bluuebunny/crossref_metadata_2025 huggingface dataset:
STUDIES ON THE PHOTOLYSIS OF PYRETHRUM
Authors: JONES G. D. GLYNNE
Published: February 2008

The rates of photolysis of films of pyrethrum were studied to determine the factors which could contribute to their increased stability.

The claims that the green colouring matter (referred to as chlorophyll) present in crude oleoresin contributed to the rapid photolysis of pyrethrum films were verified. Evidence was accumulated to show that light of a wide range of wavelengths could effect photolysis.

The action of para‐aminoazobenzene as a stabilizer was studied in detail and the experimental evidence obtained strongly suggested that this compound did not exert its action by virtue of its light‐absorbing properties but as a direct or indirect inhibitor of a chemical reaction. Assays of the four active principles in extract before and after irradiation showed that the PAAB protected primarily the cinerin II and pyrethrin II.

Sudan IV and p‐methoxyazobenzene and Spirit Red were shown to have similar stabilizing properties to PAAB.
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 INFLUENCE OF CARBON DIOXIDE ON THE TOXICITY OF UN‐IONIZED AMMONIA TO RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON)
Authors: LLOYD R. , HERBERT D. W. M.
Published: February 2008

The toxicity of solutions of ammonia to fish in different dilution waters showed a variation which was not entirely related to the concentration of the un‐ionized ammonia molecule. Evidence is presented which shows that this variation can be attributed to the increase in the concentration of free carbon dioxide at the gill surface, which causes a decrease in both the pH value and the concentration of unionized ammonia present; the extent of the decrease depends on the initial concentration of free carbon dioxide in the bulk of the solution. Quantitative measurements of the relation between the free carbon dioxide concentration of the water and the toxicity of un‐ionized ammonia are correlated with a theoretical estimation of the pH value of the water at the gill surface.
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.
THE EFFECT OF CERTAIN PREDATORS ON THE NUMBERS OF CABBAGE ROOT FLY (ERIOISCHIA BRASSICAE (BOUCHÉ)) AND ON THE SUBSEQUENT DAMAGE CAUSED BY THE PEST
Authors: WRIGHT D. W. , HUGHES R. D. , WORRALL J.
Published: February 2008

To determine the importance of beetle predators on the natural control of cabbage root fly, experiments were carried out in 1958 and 1959 using various types of barriers to obtain different levels of beetle populations on cauliflower plots. A barrier of DDT‐treated straw, placed in the soil around some plots, decreased the numbers of beetles within them and allowed a greater number of eggs and larvae of cabbage root fly to survive than on the untreated plots, resulting in a greater crop damage. Another type of barrier allowed the beetles to enter plots but made it difficult for them to leave. On these, fewer cabbage root‐fly eggs and larvae survived and the crop damage was much less than on the plots surrounded by straw barriers. Where plants were treated with insecticide the root‐fly population was reduced to a minimum and crop yields were considerably increased. The insecticide, however, caused a reduction in the numbers of predatory beetles.
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

The 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

The 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

The 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

Maximum 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

Certain 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

The 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

Following 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

Cysts 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

In 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.
Some variants and possible errors in the test‐tube dilution and slide‐germination methods for laboratory testing of fungicides
Authors: McIntosh A. H.
Published: February 2008

A method is given for moulding uniform Perspex (polymethyl methacrylate) cavity slides, which are quickly made, almost unbreakable and without joints; they can withstand strong alkalis, but not strong acids or solvents, and are useful for spore germination tests of water‐soluble fungicides. When the drops of spore suspension‐fungicide mixture in the cavities of these slides or of Böttcher's glass cavity slides are enclosed by cover‐slips, there is no meniscus effect, and in tests of long duration the same spores can be counted repeatedly.

In such tests, errors may arise from sorption of the fungicide on the surfaces of pipettes and tubes (dilution stage) and on slides and cover‐slips (incubation stage); and from changes in the volume of the drops (incubation stage).

Ions of many metals may be lost by sorption, and the losses are often greater on soft than Pyrex glass. Hg was lost rapidly. In a three‐stage serial dilution of HgCl2 solution in soft glassware from 60 to 1.0 p.p.m. of Hg, the loss in strength was 27%. More Hg was lost from HgCl2 than from phenyl mercuric acetate solutions. The losses on glass or Perspex slides with cover‐slips from solutions containing 1.0 p.p.m. of Hg (but no spores in suspension) were 30–35% in 15 min. and 61–74% in 24 hr. with HgCl2, but only 5–10% on glass and 35–37% on Perspex slides in 24 hr. with phenyl mercuric acetate. Increase in temperature (10–25% C.) slightly increased the loss from HgCl2 but not from phenyl mercuric acetate solutions. Perspex slides, which were used repeatedly for tests of water‐soluble mercury compounds and washed in distilled water after each test, eventually became toxic to conidia of Botrytis fabae Sardiña.

When the slides, with drops, are placed in moist chambers for incubation, some evaporation is unavoidable because the air close to them is not initially saturated with water vapour. When the chambers were pre‐cooled or pre‐warmed, so that the temperature of the air in them was uniform, the loss from 0.30 ml. drops in cavity slides was not serious (about 8%, with or without cover‐slips, in 48 hr. at 10 or 25% C.). But when the temperature was not uniform, the possibilities of change in drop volume were much greater: in 48 hr., the volume of open drops could decrease by evaporation (44% loss at 10° C.) or even increase slightly by condensation (3% gain at 25° C.). When spores have to be counted on several occasions, the evaporation losses may be more serious.
Chocolate spot of beans (Vicia faba L.)—interactions between phenolase of host and pectic enzymes of the pathogen
Authors: DEVERALL B. J. , WOOD R. K. S.
Published: February 2008

Botrytis fabae and B. cinerea, pathogens which cause ‘chocolate spot’ of beans (Vicia faba L.) produced polygalacturonase abundantly in media containing pectic substances or soluble cellulose derivatives; only filtrates from cultures grown on poly‐pectate had pectinesterase activity and even this was relatively low. B. cinerea filtrates from media containing cellulose had appreciable cellulase (Cx) activity, but did not degrade insoluble wood cellulose; B. fabae filtrates were inactive in both respects. Cultures of both fungi on certain types of media readily macerated sections of bean stems and caused them to become brownish black in colour.

Filtrates from cultures of both fungi had considerably lower polygalacturonase activities when leaf extracts were present in otherwise suitable media.

The latent phenolase present in water extracts of leaves was activated by poly‐pectate, polygalacturonic acid, pectin and carboxymethylcellulose. Activation was most rapid near pH 4.5 and was negligible at pH 5.5 which was the optimum value for sodium dioctyl sulphosuccinate, one of the best activators so far described. Solutions of the polymers could be diluted with no great effect on activations.

Lesions are produced more readily on old than on young leaves, and extracts of old leaves discolour more rapidly than do extracts of young leaves when exposed to activated phenolase from bean leaves. This is because young leaves contain some system which retards the development of the coloured products which are normally produced following the oxidation of phenols.

Water extracts of bean leaves inactivate the polygalacturonase of both fungi. The polygalacturonase of B. fabae differed from that of B. cinerea in being rapidly inactivated after filtrates had been diluted with water, and by being inactivated quickly by cyanide. B. fabae polygalacturonase was inactivated relatively quickly by products formed after oxidation of dihydroxyphenylalanine, but was less affected when catechol was used; B. cinerea behaved in the opposite way.

The mechanisms by which both fungi cause lesions on bean leaves are discussed in the light of the results summarized above.
Fruit‐spot (‘speckle’) of Jamaican bananas caused by Deightoniella torulosa (Syd.) Ellis
Authors: MEREDITH D. S.
Published: February 2008

Using an automatic volumetric spore trap, variation in the atmospheric spore content of Deightoniella torulosa (Syd.) Ellis, the cause of banana fruit ‘speckle’, has been studied in a banana plantation during the period September 1960‐February 1961. Dry weather was characterized by relatively low daily mean spore concentrations of 50–200 spores/m.3of air. Much higher concentrations (2000–7000 spores/m.3) were recorded shortly after rainfall or periods of under‐tree irrigation.

Considerable reduction in concentration occurred after the removal from the plantation of decaying leaves and other banana ‘trash’, such tissues being the major source of inoculum of D. torulosa. Similarly, spore counts in trash‐free plantations were consistently lower than those in ‘dirty’ ones. Although the evidence is not conclusive, since it was not possible to provide controls, it seems likely that good plantation hygiene is a major factor in reducing the air spore content of the fungus.

In the plantations, the large conidia of D. torulosa have a short air‐borne phase, probably because sedimentation and/or deposition rates are high. This results in relatively short horizontal dispersal distances.
Germination and penetration studies on coffee rust (Hemileia vastatrix B. & Br.)
Authors: RAYNER R. W.
Published: February 2008

Spore dispersal, germination, penetration and incubation‐period studies on coffee rust (Hemileia vastatrix B. & Br.) in Kenya, East Africa, are described.

Evidence is produced that air‐borne spores may be trapped effectively on the upper surfaces of leaves, thence to be liberated and transported to the undersurfaces of other leaves by rain splash.

Germination requires liquid water and was observed to occur in 2.6–4.7 hr‐(medians) at 23° C., the minimum being 1 hr. Appressoria were formed in 6.5–8.5 hr. (medians) with a 5.3 hr. minimum. Germination is inhibited by light and in the field by the rapid evaporation of water droplets on the lower leaf surface which occurs during daylight. Light inhibits the growth of germ tubes that are less than 30 μ long and reduces rate of growth if they are longer; appressoria may continue to form.

In the field, appressorium formation and infection can occur between 10 p.m. and 8 a.m. If coffee trees are wet at dusk or rain falls before midnight, infection is probable and it is proposed that the number of occasions this occurs be used to forecast the severity of the annual rust maximum.

The median incubation period throughout the year varied from 4 to 7 weeks, increasing with low temperatures and dry conditions. A multiple regression of mean maximum and minimum temperatures on incubation period gave fair agreement between observed and computed values for Ceylon and Mysore. Susceptibility and incubation period were strongly affected by coffee variety and rust biotype, but not by age of leaf or crop size.
Field observations on the control of blossom beetles (Meligethes aeneus F.) and cabbage‐seed weevils (Ceuthorhynchus assimilis Payk.) on mustard‐seed crops in East Anglia
Authors: WINFIELD A. L.
Published: February 2008

Field trials on the control of blossom beetles (Meligethes aeneus F.), and cabbageseed weevils (Ceuthorhynchus assimilis Payk.) were carried out in East Anglia during 1958 and 1959, and twenty‐six commercial crops of Trowse mustard (Brassica juncea Coss) were surveyed during the summer of 1959. The development of a Trowse mustard plant, and damage by adult and larval blossom beetles are described. Methods for assessing the damage done by both blossom beetles and seed weevils are discussed, and a preliminary attempt has been made to differentiate the effects of the two pests on the yields of seed.

It has been confirmed that DDT is unsatisfactory for the control of seed weevils; two carefully timed applications of dieldrin will probably give an economic control of both blossom beetles and seed weevils. Spraying usually gave increased yields of seed, sufficient to cover the cost of treatment, but a single spray was not persistent enough to give a good control of the damage by adult and larval blossom beetles, and at the same time to control the damage by seed weevil larvae. A single spray applied during May, when the population of adult blossom beetles was rising, did not prevent later adults or larvae from causing damage. A single spray applied shortly before flowering began allowed the early immigrant adults to cause damage but gave some control of the larvae. The infestation of pods by seed weevil larvae was best controlled by a spray during the early‐flowering period. Because of the risk of harming bees and other beneficial insects it is unlikely that a spray during the blossom period could at present be recommended as a routine for all mustard crops.
Comparison between malathion spraying and lindane‐whitewash mixture for controlling Ephestia elutella (Hübn.) in warehouses
Authors: ARMSTRONG MARGARET T.
Published: February 2008

Provisional estimates of the total numbers of adult Ephestia elutella emerging from warehouse rooms of about 4000 cu.ft. were between 228,300 and 509,300 in ‘moderately infested’ rooms and 1,670,000 in a ‘heavily infested’ room.

Moths caught on commercial fly‐papers are a useful index to the emergence date of adult E. elutella.

A trial in a Liverpool warehouse in 1958 showed that lindane in a commercial whitewash mixture, applied to walls and ceilings to produce an initial deposit of 40 mg. γ‐BHC/sq.ft., will remain effective against E. elutella between May and December. To obtain this deposit it was necessary to apply over twice this dosage. Very few active moths were seen and a negligible larval migration took place from trap bags which had been the only foodstuffs stored there.

Observations over the same period in a warehouse which had been treated commercially at a heavy dosage, in December 1957, showed similar results.

Cage tests in the laboratory and in the field indicated that malathion water‐dispersible powder, applied at an initial deposit of 162 mg. malathion/sq.ft., would theoretically be as satisfactory as lindane‐whitewash mixture. In warehouses, however, the former was not so effective as the latter, probably because of the marked fumigant effect of gamma‐BHC.

There were indications that lindane‐whitewash mixtures alone might control infestations of endemic E. elutella in fully loaded rooms.
Studies on Gloeosporium musarum Gke. & Massee causing storage rots of Jamaican bananas
Authors: MEREDITH D. S.
Published: February 2008

In several commercial‐scale experiments, bunches of bananas were treated by immersing for approximately 1 min. in 2% Shirlan WS and then rinsing in water. Reports obtained after ocean transportation and subsequent ripening of fruit in England indicated that this treatment effected poor or no control of fruit‐rot caused by Gloeosporium musarum Cke. & Massee. Possible reasons for this are discussed in relation to earlier laboratory trials.
Potato haulm resistance to Phytophthora infestans
Authors: LAPWOOD D. H.
Published: February 2008

Reasons were sought for the difference in haulm resistance to potato blight (Phytophthora infestans (Mont.) de Bary) of four potato varieties. Up‐to‐Date produced more foliage than King Edward, Majestic and Arran Viking and a denser canopy which prolonged periods of high relative humidities, and lowered mid‐day temperatures by a few degrees. When field conditions favoured infection, the fungus spread in all varieties, but most extensively in King Edward and least in Arran Viking. Infections developed first, mainly in the lower crop canopy, then the middle and finally in the upper canopy, with lesions on leaves and leaflets distributed similarly on all varieties.

The fungus advanced at the same rate in leaf laminae of all the varieties, but not in petioles, which were girdled more rapidly in Up‐to‐Date and King Edward than in the other two and consequently led to the collapse of more leaves.

Majestic and Arran Viking are more resistant than Up‐to‐Date and King Edward in the field, because their leaves are infected more slowly early in the blight attack and die more slowly after infection.
An attempt to increase yield by controlling leaf‐area index
Authors: WATSON D.J. , FRENCH S.A.W.
Published: February 2008

Previous work showed that the leaf‐area index (L) of kale crops in their later stages of growth can be much above the optimum for dry‐matter production, which was between 3 and 3.5. When L was held close to 3.5 during July‐September 1955, by repeated thinning of plants, the total yield of dry matter including thinnings was increased by about 6%. When thinning was more severe yield was not increased. In a similar period in 1956, thinning that held L between 3.5 and 4 or between 3 and 3.5 did not increase total yield of dry matter, because in this year optimal L was much higher than before. The explanation of the seasonal variation in optimal L is not known.
Studies on plant growth‐regulating substances XVI. The auxin‐activity of ω‐(N,N‐dimethylthiocarbamoylthio)alkanecarboxylic acids, and their β‐oxidation within plant tissues
Authors: GARRAWAY J.L. , WAIN R.L.
Published: February 2008

Members of the homologous series (CH3)2NC(S)S(CH2)nCO2H n= 1–6, were prepared and their plant growth‐regulating activities were examined in three different tests. Derivatives of some of these acids with methyl groups in the fatty acid chain were also studied. The metabolism in wheat and broad‐bean plant tissues of two of the homologues were investigated, the products of metabolism being identified by chromatography. All results are shown to be consistent with the theory that the fatty acid chain in this series of compounds becomes degraded in the plant by β‐oxidation.
Seed transmission of Didymella stem‐rot of tomatoes
Authors: MAUDE R.B.
Published: February 2008

In studies on seed transmission of Didymella stem‐rot of tomatoes in the outdoor crop, heavily infected seed was sown in the glasshouse in January, March and April and the surviving plants were subsequently planted in the field. 50% of the plants grown from the January sowing became infected and a few of them first showed symptoms after planting in the field. On the other hand only 9 and 5%, respectively, of the plants from the other two sowings became infected, none of them after field planting. No infection occurred on plants raised in soil in which infected seeds had previously been sown. Lesions arising from seed‐borne infection occurred on the cotyledons or hypocotyl and could be distinguished by their position on the mature plant from those resulting from other sources.
Experiments with slug baits in South Wales
Authors: WEBLEY D.
Published: February 2008

0.025% endrin and 0.05% Rogor (dimethoate), when incorporated in standard metaldehyde and bran slug baits did not increase the catch of slugs. Both insecticides in bran biscuits acted as repellents.

The addition of 1 part of 50% Sevin (I‐naphthyl‐N‐methylcarbamate) to 40 parts of the standard metaldehyde and bran mixture improved the catch by 15%.

Arion hortensis did not appear to be attracted to metaldehyde to the same extent as Agriolimax reticulatus and Milax budapestensis and the latter species responded more when the nights were warm.

Meteorological observations suggest that in the autumn and winter months more slugs are trapped when the night air temperature and the morning relative humidity are high. The age of the biscuits, the grass minimum temperature and the mean night air temperature accounted for 70% of the variance of the catch of metaldehyde biscuits.
Some properties of the virus causing ‘woodiness' of passion fruit in Western Nigeria
Authors: MARTINI C.K.H.
Published: February 2008

‘Woodiness’ of passion fruit (Passiflora edulis Sims.) in Kenya and Australia is considered to be caused by cucumber mosaic virus. A virus from similarly affected vines in Western Nigeria is transmissible by sap inoculation and by Aphis gossypii Glover, as is cucumber mosaic virus and the ‘woodiness’ virus in Kenya and Australia, but its apparent restriction to the genus Passiflora, the shape of its particles and the manner of transmission by aphids suggest that it is a distinct virus for which the name passion fruit mosaic virus is proposed. Chenopodium amaranticolor Coste & Reyn. produces countable local lesions when inoculated with preparations purified and concentrated by heat clarification and high‐speed centrifugation. Salt concentrations that are tolerated by other plant viruses seem to inactivate passion fruit mosaic virus.
Studies of pelargonium leaf curl virus
Authors: HOLLINGS M.
Published: February 2008

A virus consistently isolated from pelargoniums showing symptoms of leaf curl infected fifty‐four out of ninety‐nine plant species by sap inoculation. The virus was cultured in Nicotiana clevelandii, and assayed in Chenopodium amaranticolor, Gomphrena globosa or Phaseolus vulgaris; C. amaranticolor, P. vulgaris and Antirrhinum majus produced diagnostic symptoms. During the summer, the virus could not be isolated from pelargoniums, when they show no symptoms, although it is readily transmissible between other plants at all times. Pelargoniums proved immune to infection between March and September, but were readily infected during the winter by sap inoculation from N. clevelandii though not from infected pelargoniums, in which the virus titre is very low. Many infected pelargoniums no longer contained the virus after being grown for a summer in a warm glass house, and plants grown for 4 weeks at 37° C. in a heat chamber were freed from virus.

Leaf curl virus was not transmitted by handling, plant leaf or root contact, or by the cutting knife, nor when healthy and infected pelargoniums were exposed together outdoors. Experiments did not detect any virus transmission through the seed or soil, nor by four species of aphid or the glasshouse whitefly.

Infectivity was destroyed by heating infective sap for 10 min. at 90° C. and, often, at 85° C.; expressed sap was still infective after dilution to 1:100 (pelargonium) or 1:40,000 (N. clevelandii), and infectivity persisted for at least 21 days in sap at c. 18° C. and more than 3 years at 0° C.

The virus was fairly stable in vitro and could be partially purified and concentrated in several ways: the butanol‐centrifugation method proved best. Specific antisera were made by intramuscular injection of such preparations into rabbits, and were successful in tests by precipitin tube, micro‐precipitin drop and gel‐diffusion methods. Electron micrograms of virus preparations contained icosahedral particles about 28 mμ diameter. The virus produced one, two or more distinct light‐scattering zones when centrifuged to equilibrium in density‐gradient sucrose columns; these zones were associated with maximum serological activity, infectivity, and concentration of particles.

Leaf curl disease seems to spread slowly in Britain and is not a threat to commercial cultivation of pelargoniums; it can be controlled by selection of material for propagation, or heat treatment of any badly‐affected varieties.
Dispersal of conidia of Cordana musae (Zimm.) Höhnel in Jamaican banana plantations
Authors: MEREDITH D.S.
Published: February 2008

The air in several Jamaican banana plantations was sampled from July 1960 to September 1961, using an automatic volumetric spore trap. Conidia of Cordana musae, a banana leaf pathogen, display regular diurnal periodicity, the peak concentration of conidia per m3. of air normally occurring near 07.00 hr. The period of most rapid liberation corresponds with that of rapidly increasing temperature and decreasing R.H. Relatively low daily mean conidium concentrations (< 20 per m3.) were recorded in St Catherine where the incidence of Cordana leaf spot was low. Appreciably higher counts were obtained at Bodles where the trap was operated close to diseased plants. With few exceptions, nights when humidity exceeded 95% R.H. for less than 5 hr. were followed on successive days by concentrations lower than c. 25 conidia per m3. Rainfall and irrigation, resulting in longer periods of high R.H. at night, were usually followed by markedly higher concentrations (50–400 conidia per m3.). The highest hourly estimate recorded was c. 4000 conidia per m3.