bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in the virulence of Verticillium dahliae from strawberry
Authors: TALBOYS P. W.
Published: February 2008

Isolates of V. dahliae from strawberry, tested in 1968 against cv. Cambridge Vigour, showed differences in virulence; in cvs Talisman and Cambridge Favourite there were no significant differences between plants that were inoculated and those that were not. Evidence from this experiment, and from an earlier non‐replicated experiment with Cambridge Favourite, in which differences of virulence had been apparent, showed that environmental factors can cause variations in disease development that are of similar magnitude to those attributable to genetic variations in host and parasite.
A comparative study of Phialophora radicicola, an avirulent fungal root parasite of grasses and cereals
Authors: BALIS C.
Published: February 2008

The biology and infection‐behaviour of a typical isolate of Phialophora radicicola Cain have been compared with those of a representative isolate of Ophiobolus graminis (Sacc.) Sacc. Both species can utilize a nitrate source of nitrogen and both require thiamine and biotin for growth on inorganic nitro‐gen; P. radicicola, but not O. graminis, was able to synthesize biotin when grown on asparagine as a nitrogen source. The pH range for good growth of P. radicicola in nutrient solution was narrower than that for O. graminis, and its growth rate on agar was only one‐third. P. radicicola was the more active decomposer of cellulose, and its cellulolysis adequacy index was I.66 as com‐pared with a value of 0.33 for 0. graminis. In agreement with prediction from Garrett's (I966) hypothesis on the cellulolysis adequacy index, saprophytic survival of P. radicicola in wheat straw was shortened by additional soil nitrogen, which prolongs survival of O. graminis.P. radicicola was found to spread ectotrophically over the roots of wheat, oats and barley by runner hyphae indistinguishable from those of O. graminis, but cortical infection caused no necrosis and no discernible check to growth of the infected cereals, nor any significant decrease in grain yield of inoculated wheat grown to maturity. Pre‐existing infection of wheat roots by P. radicicola retarded spread of infection by O. graminis; inoculation of several grass species with P. radicicola reduced the extent of infection by O. graminis of wheat following the grasses.
Local redistribution of fungicides on leaves by water
Authors: HISLOP E. C. , COX T. W.
Published: February 2008

Local redistribution of various fungicides applied as large or small droplets to detached broad‐bean leaflets was examined by laboratory bio‐assay with Botrytis fabae and by leaf‐printing techniques. The results showed that fungicidal particulate and soluble material will spread in water from the initial deposits and that the protected areas on leaves inoculated after washing were often much greater than on unwashed leaves. The extent of redistribution was related to the inherent toxicity, physical form, duration of weathering and tenacity of the fungicides. The effects of formulating copper oxychloride and zineb fungicides with surface‐active agents and adhesives seemed due to differences in the tenacity of the deposits. Results indicated that similar types of redistribution would occur in the field, but the possible importance of the electrokinetic theory of redistribution was not proven.
Fungitoxic action of dimethirimol and ethirimol
Authors: BENT K. J.
Published: February 2008

The systemic fungicides dimethirimol and ethirimol were shown to be toxic to spores of Erysiphe graminis and Sphaerotheca fuliginea, in germination tests in vitro. Toxicity of dimethirimol to spores of Botrytis fabae, Phytophthora infestans, Puccinia recondita, Uncinula necator and Venturia inaequalis was relatively feeble or absent. When applied in foliage sprays or in root treatments, both compounds inhibited the emergence of germ tubes from powdery mildew spores on cucumber and barley plants. The specific disease control shown by these fungicides can be explained by their direct fungitoxic action.

The effects of dimethirimol and ethirimol on powdery mildew infections and on spore germination were greatly decreased by the presence of riboflavin in the light. A rapid photo‐chemical interaction between riboflavin and dimethirimol was demonstrated. Marked reversals both of disease control and of fungitoxicity were also given by folic acid, and it is suggested that folic acid overcomes a metabolic block induced in powdery mildew fungi by the fungicides.
Tests of dibutyltin compounds as potato blight fungicides
Authors: McINTOSH A. H.
Published: February 2008

Dibutyltin dicarboxylates were about one‐tenth as effective as fentin acetate in controlling potato haulm blight (Phytophthora infestans) in laboratory tests on detached leaflets, but were less phytotoxic. Tributyltin acetate was no more effective than dibutyltin diacetate; dioctyltin dichloride was ineffective.
Pollen release by diploid and tetraploid sugar‐beet plants
Authors: SCOTT R. K. , LONGDEN P. C.
Published: February 2008

Pollen released during three summers at Broom's Barn, Suffolk, by diploid and tetraploid multigerm sugar‐beet plants was caught by automatic volumetric spore traps and by glass funnels situated in the crop. Tetraploids produced on average 66% as much pollen as diploids, their pollen grains were larger and they needed drier air to release pollen, the concentration of which increased more slowly early in the day and was particularly small on dull, damp days. Pollen catches from diploids and tetraploids decreased at a similar rate with increasing distance from the pollinators. The germination of fruits harvested from male‐sterile plants among the pollinators was consistently less with a tetraploid than with a diploid pollinator, but was not affected by distance of the male‐sterile plants from either pollinator.
The cuticles of some Angiosperm leaves and fruits
Authors: HOLLOWAY P. J. , BAKER E. A.
Published: February 2008

The cuticles of twenty‐four species from a wide range of mono‐ and di‐cotyledonous plants were examined by chemical methods. The cuticles differ markedly in the amount and composition of the surface wax, in the thickness of the cuticular membrane, and in the content and composition of the cutin of the membrane. Fruits usually have heavier wax deposits and much thicker membranes than leaves. No direct relationship exists between surface waxiness and thickness of the membrane. Alkanes and primary alcohols are prominent in many of the surface waxes; triterpenoids occur less frequently. The cutin content of the membrane varies considerably; a delicate membrane tends to have a low content of cutin in which fatty acids are prevalent, and a well‐developed membrane a higher content of cutin more rich in hydroxy‐fatty acids. 10,16‐Dihydroxyhexadecanoic acid is often an important constituent of cutin; 9,10,18‐trihydroxyoctadecanoic acid is most prominent in the cutin of thicker membranes. The possible influence of the variations in cutin acids upon the structure of cutin and the taxonomic implications of wax and cutin composition are discussed.
Some effects of barley yellow dwarf virus on spring and winter cereals in field trials
Authors: DOODSON J. K. , SAUNDERS P. J. W.
Published: February 2008

The tolerance of spring and winter cultivars of wheat, barley and oats to infection by barley yellow dwarf virus (BYDV) was examined in field tests. Sererely affected plants were stunted and grain yields were considerably reduced. These changes in infected spring barley cultivars were associated with decreases in both ear length and number and sizes of grain. Most barley and oat cultivars were more susceptible than wheat cultivars. Yield losses decreased with successively later dates of inocultaiton, the yield response being characteristic of the tolerance of individual cultivars. Differences between tolerant and susceptible cultivars were insignificant in most cases where infection occurred after growth stage 7.

Individual seedling symptoms assessed in April and May were more closely related to each other and to yield losses than those recorded in March and June. The incorporation of seedling symptoms into indices of infection permits estimates of decrease in yield to be made by applying the formulae,

DY = (LC+LA+SH)/3

to barley cultivars and

DY = 1.7 × (LC+LA+SH)/3 ‐ 7

to oat cultivars. Thus decreases in grain yield (DY) can be related to decreases in seedling height (SH) and increases in percentage of leaf area discoloured (LA) and intensity of discoloration (LC).

Plot symptoms of infection, scored on a 0–7 scale, offered a more convenient method of assessment than individual seedling symptoms. Plot scores (PA) were closely correlated with other seedling symptoms and with decreases in grain yield (DY), and can thus be used to estimate yield losses by substituting into the formula, DY = 14PA (April)‐8. This formula was found to be applicable to all cereal cultivars examined in N.I.A.B. trials, there being no distinction between wheat, barley and oats.
Environmental factors influencing the infection of wheat by Puccinia graminis
Authors: BURRAGE S. W.
Published: February 2008

Germination rate and total germination of Puccinia graminis uredospores were directly related to pustule age and duration between spore collections. Partial drying of the spores enhanced germination rate; keeping them for 18 h at 100% r.h. reduced both rate and total germination. Spores germinated in polystyrene dishes between 4 and 29 °C and optimally between 15 and 23 °C Light (3 cal/cm2/h) had little effect on germination on moist surfaces but inhibited germination on the leaf. In Hybrid 229/8 wheat this effect was more pronounced than in var. Little Club. The number of primary infections increased linearly with duration of surface wetness with a narrow temperature optimum at 23.5 °C.

Two phases of infection could be distinguished: germination (requiring darkness and capable of taking place over a wide temperature range) and penetration (requiring light and slightly higher temperature than for germination). Stomatal closure caused by subjecting the plants to water stress led to proporational reductions in infection. The results are discussed in relation to dew formation.
Some chemicals to prevent stump colonization by Fomes annosus (Fr.) Cooke
Authors: PHILLIPS D. H. , GREIG B. J. W.
Published: February 2008

In tests to find a replacement for creosote, widely used for painting conifer stumps to prevent colonization by Fomes annosus, the best all‐round results were given by sodium nitrite. This has therefore been introduced in the forest, though, as it is poisonous to man and to animals, urea or disodium octoborate (‘Polybor’) may be used instead where labour cannot be well controlled, or there appears to be a danger to unattended livestock or to water supples.
Lethal bole rot disease of coconut in East Africa
Authors: BOCK K. R. , IVORY M. H. , ADAMS B. R.
Published: February 2008

A lethal bole, rot disease of coconut, caused by Marasmiellus cocophilus Pegler, sp. nov., reaches epidemic proportions in several areas along the coasts of Kenya and Tanzania.

The first symptoms noticed on palms 8 or more years old are a frond wilt and a crown rot, but these follow a primary bole rot. Highest mortality is among seedlings and young palms up to 8 years old.

Where the disease occurs sporophores are sometimes common on exposed roots, dead seedlings and the soil surface where diseased palms have been dug out. The fungus appears to be a persistent colonizer of coconut debris in the soil.

Mycelial cultures from infected bole tissues and from sporophores were highly pathogenic to seedlings, and slowly invaded older tissue. M. cocophilus reaches the inner bole tissues only through the roots, and wounding of roots of their aerenchymatous protuberances is important in infection.

Seedlings may become infected through roots damaged during transplanting from nurseries to the field; movement of seedlings from affected areas is one certain method of dispersal.

Suggested control measures are: (1) selection of seedlings in nurseries and subsequent transplanting should be as early as possible; (2) seedlings should be transplanted very carefully, and damaged roots pruned and disinfected; (3) seedlings should never be taken from affected areas; (4) periodic soil sterilization of nurseries; and (5) no cultivation should be done between palms, especially where disease is present.
Comparison of the biology of Myzus persicae Sulz. resistant and susceptible to dimethoate
Authors: BANKS C. J. , NEEDHAM P. H.
Published: February 2008

Apterous Myzus persicae resistant to dimethoate reproduce for the same length of time as susceptible aphids, but the resistant ones reproduce significantly faster during the first 10 days of adult life (especially during the first 5 days). Thereafter, they reproduce more slowly, and eventually the susceptible aphids produce approximately the same number of larvae. Resistant aphids die significantly younger. Resistant aphids as larvae develop faster than susceptible ones and are significantly heavier when they first become adult. The resistant aphids do not excrete faster during the first few days but, as they produce more larvae during the first 10 days of adult life and have developed faster, they probably feed faster during development and early adult life or obtain more nutritious food.

Resistant aphids were at least as effective as susceptible ones in transmitting sugar‐beet mosaic and pea mosaic viruses, and plants showed symptoms sooner when resistant aphids were the vectors.
Needle nematodes (Longidorus spp.) and stubby‐root nematodes (Trichodorus spp.) harmful to sugar beet and other field crops in England
Authors: WHITEHEAD A. G. , HOOPER D. J.
Published: February 2008

Longidorus attenuatus produces galls at the tips of roots of field crops, including sugar beet, growing in alkaline, sandy soils in eastern England. L. elongatus produces similar, but often larger, galls on the roots of sugar beet and other crops in sandy soils in the W. Midlands and in Fen peats. Trichodorus spp. cause ‘stubby root’ of sugar beet and can feed on many field crops. Seven species of Trichodorus were found in sandy soils in eastern England. L. attenuatus, L. elongatus and Trichodorus spp. aggregate around roots and stunt sugar beet and other crop plants. L. attenuatus is commoner below plough depth than in the topsoil, whereas T. cylindricus, T. pachy‐dermus and T. anemones are more abundant in the topsoil. These nematodes cause some forms of ‘Docking disorder’.
The effect of D–D, chloropicrin and previous crops on numbers of migratory root‐parasitic nematodes and on the growth of sugar beet and barley
Authors: WHITEHEAD A. G. , FRASER JANET E. , GREET D. N.
Published: February 2008

Thirty‐three gal D–D or chloropicrin/acre (371 l/ha) injected during winter into well‐drained, sandy soils controlled Longidorus attenuatus, Trichodorus spp. and other migratory root‐parasitic nematodes and resulted in greatly increased yields of sugar beet for at least 3 years; 2 years of bare fallow was less effective than soil fumigation. Trichodorus spp. multiplied more on sugar beet than on barley, whereas L. attenuatus multiplied more on barley and clover than on sugar beet.
Variations in the resistance to Heterodera rostochiensis of potatoes derived from Solarium tuberosum ssp. andigena and S. multidissectum
Authors: PARROTT D. M. , TRUDGILL D. L.
Published: February 2008

The proportion of larvae from ten populations of Heterodera rostochiensis Woll. that became female was determined on five potato clones containing genes for resistance derived from S. tuberosum ssp. andigena., on three with genes from S. multidissectum and on four with genes for resistance from both sources. Variations in the resistance of the clones bred from andigena, especially to two of the populations, suggest the presence of more than one gene for resistance.
Host range and some properties of potato mop‐top virus
Authors: HARRISON B. D. , JONES R. A. C.
Published: February 2008

Potato mop‐top virus (PMTV) was transmitted by inoculation of sap to twenty‐six species in the Solanaceae or Chenopodiaceae and to Tetragonia expansa; species in eleven other plant families were not infected. The virus was cultured in inoculated leaves of Nicotiana tabacum cv. Xanthi‐nc or in N. debneyi. Diagnostic local lesions were produced in Chenopodium amaranticolor. In winter, ten solanaceous species were slowly invaded systemically but the first leaves infected were those immediately above inoculated leaves. When transmitted to Arran Pilot potato by the vector Spongospora subterranea, PMTV induced all the main types of shoot and tuber symptoms found in naturally infected plants. Isolates of PMTV from different sources differed considerably in virulence.

PMTV‐containing tobacco sap lost infectivity when heated for 10 min at 80 °C, diluted to 10‐4, or stored at 20 °C for 14 weeks. Infectivity was partially stabilized by 0·02% sodium azide. When sap was centrifuged for 10 min at 8000 g, infectivity was mainly in the sediment. Infective sap contained straight rod‐shaped particles about 20 nm wide, with lengths up to 900 nm and crossbands at intervals of 2·5 nm. Many of the particles were aggregated side‐to‐side, and the ends of most seemed damaged. The slight infectivity of phenol‐treated leaf extracts was abolished by pancreatic ribonuclease. The present cryptogram of PMTV is R/*:*/*:E/E:S/Fu.
The long‐term survival of some plant viruses preserved by lyophilization
Authors: HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Seventy‐four viruses were tested for survival after lyophilization of infective sap and subsequent storage in vacuum‐sealed ampoules at room temperature. Fifty‐seven viruses survived at least i year and 19 of them over 10 years. The best results were obtained from host plants not containing inhibitors of infection or potent phenol oxidase systems. Purified preparations were also lyophilized. Lyophilization offers many advantages for maintaining a culture collection of sap‐transmissible viruses.
The resistance and tolerance of different cocoa varieties to cocoa swollen‐shoot virus in Ghana
Authors: LEGG J. T. , KENTEN R. H.
Published: February 2008

The resistance and tolerance to infection with cocoa swollen‐shoot virus (virulent strain A) of forty‐five and thirty‐eight cocoa progenies respectively was estimated using a manual inoculation method. Resistance was estimated from the proportion of inoculated seedlings which developed symptoms, and tolerance from the severity of these symptoms during a 4‐month period. Resistance was found among Nanay, Iquitos and Scavina, all Upper Amazon types; and an inter‐Nanay cross was outstandingly resistant and offers scope for improvement by breeding. Some Amazon‐Amazon and Trinitario‐Amazon progenies snowed tolerance, especially those with Trinitario T9/21 as a parent. Some progenies seem sufficiently promising for field testing to select varieties suitable for planting in those areas in Ghana where swollen‐shoot disease is epidemic.
Host range, properties and purification of raspberry bushy dwarf virus
Authors: BARNETT O. W. , MURANT A. F.
Published: February 2008

Raspberry bushy dwarf virus (RBDV) was found in all plants of Lloyd George raspberry with bushy dwarf disease and occurred occasionally in plants of some other cultivars. It was transmitted by inoculation of sap to fifty‐five other species in twelve families of flowering plants and infected most of them symptomlessly. It caused systemic symptoms in some species of Amaranthaceae, Chenopodiaceae and Cucurbitaceae, and necrotic local lesions in some Leguminosae. It did not induce bushy dwarf disease when returned to Lloyd George raspberry.

Chenopodium quinoa was used for propagating the virus and Vigna cylindrica for local lesion assay. In C. quinoa sap, RBDV lost infectivity when diluted 10‐4, heated for 10 min at 65 °C or stored for 4 days at 22 °C. Preparations made by twice precipitating the virus at pH 4·8 and resuspending it at pH 7·0, followed by ultracentrifugation and exclusion chromatography in columns of 2 % agarose beads, contained isometric particles about 33 nm in diameter, which sedimented as two components, with sedimentation coefficients of 111 and 116S. Only a few particles, all of them disrupted, were seen in preparations mounted in phosphotungstate, but the particles were well preserved in uranyl formate provided that they were first dispersed in a saxlt such as MgCl2 instead of distilled water. Many particles were oval in outline as though distorted during drying.

No serological relationship was detected between RBDV and twenty‐four other isometric viruses nor between RBDV and the filamentous virus apple chlorotic leafspot, to which it was previously thought to be related. An isolate of loganberry degeneration virus was serologically indistinguishable from RBDV.
Evaluation of some coccinellid species for the biological control of aphids in protected cropping
Authors: GURNEY BARBARA , HUSSEY N. W.
Published: February 2008

Four species of Coccinellidae, Adalia bipunctata (L.), Coccinella septem‐punctata L., Coelomegilla maculata de G. and Cycloneda sanguinea L., were compared as predators of aphids on cucumbers and chrysanthemums. In laboratory feeding tests C. maculata and C. sanguinea proved the most voracious but the former could not remain on cucumber foliage long enough to be effective. The fecundity of C. sanguinea was the highest of those studied and a satisfactory laboratory rearing technique has been developed for this species.
The curative activity of non‐ionic surface‐active agents against some powdery mildew diseases
Authors: EVANS E. , MARSHALL J. , COUZENS B. J. , RUNHAM R. L.
Published: February 2008

Eight non‐ionic surfactants of the general formula RO(C2H4O)nH were examined as fungicides for the control of various powdery mildew diseases. Those based on the condensation products of cetyl and oleyl alcohol with ethylene oxide were effective only as curative fungicides, having very little protective potential. This activity was greatest in products with n= 6–10. The most effective derivative, having eight ethylene oxide units, was particularly active in greenhouse tests against Sphaerotheca fuliginea on cucumber, S. pannosa on roses, and Podosphaera leucotricha on apples at concentrations which were not damaging to these crops. Although this compound caused damage to apples in the field it was effective against rose mildew and apple mildew, and its purely curative action gave a level of control equal to the standard dinitro compounds, which are capable of acting as either protectant or curative fungicides. This suggests that the dinitro‐compounds also probably act mainly in a curative fashion against these diseases in the field.
Tests of fungicides against Alternaria brassicicola and studies on some factors enhancing attack by the fungus
Authors: CHANNON A. G.
Published: February 2008

When various fungicides were sprayed on detached cabbage cotyledons in the laboratory and on young plants in the glasshouse, propineb and mancozeb at 0·2 % a.i. consistently gave good protection against subsequent infection by spores of Alternaria brassicicola. Copper oxychloride, zineb, thiram and maneb showed promise in the laboratory, but were less successful in the glasshouse. Two fentin compounds were active at low concentrations against the fungus but were phytotoxic.

Increased pathogenicity of A. brassicicola in the presence of cabbage pollen and of downy mildew infection in the laboratory is reported.
Effects of treatment with phenylthiosemicarbazide and 4‘‐chlorophenylthiosemicarbazide on Fusarium wilt of pea and tomato plants
Authors: FUCHS A. , HOMANS A. L. , VRIES F. W. de
Published: February 2008

Effects of treatment with phenylthiosemicarbazide (PTS) and its 4′‐chloro‐derivative (4′‐chloro‐PTS) on Fusarium wilt of pea and tomato plants were investigated. Depending on pH and availability of oxygen, PTS and 4′‐chloro‐PTS are converted to their corresponding phenylazothioformamides and phenylazothioformamide‐S‐oxides, which are the actual fungitoxic compounds. PTS and 4′‐chloro‐PTS were shown to inhibit growth of Fusarium oxysporum f. pisi and F. oxysporum f. lycopersici in liquid media as well as on agar plates at concentrations of 50–100 mg/1. Inhibition was greater at pH 7 than at pH 5. When administered to pea and tomato plants, both compounds caused severe phytotoxic effects, especially at temperatures favouring Fusarium wilt, thus almost entirely obscuring any protective activity against the diseases. All compounds were strongly adsorbed to loam, but readily released from sand. Neither in pea nor in tomato plants were PTS and 4′‐chloro‐PTS converted to any fungitoxic substance, not already present in the aqueous solutions administered.
Water deficit in potato plants infected with Verticillium albo‐atrum
Authors: HARRISON J. A. C.
Published: February 2008

Potato plants infected with Verticillium albo‐atrum, whether they showed disease symptoms or not, invariably had a lower leaf water content than healthy plants. This water content fell throughout the growing season as the disease progressed and showed greater diurnal fluctuations than in healthy plants. Wilting appeared in diseased plants when a water saturation deficit of c. 20% was attained, but in healthy plants occurred at marginally lower deficits. The acropetal development of wilting symptoms was reflected in the gradient of water deficits along the main axis of the plant.

Deficits of 10–28%, which commonly occurred in infected plants grown both in pots and in the field, would suggest that these plants are experiencing internal water stress throughout much of the season, and consequently may have reduced rates of photosynthesis.
3,5‐Dichlorophenoxyacetic acid as a growth retardant
Authors: SMITH MARGARET S. , MOHSIN MOHAMMED
Published: February 2008

Tomato seedlings, grown in the glasshouse, were sprayed with solutions of 3,5‐dichlorophenoxyacetic acid as sodium salt at 2 times 10‐5, 4 times 10‐5 and 10‐4 M. The treated plants became dark‐green, dwarfed, and compact. After 6–7 weeks normal growth was resumed. Measurements and analytical data on treated and control plants are presented.
Saprophytic behaviour of Cephalosporium maydis and C. acremonium
Authors: SABET K. A. , SAMRA A. S. , MANSOUR I. M.
Published: February 2008

The competitive saprophytic ability (CSA) of Cephalasporium maydis was smaller at 30 d̀C when measured by the agar‐plate modification than by the original Cambridge method. The agar‐plate method suggested that C. maydis was a less competitive saprophyte than C. acremonium although both were low in CSA.

C. acremonium grows and sporulates well on organic and synthetic media. C. maydis grows faster but is more exacting nutritionally and is less able to decompose cellulose or maize straw than C. acremonium. Neither fungus produced pectolytic culture filtrates and both were susceptible to antibiotics produced by soil micro‐organisms.

C. maydis survived on maize straw much longer than C. acremonium. In field soils C. maydis colonized and survived in supplemented wheat bran poorly and not below the top 20 cm of soil.
Barley segregates resistant and susceptible to the cereal cyst‐nematode (Heterodera avenae Woll.)
Authors: WILLIAMS T. D.
Published: February 2008

In the first year of this experiment both nematode‐resistant and susceptible segregates of spring barley were equally invaded by Heterodera avenae larvae, but few females developed in the roots of the resistant plants and numbers of eggs in the soil were fewer after the resistant crop. In the second year, a commercial, nematode‐susceptible barley crop yielded significantly more grain following the resistant segregate. The resistant segregate, derived from Hordeum pallidum var 191, suppresses the development of Heterodera avenae pathotypes 1 and 2 [British nomenclature] and should be useful in areas where these pathotypes predominate.
Grain yield and incidence of take‐all (Ophiobolus graminis Sacc.) in wheat grown in different crop sequences
Authors: SLOPE D. B. , ETHERIDGE JUDITH
Published: February 2008

The yield of wheat and the incidence of take‐all were measured in crops grown in six different 4‐year sequences, repeated in 3 successive years. The first crop of winter wheat grown after oats or beans yielded 13–23 cwt/acre (1632–2887 kg/ha) more grain than wheat after wheat or barley. Spring wheat after oats yielded 2–5 cwt/acre (250–625 kg/ha) more than spring wheat after wheat. The smaller yields of wheat after wheat or barley were caused mostly by greater prevalence of take‐all. Regression analysis indicates that each 1 % increase in straws with take‐all decreased yield of winter wheat by 0·6%. Take‐all was more prevalent in the second and third successive wheat crops after oats than in the fourth crop.
Perennation of Alternaria longipes and the early stages of its development on tobacco
Authors: NORSE D. , WHEELER B. E. J.
Published: February 2008

Alternaria longipes (Ell. &Ev.) Mason survived on autoclaved maize stems for 6 months without losing its pathogenicity, but rapidly lost viability on non‐autoclaved stems and could not be re‐isolated 4 months after inoculation. In laboratory tests it infected both living and dead maize leaves. Some Alternaria isolates from non‐solanaceous hosts infected tobacco leaves kept at high humidities for 10 days after inoculation, but not when this incubation period was reduced to 48 h. In the field, perennation on plants other than tobacco is unlikely to be important as a source of inoculum. Pathogenicity of Alternaria isolates was maintained from one season to the next when stored as conidia in sterile soil, or as dried, infected tobacco leaves; some isolates maintained on agar slopes under oil were still pathogenic after 5 years.

Alternaria conidia collected from the surface of tobacco seedlings, and isolates from apparently healthy seedling leaves were pathogenic to mature tobacco. In the field conidia were detected on tobacco leaves soon after these emerged, and epiphytic colonies were occasionally found well in advance of symptoms. Many latent infections were also detected up to 5 weeks in advance of symptoms. Visual development of latent infections closely coincided with the end of leaf expansion.
Control of coffee berry disease*
Authors: GRIFFITHS ELLIS , GIBBS J. N. , WALLER J. M.
Published: February 2008

Field experiments comparing six spraying programmes and two fungicides for control of coffee berry disease were carried out at three sites during 1968. These established that protection of the crop by sprays applied throughout the long rains (February–July) gave the best control and increased yields threefold. Early season spray programmes, which reduced the sporulating capacity of the pathogen in coffee twigs, but which ceased before the end of the rainy season, gave no disease control in the late crop (harvested October‐December) and yields were less than in unsprayed controls. All programmes which gave protection at the onset of the rains gave some disease control in the early crop (harvested June‐August). Captafol (‘Ortho‐Difolatan’ 80 WP) was better than a 50% copper formulation (‘Perenox’).

Conditions suitable for infection, as determined from meteorological records, occurred frequently during both rainy seasons. Estimates of sporulating capacity and data from spore trappings showed that although inoculum from the bark might initiate an epidemic, subsequent disease progress was more dependent upon spores derived from diseased berries; these accounted for most of the inoculum dispersed during the greater part of the season. Removal of the early crop, which was very small, had no detectable effect on disease in the late crop.

Although losses were greatest with early season spray programmes, these did nevertheless delay the onset of the epidemic. However, the subsequent rate of disease increase was greatest and ‘scab’ lesion formation least in these treatments. ‘Scab’ lesions were most abundant in those treatments which caused least delay; in unsprayed coffee, it appeared that early exposure to infection resulted in ‘scab’ lesion formation which subsequently retarded the rate of disease progress. Tree height was positively correlated with disease incidence, but there was little effect of tree aspect. Crop density had a small effect on disease incidence within branches.
Effect of altitude on the distribution of the fungus causing coffee berry disease in Kenya*
Authors: MULINGE S. K.
Published: February 2008

Investigations in 1968 and 1969 showed that the relative abundance of the four main strains of Colletotrichum coffeanum (CBD, ccp, cca and cent (Gibbs, 1969)) in the bark of coffee trees varied with altitude. The CBD and ccp strains increased substantially with altitude; the cca strain also increased but to a smaller extent. The cent strain decreased with increasing altitude.

It is considered that the greater abundance of the CBD strain at the higher altitudes contributes to the greater severity of coffee berry disease at these locations.
Comparison of fungicides for control of leaf spot (Septoria apiicola) of celery
Authors: RYAN E. W. , KAVANAGH T.
Published: February 2008

Of twenty‐one fungicides tested at recommended rates of application for their effectiveness in controlling leaf spot of celery grown in Ireland on peat and on a clay‐loam soil, three formulations containing fentin acetate with maneb and formulations of fentin hydroxide and fentin chloride were most effective. Benomyl was superior to the other non‐tin fungicides tested and, at moderate disease levels, it resulted in marketable yields of celery equal to those recorded after treatment with the organotin compounds. Generally, the organotin compounds and benomyl were followed in descending order of effectiveness by copper oxychloride, captafol, Daconil 2787 and maneb. None of the fungicides tested in the three seasons caused visible symptoms of phytotoxicity and, on disease‐free celery in 1969, none had a significant effect on yield.
A side effect of chlorthiamid and dichlobenil herbicides
Authors: LEACH R. W. A. , BIDDINGTON N. L. , VERLOOP A. , NIMMO W. B.
Published: February 2008

2,6‐Dichlorobenzamide (BAM) induced leaf margin chlorosis (LMC) on the leaves of kale seedlings and apple trees when applied to the roots. The leaf symptoms were similar to those sometimes seen after use of the herbicides chlorthiamid and dichlobenil. BAM was deposited mainly in the margin of the leaf to which BAM was transported via the transpiration stream. BAM appeared to be the causative agent of chlorosis although hydroxy derivatives of BAM were also present in the leaf. Factors possibly responsible for the variations in the occurrence and in the intensity of LMC are discussed.
Spore discharge in Entomophthora grylli
Authors: PADY S. M. , KRAMER C. L. , LONG D. L. , McBRIDE T. D.
Published: February 2008

Entomophthora grylli Fres. has been found on larvae of Bradysia (Sciaridae, Diptera) on wood in Kansas State University greenhouses since November 1967. Infected larvae crawled to an exposed site in the night and by morning spores of E. grylli were being discharged. In the greenhouse and under controlled environments spore discharge showed a marked periodicity; spore discharge occurred in the light with peaks in the first 1–4 h; discharge then gradually declined but extended into the dark. On the second and third days peaks occurred in the light but were progressively smaller. In a greenhouse under fluctuating conditions twin peaks occurred at 10·00 and 22·00; in a growth chamber, at constant 21° C. 90% r.h., alternating 12 h light and dark periods, spore discharge was similar, with maximum numbers about 21/2 h after the onset of the photo‐period. In continuous dark and continuous light no endogenous pattern was evident. Temperature range for spore discharge was 2–28·, with optimum at 15·. Decreasing humidities resulted in decreased spore production and cessation of discharge below 40% r.h.
Some factors affecting the relative ability of two strains of Puccinia graminis tritici to survive when mixed
Authors: OGLE HELEN J. , BROWN J. F.
Published: February 2008

The process of infection by strains 21 Anz‐2, 7 and 21 Anz‐2, 3, 7 of Puccinia graminis tritici was quantitatively investigated to determine whether differences existed between them at any stage of the infection process and whether any such differences were related to the relative survival ability of the two strains in mixtures. The frequency of urediospore germination, the frequency of formation of appressoria, the period between inoculation and the eruption of uredia, the proportion of infection courts developing into uredia, and the visible characteristics of the uredia, did not differ between the two strains. However, penetration occurred more frequently from appressoria of strain 21 Anz‐2, 3, 7 than from those of strain 21 Anz‐2, 7. Uredia of strain 21 Anz‐2,3, 7 increased more rapidly in size than did those of 21 Anz‐2,7 and were ultimately larger in area. Similarly, more urediospores were produced per uredium by strain 21 Anz‐2, 3, 7 than by 21 Anz‐2, 7. It is suggested that these differences in frequency of penetration and in number of urediospores per uredium could account, at least in part, for the difference in relative survival ability between the two strains.
Influence of weed hosts on the ecology of Verticillium dahliae in newly cultivated areas of the Namoi Valley, New South Wales
Authors: EVANS G.
Published: February 2008

The evidence suggests that Verticillium dahliae is not indigenous to the Namoi Valley, but was introduced, probably in weed seed, and then increased on the natural dicotylendonous weeds, from which it spread to introduced crops such as cotton. V. dahliae could have been introduced and disseminated as microsclerotia, which are plentiful in the woody fruits of noogoora burr (Xanthium pungens) and Bathurst burr (Xanthium spinosuni) and in achenes of saffron thistle (Carthamus lanatus). V. dahliae was isolated from the stem and tap root of twenty‐six of fifty‐four species of weeds growing in naturally infested soils. It was not isolated from four species recorded as hosts elsewhere. Fifteen native or introduced weed species are newly recorded hosts. V. dahliae also colonized the roots of many wilt‐immune species, but died on the roots of most plants without producing microsclerotia. The only wilt‐immune plants in which microsclerotia formed in the roots were fat hen (Chenopodium album), red root (Amaranihus macrocarpus) and Canadian flea‐bane (Erigeron canadensis) but these are reported as hosts elsewhere.
Effect of an organo ‐ mercurial fungicide, chlormequat and decenylsuccinic acid on frost hardiness and seedling diseases of oats
Authors: RAWLINSON C. J.
Published: February 2008

Treating oat seeds of ten cultivars with an organo‐mercurial fungicide (Ceresan) and a dust formulation of the growth regulator chlormequat (2% a.i.) increased survival of seedlings growing under natural and simulated winter conditions. Treatment increased frost hardiness in less‐hardy cultivars, increased soluble sugars in stem base tissues and protected them from attack by soil fungi. It also increased root length in some cultivars but did not affect leaf area. Foliar applications of 10‐3m decenylsuccinic acid did not increase frost hardiness and also increased disease on stem base tissues. The possibility that sugar concentration may influence frost‐ and disease‐resistance of seedlings is discussed.
Quantitative studies of the post‐penetration phase of infection by Puccinia graminis tritici
Authors: OGLE HELEN J. , BROWN J. F.
Published: February 2008

Data obtained during the first 120 h after several resistant and susceptible varieties of wheat and some non‐host species were inoculated with uredio‐spores of Puccinia graminis tritici provided further evidence in support of the suggestion that hypersensitive necrosis is a consequence, and not the cause, of resistance. No evidence was obtained that individual genes for stem‐rust resistance specifically influenced colony growth or the histological changes that occurred during infection. However, combinations of major resistance genes or the presence of minor genes for resistance apparently did affect colony growth and hypersensitive cell collapse. Three groups of varieties – resistant, intermediate and susceptible – were distinguished on the basis of colony growth and the amount and proportion of necrotic tissue associated with colony development. The boundary between the intermediate and susceptible groups was not as distinct as that between the intermediate and resistant groups.
A survey of Ribes species for aphid resistance
Authors: KEEP ELIZABETH , BRIGGS J. B.
Published: February 2008

Field surveys from 1967 to 1970 of a Ribes species collection comprising ninety‐five plants representing fifty‐six species and fourteen sections of the genus, revealed moderate or severe aphid infestations as follows: Hyperomyzus lactucae (L.) on ten species included in five sections; H. pallidus H.R.L. ten species, two sections; Nasonovia ribisnigri (Mosley) twenty‐eight species, seven sections; Aphis grossulariae Kltb. twenty‐two species, ten sections; Cryptomyzus ribis (L.) four species, two sections; C. korschelti Börner three species, two sections.

Cut shoot tests suggested that c. 50% of sixty‐three field‐resistant accessions were tissue‐susceptible to H. lactucae, and about 70% of fifteen field‐resistant types were tissue‐susceptible to N. ribisnigri. Possible field escape mechanisms are discussed.

In breeding black‐currants resistant to H. lactucae and gooseberries resistant to N. ribisnigri, the donors R. sanguineum and R. cereum, and R. roezlii, respectively, were chosen for their high field and tissue resistance and for the known, or expected, fertility of their F1 hybrids with black‐currant and gooseberry.
Seasonal changes in aphid populations on Brussels sprouts
Authors: DUNN J. A. , KEMPTON D. P. H.
Published: February 2008

Populations of Brevicoryne brassicae (L.) and Myzus persicae (Sulz.) were assessed weekly on Brussels sprouts at Wellesbourne, from July onwards in each of 3 years. A peak of B. brassicae numbers occurred every year about the end of July, and in 1968 and 1970 this was larger than the September peak. Some alates were produced in the generation born to the June immigrants and the dispersal of those produced at the end of July consistently brought a decline in B. brassicae populations in early August. In 1968 and 1970, however, outbreaks of entomogenous fungi which followed rain, added considerably to this decline. Records of predators and parasites indicated that these natural enemies had only a minor effect on aphid numbers. M. persicae colonized sprouts slightly earlier than B. brassicae; in 1969 and 1970 its numbers in July were low and some persisted after the first week of August in 1968 only. In each year the first eggs of B. brassicae were laid at the beginning of October, but viviparae were still numerous for a further 7 to 10 weeks.
The infection of apples, cv. Bramley's Seedling, by Nectria galligena Bres
Authors: SWINBURNE T. R.
Published: February 2008

In laborator experiments germinating conidia penetrated leticels and wounds but not the intact surfaces of apples. Date of harvest had no significant effect on the numbers of apples infected with Nectria galligena but the earliest picks rotted first in barn store. Inoculations of unpicked apples resulted in small arrested lesions which only developed into progressive rots after a considerable period in store. Rots developed mosy quickly from inoculations made between mid‐August and mid‐September. The size of rot increased with spore number and many inoculations with 10–100 conidia remained as arrested lesions.

Arrested lesions developed 10–15 days after unripe apples were inoculated and consisted of a zone of fungal colonization surrounded by suberized, necrotic cells in which compounds toxic to both N. galligena and Penicillium expansum were detected. No antifungal compounds were found in progressive rots to mature apples or in healthy apples of any age. Antifungal activity, measured by inhibition of P. expansum, was greatest 15–20 days from inoculation of unripe apples with N. galligena but decreased after a total of 35 days incubation at 20 d̀ C. Much less antifungal activity was produced in ripe or desert apples.
The resistance of spores of resistant strains of Botrytis cinerea to quintozene, tecnazene and dicloran
Authors: ESURUOSO O. F. , WOOD R. K. S.
Published: February 2008

Spores formed by strains of Botrytis cinerea resistant to quintozene, tecnazene, or dicloran did not always produce resistant colonies when grown on agar in the presence of these fungicides.

Only about one half of spores produced by fungicide‐vapour‐resistant strains in the absence of fungicides gave resistant colonies whereas all spores produced by the same strains in the presence of fungicides formed resistant colonies on agar.

Some spores produced by resistant strains that had developed on agar containing the fungicides were not viable, but those that were always gave resistant colonies on agar.
Factors affecting the development of spraing in potato tubers infected with potato mop‐top virus
Authors: HARRISON B. D. , JONES R. A. C.
Published: February 2008

A larger proportion of tubers of Arran Pilot potato growing at the surface of soil infested with potato mop‐top virus (PMTV) showed spraing symptoms (brown rings) at harvest than of tubers from below the surface. Infected tubers with or without spraing developed a spraing ring when stored in darkness, first for 1–2 wk at 18 d̀C and then for 1–2 wk at any constant temperature between 5 and 13 d̀C. Only a faint surface ring developed when either of these periods was decreased to 1 day; 4‐day periods were needed to induce distinct symptoms. Internal tuber symptoms developed more slowly than surface symptoms, and their formation was favoured by cutting the tubers in half. Additional pigmented surface rings were produced outside the first ring by successive cycles of treatment at 18 and 9d̀. Spraing did not develop when the first stage of treatment was at 22–25d̀, when the tubers were kept first at 10d̀ and then at 5d̀, when the treatment at 5–13d̀ preceded that at 18d̀, or when the tubers were kept at constant temperatures ranging from 5 to 25d̀.

When tubers of six potato varieties were grown in PMTV‐infested soil and then stored at temperatures designed to induce symptoms, the varieties known to be the most susceptible in the field were those which had the greatest tendency to develop spraing during storage. When infected tubers were exposed to light, typical spraing symptoms were not induced, but greening of the tuber surface was much delayed in localized ring‐shaped areas, so that pale weals appeared.

Spraing symptoms were produced, in favourable conditions, by the reaction of cells at the periphery of the PMTV‐invaded zone. Internal spraing did not prevent PMTV invading tissue outside the brown arcs; its rate of spread was about 10 μm/h at 14–18d̀.
Studies on the relation between density of Longidorus elongatus and growth of sugar beet, with supplementary observations on Trichodorus spp
Authors: BROWN E. B. , SYKES G. B.
Published: February 2008

Longidorus elongatus attacks sugar beet on light sandy soils in the West Midlands. Severely damaged plants may die or recover, producing fanged roots. Up to 335 L. elongatus/200 g of soil were found around attacked seedling plants and were often visible to the unaided eye on the roots of freshly lifted plants.

Five experiments were made and regressions computed of yield of beet, total numbers of plants and numbers of normal and fanged beet on L. elongatus numbers. Between 24% and 50% of roots per 100 L. elongatus/ 200 g were killed or became fanged. Corresponding figures for loss of plant were between 7.5% and 33%.

Estimated loss of yield varied between 0.8 and 7.3 tons (2.0–18.3 t/ha)/acre/100 L. elongatus/200 g, the former where the potential yield was high and the latter where poor growing conditions hindered recovery.

Large numbers of Trichodorus occurred in two trial sites and there is some evidence of competition between the two genera. Significant negative regressions for Trichodorus spp. were obtained in one trial suggesting a loss of 12% total and 17% normal roots per 100 Trichodorus spp./200 g.