raised from thiophanate‐methyl treated seed at 125 g a.i./kg gave complete control and high yields.
Purification and some properties of Tephrosia symptomless virus
Authors: BOCK K. R. , GUTHRIE E. J. , FIGUEIREDO GINA , WOODS R. D.
Published: February 2008

Tephrosia symptomless virus (TSV), isolated from Tephrosia villosa, is widely distributed in coastal districts of Kenya. The virus was readily transmitted by inoculation of sap, but not by Aphis craccivora or Apion sp. (Curculionidae) or through soil. Host range was very restricted and it infected only 10 of 70 species tested in one of nine plant families; susceptible species were confined to five genera within the Papilionaceae. The virus was cultured, propagated and assayed in soybean.

TSV remained infective after 10 min at 85°C, 3 wk at 20°C and 26 wk at ‐12°C; crude infective sap of Glycine max retained infectivity when diluted 10‐6 but not 10‐7.

Virus was purified from systemically infected soybean by clarifying sap extracted in 0.06 m phosphate buffer containing 0.001 m EDTA and 0.1% thioglycollic acid (pH 7.5) with equal volumes of 1:1 n‐butanol/chloroform followed by two cycles of differential and one of sucrose density gradient centrifugation. Purified preparations contained c. 33 nm isometric particles. TSV contained RNA and one protein of molecular weight 1.53. 106 and c. 42 000, respectively. Analytical centrifugation indicated a single component with a sedimentation coefficient (s.20, w) of 127 S; in Cs2SO4 and CsCl isopycnic gradients a single virus band formed; buoyant density in CsCl was 1.361.

TSV was not related serologically to any of 44 viruses in nine plant virus groups but it resembled the tombusviruses and other ungrouped viruses such as carnation mottle in some of its properties.
The effect of oxamyl on the growth of peas attacked by pea cyst nematode
Authors: GREEN C. D. , WILLIAMSON KATHERINE , DENNIS E. B. , McBURNEY T.
Published: February 2008

Oxamyl treatment at drilling greatly increased the growth of the plants, the yield and quality of the peas harvested, in soil infested by small or large numbers of Heterodera goettingiana. Treated plants were continuing to set pods when non‐treated plants were senescing. Rhizobium nodulation, sap nitrate and tissue nitrogen content were increased in treated plants. Oxamyl applied to growing plants reduced later nematode invasion and enabled root nodulation to proceed with an increase in tissue nitrogen but no increase in yield. Oxamyl applied at drilling in April was inactive against invasion by H. goettingiana in June, which enabled the nematode to multiply equally in treated and non‐treated plots. The most economic treatments were at the smallest rates, giving the greatest increase in yield/kg of oxamyl applied.
Seed survival and periodicity of seedling emergence in twelve weedy species of Compositae
Authors: ROBERTS H. A. , NEILSON JUNE E.
Published: February 2008

Achenes of 12 species of Compositae were collected in each of 3 years and mixed with the top 7.5 cm of sterilised soil which was confined in cylinders sunk in the ground outdoors and cultivated three times yearly. Seedling emergence was recorded for 5 yr and the numbers of viable seeds remaining then determined. Emergence of Arctium lappa, A. minus, Picris hieracioides, Taraxacum officinale, Sonchus arvensis and S. asper was mainly in spring. Seedlings of Chrysanthemum segetum, Lapsana communis, Anthemis cotula and Sonchus oleraceus were often most numerous in spring but also emerged at other times, while Matricaria matricarioides and M. recutita showed no consistent seasonal pattern of emergence. Except for C. segetum and A. cotula, in which there was evidence of innate dormancy imposed by the seed coat, the numbers of seedlings were greatest in the first year and thereafter decreased approximately exponentially from year to year. Few viable seeds of A. lappa or A. minus remained after 5 yr and those of T. officinale, P. hieracioides and S. arvensis accounted for less than 1.5% of the seeds sown. Seed survival was greatest in the annual weeds and ranged from 2.1% (S. asper) to 8.6% (M. matricarioides) after 5 yr.
Wound‐healing in carrot roots in relation to infection by Mycocentrospora acerina
Authors: LEWIS B. G. , DAVIES W. P. , GARROD B.
Published: February 2008

A period at 25 °C or 15 °C in a humidity approaching saturation before storage at 2 °C accelerated wound repair, diminishing subsequent infection by Mycocentrospora acerina in proportion to the period of treatment up to 48 h. The total number of localised lesions was reduced as well as the proportion which subsequently became progressive. Healing involved the accumulation of antifungal substances on the wound surface; patches of oily conglomerates were fungicidal and the remainder of the surface was strongly fungistatic. Only a small proportion of the chlamydospores germinated after wounds had been healed for 48 h.
Components of resistance to Cercospora arachidicola and Cercosporidium personatum in groundnuts*
Authors: NEVILL D. J.
Published: February 2008

The reactions of four groundnut cultivars to inoculation with two leaf spot pathogens (Cercospora arachidicola and Cercospodirium personatum) were investigated. Resistant cultivars showed longer latent periods, reduced sporulation and less defoliation; however, none of the cultivars was resistant to both pathogens. Numbers of lesions, time to leaflet loss and the percentage of spores which produced lesions were influenced by the concentration of C. personatum inoculum applied to the leaves and there were significant cultivar differences in lesion numbers at the lowest inoculum level. Only the first two characters were affected by applied spore concentration in the study with C. arachidicola. Generally it was found that lower inoculum levels gave a better separation of cultivars.

The level of resistance was similar to that found in the slow resting reaction of cereal crops and should be useful in a groundnut breeding programme.
Resistance and susceptibility to colour forms of the aphid Sitobion avenue in spring and winter wheats (Triticum aestivum)
Authors: LOWE H. J. B.
Published: February 2008

Glasshouse assessments of resistance to S. avenae in 29 entries of wheat and two of rye were made by releasing half‐grown aphids on randomised plants at the stem extension phase of growth. Wheat cvs Kador, Amigo, Highbury and Lutescens 1377 were resistant and cvs Sentry and Talavera de Bellevue partially resistant. Cv. Klein Acero, a breeding line TB68/6/10 and Lerma Rojo selections 197 to 200 were highly susceptible to S. avenae although the latter are moderately resistant to greenbug (Schizaphis graminum) (Starks & Merkle, 1977). The rye cultivars were susceptible to 5. avenae and no cultivar was found to be resistant to Metopolophium dirhodum.

Clonal stocks of S. avenae, differing in colour, varied in their ability to form large populations on susceptible cultivars, and hence in their differentiation of susceptible from resistant wheat. No clone was detected with specific ability to attack the resistant cvs Kador and Amigo.
The susceptibility of Myzus persicae and Brevicoryne brassicae to 14C‐phorate in artificial diets
Authors: GALLEY BY D. J. , GOHAIN RUMA
Published: February 2008

Colonies of Myzus persicae and Brevicoryne brassicae were established on artificial diets and the honeydew produced by them collected on aluminium foils. The diets were later exchanged for others containing a range of 14C‐phorate concentrations. The honey‐dew produced while feeding on the treated diets was collected separately and mortalities were recorded. The diets, aphids and their honeydew were subsequently analysed.

About 1.6% of the doses applied initially were found in the diets at the end of the bio‐assay period. Thin‐layer chromatography of diets containing LC50 concentrations of insecticides showed that phorate and its metabolites were present in similar proportions. The LC50 values were 15.5 nM and 277 nM phorate equivalents for B. brassicae and M. persicae respectively.
Field evaluation of 4‐n‐butyl‐1,2,4‐triazole for the control of leaf rust of triticale*
Authors: THAPLIYAL P. N. , SINHA A. P.
Published: February 2008

Severe epidemics of triticale leaf rust were controlled by a single treatment with 4‐n‐butyl‐1,2,4‐triazole (triazbutyl) as a foliar spray or as broadcast application on soil followed by irrigation. A single foliar spray of triazbutyl at 0.5 litre a.i./ha approached the control obtained by 1.0 litre a.i./ha. Effective control was obtained by spraying 10 days before or 10 days after the rust appearance but later spray applications were less effective.
Tests for transmission of cherry leaf roll virus using Longidorus, Paralongidorus and Xiphinema nematodes
Authors: JONES A. T. , McELROY F. D. , BROWN D. J. F.
Published: February 2008

The ability of 10 nematode species to transmit three strains of cherry leaf roll virus (CLRV) was tested by three methods: (1) virus‐infected source plants and virus‐free bait plants were grown concurrently in nematode‐infested soil, (2) as for (1) but virus source plants were removed before bait plants were planted, and (3) nematodes were extracted from soil after access to virus source plants, and were added to pots containing bait plants. The occurrence of galls on roots showed that nematodes fed both on source and on bait plants in all experiments and, in some experiments, CLRV was detected by direct assays (slash tests) of Longidorus elongatus, L. leptocephalus and Paralongidorus maximus. Although the nematodes readily transmitted control viruses, for which they are known to be vectors, CLRV was detected by root assays in only a few bait plants exposed to L. elongatus, L. macrosoma, Xiphinema diversicaudatum or L. leptocephalus + X. vuittenezi in tests by method 1. The recovery of CLRV in these tests is interpreted as being due to contamination.

These results add to the increasing circumstantial evidence against the involvement of nematodes in the transmission of CLRV. Other possible mechanisms of spread are discussed.
Effects of some systemic imidazole and triazole fungicides on white clover and symbiotic nitrogen fixation by Rhizobium trifolii
Authors: FISHER D. J. , HAYES ANN L.
Published: February 2008

Effects of prochloraz, imazalil, diclobutrazol, triadimefon and propiconazole were studied. Compared with most systemic fungicides previously tested they were all relatively toxic to R. trifolii on agar. Effects of soil residues of the compounds on the growth and nitrogen fixing capacity of white clover were measured. The lowest concentration of the fungicides used was that which would be present if all the active ingredient from a single application remained unchanged and evenly distributed in the top 5 cm of soil. This concentration of diclobutrazol decreased the size and weight of 11‐wk‐old clover plants. The rate of nitrogen fixation was reduced by twice this concentration and root nodulation by four times this amount. None of the other fungicides had any significant effect.

The possibility of field application of diclobutrazol to cereals causing damage to clover crops is discussed. It is questionable whether harmful soil residues will ever accumulate from normal usage of the fungicide but exceeding the recommended rate of application, or application to cereals undersown with clover, might cause undesirable effects on the clover.
A small‐scale screening technique for evaluating fungicides against Phytophthora palmivora pod rot of cocoa
Authors: McGREGOR A. J.
Published: February 2008

Plots of clonal Trinitario cocoa were sprayed with fungicides in the field. Ripe pods were harvested from the trial plots and artificially inoculated with Phytophthora palmivora using various techniques, the most suitable of which proved to be the zoospore spot method. Percentage infection results from the spot inoculation tests agreed well with the field percentage infection results and it was concluded that field spraying followed by zoospore spot inoculation of detached pods is a suitable preliminary screening technique for fungicides. Three systemic fungicides metalaxyl, aluminium tris (ethyl phosphonate) and DPX‐3217 in a mixture with captafol and copper oxychloride were compared with the protectant cuprous oxide. Metalaxyl was found to be the most effective of the systemic fungicides and when applied at the rate of 0·44 g ai/ha every 8 wk it gave a similar reduction in percentage infection to 4 weekly applications of cuprous oxide at the rate of 4·4 kg Cu++/ha during the wetter part of the year when pod rot is most severe.
Compensation in grain yield components in a panicle of rainfed sorghum
Authors: HAMILTON R. I. , SUBRAMANIAN BALA , REDDY M. NARAYANA , RAO C. HANUMANTHA
Published: February 2008

In a field experiment with rainfed grown sorghum hybrid CSH‐6, various proportions of spikelets from the apex, base or random regions of the panicles were removed at the time of anthesis and the yield compensation in grain number and grain size within a panicle was investigated. The distribution of grain number and grain yield in a control panicle from apex to base was parabolic while grain size showed a progressive linear decrease. Full grain yield compensation occurred due to an increase in grain number and size when the panicles lost up to 20% of their portions at the base or at random. No grain number compensation was, however, recorded at the apical region. Irrespective of the number of spikelets retained, the size of grains in the upper part of the panicle was always larger than those in the lower part.

The grain number compensation, which occurred when spikelets were removed at the time of anthesis and the decreasing grain size from apex to base of the panicle would suggest hormonal involvement in the determination of potential grain number and size.
Secondary host preferences and reproductive activity of the bird cherry‐oat aphid, Rhopalosiphum padi
Authors: LEATHER S. R. , DIXON A. F. G.
Published: February 2008

Of 15 species of grass, including cereals, alate exules and emigrants of Rhopalosiphum padi preferred to colonise Lolium perenne. Emigrants colonised cereals twice as readily as alate exules. Apterous exules also preferred L. perenne to cereals. Although small when reared on L. perenne, R. padi was more fecund per unit weight than on any of the other grasses tested. On the later growth stages of Dactylis glomerata and L. perenne, R. padi developed faster and were more fecund than on Phleum pratense at the same growth stages. At low temperatures R. padi were more fecund on P. pratense than on L. perenne and D. glomerata and vice versa at high temperatures. The secondary host preferences and reproductive activity of R. padi are discussed in relation to possible suitable hosts for viviparous overwintering and the pest status of this aphid in Britain.
Some effects of insecticide deposit patterns on the parasitism of Trialeurodes vaporariorum by Encarsia formosa
Authors: PERERA P. A. C. R.
Published: February 2008

The functional response of Encarsia formosa parasitising Trialeurodes vaporariorum on Phaseolus vulgaris was a typical type II functional response (Holling, 1959) where, with increasing host density, the numbers of hosts parasitised by a single parasitoid show a negatively accelerating rise to an upper plateau. A mean maximum parasitism of 6.6 per female per 24 h reached at host densities near 80 larvae per leaf was observed. When presented with insecticide (‘Pynosect 30 ULV’) deposits, the parasite's search pattern changed, conforming to a typical Sigmoid functional response curve. With a uniform cover spray deposit of 27.6 × 10‐7 ml/cm2 searching began only at host densities of c. 80 larvae per leaf and the mean maximum parasitism was only 1.5 per female per 24 h. When the insecticide deposit of 27.6 × 10‐7 ml/cm2 was in the form of discrete groups of 100 μm droplets, searching began at host densities of c. 40 larvae per leaf but the mean maximum parasitism was low at 2.2. However by using the same discrete deposit pattern but reducing the deposit level to 2.65 × 10‐7 ml/cm2 it was possible to obtain the same high mean maximum parasitism as with the untreated control.
Effect of nitrogen nutrition on Fusarium wilt of tomato plants
Authors: SARHAN A. R. T. , BARNA B. , KIRÁLY Z.
Published: February 2008

The role of nitrate‐nitrogen (NO3‐N) in relation to the development of tomato wilt caused by Fusarium oxysporum f. sp. lycopersici R1 was studied. Plants receiving 284 μg/ml nitrogen in the nutrient solution exhibited the same severe wilt symptoms as the control plants in soil. Disease decreased with increasing nitrogen levels (420, 630 and 1050 μg/ml). Apparently, the plants were also less susceptible to the disease when the concentration of nitrogen was 70 μg/ml, i. e. below the optimal level (284 μg/ml).

Protein content in tissues of plants grown with different amounts of nitrogen was also determined. High nitrogen levels, which decreased disease severity, increased the protein content in leaf tissues. Of 17 amino acids only proline content increased with increasing nitrogen supply. High doses of NO3–N decreased the phenol content and the activity of peroxidase in stem and leaf tissues of tomato plants. It is suggested that phenolic compounds and the activity of peroxidase are not significant in the resistance of tomato to Fusarlum wilt associated with high nitrogen supply.
An assessment of a method based on intrinsic antibiotic resistance for identifying Rhizobium strains
Authors: STEIN MICHÈLE , BROMFIELD E. S. P. , DYE M.
Published: February 2008

A method based on intrinsic antibiotic resistance (IAR) for identifying large numbers of Rhizobium strains was assessed and found to be unsatisfactory for R. phaseoli and isolates from Cicer arietinum (Rhizobium spp.). Our data showed that the number of different IAR patterns always exceeded the number of strains tested. With 90 nodule isolates from plants inoculated with a mixture of three strains of R. Phaseoli, the technique gave 18 different resistance patterns. When 24 strains of Rhizobium spp., each replicated three times, were examined 68 different resistance patterns were obtained. Single colony isolates from one strain also gave several different IAR patterns. All strains tested with fluorescent“ antibody were readily identified. Attempts to obtain correct strain identification with IAR by simplifying the scoring systems or allowing up to two differences in the resistance patterns were unsuccessful. We were unable to define the source of this variation although incubation time and inoculum concentration were shown to affect the IAR patterns
Regeneration of virus‐free grapevines using in vitro apical culture
Authors: BARLASS M. , SKENE K. G. M. , WOODHAM R. C. , KRAKE L. R.
Published: February 2008

Fragmented shoot apex culture of grapevine has been demonstrated to regenerate plants free from the graft‐transmissible diseases leafroll, yellow speckle, fleck and summer mottle. This technique in combination with heat therapy of the cultures has also produced vines free from fanleaf virus. Regenerated plants free of yellow speckle were consistently obtained if cultures were incubated at 27/20 °C but not if incubated at 35 °C. The possible ways that the in vitro elimination of these diseases was achieved are considered.
The effect of glyphosate on frond regeneration, bud development and survival, and storage rhizome starch content in bracken
Authors: AL‐JAFF D. M. A. , COOK G. T. , STEPHEN N. H. , ATCHISON T. C. , DUNCAN H. J.
Published: February 2008

In addition to very effectively suppressing bracken frond regeneration for two years at levels of 2.24 kg a. i./ha and above, glyphosate had considerable effects on the rhizome system. Dry weight of frond‐bearing rhizomes, number of living apices and developed buds, number and viability of dormant buds and starch content of storage rhizomes were all markedly reduced. The effects on dormant buds and starch content are particularly important when considering frond regeneration and as a consequence of these, glyphosate is likely to give long lasting control of bracken. Low levels of glyphosate (0.02 and 0.07 kg a. i./ha) did not stimulate bracken growth, while the addition of NH4SCN apparently inhibited the action of the sub‐lethal rate of 0.56 kg a. i./ha.
Specificity and mode of action of BTS 44584 and chlormequat chloride on wheat and soybeans
Authors: SMITH AILEEN R. , THOMAS T. H. , GARROD J. F.
Published: February 2008

The distribution and persistence of the two growth retardants chlormequat chloride and BTS 44584 were studied in wheat and soybean using radioactively labelled tracers. The chemicals were applied as seed soaks and as foliar treatments to selected leaves and root treatments. Although there were some differences in the distribution of 14C‐BTS 44584 and 14C‐chlormequat chloride, these could not be directly correlated with either the growth effects observed or the species specificity displayed by the two compounds in previous studies. Differences in the amounts of degradation of the compounds appeared to be due to differences in species, plant age and mode of application rather than any relationship between degradation and species specificity.
Distribution and abundance of adult Opomyza florum (Diptera: Opomyzidae) in cereal crops and grassland
Authors: VICKERMAN G. P.
Published: February 2008

From 1971 to 1979 counts were made of the numbers of Opomyza florum adults found in vacuum net samples taken from cereal and grass fields on a 62‐km2 study area in West Sussex. In 2 years, 1974 and 1975, counts were made of the numbers of adults found in similar samples taken from hedgerow grasses. In all years, numbers of adults were highest in winter wheat crops; relatively few were found in other autumn‐ or spring‐sown cereals or in grass fields. Mean numbers (/m2) in winter wheat in June varied from 33.0 in 1974 to only 0.9 in 1977. In most years, the first adults were found in June in winter wheat; numbers reached a peak in July and then declined rapidly. More adults were usually found in winter wheat crops that followed winter wheat in the rotation than in those following grass. Adults were also more abundant in June in winter wheat crops sown relatively early than in those sown late. The current tendencies towards earlier drilling of winter wheat and to the growth of successive wheat crops could increase the pest status of O. florum.
The influence of potato harvesting and grading machinery on contact spread of Phoma exigua var. foveata on tubers
Authors: COPELAND R. B.
Published: February 2008

The incidence of wounds infected by Phoma exigua var. foveata was increased if freshly damaged tubers (recipients) were shaken in a bag with diseased tubers (donors) to simulate the tuber‐to‐tuber contact that occurs during potato handling. An increase in the number of gangrene rots on damage points also occurred if the recipient tubers were wounded after contact with the diseased tubers, rather than before, and when the donor tubers were heavily infested with P. exigua var. foveata but were free of gangrene lesions. Increasing the proportion of donor to recipient tubers increased the percentage of infected wounds on recipients.

Increased incidences of infection in recipient tubers also occurred after they had been passed over an elevator digger when it was lifting stocks of tubers heavily infested with P. exigua var. foveata. When spores of an E +ve isolate of P. exigua var. foveata were sprayed onto the webs of manned potato harvesters, tubers harvested immediately after developed gangrene rots from many of which the E +ve isolate was cultured. An E +ve isolate was also used to demonstrate the transfer of P. exigua var. foveata inoculum from tubers onto soil on riddles of a potato grader and from these soil‐coated surfaces onto other tubers during grading.