bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of viruses on growth and cropping of pear trees
Authors: CROPLEY R. , POSNETTE A. F.
Published: February 2008

Two virus diseases, vein yellows and mosaic, that commonly infect pear trees, reduced the growth and crop of four cultivars (Beurré Hardy, Doyenne du Cornice, Conference and Williams' bon Chrétien) in an experiment continued for 13 years. Reduction in yield was mainly due to the smaller size of infected trees. These produced about 30% less fruit than healthy trees when infected with vein yellows and 40 % less fruit when also infected with mosaic. Fruit size was decreased in only one year. The fertility of Cornice flowers was impaired.

The greater vigour of healthy trees did not delay cropping; they produced over 30% more fruit than infected trees in the first three harvests.
Growth and yield of maize at different altitudes in Rhodesia
Authors: WILSON J. H. , CLOWES M. ST. J. , ALLISON J. C. S.
Published: February 2008

A late (SR 52) and an early (N × K) variety were grown, with irrigation, on well fertilized soil at three sites, Chiredzi (altitude 420 m), Henderson (1260 m) and Grasslands (1620 m). Mean incoming radiation was similar at all sites, while mean temperature decreased as altitude increased.

Final total and grain dry weights were greatest at Henderson, and those of SR 52 exceeded those of N × K, although not greatly at Chiredzi. Initially, leaf area index (L) decreased with increase in altitude, but plants flowered later as altitude increased, and L at the time of flowering was greatest at Henderson. L at flowering was greater in SR 52 than in N × K, though only slightly so at Chiredzi. Leaves withered sooner after flowering at Chiredzi and Grasslands than at Henderson, but leaves of the two varieties withered at about the same time after flowering at each site.

During most of the vegetative phase the efficiency of the leaves and crop growth rate (C) increased with decrease in altitude, and were greater in N × K than in SR 52. More dry matter was accumulated after flowering at Henderson than at the other sites, and more by SR 52 than by N × K at Henderson and Grasslands, but not at Chiredzi. Leaf area duration (D) after flowering was greater at Henderson than elsewhere, and greater in SR 52 than in N × K, except at Chiredzi. After flowering leaf efficiency (dry weight increase ÷D) was least at Henderson and greatest at Grasslands, but differed little between varieties at each site. The fraction in the grain of the dry matter accumulated after flowering decreased with increase in altitude and was greater in SR 52 than in N × K.
The effect of sowing date and photoperiod on panicle morphology in naked oats (Avena nuda)
Authors: JENKINS G.
Published: February 2008

Variations in panicle morphology in different environments were investigated for eight cultivars of naked oats (Avena nuda) and two cultivars of husked oats (A. sattva) in two experiments. The first experiment involved successional sowings in the glasshouse at monthly intervals from February to June. In the second experiment, the plants were grown continuously under constant photoperiods of 9, 11, 13 and 15 h. All the cultivars were found to be photoperiod sensitive, with Victory showing the greatest reduction in time to panicle emergence with increasing photoperiod.

The proportion of multiflorous spikelets in all the cultivars of A. nuda except Nuprime and Laurel was greatest at constant photoperiods below 15 h. With successional sowings the proportion of multiflorous spikelets increased until mid April and thereafter decreased. The proportion of husked grains in the A. nuda cultivars was not markedly affected by variation of sowing date or photoperiod except for an increase in the variety Balkanischer following early sowing and subjection to a 15 h photoperiod. Under certain photoperiod treatments, some A. nuda varieties had a very low proportion of multiflorous spikelets but produced completely naked grain. The implication of these results in studies of the A. nuda genotype is discussed.
Formation and ultrastructure of microsclerotia of Pyrenochaeta lycopersici
Authors: WHITE J. G. , SCOTT A. C.
Published: February 2008

The formation of microsclerotia of Pyrenochaeta lycopersici Schneider & Gerlach was observed in culture, in isolated tomato root segments and in roots of intact tomato plants. In culture microsclerotia formed in the aerial mycelium, and submerged in the agar; in tomato roots they formed in single cells of the outer cortex.

The microsclerotium of P. lycopersici is structurally unspecialized and has cell walls of similar thickness throughout. Microsclerotia are thought to have powers of long survival in soil. In isolation the microsclerotia of P. lycopersici maintained viability over 2 years with consistently high germinability. Transverse hyphae were never seen in sections of microsclerotia, suggesting that germ‐tubes arise from the outermost layers of cells.
Comparative transmission of bean leaf roll and pea enation mosaic viruses by aphids
Authors: COCKBAIN A. J. , COSTA C. L.
Published: February 2008

Acyrthosiphon pisum was a more efficient vector than Myzus persicae of bean leaf roll virus (BLRV), but the two species transmitted pea enation mosaic virus (PEMV) equally well and much more often than Megoura viciae. M. viciae did not transmit BLRV, and Aphis fabae did not transmit BLRV or PEMV.

BLRV and PEMV were transmitted more often by nymphs of A. pisum than by adult apterae or alatae that fed on infected plants only as adults, but both viruses were readily transmitted by adults that had developed on infected plants. The shortest time in which nymphs acquired BLRV was 2 h, and 50 % transmitted after an acquisition period of 4 days. Some nymphs acquired PEMV in 30 min and 50% in 8 h. The shortest time for inoculation of BLRV by adults was 15 min, but some transmitted PEMV in probes lasting less than 1 min. The median latent periods of BLRV and PEMV in aphids fed for 12 h on infected plants were, respectively, 105 and 44 h.

Clones of A. pisum differed in their ability to transmit BLRV and PEMV, and efficiency in transmitting the two viruses seemed to be unrelated. Some aphids that fed successively on plants infected with each virus transmitted both viruses, and infectivity with one virus did not seem to affect transmission of the other.
Host range and overwintering sources of bean leaf roll and pea enation mosaic viruses in England
Authors: COCKBAIN A. J. , GIBBS A. J.
Published: February 2008

Bean leaf roll virus (BLRV) and pea enation mosaic virus (PEMV) were each transmitted by Acyrthosiphon pisum (Harris) to fifteen of thirty species of legumes in the glasshouse; eleven species were susceptible to both viruses. The only biennial or perennial species infected by BLRV were hop trefoil (Medicago lupulina L.), lucerne (M. sativa L.) and red clover (Trifolium pratense L.), but naturally infected sainfoin (Onobrychis viciifolia Scop.) and white clover (T. repens L.) were found. The only perennial species infected with PEMV in the glasshouse was kidney vetch (Anthyllis vulneraria L.).

Eggs of A. pisum, which seems to be the main vector of BLRV and PEMV in England, were found in winter on several species of cultivated perennial legumes, most on lucerne, fewest on white clover. In spring, more viviparae of A. pisum were found on lucerne than on other perennial legumes, and many on lucerne, but few on red or white clover, were infective with BLRV. Lucerne is probably the main overwintering source of BLRV in areas where lucerne is common, but elsewhere red and white clovers are probably as important. No aphid collected from perennial legumes between 1965 and 1968 was infective with PEMV, but this virus can overwinter in common vetch (Vicia sativa L.).

Lucerne infected with BLRV was usually symptomless or showed only transient mild yellowing of young leaves. Lucerne plants showing vein‐yellowing, similar to that previously reported as a symptom of BLRV, were possibly infected with an aberrant strain of BLRV but more probably with BLRV and another aphid‐transmitted agent. Inoculations from lucerne with vein‐yellowing symptoms sometimes caused vein‐yellowing, and sometimes typical BLRV‐symptoms, in crimson clover (Trifolium incarnatum L.).
Glasshouse tests of chemicals for control of potato common scab
Authors: MCINTOSH A. H.
Published: February 2008

Quintozene is the only chemical used successfully in practice to control soil‐borne Streptomyces scabies, the cause of potato common scab. However it may be carcinogenic, and the aim of this work was to find a substitute for it.

About 100 chemicals, most of which had known fungitoxic action or were related to such chemicals, were tested in the glasshouse by growing potato plants in soil with which the chemicals had been mixed, usually at 50 ppm. Many of the chemicals failed to decrease the incidence of scab, or decreased the yield of tubers, or both. The most effective chemical was captafol, which was as effective as quintozene and, unlike quintozene, did not decrease yield. Captan and folpet, which are very closely related to captafol, were ineffective.
Control of potato cyst‐nematode, Heterodera rostochiensis, in silt and peat loams by ten pesticides applied to the soil at planting time
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Incorporated in silt or peat loam top‐soil in spring before susceptible potatoes were planted, three carbamoyl oximes, aldicarb, Tirpate (2,4‐dimethyl‐2‐formyl 1‐1,3‐dithiolane oxime iV‐methylcarbamate) and Du Pont 1410 (S‐methyl i‐(dimethylcarbamoyl)‐N‐((methylcarbamoyl) oxy) thioformimidate) and one organophosphate, Nemacur (O‐ethyl‐O‐(3‐methyl‐4‐methylthiophenyl)‐isopropylamidophosphate) all at n‐2 kg a.i./ha greatly increased the yield of tubers and effectively controlled potato cyst‐nematode (Heterodera rostochiensis Woll.). At the same dosage thionazin was as effective in the peat loam but was ineffective in the silt loam; phorate and Mocap (O‐ethyl S,S‐dipropyl phosphorodithioate) were less effective and chlorfenvinphos, diazinon and a coarse granule formulation of fensulphothion were ineffective in controlling potato cyst‐nematode.
Treating potato ridges in spring with aldicarb, D‐D or dazomet to control potato cyst‐nematode, Heterodera rostochiensis, in sandy clay and peat loam soils
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Applied to potato ridge soil in spring, before potatoes were planted, small amounts of aldicarb (10‐3 kg/ha or less) controlled potato cyst‐nematodes (Heterodera rostochiensis Woll.) better than large amounts of dazomet (110–466 kg/ha) or D‐D (102–439 kg/ha). Applied in spring 1968 and 1969 to heavily infested sandy clay soil 466 kg dazomet/ha allowed Majestic potatoes to grow and yield well in both years without increasing the number of nematodes in the soil after harvest, but in peaty loam dazomet was toxic to potato plants and, when applied in autumn, killed fewer nematodes. D‐D in potato ridges in spring controlled nematodes less well than dazomet or aldicarb, but 896 kg D‐D/ha injected in sandy clay soil in autumn increased potato yield the following year without increasing the number of nematodes after harvest.
Some properties of pelargonium flower‐break virus
Authors: STONE By OLWEN M. , HOLLINGS M.
Published: February 2008

A virus obtained from pelargonium cvs Irene and Paul Crampel appears to differ from any previously reported; although symptomless in most pelargonium cvs tested, it caused colour break in the flowers of two seedling clones. It seems uncommon in pelargoniums. The virus was readily transmitted by inoculation of sap, but not by Myzus persicae with short feeds, by dodder or through seed. It infected only fifteen of 100 species tested in six of thirty‐five plant families. Pelargoniums were freed from the virus by heat‐treatment.

The virus remained infective after 10 min at 85 oC, 3 wk at 20 oC or 27 wk at 2 oC; it was infective at 1/500000 dilution of Nicotiana clevelandii or Chenopodium quinoa sap.

Purified preparations were readily made by several methods, and contained isometric particles c. 30 nm diameter. Although a good antigen, the virus was serologically unrelated to any of forty‐two isometric viruses. In immunoelectrophoresis, the virus moved as a single antigenic component towards the cathode. It gave a single, specific zone in density‐gradient centrifugation, and one moving component (s020 w= 125 S) in analytical centrifugation. The virus contained one protein of mol. wt. c. 41000. The present cryptogram of the virus is (R)/*: */*:S/S:S/*, and the name pelargonium flower‐break virus is proposed.
The effects of trifluralin and related dinitroaniline herbicides on clubroot of Brassicae
Authors: BUCZACKI By S. T.
Published: February 2008

In glasshouse tests, trifluralin, when mixed with the soil before sowing, lowered the incidence of clubroot on cabbages.

An emulsifiable concentrate was more effective than a wettable powder and control was better in soil alone than in a soil/peat mixture. Four other dinitroaniline herbicides were tested; benfluralin and isopropalin lowered clubroot incidence at non‐phytotoxic rates whereas nitralin and dinitramine did not.
The modes of action of two benzimidazoles and thiophanate‐methyl used for the control of Verticillium wilt of strawberry
Authors: JORDAN By V. W. L.
Published: February 2008

Benomyl, thiabendazole and thiophanate‐methyl were found to be fungistatic against Verticillium dahliae in vitro. All materials suppressed wilt symptoms on artificially inoculated strawberry plants when applied as a root dip, soil drench or a foliar application.

Quantitative bioassays of the amount of toxic residues and fungal colonization in tissues of treated plants after root treatment revealed that these materials or their toxic breakdown products were readily translocated to crown and leaves: they suppressed the internal spread of the pathogen throughout the plant. After foliar application there was no marked basipetal movement of material within the plant: fungal colonization was greatly reduced in treated leaves, but the roots and crowns were colonized to a similar extent to those of untreated plants.
Investigations on fungicides: XV. The fungitoxicity and systemic antifungal activity of N‐(2, 2, 2‐trichloro‐1‐methoxyethyl) formamide and related compounds
Authors: CARTER By G. A. , CHAMBERLAIN K. , WAIN R. L.
Published: February 2008

The direct and systemic antifungal activity of 100 compounds structurally related to iV‐(2, 2, 2‐trichloro‐i‐methoxyethyl)formamide has been measured. Some of the compounds showed either protectant or systemic activity against powdery mildew fungi. Compounds not possessing a terminal formamido group showed little anti‐mildew activity and for good systemic activity an alkyloxy or alkylamino side‐chain in the molecule appeared to be necessary.
Effect on carrot root yield and size distribution of the growth‐retardants chlormequat chloride and aminozide
Authors: THOMAS By T. H. , CURRAH I. E. , SALTER P. J.
Published: February 2008

In two experiments, foliar sprays of either chlormequat chloride or aminozide depressed top growth, increased root yield and enhanced leaf and root colour in six carrot cultivars. In the first experiment, a direct correlation between concentration of the two retardants and root yield was apparent within the range 0–2000 mg/1 a.i. applied as run‐off sprays to two cultivars. In the second experiment, increases in total root and canning‐size yield and root/shoot ratio were obtained with four cultivars, but the magnitude of these effects was dependent on the time at which the retardants were applied and the time of harvest of the crop. The effects of aminozide on root yield were less persistent than those of chlormequat chloride, the yield differences between untreated and aminozide‐treated plots decreasing with time after application.
Some effects of seed source on early growth in Maris Peer potatoes
Authors: GRAY D.
Published: February 2008

Potato seed tubers cv. Maris Peer obtained from a number of sources in England and Scotland were graded into a range of weights and after storage for approximately 3 or 7 months in 1971 or 3 months in 1972 they were planted to determine the effect of seed source on early foliage growth.

In both years there were large differences between seed sources on the effect of seed tuber weight on the dry weight of foliage produced in a glasshouse from seed stored for 3 months. In some instances small seed from one source produced the same weight of foliage as large seed from another source. In 1971 after seed storage for 7 months there was no effect of source on foliage dry weight produced in the field. There was, however, no consistent effect of the site of production of the parent seed, of fertilizer treatments of the seed crop, or of N content of the seed tubers. Seed tuber N content increased, though not proportionally, with an increase in seed weight. It was unaffected by source except for seed tubers from one site m 1972.
Changes in developing pea (Pisum sativum) seeds in relation to their ability to withstand desiccation
Authors: MATTHEWS S.
Published: February 2008

In two separate experiments in 1970 and 1971 the germination ability of seeds that had been rapidly desiccated following harvesting from glasshouse‐grown pea plants improved with time after fertilization. In 1970 the germination of seeds directly after harvesting also improved with time. In both years the readiness with which electrolytes were leached from dried seeds decreased with seed age, measured as time after fertilization. The germination ability of desiccated seeds, and of undried seeds in 1970, improved after the cessation of seed moisture increase on the parent plant. This improvement coincided, in 1970, with a fall in the readiness with which electrolytes could be leached from seeds and with a decline in the rate of oxygen uptake of seeds directly after harvest.

Vital staining of dried seeds from harvest samples indicated the viability of the samples as determined by germination tests. In both years, when the cotyledons first showed complete staining, the staining was very intense; in 1970 this occurred in a harvest sample with a greater than 50% germination level, but in 1971 it occurred in a sample that showed incomplete staining in the embryo axis and less than 5 % germination.

In 1971 the comparative rates of moisture loss from seeds, measured with a sensor element diffusion porometer, were very low at 25 days after fertilization, increased up to a peak at 35 days and fell to a rate at the final harvest (44 days) which was nearly three times faster than the initial rate. Thus, during the period of dehydration, after 37 days, the seeds were able to lose moisture.

When seeds were allowed to lose moisture slowly after harvest, before being desiccated rapidly, their eventual condition as measured by leaching improved. Also, the faster the initial water loss preceding rapid desiccation the more readily were the dried seeds leached.

It is suggested that seeds can only withstand rapid desiccation after the cessation of moisture increase and after some slow dehydration, which is accompanied by a slowing down in physiological activity.
The ecology and economics of damage to Brassicae by wood‐pigeons Columba palumbus
Authors: MURTON R. K. , JONES BARBARA E.
Published: February 2008

Damage caused by wood‐pigeons, Columba palumbus, to spring cabbage and Brussels sprouts was measured during three winters in two areas in the Vale of Evesham, Worcestershire. In one area (experimental) special attempts were made to reduce pigeon damage in addition to the normal efforts of the growers. In the other (control) area no such additional measures were taken. There was slightly more damage in 1969‐70, but low market prices made it less important than in 1968‐9 or 1970‐1. There was no significant difference in any season between the damage in the control and experimental areas. No damage was caused to Brussels‐sprout buttons as the birds ate only the tops of the plants; they preferred Brussels sprouts to cabbages and it is likely that the presence of the former helped to reduce the amount of damage to nearby cabbage fields. The amount of damage was not correlated with the amount spent on crop protection; actual damage was not correlated with the grower's estimates in the control area.

In the second season a very intensive shooting campaign in the experimental area did not result in less damage, but the movements of local inhabitants and farm workers near a village did afford protection. The significance of the damage in the Vale and elsewhere is assessed in relation to the economics of crop production, the cropping pattern for cabbages and the behaviour and ecology of the wood‐pigeon.
The feeding behaviour of Phytoseiulus persimilis (Acarina: Phytoseiidae), particularly as affected by certain pesticides
Authors: JACKSON G. J. , FORD J. B.
Published: February 2008

Detailed observations were made of the behaviour of Phytoseiulus persimilis while searching for, identifying and feeding on eggs of Tetranychus urticae. A theory is proposed to explain how P. persimilis may identify prey eggs and distinguish them from non‐prey objects. The existence of a water‐soluble feeding stimulant on prey eggs is postulated.

The effect of residues of captan, dinocap and malathion on the feeding behaviour of P. persimilis was investigated. Residues of the fungicide dinocap on the eggs of the prey did not affect acceptance by the predator, but captan had a marked repellent effect. Malathion had an even stronger repellent effect.

It is suggested that, by making the prey eggs less acceptable to the predator, the use of certain fungicides could render more difficult the prediction of population interactions on which biological control depends.

We wish to thank Dr N. W. Hussey of the Glasshouse Crops Research Institute for helpful comments and for supplying predatory mites. Mr Jackson wishes to thank the Overseas Development Administration for financial support during this work.
Variation in the intensity of diapause in winter eggs of fruit tree red spider mite, Panonychus ultni
Authors: CRANHAM J. E.
Published: February 2008

Winter eggs of Panonychus ulmi from six orchards in Kent showed a range of 3 weeks in the dates of 50 % hatch at field temperatures. From the effects of the duration and temperature of chilling, and the temperature of incubation, it was concluded that samples varied in their chilling requirement, and not in threshold temperatures for development. Diapause was terminated most effectively by chilling initially at o oC (for late‐hatching strains) or 5 followed by 9 for the last month or two. Heritable variation in diapause intensity is discussed in relation to heat sums and the forecasting of hatch, and to phenology.
Comparison and characterization of maize stripe and maize line viruses
Authors: KULKARNI H. Y.
Published: February 2008

Two morphologically similar viruses isolated from maize in East Africa induced two distinct symptom types in maize. One, designated maize stripe virus (MSV), showed broad yellow stripes or a yellowing of the entire leaf, acute bending of the shoot apex and severe stunting. The second, maize line virus (MLV), induced continuous, narrow yellow lines along the leaf veins and did not cause apical bending or stunting. MSV and MLV were both transmitted by Peregrinus maidis (Delphacidae), but not by Cicadulina mbila (Jassidae) or by sap inoculation.

Both viruses were purified by extracting systemically infected leaves in 0–5 M sodium citrate buffer and clarifying with 7 ml n‐butanol/100 ml extract, followed by differential, and finally sucrose density gradient, centrifugation.

Partially purified preparations of both viruses contained isometric viruslike particles of two sizes: MSV particles were 35 and 40 nm in diameter with sedimentation coefficients (so2o, w) I09 anI0o respectively; MLV particles were 28 and 34 nm in diameter. Antisera prepared against MSV and MLV had dilution end points of 1/128 and 1/64 respectively in agar‐gel diffusion tests.

In tests with low‐titre antisera, MSV did not react with MLV antiserum and MLV did not react with MSV antisreum; in the presence of antiserum containing antibodies to both MSV and MLV, the two viruses formed precipitin bands which crossed in the pattern of non‐identity. Maize streak virus and maize mottle virus showed no serological relationship with MSV or MLV.

On the basis of particle size and serology MSV and MLV are shown to be two distinct and possibly unrelated viruses.

MSV and MLV apparently are dissimilar from any characterized viruses of the Gramineae.
Control of potato cyst‐nematode, Heterodera rostochiensis, in sandy, peaty and silt loam soils by dazomet and Telone applied in different ways
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Dazomet applied in the ridges in autumn or in spring, before potatoes were planted in them, controlled potato cyst‐nematode (Heterodera rostochiensis), British pathotype A, better in sandy loam and peaty loam than Telone (1,3‐dichloropropene mixture). In sandy loam dazomet controlled potato cyst‐nematode as well when applied in spring as when applied in autumn and as well when the soil was ridged after treatment as when it was not. Telone was as effective when applied to ridges in autumn as when applied to ridges in spring. In peaty loam potato cyst‐nematodes were least abundant after a crop of Maris Piper potatoes. The yields of King Edward potatoes were greatly increased and nematode multiplication was greatly reduced by dazomet incorporated in the ridges in autumn. Two equal doses of dazomet, one incorporated in the topsoil before, the other after ploughing, controlled potato cyst‐nematode as well and increased the yield of King Edward potatoes more than an equivalent amount of dazomet applied after ploughing. Dazomet applied to silt loam soil in two dressings, one before, the other after, ploughing, controlled potato cyst‐nematode better than an equal amount applied as a single dressing after ploughing. The nematode was controlled best by two large dressings of dazomet or by a combined treatment of dazomet and Telone.
Changes in growth regulator content of radish seedlings, Raphanus sativus, infested with the aphid Myzus persicae
Authors: HUSSAIN A. , FORREST J. M. S. , DIXON A. F. G.
Published: February 2008

Following 10 days of infestation by the aphid Myzus persicae there was an increase in the amount of growth inhibiting substances and a decrease in cytokinins, gibberellins and auxins in infested as compared with similar uninfested radish seedlings. Even after previously infested seedlings have been freed of aphids for 10 days, differences in the hormone balance remained. The possible relationships between the changes in hormonal balance and the effect of the aphid infestation on growth, translocation and wilting are discussed.
Laboratory and field investigations with organophosphorus resistant Tetranychus urticae on strawberries
Authors: GOULD H. J.
Published: February 2008

Laboratory tests using a slide dip technique confirmed that strains of Tetranychus urticae resistant to demeton‐S‐methyl and dimethoate had developed on strawberries in south Hampshire. These pesticides had been used very successfully for many years for the combined control of aphids and red spider mite.

In small plot screening trials dicofol, phenisobromolate, chloropropylate, quinomethionate and dinobuton gave consistently good results. Binapacryl was very effective but caused damage to the plants. A number of other acaricides including formetanate and methiocarb were shown to be worth further investigation.

Tetradifon, also used for some years on strawberries, gave variable results.
Potato blight control in east and south‐east Scotland 1959–68
Authors: BOYD A. E. W.
Published: February 2008

Routine protective spray application to commercial Majestic potato crops on two farms in south‐east Scotland for 9 and 10 years respectively gave highly significant average increases in total yield of 1.2 and 2.1 tons per acre (3.0 and 5.3 tonnes per ha) respectively in rows not affected by tractor wheels. In 6 and 7 years respectively the increases were more than 1 ton per acre. These increases were composed almost entirely of ware tubers. There was no average difference in yield whether the first spray application was made when the haulm closed in the rows or after the first general forecast based on the Beaumont period was announced.

The average total yield reduction in the four rows affected by tractor wheels tended to offset the benefit given by spray application, and, where an eight‐row spray boom was employed, halved the potential overall yield increase. Reduction was again confined to the ware fraction.

Similar experiments with cv. King Edward over a shorter period in eastern Scotland generally showed little consistent effect on yield, possibly partly because of the late appearance of blight in some of these crops.

Considerable yield gains were obtained in Majestic crops even when the disease first appeared in mid‐August in some seasons which could not be classified as ‘blight years’. Over the 10 years of the investigation, there were 5 blight years as defined by Large (1959) compared with the 1 in 10 which Large mentioned for the north of England.

Spread of blight from local sources, such as discard heaps outside the crop and before the occurrence of the field epidemic phase, was found to interfere with adequate timing of spray applications and with the effectiveness of the general forecast based on the Beaumont period.

Infection of Majestic tubers was generally low but at one Majestic site and in the King Edward series the overall average tuber infection was significantly decreased by spraying. Tuber blight was shown to vary inversely with the size of tubers of Majestic as well as of King Edward.
Glasshouse evaluation of some systemic fungicides for control of clubroot of brassicae
Authors: BUCZACKI S. T.
Published: February 2008

Of nine systemic fungicides screened as soil mixes against clubroot, only the precursors of methyl benzimidazol‐2‐ylcarbamate (MBC) or ethyl benzimidazol‐2‐ylcarbamate (EBC) gave promising results. Benomyl was the most effective, usually giving control at 250 mg/kg dry soil. Most fungicides were less effective against an isolate of Plasmodiophora brassicae from Brussels sprouts than against one from rape. Disease control was slightly better on cabbage than on a highly susceptible rape variety.
Effects of soil fumigation on the growth of apple and cherry rootstocks on land previously cropped with apples
Authors: JACKSON J. E.
Published: February 2008

Apple and cherry rootstocks were planted into land on which apple trees had previously been grown and which pot tests had shown to be subject to apple replant disease. Prior to planting the land was either left unfumigated or zones of progressively increasing area (0.052 m2, 0.839 m3, 3.356 m2) centred on the proposed planting holes were fumigated with chloropicrin. Fumigation greatly increased the growth of the apple rootstocks but not of the cherry rootstocks. In the first year after planting the effects of the two larger fumigated areas were identical but in later years apple rootstock growth was directly related to the size of the fumigated area. This indicated that the replant disease does not simply affect tree establishment as was previously thought to be the case. The implications of this are discussed.
Effects of D‐D, Telone or dazomet applied to potato ridges in spring on potato cyst‐nematode, Heterodera rostochiensis, in sandy loam and silt loam soils
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Large amounts of dazomet (329, 439 kg/ha) applied to potato ridge soil in spring, before potatoes were planted, controlled potato cyst‐nematode (Heterodera rostochiensis) in sandy loam and silt loam more effectively than large amounts of D‐D (359, 448 kg/ha). In heavily infested sandy loam, 329 kg dazomet/ha or 857 kg methyl bromide/ha applied in spring 1969 or 439 kg dazomet/ha applied in autumn 1968, greatly decreased the number of larvae able to invade potato roots, so Majestic potatoes grew and yielded well without increasing the number of nematodes left in the soil after harvest. Large amounts of D‐D or Telone applied to the topsoil in autumn or to the ridges in spring were less effective in controlling potato cyst‐nematode or increasing potato yields. Applied in spring 1969 to silt loam ridges, 439 kg dazomet/ha had more effect than 448 kg D‐D/ha on potato cyst‐nematode and on the increase in yield of Majestic potato. The yield of Maris Piper potatoes (resistant to H. rostochiensis pathotype A) in infested silt loam was increased greatly by D‐D, as much by 112 as by 224 or 448 kg/ha.
Phytophthora collar rot of apple: seasonal effects on infection and disease development
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

One‐to three‐year‐old trees of the apple variety Cox's Orange Pippin were highly resistant to infection by Phytophthora cactorum except during the spring from March to May. A rapid increase in resistance occurred after this time from the commencement of shoot growth. The period of susceptibility to infection by P. syringae was from October to December, when trees were dormant. Inoculations with either fungus during the respective susceptible periods caused rapidly extending lesions which girdled and killed the trees; established lesions continued to enlarge in months when trees were resistant to infection.

Similar seasonal fluctuations in resistance to infection by P. cactorum also occurred in mature (35‐year‐old) Cox trees but the susceptible period was longer. Lesions resulting from inoculations at the optimum time (the ‘mouseear’ to ‘pink‐bud’ stages of development) extended at similar rates in both young and old trees.

The infrequent incidence of collar rot in young trees is probably related to factors other than inherent resistance. In resistance and pathogenicity studies young trees gave reliable and consistent results, provided that inoculations were correctly timed in relation to bud development.
Phytophthora collar rot of apple: influence of the rootstock on scion variety resistance
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

In field experiments with young trees great differences were found in the resistance to Phytophthora cactorum of Cox's Orange Pippin apple scions grafted on different clonal rootstocks. The rootstock effect on scion resistance was inversely related to the effect on tree vigour: the rootstocks inducing high resistance were dwarfing (M. 9) or semi‐dwarfing (M. 7, M. 26, MM. 106), and those inducing low resistance were vigorous or very vigorous (M. 25, MM. 104, MM. 109). Mean lesion lengths in Cox on MM. 104 were five to eight times greater than those in Cox on M. 9. The rootstock influence on scion resistance was associated primarily with effects on the rate of lesion extension: during the early stages only of host colonization there appeared to be threshold extension rates below which host resistance factors effectively suppressed a large proportion of infections. The influence of the root‐stock on scion resistance was apparently unrelated to inherent rootstock resistance.

On all rootstocks Cox showed diminished resistance to infection during the period from the swelling of buds to the early stages of shoot growth. Although most susceptible during the ‘mouse‐ear’ and ‘pink bud’ stages of development, suscpetibility was not associated with flowering per se.

Rootstock type did not affect the resistance of Cox scions to P. syringae, for which the period of susceptibility to infection occurred in the dormant season.
Peanut mottle virus in East Africa
Authors: BOCK K. R.
Published: February 2008

A very common and widespread virus pathogen of groundnut and soybean in East Africa was identified as peanut mottle virus (PnMV)* on the basis of particle morphology, serology, host range and reaction, transmission and physical properties.

Virus concentration adequate for serological tests was obtained from cowpea (Vigna unguiculata) cultured at 27 °C but not at 23 °C. Purified preparations from this source gave a single, specific light‐scattering zone in sucrose density gradients.

PnMV was purified using 0.5 M sodium citrate buffer containing 1% mercapto‐ethanol; an antiserum made against such preparations had a homologous titre of 1/8192.

Groundnut and soya isolates from N., N.E., N.W. and S. districts of Uganda, N.W. Tanzania, and W. and E. (coastal) districts of Kenya were serologically similar and varied, within narrow limits, in symptoms induced in certain groundnut and soya varieties. A serologically related but distinct virus was isolated from Voandzeia subterranea.

PnMV was not related serologically to any of ten viruses of the PVY group.

Glasshouse experiments simulating groundkeeper conditions in the field indicated 20% seed transmission in groundnut; PnMV was transmitted by Aphis craccivora in the non‐persistent manner.

All twenty‐one varieties and breeding lines of soybean tested were highly susceptible.

The prevalence of PnMV in East Africa and the reduction in yield caused in groundnut indicates the virus to be economically important, and groundnut and soybean improvement programmes should include routine PnMV susceptibility tests.
Purification and serology of the W strain of cucumber mosaic virus
Authors: TOMLINSON J. A. , ELIZABETH ANNE L. CARTER , FAITHFULL M. , WEBB M. J. W.
Published: February 2008

During studies on the purification of cucumber mosaic virus (strain W) it was found that preparations were most infective and stable when made from tobacco leaves (10–12 days after inoculation) homogenized in phosphate buffer containing EDTA and thioglycollic acid and clarified with diethyl ether.

The preparations were further purified by centrifugation in sucrose density gradients containing EDTA at pH 9.0 and were then stable at 2 °C for > 100 days. When mounted in neutralized ammonium molybdate they were shown to consist of predominantly intact particles.

In tube and ring precipitin tests and in agar gel‐diffusion tests, specific precipitation with homologous antiserum occurred only in media containing alkaline adjusted solutions (ammonium molybdate and dipotassium hydrogen phosphate).
Effect of additives and storage conditions on antibody titres of tobacco mosaic and southern bean mosaic virus antisera
Authors: WATERWORTH H. E. , LAWSON R. H. , BLIZZARD J. W.
Published: February 2008

The effect on serological activity of methods of storing antisera to southern bean mosaic virus and tobacco mosaic virus was tested. Aliquots (0.5 ml) were (1) stored at —70, —20, +4, +26 or +37 °C, (2) repeatedly frozen and thawed, (3) stored in 5% peptone, 0.02% sodium azide or 50% glycerol, (4) diluted before storage, or (5) freeze‐dried. All samples were titrated against purified virus after 1, 6 and 12 months. Most of the treatments had little effect on the precipitin titres of the antisera, but the titres were decreased by storage at 37 °C.

Mention of specific equipment, trade products or commercial companies does not constitute their endorsement by the U.S. Department of Agriculture over similar products or companies not mentioned.
Virus‐like particles in the take‐all fungus, Gaeumannomyces graminis
Authors: RAWLINSON C. J. , HORNBY D. , PEARSON V. , CARPENTER J. M.
Published: February 2008

Isometric virus‐like particles (VLP) measuring 35 nm and 27 nm occurred in cultured mycelium of Gaeumannomyces graminis var. tritici and G. graminis var. avenae. These VLP had, respectively, sedimentation coefficients (s°20, W) 148S and 110S and ultraviolet absorption (maximum 260 nm, minimum 240 nm) typical of nucleoprotein (A260:280 = 1.6, A260:240 = 1.2). Preparations of the 35 nm particles had two major and one minor component in caesium chloride, and 27 nm particles had two components (buoyant densities 1.37, 1.36, 1.30, 1.35, and 1.29 g/cm3 respectively). Preparations of the 35 nm particles or 35 nm plus 27 nm particles had one major protein species with estimated molecular weight 70000 daltons.

The 35 nm VLP were absent from 11 isolates of G. graminis var. tritici from first cereal crops after fallow or non‐susceptible break crops; two of these contained the 27 nm particles. More than half of 145 isolates, from cereals after 2–12 consecutive susceptible crops, contained either 35 nm or 27 nm VLP. VLP were not confined to G. graminis isolates from soils exhibiting ‘take‐all decline’ nor consistently associated with weak pathogenicity or with isolates of unusual growth, morphology, pigmentation, lysis or readiness to form perithecia. Isolates with one kind of particle were mostly more pathogenic and those with both kinds less pathogenic than isolates without VLP. The proportion of isolates with 27 nm and 35 nm particles increased progressively in samples from different consecutive crops during the first 9 years of cropping, then decreased.

Isolates did not gain or lose VLP during infection and re‐isolation from wheat seedlings grown in sand.

Four ‘infected’ isolates were freed from VLP either by culturing ascospores or by growing hyphal tips excised from colonies kept near their thermal death point. Both VLP appeared in cultures which had undergone anastomosis with infected isolates.
Chemical control of the frog‐eye disease (Cercospora nicotianae) of tobacco (Nicotiana tabacum) in Nigeria
Authors: FAJOLA A. O. , ALASOADURA S. O.
Published: February 2008

Six fungicides‐Bordeaux mixture, Verdasan, Tillex, Coprantol, Karathane and Dithane M 45‐were evaluated for the control of the spore germination of Cercospora nicotianae, causing the frog‐eye disease of tobacco. Four of these were also tried against artificial infection in the greenhouse and two against natural infection in the field during three growing seasons of the crop in Southern Nigeria.

The results of the laboratory evaluations were in general agreement with those obtained from the greenhouse and field trials. It was found that Dithane M 45 had a higher fungicidal value and tenacity than the other fungicides tested, and gave the best control of the disease. A marked luxuriant growth induced by Dithane M 45 on treated plants is reported and discussed.
A method for assessing the efficacy of seed disinfectants for the control of seed‐borne Septoria nodorum on wheat
Authors: HOLMES S. J. I. , COLHOUN J.
Published: February 2008

The most rigorous tests of the effectiveness of seed disinfectants for the control of Septoria nodorum on wheat can be made by growing seedlings from treated seeds in the glasshouse at an air temperature of 12 °C and a soil moisture content of 30% of the maximum water holding capacity. In carrying out such tests assessments were made of the percentage of diseased seedlings and of the disease index. Based on the results obtained a schedule of testing is recommended.
The use of canonical analysis for selection within a population of spring barley
Authors: RIGGS T. J.
Published: February 2008

A selection method is described involving the application of canonical analysis to data for a number of measured traits in a composite population of spring barley grown in two seasons.

Lines were selected which fell within the Euclidean space defined by the range, for a number of standard cultivars, on each significant canonical variate. Alternatively, limits were fixed for an acceptable range for each trait and transformed to canonical variates. Lines were selected which fell nearest to the centroid of this acceptable space.

The method might be used as an alternative to the selection index method where difficulty is often encountered in assigning appropriate economic weightings to the traits measured.
The effect of plant spacing on the number of aphids trapped over cocksfoot and kale crops
Authors: A'BROOK JOHN
Published: February 2008

The response to plant spacing by flying and landing aphids has been studied using cylindrical and horizontal sticky traps over cocksfoot and kale crops. Some aphid species showed a significant response to spacing, being caught more frequently over wide‐than close‐spaced crops; the regressions of catches over widely‐spaced on those over close‐spaced plants suggested that most of the species caught followed this trend irrespective of the host plant. The landing response to spacing on horizontal traps at 0.3 m was normally greater than that on cylindrical traps at 1 m. At 1 m, some species (e.g. Aphis fabae gp.) gave a different response to spacing in the two crops, whilst others (e.g. Rhopalosiphum oxyacanthaé) responded similarly to both crop spacings. In contrast to previous results with other aphid species and spaced groundnuts, the landing response of Rhopalosiphum spp. was elicited both when there was a cover crop (clover) between widely‐spaced drills of cocksfoot and by widely‐spaced cocksfoot alone. It is suggested that one stimulus eliciting the landing response with widely‐spaced plants is the electromagnetic emission from bare earth between the plants. Aphid landing behaviour was influenced by the spacing of both cocksfoot and kale plants.
Growth of crop roots in relation to soil moisture extraction
Authors: DURRANT M. J. , LOVE B. J. G. , MESSEM A. B. , DRAYCOTT A. P.
Published: February 2008

Growth of the roots of sugar beet, potato and barley in the field was observed through glass panels and related to changes in soil moisture measured by a neutron probe during 1969–71. The depth of observed root growth was generally related to, but 10–15 cm deeper than, the maximum depth of soil‐moisture extraction. On average of three years, sugar beet, potato and barley used water from the top 23, 33 and 45 cm soil respectively by the beginning of June, and from the top 70, 68 and > 100 cm soil by the end of June. Maximum soil drying in each horizon gave an in situ measure of available water capacity, and showed that sugar beet and barley eventually extracted similar amounts of water from each horizon, but potatoes extracted less, especially from below 60 cm. Between 30 and 100 cm deep, the in situ available water capacity (per 10 cm soil) progressively decreased from 16 to 10, 15 to 5 and 16 to 8 mm under sugar beet, potato and barley respectively. The calculated soil‐moisture deficit (potential evapotranspiration minus rainfall) and measured soil moisture deficit were not related early in the growing period before the crops established much leaf cover.
The overwintering and abundance of cereal aphids
Authors: DEAN G. J.
Published: February 2008

The longevity of Sitobion avenae varied inversely with temperature from 25 to over 100 days when reared outdoors on barley under lantern jars, being longest between December and April–May. This was due mainly to changes in the length of the pre‐ and post‐reproductive periods rather than the length of the period of reproduction. Fecundity varied directly with temperature, from eight to sixty‐seven nymphs per female. When reared on winter wheat and sheltered from wind, rain and snow, S. avenae survived best, Metopolophium dirhodum survived less well and Rhopalosiphum padi worst; when exposed in the open none of the three species survived.

Close relationships were not demonstrable between the numbers of alate M. dirhodum, S. avenae and Rhopalosiphum spp. trapped in any year, between the abundance of these aphids and weather conditions between January and April, or between the numbers of these alatae and the size of crop infestations. This was probably because insufficient information was available about their biology, both inside and outside the crop.