bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic manuring for potato scab control and its relation to soil manganese
Authors: ROGERS P. F.
Published: February 2008

The suggestion that organic amendment of soil controls scab by reducing insoluble soil manganese to soluble forms toxic to Streptomyces scabies was investigated in pot and field experiments by assessing numbers of manganese‐reducing micro‐organisms in soil.

Dried grass meal (2 tons/acre) gave significant control of scab but increases in soluble manganese were insufficient to account for this control. Populations of micro‐organisms in soil increased after adding grass meal but decreased again by the time tubers were initiated and scab infection began. The results suggest that manganese reduction could affect scab if soil contained easily reducible manganese, because dried grass meal increased the numbers of manganese‐reducing micro‐organisms.
Effects of sacbrood virus on adult honey‐bees
Authors: BAILEY L. , FERNANDO E. F. W.
Published: February 2008

Much sacbrood virus accumulates in the brains of infected bees, especially of drones, without causing symptoms. However, infected individuals fly earlier in life than healthy bees and most infected foragers fail to collect pollen, as do bees briefly anaesthetized with CO2. The few infected bees that gather pollen contaminate their loads with much sacbrood virus. Infection does not shorten the lives of drones, or of workers that have been deprived of pollen, but it much shortens the prolonged lives of workers that have eaten pollen. Infected workers, healthy workers deprived of pollen, and senile individuals are unable to maintain the usual metabolic rates of bees at temperatures below 35oC, or to resist chilling.
Influence of pea‐root exudates on germination of conidia and chlamydospores of physiologic races of Fusarium oxysporum f. pisi
Authors: WHALLEY W. M. , TAYLOR G. S.
Published: February 2008

Sterile root exudates from wilt susceptible and wilt resistant pea cultivars showed no differential effects on spore germination ofFusarium oxysporumSchl.f.pisi(Linf.) Snyd. & Hans, races 1 and 2 which could be correlated with the pathogenicity of a particular isolate to a given cultivar. Uniformly high percentages of germination were obtained with conidia of the two races in aseptic shake culture with exudates collected from resistant or susceptible plants of various ages. Chlamydospores of the two races incubated with exudates under sterile conditions germinated to uniformly high levels irrespective of exudate origin. Conidia and chlamydospores ofFusarium solani(Mart.) Sacc. f.pisi(Jones) Snyd. & Hans., used for comparative purposes, also germinated to high levels in the presence of exudate solutions of all cultivars.

Non‐specific germination of the two races ofF. oxysporumf.pisioccurred in soil when the exudates were supplied to populations of chlamydospores via diffusion units. Germination was lower than that recorded under sterile conditions and was rapidly followed by germling lysis.
The role of weed hosts and the distribution and activity of vector nematodes in the ecology of tobacco rattle virus
Authors: COOPER J. I. , HARRISON B. D.
Published: February 2008

At a site in eastern Scotland, nine common species of arable weeds were infected with tobacco rattle virus (TRV), and some of these, notably Viola arvensis and Stellaria media, comprised an overwintering reservoir of the virus. TRV was seed‐borne both in naturally and in experimentally infected V. arvensis (2–10%), and occasionally in other weed species. In the glasshouse at 20 oC a naturally infective population of vector nematodes (Tricho‐dorus spp.) kept in soil free of plants retained its infectivity for 20 wk, although few Trichodorus survived for this period. In the field, the incidence of TRV infection in potato (spraing disease) in plots kept free of weeds for 1–5 years was 3–4 times that in weed‐infested plots but Trichodorus numbers did not differ appreciably between the two treatments. Presumably the virus is retained for long periods in its vectors and these feed on potato more frequently when other hosts are not available. Weeds are probably important in the long term as hosts of both TRV and its vectors, but in the short term weed control seems unlikely to prevent potato spraing because of the long persistence of TRV in vector populations.

In the field, Trichodorus accumulated near the interface between topsoil and subsoil, and the incidence of spraing was greatest where the topsoil was shallowest. When cucumber seedlings were exposed to virus‐carrying Trichodorus, TRV reached a greater concentration in roots at 20 oC than at 24 oC, and the virus was not detected in roots at 29 oC. In a sandy soil, TRV was transmitted only when the water content exceeded 15%, and at least 30 % water was needed for maximum transmission. Annual records of rainfall and spraing disease suggest that spraing is most prevalent when the summer is wettest.

TRV is not confined to cultivated land. Stabilized sand dunes supporting a pure stand of Ammophila armaria were colonized by Trichodorus pachyder‐mus, but TRV was detected only where the plant community had enlarged to include V. arvensis and other dicotyledons. In such situations, TRV may be introduced in the seed of V. arvensis, and the movement of soil by wind probably contributes to the dispersal of Trichodorus.
Long‐day effects on growth and flower initiation of tomato plants in low light
Authors: HURD R. G.
Published: February 2008

Young tomato plants (cv. Minibelle) were grown in plant growth cabinets in 575 kJ m‐2 (400–700 nm) daily radiation. Plants grown in an 8 h day were then compared with those in which 10% of the radiation was taken from the main 8 h light period and supplied over the next 8 h period. After 41 days from sowing the 16 h day plants had almost twice the dry weight of those in short days and a 55 % greater leaf area. Net assimilation rate, relative growth rate and relative leaf area growth rates were all greater in long days, although the differences in growth diminished with time. The long‐day treatment also increased the proportion of dry weight in the leaves, a function which is usually relatively stable in different environments.

The beneficial effect of the long days may arise from a reduction in night respiration, or an increase in rate of photosynthesis through the observed increase in chlorophyll content.

The 8 h light period resulted in flower initiation one or two nodes lower than the 16 h period so that the cultivar is a quantitative short‐day plant.
Cowpea mild mottle, a newly recognized virus infecting cowpeas (Vigna unguiculata) in Ghana
Authors: BRUNT A. A. , Kenten R. H.
Published: February 2008

Cowpea mild mottle virus (CMMV), a previously undescribed virus widespread in cowpeas (Vigna unguiculata) in the Eastern Region of Ghana, was seed‐borne in V. unguiculata, Phaseolus vulgaris and Glycine max, but was not transmitted by twelve aphid species including Aphis craccivora, A. fabae, Acyrthosiphon pisum and Myzus persicae. CMMV was transmitted by inoculation of sap to eleven of seventeen members of the Papilionaceae causing very severe diseases in G. max and Arachis hypogaea, and to ten of fifty‐one species within five of nineteen other families; it was best propagated in G. max and Nicotiana clevelandii, and assayed in Chenopodium quinoa. Sap from systemically infected G. max was infective after dilution to 10‐3 but not 10‐4, after 10 min at 65 °C but not at 70 °C, or after 4 days at 18 °C or 16 days at 2 °C. Lyophilized sap was infective after 3 years in vacuo.

CMMV has straight to slightly flexuous, fragile filamentous particles, c. 13 × 650 nm which, in sap, are occasionally surrounded by a loose external spiral. About 5 mg of purified virus was obtained from 1 kg of leaf tissue of G. max or N. clevelandii by clarifying leaf extracts in 0.02 m borate buffer (pH 9.5) with chloroform, followed by two or three cycles of differential centrifugation, and density gradient centrifugation. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 5 % nucleic acid, contained numerous particles without external spirals, which sedimented as a single component with a sedimentation coefficient (s°20, w) of 165 × 4S, and contained a single polypeptide species with a molecular weight of 32000–33000. CMMV showed a distant serological relationship to carnation latent virus, but not to ten other morphologically similar viruses; it thus seems to be a distinct member of the carlavirus group, and has the cryptogram: */*:*/(5):E/E:S/*.
The sowing of germinating vegetable seeds using a fluid drill
Authors: CURRAH I. E. , GRAY D. , THOMAS T. H.
Published: February 2008

Carrot seeds which had been imbibed or germinated and were then sown in a gel extruded through standard coulters emerged five days earlier than dry seeds sown with a conventional drill and gave higher yields after 64 days although not after 77 days. There was no difference in mean time to emergence or in final plant stand between lettuces grown from dry seeds and those from seeds imbibed for 24 h and sown in a gel, but the duration of the emergence period of the latter was halved in one of the two experiments. Celery seeds, the light requirements of which had been satisfied during germination in optimum conditions in the laboratory before they were sown in the field in a gel, gave a 60% plant stand as compared with a stand of 2% from dry seeds.
Studies on the sensitivity of monogerm sugar beet germination to water
Authors: PERRY D. A. , HARRISON J. G.
Published: February 2008

Excessive water in the substratum inhibited germination of monogerm sugar beet seed but it was not lethal, and other crop seeds tested were not as sensitive as beet. The inhibition was not evident in a pure oxygen atmosphere and was lessened when the fruit cap was removed. Although bacterial populations on fruits absorbed appreciable quantities of oxygen, differences between populations in optimum and excessive water were insufficient to account for the inhibition.

Anatomical observations revealed the presence of a pore through the sclerified fruit wall at the point of attachment to the mother plant. Evidence indicated that the pore was the route for oxygen and water uptake to the seed, and theoretical calculations of gas flux suggested that oxygen supply would be insufficient to sustain germination when the pore was filled with water.
A strategy for evaluating the safety of organisms for biological weed control
Authors: WAPSHERE A. J.
Published: February 2008

A strategy for establishing the specificity and safety of an organism as a biological weed control agent is described. A critical first step is to expose to its attack a small group of plants very closely related and exhibiting morphological and biochemical similarities to the weed. To prevent an erroneous negative result tests are also made on selected cultivated plants, including those closely related to the weed, those of which the associated insects and fungi are little known, those that have evolved apart from or been little exposed to the agent, those attacked by closely related organisms and those already recorded as hosts.

The circumstances under which the strategy might fail to indicate safety are discussed, i.e. polyphagous organisms attacking plants irregularly distributed throughout many families, organisms highly specific to two alternate hosts, and those attacking two or three phylogenetically widely separated plant groups. The additional crop plant testing, included in the overall strategy to deal with such possible failures, is discussed.

It is shown that the strategy would have included Sesamum tndicum in the list of plants challenged by the bug Teleonemia scrupulosa in biological testing for control of Lantana camara, thereby forewarning of the attack that was subsequently observed in Africa.
Evaluation of wheat cultivars for ability to retard development of stem rust
Authors: WILCOXSON ROY D. , SKOVMAND B. , ATIF A. H.
Published: February 2008

The ability of wheat cultivars (Triticum aestivum) to retard the development of stem rust, Puccinia graminis f.sp. tritici, was evaluated in hill plots for 3 yr at several locations in Minnesota, against single races and mixtures of races. The area under the disease progress curve was a convenient and reliable method for data summation, but the rate of disease development was not. When inoculated with single races (15B2, 32, 113 or 31) or with mixtures of races (11, 15, 15B2, 17, 32, 151), the cvs Exchange, Thatcher, McMurachy, Redman, Kenya 58, Frontana and Idaed retarded stem rust development more than Baart, Prelude and Marquis; Lee was intermediate. The methods and techniques reported should permit selection of cultivars capable of retarding the development of stem rust.
Host relations and distribution of a physiological and pathological variant of Pseudomonas morsprunorum
Authors: FREIGOUN S. O. , CROSSE J. E.
Published: February 2008

In a plot of sweet‐cherry trees (Primus avium), leaf spot infections caused by Pseudomonas morsprunorum were more abundant on the cv. Roundel than on the normally more susceptible cv. Napoleon. Roundel also supported significantly higher leaf surface populations of the pathogen. This reversal in the relative field susceptibility of the two cultivars was associated with the presence on the trees of a variant form of P. morsprunorum that differed from typical strains in colony structure, gelatinase activity and pathological characters. The variant strains were less infective through leaf scars but more invasive in bark parenchyma than typical strains, and in branch and leaf inoculations, they showed specialization for the cv. Roundel. This specialization was reflected in the distribution of variant and typical strains on Roundel and Napoleon trees in other localities. The significance of the variant in relation to disease epidemiology and cultivar resistance is discussed. The variant is designated race 2 to distinguish it from the typical, or race 1 cherry strains of P. morsprunorum.
Sugar concentration in sugar beet: varietal differences and the effects of soil type and planting density on the size of the root cells
Authors: MILFORD G. F. J.
Published: February 2008

Differences in beet weight and sugar concentration of four commercial varieties grown on two types of soil and at different planting density were related to changes in the numbers, sizes and sugar storage capacities of the storage root cells.

Much of the variation in beet weight between varieties and soil type was attributable to differences in cell size, less to differences in their number. Differences in weight of beet grown at different densities were caused equally by changes in number of cells and their size. Variation in sugar concentration of the beet was, in all cases, determined more by differences in cell size than in their capacity tostore sugar, but the two factors were not wholly independent of each other.
Germination of Puccinia striiformis uredospores on leaves of adult winter wheat plants
Authors: RUSSELL G. E.
Published: February 2008

In experiments with intact adult winter wheat plants and detached leaves, higher percentages of Puccinia striiformis uredospores germinated on the adaxial leaf surface, particularly the distal parts, than on the abaxial surface. This is consistent with the observation that the distal parts of the adaxial leaf surface are those which are most susceptible to yellow rust.

Higher percentages of uredospores germinated on leaves of some of the winter wheat varieties examined than on those of others. These varietal differences depended on the part of leaf and the race of P. Striiformis used for the comparisons. This suggests that the differences between varieties are partly race specific.
The geographical distribution of Xiphinema and Longidorus nematodes in the British Isles and Ireland
Authors: TAYLOR C. E. , BROWN D. J. F.
Published: February 2008

The distribution of Xiphinema and Longidorus species in the British Isles and Ireland were mapped by means of a computer programme from 5527 records. Longidorus caespiticola, L. elongatus, L. goodeyi and L. leptocephalus were found to be widespread among a wide range of vegetation types, particularly in grassland and arable crops; L. macrosoma and L. profundorum were recorded frequently in southern and central England, and L. attenuatus in East Anglia; L. vineacola was recorded once only in Eire. Paralongidorus maximus was recorded from two localities in eastern Scotland and one in southern England, on each occasion from intensively cultivated ground. Four species of Xiphinema were recorded but only X. diversicaudatum is widespread although apparently with a northerly limit in central Scotland; X. diversicaudatum was equally prevalent in arable crops, grassland and deciduous woodland; X. coxi and X. vuittenezi were recorded from a few scattered localities in England, and the few records for X. mediterraneum were all from Kent, south east England. All species were found in a wide range of soil types but mostly in light soils with a large sand fraction. Many of the species occurred together in mixed populations; L. caespiticola was most frequently associated with X. diversicaudatum and with L. leptocephalus and L. elongatus. X. diversicaudatum also was commonly found with L. goodeyi. Viruses were transmitted in laboratory bait tests in only eighteen of 325 soil samples containing X. diversicaudatum and four of 265 containing L. elongatus.
Effects of virus genotype and temperature on seed transmission of nepoviruses
Authors: HANADA K. , HARRISON B. D.
Published: February 2008

Transmission of different nepoviruses through chickweed (Stellaria media) seed was differently affected by ambient temperature during seed production. Raspberry ringspot and tomato black ring (Scottish isolate) viruses were similarly and frequently transmitted at14, 18 and 22 oC, whereas arabis mosaic virus was transmitted most frequently at 14 oC, and strawberry latent ringspot and tomato black ring (German isolate) viruses at 22 oC. When infected by seed‐borne nepoviruses, seedlings of S. media and other species were symptomless at 15–25 oC, and the viruses were therefore detected by inoculating sap to Chenopodium quinoa indicator plants. However, typical symptoms of arabis mosaic and tomato black ring viruses were induced by growing Nicotiana tabacum, N. clevelandii and C. quinoa seedlings infected with seed‐borne virus at 33–37 oC during the third and fourth weeks after sowing, preceded and followed by periods at 15–25 oC. The proportion of N. tabacum seedlings developing symptoms was the same as that of untreated seedlings yielding sap‐transmissible virus.

Seed transmissibility of pseudo‐recombinant isolates of raspberry ringspot and tomato black ring viruses, containing RNA‐i from one virus strain and RNA‐2 from another strain, depended greatly on the transmissibility of the strain contributing RNA‐i. The source of RNA‐2 had an additional but smaller influence. The satellite RNA (RNA‐3) of tomato black ring virus was seed‐transmitted in S. media and its occurrence in cultures did not affect the frequency of transmission of the virus. Results of testing the infectivity of extracts of seed from infected mother plants suggested that failure of seed transmission reflected failure to become established in the seed, not subsequent inactivation.

Whereas seed transmissibility of raspberry ringspot virus is primarily dependent on information carried in RNA‐i, transmissibility by nematode vectors, another property of major ecological importance, is determined by RNA‐2. In the field, selection pressures presumably can act independently on the two parts of the genome but evidence was also obtained of selection for mutual compatibility of RNA‐i and RNA‐2.
Cultural and insecticidal control of Thrips tabaci on onions in the Sudan
Authors: KISHA JENNIFER S. A.
Published: February 2008

Onion thrips (Thrips tabaci) is the major pest of onions in the Sudan. In the Gezira Scheme onions are normally transplanted between October and January when the thrips population is very low. Later, thrips commence to breed. Early transplanted onions were well established before infestations became severe and, without the need for insecticidal control, produced significantly higher yields. Onions transplanted later, when thrips began to multiply, produced lower yields.

Depending on the duration and intensity of infestation three to five sprays applied at fortnightly intervals were required to control thrips on the late transplanted crop. The effect of spray frequency on the development and yield of onions was investigated and the response found to be solely due to the extent of thrips control achieved. The toxicant itself had no effect on growth. Although the leaves were unaffected by the various treatments, spraying when most thrips were present increased fresh and dry leaf weights, bulb weight and, in the Hudeiba cultivar, the proportion of flowering plants.

With the late‐transplanted crop, light infestations led to yield losses of at least 39% whilst severe thrips attacks reduced the crop by 57%.
Role of weed grasses in the etiology of ergot disease in wheat
Authors: MANTLE P. G. , SHAW S. , DOLING D. A.
Published: February 2008

Forty isolates of the ergot fungus Claviceps purpurea collected from nineteen gramineous host species were used to inoculate male‐sterile wheat. The isolates segregated into highly and weakly infective groups. The marked pathogenicity, on wheat, of the fungal strains occurring on certain grass species has been correlated with distinctive patterns of alkaloids within the sclerotia.

Analysis of the alkaloid content of 241 samples of naturally occurring ergot sclerotia from twenty gramineous host species has confirmed the existence of host restricted strains characterized also by their particular spectra of alkaloids.

Similarity of the alkaloid spectra of ergot sclerotia from blackgrass (Alopecurus myosuroides) and wheat, ease of cross‐infection from blackgrass to wheat and an association between blackgrass infestation and the occurrence of ergot sclerotia in surveyed wheat crops have confirmed the hypothesis that the presence of this early flowering weed grass increases the risk of high levels of ergot infection in wheat.
Laboratory rearing of the mushroom phorid Megaselia halterata (Diptera: Phoridae)
Authors: RICHARDSON P. N. , HESLING J. J.
Published: February 2008

A technique used for 3 yr to produce 15 000–20 000 nematode‐free adult Megaselia halterata/v/k is described and its potential for future mass‐production of nematode‐parasitised flies, for use in biological control, is assessed. Gravid female phorids preferred to oviposit in compost in which mushroom mycelium had grown for 7–12 days. At 20 ± 1 °C flies began to emerge 24 days after adults of the previous generation had been released on the compost. By day28, 88% of the total population had emerged.

In laboratory experiments using different densities of parental flies, fly yield per female was highest when 200 flies infested each 1 kg of compost. At higher densities, competition between larvae affected survival of larvae and pupae, and probably resulted in the mean egg content of emerging flies being reduced by as much as 16‐4%. Theoretically, 250 kg compost should yield 1 150 000 phorids.
Development of the Dutch elm disease epidemic in southern England, 1971‐6
Authors: GIBBS J. N.
Published: February 2008

The current epidemic of Dutch elm disease was studied by recording the fate of individual hedgerow elms (Ulmus procera) in five plots in the West Midlands, and by analysing data from successive Forestry Commission surveys of non‐woodland elms in 234 plots in southern England.

Ninty‐five percent of the individual trees died between May 1972 and September 1975. The average infection rate (r) was found to be 1 ‐35 during the period when the proportion of disease, x, increased from 0–16 to 0–42. In the plots of the main survey the average infection rate was 0–65 and the cumulative loss increased from 6 to 62% between 1971 and 1976, with little evidence that the course of the epidemic was influenced by variations in the weather from year to year. These infection rates are as high as those recorded in Dutch elm disease epidemics elsewhere in the world. The infection rate in English elm was higher than in either the wych elm or the heterogeneous ‘smooth‐leaved elm’. The study of English elm in four geographical areas of southern Britain showed that there was an initial drop in infection rate until x = 0–12, when a steady infection rate obtained in all four areas, ranging from 0–56 in the Midlands to 0–76 in the south‐east. It is concluded that the epidemic is likely to continue at a high rate until most non‐woodland elm have died. Most trees which survive are likely to be smooth‐leaved elm in East Anglia.

Few communities in southern England have been able to practice vigorous sanitation control programmes, but data from two, in East Sussex and Brighton, are analysed and the effect on disease progress discussed.
Methods used to study Pythium oligandrum, an aggressive parasite of other fungi
Authors: Deacon J. W. , Henry Christine M.
Published: February 2008

Isolates of Pythium oligandrum Drechsler and P. acanthicum Drechsler behaved similarly in a range of experiments and in a manner consistent with mycoparasitism. They grew on cellulose in association with some fungi ‐ notably Botryotrichum pilulferum Sacc. & March. and Phialophora radicicola Cain var. radicicola (IMI 187786) ‐ and markedly reduced cellulolysis by these species; however, they had little effect on cellulolysis by Gaeumannomyces graminis (Sacc.) Arx & Olivier var. graminis and made little growth on cellulose in the presence or absence of this fungus.

Pythium oligandrum and P. acanthicum also grew rapidly across plates of potato‐dextrose agar precolonised by Phialophora radicicola var. radicicola, whereas isolates of P. echinulatum Matthews, P. mamillatum Meurs, P. megalacanthum de Bary, P. spinosum Sawada and P. ultimum Trow did not grow under these conditions. Precolonised agar plates were therefore used as a selective medium to isolate Pythium oligandrum and similar fungi from soils. For this, small pieces of soil organic matter were transferred to precolonised agar plates and incubated for 4–6 (‐12) days, when the presence of P. oligandrum or similar fungi was assessed by their production of spiny oogonia across the host colony. The technique proved successful in isolating these fungi from a wide range of cultivated soils, even if the soils had been stored air‐dry. However, boiled hemp seeds buried in soil and subsequently transferred to precolonised agar plates usually gave rise to phytopathogenic rather than mycoparasitic pythia.

Pieces of wheat straw precolonised by P. oligandrum decomposed at the same rate as virgin straws or straws precolonised by P. ultimum or Mucor hiemalis Wehmer, when all were buried in nitrogen‐supplemented soil. However, different cellulolytic fungi appeared to colonise straws in these respective treatments, Fusarium spp. being less common and Stachybotrys atra Corda more common in the presence of P. oligandrum than in its absence. When subsequently opposed to P. oligandrum on agar plates, Fusarium spp. appeared to be parasitised by this fungus and made very little growth across the agar, whereas S. atra grew through the colony of P. oligandrum and was clearly unaffected by the presence of this fungus.

Our results demonstrate the widespread occurrence of P. oligandrum in cultivated soils in Britain and also suggest that this species might influence the activities of other soil fungi.
Studies on the lenticel development, surface microflora and infection by common scab (Streptomyces scabies) of potato tubers growing in wet and dry soils
Authors: ADAMS M. J. , LAPWOOD D. H.
Published: February 2008

The mechanisms of control of potato common scab (Streptomyces scabies) by irrigation were investigated in 5 years by studying the growth and surface microflora of young potato tubers developing in wet or dry soils. Direct examination of the tuber surface by light or scanning electron microscopy showed that the newly formed internodes near the apex, which carry stomata, had a very sparse microflora. In dry soil the older internodes, which carry lenticels at a susceptible stage, were increasingly colonised by actinomycete hyphae and discrete, although sometimes large, bacterial colonies. In wet soil, actinomycetes were rarely seen on tuber surfaces but bacteria were generally scattered over them, differences not always shown by isolation from periderm pieces onto water agar.

When dry scab‐infested soil was wetted, scabs did not subsequently develop on the two youngest tuber internodes (A‐1, A‐2), which may be an example of disease escape rather than inherent resistance of the stomata. The scab control achieved in wet soil was probably caused by some form of microbial antagonism, but whether through competition or antibiosis was not established.
An investigation into inter‐plot interactions, in experiments with mildew on barley, using balanced designs
Authors: JENKYN J. F. , BAINBRIDGE A. , DYKE G. V. , TODD A. D.
Published: February 2008

Serial designs, balanced for effects of neighbours, were used in 1975–1977 to investigate interactions between plots of spring barley given different treatments for the control of powdery mildew (Erysiphe graminisDC. f. sp.hordeiMérat). Differences in amounts of disease, between similarly treated plots, could be related largely to the treatments applied to the neighbouring plots and to wind directions. Amounts of disease in plots were usually increased if the upwind neighbour was untreated but untreated plots themselves were also affected by neighbours, having least disease where the upwind neighbour was sprayed early.

Differences in mildew due to treatment were reflected in grain yield. Yields also provided evidence of interactions between plots. Interference, as well as altering the average response to treatments, can also contribute to variability in experiment results and lead to substantial losses in efficiency. The yields in 1975 and 1976 provided strong evidence of profiles of fertility. In the analyses, adjustment by covariates, employed to allow for these profiles, gave substantial net gains in accuracy.
Observations on the cabbage stem flea beetle, Psylliodes chrysocephala, on winter oil‐seed rape in Cambridgeshire
Authors: ALFORD D. V.
Published: February 2008

The biology of the cabbage stem flea beetle, Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), on winter oil‐seed rape crops was studied in Cambridgeshire from 1974 to 1978, with particular reference to autumn and winter activity. The timing of adult invasion of crops in the autumn and subsequent attack on plants by larvae showed considerable variation from year to year, being influenced mainly by temperature. Also, early‐germinating crops tended to be invaded earlier than later‐germinating ones. Egg development, which was closely correlated with temperature, required an accumulated sum of 240 day oC above 3.2 oC (calculated from daily mean temperatures). Monitoring adult activity, and consideration of temperature data, allowed dates of egg hatch to be predicted. The usefulness of this information for accurately timing chemical sprays against the pest is discussed.
Studies of halo‐blight seed infection and disease transmission in dwarf beans
Authors: TAYLOR J. D. , DUDLEY C. L. , GRAY) LORNA PRESLY (née
Published: February 2008

The transmission of Pseudomonas phaseolicola from plant to seed was mainly by the penetration of bacteria from external pod lesions to the underlying seeds. There was no evidence for translocation of bacteria from other parts of the plant to the seed, and symptomless pods contained only healthy seeds. Although a small proportion of infected seeds showed obvious symptoms of infection, the majority showed either slight symptoms, which could be detected only by careful observation, or were symptomless. In tests of disease transmission from seed to seedling, seeds with slight symptoms, or those which were symptomless were responsible for 35% and 52% respectively of the total disease transmission compared to 13% for obviously infected seeds. The viability of bacteria in seed stored under relatively uncontrolled conditions (10–27 d̀C) declined by a factor of 250 per annum over the first 3 yr with extrapolation predicting effective extinction after c. 5 yr. The pathogen survived longer under controlled conditions (7–10 d̀C and 45–50% r.h.) but no viable bacteria were detected in seed stocks which were 10‐yr‐old and with one exception 6‐yr‐old stocks were also free of the pathogen.
The biology of the ground beetle Harpalus rufipes in a strawberry field in Northumberland
Authors: LUFF M. L.
Published: February 2008

Harpalus rufipes (Degeer) was studied in a strawberry plot in Northumberland from 1973 to 1978 by pitfall trapping, and in the laboratory. Adults were active from April until November. Overwintered male beetles predominated at the beginning of each season until May, followed by overwintered females in June and July. Newly emerged, mainly female, beetles were active from August onwards. Overwintered females matured during early summer and laid eggs in August with a fecundity of 10–15 eggs/female. In the laboratory about 30% of beetles survived from one breeding season to the next.

First‐ and second‐instar larvae were caught in pitfall traps in autumn; in the laboratory they made approximately vertical burrows in which they stored seeds taken from the soil surface. Third‐instar larvae fed on these seeds and were not active on the surface. Preferred seeds were those of grasses and Chenopodium album L. Larvae were usually aggregated in the soil at densities of 3–20/m2.
Effects of Pythium species on the growth of apple and their possible causal role in apple replant disease
Authors: SEWELL G. W. F.
Published: February 2008

Several lines of circumstantial evidence collectively indicated that poor early growth of apple (‘replant disease’) might be associated with the effects of soil‐borne pythiaceous fungi. This hypothesis was supported by pathogenicity tests. All isolates tested of P. sylvaticum and certain isolates of seven other Pythium spp. significantly reduced the growth of apple seedlings. The growth reductions caused by certain Pythium isolates were of comparable magnitude to the growth increases occurring after chloropicrin‐fumigation of apple orchard soils. The Pythium isolates most virulent to apple were of low virulence to a clonal cherry rootstock.

Reappraisal of the nature of the disease as a non‐specific soil malaise is consistent with established features of the pathology of Pythium spp. The disease, however, is an ill‐defined ‘poor growth phenomenon’ with no diagnostic symptoms and conclusive evidence that Pythium spp. are widely causal is likely to be elusive.
Studies on the epidemiology of Alternaria brassicicola in Brassica oleracea seed production crops
Authors: HUMPHERSON‐JONES F. M. , MAUDE R. B.
Published: February 2008

Alternaria brassicicola lesions present on overwintered leaf litter of Brassica oleracea seed production crops produced high concentrations of spores in the spring, these were able to initiate new infections on foliage and subsequently on inflorescences and pods. A vertical disease gradient developed in maturing crops, the lowest pods becoming infected first and infection spreading slowly upwards. Spores were produced abundantly after 20 h leaf wetness at a mean temperature of 13°C or more. Their release was stimulated by a fall in relative humidity but inhibited at a constant high relative humidity resulting in a daily cycle in air spore concentrations with minimum numbers occurring in the early morning and maximum numbers in the early afternoon. For most of the growing season spore movement was restricted to within the crop, however, massive release of spores and subsequent distribution over a wide area occurred when the crop was cut and later threshed. Using semi‐selective agar traps spores released at these times were detected up to 1800 m downwind of the parent crop and were instrumental in infecting nearby young crops destined for seed production in the following season.
Pathogenic variability of downy mildew (Sclerospora graminicola) on pearl millet. II. Statistical techniques for analysis of data
Authors: BALL SARAH L. , PIKE D. J.
Published: February 2008

Different cultivars of pearl millet were exposed to infection by asexual propagules ofSclerospora graminicolain Polythene tunnels. Subsequent incidence of disease was measured on one‐month old seedlings. The data consisted of binomial proportions based on differing total numbers of seedlings. It is shown how to utilise the logit link in the GLIM statistical package for analysis to compare variety performances. In addition the possibilities of interplot interference and intraplot variation were investigated using GLIM. Interplot interference occurred infrequently and did not affect the rank order of the cultivars in terms of their response to the fungus infection. Intraplot variation was also shown to be non significant in spite of proximity of some plants to the disease spreader plants. Once these potentially confounding phenomena were eliminated the cultivars could be compared directly with impunity. GLIM was also used to confirm that the type of symptom expression was a stable feature of each host genotype.
Chemical treatments for control of decay in pruning wounds
Authors: MERCER P. C. , KIRK S. A. , GENDLE P. , CLIFFORD D. R.
Published: February 2008

Wound treatments were evaluated, in the laboratory and the field, for their effect on beech and poplar tissue (phytotoxicity) and on the growth and colonisation pattern of micro‐organisms. Three types of treatment were examined: a physical barrier or sealant, a sealant plus fungicide and a fungicide alone. Greatest phytotoxicity was shown by materials normally employed as timber preservatives and the least by sealants. Generally colonisation by fungi and bacteria was little delayed by most treatments with the exceptions of Santar (sealant plus mercuric oxide) and Australian Arborseal (sealant plus captafol). However, colonisation by basidiomycetes was generally delayed by treatment, but its overall intensity was reduced only by Santar and Lac Balsam (sealant). Some treatments had a selective effect on the species of micro‐organisms colonising a wound ‐ thus wounds treated with carbendazim derivatives were most likely to be colonised by basidiomycetes and Alternaria spp. Treatment with Santar discouraged most micro‐organisms with the exception of Phoma spp.

No sealant provided a visually intact cover for longer than 12 months: even wounds with apparently intact cover occasionally had fruit bodies of decay fungi present on them. The chemicals triadimenol, triadimefon, carbendazim and thiophanate methyl were still present in fungicidal amounts in wounds up to at least 157 days. Both Santar and triadimenol prevented the growth of Trametes versicolor from inoculum plugs in wounds of apple trees.
Ecology of nematophagous fungi: distribution and habitat
Authors: GRAY N. F.
Published: February 2008

A survey of 161 samples of soil and plant material collected from sites throughout Ireland has shown that nematophagous fungi exist in a wide range of habitats. 205 isolations were made consisting of 11 endoparasitic and 20 predatory species. The commonest endoparasites and their frequency of occurrence were Myzocytium spp. (9·3%), Acrostalagmus obovatus (6·8%) and Harposporium anguillulae (6·2%). Predators were equally abundant, the commonest being Dactylella bembicodes (8·7%), D. mammillata (6·8%) and D. ellipsospora (6·2%). Arthrobotrys oligospora and A. musiformis both had a highly restricted distribution. Adhesive knobs and constricting rings were significantly more abundant than the other trapping mechanisms.

All the samples were classified into one of 10 broad habitat types. Of these temporary agricultural pasture, coastal vegetation and coniferous leaf litter had the greatest percentage of sites from which nematophagous fungi were isolated. A number of species showed distinct habitat associations, in particular Arthrobotrys robusta, A. musiformis and Dactylella cionopaga.
The use of polyethylene bags in the culture and study of Striga spp. and other organisms on crop roots
Authors: PARKER C. , DIXON N.
Published: February 2008

A technique is described by which root parasites such as Striga and Orobanche species may be grown on the roots of suitable host plants growing on a layer of glass‐fibre filter paper in a flattened, standard polyethylene bag. The single‐bag units are compact, inexpensive, simple to set up and allow repeated observation without damage. Some other potential uses of the technique are described.
The effect of leachates from grass trash on establishment of ryegrass
Authors: MARSHALL A. H. , NAYLOR ROBERT E. L.
Published: February 2008

These experiments have shown that whilst leachates from grass trash produced by killing grass with glyphosate can significantly affect germination and seedling growth of both perennial and Italian ryegrass on germination paper and on inert media, they had no effect when added to seeds on soil. This suggests that these leachates are unlikely to inhibit germination in direct drilled sowings in the field unless seeds are sown in direct contact with grass trash and in conditions of sufficient moisture availability to enable production of the leachates.

Comparisons of the effect of leachates from grass killed with herbicides or by drying, both before and after passing through a soil column further confirmed this and suggested that the effect of these leachates could partly though not wholly be attributed to herbicide residues on the trash.

Glyphosate was less toxic to germination than paraquat. However on sandy soils, glyphosate residues could still cause a reduction in germination. Surface trash produced by spraying with glyphosate had no effect when seeds were sown at a depth of 1 cm, again confirming that seeds must be in close proximity to grass trash before germination and establishment is reduced.
Laboratory tests on mating competition between thiotepa‐sterilised and normal males of the potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)
Authors: NABI M. N. , HARRISON R. A.
Published: February 2008

Male potato moths less than 24‐h‐old were sterilised in fumigation chambers in the laboratory with one of three concentrations of thiotepa 0·05, 0·075 and 0·1 g at either 25 or 30°C. Sterile males were associated with untreated virgin males and virgin females in the ratios of 1:1:1, 2:1:1, 4:1:1 and 1:0:1. The sterile and normal male contingents were placed with a single female. The percentage of egg hatch after mating decreased with the increase of concentration and the sterile male ratio. Sterile males were competitive in mating and their longevity was not adversely affected in comparison to the control groups.
Biological treatments for the control of decay in tree wounds.: Laboratory tests
Authors: MERCER P. C. , KIRK S. A.
Published: February 2008

Non‐decay fungi and bacteria which had been isolated from pruning wounds of beech (Fagus sylvatica) were examined for their ability to check the growth of decay fungi in a number of laboratory tests. Several fungi and bacteria inhibited growth although the degree of inhibition varied to some extent with the test. The most consistently antagonistic fungi were Trichoderma spp., especially an isolate of T. viride. The most antagonistic bacteria were Bacillus spp.
Olive latent virus‐1, an isometric virus with a single RNA species isolated from olive in Apulia, Southern Italy
Authors: GALLITELLI D. , SAVINO V.
Published: February 2008

A mechanically transmissible virus isolated from some olive trees growing in Apulia, Southern Italy is described under the name of olive latent virus‐1 (OLV–1). Virus particles (c. 30 nm in diameter) sedimented as a single component (11 IS) and contained a major single‐stranded RNA species which when denatured had a size of about 4100 nucleotides and up to seven smaller RNAs. When centrifuged to equilibrium either in CsCl or CS2SO4 gradients, virus preparations were homogeneous. In polyacrylamide gel electrophoresis, about 50% of virus coat protein preparations formed a band of mol. wt 32 000 (32K protein) but two other bands of mol. wt 36 000 (36K protein) and 65 000 (65K protein) and some diffuse bands were also observed. The 32K protein, its probable dimer (65K protein) and diffuse bands are regarded as components of virus coat protein, whereas the 36K protein is probably a contaminant from the host plant. Virus particles were stabilised by divalent cations, pH‐dependent bonds and salt links between protein and RNA. EDTA‐treated virions were sensitive to ribonuclease and SDS.

OLV‐1 was serologically unrelated to four tombusviruses, seven sobemoviruses or putative sobemoviruses, and seven other single component isometric plant viruses.
The technology of ethylene control: use and removal in post‐harvest handling of horticultural commodities
Authors: KNEE M. , PROCTOR F. J. , DOVER C. J.
Published: February 2008

A meeting of the Post‐Harvest Biology Group of the Association of Applied Biologists on 26 April 1984 discussed the significance of ethylene in the post‐harvest handling of horticultural commodities. The natural production of ethylene by crops and the risks of accidental exposure were surveyed. The effects of ethylene on plants were described in terms of ability to respond (responsiveness) and the relationship between response and concentration of ethylene (sensitivity). Sensitivity is related to the properties of ethylene receptors and may be common to all plant tissues. The varying responses to ethylene of fruits, vegetables and ornamentals were described. The limited studies of production and action of ethylene under temperature and atmosphere conditions of normal post‐harvest handling were reviewed. Methods of applying and removing ethylene were evaluated in terms of their practicality and applicability. The methodology of ethylene measurement was briefly considered. The potential for further research on post‐harvest significance of ethylene was discussed.
Nutrient availability effects on vesicular‐arbuscular mycorrhizal bell pepper (Capsicum annuum) seedlings and transplants
Authors: HAAS JERRY H. , BAR‐TAL A. , BAR‐YOSEF B. , KRIKUN JAMES
Published: February 2008

Pepper (Capsicum annuum) seeds were sown in nutrient‐poor sand or nutrient‐rich peat/vermiculite amended or not amended withGlomus macrocarpum. The vesicular‐arbuscular mycorrhizal (VAM) seedlings were irrigated with three levels of nutrient solution, and transplanted into four levels of P‐amended soil, each of which was irrigated with two levels of nutrient solution minus P. Mycorrhizal seedlings in sand were responsive to increasing nutrient levels; in nutrient‐rich peat the seedlings did not respond to additional fertilisation. The greatest seedling development accompanied by good fungus colonisation was in nutrient‐poor medium irrigated with the highest nutrient solution tested (18 mM N, 1.2 mM P, and 7 mM K). Non‐VAM plants almost ceased growing between the weeks 4 and 5, whereas VAM plants increased in weight by 41–188%. After transplanting, sand‐grown seedlings benefited from VAM when 300 mg P/kg or more was added to the soil but peat‐grown plants did not. Fruit development was delayed in all non‐VAM plants compared with VAM ones.