bluuebunny/crossref_metadata_2025 huggingface dataset:
SUGAR BEET YELLOWS: A PRELIMINARY STUDY OF THE DISTRIBUTION AND INTERRELATIONSHIPS OF VIRUSES AND VIRUS STRAINS FOUND IN EAST ANGLIA, 1955‐57
Authors: RUSSELL G. E.
Published: February 2008

Aphid transmissions to sugar beet seedlings from yellowed sugar beet leaves collected from commercial fields in East Anglia during the summers of 1955, 1956 and 1957, showed the occurrence of two yellowing viruses. One was sugar beet yellows virus (SBYV) and produced vein‐etch and yellowing symptoms on beet seedlings in the glasshouse; the other produced yellowing but no etch. These two viruses were apparently unrelated, so that sugar beet tolerant to one of them would not necessarily be tolerant to the other. The second virus, called ‘sugar beet mild yellowing virus’ (SBMYV), decreased the root yield of sugar beet plants grown under glass, by as much as did the milder SBYV strains, but less than did the severe SBYV strains. The proportions of the two viruses in the samples differed from year to year and from place to place.
OBSERVATIONS ON THE CONTROL OF MITE INFESTATIONS IN STORED WHEAT BY CHEYLETUS SPP. (ACARINA, CHEYLETIDAE)
Authors: NORRIS J. D.
Published: February 2008

An account is given of the control of the grain mite Acarus siro L. (=Tyroglyphus farinae L.) by the predatory mite Cheyletus sp. in imported wheat stored in bags or in bulk. After 12–18 months of storage Cheyletus sp. had developed in 75% of the parcels of wheat and in 67% of these it became dominant over other mites. This usually occurred in late summer for bagged wheat. Control of A. siro by Cheyletus sp. compared favourably with that achieved by fumigation with methyl bromide and on occasion was superior. Both development and dominance of Cheyletus sp. were adversely affected by earlier fumigation but there was some evidence that spraying wheat with γ‐BHC favoured the development of this species and, in some circumstances, its dominance. Dominance by Cheyletus sp. in bulk grain often occurred in the winter months when the surface moisture content of the wheat was at its highest.

The development of Cheyletus eruditus Schr. is described in a bulk grain store where dense populations of A. siro and Glycyphagus destructor Schr. were eliminated by the predator. The numbers of C. eruditus in wheat tended to increase faster when the surface layers were disturbed than when the grain was undisturbed. Nevertheless, dominance over the other mites tended to occur first in undisturbed grain.
THE ADAPTATION OF FUNGI TO FUNGICIDES: ADAPTATION TO COPPER AND MERCURY SALTS
Authors: PARRY K. E. , WOOD R. K. S.
Published: February 2008

The susceptibility of Botrytis cinerea to copper sulphate in liquid media increased when the volume, and therefore the depth, of the medium in culture bottles exceeded certain values; when the volume was 40 ml. the maximum concentration allowing growth was 300 p.p.m.

By growing mycelium in media containing progressively higher concentrations of copper sulphate a strain was produced which grew at a concentration of 750 p.p.m.

In high concentrations of copper sulphate growth always started at the edge of the liquid, and inocula grew only if they were placed in this position.

In germination tests spores from the resistant strain were more resistant to copper sulphate than were spores of the parent strain.

The resistance of mycelium, and to a lesser extent of spores, was retained after growth of the resistant strain for six months in fungicide‐free media.

Spore and mycelial inocula grew in much higher concentrations of copper sulphate when nutrient media were solidified with agar.

The strain resistant in liquid media was no more resistant than the parent strain on agar media.

The resistance of the fungus was not increased after growth for long periods on agar containing high concentrations of copper sulphate. The resistance of the strain resistant in liquid media was not lost after growth on agar media for 3 months.

Attempts to produce strains more resistant than the parent to mercuric chloride were unsuccessful.

The results obtained with phenyl‐mercuric acetate were essentially similar to those obtained with copper sulphate, but relatively much more resistant strains were produced.
THE EFFECT OF LARVAE OF CHIRONOMUS RIPARIUS MEIGEN ON THE REDOX POTENTIALS OF SETTLED ACTIVATED SLUDGE
Authors: EDWARDS R. W.
Published: February 2008

The introduction of Chironomus riparius larvae to give densities of 12,500 and 50,000/m2in activated sludge, previously settled and consolidated for 6 months, had the following effects:

(a)a rise in pH initially at the sludge surface but later extending to all depths,

(b)an increase in the depth of the surface layer of sludge where the redox potential is high,

(c)increases in the pH value and concentration of ammonia and a decrease in the concentration of oxidized nitrogen in the overlying water.
THE DEVELOPMENT OF A COMPARATIVE METHOD FOR THE EVALUATION OF THE MOTH‐PROOFNESS OF WOOL SERGE
Authors: HUECK H. J.
Published: February 2008

Existing test methods for the moth‐proofness of wool were compared in inter‐laboratory experiments and found to be lacking in accuracy and agreement between laboratories.

Several factors influencing the usefulness of such a test method were investigated, and it was found that a considerable gain in accuracy could be reached if weight loss due to larval attack on test samples was referred to weight loss obtained with a standard wool serge impregnated with a standard moth‐proofing substance. Apart from this principle, improvements in the general testing procedure, including the number of test samples and test animals used, the definition of weight loss and the introduction of strict randomization procedures proved to be valuable.

As a provisional reference standard, wool serge impregnated with dinitro‐α‐naphthol was adopted. A tolerance level for the moth‐proofness of wool serge was laid down.
FURTHER STUDIES ON RASPBERRY RINGSPOT AND TOMATO BLACK RING, SOIL‐BORNE VIRUSES THAT AFFECT RASPBERRY
Authors: HARRISON B. D.
Published: February 2008

Raspberry ringspot virus (RRSV) was found in eastern Scotland and Wiltshire infecting several varieties of raspberry, several weed species and sugar beet. Serological tests, and protection tests in Petunia hybrida, showed that isolates from different host species found at several localities in eastern Scotland were more closely related to one another than to the isolate from Wiltshire. RRSV was readily transmitted to Chenopodium amaranticolor by mechanical inoculation of sap from diseased raspberry but less readily to other species. Both the symptoms shown by C. amaranticolor, French bean, tobacco and Petunia hybrida, and its behaviour in serological and plant‐protection tests, distinguished RRSV from tomato black ring, raspberry yellow dwarf, tobacco ringspot and cucumber mosaic viruses. Preparations of RRSV lost infectivity when diluted 10‐4, kept for 3 weeks at 18° C., or when heated for 10 min. at 70° C. but not at 66° C. RRSV was precipitated without being inactivated by ammonium sulphate, ethanol or acetone. It was inactivated at pH 3.

The beet ringspot strain of tomato black ring virus was isolated from the raspberry varieties Malling Seedling V and Malling Exploit by mechanical inoculation of sap to Chenopodium amaranticolor, but not from other varieites growing in virus‐infested soil.

RRSV and the beet ringspot strain of tomato black ring virus are soil‐borne. They infected plants grown under glass in soil collected from several different fields: the incidence of infection differed in different soils, but infection by each virus was favoured by the same samples of soil. Infection with tomato black ring virus occurred equally in soil collected at different times of the year. Treatment with formaldehyde or parathion made soil non‐infective. Attempts to detect virus in extracts of virus‐containing soils, and to make autoclaved soils infective by watering them with virus suspensions or by growing artificially infected plants, failed, suggesting that infection depends on some factor other than free virus, possibly the presence of an organism.
EXPERIMENTS IN THE SUDAN GEZIRA ON CONTROL OF WILT OF DOLICHOS BEAN (DOLICHOS LABLAB) ASSOCIATED WITH ATTACK BY COCKCHAFER GRUBS (SCHIZONYCHA SP.)
Authors: TARR S. A. J.
Published: February 2008

Wilt of dolichos bean (Dolichos lablab) in the Sudan Gezira appeared to be due primarily to cockchafer grubs (Schizonycha sp.) in the soil attacking the hypocotyls or roots of plants up to about 6 weeks after sowing. Many wilted plants also showed symptoms of ashy stem blight (Macrophomina phaseoli), but in these the fungus was probably a secondary invader rotting roots weakened or damaged by unfavourable soil conditions or insects. Wilt was often severe in dolichos sown on land cropped to sorghum (Sorghum vulgare) in the preceding season, sorghum roots in the soil harbouring the grubs. Under moderate grub attack seed dressings containing organomercurial and γ‐benzene hexachloride (BHC) gave satisfactory‐protection at 0.089%γ‐BHC/seed but were inadequate when wilt was severe. Dieldrin and aldrin at 0.044 or 0.089%/seed gave excellent protection in all experiments, but their performance under exceptionally severe wilt conditions has yet to be tested, as also the relative efficiencies of seed treatment and soil treatment under such conditions. Fungicide‐insecticide seed treatment also reduced preemergence rotting of germinating seeds due to grub attack.

Wilt rarely occurred in dolichos planted on land fallow in the preceding season, but, even in the apparent absence of wilt, seed treatment often appreciably improved emergence, plant populations, growth and yields. These effects possibly resulted from control of root damage by soil insects, such damage reducing growth and yields but not sufficiently severely to cause wilting. Pending further investigation a powder seed dressing containing organomercurial plus 20% dieldrin, and applied at 1:450 by weight to seed (about 5–6 g./acre of dieldrin), is recommended for dolichos bean in the Gezira.
MOVEMENT OF EELWORMS
Authors: WALLACE H. R.
Published: February 2008

Tracks were plotted of about 300 individual eelworms comprising six species among water droplets on a glass surface. Measurements of the tracks indicated that the product of length and activity of an eelworm divided by its speed was a constant. This supports the hypothesis that the speed of an eelworm among water droplets is a function of its length and activity. This principle can only be applied to movement in soil where the length of the eelworm is less than about three times the particle diameter. Under such conditions the eelworms move in thin films or water droplets over particles. Among smaller‐sized particles the speed of the eelworms is influenced by particle size. With increasing eelworm length there is an increase in soil particle size for maximum mobility.
SOME EFFECTS OF CHANGING TEMPERATURE AND OF VIRUS INHIBITORS ON INFECTION BY CUCUMBER MOSAIC VIRUS
Authors: BADAMI R. S.
Published: February 2008

Whereas the spinach strain of cucumber mosaic virus fails to multiply and cause symptoms in tobacco plants kept above 30° C., the yellow strain infects at 36° C. and causes more severe symptoms than at 20° C. Increasing the temperature up to 28° C. increases the initial rate at which the spinach strain multiplies, but the virus later reaches much higher concentrations in leaves at lower temperatures, presumably because it is rapidly inactivated at 28° C. Exposing inoculated plants to 36° C. for 6 hr. decreases the number of infections by the spinach strain when the exposure starts within 6 hr. of inoculation, but not afterwards.

Pancreatic ribonuclease inhibits infections by strains of cucumber mosaic virus; inhibition is greatest when the enzyme is present in the inoculum, and when applied to inoculated leaves its effect decreases rapidly with increasing time after inoculation.

Infection by and the multiplication of strains of cucumber mosaic virus in tobacco are only slightly affected by thiouracil and greatly by azaguanine, whereas strains of tobacco mosaic virus are inhibited much more by thiouracil than by azaguanine. Like tobacco mosaic virus, cucumber mosaic virus multiplies more when inoculated leaves are floated in nutrient solutions than in water, but unlike tobacco mosaic virus, its multiplication is not inhibited by thiouracil more in nutrient solutions than in water.
EFFECT OF NITROGENOUS FERTILIZER APPLIED AT DIFFERENT DATES ON TAKE‐ALL, EYESPOT AND YIELD OF WINTER WHEAT GROWN ON LIGHT SANDY LOAM
Authors: SALT G. A.
Published: February 2008

In a replicated field experiment on light sandy loam at Woburn, where winter wheat is a very uncertain crop, Cappelle and Holdfast, grown after potatoes with dung, yielded 50 and 41 cwt./acre of grain, respectively, when given 6 cwt./acre of Nitro‐Chalk in April, compared with 19 and 20 cwt./acre when unfertilized. The same fertilized plots yielded 29 and 19 cwt., respectively, in the second, and 25 and 17 cwt./acre, respectively, in the third year on the same land, whereas unfertilized plots of both varieties yielded only 9 and 5 cwt./acre. The decrease in mean yield from 27 cwt. in the first, to 15 and 10 cwt./acre in the second and third crops was associated with a decrease in ear number from 16.7 to 14.6 and 12.2, respectively, and with a striking decrease in weight of grain per ear, caused partly by a large increase in the proportion of small grains. Eyespot (Cercosporella herpotrichoides Fron.) although present each year did not become prevalent; an increase in the percentage straws affected by take‐all (Ophiobolus graminis Sacc.) from 9 to 15 and 26%, respectively, and a severe increase in weed infestation (Agrostis gigantea) appeared to be the main factors reducing yield.

Nitro‐Chalk applied in April yielded most grain every year, and wheat fertilized at this time had less eyespot and take‐all than that fertilized in March. Fertilizer applied in May increased weed growth, failed to decrease take‐all and yielded fewer ears, less grain, and a higher proportion of tailcorn than did earlier applications.
AN ANALYSIS OF THE GROWTH RESPONSE OF YOUNG TOMATO PLANTS TO INFECTION BY VERTICILLIUM ALBO‐ATRUM: II. THE PRODUCTION OF GROWTH SUBSTANCES
Authors: PEGG G. F. , SELMAN I. W.
Published: February 2008

Bioassays on ether‐soluble acid extracts from healthy and Verticillium‐infected tomato plants, showed the presence of substances inhibiting growth of wheat coleoptiles in both healthy and infected leaves and stems, but the amounts were greater in the infected.

Assays of infected stems and leaves showed increases in growth‐promoting activity expressed as indole‐3‐acetic acid equivalents (IAAe), up to 200% of those for healthy controls.

Similar assays of cultures of V. albo‐atrum showed growth‐promoting activity. No acid substance capable of inhibiting the growth of wheat tissue was detected in the culture filtrate. IAA was identified by colour test with Ehrlich's reagent on chromatograms from extracts of both infected stems and fungal culture filtrates.

The vertical distribution of IAAe was determined in healthy and infected plants at the eight‐leaf stage by assaying individual leaves and four stem segments separately. In healthy plants the IAAe content was greatest in the young leaves (6–8) but no gradient was observed as between leaves 1–5. In infected leaves increases over the controls were found in leaves, 1, 3 and 6 and a decrease in leaf 8.

In healthy stems IAAe was highest in the distal segment and infected stems showed higher values at all four levels, with the relative increase greatest in the distal region.

It is suggested that the major part of the Verticillium syndrome including petiolar epinasty, tylosis, pith hyperplasia and the formation of adventitious roots is the result of an accumulation of growth substances in infected tissue.
THE INCIDENCE OF CERTAIN SEED‐BORNE DISEASES IN COMMERCIAL SEED SAMPLES: I. LOOSE SMUT OF BARLEY, USTILAGO NUDA (JENS.) ROSTR.
Authors: MARSHALL GILLIAN M.
Published: February 2008

A simple whole‐embryo test for detecting the presence of loose smut, Ustilago nuda, in barley grains has been developed and is described. Embryos from 1000 grains can be examined within 24 hr. and the actual working time per sample is just over 1 hr.

The results of embryo tests showed a high positive correlation with the incidence of the disease in field plots, (r= 0.83).

Commercial samples of seed barley, submitted in 1954‐57 to the Official Seed Testing Station, have been examined by this embryo test for the presence of loose smut. The varieties received could be clearly divided into two groups: the Scandinavian‐bred varieties, e.g. Carlsberg and Herta, having 84% of the samples infected, with the level of infection up to 19%; and the English‐bred varieties, e.g. Proctor and Plumage‐Archer, where only 9.5% of the samples were infected, with the level of infection rarely more than 0.5%. In spite of differences in weather conditions during the period when infection occurred seasonal variations in the incidence of loose smut were not obvious from the results in the 3 years.
THE DETERMINATION OF THE SIZE OF PLOT SUITABLE FOR COTTON SPRAYING EXPERIMENTS IN THE SUDAN GEZIRA
Authors: JOYCE R. J. V. , ROBERTS P.
Published: February 2008

An insecticidal experiment in the season 1955‐56 investigating interplot effect—defined as the interaction of one plot with the insect population on an adjacent plot—is described. This effect is considered to operate in three possible ways: (a) spray drift; (b) insect (pest) movement; (c) insect (parasite and predator) movement.

In the experiment, care was taken to minimize (a). The plot sizes were 10‐ or 20‐feddan fields within areas of 90 and 180 feddans, respectively.

There was strong evidence that yields of fields on the boundaries between sprayed and unsprayed fields were affected by the treatments on the other side of the boundary. That is, sprayed fields yielded less when adjacent to unsprayed fields and unsprayed fields yielded more when adjacent to sprayed.

When cotton fields of 10 feddans in areas of about 90 feddans were unsprayed and separated by 150 or 450 m. of unsprayed cotton from sprayed fields, Empoasca libyca de Berg. and bollworm infestations were not measurably changed, but the Hercothrips spp. infestations were significantly reduced and the Bemisia tabaci Genn. infestation slightly increased compared with those found on 10‐feddan fields within 90 feddans of completely unsprayed cotton, the changes in infestation corresponding to the distance from the sprayed cotton. Yields from such fields tended to be higher than those from within completely unsprayed cotton, although these differences were not significant.

When fields of 20 feddans in areas of 180 feddans were unsprayed and separated by 150 or 450 m. of unsprayed cotton from sprayed fields of similar size, there were no apparent differences when their insect infestations or yields were compared with those from 20‐feddan fields within 180 feddans of completely unsprayed cotton.

These results are adduced as evidence that interplot effect might have affected infestations and yields in 10‐feddan fields of unsprayed cotton at distances of 150 or 450 m. from sprayed cotton. No such interplot effect was apparent when 20‐feddan fields were used. It is considered that spray drift was unlikely to have caused these results which must, therefore, have been due to insect (pest, parasite and predator) movement.

It is concluded that in experiments in the Sudan Gezira, where treatments affect the insect complex on cotton, it is dangerous to assume that a 10‐feddan field in a 90‐feddan area is independent of differently treated fields in that area. On the other hand, independence can probably be assumed in 20‐feddan fields in 180‐feddan areas of cotton, provided that the field is separated from its differently treated neighbour by at least 150 m.
BACTERIAL CANKER OF STONE‐FRUITS: IV. INVESTIGATION OF A METHOD FOR MEASURING THE INOCULUM POTENTIAL OF CHERRY TREES
Authors: CROSSE J. E.
Published: February 2008

Pseudomonas mors‐prunorum Wormald, the organism causing bacterial canker of stone‐fruits, was present on healthy cherry leaves during the autumn in numbers sufficient to suggest that they were the main source of inoculum for the infection of stems and branches. Quantitative estimates of the pathogen could be obtained by shaking leaves in water and plating out the washings. This method was examined in detail as a possible means of comparing the inoculum potentials on different cherry varieties.

The numbers of the pathogen varied considerably between leaves and between branches, but not between trees of the same variety. It was estimated that a sample of 192 leaves, eight from each of twenty‐four different branches would be adequate to show differences between varieties if sufficiently replicated in time. The accuracy of a twenty‐four branch sample was tested by comparing parallel samples from two separate groups of trees of the same variety. There was a highly significant correlation between the numbers of bacteria obtained from the two series of samples. From the error variance in an analysis of variance, it was calculated that five successive samples would show a significant difference between two such groups of trees if one exceeded the other by 54%.

It was necessary to wash leaves for 4 hr. or more, depending on temperature, to recover all the bacteria from the leaf surfaces. At temperatures lower than 27° C. however, bacterial growth intervened before this stage was reached. At laboratory temperatures a period of 4 hr. washing was found to be most suitable for comparing varieties and gave 80–90% recovery of bacteria without errors due to growth.

A characteristic flora of non‐parasitic bacteria was observed on cherry trees, coexisting with the pathogen on the leaf surfaces. The fungus Pullaria pullulans was also extremely abundant.
THE EFFECTS OF METHODS OF SEWAGE APPLICATION ON THE ECOLOGY OF BACTERIA BEDS
Authors: HAWKES H. A.
Published: February 2008

Two difficulties in treating sewage in bacteria beds—namely, the choking of the beds by excessive growths of micro‐organisms and the nuisance from flies breeding in the beds—are considered as one ecological problem. The effect of the manner in which the sewage is applied to the bed through different types of distributor nozzle on the film and fauna populations was studied. It was found that nozzles which provided a strong flushing action on the surface did not prevent excessive growth of film below the surface but did limit the grazing fauna, as a result of which the amount of film was greater than under jets in which the flushing action was reduced. Where this reduction was effected by allowing the sewage jet to first impinge on a splash plate, uniform conditions were produced in the medium below, where the species were in direct competition for food in the one ecological niche. As a result the fly larvae (Anisopus fenestralis and Psychoda sp.) suppressed the population of Achorutes subviaticus (Collembola) during the winter. Where the flushing action was reduced by allowing the sewage to flow through an increased number of holes of smaller bore, two niches were provided, one wet region, subject to some flow of sewage, and the other drier region between the jets. Under this method, two populations existed side by side, Achorutes being present throughout the year in the drier zone and A. fenestralis larvae occupying the sub‐jet zones.
LEAF INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E.F.SM.) DOWSON
Authors: LAST F. T.
Published: February 2008

Xanthomonas malvacearum spread more rapidly along vascular tissue than into mesophyll when inoculated to the main veins of susceptible cotton leaves. The extent of spread varied with the concentrations of inocula, tissue age and cotton variety.

Increasing concentrations of inocula accelerated the initial spread of disease.

Bacteria spread more rapidly in young leaves than in old—increasing age greatly decreased disease in the mesophyll. The initial invasion was quicker in young leaves of young plants than in young leaves of old plants.

Three types of behaviour, according to the host's reaction, distinguish Knight's resistance factors: (a) where X. malvacearum spread extensively along veins and into mesophyll of plants containing factors B3 and B5; (b) where it was restricted to the point of inoculation in plants containing B4, B9 and combinations with B6m; and (c) where it spread along veins but not appreciably into mesophyll in varieties containing B2 and B2B3.

From this and four other different types of tests, factors B2 and B3 seem to increase mesophyll resistance but only B2 gives appreciable vascular resistance. Further, the vascular bundles in varieties with B2 seem to be surrounded by an additional ‘barrier’ which resists X. malvacearum.
THE SURVIVAL IN SOIL OF APTERAE OF THE LETTUCE ROOT APHID, PEMPHIGUS BURSARIUS (L.)
Authors: DUNN J. A.
Published: February 2008

Some aphids in a population of Pemphigus bursarius on the roots of a summer host do not form wings and fly back to poplar. The fate of these apterae has been investigated and it was found that they could successfully overwinter even though their original host plant had died. Having overwintered without their host, they were then able to colonize the roots of a spring‐planted lettuce crop. Whether the soil was cultivated before or after winter seemed to have little effect on the numbers of apterae that survived.

The influence of temperature on the survival of apterae was studied, and from the findings it appears to be well within the capacity of P. bursarius, in the Midlands, to hibernate in the soil without a host from October to April.
FEEDING HABITS OF THE LACE‐BUG URENTIUS AEGYPTIACUS BERGEVIN (HEMIPTERA: TINGIDAE)
Authors: POLLARD D. G.
Published: February 2008

Adults and nymphs of the lace‐bug Urentius aegyptiacus Bergevin (Tingidae) feed on leaves of the egg‐plant (Solanum melongena L.). The stylets of this insect are of typical hemipteran structure and are inserted into the leaf from either surface. Penetration of the epidermis is mainly intracellular, but may be intercellular or stomatal, while the course through the mesophyll and palisade tissues—frequently in a plane parallel to the leaf surfaces—is predominantly intracellular. The stylets terminate intracellularly, generally within a palisade cell, sometimes in a mesophyll cell, but only rarely in the vascular elements. The stylet sheath and track are absent and the saliva neither gels nor stains. Feeding damage, which results in externally visible chlorotic areas, is caused by the extraction of cell contents within feeding zones which are confined at first to the palisade but later extend to the mesophyll: it is accompanied by laceration of the cell walls and diffusion of an oral secretion of low phytotoxicity. Shrinkage of the leaf is due initially to collapse of the mesophyll and epithelial cells; the palisade and xylem cells retain their characteristic size and shape until destruction of the other tissues is complete.
EXPERIMENTS ON THE MODE OF ACTION OF INSECTICIDAL SEED‐DRESSINGS, ESPECIALLY AGAINST LEPTOHYLEMYIA COARCTATA FALL., MUSCIDAE, THE WHEAT BULB FLY
Authors: WAY M. J.
Published: February 2008

Certain chlorinated hydrocarbon insecticides applied as seed‐dressings to wheat can kill wheat bulb fly larvae either by contact or by systemic action.

Newly hatched larvae may be killed by contact action when they pass close to the treated seed on their way to attack the shoot. Such kill depends on the behaviour of the larvae and on the depth the seed is sown. Larvae move upwards after hatching and probably reach the surface soil where they search for the host plant, entering the shoot at a depth of between 1/4 and 1 in. This behaviour explains results of experiments in which about half of the larvae were killed by contact action of dieldrin on seeds sown 1/4 in. deep and few or none by similarly treated seeds sown at 3 in. It is not known whether the larvae are killed directly by contact action or whether they die of starvation after being deterred.

Larvae not killed by contact may be killed by systemic action. The systemic action of dieldrin and aldrin, unlike their contact action, does not protect the plant from damage by wheat bulb fly larvae, which tunnel within the shoot and destroy the growing point before they are killed. γ‐BHC applied as a seed‐dressing apparently remains systemically active for less time than dieldrin or aldrin, but while active usually kills, or perhaps deters, the larva before it significantly damages the plant.

The uptake of dieldrin and aldrin by the wheat seedling depends on contact between the insecticide and the seed or roots, close contact with the seed seeming especially important. Systemic action is also favoured by late sowing, by sowing the seed very shallowly and by increasing the dose of insecticide adhering to the seed. Dieldrin applied as a seed‐dressing at 4.5 mg./seed was not phytotoxic to Cappelle wheat sown within 10 days of treatment, whereas γ‐BHC, even at 0.022 mg./seed, delayed the germination of some seeds.

Preliminary experiments with dieldrin seed‐dressings against onion fly larvae showed that newly hatched larvae mostly enter the young onion plant at the base of the bulb close to the position of the treated seed and thus are likely to be killed by contact with the insecticide on the seed. There was no evidence that dieldrin seed‐dressings act systemically against onion fly larvae.
HOST FINDING BY APHIDS IN THE FIELD: GYNOPARAE OF MYZUS PERSICAE (SULZER)
Authors: KENNEDY J. S. , BOOTH C. O. , KERSHAW W. J. S.
Published: February 2008

Attempts to test experimentally the theory of olfactory attraction to host plants gave negative results, and more conclusive evidence was sought by recording the behaviour of host‐finding migrants in the field. The first of three occasions when the natural alighting rate was high enough for comparative purposes was an autumn migration dominated by Myzus persicae returning to its specific overwintering host, the peach tree.

The proportion of M. persicae gynoparae among all aphids caught alighting on a spindle tree, where persicae does not overwinter, was as high as on peach. The much heavier accumulation of migrants on the peach was evidently due, not to their differential alightment, but to their differential rate of departure, with a longer average stay on the peach. The proportion of persicae gynoparae was smaller in catches on transparent sticky traps than among alighters on the trees, and they avoided alighting on brussels sprout plants more often than on peach. Only a fraction of those that approached the plants alighted, even on peach; and only a small fraction of those that did alight, stayed, even on peach.

There was appreciable colonization of spindle and sprouts by the M. persicae gynoparae and some ‘wasted’ oviposition by their progeny on spindle. After the migration was over the peach leaves entered the last stages of senescence before the spindle leaves, and persicae gynoparae (no longer able to fly) that were given access to both at that time, settled preferentially on spindle. The distribution of males created the impression that they were less host‐specific than gynoparae.
HOST FINDING BY APHIDS IN THE FIELD: APHIS FABAE SCOP. (GYNOPARAE) AND BREVICORYNE BRASSICAE L.; WITH A RE‐APPRAISAL OF THE ROLE OF HOST‐FINDING BEHAVIOUR IN VIRUS SPREAD
Authors: KENNEDY J. S. , BOOTH C. O. , KERSHAW W. J. S.
Published: February 2008

Aphis fabae gynoparae occurred in the same large proportion in simultaneous collections of all aphids alighting and probing on, and taking off from, a host plant (spindle) and a non‐host (peach), and behaved similarly when approaching and leaving them in the same conditions. Most alighters took off again from leaves of both kinds within a few minutes, staying longer and probing more times on the host. In atmospheric conditions favouring local ‘hovering’ instead of dispersal, flying and alighting aphids became concentrated around host plants, not through any specific attraction to them, but apparently because more aphids had accumulated upon them and were now taking off.

Brevicoryne brassicae occurred in the same large proportion in simultaneous collections of aphids alighting on a host plant (cabbage) and a non‐host (sugar beet). No satisfactory evidence was found of preferential alightment on cabbage and there were indications of preferential alightment on the non‐host. A very small minority of the A. fabae and B. brassicae that alighted on their hosts stayed there long enough to larviposit. This minority was rather larger among alighters late in the day, but in the absolute sense, more colonization occurred during earlier periods when more aphids arrived.

The intensely dispersive type of host‐finding behaviour in Myzus persicae, A. fabae and B. brassicae may be common among Aphididae. It seems ideal for the dissemination of non‐persistent plant viruses, more particularly among the less‐favoured host plants of each aphid. The tendency to commensal association between virus and vector provides an ecological framework which may govern the incidence of virus‐vector specificity and symbiosis.
STUMP PROTECTION AGAINST FOMES ANNOSUS: TREATMENT WITH CREOSOTE
Authors: RISHBETH J.
Published: February 2008

Creosoting of pine stumps immediately after felling commonly prevents the entry of Fomes annosus and other primary basidiomycete colonizers through the cut surface. Ceratocystis spp. and Ophionectria cylindrospora frequently enter creosoted stumps, but growth tends to be slow.

Light applications of creosote often fail to exclude basidiomycetes. Failure to achieve protection may also result from delay in application, especially when resin flow from the cut surface is rapid; this flow impedes creosote penetration.

In one experiment creosoting also controlled air‐borne Fomes annosus infection of larch stumps. Various protectants were tested in the forest, a preliminary indication of their efficiency being obtainable after 2 months. A gasworks creosote (b.p. 190–300° C.) was promising, whilst a tar/creosote mixture was unsatisfactory.

Disadvantages of creosote as a stump protectant arise mainly from its retarding effect on stump colonization. Creosoted stumps tend to remain alive longer than untreated ones and the risk of F. annosus attaining dominance in stumps already having root infection is correspondingly greater.
BACTERIAL ROTTING OF APPLE FRUIT
Authors: COLE MARTIN
Published: February 2008

Three bacterial isolates obtained from a rotten apple were found to produce actively spreading firm brown rots when stab‐inoculated into Bramley's Seedling apples, but bacteria were not found at the front of the rot.

One isolate was a capsulated, non‐motile, non‐fluorescent, Gram‐negative rod apparently not described previously. The name proposed for the isolate is Pseudomonas pomi. The other two isolates were the same and were non‐capsulated, non‐fluorescent, Gram‐negative motile rods, usually with two polar flagella, and were considered to be identical with Ps. melophthora Allen & Riker (Allen & Riker, 1932).

The three isolates grew on media at pH 5.0 and in apples with juice of pH 3.5. For each isolate the square of the distance of the front of the rot from the point of inoculation of apples, was found to be directly proportional to the time after inoculation. The isolates were able to invade fruit at the stalk and eye ends and where the skin had been pricked. No apparent infection followed spraying leafy shoots or flowers of Bramley's Seedling trees with bacterial suspensions and there was no visible reaction after hypodermic inoculation of bacterial suspensions into apple shoots.
THE INCIDENCE OF CERTAIN SEED‐BORNE DISEASES IN COMMERCIAL SEED SAMPLES
Authors: MARSHALL GILLIAN M.
Published: February 2008

Samples of commercial wheat seed submitted to the Official Seed Testing Station, Cambridge, have been examined from 1918 to 1957 for the presence of bunt balls (Tilletia caries (DC.) Tul.) and earcockles (Anguina tritici (Stein.) Filipjev) and the incidence of these organisms is reported.

The highest proportion of contaminated samples was found in 1921 (33% with bunt balls and 9% with earcockles). Since then incidence has decreased rapidly and is now steady at less than 1% with bunt balls and nil or less than 0.1% with earcockles. Low bunt‐contamination was confirmed by finding no bunt spores in 122 samples in 1957.

The survey illustrates the effective control and almost complete elimination of a seed‐borne disease and pest in the United Kingdom.

No seasonal effect on the incidence of either pathogen was found nor was any varietal susceptibility to bunt detected.
THE DETERMINATION OF THE REACTION OF BARLEY VARIETIES TO LOOSE SMUT
Authors: MALIK M. M. S. , BATTS C. C. V.
Published: February 2008

The inoculation of barley with loose smut (Ustilago nuda) using various techniques has given results which do not reflect the known behaviour of varieties under natural conditions. No consistent results have been obtained, but all the varieties thus inoculated could become infected. No variety therefore possessed true physiological resistance and in the field some must escape infection. The inoculation techniques obviously overcame this escape.

A method has been devised which, with the varieties used, has reflected their behaviour in the field. Drops of coloured water or spore suspension are allowed to fall from a height on to ears at anthesis. Grains on the ears of varieties which do not become infected in the field do not become coloured or infected (depending on the drops used), while grains of varieties susceptible in the field do become coloured or infected. This is due to the glumes of the former group of varieties remaining closed, and so preventing access of smut spores under natural conditions.
THE USE OF A MULTIPLE‐TRANSFER METHOD IN PLANT VIRUS TRANSMISSION STUDIES—SOME STATISTICAL POINTS ARISING IN THE ANALYSIS OF RESULTS
Authors: GIBBS A. J. , GOWER J. C.
Published: February 2008

The frequency of success of attempts to transmit a virus disease from one plant to another has long been used to measure the effects of any of the factors which influence transmission. Samples are taken from the population under test (e.g. vectors, diseased plants, etc.), and usually one sample is tested on each test plant; this is binomial sampling. However, in the procedure we name the ‘multiple‐transfer method’ more than one sample may be tested on each test plant. This increases the number of samples tested without increasing the number of test plants used, and errors due to heterogeneity in the population under test are therefore minimized. Results from experiments using the multiple‐transfer method may be evaluated by using the maximum likelihood estimator. The method is particularly reliable when the proportion of infected samples being studied is small, but can lead to considerable over‐estimation when the proportion is high.
THE TOXICITY OF ZINC SULPHATE TO RAINBOW TROUT
Authors: LLOYD R.
Published: February 2008

The toxicity of zinc sulphate to rainbow trout (Salmo gairdnerii Richardson) has been investigated in waters of different chemical and physical properties.

Zinc sulphate was less toxic to rainbow trout in hard water than in soft water; when the log concentration of zinc was plotted against log median period of survival of the fish the dose response curve was linear in a very soft water, and curvilinear in a hard water, approaching an apparent threshold concentration. Solutions of zinc sulphate containing calcium chloride were less toxic than those containing an equivalent concentration of calcium as bicarbonate.

An increase in temperature decreased the survival time of rainbow trout in solutions of zinc sulphate in a hard water, but the threshold concentration was not appreciably affected by changes in temperature.

A reduction in the dissolved oxygen concentration of the water increased the toxicity of zinc sulphate, but the effect was reduced when the fish were previously acclimatized to the lower oxygen concentration of the test.

The cause of death of fish in solutions of zinc sulphate was not by the precipitation of mucus on the gills but probably by damage to the gill epithelium.
SOME FIELD HABITATS OF MITES OF STORED FOOD PRODUCTS
Authors: GRIFFITHS D. A.
Published: February 2008

Forty‐seven samples were collected from stacks of hay, corn and straw and from permanent grassland in the East Midland counties of England. The living mites were extracted and all except the Oribatei were identified. Records were kept of the occurrence of those mites associated with stored food products, of the mites Forcellinia fungivora Oud. and Alliphis halleri Can., and of the beetle Enicmus minutus L.

Fifty‐two species of mites were identified of which twenty‐two were associated with stored food and food stores. Twenty‐one stored‐product species were collected from hay‐ and strawstacks and five from grassland. Acarus siro L., a major pest of stored cereals and cereal products, was the dominant mite in stacks and was also found in grassland samples. Tyrophagus longior Gerv. was similarly distributed and occurred almost as frequently. The motile hypopial stage of Acarus siro was found in 43% of the stack samples; it was attached to mites, beetles and other invertebrates. Its distribution pattern resembled that of the fungus beetle Enicmus minutus. Tyrophagus palmarum Oud., an uncommon stored‐product mite, was the dominant species collected from grassland samples.

It is concluded that: (a) all the mites commonly associated with foodstuffs stored indoors are present in the outdoor habitat afforded by stacks; (b) Acarus siro and Tyrophagus longior are dominant in stacks and both appear to be field dwellers; (c) T. palmarum appears to be a successful field dweller and its occasional association with stored food may be accidental; (d) the dominant warehouse partnership of Acarus siro and Glycyphagus destructor does not occur outdoors; here Tyrophagus longior replaces Glycyphagus destructor; (e) species of the family Glycyphagidae appear to live mainly in haystacks sited in stackyards; and (f) considering how the mites were acquired, grainstacks standing in the open field have a peculiar combination of dominants, namely: Acarus siro, Tyrophagus longior, T. palmarum and Alliphis halleri.
FIELD STUDIES ON WHEAT‐BULB FLY INFESTATIONS
Authors: RAW F.
Published: February 2008

An account is given of two experiments done on commercial farms in Essex to study the effect of tilth, cultivation and seed rate on wheat‐bulb fly infestation and the effect of infestation on yield. Heavier infestations developed on rough fallows and those cultivated during the oviposition period, than on smooth fallows and those not cultivated during the oviposition period. These results confirmed those of an earlier experiment done at Rothamsted. At each level of infestation, more larvae survived on plots sown at 3 bus./acre than on plots sown at 2/3 or 1 bus./acre. Although some plots had a high larval population no effect of infestation on yield was observed even at the lower seed rates. This is attributed to early sowing. The extent to which the cultural treatments studied can be used to control wheat‐bulb fly infestations is discussed.
OSCINELLA FRIT L. IN SOUTH WALES. THE RELATIONSHIP BETWEEN SOWING DATE, PLANT DEVELOPMENT AND PROGRESS OF ATTACK IN SPRING OATS
Authors: FIDLER J. H. , WEBLEY D.
Published: February 2008

The degree of lateness of sowing of spring oats in south Wales is reflected in a proportional increase of frit‐fly damage to the shoots. Late‐sown crops are also more subject to heavy attacks on grain than those sown earlier.

Equations are given relating the development of frit‐fly attack both to the growth of the plant and to the date of sowing.
DIDYMELLA STEM‐ROT OF OUTDOOR TOMATOES
Authors: KNIGHT DOROTHY E. , KEYWORTH W. G.
Published: February 2008

Experiments were made during 1954‐7 on the control of Didymella stem‐rot of tomatoes, by applications of various fungicides. The toxicity of a wide range of compounds to the fungus and to tomato plants was determined in the laboratory and promising compounds were then tested in the field. There were two main test methods, in both of which the plants were infected artificially at varying periods before or after treatment with the fungicides. In one method the inoculum was applied to leaf scars and in the other to the stem bases, the fungicides being sprayed on to the same sites.

Of the compounds tested, maneb was the most successful, showing both eradicant and protectant properties at 1 and 2%. Captan (0.25 and 0.5%) was a good protectant but was less effective as an eradicant. Attempts were made to test the compounds under conditions of natural spread of the disease but this was so slight that the results were not conclusive.
FIELD SPRAY TRIALS AGAINST WILDFIRE AND ANGULAR LEAF SPOT OF TOBACCO IN RHODESIA*
Authors: COLE J. S.
Published: February 2008

Field tests in Southern Rhodesia compared several antibiotics with copper fungicides for the control of wildfire and angular leaf spot of tobacco.

When streptomycin‐sensitive strains of the pathogen were used, streptomycin gave the best control. During one test, strains of Pseudomonas tabaci developed which were resistant to streptomycin: this was followed by a rapid breakdown of control. In another test, which compared streptomycin, oxytetracycline, neomycin, chlortetracycline and copper, streptomycin was the only effective spray. Cultures, isolated at the end of this test, showed resistance to all the antibiotics except chlortetracycline, but they lost their pathogenicity during laboratory tests. Oxytetracycline was generally no better than the lower rate of copper, and in one test it was ineffective. When variants resistant to streptomycin were used, a mixture containing oxytetracycline and streptomycin at quarter‐strength and copper at half‐strength was slightly better than full‐strength copper or a mixture of half‐strength copper and oxytetracycline.

Half‐strength streptomycin and copper was slightly better than full‐strength copper or half‐strength streptomycin and oxytetracycline, against a mixture of streptomycin‐resistant and sensitive variants of P. tabaci.
THE USE OF ENDRIN AND OTHER INSECTICIDES AGAINST LETTUCE ROOT APHID, PEMPHIGUS BURSARIUS L
Authors: DUNN J. A.
Published: February 2008

Several insecticides have been used as protectants against lettuce root aphid, including, in 1955, lindane, schradan, aldrin and endrin; the last‐named giving the most promising results. With a dressing of an equal weight of 50% endrin dust added to lettuce seed, 86% reduction in aphid numbers was obtained. In 1957, a seed dressing with endrin also gave a good control, which was superior to that obtained with thimet 44D. However, in 1956 and 1958 endrin seed dressing failed to control the aphid. When a seed dressing with endrin was supplemented by an endrin spray applied to the seedlings a consistently good control resulted.

A high level of aphid control was obtained in 1958 with two sprays of diazinon applied along the lettuce rows, the first applied after singling and the other at the early rosette stage. Diazinon or endrin, applied to the soil at 4 lb. actual insecticide/acre and rotavated into the top 3 in. before sowing, also gave high levels of control.

No recommendations for the use of endrin on lettuce can be made until levels and persistence of residues are known.
INSECTICIDAL CONTROL OF PAEDOGENETIC CECID LARVAE IN MUSHROOM BEDS
Authors: HUSSEY N. W. , WYATT I. J. , HUGHES J. T.
Published: February 2008

γ‐BHC, incorporated at 50 p.p.m. in mushroom compost during the last turn of composting delayed the reproduction of paedogenetic cecid larvae without reducing the yield of mushrooms. Other insecticides were less satisfactory as they either did not control the larvae, were not sufficiently persistent or decreased the yield. Large cecid populations did not depress yields on normal composts but a proportion of the larvae migrated on to the sporophores, thus reducing the value of the crop.