bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatic factors restricting the distribution of the aphid Rhopalosiphoninus latysiphon to the subterranean parts of field potato plants
Authors: GIBSON R. W.
Published: February 2008

Rhopalosiphoninus latysiphon (Davidson) infests the roots of field potato plants, but it is normally absent from the foliage. In cool conditions it is possible to rear this aphid on the foliage of potato plants. From experiments, it is suggested that R. latysiphon does not normally infest the foliage because it does not tolerate the high air temperatures and the radiant heat to which it would be exposed; a damp environment is also preferred. These are probably the main causal factors in the aphid's selection of a subterranean environment.
The ecology of Erwinia rubrifaciens and the development of phloem canker of Persian walnut
Authors: SCHAAD N. W. , WILSON E. E.
Published: February 2008

A requisite for development of bacterial phloem canker caused by Erwinia rubrifaciens is the presence of the highly susceptible Hartley cultivar; when interplanted with Hartley, the Franquette and Payne cultivars are sometimes attacked by the disease. The recently developed cultivars, Gustine and Howe, developed active cankers when inoculated, but not as extensive as those in Hartley. The age of the plant part is important in the disease. One‐year‐old Hartley trees and twigs of the current season on mature trees did not develop active cankers. The complete disease syndrome occurs only on trunks and primary (scaffold) branches. Extension of the cankers was most rapid during the summer when the temperature was high. This was correlated with the effect of temperature on growth of the bacterium in culture. At midday in summer the temperature of the cambial area of a shaded trunk was as much as 10d̀F (5.6 d̀C) below ambient temperature but it was commonly a few degrees above ambient at night.

Breaks in the thick phelloderm of the trunks and branches are necessary for penetration of the pathogen to the inner bark. Of the several types of breaks commonly occurring, those produced by mechanical harvesting equipment and by sap‐sucking birds were found to be infection sites. Bacteria occur in large numbers in a slimy substance which exudes through cracks and accumulates on the bark of infected trees. They survived for at least 123 days in the exudate and were disseminated laterally as far as 20 ft (6.1 m) in wind‐blown rain. Bacteria were also transmitted from tree to tree in exudate contaminating the pads of mechanical harvesting equipment.
Stabilization, culture and some properties of tulip halo necrosis virus
Authors: MOWAT W. P.
Published: February 2008

Tulip halo necrosis virus, obtained from tulips with leaf necrosis, is very labile in crude sap but can be transmitted consistently by inoculating Nicotiana clevelandii plants with extracts made in pH 8 phosphate buffer containing a stabilizing agent such as 0.2M 2‐mercaptoethanol or 0.01M dithiothreitol. Of the fifteen species in five families of Angiosperms infected by inoculation with sap, few are suitable as sources of inoculum. Cultures of the virus can be maintained in Nicotiana clevelandii kept at 14 or 18d̀C but not at 21d̀C. Infectivity can be assayed in Chenopodium quinoa, in which necrotic local lesions are produced. Stabilized extracts of leaves were infective at a dilution of 1/16 but rarely at 1/32, and infectivity decreased disproportionately with dilution. Infectivity of all extracts was abolished in 10 min at 50d̀C and of some at 45d̀C, but survived when extracts were clarified using diethyl ether or trichlorotrifluoroethane. The virus was not transmitted by the aphid Myzus persicae.
Differences in the probing behaviour of Elatobium abietinum feeding on Sitka and Norway spruces
Authors: PARRY W. H.
Published: February 2008

The probing behaviour of Elatobium abietinum (Walk.) on the needles of Norway spruce and Sitka spruce was directly related to the stomatal frequency accompanied by heavy deposition of saliva, and multiple branching and divergence of the salivary sheath, all of which were associated with the impenetrability of the endodermis. On Norway spruce these features were very greatly reduced where there was a higher rate of probing coupled with a higher rate of penetration into the phloem, which was not accompanied by early uptake of phloem sap when compared with aphids on Sitka spruce. These differences in probing behaviour are related to damage symptoms exhibited by the host trees.
A strain of radish mosaic virus occurring in turnip in Yugoslavia
Authors: ŠTEFANAC ZLATA , MAMULA D.
Published: February 2008

Fields of turnip (Brassica rapa L. var. rapa) in Yugoslavia often contained plants infected with radish mosaic virus (RaMV). Yugoslav isolates resemble the type strain in host range, symptoms, physical properties, particle morphology and flea‐beetle transmission and are serologically closely related to the type strain, but did not infect radish and are designated as the European strain. Light microscopy of infected turnip and some other cruciferous species revealed the characteristic inclusion bodies in the cytoplasm.
The effects of soil fumigation and nitrogen fertilizers on nematodes and sugar beet in sandy soils
Authors: COOKE D. A. , DRAYCOTT A. P.
Published: February 2008

In fifteen experiments on light land infested with plant‐parasitic nematodes, fumigating the soil during the previous winter with D‐D increased the average yield of sugar‐beet roots from 25 to 36 t/ha; this was more than that obtained with various forms of nitrogenous fertilizers used in amounts up to 250 kg N/ha. Application of 85 kg N/ha increased yields on fumigated plots by 7 t/ha, and there was little benefit from giving more. Fumigation killed 65 % of the Pratylenchus spp., 80% of the Trichodorus spp. and 90% of the Tylenchorhynchus spp. in the top 5 cm of the soil and, at 15–20 cm deep, 90, 93 and 95% of these three genera. The increased yield from fumigant at different sites was not correlated with the initial populations of nematodes. The average increase in yield from fumigation was only poorly correlated with rainfall during May. The increases in nematode populations between April and August depended on rainfall, and were 0positively correlated both with the accumulated rainfall for the 10 weeks before sampling the soil in August and with the rainfall during the week previous to sampling. Fumigation not only improved the health of roots, and so enabled them to use nitrogen more efficiently, but also increased the amount of available nitrogen in the soil and decreased the amount lost by leaching. Injected anhydrous ammonia did not affect the populations of nematodes.
Glandular hairs providing resistance to aphids in certain wild potato species
Authors: GIBSON R. W.
Published: February 2008

Glandular hairs occur abundantly on Solanum polyadenium, S. tarijense and S. berthaultii. An exudate is discharged from the glandular hair when an aphid mechanically ruptures the cell walls. On contact with atmospheric oxygen, a chemical reaction is initiated in which the clear, water‐soluble material contained in the hair changes to a black insoluble material which is precipitated on the aphid's limbs. This initially impedes its movements and further accumulations eventually stick the aphids to the plant so that they are immobilized and starve to death. In experiments described, about 30 % of infesting aphids were completely immobilized within 24 h. The potential value of this source of resistance to aphids, if incorporated into the cultivated potato, is discussed, especially with reference to the advantages of its being combined with other forms of resistance and to its effectiveness against virus vectors.
Differences in susceptibility to attack by Brevicoryne brassicae (L.) on brussels sprouts
Authors: DUNN J. A. , KEMPTON D. P. H.
Published: February 2008

The attack by alate and other forms of Brevicoryne brassicae (L.) and the amount of leaf malformation they caused on each of eighteen varieties or plant breeders' lines of brussels sprout were assessed in both 1967 and 1968 over the first 6 weeks following planting out. The results of the two years agreed closely despite differences in the dates of planting relative to aphid immigration. As a group, the Dutch varieties Roodnerf, Gravendeel, Tribune, Hercules and Castricum Glory were preferred by the incoming alates but suffered less damage than the least preferred inbred line, 3BL, of Cambridge No. 3. Some evidence of antibiosis was obtained, especially from a later experiment with three Cambridge inbred lines. However, in 1969 when there was a high rate of aphid multiplication on six varieties representing sprout types from Holland, Cambridge, Bedford and Ireland, any expression of host non‐preference or antibiosis was soon obscured by the development of large aphid infestations and much damage. Under these circumstances, considerable varietal differences in tolerance to attack were found. Irish Elegance sustained most damage yet its most heavily attacked plants supported little more than half of the aphid numbers of equivalent plants of the most tolerant variety Darkmar 21. The Dutch varieties Vremo Inter and Seven Hills were almost as tolerant as Darkmar 21 and recovered quickly from damage. Darkmar 21 also showed high tolerance to attack in 1970, as did the Dutch varieties Rollo, Roodnerf and Stiekema, when large aphid infestations developed on the eight varieties then grown. Lack of plant tolerance to damage appeared to be associated with incurling foliage, a characteristic of Irish Elegance, Cambridge No. 1 and No. 3.
Studies on a further race (W. 4) of Bremia lactucae Regel
Authors: CHANNON A. G. , HIGGINSON YVONNE
Published: February 2008

A further race (W. 4) of Bremia lactucae was identified in a sporangial collection from an infected field crop of the cultivar Avondefiance by tests on detached seedlings and leaf disks of various diagnostic lettuce cultivars. Race W. 4 appeared to be unstable, with a similar host range to race W.3, but differed from it in its inability to infect the crisp‐lettuce cultivars Grand Rapids, Calmar, Caravan, Francisco and Great Lakes.

Races W. 1, W. 2 and W. 3 were also found in tests starting with the sporangial collection from Avondefiance. Although W. 3 could have been present in small quantities in this original collection, it was considered that W. 1 and W. 2 arose spontaneously from W. 4 during subculturing.

A means of eliminating W. 2 from mixtures of W. 1 and W. 2 is described.

A laboratory experiment indicated that when competing in a crop of Avon‐defiance or Cobham Green, race W. 2 might predominate over race W. 3.
Resistance to attack by Brevicoryne brassicae among plants of Brussels sprouts
Authors: DUNN J. A. , KEMPTON D. P. H.
Published: February 2008

Because they remained almost uncolonized by the cabbage aphid (Brevicoryne brassicae (L.)) throughout the growing season, plants of Brussels sprouts were singled out in each of 4 years, from plots heavily infested with the aphid, as possibly being resistant to attack. Clones of these plants were established from cuttings and tested in a controlled environment by inoculation with B. brassicae and later, in the field, by natural infestation. The tests confirmed that some of the plants were resistant to the aphid, and the most resistant of those from the first year of the work proved at least as resistant as any subsequently found. The resistance was expressed as antibiosis, but in the field host non‐preference was also shown by incoming winged aphids.

The possibility that biotypes of B. brassicae might exist, to which the resistant sprout clones were not necessarily resistant, was investigated using B. brassicae collected from sprouts from each of several areas in England. Eight sprout clones, seven of which were known to be resistant, and the other susceptible, to B. brassicae from Wellesbourne were tested with these other B. brassicae. The results showed that biotypes of the aphid, with differing abilities to colonize respective sprout clones, existed in each area, and of the seven sprout clones resistant to the Wellesbourne aphid, only one appeared never to be fully susceptible to one or more of the other biotypes of B. brassicae.
Control of Fusarium solani rot of potato tubers with fungicides
Authors: MURDOCH ANNE W. , WOOD R. K. S.
Published: February 2008

Tecnazene (up to 33 ppm) and dichloran (up to 500 ppm) had little effect on germination of spores or growth of Fusarium solani isolated from and causing a rot of potato tubers; they also did not decrease rotting when applied to wounds later inoculated with the pathogen.

Benomyl and thiabendazole (up to 500 ppm) also had little effect on spore germination but did greatly decrease growth at 5 ppm. A pronounced pink coloration developed in cultures growing slowly in the presence of benomyl; a similar though less striking effect appeared in agar cultures containing thiabendazole.

Benomyl suspended in water or diluted with Fuller's earth gave good control of rotting when applied to wounds inoculated later with F. solani. Still better control was obtained with thiabendazole; dusts containing 1% a.i. substantially decreased rots and those containing 10 % a.i. gave almost complete control when applied to wounds shortly before inoculation. Thiabendazole was also very effective when used 24 h after inoculation and a fair measure of control was obtained when it was applied 24 h later.

Benomyl and thiabendazole placed on apparently intact surfaces of tubers caused tissue 5 mm deep to become toxic to F. solani 10 days later, and, unexpectedly, this tissue prevented spore germination.

Fuller's earth alone substantially decreased rotting.

The results obtained suggest that dusts containing thiabendazole have some promise for the control of Fusarium rots of potato tubers, especially of early crops.
Chemical control of potato cyst‐nematode in sandy clay soil
Authors: WHITEHEAD A. G. , FRASER JANET E. , STOREY G.
Published: February 2008

In sandy clay soil in Bedfordshire, potato cyst‐nematode (Heterodera rostochiensis Woll.) was controlled and yields of Majestic potatoes greatly increased when i‐2g aldicarb, 4‐0 g fensulphothion or 10‐3 g diazinon, disulphoton, ‘Isolan’ (i‐isopropyl‐3‐methyl‐5‐pyrazolyl dimethylcarba‐mate) or thionazin per m2 were incorporated in the top soil before potatoes were planted. Diethyl phosphorothioates controlled H. rostochiensis better than dimethyl phosphates. One hundred and eleven g methyl bromide, 47‐6 g carbon disulphide or 45‐2 g D‐D per m2 applied to the soil and covered with polyethylene sheeting greatly increased the yield of potatoes, but also increased the number of nematodes in the soil. Estimates of the number of larvae able to invade potato roots in treated soil after harvest and of cysts, total eggs or live eggs selected the same range of treatments as effective in controlling H. rostochiensis.
Interference by common leaf saprophytic fungi with the development of Phoma betae lesions on sugarbeet leaves
Authors: WARREN R. C.
Published: February 2008

When sugarbeet leaves were inoculated simultaneously with the parasitic Phoma betae and the saprophytic Aureobasidium pullulans or Torulopsis Candida, the development of expanding lesions caused by P. betae was curtailed. Two other common saprophytes, Sporobolomyces pararoseus and Cladosporium cladosporioides, also decreased numbers and sizes of expanding lesions in the presence of pollen. The numbers of saprophyte cells applied to inoculum areas were similar to those occurring naturally on sugarbeet leaves in the summer.

Lesion development was not affected by a mixture of heat‐killed cells of the four saprophytes.
Field experiments on potato aphids and virus spread in South Wales 1966/9
Authors: WEBLEY D. P. , STONE L. E. W.
Published: February 2008

In 1966‐9 the spread of leaf roll and severe mosaic (Virus Y) was investigated in seed and ware areas in South Wales. The use of disulfoton granules at planting time greatly reduced the spread of leaf‐roll virus in both areas but had less effect on the spread of severe mosaic. Foliar sprays with formothion did not reduce the spread of either virus. Practical considerations are briefly discussed.
Effect of staking, nitrogen and potassium on growth and development in lesser yams: Dioscorea esculenta
Authors: ENYI B. A. C.
Published: February 2008

Dry‐matter accumulation was greater in staked than in unstaked plants of the lesser yam (Dioscorea esculenta). Staking, N and K application tended to increase the proportion of dry matter diverted into the tubers. Staking was the most important factor in increasing total tuber production, which was one and a half times greater in staked than in unstaked plants. Leaf‐area development was closely and positively related to vine growth, and since staking and N application encouraged vine growth these treatments therefore led to the production of plants with greater leaf area. Leaf‐area duration was increased by staking and N application and was closely and positively related to tuber yield. Staking and N application increased tuber number per plant while K application increased the size of individual tubers. Staking and K application increased bulking rate and both treatments increased the period of bulking by causing earlier tuber initiation.
The effects of windbreaks on the blossom‐visiting fauna of apple orchards and on yield
Authors: SMITH B. D. , LEWIS T.
Published: February 2008

Windbreaks of coir netting were erected in apple orchards during the flowering period in 1969 and 1970 in an attempt to increase the number of insect pollinators present. Suction traps were used to sample flying insects; insects visiting trees were sampled by examination of flowers. The sheltered zone behind the windbreaks contained more of most species of insects than elsewhere. Increases in final fruit set of approximately 30% in 1969 (cv. Cox's Orange Pippin) and 20 % in 1970 (cv. White Jersey) occurred in trees receiving maximum shelter, and these were due mainly to the increased abundance, and possibly increased activity, of honey bees there. Fruit size was not reduced where yields were increased.
The timing of sprays for the protection of terminal buds on apple shoots from powdery mildew
Authors: BUTT D. J.
Published: February 2008

Post‐blossom sprays of fungicides, repeated at 10‐day intervals until leader (syn. extension) shoots had stopped producing new leaves, provided the best protection of terminal buds against Podosphaera leucotricha on the apple cv. Lane's Prince Albert. Spraying was most effective in early summer, although many of these buds were not invaded until later, when the rate of shoot growth declined; applications from July to September did not compensate for the enhanced infection which followed interruptions of the post‐blossom programme between late May and early July. This early period was critical because most leaf infections occurred then, and because this phase of the epidemic on foliage determined the eventual intensity of mildew on terminal leaves, and hence the inoculum available for infecting terminal buds. Also, many lateral shoots ceased growth early and their apices were directly protected by sprays applied in June. Applications after early June were too late to protect newly formed fruit buds on spur branches.
Secondary leaf fall of Hevea brasiliensis: factors affecting the production, germination and viability of spores of Colletotrichum gloeosporioides
Authors: WASTIE R. L.
Published: February 2008

The optimum temperature for growth and sporulation of Colletotrichum gloeosporioides from Hevea brasiliensis was between 26 and 32 oC, whereas spore germination exceeded 90% between 21.5 and 30.5 oC. Germination decreased in culture after 3 days, and on exposure of spores to sunlight or oven heat (46 oC) for 10 min.

Spore viability and germination were sensitive to atmospheric humidity; at 99% r.h. germination was half that at 100% r.h. and was negligible below 97% r.h. Germination decreased by up to 30% after 3 h storage at 80% r.h. Continuous light favoured spore production in vitro, but spores produced in the dark had a higher percentage germination.

No differences were detected between the numbers of spores germinating on leaves of different ages, although there were slightly more on susceptible cultivars and in the presence of extracts of uninfected susceptible leaves. Extracts from, infected leaves depressed spore germination, as did concentrations above 5 times 105 spores/ml. The highest % germination was observed when naturally infected leaves were dry‐stored for up to 20 days and then incubated for 2 days in a moist chamber.
Tobacco yellow vein, a virus dependent on assistor viruses for its transmission by aphids*
Authors: ADAMS A. N. , HULL R.
Published: February 2008

Tobacco yellow vein, a disease found in Malawi, is caused by a combination of two viruses transmitted in the persistent manner by aphids. One component, tobacco yellow vein virus (TYVV) is manually transmissible, but aphids transmit it only from plants also containing the other (assistor) component, which is not manually transmissible. Aphids also transmit TYVV from plants containing either of two other assistor viruses ‐ tobacco vein‐distorting and groundnut rosette assistor. A virulent isolate of TYVV infected Soja max, Arachis hypogaea and several solanaceous species. It infected plants already containing tobacco mottle or groundnut rosette viruses but not those containing a mild isolate of TYVV.
The effects of rainfall and shade on the occurrence of three mite pests of tea in Ceylon
Authors: DANTHANARAYANA W. , RANAWEERA D. J. W.
Published: February 2008

Outbreaks of the red spider mite (Oligonychus coffeae Nietn.), the purple mite (Calacarus carinatus Green) and the scarlet mite (Brevipalpus californicus Banks) of tea were closely associated with the monthly rainfall pattern. Peak numbers occurred during the intermonsoonal dry periods. The relationship between mite numbers and the rainfall pattern suggests that control measures should commence at the end of the first month after the dry season begins. More red spider mites, but fewer purple mites, occurred on tea grown under shaded conditions. Observations on the relationship between scarlet mite numbers and shade were inconclusive. It is suggested that, in addition to direct effects of rainfall and shade, mite numbers are determined by certain biochemical processes that take place within the tea leaves.
Races of Colletotrichum lindernuthianum and implications for bean breeding in Uganda
Authors: LEAKEY C. L. A. , SIMBWA‐BUNNYA M.
Published: February 2008

Nineteen local isolates of the bean anthracnose pathogen have been obtained and tested over the period 1964–70 for pathogenicity on a set of differential cultivars including the sets of four cultivars each used in the alternative systems of Schreiber and Hubberling and of Bannerot and Blondet. The results indicate the existence of a number of races not conforming to those of either system and the ability, when freshly collected, of some isolates with affinities to both α and β races partially to overcome the immunity of the cultivar Cornell 49–242. The implications of the position as now known from these results and a review of the literature for disease‐resistance breeding are discussed. Tests of the Uganda isolates, on a range of other dry bean cultivars, indicate a tendency for α and δ races to be pathogenic on small‐seeded indeterminate viny or indeterminate bush cultivars, whereas β and γ races tend to be pathogenic on larger‐seeded and determinate cultivars.
Effects of fungicides on the populations of Colletotrichum and other fungi in bark of coffee*
Authors: GIBBS J. N.
Published: February 2008

The effects of copper, captafol and Tuzet, applied to coffee in early season (January to April) and in other programmes continuing through the long rains (January to July), on the bark populations of Colletotrichum cofleanum Noack. (the pathogenic CBD strain and the saprophytic ccm, cca and ccp strains), Phoma spp., Fusarium stilboides Wollenw. and a Phomopsis sp. were investigated on branch material from field experiments in Kenya in 1968 and 1969 by a plating technique which estimated sporulating capacity (s.c.)

Fungicide application initially caused a non‐specific reduction in s.c., Tuzet being the most effective. With the onset of the long rains this general reduction was not maintained, although during the period between the long and short rains the levels of many fungi in sprayed plots were still below those in the unsprayed control. In contrast, the s.c. of Phoma in plots sprayed with copper and of Phomopsis in those sprayed with Tuzet were higher than on unsprayed plots. The S.C. of the CBD strain was below that in the control only in plots sprayed with captafol.

Effects were still evident after the short rains. Some early‐season programmes of all three fungicides increased the s.c. of the CBD strain while continuing programmes of copper and captafol reduced its S.C. relative to that on unsprayed trees. Differences in S.C. at this time were related to infection in the early crop a few weeks later.

The initial antisporulent effect of a fungicide appears less important than its persistence and its effect on bark colonization by the different fungi. Early‐season sprays of copper, formerly used to control CBD, may have contributed to an increase in disease hazards by affecting the primary level of the pathogen.
The effects of topping and plant population on dry matter synthesis and distribution in Brussels sprouts
Authors: JONES L. H.
Published: February 2008

The effects of topping at different dates, and of different plant populations on dry‐matter production and distribution in Brussels sprouts were studied. Total dry‐matter production per unit area was unaffected by either topping or density. Leaf area was decreased by topping, resulting in a temporary increase in net assimilation rate. Topping resulted in a redistribution of dry matter; that which would have formed new stem and leaf tissue was directed into sprout production.

Increasing plant density did not affect the distribution of dry matter but increased the number of smaller sprouts. The apparent optimum plant spacing in this series was 21×21 in (53×53 cm). At maturity assimilation approximately balances respiration.
Some effects, especially on yield, of artificially defoliating sugar beet
Authors: DUNNING R. A. , WINDER G. H.
Published: February 2008

The effects of completely defoliating sugar beet at different dates from May to October were examined in four years. In each year there were plots given the usual nitrogen fertiliser application to the seedbed, and also in two of the years plots given no nitrogen.

At harvest in mid‐November, minimum root weights followed defoliation in July or August, but defoliation in August or later gave minimum sugar contents. When nitrogen was applied to the seedbed sugar yields were smallest after August defoliation; in the absence of nitrogen, July defoliation gave the lowest sugar yields, root yield being smaller but sugar content usually greater than with nitrogen. Up to 40% of the sugar yield was lost by July or August defoliation and late defoliation increased some of the impurities in the root juice. Yields, and recovery from defoliation, were greater with nitrogen than without. Partial defoliation in May had relatively little effect on yield. Defoliation affected the incidence of virus yellows differently in different years.
The diurnal periodicity and cycle of behaviour of the adult cabbage root fly (Erioischia brassicae)
Authors: HAWKES C.
Published: February 2008

Adult cabbage root fly (Erioischia brassicae (Bouché)) exhibited a diurnal periodicity in behaviour. Trapping tests indicated that the flies fed from hedgerow flowers in the morning, visited the crop in the early afternoon and returned to the hedges in the late afternoon. In the laboratory the flies also showed a cyclical pattern in behaviour. Feeding preceded oviposition by 3 days and this was reflected in the field by a relative increase in the movement of females away from the hedges and to the crop when they became gravid. The diurnal periodicity and the cycle in behaviour of males was similar to that of the females, indicating that some of the flies' movement was non‐appetitive.

The tendency of flies to stay for most of the day at hedges resulted in progressive declines in the numbers captured with increasing distances from hedges.
Evaluation of fungicides for the control of Verticillium wilt (V. dahliae) of strawberry
Authors: JORDAN V. W. L.
Published: February 2008

The treatment of soil or plants before planting, in September 1969, significantly reduced Verticillium wilt on strawberry in the following season. One application of benomyl or thiabendazole (both 0–5% a.i.) at 6728 l/ha to soil 24 h before planting, dusting roots with formulated benomyl powder (50% a.i.) at planting, or a combination of both benomyl dust + drench treatments were effective. However, although the double treatment gave the most disease control in 1970, plants from the soil‐drench treatments gave the highest yields.

Residual effects of the 1969 applications were still evident in 1971 from increased vigour, lack of wilt and high yield, especially with the benomyl treatments.
Feeding and the uptake of phosphamidon by two strains of Myzus persicae (Sulz.) on radish plants
Authors: HALIMIE M. A. , FORD J. B.
Published: February 2008

Intraspecific differences in the uptake of solutions containing phosphamidon, enclosed in Parafilm membranes, have previously been demonstrated in Myzus persicue. This paper shows that similar differences also occur when the aphids are fed on treated plants. Uptake from phosphamidon‐contaminated plants is reduced though the effect was quantitatively different in the two strains of aphid studied. The depression in the level of feeding was related to the concentration of insecticide applied to the plant.
Sclerotinia minor on lettuce: progress of an epidemic
Authors: JARVIS W. R. , HAWTHORNE B. T.
Published: February 2008

Analyses of disease progress curves of lettuce drop, caused by Sclerotinia minor, indicate that early infected plants sometimes provide inocula for later secondary spread within the crop, there sometimes being evidence of plant‐to‐plant spread. It is suggested that primary infections are attributable to aerially dispersed ascospores, produced by germinating sclerotia which are soil‐borne, and that secondary plant‐to‐plant spread is associated with mycelial inocula.
Investigations on fungicides: XIV. Fungitoxicity of N‐(2,2,2–trichloro‐1–methoxyethyl)‐formamide and related compounds
Authors: CARTER G. A. , SUMMERS L. A. , WAIN R. L.
Published: February 2008

From a study of forty compounds related to the systemic fungicide N,N'‐bis(1–formamido‐2,2,2–trichloroethyl)‐piperazine, known as triforine (CELAW524), it was found that a new compound, N‐(2,2,2–trichloro‐1–methoxyethyl)‐formamide, controls Erysiphe graminis on wheat when applied to the roots in sand. A number of N‐(2,2,2–trichloro‐1–aryloxyethyl)‐form‐amides and alkyl N‐(2,2,2–trichloro‐1–arylaminoethyl)‐carbamates protect broad beans against Uromyces fabae and wheat against Erysiphe graminis; some of these formamides show slight activity when applied to plant roots.
Take‐all in spring‐sown cereals under continuous cultivation: disease progress and decline in relation to crop succession and nitrogen
Authors: SHIPTON P. J.
Published: February 2008

Incidence and severity of the take‐all disease in spring wheat and spring barley caused by Gaeumannomyces graminis (syn. Ophiobolus graminis) were studied during seven years of monoculture.

The fungus apparently survived for much longer periods in the soil under non‐susceptible break‐crops than previously recorded. The incidence and severity of infection increased progressively with each successive cereal crop from initially low levels to a maximum within 3–7 years, which was followed by a progressive but limited decline in the disease. Spring wheat was more susceptible to take‐all than spring barley and the development of take‐all decline (TAD) was recorded earlier in the sequences of wheat than of barley crops. Nitrogen did not influence the disease until the point of maximum incidence and severity, when it caused a reduction in disease levels in addition to that associated with TAD. Factors influencing the time of onset and the rate of development of take‐all and of TAD are discussed and possible explanations for TAD are suggested.
Further experiments on photosynthesis and translocation in wheat
Authors: LUPTON F. G. H.
Published: February 2008

A model is deveolped relating photosynthesis taking place in successive layers of the canopy of a wheat crop to the intensity of the radiation incident on the crop, the elevation of the sun, and to the angle to the horizontal and photosynthetic area of ears, leaves and leaf sheaths. The validity of the model is tested by comparing the rate of photosynthesis, pattern of translocation and solid geometry of a semi‐dwarff wheat (TL 365a/25) with those of a variety of conventional height (Cappelle‐Deprez). The model gives realistic estimates of crop yield and indicates that the greater yield of the semi‐dwarf selection is caused by faster photosynthesis, despite less photosynthetic surfaces of ears and leaves. It also indicates that selection for erect leaves may lead to further increases in yield.
The effect of replacing potassium by sodium on cation uptake and transport to the shoots in four legumes and Italian ryegrass
Authors: WHITEHEAD D. C. , JONES L. H. P.
Published: February 2008

White clover, red clover, lucerne, sainfoin and Italian ryegrass were grown in a series of culture solutions in which 0, 25, 50, 75 and 100% of the potassium was replaced by sodium. In the shoots, the potassium: sodium ratios indicated selectivity for potassium which decreased in the order: sainfoin>lucerne>red clover>white clover > Italian ryegrass. In the roots only sainfoin showed selectivity for potassium: with the other species the ratio of potassium to sodium in the roots was similar to that in the other species the ratio of potassium to sodium in the roots was similar to that in the culture solution. All species showed selective transport of potassium to the shoots in preference to sodium: this was least in Italian ryegrass and white clover and greatest in sainfoin, which in contrast to other species also showed restricted transport of potassium to the shoots. Replacement of potassium by sodium slightly increased the magnesium concentration in the shoots but had no effect on the calcium concentration.
Attempts to define and mimic the effects of pollen on the development of lesions caused by Phoma betae inoculated onto sugarbeet leaves
Authors: WARREN R. C.
Published: February 2008

Expanding lesions resulted when conidia of Phoma betae Frank, mixed with rye pollen, were inoculated on to sugarbeet leaves by a standard technique. Conidia without pollen generally caused non‐expanding necrotic spots; these could be made to spread later by covering them with pollen or orange juice, but not with water.

Germ‐tube growth was quicker on water agar than on sugarbeet leaves. Pollen extract stimulated germ‐tube growth on leaves 10 h after inoculation and resulted in the production of knots of hyphae overlying areas where intercellular hyphae could be discerned and where expanding lesions developed.

Some inorganic salts mimicked the stimulatory effect of pollen on germtube growth on agar slides, but only a mixture of hexose sugars with boric acid reproduced the effect of pollen on both numbers and size of expanding lesions caused by P. betae on sugarbeet leaves, and numbers of expanding lesions caused by Botrytis cinerea Pers. ex Fr. on bean leaves.
Infection of stored celery plants by Centrospora acerina
Authors: DAY J. R. , LEWIS B. G. , MARTIN SUSAN
Published: February 2008

Chlamydospores in tissue near the bases of plants and in attached soil particles were the main form of inoculum of Centrospora acerina (Hartig) Newhall found on celery plants prepared for storage. Most of these spores remained ungerminated for several weeks but subsequently formed germtubes, terminal appressoria and infection‐pegs, which usually penetrated the plant surface through either the intact cuticle or damaged areas. For several weeks after the beginning of storage the plants were highly resistant to infection. During this time, appressoria failed to penetrate the intact cuticle and, if the fungus entered through damaged areas, hyphal growth in tissue was suppressed. Infection was often found to be associated with abrasion or splitting of the cuticle in commercially stored plants and, in experiments, deliberate damage enhanced the probability of infection. The development of the disease was much slower at 2 d̀C than at 15 d̀C.
Systemic action of benomyl against late‐wilt disease of maize.
Authors: SABET K. A. , SAMRA A. S. , ABDEL‐RAHIM M. F.
Published: February 2008

Benomyl (methyl‐I‐(butyl carbamoyl)‐2‐benzimidazole carbamate) at 2.5 to 100 ppm completely inhibited the growth in vitro of Cephalosporium maydis Samra, Sabet & Hingorani, the causal fungus of late‐wilt of maize. In pot experiments, late‐wilt was controlled by applications equivalent to 10 ppm benomyl/unit wt dry soil at sowing but not by applications 30 days after sowing or by seed treatments (dusts and dips). A fungitoxic substance was detected in benomyl‐treated soil, planted with maize, 120–150 days after treatment and for 150–180 days in unplanted soil. Sap expressed from maize grown in benomyl‐treated soil was also fungitoxic, especially that from the roots and distal parts of the leaf blades.

In the field, soil applications of benomyl to 10 kg/feddan (4200 m2) failed to control late‐wilt. Tests indicated little fungitoxicity in the sap of maize plants 25 days after sowing.
Strain‐genotype interaction of tobacco mosaic virus in tomato
Authors: PELHAM J.
Published: February 2008

The symptoms and virus content of isogenic tomato genotypes differing by three tobacco mosaic virus (TMV) resistance factors, Tm‐I, Tm‐2 and Tm‐22, were studied in relation to various isolates of TMV and four strains were identified. The common strain induced no symptoms on plants with any of the factors for resistance, one strain caused symptoms on Tm‐I plants, one on Tm‐2 plants and one on both Tm‐I and Tm‐2 plants and also on Tm‐I Tm‐2 plants. No strain induced symptoms on Tm‐22 plants.

The gene, Tm‐I, was found to be dominant or incompletely dominant for preventing symptom development but was recessive or intermediate for limiting virus multiplication of the common strain. Both Tm‐2 and Tm‐22 were dominant for a hypersensitive response to the common strain. Virus multiplication was temperature‐dependent. The background or varietal genotype did not affect virus multiplication.

A systemic necrosis of Tm‐22 plants occurred only when heterozygous Tm‐22 was not protected by other factors against specific strains of TMV.

The complexity of the host genotype, pathogen genotype and environment interactions are outlined and the exploitation of the resistance factors in tomato breeding discussed.
Serological relationship and detection of bean common and bean yellow mosaic viruses in agar gel
Authors: UYEMOTO J. K. , PROVVIDENTI R. , SCHROEDER W. T.
Published: February 2008

Microprecipitin tests demonstrated a distant serological relationship between intact virus particles of BCMV and BYMV. Antiserum titres of 2048–4096 and 16–128 (reciprocals of dilution end‐points) were found for homologous and heterologous antigens, respectively. Cross‐reactivity, however, was not obtained in agar immunodiffusion tests when the antigens, in purified preparations or crude infective sap, were treated with pyrrolidine or when the reactants were placed in agar gels containing sodium dodecyl sulphate. Only homologous antigens produced a precipitin line; homologous antiserum titre was 16.

In comparative immunodiffusion trials, single‐radial‐diffusion tests (antiserum incorporated in agar) were much more sensitive than double‐diffusion tests for detecting low virus concentrations.

Analyses of virus proteins by polyacrylamide‐gel electrophoresis demonstrated that coat protein of each virus was composed of a single polypeptide chain with a molecular weight of 35000.
Effects of growth regulators on fruit abscission in oil palm, Elaeis guineensis
Authors: CHAN K. W. , CORLEY R. H. V. , SETH A. K.
Published: February 2008

By delaying harvest of fruit bunches of the oil palm Elaeis guineensis Jacq., an increase in their oil content can be obtained, but this is accompanied by increased harvesting costs and lower oil quality, as the number of detached fruit increases. Treatment of ripening bunches with auxins, gibberellic acid, or ethephon retards fruit abscission, and harvest can be delayed by up to 5 days without increase in the number of detached fruit. Indications are that oil yield might increase by more than 5% during this period, without change in harvesting costs or oil quality.
Cucumber black root rot caused by Phomopsis sclerotioides
Authors: EBBEN MARION H. , LAST F. T.
Published: February 2008

Phomopsis sclerotioides was proved to be a primary parasite attacking cucumber roots. Black pseudosclerotial and pseudostromatal lesions occurred more commonly at temperatures of c. 20 oC but at 10 oC unspecific light brown lesions predominated. Damage done by P. sclerotioides was minimal at soil temperatures of c. 20 oC, the aerial dry weights of parasitized plants, as percentages of those of the healthy controls, changing from c. 15% to c. 95% as soil temperatures increased from 12 to 20 oC.

Root lesions were associated with root loss and decreased shoot growth. Severe attacks on young plants resulted in stunted growth and small, intensely green leaves. With less severe or later attacks, growth was initially indistinguishable from that of plants growing in uninfested soils until the rate of leaf senescence suddenly increased; these foliar symptoms temporarily simulated attack by vascular wilt fungi. Both sets of foliar symptoms were associated with appreciable yield losses.
The effect of a few days of rain on the distribution of common scab (Streptomyces scabies) on young potato tubers
Authors: LAPWOOD D. H. , ADAMS M. J.
Published: February 2008

At Woburn, Beds, in 1967, potato tubers formed and grew in dry soil except after rain between 23 and 26 June. At lifting, Majestic tubers were severely and uniformly scabbed, except for distinct bands free from lesions. The position of the bands differed depending on the date when tubers started to form; they were further from the stolon attachment when tubers formed early and nearer it when tubers formed late.

Samples taken in June and July showed that the scab‐free band and the late June rain were related. From 25 June to 1 July the soil was probably wet enough to prevent Streptomyces scabies infection, but only one or two tuber internodes remained free from infection; they were the internodes that began to expand about a week before the rain. Internodes that formed while the soil was wet became scabbed, showing they were still susceptible to S. scabies after the soil had dried again.

Recent work on lenticel formation has suggested a hypothesis to explain these results.
The fate of carboxin, benomyl and thiabendazole in seed‐ and soil‐treated plants, as shown by in vitro and in vivo bioassays on some epiphytic yeasts
Authors: GROSS Y. , KENNETH R.
Published: February 2008

The yeast, Sporobolomyces roseus, when added to leaves of barley and pea seedlings seed‐ and soil‐treated with carboxin, benomyl or thiabendazole (TBZ), sporulated little or not at all from both sides of the first leaves. Second leaves of barley and third of pea gave similar results. Tests in vivo showed that all three chemicals reduced sporulation of S. roseus at lower concentrations than they did growth, and also delayed sporulation. Leaves from benomyl‐ or TBZ‐treated plants inhibited the growth of sensitive test organisms (S. roseus, Leucosporidium scottii and Aureobasidium pullulans), on agar: it is considered that fungitoxic substances are excreted from both faces of leaves of barley and pea treated with these chemicals.

Leaves from carboxin‐treated plants, however, did not inhibit sensitive test organisms (S. roseus, L. scottii and Ustilago hordei), so their inhibitory action in vivo is deemed to result from hormonal imbalance in treated plants: carboxin‐treated barley plants were greener than control plants, no guttation occurred on leaves, and stomata tended to remain open; treated barley and pea were more sensitive to drought than were controls. Carboxin‐treated barley and pea plants sprayed with the cytokinin antagonist, abscisic acid, behaved as did plants without carboxin. It is considered likely that carboxin affects the epiphytes by creating a leaf surface incapable of sustaining them, possibly through dryness.
Growth of helminthosporia on media containing the fungicide benomyl and the assay of benomyl using Botrytis cinerea
Authors: GREENAWAY W.
Published: February 2008

A bioassay using Botrytis cinerea detected 0–05 ppm benomyl in potato dextrose agar. Nine species of Cochliobolus, fourteen of Drechslera, four of Helminthosporium and five of Pyrenophora tolerated the presence of benomyl to the same extent, and grew on agar plates containing 40 ppm of the compound.
Control of potato cyst‐nematode, Heterodera rostochiensis, in sandy loam, by Du Pont 1410 (S‐methyl l‐(dimethylcarbamoyl)‐N‐[(methylcarbamoyl) oxy] thioformimidate) applied to the soil at planting time
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E.
Published: February 2008

When applied to heavily infested sandy loam soil at planting time, as little as 5 ppm Du Pont 1410 (5‐methyl I‐(dimethylcarbamoyl)‐N‐[(methylcar‐bamoyl) oxy] thioformimidate) in pots, or 2–5 ppm in field plots, effectively controlled potato cyst‐nematode, Heterodera rostochiensis Woll., and greatly increased the growth and yield of susceptible potatoes. Dipping the shoots of potted King Edward potatoes once in aqeuous solution containing 2000 ppm did not control potato cyst‐nematode. Nematode control was not increased when 2 or 4 kg a.i./ha was sprayed on the foliage of young Pentland Crown potatoes growing in soil already treated with the nematicide.
The effect of seed weight on the early growth and nodulation of white clover
Authors: MYTTON L. R.
Published: February 2008

The results of growing, in agar culture, nodulated and un‐nodulated white clover seedlings from three seed‐weight categories, and the subsequent growth of selected plants in soil in pots, are reported.

Seed‐weight variations greatly influenced plant growth, made substantial differences in nodulation parameters and nitrogen fixation, and contributed appreciably to the observed variability. The relationship of such effects to nitrogen fixation and the relevance to breeding for superior symbiosis are discussed.

The growth of plants, as determined by agar culture technique, was not predictive of their subsequent performance in the soil in pots, and restricting seed weight variations did not improve the prediction. The importance of such effects and the relevance of tube culture to breeding work are discussed.
Seasonal changes in incubation time of Erysiphe graminis f.sp. hordei.
Authors: JENKYN J. F.
Published: February 2008

Incubation time of Erysiphe graminis f.sp. hordei varied seasonally, but between early May and late September it was always between 5 and 8 days. This is approximately the time of year when the 30‐year weekly mean air temperature exceeds 10oC. Amount of infection during summer was decreased by hot, dry weather. In winter, incubation times were more variable and long incubation times were usually associated with few infections. Variation in incubation time during the summer is unlikely to be of practical importance in determining the rate of epidemic development.