bluuebunny/crossref_metadata_2025 huggingface dataset:
Eyespot in wheat after four‐course rotations and 3 1/2‐year leys
Authors: HEARD A. J.
Published: February 2008

In 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

In 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.
A growth study of sugar beet treated with gibberellic acid and (2‐chloroethyl)trimethylammonium chloride (CCC)
Authors: HUMPHRIES E. C. , FRENCH S. A. W.
Published: February 2008

Gibberellic acid sprayed on sugar‐beet plants decreased leaf production, whereas (2‐chloroethyl)trimethylammonium chloride (CCC) applied to the soil increased it. These changes were associated with a change in shape of the growing point; GA elongated it and CCC flattened it. Leaf area per plant increased to a maximum of about 28 dm. at the end of June; CCC consistently decreased it, but GA had no effect although the plant had fewer leaves than the controls. GA increased petiole length in the first part of the season but later diminished it. Petiole length increased with amount of GA applied. CCC had the opposite effect, decreasing petiole length at the beginning of the season and afterwards increasing it.

Total dry matter of plants treated with GA was significantly increased at harvests 3 weeks and 8 weeks after initial application. CCC‐treated plants had less dry matter throughout. GA increased crown dry weight and the effect increased with the amount applied. Neither GA nor CCC significantly influenced the weight of storage root. Plants overwintered in an unheated glasshouse continued to increase in dry matter; GA increased the weight of flowering stems but CCC had no effect.

From observations on individual leaves mean leaf area growth curves for successive groups of five leaves were constructed. Gibberellic acid increased both areas and longevity of leaves 8 to 17 and GA‐treated plants had the same dry weight as controls in spite of fewer leaves, because leaf area duration was increased. This study emphasizes that different leaves contribute very differently to the total dry matter of the plant. Each of leaves 8–17 had an average duration of 22 dm.2‐weeks and together they produced about two‐thirds of the final dry matter in autumn. CCC decreased leaf area duration and dry matter. None of the treatments changed net assimilation rate (E). In previous experiments with mustard plants CCC decreased E, either through a direct inhibitory effect of CCC on photosynthesis or through decrease in photosynthesis because the dwarfed stem in the treated mustard provided only a small sink for photosynthates. In sugar beet CCC does not affect E, possibly because the root provides a large sink.

The differences between sugar beet and potato in development of leaf area and production of dry matter are discussed and the importance of leaf area duration emphasized.

GA affects sugar beet and potato differently. It hastens leaf senescence in potato but delays it in sugar beet. GA may prolong the life of sugar‐beet leaves because by making them fewer it decreases competition between them. Gibberellic acid causes a transient increase in leaf growth and dry‐matter production both in sugar beet and potato.
Powdery mildew of tobacco (Erysiphe cichoracearum DC.)
Authors: COLE J. S.
Published: February 2008

Percentage germination, and growth of hyphae from single conidia of Erysiphe cichoracearum DC., were measured on leaf discs from topped and intact tobacco plants, grown in aerated nutrient solutions consisting of basal medium plus large or small amounts of potassium. The effect of supplying sodium was also studied. Discs were incubated on water and on 10% sucrose solution. Changes in free amino nitrogen and carbohydrate in comparable uninfected leaf discs, before and after incubation, were also measured.

Potassium deficiency resulted in more free amino nitrogen and soluble carbohydrate and less insoluble carbohydrate, per cm.2 of leaf. Spore germination was not greatly affected by treatments, though it was usually less on discs from potassium‐deficient leaves. The pathogen grew slower on potassium‐deficient leaf discs, whether they were incubated on water or on sucrose.

Incubating discs from some leaves on sucrose, compared with water, gave greatly increased sugar content and less fungal growth; discs from other leaves had a much smaller increase in sugar, and hyphal length was similar to that on discs incubated on water.

Sodium, when potassium was scarce, increased potassium deficiency symptoms, free amino nitrogen and sugar content, and resistance to powdery mildew.
Studies on the fungitoxicity of captan
Authors: RICHMOND D. V. , SOMERS E.
Published: February 2008

The uptake of captan from aqueous solution by conidia of Neurospora crassa can be markedly reduced by pretreatment of the cells with thiol reagents such as iodoacetic acid (IOA). The nature of this reaction has been investigated and it is shown that IOA largely reacts with the soluble thiol pool of the spores. Captan, however, reacts with both soluble and insoluble thiols and it is suggested that whilst the former is a detoxication process the latter may provide the key to its toxic action.

Using glutathione as a model soluble thiol the molar ratio and pH dependence of the captan detoxication process has been determined and compared with the cellular reactions. Assay of 35S‐labelled captan has shown that captan is almost completely decomposed by the spores and that one‐third of the accumulated captan is converted to sulphur compounds fixed to insoluble cell entities.
Studies on photosynthesis in the ear of wheat
Authors: LUPTON F. G. H. , ALI MOHAMED A. M.
Published: February 2008

Estimates of varietal differences in photosynthesis by ears of wheat, obtained by shading ears or stems, are compared with estimates obtained from a technique involving removal of spikelets at anthesis. The results obtained by different techniques and in different seasons differed widely.
The effects of nitrogen, phosphorus, potassium and magnesium on the growth of tulips during the second season of treatment and on the chemical composition of the bulbs
Authors: CHEAL W. F. , WINSOR G. W.
Published: February 2008

In factorial nutrition treatments, for a second season, with three rates of nitrogen, phosphorus and potassium, and some additional treatments with magnesium, on two bulb sizes of Golden Harvest and Elmus tulip, the effect of nitrogen was again found to be dominant. Nitrogen deficiency decreased bulb yields, leaf area, stem length (with one exception) and flower size; it also retarded flowering: the majority of small nitrogen‐deficient bulbs produced only single leaves.

Deficiencies of phosphorus, potassium and magnesium had more marked effects than in the first season of treatment and generally reduced bulb yields and leaf area; in some instances stem length and flower size were also reduced. High phosphorus advanced the flowering of Elmus bulbs.

The relationships between nutrition and mineral composition of the bulbs showed consistent trends determined by rates and duration of treatments, planting size and variety.
Studies on plant growth‐regulating substances: XXI. The release of pectic substances from wheat coleoptile tissue incubated with solutions of ethylenediamin etetraacetic acid
Authors: TAYLOR H. F. , WAIN R. L.
Published: February 2008

The effect on excised wheat coleoptiles of solutions of ethylenediaminetetraacetic acid, at concentrations which produce a significant growth response in segments of this tissue, was investigated.

The removal not only of calcium ions, but also of pectin, from coleoptiles by these solutions of the chelator was demonstrated and the implications of these findings are discussed. An increase in the plasticity of the cell walls is considered to arise from the removal of both of these constituents, and the small extension of the coleoptile segments to be a direct consequence of these changes.

The concentration of EDTA required to give either the growth‐regulating response or to cause the loss of pectin and calcium was shown to approach that which also caused visible signs of toxicity, and this was taken as further support for the ‘subacute toxicity’ theory put forward earlier by Fawcett, Wain & Wightman.
The residual effect of previous nutritional treatments on the growth and composition of tulips supplied with complete nutrients in sand culture
Authors: CHEAL W. F. , WINSOR G. W.
Published: February 2008

Tulip bulbs produced in sand culture with three rates each of nitrogen, phosphorus and postassium in factorial combination were subsequently grown for one season with complete nutrients in order to study the residual effects of the previous treatments. The bulbs included the progeny of large (II cm). and small (7 cm.) Golden Harvest after one season of differential nutritional treatments and of large Golden Harvest (II cm). and Elmus (12 cm.) after tow such seasons.

The early stages of growth, became less apparent by early March, but many of the bulbs previously deprived of nitrogen produced only single leaves and no flowers. The favourable effect of nitrogen on the weights of Golden Harvest bulbs was less marked at lifting than at planting time, but remained highly significant. The yield of Elmus bulbs showed particularly marked responses to both nitrogen and phosphorus. Other residual effects included decreased leaf area of bulbs previously deprived of nitrogen and phosphorus, and slightly earlier flowering with increasing levels of nitrogen.

Growth in complete nutrient solution decreased the differences in amounts of major nutrients in the bulbs. The percentage of nitrogen in Golden Harvest bulbs, and of phosphorus and potassium in both varieties, nevertheless increased significantly with the levels of these nutrients in the previous seasons.
A field experiment in Ghana on the tolerance of cocoa seedlings to cocoa swollen‐shoot and cocoa mottle‐leaf viruses
Authors: GLENDINNING D. R. , LEGG J. T. , LOVI N. K. , MARTINSON VERONICA A.
Published: February 2008

Seedings of Amelonado Cocoa and of two progenies obtained by crossing Iquitos (Upper Amazon) parents were infected with three strains of cocoa swollen‐shoot virus (CSSV) and with cocoa mottle‐leaf virus (CMLV). CSSV strain I A had the most severe effects on the growth and canopy condition of all varieties. All four virus isolates had more effect on the growth of Amelonado than on the Iquitos progenies, except that CSSV strain I W affected the growth of Amelonado and one of the Iquitos progenies equally, as did CMLV which caused the greatest decrease in the first crop of all varieties. The relative virulence of different CSSV strains in any one variety can be assessed from single criteria such as length of latent period or effect on growth; CMLV had a shorter latent period than CSSV Strain I A but less effect on growth.
The effect of soil insecticides on the predators and parasites of the cabbage root fly (Erioischia brassicae (Bouché)) and on the subsequent damage caused by the pest
Authors: COAKER T. H.
Published: February 2008

Field experiments on the effect of residues of aldrin and dieldrin in the soil on the beetle predators of the cabbage root fly, showed that populations of adult carabid and staphylinid predators were altered by aldrin/dieldrin residues at concentrations of 0.06 p.p.m. and above. The lower insecticidal concentrations were aged residues which had become intimately mixed with the soil. Although the residues reduced the numbers of trapped Aleochara spp., concentrations below 0.5 p.p.m. increased the numbers of Bembidion lampros, probably because their movement was stimulated by the insecticide. Harpalus spp. and Feronia spp. were unaffected by residues below the concentration toxic to cabbage root‐fly eggs and larvae. The reductions of the predators implied by the trapping records increased the survival of the cabbage root‐fly eggs and larvae, thus leading to augmented damage to cauliflowers, cabbage and Brussels sprouts, which resulted in reductions in yield of up to 70%.

Larval and pupal parasitism by Aleochara spp. and Idiomorpha rapae were also reduced by the insecticide residues, although concentrations of 0.2 p.p.m. and above were required to decrease parasitism by I. rapae.
The control of Alternaria species on leaves of sugar beet infected with yellowing viruses
Authors: RUSSELL G. e.
Published: February 2008

Leaves of virus‐free sugar‐beet plants rarely became infected with Alternaria spp. in two field experiments at Cambridge in 1965. Infection with beet yellows virus (BYV) increased susceptibility of plants to Alternaria only slightly but infection with beet mild yellowing virus (BMYV) increased it greatly. There was a close association between the severity of Alternaria symptoms, shown by different breeding lines and varieties of sugar beet, and the losses of sugar yield which they sustained after infection with BYV and BMYV. Many lines and varieties were resistant to Alternaria even when infected with BMYV and their resistance seemed to be inherited as a dominant character. Individual plants of any one line or variety differed greatly in resistance to Alternaria, suggesting that selection should improve the present level of resistance.

Spraying the foliage of Alternaria‐susceptible varieties with fungicides had little effect on the severity of Alternaria symptoms or on sugar yield. This was probably because the wet summer of 1965 was ideal for the spread of Alternaria and because rain washed the fungicide deposits from the sprayed leaves.
Powdery mildew of tobacco (Erysiphe cichoracearum DC)
Authors: COLE J. S.
Published: February 2008

A Hirst volumetric spore trap, at a height of 30 cm., was used to assess the diurnal distribution of Erysiphe conidia in the air in tobacco crops infected with E. cichoracearum in Rhodesia. Air temperature and humidity, and the length of time leaves were wet each day, were also recorded at the same height, amongst the plants. In four seasons, most conidia were caught between 13.00 and 15.00 hr.

There were close positive correlations in 1962 between numbers of conidia per m.3 of air per hour and saturation deficit and air temperature during the same hours (10.00–18.00 hr.) Correlations of total Erysiphe conidia per day with temperature and humidity were very variable; temperature had no apparent effect during three seasons, but in one (1961)there was a highly significant positive correlation between numbers of conidia and the daily duration of temperatures > 25d̀ C. More conidia were also caught when the air was dry for long periods that season, though temperature probably had the greater effect. In 1962, more conidia were caught per day the longer the air was humid (s.D. 0–1 mb.) In 1961, the amount of rain per day had no apparent effect on numbers of conidia, but in 1962 more were caught the greater the daily rainfall. However, rain, which nearly always fell in the afternoon, also removed most conidia from the air that afternoon. Neither windspeed nor duration of leaf wetness appeared to affect spore dispersion.
Glasshouse experiments on apple scab
Authors: MOORE M. H.
Published: February 2008

Dilutions of various fungicides were compared on potted MM 109 clonal rootstocks in the glasshouse for protective (pre‐infection) and curative (post‐infection) activity against apple scab. The materials, as commercial preparations, included captan, copper (as ‘dry’ Bordeaux mixture), dichlofluanid, didecyldimethylammonium bromide (DDAB), dispersible sulphur, dithianon, dodine acetate, lime‐sulphur (LS), phenylmercury chloride (PMC), and thiram; they were assessed on the basis of percentage active ingredient in the dilutions.

When acting at normal rates of use, many of the fungicides were much more effective protectively than curatively, but this contrast was less applicable to DDAB, dodine acetate, LS, and dichlofluanid. PMC, however, was an especially notable exception in proving curatively superior at unusually low rates. In addition, it was particularly active in vapour form, and was effectively translocated not only from one leaf surface to the other, but, especially at 0.005%, from sprayed to younger unsprayed leaves on the same shoots. Other standard fungicides showed little or no translocated activity, but isobutyl‐o‐coumarate was effective at the growing shoot‐tips in spring from a spray applied to the lower leaves.

PMC reduced infection when applied once at any time during the scab‐incubation period, and especially 24 hr. after infection, when the control was almost complete. Longer intervals before spraying reduced the curative action, but not in proportion to the intervals; the infection pattern showed multi‐peak fungicidal activity and, after the later sprays, many lesions were practically infertile. The curative properties of PMC were matched by several other formulated phenylmercury salts compared at equivalent percentage mercury content, but the dimethyldithiocarbamate proved rather less effective. A preliminary attempt to supplement the curative properties of PMC with the protective properties of LS, by mixing these fungicides at low rates, showed evidence of fungicidal antagonism, and this needs further investigation.

Several fungicides, notably the inorganic sulphurs, thiram, the phenylmercury compounds, dichlofluanid, and DDAB showed incidental activity against natural infection by powdery mildew.
The fungitoxicities of plant furocoumarins
Authors: MARTIN J. T. , BAKER E. A. , BYRDE R. J. W.
Published: February 2008

A mixture of the furocoumarins pimpinellin, isopimpinellin, isobergapten and sphondin isolated from Heracleum sphondylium root was toxic to Gloeosporium limetticola, Botryis cinerea, Sclerotinia fructigena and Stereum purpureum at 200 p.p.m. or less in nutrient medium. The extractive of the leaves of plants that contain furocoumarins suppressed in vivo growth of G. limetticola and B. cinerea at concentrations lower than the contents of the extractive in the leaves. Furocoumarins may form an important class of natural defensive agents against fungi; this possibility is discussed.
Modification of growth habit of Majestic potato by growth regulators applied at different times
Authors: DYSON P. W. , HUMPHRIES E. C.
Published: February 2008

The effect of gibberellic acid, CCC (2‐chloroethyltrimethylammonium chloride) and B 9 (N‐dimethylaminosuccinamic acid) was studied on growth of potato plants in pots. Growth was analysed on four occasions and changes in habit defined in terms of internode lengths, leaf areas and growth of lateral branches.

Soaking seed pieces for 1 hr. in GA solution caused six internodes to elongate greatly, an effect not prevented by CCC applied when the shoot emerged from the soil. The effects on internode extension were determined by the length of the interval between GA treatment and CCC treatment.

Treatment at emergence with CCC shortened all internodes and more CCC applied 4 weeks later had no effect. Late application of CCC or B9 shortened the top two lateral branches, usually very long in untreated plants.

The regulators affected leaf growth differently from internode growth: usually growth regulators had less effect on leaf growth.

Effects on growth depended on when the regulators were applied. Treatment with GA alone inhibited bud development at higher nodes than in untreated plants; when followed by late treatment with CCC, lateral growth at higher nodes was also less. CCC retarded development of lateral branches especially when applied early. B9 had a similar effect to CCC applied late. When regulators retarded growth of lower laterals, upper laterals often grew more than in untreated plants. Treatments did not affect the number of leaves on the main stem at first but later GA hastened senescence. GA increased the number of leaves on lateral stems, and the effect was enhanced by CCC. CCC alone increased the number of first‐ and second‐order lateral leaves. GA lengthened and CCC shortened stolons. The effect of CCC persisted throughout the life of the plant. CCC or B 9 shortened stolons whenever applied. CCC hastened tuber initiation but slowed tuber growth.

CCC at first retarded formation of lateral tubers but had no effect on the ultimate numbers of lateral and terminal tubers.

The value of E (net assimilation rate) did not alter with time. CCC applied at emergence increased E, probably because it hastened tuber initiation and temporarily increased sink capacity. Although tubers formed earlier with CCC, their growth was slower and their demand for carbohydrate was also less. The increase in second‐order laterals in CCC‐treated plants indicates that they utilize carbohydrate that would normally go to tubers.

This experiment also demonstrates that crowding leaves by shortening stems did not diminish E, possibly because another over‐riding process (bigger sinks) offsets the effect of shading.
Studies on plant growth‐regulating substances: Interactions between auxins and inactive analogues
Authors: GRIFFITHS J. , INTARAKOSIT P. , TAYLOR H. F. , WAIN R. L.
Published: February 2008

The growth‐regulating activities of four auxins were assessed in the wheat cylinder and pea segment tests, and the capacity of certain inactive analogues to act as auxin antagonists was examined. 2,4‐Dichlorophenylthioisobutyric acid was found to antagonize the auxin activity of 2,4‐dichlorophenylthioacetic acid and was more effective than the established antagonist α‐(i‐naphthylmethylsulphide)propionic acid in interaction experiments with 2,4‐D. Two auxins were studied with their respective sulphonamide analogues as antagonists and only slight reduction in growth‐regulating activity was observed. Interaction experiments with an auxin and its corresponding arsonic acid revealed no evidence of true competitive antagonism. The implications of these findings are discussed.
The effect of temperature upon intensity of colour in the coronas of cut blooms of narcissus var. Soleil d'Or
Authors: SMITH W. H. , PARKER J. C.
Published: February 2008

Cut blooms of narcissus Soleil d'Or were subjected to constant temperatures ranging from 1.2° C. to 18.3° C. both in darkness and under illumination. The rate of opening of successive florets, the rate and final degree of colour development of the corona and subsequent display life were observed.

Opening was negligible at 1.2° C. and 38 days were taken to open to five florets at 4.5° C. Full opening occurred in 4 days at 15.6° C.

The change of colour of the corona from yellow to orange was negligible at 15.6° C, but final intensity of orange colour increased with decreasing temperatures. Temperature affected colour development both of opened and unopened florets, and after treatment at low temperature colour continued to develop when the blooms were removed to 18.3° C. The period of low‐temperature treatment giving maximum colour development was 8 days.

Artificial illumination of intensity 200 ft.‐candles had little effect at 18.3° C. but it increased orange colouring at the lower temperatures.

Increased orange colour whether at intermediate or low temperature was shown to be associated with a slight increase in the concentration of the total carotenoids, but more especially with greatly increased content of β‐carotene which constituted approximately 10–20% of the total carotenoids.
The relationship between hypersensitive tissue and resistance in wheat seedlings infected with Puccinia graminis tritici
Authors: BROWN J. F. , SHIPTON W. A. , WHITE N. H.
Published: February 2008

Data obtained during the first 120 hr. of the infection process in several resistant and susceptible varieties of wheat infected with Puccinia graminis tritici did not show any consistent relationship between the growth of the rust colony and the rate of increase of host tissue showing hypersensitive necrosis. Furthermore, no apparent relationship existed between the area of the rust colony at any given time after inoculation, and the amount of hypersensitive necrotic tissue per unit area of the leaf colonized. Thus, it is suggested that hypersensitive necrosis of the host tissue is a consequence and not the cause of resistance of wheat to infection by P. graminis tritici.
The control of damping‐off in Pisum sativum L. by cycioheximide
Authors: AKINREFON O. A.
Published: February 2008

Experiments on the effect of cycioheximide (Acti‐dione) in controlling damping‐off disease of peas confirmed that phytotoxicity would preclude its use despite its high toxicity to Pythium spp.

The antibiotic did not inhibit germination of peas, but retarded growth of the shoot; the tap root was apparently unaffected, but the lateral roots were stunted.
Orientation of male Heterodera rostochiensis Woll. and H. schachtii Schm. to their females
Authors: GREEN C. D.
Published: February 2008

A chemical attractive to their males is emitted by females of Heterodera rostochiensis and H. schachtii. The attraction is evident in agar plates when the females have been killed or removed from the agar, and on 3 mm. thick agar it takes more than 15 min. at 20° C. to diffuse sufficiently to be perceptible to males 5 mm. from the females. The perception is gustatory and seems to elicit klinokinetic aggregation behaviour and klinotaxic orientation. The males respond to a decrease in stimulation by stopping, followed by either a reversal and turn, or a swing and turn. Fatigue of the receptors, leading to loss of acuity of perception, occurs at greater concentrations of the attractant and decreases the frequency of turning. Then the intensity of turning increases and the approach to the female is less well orientated. Females of H. schachtii secreted a less labile or more concentrated attractant; thus their males were more frequently less well orientated and removal of the females caused more direct attraction. Male behaviour was efficient enough to ensure mating even of isolated females.
The permeability of artificial windbreaks and the distribution of flying insects in the leeward sheltered zone
Authors: LEWIS T. , STEPHENSON J. W.
Published: February 2008

The number of flying insects in the sheltered zone to leeward of artificial windbreaks of 0, 25, 45 and 70% permeability was greater than in unsheltered areas. Insects accumulated in the air nearer to dense windbreaks than to more permeable ones, and the position of maximum aerial density of insects coincided with that of maximum shelter. The more dense the windbreak the greater the numbers in the air to leeward. Absolute wind speed slightly affected the position of maximum aerial density behind a 45% permeable fence.
Artificial windbreaks and the distribution of turnip mild yellows virus and Scaptomyza apicalis (Diptera) in a turnip crop
Authors: LEWIS T.
Published: February 2008

In a turnip crop natural infection with turnip mild yellows virus was greatest in two narrow zones, one to leeward of an artificial windbreak, the other in a long shallow depression in the earth. Both zones were approximately across wind when Myzus persicae flew in early summer. Later in the summer, similar windbreaks facing different prevailing winds increased the number of larvae of Scaptomyza apicalis on the plants immediately to leeward and windward of the windbreaks, probably because shelter affected adults that were flying and laying eggs in the crop.
Host range and some properties of groundnut rosette virus
Authors: OKUSANYA BOLAJOKO A. M. , WATSON MARION A.
Published: February 2008

Two isolates of groundnut rosette virus from East Africa (GRVE1 and GRVE2) and from West Africa (GRVW1 and GRVW2) were transmitted by Aphis craccivora obtained from West Africa. A third isolate from West Africa (GRVW3) was not transmitted by A. craccivora from three widely separated sources. GRVW1, GRVW2 and GRVW3 caused leaf‐symptoms in groundnut of a mosaic pattern in light and dark green. GRVE1 and GRVE2 caused chlorosis or chlorosis and leaf distortion as well as mosaic symptoms. Groundnut plants with GRVW1 could not be infected by means of aphids with GRVE1, and GRVE1 gave similar protection against GRVW1, which suggests that they are strains of the same virus.

All isolates were transmissible manually from groundnut to groundnut (Arachis hypogea), Trifolium incarnatum and T. repens, and caused systemic infection. Inoculated Nicotiana clevelandii and N. rustica developed symptoms but virus could not be recovered from them. Chenopodium amaranticolor, C. hybridum and C. quinoa showed local lesions on inoculated leaves. Virus could be acquired by aphids from groundnut or Trifolium repens infected by means of aphids, but not from those infected by manual inoculation. Virus could not be recovered from T. incarnatum manually or by aphids, but was transmitted by cleft‐grafting from clover to groundnut.

Saps extracted in borax buffer plus zinc sulphate at pH 9 from plants infected with GRVW1 and GRVE1 remained infective at 18° C. for 1 week, and at — 20° C. for up to 4 weeks. Virus could be recovered from frozen leaves. Buffered saps lost infectivity when heated above 50° C. for 10 min.; most were still infective when diluted 1/10 and some at 1/100.

Electron micrographs of partially purified preparations contained spherical particles 25–28 mμ in diameter. There were usually only about five per microscope field and they resembled those of some other viruses.
The influence of germinating seeds and developing roots on re‐establishment of micro‐organisms in fumigated soil
Authors: VAUGHAN E. K. , NEWHOOK J. F. , ROBERTSON G. I.
Published: February 2008

A laboratory study was made of re‐invasion of soils fumigated in closed containers at rates of 3 ml./sq.ft. 10 in. deep with chloropicrin, methyl bromide and a 67:33 mixture of the two materials (MBC–33), using the dilution plate method of determination. Counts after aeration, 3 weeks later, showed that all three fumigants eliminated practically all fungi. Chloropicrin and MBC–33 also killed almost all bacteria and actinomycetes, whereas fumigation with methyl bromide markedly increased numbers of bacteria without materially altering numbers of actinomycetes.

Subsequently, in soils fumigated with chloropicrin or MBC–33, fungi recolonized rapidly, but up to 93 % of the colonies isolated were Trichoderma viride. Increase of fungi in soils fumigated with methyl bromide was slower and Penicillium spp. predominated. Bacteria at first declined in numbers, then increased rapidly in soils fumigated with all three materials. In soils fumigated with methyl bromide, actinomycetes, usually considered to include good antagonists, increased but did not exploit their initial advantage over fungi. In soils fumigated with chloropicrin and MBC–33 actinomycetes did not recolonize in appreciable numbers.

The greatest variety of fungous genera occurred in isolates from rhizo‐spheres of red beet, but the greatest numbers of colonies of both fungi and bacteria were isolated from rhizospheres of pea and pumpkin. None of the crops tested greatly stimulated recolonization by actinomycetes. Compared with the drastic changes brought about by fumigants the influence of seed and root exudates on either the magnitude or the composition of re‐invading micro‐organisms was slight.
Uptake and binding of dodine acetate by fungal spores
Authors: SOMERS E. , PRING R. J.
Published: February 2008

Uptake of the dodine cation from acetate solutions by conidia of Alternaria tenuis and Neurospora crassa was characterized by a rapid rate of sorption, a ‘Langmuir type’ adsorption isotherm, and independence of temperature: all of which suggests an ionic bonding mechanism. Metal cations competed with dodine for the anionic binding sites of the cell—regarded as carboxyl and phosphate groups—and dodine uptake also decreased as ionization of the carboxyl group was suppressed.

Cell walls of A. tenuis had a greater capacity to bind dodine than did those of N. crassa. Binding at the cell wall may detoxify some of the large amount of dodine that must be accumulated by the spores to achieve toxicity. The dodine retained by N. crassa cell walls could not be exchanged or desorbed by washing and is probably bound covalently rather than by weaker ionic bonds. At sub‐lethal concentrations there was no evidence that dodine disorganized cell wall structure.

Disruption of spores which had been incubated with 14C‐labelled dodine showed the fungicide to be associated with intra‐cytoplasmic organelles. It is suggested that dodine reacts with the protoplast membrane so as to alter its permeability and allow more dodine to penetrate into the cytoplasm where it may destroy intracellular membrane structure.
The effect of some microphagous saprobic nematodes on mushroom culture
Authors: HESLING J. J.
Published: February 2008

When added to spawned mushroom compost the microphagous saprobic nematodes Pelodera cylindrica, Mesorhabditis spiculigera and Acrobeloides bütschlii did not affect mycelial growth or compost pH. The eelworms multiplied at first but their numbers declined as the mycelium colonized the compost. In contrast, the fungal‐feeding Aphelenchoides composticola increased rapidly and destroyed the mycelium. Excess water, and the presence of the fungal competitor of mushroom, Chaetomium olivaceum, allowed some increase of the microphagous forms. Different numbers of Mesorhabditis spiculigera added to the ‘casing’ had no effect on mushroom yield but the mushroom ‘flushes’ seemed less pronounced. Reasons for the failure of the saprobic eelworms to affect mushroom, and the possibility of synergistic pathogenicity by these eelworms and bacteria, are discussed.
The effects on a population of potato‐root eelworm (Heterodera rostochiensis) of growing potatoes resistant to pathotype B
Authors: COLE C. S. , HOWARD H. W.
Published: February 2008

The effects on a potato‐root eelworm (Heterodera rostochiensis Woll.) population of growing potatoes resistant to pathotype B of the eelworm were investigated. The eelworm population, which was originally nearly entirely pathotype A, had been changed into a mixture of pathotypes A, B and C before 1961, when the experiments described in this paper began, by growing potatoes resistant only to pathotype A.

The resistant potatoes grown in the years 1961 and 1962 were certain clones of the hybrid triploid species Solarium xjuzepczukii Buk., clones bred from S. multidissectum Hawkes with the gene H2 and clones bred from S. vernei Bitt. et Wittm. In the years 1963‐65 the clone used was D 40 which has both the gene H2 from Andigena and the gene H2 from 5. multidissectum and is resistant to both pathotypes A and B of the eelworm. The only potatoes which caused a reduction in the egg population were those bred from S. vernei. The clone D 40, although it had little effect on the egg population, appeared to have more resistance than could be accounted for from possessing genes H1 and H2.
Effects of infection with narcissus mosaic, narcissus yellow stripe and tobacco rattle viruses on the growth and flowering of narcissus cv. ‘Minister Talma’
Authors: REES A. R.
Published: February 2008

Three plots were planted with similar‐sized narcissus bulbs: healthy; infected with narcissus mosaic virus (NMV); and infected with narcissus yellow stripe + tobacco rattle virus (NYSV+TRV). No effects of infection were observed on flower number, diameter, paracorolla length or flower dry weight, but the flower stalks were shorter in the infected plants. NMV‐infected plants produced slightly blemished flowers, and 74% of the NYSV + TRV‐infected flowers were of poor quality. Virus infection delayed leaf growth and loss of bulb dry weight early in the season and senescence in July. NYSV+TRV‐infected plants were more affected than NMV‐infected plants. However, maximum leaf area was similar for all plants. The maximum plant dry weight and the final weight of the bulb were not significantly affected by infection, but small differences, which could be cumulative in successive years would not have been detected. Differences in net assimilation rate, if any, were small.
Bacterial canker of stone‐fruits: Infection experiments with Pseudomonas mors‐prunorum and P. syringae
Authors: CROSSE J. E. , GARRETT CONSTANCE M. E.
Published: February 2008

The effect was compared of inoculating Pseudomonas mors‐prunorum and P. syringae at high inoculum concentration through wounds in plum stems and cherry branches, and through cherry‐leaf scars. In the wound inoculations a North American cherry strain of P. syringae was considerably more virulent than any of three indigenous cherry strains of P. mors‐prunorum, but two pear strains of P. syringae were less virulent. P. mors‐prunorum showed a much greater capacity to invade through leaf scars, particularly towards the end of the leaf‐fall period, when all three P. syringae strains were largely ineffective. Evidence is discussed which suggests that the greater infectivity of the P. mors‐prunorum strains through leaf scars was related to their capacity to colonize the host tissues from small inocula. The P. syringae strains died out in cherry cankers earlier than P. mors‐prunorum strains and they were less stable during host passage. The results of the experiments indicate that virulence in these organisms is a complex phenomenon and determined by several factors.
Studies on the nutrition of Arthrobotrys oligospora Fres. and A. robusta Dudd: The predaceous phase
Authors: HAYES W. A. , BLACKBURN F.
Published: February 2008

The effects of substrate on the predaceous activity in sand cultures of two isolates of the genus Arthrobotrys were measured by expressing the number of non‐survivors of a free‐living nematode population exposed to the fungi for 4 days as a percentage of a comparable population of nematodes not exposed to predation. This percentage is designated the predacity number.

By varying the energy source it was shown that nutrient requirements for the extension of mycelium may differ from those for the expression of predacity. There is a greater reduction in the activity of A. oligospora when nitrogen is supplied as ammonium than when it is presented as nitrate or nitrite. The predacity of A. robusta is greatest on media deficient in biotin and with nitrite as nitrogen source.

The relationship of results derived from artificial cultures to results from more direct examination of soils is discussed.
Powdery mildew of tobacco (Erysiphe cichoracearum DC.): Susceptibility of proximal and distal parts of leaves from different stalk positions on intact and topped field plants in relation to free amino nitrogen and carbohydrate content*
Authors: COLE J. S.
Published: February 2008

The area covered by visible mycelium of E. cichoracearum on the upper surface of leaves 4, 8, 12 and 16 of tobacco plants in field plots in Rhodesia was expressed as percentages of the proximal and distal halves at weekly intervals. Free amino nitrogen and carbohydrate in discs from proximal and distal halves of the same leaves were analysed when each leaf was expanding rapidly and was not infected, and several weeks later, when the rate of expansion had slowed down and there was slight infection. On two other occasions, similar leaf discs were inoculated with conidia, to measure the percentage germination and hyphal length from individual conidia after incubation for 2–3 days at constant temperature and humidity; duplicate discs were chemically analysed.

Leaves were not susceptible until at least 6 weeks after they had emerged from the bud. Soluble carbohydrate increased and free amino nitrogen decreased during the change from resistance to susceptibility.

Proximal parts of leaves were usually infected first; they initially contained less amino nitrogen and soluble carbohydrate than distal parts. All parts of the leaf seemed to be equally susceptible later, when there were no differences in their amino nitrogen or soluble carbohydrate.

Upper leaves of intact plants had more natural infection than those from corresponding leaves from topped plants. More conidia germinated on discs from them and produced longer hyphae. The discs from intact plants contained less free amino nitrogen and more soluble carbohydrate than those from topped plants.

The accuracy of visual assessments of susceptibility was, generally, confirmed by measurements of percentage germination and length of hyphae from individual conidia on leaf discs.

Regressions of hyphal length on leaf composition showed that susceptibility was apparently related inversely to free amino nitrogen and water content and directly to insoluble carbohydrate per unit dry matter.
Properties of wilt‐toxins produced by Verticillium albo‐atrum Reinke & Berth.
Authors: STODDART J. L. , CARR A. J. H.
Published: February 2008

Cultures of Verticillium albo‐atrum grown in a liquid, mineral salts/sucrose medium, were harvested at daily intervals and subjected to gel‐filtration on Sephadex G‐25 columns eluted with demineralized water. Ultraviolet scanning of the eluate indicated a broad division into high and low molecular weight fractions (HMW and LMW). The HMW material was found to be a variable mixture of a protein component (M.W. c. 100,000) possessing mild cellulase activity, and fructosan (M.W. 5,000–10,000). Both components produced wilting in a lucerne detached‐leaf bioassay. Heat denaturation resulted only in the loss of the protein component with a corresponding reduction in wilt‐toxicity. A number of LMW components were found to produce leaf necrosis, but only in high concentrations and long‐duration assays. These were considered to be of doubtful significance in the wilt syndrome. The possible action mechanisms and the basis of resistance are discussed.
Cellulase activity of Polyporus betulinus
Authors: BELL M. K. , BURNETT J. H.
Published: February 2008

Methods are described for isolating and crossing monocaryons of P. betulinus and of determining their cellulase activity by observing changes in viscosity of a carboxy‐methyl cellulose preparation.

Cellulase activity, so measured, is not correlated with growth rate in the presence or absence of cellulose.

Cellulase activity is almost certainly controlled polygenically and is inherited independently of mating type.
Some observations on size and biological activity of spray deposits produced by various formulations of copper oxychloride
Authors: EVANS E. , COX J. R. , TAYLOR J. W. H. , RUNHAM R. L.
Published: February 2008

Chemical estimations and biological assays, using Botrytis fabae, of spray deposits on beans (Vicia faba) in the laboratory have shown that the amount of an initial spray deposit of copper oxychloride is dependent on the volume of application used per unit area and the concentration of copper in the spray liquid. The addition of 0.1 % of an anionic surfactant (dioctyl sodium sulpho‐succinate) greatly reduced the amount of these initial deposits although another anionic surfactant did not. In the laboratory trials the fungitoxicity of the spray deposit was related to the actual copper levels initially present. In general, the addition of surfactants improved the fungitoxicity of the initial deposit.

The addition of surface‐active agents did not materially affect the rain‐resistance of the spray deposits, while their presence in emulsions of PVA, PVC and PVB gave an improved biological performance. All three polymeric materials greatly improved the tenacity of copper oxychloride spray deposits without reducing their fungitoxicity in laboratory tests.

When examined in field experiments against potato blight (Phytophthora infestans) these apparent biological advantages due to the tenacity and good distribution of the polymeric emulsion formulations did not materialize. An explanation for this apparent contradiction between laboratory and field data has been given based on certain features of the epidemiology of the pathogen.
The relative toxicity and persistence of insecticides applied as water‐dispersible powders against stored‐product beetles
Authors: PARKIN E. A.
Published: February 2008

Twelve insecticides, formulated as water‐dispersible powders, were applied to strips of filter paper and their toxicities to eight species of stored‐product beetles were determined. The insecticides were DDT, methoxychlor, lindane, aldrin, dieldrin, synergized pyrethrins, malathion, fenthion, Chlorthion, diazinon, trichlorphon and carbaryl. The insects were adults of Sitophilus granarius (L.), S. zeamais Mots., Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.), Stegobium paniceum (L.), Lasioderma serricorne (F.), and Ptinus tectus Boield. Tables of LD 50 values are presented in terms of deposits of active ingredient between the limits investigated, namely 0.625 and 80 mg./sq.ft., for 2‐day and 3‐day periods of continuous exposure at 25d̀ C. and 70% R.H. The data give a broad view of the susceptibility of each insect species to the different insecticides, the effectiveness of each insecticide against the range of insect species, and the speed of action of the insecticides. Trichlorphon had a very low toxicity to all species except O. surinamensis and was omitted from further testing.

Deposits of the remaining eleven water‐dispersible powders on filter paper were stored and tested at intervals up to 16 months. This yielded information on the persistence of the formulations after application to a chemically inert substrate. Five of the insecticides‐malathion, fenthion, Chlorthion, diazinon and carbaryl were then investigated for their persistence on cement, tile, whitewash on tile, wood, and sacking. This test revealed loss of effectiveness of some of the organophosphorus insecticides because of volatility or of alkalinity of the substrate, although some of the results obtained with tiles were difficult to explain. Factors such as surface activity, porosity and real surface area may have played a role, as well as the physical state of the insecticide in the formulation.