bluuebunny/crossref_metadata_2025_split huggingface dataset:
The epidemiology of tomato mosaic
Authors: BROADBENT L. 
Published: February 2008

SUMMARYA tomato strain of tobacco mosaic virus infected, on average, about half the cleaned seeds from infected fruits. The proportion differed with tomato cultivar, time of infection and truss. Virus content also varied; seeds usually carried TMV externally, in low concentrations, but about a quarter also carried it within the testa or the endosperm. High virus concentrations sometimes occurred internally, usually when the endosperm was infected. Internal infection decreased, mainly by absence of virus in the testa, as the plant age at the time of infection increased. Endosperm infection occurred mainly in fruits from flowers that set after the plants were infected. The proportion of fruits with seeds was smaller in early infected plants than in those infected later. Fewer necrotic, blackened seeds were obtained from late‐infected plants than from those infected earlier, and more necrotic seeds were infected with TMV than normal ones, especially in the endosperm. Although the embryo was sometimes contaminated during dissection, virus within it was never confirmed. Necrotic seeds often failed to germinate.Treating the fruit pulp with one‐quarter of its volume of conc. hydrochloric acid for 30 min. was the best means of cleaning seeds and of eliminating TMV carried externally. Fermentation and sodium carbonate extraction did not eliminate external TMV. Soaking previously cleaned seeds in 10% Teepol (Shell non‐ionic detergent) solution for 2 hr., or in a 10% tri‐sodium orthophosphate solution for 20 min. also inactivated external virus. The only treatment that often eliminated TMV carried internally was heating dry seeds in an oven at 70d̀C; treatment for 3 days was usually enough to free seeds completely but sometimes 3 weeks would not eliminate all virus, particularly that carried by the endosperm. Such treatments did not affect percentage germination of seeds other than recently harvested ones, but heated seeds sometimes took longer to germinate than unheated ones.TMV was lost within a few months in some stocks of seeds but persisted for at least 9 years in others with endosperm infection. Virus content of seeds fell rapidly for 2 weeks after sowing but then remained at a low level for many weeks. Plants never became infected when allowed to grow undisturbed after the seeds were sown. ‘Seed‐infectio’ occurred only when the seedlings were pricked out (transplanted) and the testas or remaining endosperm were rubbed against the seedlings. The proportion of plants thus infected was usually small because (1) many seeds did not carry virus; (2) virus was rapidly inactivated after sowing; (3) after normal sowing 65% of testas were left behind in the soil when the seedlings were pricked out; (4) very young seedlings resisted infection: and (5) infection was more likely with recently harvested than with older seeds, probably from TMV remaining on the testas. However, all seedlings which were infected, even with dilutions of TMV‐infected leaf sap leaf in water as low as one part in five millions, showed symptoms within 3–5 weeks.
Studies on resistance and tolerance to cocoa viruses in Ghana
Authors: ATTAFUAH ALEX. , GLENDINNING D. R. 
Published: February 2008

SUMMARYCuttings of twenty‐seven cocoa selections were infested with mealybugs (Planococcus njalensis) which had fed on plants infected with the New Juaben strain of cocoa swollen shoot virus. Susceptibility to infection with CSSV seemed to vary, and in general those selections which had appeared relatively resistant in earlier studies again appeared resistant. There were great differences in reaction to infection, clones from Scavina × unknown progenies being least affected while various other Amazon selections, particularly some from Iquitos × unknown and Nanay × Iquitos progenies, were also very tolerant. Some local Trinitario selections displayed a measure of tolerance. The tolerance results were similar to those previously obtained in Ghana with the same virus and using beans or seedlings, and also to those obtained in field trials and with budded material infected with Nigerian virus isolates.
The biology of Sclerotinia trifoliorum Erikss. and other species of sclerotium ‐forming fungi
Authors: WILLIAMS G. H. , WESTERN J. H. 
Published: February 2008

SUMMARYThe survival in soil of sclerotia of Sclerotinia trifoliorum, S. sclerotiorum, Sclerotium delphinii and S. rolfii was studied. Those of S. rolfsii disintegrated in less than 1 month, while 95% of those of S. delphinii and Sclerotinia sclerotiorum were recovered after 2 years.Sclerotia of S. trifoliorum placed in soil in March slowly diminished in numbers over the summer months, and in late autumn there was a rapid decrease in those near the surface, as a consequence of apothecial formation. This rapid fall did not occur when sclerotia were buried under clover. Over the winter, sclerotia 1 and 2 in. deep increased in numbers by the formation of secondary sclerotia. Secondary sclerotia also occurred in samples of Sclerotinia sclerotiorum.Soil moisture content affected sclerotial survival, an accelerating decline in numbers being noted up to a soil moisture‐holding capacity of 30%. Above this level, increasing numbers of secondary sclerotia were formed, so that the numbers of sclerotia recovered were sometimes greater than those originally buried.Sclerotia became more liable to decay after producing apothecia, but they did not invariably disappear, and some were capable of forming two or possibly three crops of apothecia in successive years.
The detection of antifungal substances before and after infection of beans (Vicia faba L.) by Botrytis spp.
Authors: PURKAYASTHA R. P. , DEVERALL B. J. 
Published: February 2008

SUMMARYPrevious work showed that germ‐tube growth of Botrytis cinerea, but not of B. fabae, is inhibited several hours after germination on the leaves. This study concerns the detection of substances in leaves and pods which could explain the different responses of the two fungi.Ether and methanol extracts of leaf surfaces were not inhibitory to either fungus. Drops of water which were incubated for periods up to 48 hr. on healthy leaf surfaces became slightly inhibitory to germ‐tube growth of both fungi. However, drops of water containing spores of B. cinerea became highly inhibitory after incubation on surfaces of leaves or in seed cavities of pods for 72 or 24 hr. respectively. Drops containing spores of B. fabae and water controls became stimulatory to test spores after incubation for 24 hr. in pods but slightly inhibitory after 72 hr. on leaves. The inhibitory substances were partially extracted from collected drops into petroleum ether. Substances soluble in petroleum ether extracted from the endocarp of pods were highly inhibitory to test spores 24 hr. after infection by B. cinerea but stimulatory before infection or 24 hr. after infection by B. fabae.
The effect of some fungicides and herbicides on ascospore production of Venturia inaequalis (Cke.) Wint.
Authors: HUTTON K. E. , BURCHILL R. T. 
Published: February 2008

SUMMARYThe ascospore productivity of severely scabbed apple leaves was reduced by 93.7–99.9% by a single autumn application of phenylmercuric chloride (PMC) over a concentration range of 0.0025–0.1%. Phenylmercury dimethyl‐dithiocarbamate (PMD) was slightly less effective at equivalent concentrations of mercury. Of the non‐mercury compounds tested, only high concentrations of didecyldimethylammonium bromide and the herbicide diuron approached PMC in effectiveness. Low concentrations of PMC applied in the spring reduced the numbers of ascospores released from leaves bearing mature perithecia.A new technique for estimating the ascospore productivity of overwintered apple leaves is described.
Studies on two races of Bremia lactucae Regel
Authors: CHANNON A. G. , WEBB M. J. W. , WATTS L. E. 
Published: February 2008

SUMMARYTwo races of Bremia lactucae are described; race W.1, which can attack various lettuce varieties now being grown commercially but cannot attack the resistant lettuces bred at Wellesbourne, and race W.2, which can infect not only the market varieties but also some of the W.1‐resistant lines. Race W.2 was shown to arise directly from race W.1, possibly by mutation.The length of incubation time from inoculation to sporulation of the mildew in lettuce leaves decreased as the number of spores applied in the inoculum increased. This fact was used to assess the concentration of race W.2 spores in naturally occurring spore populations, by comparing the effects on W.1‐resistant plants of graded dilutions of spores from the field with those of known concentrations of race W.2. These tests showed that race W.2 was most prevalent where W.1‐resistant lettuces had been grown for some years. Race W.2 spores were found, however, where no W.1‐resistant lettuces had been grown, and it appears that race W.2 may be a normal constituent of most Bremia populations. The importance of these findings in relation to future breeding for downy mildew resistance is discussed.
The influence of volatility and water solubility of systemic insecticides on their movement through soil and absorption by plant roots
Authors: BURT P. E. , BARDNER R. , ETHERIDGE P. 
Published: February 2008

SUMMARYWhen applied in the soil at the time potato tubers were planted, phorate and disulfoton were more effective than dimethoate and menazon in controlling aphids on the foliage of the crop in dry years, but all four were equally effective in wet years. The reason was sought by comparing the ability of the roots of wheat seedlings to absorb these systemic insecticides from air and from water. When absorbed from solution in water, all four insecticides were almost equally effective in killing Rhopalosiphum padi fed on the leaves, but when the roots were in contact only with the vapours of the insecticides, phorate and disulfoton were much more effective than dimethoate or menazon. This is thought to be the first demonstration that sufficient of the vapours of systemic insecticides can be absorbed by the roots of a plant to render the leaves toxic to insects feeding on them.These results and the physical properties of the insecticides suggest that only insecticides as volatile as phorate and disulfoton can move through dry soil to the roots of plants, and that even in moist soil phorate and disulfoton probably move mainly through the air rather than through the soil water. The more soluble and less volatile dimethoate and menazon are probably absorbed in amounts able to make the foliage toxic to aphids only when they can move to the roots through water.
The movement of 32 phosphorus ‐ labelled dimethoate in the cacao tree, Theobroma cacao L.
Authors: DUNN E. , WARD A. H. 
Published: February 2008

SUMMARYThe movement and persistence of the systemic insecticide dimethoate and its metabolites in the cacao tree have been studied by the use of radio‐phosphorus in Rogor 40.In trunk‐injection experiments only 11% of the insecticide entered effectively into the tree and of this 83% remained within 1 ft. of the point of injection. The remainder was quickly translocated upwards but was unevenly distributed in the canopy.Uptake of dimethoate from soil into the stem and branches proceeded continuously but slowly and was much less than from injections.In mature pods, over 86% of the dimethoate was found to be degraded into non‐toxic metabolites: thus there is little hazard from dimethoate residues in cacao beans.
The distribution of Myzus persicae (Sulz.) on year‐round chrysanthemums
Authors: WYATT I. J. 
Published: February 2008

SUMMARYFour cultivars of chrysanthemum (B.G.A. Tuneful, Giant No. 4 White Indianapolis, Bluechip and Yellow Princess Anne) were infested with Myzus persicae (Sulz.) in an insect‐proof glasshouse. Four weeks of rapid reproduction led to temporary overpopulation, but the mean density was soon regulated to a constant level by the production of alatae. When the density was highest, the same proportion of alatae was produced in all regions of the plants and on all cultivars, regardless of population density at the site of eclosion. This was thought to be due to the rapid state of flux in the entire population.Pronounced varietal differences developed in the size and distribution of populations, Tuneful supporting six times as many aphids as Princess Anne. Vertical distribution of aphids on the plants differed not only with cultivar, but also according to the population density and the developmental stage of the plant. A complete redistribution occurred as the density stabilized, revealing further varietal characteristics. The youngest leaves were always the most attractive to the aphids, and preference was frequently shown for their upper surface, particularly on Princess Anne.Short days had little direct effect on the behaviour of the aphids. The induced flowering, however, brought inevitable changes in aphid distribution; populations tended to move upwards towards the flowers, resulting in small, damaged and infested blooms.
The influence of temperature on the spread of aphid‐borne potato virus diseases
Authors: GABRIEL W. 
Published: February 2008

SUMMARYAir temperature is one of the most important factors influencing the spread of potato viruses in Poland. High correlations of leaf‐roll infection with accumulated air temperatures for the period I January‐30 April, and of infection with virus Y with accumulated air temperatures for the period 1 January‐10 July were obtained. On this basis the expected areas of different incidence of potato virus diseases were delimited in Poland. The correlation of mean infection for 4 years and mean accumulated temperatures for 15 years was higher than for the particular years, and the proportion of the total variance accounted for by regression exceeded 60%.The differences in the spread of both the viruses are discussed.
Contrasting effects of resistant and susceptible tomato plants on tomato mosaic virus multiplication
Authors: DAWSON J. R. O. 
Published: February 2008

SUMMARYMultiplication of tomato mosaic virus (strain of tobacco mosaic virus) in susceptible and in resistant tomato plants was studied by assaying the infectivity and virus content of sap from non‐inoculated leaves on infected plants. In susceptible plants, infectivity and virus particle number increased rapidly to a maximum at about 14 days after inoculation; leaves produced subsequently contained less virus. In resistant plants, no virus was detected in non‐inoculated leaves until 5 weeks after inoculation. Infectivity then gradually increased at a somewhat higher rate than did numbers of virus particles. The concentration of virus in resistant plants remained lower than in susceptible ones. At first the ratio of infectivity to particle number was larger for samples from the susceptible than the resistant line, but the ratio from the resistant line increased slowly until it eventually equalled that from the susceptible one.Virus cultured in either of two lines of tomato with different types of resistance invaded healthy plants of either line more readily than virus cultured in the susceptible variety. Resistant lines seem to select self‐invasive new forms of tomato mosaic virus.
The assessment of populations of Thrips nigropilosus Uzel. on pyrethrum
Authors: BULLOCK J. A. 
Published: February 2008

SUMMARYA satisfactory method of collecting samples of Thrips nigropilosus was developed in which only the mature leaves were collected, and a number of plants were sampled across several rows of the plot. This give a reproducible and representative estimate of the population within the plot.Despite the development of this technique, very great differences remained between counts on plots of a Latin square experimental design. The use of covariance analysis considerably reduced the residual variance when populations were increasing arithmetically or at only slightly increased rates. When the increase became more rapid, the value of covariance diminished rapidly while simultaneously positional effects became more significant, suggesting that restraining influences were operating unequally in different parts of the experimental area. It is considered that this phenomenon is widespread in populations of T. nigropilosus and that, as expanding populations are the most likely to be subject to experiment, a more complex design, probably of the incomplete block type, should be used in future.
A comparison of some quantitative methods of extracting small vermiform nematodes from soil
Authors: WHITEHEAD A. G. , HEMMING J. R. 
Published: February 2008

SUMMARYWhen 200 ml. dispersed soil is sedimented from an obliquely rising water current in a simple compartmented tank about three‐quarters of the nematodes are extracted. About 95% of the nematodes in the concentrated suspension can be separated finally from mineral and heavy organic particles by centrifugal notation. When mobile nematodes were finally separated from soil particles by paper tissue, this sedimentation method extracted as many nematodes from sand and loam as Seinhorst's two‐flask and elutriation methods, but in one test extracted fewer Tylenchorhynchus from clay and in another fewer Paratylenchus from clay than the elutriation method. The method is quicker (4 or 6 instead of 30–45 min.) and easier.Mobile nematodes can be extracted from 300 ml. soil spread out on paper tissue in 23. 33 cm. trays of 8 mesh/cm. phosphor‐bronze gauze, just resting on shallow water. The suspension obtained after 24 hr. at 16–18°C. was concentrated to 10–15 ml. without loss by sedimentation in two tapered cylinders, one of 8 cm. bore, the other of 2.6 cm. bore. This method usually extracted significantly more nematodes than the sedimentation, two‐flask and elutriation methods.
The epidemiology of tomato mosaic IX. Transmission of TMV by birds
Authors: BROADBENT L. 
Published: February 2008

SUMMARYHouse sparrows (Passer domesticus L.), confined in a cage with separate groups of TMV‐infected and healthy tomato plants, infected fifty of the 262 healthy plants by flying between the groups and perching on the plants. None of 191 healthy plants in an adjoining or the same cage without birds was infected. Thus birds could possibly spread TMV within crops and from one crop to another.
Effect of soil amendment with chitin on pea wilt caused by Fusarium oxysporum f. pisi
Authors: BUXTON E. W. , KHALIFA O. , WARD V. 
Published: February 2008

SUMMARYChitin applied to soil naturally infested with F. oxysporum f. pisi greatly lessened the severity of wilt in Onward peas, sown at the time the chitin was applied to the field. In the glasshouse, different pea varieties sown in the field soil 8 months after the chitin was applied were protected equally against infection by any of the three races of the fungus. The severity of wilt decreased with increasing amounts of chitin added to the soil.Applying chitin to artificially inoculated soil a month before pea seedlings were planted in pots also greatly diminished the severity of wilt.Adding chitin to soil decreased the population of Fusarium and increased the number of actinomycetes. Many of the actinomycetes were antagonistic towards Fusarium.
Further studies on the effect of aldrin and three other chlorinated hydrocarbons on clubroot of summer cabbage
Authors: CHANNON A. G. , FLINT ANNE E. , HINTON R. A. L. 
Published: February 2008

SUMMARYField tests were made of the four chlorinated hydrocarbon insecticides, aldrin, dieldrin, endrin and telodrin, applied as pre‐planting root dips with a methyl cellulose sticker. None of the treatments controlled the disease as effectively as a root dip in a 10% suspension of pure calomel, but they generally caused less initial growth check, resulting in some instances in significantly higher yields at maturity.Evidence that dieldrin and endrin had greater activity against clubroot than aldrin and telodrin was obtained in glasshouse experiments. This was confirmed in laboratory tests where it was also shown that the first two chemicals either eliminated or markedly reduced root hair infection of cabbage seedlings at a concentration as low as 0.1 p.p.m.
Eyespot in wheat after four‐course rotations and 3 1/2‐year leys
Authors: HEARD A. J. 
Published: February 2008

SUMMARYIn a long‐term ley‐fertility experiment, on old arable land, the treatments include various 3 1/2‐year leys and an arable four‐course rotation—barley, fodder‐beet, barley, undersown with a 1‐year ley. The yields of winter wheat following most of the 3 1/2‐year leys are higher than after the arable rotation. To determine whether this is partly due to disease, the wheat was examined in 1957, 1958, 1959 and 1961 for soil‐borne diseases, mainly eyespot (Cercosporella herpotrichoides) and take‐all (Ophioboltis graminis).Very little take‐all occurred. The amount of eyespot was negligible in 1957. In the other years, examination of the wheat suggested that the amount of eyespot in the soil was low during 1‐year leys and hayed 3 1/2‐year leys, and during grazed 3 1/2‐year leys not receiving nitrogen fertilizer, but possibly not during grazed 3 1/2‐year leys receiving heavy dressings of nitrogen. The 1‐year leys were probably as good as the 3 1/2‐year leys at controlling eyespot. The main factor affecting the level of eyespot in the wheat appeared to be the level of mineral nitrogen in the soil under the wheat. In wheat not receiving nitrogen fertilizer, between 4 and 24% of the culms bore eyespot. When the wheat received 78 lb. N per acre after the 1‐year ley of the arable rotation, up to 49% of the culms bore eyespot; and when the wheat received 52 lb. N per acre after heavily‐manured grazed leys (the residues of which contained much mineralizable nitrogen), up to 60% of the culms bore eyespot. Nevertheless, the increases in mineral nitrogen increased the yields of wheat.Although the wheat yields were probably not depressed by eyespot, the large amount of eyespot associated with some treatments, notably where both the 3 1/2‐year grazed leys and the subsequent wheat received nitrogen fertilizer, was potentially important to the survival of the disease.
Low‐volume spraying to control coffee leaf rust in Kenya
Authors: FIRMAN I. D. , WALLIS J. A. N. 
Published: February 2008

SUMMARYIn a 2‐year trial on arabica coffee in Kenya, a cuprous oxide fungicide (50% Cu) at a range of 0–5% (w/w) was applied by mist‐blower five times a year at approximately 10 gal./acre.The results demonstrated: (i) a positive linear relationship between log. spray concentration and the amount of copper (expressed as log10 mg. Cu/m.2+1) retained by the foliage; (ii) a significant negative linear relationship between spray concentration and the incidence of leaf rust (caused by Hemileia vastatrix Berk. & Br.); (iii) a positive linear relationship between concentration of fungicide applied and yield of coffee.An additional spray in May increased the mean annual yield by 2 cwt. coffee per acre and reduced a heavy rust attack.Trees receiving the highest spray concentration retained the most leaves; at lower concentrations there was considerable leaf fall but this was offset by new leaf production; unsprayed trees suffered severe leaf loss and were unable to produce as much new foliage.