bluuebunny/crossref_metadata_2025_split huggingface dataset:
STUDIES UPON THE COPPER FUNGICIDES
Authors: ARMAN P. , WAIN R. L. 
Published: February 2008

A study of the absorption of soluble copper by apple leaves was undertaken with a view to obtaining a better understanding of the mechanism of copper spray damage.The ability of young apple leaves to absorb copper was found to be relatively high and this may be due to the large number of stomata and hairs present. As the leaves grew more mature this capacity fell, rose again to a maximum in July or August and then fell again as the leaves approached senescence. It is suggested that these changes may be due to seasonal changes in leaf metabolism, which probably affects nutrient absorption by leaves as in roots.It has been observed in the field that apple leaves are often more susceptible to copper spray damage in the autumn. Since absorption is then at a low level it is concluded that the rate of absorption is not the only factor affecting damage to leaves caused by copper sprays.The presence of injuries in the leaves has two effects: first, it causes an increased excretion of copper‐dissolving substances (Arman & Wain, 1958) and, secondly, it increases the rate at which soluble copper is absorbed. A combination of these two factors may bring about localized spray damage. However, the increase in the absorption of soluble copper caused by the presence of extensive injuries in the leaves was sufficiently small for the conclusion to be drawn that injuries do not normally constitute a major route for the entry of copper into the leaf and it is probable that spray damage can occur in the absence of injuries.
THE EPIDEMIOLOGY OF PHYTOPHTHORA INFESTANS
Authors: HIRST J. M. , STEDMAN O. J. 
Published: February 2008

Temperature and relative humidity of air within and above potato crops were recorded throughout the growing seasons of 1951‐8, with wet‐ and dry‐bulb mercury‐in‐steel thermographs. Diurnal periodicity curves of successive weeks showed that conditions within the crop changed, relative to those above, as the crop grew. When much bare ground was exposed, the air within the crop was warmer and less humid at midday than at 4 ft. above ground, particularly in dry and sunny weather. The growth of the foliage and the amount of sunshine and rain determined how quickly this pattern was replaced by one with smaller temperature differences and crop humidity slightly in excess of that above it, at all times of day. Rain on crops with dense foliage almost completely eliminated temperature differences and gave relative humidities over 90% that persisted in the crop for a larger proportion of each day than in the screen. Finally, as the disease defoliated the crop and again exposed the soil, the relationship partly reverted to that early in the season.Above the crops, curves of the number of hours per day with relative humidity not less than 90%, rose and fell with the passing of wet spells. At first this was also true within crops, but when foliage was dense the rise in relative humidity after rain often persisted through intervals of dry weather. Such conditions usually preceded the appearance of potato blight in epidemic proportions by 1–3 weeks. It is difficult to account for the regularity of blight outbreaks by seasonal climatic changes, and although many factors are probably involved, changes in ecoclimate seem important. When knowledge about the response of Phytophthora infestans is related to the meteorological observations and to the dates of blight outbreak, the growth of potato crops seems often to be self‐destructive, because it progressively modifies the immediate environment to favour the spread of the crop's most destructive pathogen.
STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS
Authors: SABET K. A. 
Published: February 2008

The atypical symptoms first described by Bryan (1932) of the angular leaf spot disease of cotton caused by Xanthomonas malvacearum (E. F. Sm.) Dowson were reproduced by inoculation into seeds, stem apices or buds. The lesions that developed on the veins of the newly produced leaves were elongated and water‐soaked, becoming dark brown. The leaf tissue dependent upon infected veins became yellow, flaccid and withered. The development of these symptoms was enhanced when inoculations were made into opening buds or germinating seeds as compared with inoculations into closed buds or dormant seeds.In other bacterial diseases caused by Xanthomonas spp., somewhat atypical symptoms could also be produced by bud inoculation into the appropriate host. Those produced by X. ricini (Yoshi & Takimato) Dowson on castor, closely resembled the vein lesions described above on cotton but resulted only from bud inoculations; inoculations into stem apices and seeds failed to produce them. In dolichos bean inoculated with X. phaseoli (Smith) Dowson, atypical symptoms were produced only by seed inoculations and were confined to the first simple leaves (prophylls).The differences in the production of atypical symptoms on the three hosts are correlated with differences in host structure and with the degree of virulence of the pathogen. The leaf parasite X. ricini, for example, which cannot infect castor bean stems, does not produce atypical symptoms when inoculated below the stem apex.From the data discussed below, the incidence of atypical symptoms is attributed to infection either of an actively growing tissue or of a telescoped structure which subsequently completes its development.The atypical symptoms of the cotton disease are not caused by a special strain of X. malvacearum. Further, they are not a peculiarity of this disease but may also develop in other necrotic diseases under similar conditions.
THE TRANSMISSION BY MITES, HOST‐RANGE AND PROPERTIES OF RYEGRASS MOSAIC VIRUS
Authors: MULLIGAN T. E. 
Published: February 2008

A virus that causes chlorotic streaks on ryegrass leaves was transmitted by the eriophyid mite Abacarus hystrix (Nalepa). Virus‐free mites acquired the virus in 2 hr. feeding on infected ryegrass and the proportion that became infective increased with increased feeding time up to 12 hr.; vectors lost infectivity within 24 hr. of leaving the infected leaves. All instars of A. hystrix transmitted the virus.The virus was transmitted by manual inoculation of sap to other species of Gramineae, including oats, rice, cocksfoot and meadow fescue, but none of these hosts seemed to contain as much virus as ryegrass; their saps did not precipitate specifically with antiserum prepared against the virus in ryegrass, whereas sap from infected ryegrass precipitated up to a dilution of 1/32. Infective sap of S22 Italian ryegrass contained flexuous rod‐shaped particles; the dilution end‐point of the virus was about 1 in 1000; the virus was inactivated when held for 10 min. at 60°C. and most of its infectivity was lost after 24 hr. at room temperature.
AN ANALYSIS OF COMPETITION BETWEEN BARLEY AND WHITE PERSICARIA
Authors: ASPINALL† D. 
Published: February 2008

White persicaria grown with barley had a lower relative growth rate, a lower net assimilation rate, a higher leaf‐area ratio and a higher leaf‐area: leaf‐weight ratio than when grown alone. These differences were accentuated with time and with increase in the density of the surrounding barley plants. That the responses were those of plants subjected to a high degree of shading was confirmed by growing spaced plants under differing degrees of shade and from measurements of the amount of light penetrating the mixed stands. However, they do not necessarily demonstrate that light was the environmental factor in shortest supply.An attempt was made to distinguish the effect of competition between shoots from competition between the roots. Root competition appeared to reduce growth more than shoot competition although the influence of the latter increased with time. Increase in nutrient supply, which was varied by supplying, at weekly intervals, solutions of various dilutions, caused a proportionately greater increase in the growth of white persicaria than of barley in a mixed population.These results suggest that restricted nutrient supply was the factor which first decreased the growth of white persicaria. This was a direct consequence of its smaller root system arising from a smaller embryo than that of barley. The divergence between the amount of growth of the two species with time led to the white persicaria plants becoming progressively more and more shaded, and ultimately caused a further reduction in the rate of expansion of the root system and of the leaves. Although restriction in light was certainly concerned, as shown by the type of plant produced, it seemed likely that mineral nutrients were the factors always in shortest supply.The reduction in tiller number, but not in dry weight, of barley when grown with white persicaria was interpreted as a response to a lower internal concentration of nitrogen arising directly from the lower external concentration. Root extension did not appear to be significantly reduced.
LABORATORY ERRORS ASSOCIATED WITH THE ESTIMATION OF THE POPULATION DENSITY OF HETERODERA SPECIES IN SOIL
Authors: MORIARTY F. 
Published: February 2008

As unexpectedly large sampling errors were obtained in preliminary population studies on Heterodera, an examination was made of the laboratory errors associated with sampling for H. göttingiana and H. schachtii. Soil samples were taken from microplots and appeared to be satisfactory, being without the usual heterogeneity found in sampling from fields. There was little evidence of errors introduced by the technique used for estimating the number of eggs and larvae in a subsample. These errors, when they occurred, were always small, and this standard technique was deemed satisfactory. The logarithmic transformation was suitable for statistical analysis of both cyst and egg counts.Apart from the residual variation, there were two other important sources of variation when sampling for eggs. There was a large variation between sub‐samples, caused by differences in the number of cysts and in the number of eggs per cyst. There was also in some instances a difference between observers counting the same eggs of up to 20%. Where a comparative measure of density is sufficient, this bias is probably unimportant, and to increase accuracy of estimates of eelworm density, most laboratory work should be devoted to the separation of cysts from the soil sample.
FIELD EXPERIMENTS ON CEREAL ROOT EELWORM
Authors: STONE L. E. W. 
Published: February 2008

In 1955‐59 experiments were carried out in south‐west England on field sites heavily infested by the cereal root eelworm, to determine the behaviour of the soil population under various crops.Under three common types of ley, the population fell to less than 5% of its original level in 3 years.Of six pure grass stands tested, the population fell most sharply under cocksfoot and tall fescue.Observation plots under the four cereals illustrate their different efficiencies as hosts.
EXPERIMENTS ON THE AIRTIGHT STORAGE OF DAMP GRAIN
Authors: HYDE MARY B. , OXLEY T. A. 
Published: February 2008

Airtight storage as a means of preventing deterioration of damp grain was studied both on a laboratory scale and in 10‐ton bins, at grain moisture contents from 17 to 24%.Except when containers leaked, there was no development of mould, and the grain was bright and free‐flowing, even after prolonged storage, at high moisture content. The grain remained mould‐free after a bin was opened several times and small quantities of grain run out in cool weather. Such grain, removed from hermetic conditions and stored in sacks in an unheated building, showed no mould development for several weeks.With prolonged hermetic storage or at high moisture content the grain developed a sour‐sweet smell and taste which when extreme were not entirely removed by subsequent airing or drying.There was no spontaneous heating; the grain in the 10‐ton bins reflected the mean temperature of the surroundings.The oxygen in the intergranular air was reduced to a low level and replaced by carbon dioxide within a few days or weeks, according to the moisture content and temperature of the grain. At moisture contents of 16% and above, appreciable positive pressure developed inside the containers. The carbon dioxide concentration rose to 90–95% at grain moistures of 22–24%, 70–75% at 19%, 50% at 18%, and 35–40% at about 17% moisture content. The change from aerobic to anaerobic activity was marked by a reduction in the rate of production of carbon dioxide. With grain of less than 14% moisture content, the rate of respiration was slow, the carbon dioxide concentration being only about 2% after 18 months' storage. As long as oxygen remained, the apparent respiratory quotient was consistently between 0.6 and 0.7, whatever the moisture content of the grain.This work formed part of the programme of work of the Pest Infestation Laboratory.
STUDIES ON THE IMPORTANCE OF WILD BEET AS A SOURCE OF PATHOGENS FOR THE SUGAR‐BEET CROP
Authors: GIBBS A. J. 
Published: February 2008

Beet yellows virus, beet mosaic virus, rust (Uromyces betae (Pers) Lév.), and downy mildew (Peronospora schachtii Fuckel.) were found to be common in wild beet (Beta vulgaris s.‐sp. maritima L.) growing on the foreshores of south Wales and southern England. The virus diseases were more prevalent in southeast England than in the west, rust more in the west than in the east, and downy mildew is equally prevalent in all regions.Beet yellows is the most commercially important disease and is more common in sugar‐beet crops in East Anglia than elsewhere in Great Britain. There was no evidence that beet yellows spread in East Anglia from wild beet to nearby sugar‐beet crops during the springs of 1958 or 1959, and Myzus persicae Sulz., the principal vector of yellows, was rarely found on wild beet growing on the foreshore.In glasshouse experiments aphids colonized sugar‐beet plants watered with tap water in preference to those watered with sea water. Daily watering with sea water made plants unpalatable to aphids within 14 days. Aphids also preferred leaves sprayed with distilled water to those that had been sprayed with sea water. Salt solutions gave results similar to those obtained with sea water.
Host finding by aphids in the field
Authors: KENNEDY J. S. , BOOTH C. O. , KERSHAW W. J. S. 
Published: February 2008

SUMMARYThe spectral energy distribution of the light reflected from various leaves and soils has been measured and corrected for ‘standard’ sunlit conditions, and then compared on the basis of Moericke's evidence that aphids of many species distinguish two parts of the spectrum as colours, alighting and probing in response to wavelengths greater than 500μ.Alightments by Brevicoryne brassicae and Myzus persicae in the field occurred preferentially on leaves reflecting a greater proportion of long‐wave energy, with little or no regard for the ‘botanical’ (plant‐taxonomic) host status of the plants for each aphid. The colour attraction of such ‘yellow‐sensitive’ aphids serves rather to bias their alightments towards plants of the appropriate physiological type.Laboratory experiments confirmed the existence, inferred from field observations, of a second, non‐specific mechanism of visual attraction normally involved in alightments on plants, namely a close‐range optomotor reaction with both orienting and arresting components.The light reflected from various soils embodied maximum energy at the extreme long‐wave end of the spectral range affecting aphids, while the leaf energy peak was 540–560 mμ. The predominantly long‐wave emission from both leaves and soils contrasts sharply with the light from clear or clouded skies, wherein the peak energy region lies below 500 mμ. The aphids' type of colour vision thus provides for a primary discrimination between sky and ground, beside any subsidiary discriminations among plants and soils.Low‐flying Aphis fabae were attracted to white surfaces as well as to yellowing leaves in the field. The change in the migrant's behaviour from ‘distance flight’ in the upper air to low‐level ‘alighting flight’ appears to be due, not to a reversal of the response to short‐wave sky light from positive to negative, but simply to a relative strengthening of the positive response to long‐wave light from the ground.
Observations on the pollination of red clover by bees
Authors: HAWKINS R. P. 
Published: February 2008

SUMMARYThe pollinators of red clover are described and the relationship between the number of seeds set per head and the yield of clover seed is recorded.Two methods of recording insect pollination in relation to the numbers of seed set per head of clover were explored in 1955. In 1956 and 1957 recording of actual crops of seed was continued.Certain species of humble‐bees are important in the production of singlecut red clover seed, and in the production of doublecut red clover seed in 1956, although another factor, possibly honey‐bees, was dominant in 1957.There was no indication that ‘robbing’ was associated with a lower ‘seed set’; on the contrary in 1957 it was associated with a higher ‘set’, possibly because it attracted honey‐bees to the crop.The data showed that the numbers of the different species of humble‐bees varied, but gave no indication of the relative effectiveness of the various species in pollination. Those present in greatest numbers were of most value for pollinating red clover.Pests and diseases likely to reduce seed set were found to be negligible during 1955, 1956 and 1957. Differences in fertility between one field and another were small.
Potato haulm resistance to Phytophthora infestans
Authors: LAPWOOD D. H. 
Published: February 2008

SUMMARYThe resistance to potato blight (Phytophthora infestans (Mont.) de Bary) of the haulms of four potato varieties, Up to Date (UD), King Edward (KE), Majestic (MJ) and Arran Viking (AV) was assessed in the field from 1956 to 1959. Although these varieties are reputed to differ appreciably in resistance, the differences measured were smaller than expected and significant in only two seasons. They were shown better by measurements on individual leaves than by assessing effects on whole plots. The greater resistance of AV and MJ, compared with UD and KE, was correlated with a slower increase of blight at the start of an attack rather than with differences in the rate of haulm destruction when the attack was well advanced. However, there was some evidence that leaves of KE died most rapidly and leaves of AV most slowly after infection.
Fungicidal activity and chemical constitution IX*
Authors: BYRDE R. J. W. , CLIFFORD D. R. , WOODCOCK D. 
Published: February 2008

SUMMARYMaximum fungistatic activity in a series of 6‐n‐alkyloxines, tested against the mycelium of Aspergillus niger, was shown at a chain length of 6–7 carbon atoms. 6‐n‐Hexyloxine was more active than the corresponding 5‐n‐hexyl compound, the ED 50 value being approximately half.In the presence of Cu2+, maximum activity was found with oxine and 6‐methyloxine; with some higher members of the series a rapid initial growth rate fell sharply after 2 days. This growth inhibition was shown to be due to the production of oxalic acid by the fungus, which resulted in the liberation of the free oxine.
Investigations on fungitoxic derivatives of salicylaldehyde
Authors: SMITH R. J. , READ W. H. 
Published: February 2008

SUMMARYCertain N‐alkyl, N‐aryl and N‐heterocyclic derivatives of three halogenated salicylideneimines have been synthesized and tested for eradicative activity against cucumber powdery mildew. Although the activity of several of these compounds closely approached that of 3‐chlorosalicylideneaniline, which showed pronounced activity in an earlier investigation, no compound of practical value was discovered.
The fungitoxicity of metal ions
Authors: SOMERS E. 
Published: February 2008

SUMMARYThe in vitro fungistatic activity of some twenty‐four metal cations has been determined against Alternaria tenuis and Botrytis fabae. The metal salts, mainly nitrates, were tested in aqueous solution without added spore germination stimulant. The logarithm of the metal ion concentration at the ED 50 value has been found to conform to the exponential relationship with electronegativity proposed by Danielli & Davies (1951). These results are discussed in relation to the site of action of metal cations on the fungal cell.
Concentrate spraying of apple trees
Authors: MOORE M. H. 
Published: February 2008

SUMMARYFollowing earlier indications of the importance of the quantity of lime‐sulphur concentrate applied per acre (dosage) in the control of apple scab and powdery mildew, further intensive paint‐gun experiments were designed to clarify basic dosage/volume relationships. They established that control depends primarily on the dosage and not merely on the volume of spray applied, but the volume was in some circumstances a critical factor in spray damage.Incidental data showed the influence of lime‐sulphur dosage also on the population of fruit tree red spider mite and on infestations of sawfly. There was evidence that the incidence of fruit russet and poor skin finish is sometimes related to impaired foliage.Gravity flow and droplet‐size of spray together increased with increasing dilution of lime‐sulphur, and thus influenced spray distribution on the foliage when a range of dilutions was applied at fixed volume/acre.
Heterodera rostochiensis (Woll. 1923) on Solanum demissum—a population study
Authors: HESLING J. J. 
Published: February 2008

SUMMARYCysts of three different size grades provided three series of six different inoculum levels of Heterodera rostochiensis on Solanum demissum. The cyst numbers were adjusted so that the infestation levels in terms of eggs per gram of soil were the same in each series at any one inoculum level. Thus, the inoculum was dispersed within many small cysts, several medium cysts or few large ones. The different dispersion of the infestation had little effect on the final eelworm population. New cysts produced in the experiment were size‐graded and their total egg content and hatchable larval content were estimated. Neither size‐grade of the inoculum cysts nor the level of infestation had any effect on the content or hatchability of the graded new cysts. Percentage hatch appeared to decline with increase of cyst size; no useful decrease in hatching variability was achieved by using graded new cysts in hatching tests. The smallest new cysts (< 0.295 mm.) contained an average of sixty‐four eggs; such cysts are easily overlooked in soil samples.
The disfiguration of painted surfaces by fungi, with special reference to Phoma violacea
Authors: EVELEIGH D. E. 
Published: February 2008

SUMMARYIn a survey of moulds attacking painted surfaces, Phoma violacea was found commonly associated with paintwork in glasshouses (twenty‐eight isolates) and was once observed on exterior paintwork. No source of infection was traced, except for the attack on exterior paintwork which probably originated from a nearby glasshouse. Distribution by insects was noted. P. violacea was shown capable of attacking paint films from either surface (above or below) and penetration of the film from the top surface was demonstrated in laboratory and natural exposure tests. P. violacea was used in standard methods of testing fungicidal paints in comparison with other genera commonly employed. The development of strains resistant to fungicides was noted.