bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of responses of resistant and of susceptible tomato plants to Verticillium infection
Authors: SINHA A. K. , WOOD R. K. S.
Published: February 2008

Comparative studies were made of the responses of resistant and of susceptible Gem tomato plants to infection by Verticillium albo‐atrum. When inoculated through roots, there were striking differences in their responses. In susceptible plants, the foliar symptoms and amount of mycelium in the stem increased rapidly for some time. Then the mycelium started to disappear from the stem; this was accompanied by a check to the normal progress of symptoms, and by the formation of tyloses. In resistant plants, a limited invasion of the root and lower stem was accompanied by rapid and extensive tylosis. The mycelium soon disappeared from the stem and the plant then recovered from the initially mild symptoms. There was an inverse relationship between the amount of mycelium and the extent of tylosis in infected plants. The growth of susceptible plants was markedly reduced by infection. Total leaf area was much less because the newly produced leaves did not expand normally. The root system in infected plants was smaller because there were many fewer tertiary roots. In resistant plants infection stimulated growth.

Tomato cuttings inoculated with conidia reacted similarly to root‐inoculated plants. Hyphae grew well in the vascular system of susceptible cuttings whereas in resistant cuttings the pathogen started to grow but soon disappeared.

Detached leaves of susceptible plants, inoculated through cut ends, wilted more than did leaves from resistant plants. It is suggested that resistance is mainly of the active type that develops after infection.
The nature and causes of annual fluctuations in numbers of Aphis fabae Scop. on field beans (Vicia faba)
Authors: WAY M. J.
Published: February 2008

Experiments for nine successive years showed that Aphis fabae Scop. populations on mid‐March‐sown field beans were either large with peak densities between late June and mid‐July or very small with peak densities in early August. It is concluded that the largest populations develop when many plants have been colonized by primary migrants from Euonymus europaeus and temperature and radiation are above average during June and early July, as in the year 1957. Cold, dull weather slows multiplication and decreases the size of the peak population even when there is a large initial colonization, as in 1954. The peak population may also be less than predicted from the initial colonization when natural enemies are exceptionally abundant in early June, as in the year 1960. Yield losses of mid‐March‐sown crops in years of large A. fabae populations ranged from 53 % in 1954 (peak population of 1260 aphids per plant) to 100% in 1957 (6920 aphids per plant).

Small summer populations with peak densities of about 0·2–85 aphids per plant developed on mid‐March‐sown plots in years when fewer than about 6% of the plants were colonized by primary migrants. Yield losses ranged from 6·3–13·6%.

Three years' experiments indicated that crops sown in late April or May are relatively lightly infested in years when large populations develop on mid‐March‐sown crops. Conversely, they may be relatively heavily infested when the populations on these crops are small, as in 1955 when temperatures and sunshine during July and early August were above average.

Small and large early summer populations tend to alternate in successive years. The alternation is upset by hot, sunny weather during July and August, and perhaps September and October, which compresses the population cycle Thus the large and small populations expected from this alternation in 1956 and 1960 developed instead during exceptionally fine weather in late summer 1955 and 1959, converting 1956 and 1960 to years of small and large populations respectively.
Factors affecting the toxicity of diazinon to Musca domestica L
Authors: GWIAZDA MARIA , LORD K. A.
Published: February 2008

Processes affecting the toxicity of diazinon to a susceptible and a resistant strain of houseflies were examined.

More evidence was obtained to show that slower penetration of diazinon through the integument of resistant flies is a cause of resistance.

Small amounts of two decomposition products were found in both strains. The decomposition mechanisms, in these strains were differently distributed and, although detoxication of diazinon in the two strains is quantitatively similar and small, it may contribute to resistance.

Traces of diazoxon were detected when diazinon was incubated with tissue extracts of either strain.

Tissue extracts of resistant, but not of susceptible, flies decomposed significant amounts of diazinon in 1 hr. and the ability to decompose diazoxon seems to be an important cause of resistance.

Tissues of both strains sorbed diazinon from aqueous solution similarly; the quantities sorbed were large and suggest that sorption may increase the amount of poison needed inside the insects to kill, by between five and forty times.
The role of water in the spread of Phytophthora infestans in the potato crop
Authors: LACEY J.
Published: February 2008

During falls of rain before 5% of the haulm was destroyed by blight, most rain water was deposited on soil at the bottom of the ridge, and least at the top in crops of King Edward, Majestic, and Up‐to‐Date potatoes. Afterwards less water was trapped half way up the side of the ridge than above or below. Water was also channelled down the stems and, while these were upright, was deposited in the channel often formed around the stem bases by wind movement. Fewer than 500 sporangia per ml. were seen in water collected when blight was present in the crop.

Growing tubers of Ulster Ensign and King Edward, inoculated with P. infestans, infected healthy tubers less than 1–3 cm. away, when the soil water content was greater than 20%, and sporulation on the inoculated tubers was maximal. Similarly inoculated Up‐to‐Date and Majestic tubers sporulated less abundantly and failed to infect healthy tubers.

Sporulation also occurred on inoculated seed tubers, although infection of the haulm from these tubers could not be confirmed. Water movement from the seed tuber region to the furrows may occur under suitable conditions.
The toxicity of some soil insecticides to carabid predators of the cabbage root fly (Erioischia brassicae (Bouché))
Authors: MOWAT D. J. , COAKER T. H.
Published: February 2008

In laboratory tests concentrations of dieldrin in soil, below that required to control cabbage root fly, were found to be toxic to several species of carabid beetles which prey on the immature stages of this pest. These results confirm previous findings from field experiments that dieldrin residues in soil can, by reducing the populations of predaceous beetles, increase the survival of the cabbage root fly and the subsequent crop damage caused. The toxicity of selected organophosphorus insecticides to these beneficial insects was studied in soils of different moisture content. Thionazin was found to be highly toxic at all moisture levels as was diazinon in moist soil. Chlorfenvinphos and azinphos‐methyl and, in dry soil diazinon, were very much less toxic.
A comparison of cereal root eelworm resistant and susceptible spring barley genotypes at two sites
Authors: COTTEN JOHN
Published: February 2008

A comparison between otherwise identical cereal root eelworm resistant and susceptible spring barley lines was made on two sites, one lightly infested the other heavily infested with the nematode. On the lightly infested site, the grain yields of the resistant and susceptible lines did not differ, but on the heavily infested site, the resistant lines out‐yielded the susceptible lines by 20%.

A similar comparison was also made between five reputedly eelworm‐resistant spring‐barley genotypes and three cultivars known to be susceptible. On the lightly infested site, the three susceptible cultivars out‐yielded all other genotypes, while on the heavily infested site they were out‐yielded by all other genotypes except one.

Development of the nematode was compared in resistant and susceptible genotypes. Although the nematode was as numerous in resistant genotypes as in susceptible genotypes, either invasion or development of the nematode was retarded in resistant genotypes. Although not conclusive, there was evidence that the male was less retarded in development than the female, which was rarely found in the adult form on resistant plants.
The isolation and identification of rhubarb viruses occurring in Britain
Authors: TOMLINSON J. A. , WALKEY D. G. A.
Published: February 2008

Virus‐like symptoms were common in British crops of rhubarb. All plants tested of the three main varieties, ‘Timperley Early’, ‘Prince Albert’ and ‘Victoria’, were virus‐infected. Turnip mosaic virus and a severe isolate of arabis mosaic virus (AMV) were obtained from ‘Timperley Early’; and ‘Prince Albert’ contained turnip mosaic virus, cherry leaf roll virus (CLRV), a mild isolate of AMV and, infrequently, cucumber mosaic virus (CMV). The main commercial variety ‘Victoria’ contained turnip mosaic virus, CLRV, a mild isolate of AMV and, infrequently, strawberry latent ringspot virus (SLRV). All the viruses were identified serologically. The rhubarb isolates did not differ markedly from other isolates of these viruses in herbaceous host reactions, properties in vitro or particle size and shape. A rhubarb isolate of CLRV was distinguished serologically from a cherry isolate of the virus.

Turnip mosaic virus, CLRV and SLRV, were transmitted with difficulty, but AMV isolates were readily transmitted by mechanical inoculation. Turnip mosaic virus was also transmitted to rhubarb by Myzus persicae and Aphis fabae. CLRV was transmitted in 6–8% of the seed of infected ‘Prince Albert’ and ‘Victoria’ rhubarb and in 72% of the seed of infected Chenopodium amaranticolor. Mild isolates of AMV were also transmitted in 10–24% of the seed of infected ‘Prince Albert’ and ‘Victoria’ plants.
The production of virus‐free clones of some British potato varieties
Authors: KASSANIS B. , VARMA ANUPAM
Published: February 2008

Virus‐free clones of some British potato varieties, of which all commercial stocks are infected, were obtained by culturing apical meristems of sprouts on tubers. The variety Golden Wonder was freed from potato virus A, Arran Comet from potato virus X, and Epicure, Orion and Sharpe's Express from potato virus S. Of the 196 meristems cultured, forty‐one (21%) grew and of these twenty developed into plants, of which nineteen were virus‐free. More of the excised meristems grew when the first leaf primordium was included than when not, and its inclusion seemed not to increase the chances of the progeny being infected.
Studies with 3,5‐diiodo‐4‐hydroxybenzonitrile (ioxynil) and related compounds in soils and plants
Authors: ZAKI M. A. , TAYLOR H. F. , WAIN R. L.
Published: February 2008

The inactivation of the herbicide ioxynil by contact with soil has been investigated. Shaking solutions of the sodium salt with acid soils led to a precipitation of the herbicide. With alkaline soils, a small amount of ioxynil became adsorbed on the soil particles. With unsterilized soils, hydrolysis to 3,5‐diiodo‐4‐hydroxybenzoic acid occurred, with 3,5‐diiodo‐4‐hydroxy‐benzamide as an intermediate product. Liberation of iodide ion in this system was also demonstrated.

The phytotoxicity of ioxynil is enhanced by exposure of treated plants to light. The reduction in chlorophyll level of bean leaf tissue treated with ioxynil and other dihalogenohydroxybenzonitriles when exposed to light has been determined. Evidence is presented showing that although ioxynil is poorly translocated in the dwarf bean plant, its degradation products appear in the shoots of these plants after the herbicide has been supplied through the roots.
Factors affecting male probing activity of the red bollworm Diparopsis castanea (Hmps.) in relation to sterility induced by tris(1 ‐aziridinyl) phosphine oxide (tepa)
Authors: CAMPION D. G. , OUTRAM I.
Published: February 2008

Assuming that the sex attractant of the female red bollworm, Diparopsis castanea (Hmps.), can be isolated, it might be used at bait stations in combination with chemosterilants for the control of this insect. To ensure success, it is essential that male moths attracted to the bait station should pick up an effective dose of chemosterilant either by brief contact with, or by momentary probing on, chemosterilant‐treated surfaces.

In Rhodesia, during the dry season, up to 90 % of the moths tested probed on water after 3 days, while 80% probed on 10 %‐D‐glucose after 2 days. In a laboratory with controlled humidity, 70 % of the moths probed after 18 h at 0–10% R.H.; and 10% probed after 18 h at 40% R.H. The average amount of liquid imbibed by individual moths varied from 15·5 μl after 18 h at 0% R.H. to 7·2 μl after 18 h at 40% R.H. It was estimated, and later confirmed, that thirsted moths probing on a 0·1 % aqueous solution of tris (1‐aziridinyl) phosphine oxide (tepa) would take up the equivalent of a sterilizing dose. The treated moths were consistently sterilized with no adverse effects on mating frequency, longevity or competitiveness.

As both sexes were found to be sexually mature on emergence, it is probable that little dispersion of the newly emerged adult population occurs before the first mating.
The adaptation of tomato mosaic virus to resistant tomato plants
Authors: DAWSON J. R. O.
Published: February 2008

Tomato mosaic virus derived from susceptible tomato plants (the standard virus) was cultured in resistant plants. Sap from non‐inoculated leaves of resistant tomato plants infected with virus from the resistant host was more infective and contained more virus particles than leaf sap of resistant plants infected with the standard virus. Leaves of resistant tomatoes infected with virus from the resistant host also showed more obvious symptoms. Susceptible plants infected with virus from resistant plants not only showed fewer symptoms than when infected with standard virus, but samples were less infective and contained less virus up to 26 weeks, when values for infectivity were similar.

This modification in activity was not reversible and was obtained with two lines of tomato having different types of resistance. Passage of virus from resistant plants through susceptible plants did not impair its ability to infect resistant plants.
Epidemiology of stamen blight of raspberry
Authors: DICKENS J. S. W.
Published: February 2008

Stamen blight, caused by Hapalosphaeria deformans Syd., is a disease of a number of Rubus species. It is widespread on commercial raspberries in Angus and east Perthshire. Evidence indicates that spread is from diseased flowers to the axillary buds of young canes during the summer and entry into these buds is complete by autumn, after which it is unlikely that the pathogen can be reached even by an eradicant fungicide. Attempts to infect young canes artificially, however, have failed. Rain splash appears to be of considerable importance in dispersal, but some spread by wind and pollinating insects could occur. Possible control measures are discussed and the importance of planting canes from spawn beds, where no flowering canes are kept, is emphasized.
Emergence and phytopathological properties of a new strain of Claviceps purpurea (Fr.) Tul. on rye
Authors: MANTLE P. G.
Published: February 2008

The emergence of a new stable strain of Claviceps purpurea is described. The strain formed the sphacelial stage very weakly on rye, and was unlikely therefore to be able to initiate an epidemic under field conditions, but the sclerotia contained chanoclavine as the major alkaloid in contrast to the ergotamine component of the parent strain. Isolates of C. purpurea derived from ryegrass ergots were also shown to parasitize rye.
The development of Botrytis cinerea on cut flowers of carnation
Authors: EDNEY K. L.
Published: February 2008

Enclosing carnation blooms in polythene increased rotting associated with naturally occurring Botrytis infections and accelerated the rate of conidia development when flowers were artificially inoculated before being stored at 1·7 °C. Petal infections were observed 16 and 48 h after inoculation and incubation at 18·3 and 1·7 °C respectively. The products of exosmosis from petals kept at 18·3 °C for 7 days stimulated germination of B. cinerea conidia. Slight pectic enzyme activity was detected in a liquid medium, derived from carnation petals, after incubating B. cinerea cultures at 18·3 °C for 6 days. Although cultures of Botrytis evolved virtually no ethylene, the surge of ethylene produced by uncontaminated ageing flowers occurred sooner after inoculation. A spray containing 1·2% a.i. of 2‐aminobutane controlled rotting but damaged flowers.
The role of wounds in the infection of oranges by Penicillium digitatum Sacc
Authors: KAVANAGH J. A. , WOOD R. K. S.
Published: February 2008

Inocula of spores of Penicillium digitatum in water applied to apparently uninjured skin of oranges do not cause lesions to develop. Addition of citric acid, orange juice, or various extracts of rind had little effect on susceptibility to infection.

When spores in water are applied to wounds made between oil vesicles, lesions develop only from wounds that penetrate deeply into the albedo. The flavedo of most oranges seems to be resistant to infection even when damaged, but in a few consignments it showed much less resistance. Increasing the number of conidia in the inoculum caused more lesions to develop but some fruits developed lesions from inocula containing very few spores. The method and timing of spore application to wounds had a considerable effect on the incidence of lesions; emanations from infected fruit had no effect.

Lesions developed more rapidly and readily when suspensions of spores in water were applied to wounds in the skin that damaged oil vesicles; wounds as shallow as 0–25 mm allowed lesions to develop.
Host range and variation in virulence of Mycosphaerella ligulicola
Authors: CHESTERS C. G. C. , BLAKEMAN J. P.
Published: February 2008

A soil‐borne inoculum of Mycosphaerella ligulicola was found to be mildly pathogenic to leaves or stems of globe artichoke, rudbeckia, zinnia, sunflower and dahlia, but severely pathogenic to lettuce. This is the first report of an infection by this fungus of plants other than chrysanthemum or pyrethrum. It was found that, with successive passages of the fungus through lettuce and chrysanthemum respectively, an increase in virulence to these hosts occurred. After a single passage through lettuce a reduction in virulence to chrysanthemum resulted, but with further passages through lettuce there was no further reduction in virulence to chrysanthemum.
Effect of the timing of insecticide applications on infestation by Cavariella aegopodii Scop, on carrots*
Authors: DUNN J. A. , KEMPTON D. P. H.
Published: February 2008

The residual effectiveness of demeton‐methyl and menazon sprays applied to carrot plants was compared in the laboratory using Cavariella aegopodii Scop, and more observations were made in the field, where applications of both insecticides were timed in relation to the observed immigration period of the aphid. The relative field performances confirmed those found in the laboratory and, as the aphid population control exercised was inversely proportional to the amount of alate immigration occurring after the sprays had become ineffective, the more persistent menazon was progressively superior to demeton‐methyl the nearer they were applied to the beginning of immigration.

A single spray application of either material towards the end of immigration gave a similar overall control of aphid numbers to that given by disulfoton granules applied at sowing time.

To minimize colonization, two spray applications spanning the immigration peak were required and, with 2 weeks between the demeton‐methyl sprays and 3 between those of menazon, the highest degree of control was obtained when the first application was made 7–10 days after the beginning of immigration.
Studies on a virus causing stem grooving and graft‐union abnormalities in Virginia Crab apple*
Authors: de SEQUEIRA O. AMARO
Published: February 2008

A virus was transmitted from apple trees to Nicotiana glutinosa and Chenopodium spp. and back to a range of woody indicators in which it affected only Virginia Crab; symptoms were grooves in the xylem, and swelling and necrosis of the scion immediately above the union with the stock. The virus was distinct from that causing stem pitting in Virginia Crab, because although easily detectable in several apple varieties, it was not found in many trees infected with stem pitting virus.

The stem grooving virus has flexous particles 600–700 m/μ long, a heat inactivation point of 67 °C, a dilution end‐point of 10‐3 in N. glutinosa sap and remains infective for at least 2 days at 20 °C.
A relationship between leaf structure and growth potential in apple
Authors: BEAKBANE A. BERYL
Published: February 2008

The number of palisade mesophyll cells per unit area leaf lamina was related to the growth potential of apple rootstocks covering a wide range of vigour. The number of these cells per unit leaf surface depends on cell diameter, the number of layers of palisade, and the amount of intercellular airspace. In composite, grafted trees rootstock influence was observed on the leaf structure of scions of low, or intermediate, growth potential.
Germination of sclerotia of Sclerotium cepivorum Berk. under aseptic conditions
Authors: COLEY‐SMITH J. R. , KING J. E. , DICKINSON D. J. , HOLT R. W.
Published: February 2008

The response of sclerotia of Sclerotium cepivorum to a number of plant extracts and nutrient solutions was tested, aseptically, on agars, silica gels, filter paper discs, and on columns of soil. There was no specific response of sclerotia to extracts of Allium species in any of these experiments, whereas in unsterile soil consistently high levels of germination were obtained only with Allium extracts. It was shown that sclerotia are subject to the mycostatic influence of unsterile soil. With S. cepivorum soil mycostasis appears to be specifically reversed by Allium species or by water extracts made from them.
The effect of growth substances on Verticillium wilt of tomato plants
Authors: SINHA A. K. , WOOD R. K. S.
Published: February 2008

This paper describes the effects of a number of growth‐regulating substances on the development of disease in tomato plants caused by Verticillium albo‐atrum. Indole‐acetic acid usually reduced disease and also reduced the number of hyphae in the stem but it increased tylosis; low concentrations slightly stimulated disease development. Some control of disease was obtained by removing apical buds, and axillary shoots as they developed. When the apical bud alone was removed, developing axillary shoots sometimes wilted; this did not occur in plants with intact buds.

Gibberellic acid increased disease in susceptible plants and also induced symptoms in resistant plants. Maleic hydrazide greatly reduced growth of plants, made them more diseased and stimulated growth of the parasite in the vessels.

Of other growth‐regulating substances tested, 2,4,6‐trichlorophenoxy‐acetic acid, 2,3,5‐triiodobenzoic acid and 2,4‐dichlorophenoxyacetic acid increased disease at some concentrations and reduced it at others. Cycocel (2‐chloroethyl) trimethyl ammonium chloride and naphthaleneacetamide, gave good control of disease over a range of concentrations when applied to the soil in which plants were growing. Treatments which reduced disease also reduced the growth of the parasite in the shoot and stimulated the formation of tyloses.

Indole and 2,4‐dichloroanisole had some effect on disease development but this was much less than that induced by the other substances.
Population studies on the active stages of the black bean aphid, Aphis fabae Scop., on its winter host Euonymus europaeus L
Authors: WAY M. J. , BANKS C. J.
Published: February 2008

Autumn populations of Aphis fabae Scop, on the primary host Euonymus europaeus L. were little affected by natural enemies, most of which had begun to hibernate before the aphid populations developed.

The size of the population in spring was usually determined by the number of overwintering eggs on a bush. The fundatrices hatched about 3–6 weeks before natural enemies became common. The growth of large A. fabae populations was first halted by the effects of intra‐specinc competition, notably by the production and departure of emigrant alatae and by adult apterae reproducing more slowly. Later, natural enemies, especially Adalia 2‐punctata (L.), Syrphidae and the parasite Trioxys sp. (near angelicae), multiplied and accelerated the decline in the aphid populations, which usually disappeared in June leaving many immature natural enemies. Larval A. 2‐punctata began to eat parasitized aphids and cannibalized other larvae and pupae.

The small populations of A. fabae that develop from few overwintering eggs are at greater risk from natural enemies than are large ones. Intraspecific competition still slowed population increase, because most aphids remained crowded on the few originally colonized twigs. Such populations produced very few emigrant alatae before they were exterminated by the combination of T. angelicae with specific and non‐specific predators. Adult Cantharidae killed many of the aphids, especially in hedgerow habitats, where they were abundant.

Coccinellidae, Anthocoridae and syrphid larvae, and the adults of nonspecific predators, notably Cantharidae, prevented recolonization of E. europaeus throughout July and August. Leaves of E. europaeus may remain physiologically suitable for A. fabae throughout July but begin to deteriorate in August when A. fabae kept on them become less fecund.

Experiments using exclusion techniques provided evidence that natural enemies which attack A. fabae on E. europaeus and on summer hosts cause the common 2‐year cycle of aphid abundance.

Individual E. europaeus differ consistently in the extent to which they are colonized by A. fabae. Conditions are discussed that should govern the choice of E. europaeus bushes on which the A. fabae populations can be used as sensitive indicators of later crop infestations.
Hatching of the winter eggs of the fruit‐tree red spider mite (Panonychus ulmi (Koch))
Authors: LIGHT W. I. ST G. , JOHN MARGARET E. , GOULD H. J. , COGHILL K. J.
Published: February 2008

Observations on the hatching of winter eggs of Panonychus ulmi (Koch) from apple orchards in England over the 5 years 1962‐6 are described. Differences of 2–3 weeks between orchards in the date at which 50% hatch was reached were quite common and this was out of step with petal fall in the majority of orchards. There was a continuous range between early and late hatching populations and a tendency for the populations to hatch in the same order every year. In 1966 populations on Cox's Orange Pippin hatched earlier than those on Worcester Pearmain but the difference was unlikely to be of practical importance. Neither recording accumulated day degrees for populations hatched out‐of‐doors nor hatching in an incubator after chilling was considered to give a sufficiently reliable forecast of 50% hatch but observations in 1966 suggested that this might be predicted from the total eggs hatched in an incubator expressed as a percentage of total healthy eggs.
The control of strawberry‐seed beetle (Harpalus rufipes Deg.); with observations on the damage it causes and that by linnets (Carduelis cannabina cannabina (L.))
Authors: FRENCH N. , JOHN MARGARET E. , MORETON B. D.
Published: February 2008

In a laboratory trial, the previous diet of strawberry‐seed beetles influenced their choice of food. The beetles generally preferred crushed oats to chicken pellets or bran though they fed more often on ripe strawberries than on the other foods. Baits of crushed oats containing malathion and fenitrothion (each at 0·15% active ingredient) and 0·1% a.i. of aldrin were eaten when strawberries were also available. In field trials, beetle mortality ranged from about 30% in small enclosed plots to about 90% in large field plots. Malathion bait remained effective for 5–7 days under wet conditions and 10–12 days under dry. Fenitrothion and aldrin baits were effective for 2–3 weeks. Observations made after using fenitrothion baits suggest that they are not a danger to wild life. In a survey of forty‐seven commercial crops linnet damage was found in thirty‐five crops and seed‐beetle damage in three crops. Linnet damage was most severe in unstrawed maiden crops.
Some effects of spraying with thiabendazole on the susceptibility of sugar beet to yellowing viruses and on their vector, Myzus persicae (Sulz.)
Authors: RUSSELL G. E.
Published: February 2008

In a field experiment fewer sugar‐beet plants became infected with aphid‐transmitted yellowing viruses in plots that had been sprayed with solutions of thiabendazole lactate than in water‐sprayed plots, after exposure to natural infestation with aphids. Subsequent glasshouse tests showed that foliar sprays of o·o1 % thiabendazole lactate in water significantly reduced the proportion of inoculated sugar‐beet plants which became infected with beet yellows virus (BYV) or beet mild yellowing virus (BMYV) after inoculation with viruliferous Myzus persicae (Sulz.). This effect on virus transmission was not apparently due to a direct insecticidal action of thiabendazole, because adult aphids usually survived equally well on sprayed and unsprayed plants. Treatment of test plants with thiabendazole did not affect the transmission of beet mosaic virus to them by M. persicae. The fecundity of M. persicae was greatly reduced by transferring them to plants which had been sprayed with thiabendazole or by spraying them with thiabendazole before transfer to unsprayed plants. The fertility of adult Aphis fabae Scop, was also reduced by spraying with thiabendazole. The mechanisms whereby thiabendazole affected fecundity of aphids and transmission of viruses are not understood.
The relationship between leaf blotch caused by Rhynchosporium secalis and losses in grain yield of spring barley
Authors: JAMES W. CLIVE , JENKINS J. E. E. , JEMMETT J. L.
Published: February 2008

Two methods were used to investigate the loss in grain yield associated with specific levels of leaf blotch. Yields from plots sprayed with fungicide were compared with those from unsprayed plots and yields of varieties of different susceptibility to the disease were compared with one another. A disease assessment key is presented, which was used to assess the percentage laminar area of the top two leaves affected by the disease. A linear relationship between disease on the upper two leaves and yield was established. Results from nine trials showed a consistent relationship between the disease level, at growth stage 11·1 (Feekes scale), and loss in yield. The loss in yield expressed as a percentage of the yield of an uninfected crop was equivalent to approximately two‐thirds of the percentage of the flag‐leaf area visibly infected, or one‐half of the infected area on the second leaf. The predicted loss in yield is the average of these two estimates.
Experiments using sterilized apple‐leaf discs to study the mode of action of urea in suppressing perithecia of Venturia inaequalis (Cke.) Wint.
Authors: ROSS R. G. , BURCHILL R. T.
Published: February 2008

Laboratory experiments using sterilized apple‐leaf discs showed that treatment of leaves with urea during the early stages of perithecial initiation induced a high nitrogen content of the leaves, which prevented further development of perithecia although mycelial growth was unaffected. Treatments applied at a later stage of fungal development inhibited both perithecial and mycelial growth.

Some of the bacteria isolated from urea‐treated leaves in the field restricted perithecial development, particularly when applied in the first month after inoculation with suspensions of conidia from sexually compatible strains of the fungus. One isolate, a Pseudomonas sp., was shown to be important in the decomposition of apple leaves.
Methods of measuring the prevalence of pathogenic fungi on potato tubers
Authors: HIDE G. A. , HIRST J. M. , SALT G. A.
Published: February 2008

Methods are described whereby the prevalence of pathogenic fungi on seed potato tubers can be measured quickly and quantitatively. Eye‐bearing plugs of tuber tissue, 8 mm diameter by 10 mm long, are excised, incubated over water at 15 °C for 5 days and then examined microscopically. The occurrence of fungi and macroscopic tuber symptoms are recorded directly on punched tape and tabulated by computer.
Freckle disease of banana in Hawaii caused by Phyllostictina musarum (Cke.) Petr
Authors: MEREDITH D. S.
Published: February 2008

‘Freckle’ (‘black‐spot’ disease) of bananas is common on leaves and fruit of Dwarf Cavendish and other varieties in Hawaii, especially after rainy periods. On fruit, symptoms may appear 2–4 weeks after the bunch has opened, and become more severe as maturity is approached. The disease is usually confined to older leaves on affected plants. Freckled tissue contains numerous pycnidia of Phyllostictina musarum and disease was experimentally induced by inoculating leaves and fruit with conidia of this fungus. This appears to be the first record of successful inoculation with P. musarum.

Conidia of P. musarum germinate after 3–6 h in a film of water on banana peel, appressoria being formed after 18–30 h. Penetration of the epidermis occurs 24–96 h after inoculation, and is brought about by an infection hypha which grows from the appressorium. The progressive increase in severity of freckle as fruit matures is due to repeated infection by further conidia of P. musarum, rather than to enlargement of original infections. Some banana clones, including Gros Michel, appear to be resistant to the fungus

Dispersal of P. musarum conidia immediately after discharge from the pycnidium is chiefly by rainwater and dew. Secondary infections contribute greatly to the total number of infections. Conidium dispersal by water often results in the development of characteristic patterns of spotting, chiefly in the form of streaks or circular areas, coinciding with the directions of movement of rainwater and dew. Large numbers of conidia of P. musarum are washed on to fruit in rainwater and dew running from diseased, overhead leaves.
Laboratory tests of fungicides against Peronospora parasitica (Pers. ex Fr.) Fr
Authors: CHANNON A. G. , FAULKNER) RUTH J. HAMPSON (née
Published: February 2008

Methods were investigated of culturing Peronospora parasitica on detached cotyledons in plastic box moist chambers in constant‐temperature cabinets. Light was essential and a temperature of 15 °C was most suitable for infection and survival of cotyledons. Using such cotyledons the protectant and eradicant actions of various fungicides against P. parasitica were compared with those of zineb. Captafol, Daconil 2787, dichlofluanid and propineb were markedly superior to zineb as protectants, being highly effective at 0·025 % a.i. None of these compounds (at 0·2 % a.i.) checked fungal development when applied 5 h after inoculation, during which time the fungus had penetrated the cotyledons, and it was concluded that the fungicides had thus no internal effect. Internal fungistasis was shown, however, by a maneb‐nickel sulphate fungicide and also by nickel sulphate. The latter (at 0·4% NiSO4.6H2O) gave some disease control when applied up to 72 h after inoculation and appeared to be translocated within the tissue of the cotyledon.
Effects of cultural treatments on the incidence of, and damage done by, tomato brown root rot
Authors: LAST F. T. , EBBEN MARION H. , ROTHWELL J. B. , JONES D. A. G.
Published: February 2008

In soils naturally infested with Pyrenochaeta lycopersici, which usually occurs as a grey sterile fungus (GSF), symptoms of brown root rot (BRR) developed sooner and more extensively in the second year of cropping than in the first. The amount of BRR attributable to corkiness increased as plants aged but, at comparable stages of cropping, decreased in the second and third seasons, an effect associated inversely with the severity of early GSF attack. The larger amount of corkiness, 33 compared with 18 %, on two batches of plants in 1965, each with 53 % end‐of‐season BRR, was also attributed to a less severe early GSF attack on the former than on the latter, growing in soils unsteamed for 1 and 3 years respectively.

The incidence of BRR decreased with increasing depth in infested soils but increased on plants grown in plots with partially sterilized topsoil.

Partially sterilizing soils at the G.C.R.I. and Fairfield E.H.S. decreased the incidence of BRR and increased crop weights from about the second month of picking, but fruit quality was poorer. Seasonal yields from plants in untreated soil progressively decreased relatively to those from repeatedly steamed plots, from 93 to 65 % in successive years at Fairfield and from 65 to 56 and 43 % at the G.C.R.I. Steaming done in 1963 and 1964 temporarily retarded GSF attack in 1965 with corresponding yield increases.

Increasing the amounts of sterilized propagating soil surrounding roots at planting from 0·4 to 1·01 per plant increased yields by c. 0·4 kg/plant, this being a relatively large increase for plants in infested soil, where this treatment significantly delayed the early incidence of BRR near stem bases.

Grafting commercially acceptable scions to rootstocks that tolerated colonization by GSF (‘resistant’ rootstocks), temporarily checked growth, delayed picking and decreased fruit quality. Usually grafted plants, irrespective of soil treatment, yielded at least as much fruit as ungrafted plants in steamed soil. In one of five comparisons, soil steaming increased yields of grafted plants. When testing the effects of previous cropping it seemed that populations of GSF increased similarly in soils planted with grafted and ungrafted plants.

In addition to GSF attack, roots at Fairfield E.H.S. were often colonized by Colletotrichum coccodes, microsclerotia (= black dots) being more numerous as plants aged. Although significantly more black dot developed on GSF‐resistant rootstocks grown in untreated soil than on those grown in steamed soil, the differences were not associated with effects on yield. C. coccodes colonized GSF‐susceptible and ‐resistant roots equally.
Effects of plant growth regulators and other compounds on flow of latex in Hevea brasiliensis
Authors: ABRAHAM P. D. , BOATMAN S. G. , BLACKMAN G. E. , POWELL R. G.
Published: February 2008

Eighty‐nine compounds have been tested for their ability to promote the flow of latex from Hevea brasiliensis after tapping. The twenty‐four substances which showed significant activity were: twelve chloro‐ and fluoro‐phenoxy alkylcarboxylic acids substituted in the 4‐, 2, 4‐ and 2, 4, 5‐ positions, two chlorinated benzoic acids, α‐ and β‐naphthaleneacetic acid, 3‐indolylacetic acid, 2‐methoxy‐4‐diethylamino‐6‐isopropylamino‐1, 3, 5‐ triazine (methoxy‐ipazine), N,N‐diallyl‐α‐chloroacetamide (CDAA), 1,1′‐dimethyl‐4,4′‐bi‐pyridilium‐2A (paraquat), neomycin, dichloro‐m‐xyienol, and phenyl mercury acetate and chloride. Despite the many replications the high variability of the yield data does not allow of a precise classification of the relative activities. The most active compounds were 2, 4‐dichloro‐5‐fluorophenoxyacetic acid and 2, 4, 5‐trichlorophenoxyacetic acid (2, 4, 5‐T), although 2, 4‐dichlorophen‐oxyacetic acid (2, 4‐D) gave increases in yield comparable to those of 2, 4, 5‐T in some of the trials.
The analysis of grain yield of wheat in terms of photosynthetic ability and efficiency of translocation
Authors: LUPTON F. G. H.
Published: February 2008

A technique, using 14CO2, for measuring the rate of photosynthesis and the distribution of synthesized carbohydrate in the same plant, applied to wheat plants at intervals from 10 days before anthesis until the plants were no longer green, showed that the rate of photosynthesis by the leaves and ears decreased steadily; it was much less for ears than for leaves. The proportion of carbohydrate translocated to the grain was very small at and before anthesis, but increased rapidly afterwards.

Integration of these data provided estimates of yield based on physiological components which showed good agreement with measured yields at harvest, though varietal differences in observed yield could not be explained.

An experiment in which ears were removed from plants 7 days after anthesis showed that photosynthetic activity was not limited by the size of the ‘sink’ to which photosynthates were translocated.
Hatching agents for the potato cyst‐nematode, Heterodera rostochiensis Woll
Authors: CLARKE A. J. , SHEPHERD AUDREY M.
Published: February 2008

Of 444 compounds tested for their ability to stimulate eggs of Heterodera rostochiensis to hatch, forty‐five did so to varying extents. Many compounds that hatched H. schachtii Schm. eggs did not hatch H. rostochiensis eggs. The most effective compounds with H. rostochiensis were picrolonic acid, anhydro‐tetronic acid and vanadates. Tests with analogues of picrolonic and anhydro‐tetronic acids suggested some structures that may be concerned in hatching H. rostochiensis and H. schachtii. The simple analogues hatched the eggs of H. schachtii but not those of H. rostochiensis. Suitably placed polarisable atoms seemed to be an essential feature. Picrolonic acid contains pairs of polarizable atoms, about 4 and 6·7 Å apart, that may respectively be associated with the hatching of H. schachtii and H. rostochiensis. Other features of the more active hatching agents were a cis and co‐planar arrangement of the two polarizable atoms with respect to the rest of the molecule. The function of hatching agents is discussed.
Some hosts and properties of bulbous iris mosaic virus
Authors: BRUNT A. A.
Published: February 2008

Iris mosaic virus (IMV) was the only virus isolated from forty‐six bulbous iris plants of twenty‐two cultivars tested; it was common also in Iris danfordiae and I. reticulata but was not detected in any of fifty‐two rhizomatous iris plants with mosaic symptoms. IMV was transmitted to healthy irises with difficulty by mechanical inoculation but was transmitted efficiently by Myzus persicae.

IMV infected eight of forty‐six plant species inoculated mechanically with partially purified virus preparations. Characteristic local lesions without subsequent systemic infection were produced in Amaranthus caudatus, six Chenopodium spp., and Tetragonia expansa; of these, C. quinoa and T. expansa were the best indicator and assay hosts.

The virus was moderately stable in vitro and, unlike some similar filamentous viruses, was best purified by differentially centrifuging infective sap clarified with n‐butanol. Partially purified preparations from several hosts were infective, produced one specific light‐scattering zone after centrifuga‐tion in sucrose density‐gradient columns, were antigenic and contained particles of 760 mμ model length. IMV was not serologically related to any of nine similar aphid‐transmitted, filamentous viruses.
Studies of the seed‐transmission of tobacco ringspot virus
Authors: OWUSU G. K. , CROWLEY N. C. , FRANCKI R. I. B.
Published: February 2008

Some factors influencing the transmission of tobacco ringspot virus (TRSV) by seed of soybean, Glycine max (L.) Merr. cv. Lincoln, have been studied.

The age of a plant at the time of infection was the most important factor determining the amount of infected seed produced. The inability of TRSV to infect maturing embryos was not due to slowness of virus movement within the host. TRSV was consistently found in the embryo and perisperm tissues of infected seeds but not in the testa.

All attempts to control seed‐transmission of TRSV in soybean failed. Storage for 7 months, and heat‐treatment of seed at temperatures near the thermal inactivation point of the virus, failed to inactivate TRSV in infected seeds. Spraying of TRSV‐infected plants with 2‐thiouracil and 8‐azaguanine had no effect on host infection and did not prevent seed‐transmission.
Changes in the microbial population of apple leaves associated with the inhibition of the perfect stage of Venturia inequalis after urea treatment
Authors: CROSSE J. E. , GARRETT CONSTANCE M. E. , BURCHILL R. T.
Published: February 2008

Treatment of detached apple leaves in October with urea induced a rapid and prolonged increase in the microbial populations present in the leaves during the winter. These effects were accompanied by a major shift in the population balance from a predominantly Gram‐positive, chromogenic type of microflora to one dominated by Gram‐negative and non‐chromogenic organisms. Fluorescent pseudomonads became particularly numerous in the urea‐treated leaves and many were found to suppress the development in vitro of Venturia inaequalis. An organism forming yellow colonies, possessing exceptional activity against the scab fungus, which was also found in urea‐treated leaves, was shown to be a Gram‐negative, peritrichous bacterium.

No antagonistic organisms were isolated from untreated control leaves, but many were found–usually chromogenic forms–which appeared to stimulate the scab fungus in vitro. Treatment with urea accelerated the decomposition of the leaves and suppressed the development of V. inaequalis in the portions of the laminae which remained structurally intact until the following spring.

Many of the effects of urea were enhanced by the addition of glucose, streptomycin, or a suspension of a Pseudomonas sp. isolated from leaves during the winter. Streptomycin alone reduced the total numbers of microorganisms in the leaves but increased the proportion of Gram‐negative organisms: this was associated with diminished ascospore production in the spring.

There was no direct evidence that the antagonistic flora stimulated by urea was responsible for the inhibition of V. inaequalis, and alternative explanations are suggested.
Leaf‐area development in King Edward potato plants inoculated with Verticillium albo‐atrum and V. dahliae
Authors: HARRISON J. A. C. , ISAAC IVOR
Published: February 2008

Leaf‐area development in King Edward potato plants infected with Verticillium albo‐atrum and V. dahliae was examined both in plants with a normal growth pattern and in those where maturity had been artificially delayed. Methods are described for producing uniform, single‐stemmed, initially disease‐free host plants, and for measuring their total and green leaf areas throughout their development.

Under both growth conditions the pathogens had no apparent effect upon the initiation of new leaves on the main axis of the plant, but they did influence their subsequent development. During the growing period the pathogens caused stunting, thus preventing the production of the potential maximum leaf area, while at maturity the chlorosis and necrosis of the diseased leaves and their premature fall reduced functional leaf area.

In diseased plants in which maturity had been delayed, stunting at the apices was more apparent: internode length, leaf petiolar axis length and leaf area were all smaller than in healthy plants, the greatest reductions being shown in leaf area. Cells in the stunted leaves were fewer and smaller than those in healthy leaves.

A direct result of leaf‐area reduction was the development of smaller tubers, with consequent reduction in the fresh weight, and some reduction in tuber number.

V. albo‐atrum invariably proved to be more virulently pathogenic than V. dahliae; the use of an average Verticillium index was shown to be a reliable method for estimating relative virulence since it reflected both leaf area and yield reductions.

Delaying host maturity and thus lengthening the period of extension growth conferred some resistance on plants infected with V. dahliae; symptom progression was stopped after its initial expression, and consequently leaf area was increased. This form of resistance was not shown in the plants inoculated with V. albo‐atrum.