bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on blight (Phytophthora infestans) and resistant potatoes at Toluca, Mexico
Authors: LAPWOOD D. H.
Published: February 2008

A late blight epidemic studied at Toluca, Mexico, in 1962 may have started from stems infected at soil level by soil‐borne Phytophthora infestans. Its severity was demonstrated by the large differences in the rate foliage was destroyed and in yield of tubers between fungicide‐sprayed and unsprayed susceptible and resistant cultivars. The foliage resistances of some Mexican and European cultivars were compared using conventional blight keys and recording the destruction of marked leaves. Cultivars reacted in four ways: (1) Up‐to‐Date and Alpha leaves were infected and killed soon after plants emerged; (2) Bertita, Conchita and Florita abscissed many infected lower‐canopy leaves, and many infections on upper leaves aborted; (3) Elenita leaves had a few lesions in which the fungus grew slowly but remained alive; (4) Greta showed no infection until the potato plants met between rows but then infections developed rapidly and the foliage soon died. Mexican cultivars, except for Elenita, had few blighted tubers; susceptible European cultivars were killed before many tubers formed.

Most spores were released during the morning, as in Europe, and leaf infection seemed associated with days with rain when much of the night remained humid. Cool nights lengthened incubation and generation times.
Properties of cherry ring mottle, a distinctive strain of prune dwarf virus*
Authors: RAMASWAMY S. , POSNETTE A. F.
Published: February 2008

A virus was transmitted from sweet cherry trees with cherry ring mottle disease to cucurbitaceous plants with the aid of liquid nitrogen, caffeine or polyethylene glycol, which were more effective than sodium diethyldithiocarbamate, polyvinylpyrrolidone and other materials used in sap‐transmission studies. The virus was transmitted from dormant buds, petals, young leaves, anthers and pollen. Of 172 herbaceous species and varieties tested, twenty‐five (thirteen spp.) became infected with virus. Ribes nigrum and peach seedlings were also infected. Of the systems produced in woody plants, those in Italian Prune resembled the symptoms caused by prune dwarf virus, but those in other Prunus spp. did not. In cucumber extracts the thermal inactivation point was between 40 and 44 d̀C; dilution end‐point was 1/16 to 1/32 and longevity in vitro 8–16 h. Formaldehyde (4%) fixed the particles and preserved their shape for electron microscopy; they were spherical, with a mean diameter of 24 nm. The virus reacted with prune dwarf virus antiserum but differed in several ways from other isolates
Effects on Myzus persicae (Sulz.) and transmission of beet yellows virus of applying certain trace elements to sugar beet
Authors: RUSSELL G. E.
Published: February 2008

Applications of lithium chloride (LiCl), zinc sulphate (ZnSO4) or nickel sulphate (NiSO4) to the roots of sugar‐beet plants in the glasshouse encouraged settling on the leaves of adult apterae from a clone of Myzus persicae (Sulz.); conversely, treatment with boric acid (H2B2O7) inhibited aphid settling. Larviposition of M. persicae was increased by NiSO4 and tin chloride (SnCl2). Viruliferous M. persicae transmitted beet yellows virus (BYV) more efficiently to plants treated with LiCl or H2B2O7 than to those treated with copper sulphate (CuSO4), ZnSO4 or SnCl2. The sulphate and chloride anions of the applied chemicals appeared to have little effect on M. persicae and virus transmission.

It is suggested that applications of trace elements to sugar beet affected M. persicae and virus transmission by changing the concentrations of trace elements in the aphids' diet and by altering the metabolism of the leaf tissues in the host plant.
Studies on plant growth‐regulating substances: XXXII. Chlorosubstituted α‐hydroxy‐and α‐methoxy‐phenylacetic acids
Authors: CHAMBERLAIN VALERIE K. , WAIN R. L.
Published: February 2008

The plant growth‐regulating activities of all the mono‐ and di‐chloro‐substituted α‐hydroxy‐phenylacetic (mandelic) acids and their methoxy derivatives have been determined in the wheat coleoptile cylinder, pea segment and pea curvature tests. In general, chloro‐substituted α‐hydroxy acids were less active in all three tests than the corresponding α‐methoxy acids. The α‐methoxy compounds and the dichloromandelic acids were more active in pea than in wheat tissues.

These results are discussed in relation to the plant growth‐regulating activities of the corresponding phenylacetic and phenoxyacetic acids.
Apple stem‐grooving virus: propagating hosts and purification
Authors: UYEMOTO J. K. , GILMER R. M.
Published: February 2008

Isolates C431 and DGEV of apple stem‐grooving virus infected Zucchini squash (Cucurbita maxima) and pumpkin (C. pepo) systemically; these hosts were superior to Chenopodium quinoa for propagating the virus. Virus concentrations were assayed by counts of local lesions on cowpea (Vigna sinenis). Good yields of virus were concentrated from Zucchini squash sap clarified with bentonite or chloroform‐bentonite and purified by densitygradient centrifugation and zone electrophoresis. Filamentous virus particles 615 nm (C431) and 640 nm (DGEV), virtually free of host constituents and only slightly aggregated, were observed in electronmicrographs.
An analysis of the effects of nutrient supply on the growth of potato crops
Authors: DYSON P. W. , WATSON D. J.
Published: February 2008

Fertilizer nitrogen did not delay tuber initiation by the potato variety King Edward in the field, but slowed the early growth of tubers. Later, N hastened tuber growth and the largest amounts prolonged it. Leaf and stem growth were increased by N from an early stage. Leaf area index (L) reached maxima of 2.5 to 3.0 with the largest amounts of N, and 1.0 with no nitrogen: L decreased after late July, faster with increased N, and only the largest amount prolonged the life of the haulm. N increased leaf area duration (D) by up to 125% in both years. D was 21% greater in 1964 than 1963, and net assimilation rate in August and September was larger; consequently mean yield was 50% more in 1964. Uptake of nitrogen and N % of dry matter were increased by increasing nitrogen. The N % of tuber dry weight remained constant or increased slightly from about 2 weeks after tuber formation, while N % of the leaves and stems decreased rapidly, and much N was transferred from tops to tubers. The 1964 results suggest that tuber growth depends on continued nitrogen uptake by the plant.

P and K had small effects compared with those of N. K increased leaf area duration by 9% in 1963 and 3% in 1964, and yield by 11 and 8% respectively. P increased leaf area duration by 17% and yield by 9% in 1964. K had very small effects until the end of the season, when it prolonged the period of growth. P increased growth rates of all parts of the plant up to 4 weeks from emergence, and the differences in dry weight at that time persisted to maturity but did not increase.
Studies on plant growth‐regulating substances: XXXIV. The effects of 3,5‐dichlorophenoxyacetic acid on plant growth
Authors: FIRD R. D. , WAIN R. L.
Published: February 2008

The effect of 3,5‐dichlorophenoxyacetic acid (3,5‐D) in reducing the shoot growth of tomoato plants has been investigated and evidence is presented which suggests that the inhibition of shoot growth which occurs is not the result of a competitive antagonism between 3,5‐D and endogenous auxin or gibberellins. A reinvestigation of the effect of 3,5‐D on certain auxin‐induced responses failed to reveal evidence which would support the previous classification of 3,5‐D as an ‘anti‐auxin’.
The seasonal release of spores of Nectria galligena from apple cankers in Northern Ireland
Authors: SWINBURNE T. R.
Published: February 2008

Trapping of ascospores and conidia of Nectria galligena Bres. released from cankers on Bramley's Seedling apple trees over a period of three years showed that ascospores were most prevalent in the spring and early summer, and conidia from early summer to late autumn. Few ascospores were released in late summer or mid‐winter but a minor period of discharge occurred in autumn.

The distribution of cankers within trees in various orchards was also examined, and most were found to occur at the junctions of different seasons' growth. Possible reasons for this are discussed.
Lesion and epidemic development of Alternaria longipes (Ell. & Ev.) Mason on tobacco
Authors: NORSE D.
Published: February 2008

Lesion development of A. longipes was studied in the glasshouse and in the field. The incubation period on glasshouse plants varied from 3 to 8 days. Some pinpoint lesions failed to develop, and lesion development on the upper leaves of pot plants was less than on the lower ones. The maximum estimated lesion multiplication rate was 2.1 daughter lesions/mother lesion/day, but was generally ≤ 0.6.

Epidemic development was studied in four seasons (1966 to 1969) by weekly assessment of infection levels on alternate leaves. Leaf area, airborne inoculum concentrations, air, leaf and soil temperature, soil moisture, saturation deficit, rainfall, duration of leaf wetness, and wind speed were also measured. Relative infection rates varied from 0.17‐0.26 units/day. Slow disease development in 1968 (r = 0.17 units/day) could be related to the adverse effects of climate on host development and on infection processes. The relative rate of infection varied widely at different stalk position (0.16‐0.29 units/day in 1966) and at different times at the same stalk position (0.17=0.48 units/day at position 25 in 1969). There was no consistent relationship between the stalk position of leaves and the rate at which they were infected. Similarly there was no consistent relationship between the rate of infection of whole plants or of leaves at a particular stalk position and climatic or inoculum factors, although during limited periods, changes in one or other of these factors did coincide with an alteration in the relative rate of infection.

The interpretation of rates of infection and the theoretical results of greater field hygiene are discussed.
Bait shyness of two gerbils, Tatera indica indica Hardwicke and Meriones hurrianae Jerdon
Authors: PRAKASH ISHWAR , JAIN A. P.
Published: February 2008

Two rodents, Tatera indica indica Hardwicke and Meriones hurrianae Jerdon, developed aversion to zinc phosphide after one day's exposure to a sublethal dose. The poison shyness persisted for at least 115 and 35 days, respectively.
Verticillium wilt of cacao in Uganda: symptoms and establishment of pathogenicity
Authors: EMECHEBE A. M. , LEAKEY C. L. A. , BANAGE W. B.
Published: February 2008

Pathogenicity tests have shown that Verticillium dahliae Kleb. causes a vascular wilt disease of cacao (Theobroma cacao L.) in Uganda. Isolates of V. dahliae from cacao, okra (Abelmoschus esculentus Medik.), and cotton (Gossypium hirsutum L.) induced similiar symptoms on artificially inoculated cacao seedlings.

External symptoms of the disease include acute wilting, foliar chlorosis and abscission, stunting of roots and shoots, and production of suckers at lower nodes of severely affected plants. The internal symptoms are vascular discoloration, tylosis, and presence of gum deposits and mycelium of V. dahliae in xylem vessels.
Pepper veinal mottle virus‐a new member of the potato virus Y group from peppers (Capsicum annuum L. and C. frutescens L.) in Ghana
Authors: BRUNT A. A. , KENTEN R. H.
Published: February 2008

Pepper veinal mottle virus (PVMV), a previously undescribed virus widespread in Capsicum annuum and C. frutescens in the Eastern Region of Ghana, is acquired and inoculated in 2 min feeding periods by aphids (Myzus persicae and Aphis gossypii); it is transmissible by inoculation of sap to eleven of fifteen Solanaceae and to five of forty‐six other species within three of seventeen other families. The virus was propagated in Nicotiana clevelandii and Petunia hybrida, and assayed in Chenopodium quinoa, C. amaranticolor and C. murale. Sap from Capsicum annuum was infective after dilution to 10‐3 but not 10‐4, after 10 min at 55 but not 60oC, and after 7 but not 8 days at 25oC. Lyophilized sap from P. hybrida was infective after 6 years in vacuo.

Yields of 10–25 mg of virus per kg of leaf tissue were consistently obtained from P. hybrida or N. clevelandii by extracting systemically infected leaves in 0.5 M borate (pH 7.8) containing 0.2% mercaptoethanol and chloroform, followed by repeated precipitation with 50 g polyethylene glycol (M.W. 6000) per l, several cycles of differential centrifugation and centrifugation in sucrose density‐gradient columns.

Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 6% nuclei acid (A 260/280 = 1.25; A 260/246 = 1.27) and contained numerous unaggregated and unbroken filamentous particles c. 770 times 12 nm which sedimented as a single component with a sedimentation coefficient (so20,w) of 155 S. PVMV contained RNA (moles %: G = 24, A = 23, C = 27, U = 26), and a single protein species with a molecular weight of 32000–33000 daltons. PVMV was not serologically related to potato virus Y (three strains), or to twelve other morphologically similar viruses, and seems to be a distinct member of the potato virus Y group.

The cryptogram of PVMV is R/(I):*/(6):E/E:S/Ap.
Organo‐mercury fungicide treatment of sugar‐beet seed
Authors: BYFORD W. J.
Published: February 2008

Sugar‐beet seed treated with I% (v/w) of 1.2% ethyl mercuric phosphate (EMP) solution applied as a mist gave seedling emergence in the field and final plant stand comparable to those of seed treated by 40 ppm EMP steep. However, when the mist‐treated seed was stored after treatment, phytotoxic effects sometimes developed; consequently the treatment is not considered a suitable replacement for the EMP steep, now given to all sugar‐beet seed in Britain.
The life‐cycle and host preferences of the bird cherry‐oat aphid, Rhopalosiphum padi L., and their bearing on the theories of host alternation in aphids
Authors: DIXON A. F. G.
Published: February 2008

Emigrants of the host‐alternating bird cherry‐oat aphid fly from the primary host to various grasses before the end of June, even in the absence of natural enemies on bird cherry. They fly before the leaves of bird cherry mature and at a time when numbers of insect predators are rapidly increasing. In the autumn gynoparae and males return to bird cherry whose senescing leaves again provide the aphids with a rich source of food. The growth efficiency of R. padi on bird cherry and oats indicates that the quality of the available food on the two hosts is markedly different.

Apterous exules prefer oats to young bird cherry leaves and survive best on oats. Gynoparae prefer bird cherry leaves and only successfully produce offspring on the primary host. This, and other work published on R. padi, support the premise that a change in the aphid's preferences causes the change of host.

The dual‐discrimination theory of host alternation in aphids is examined in the light of this and other published work.
The role of the apple spray programme in the protection of fruit buds from powdery mildew
Authors: BUTT D. J.
Published: February 2008

Comparisons of programmes, which differed in the dates on which high‐volume sprays of dinocap (0.019 %) were omitted, indicated that applications in the period from green cluster to early fruitlet protected the bourse buds of apple cv. Cox's Orange Pippin from infection, and so controlled the number of mildewed blossom trusses in the following year. This role of the sprays in preventing primary mildew declined after the early fruitlet stage. The existence of two phases of the disease was confirmed, and although dinocap at late blossom and early fruitlet contributed to the control of preliminary infections of secondary mildew on vegetative shoots, the latter phase did not become severe until after the peak invasion of bourse buds. Fewer than 20% of the fruit buds which produced primary‐mildewed blossom in 1968 were succeeded by healthy fruit buds in the next year; this poor recovery was not improved by dinocap applied during the flowering period in 1968.

Fruit‐set and crop of James Grieve and Cox's Orange Pippin were reduced in 1968 by dinocap applied at green cluster and pink bud, or at full blossom and petal‐fall, but no deleterious effects were produced by equivalent sprays in 1969. The need for mildew control during flowering is discussed in relation to phytotoxic sensitivity.
A study of seed lots of peas (Pisum sativum L.) differing in predisposition to pre‐emergence mortality in soil
Authors: MATTHEWS S.
Published: February 2008

In three seed lots the condition of the cotyledons was found to be important in denning seeds predisposed to pre‐emergence mortality. Such seeds readily exuded materials into seed‐steep water, were rapidly infected by Pythium spp. and showed intensely stained cotyledons after being in solutions of tetrazolium chloride. In soil, infection of the cotyledons was found to occur before infection of the seedling axis and occurred in normal seed if disks of cotyledon material were placed in the soil next to the seed.

It is suggested that cotyledons influence predisposition by either increasing exudation around the seed and stimulating the fungal pathogen or by acting as a food base for the fungal hyphae which infect and kill the seedling axis.
Grain yield and quality of wheat as affected by chlormequat (2‐chloroethyl‐trimethyl ammonium chloride)
Authors: LOWE L. B. , CARTER O. G.
Published: February 2008

Three field experiments studying the effect of chlormequat (CCC) on the grain yield of spring wheat and the quality of the grain for baking purposes were made. In the first, CCC applied as a spray during the stage of rapid internode elongation proved more successful than application as a mixture with superphosphate drilled with the seed at sowing. Both methods prevented lodging and the depression of yield which occurred in the control plots. In the other two experiments the sole method of CCC application was by spraying.

In all three experiments CCC‐treated plots had more ears per unit area and grains per ear than control plots; the one exception being at the lowest plant density derived from a seeding rate of 24 kg/ha. CCC helped prevent weather damage to the grain and as a result baking performance of the flour from treated plots was superior to that from the untreated plots.
Cereal aphids, their parasites and predators caught in cages over oat and winter wheat crops
Authors: JONES MARGARET G.
Published: February 2008

The trapping of alate aphids in emergence cages each 1 yd2 (0–83 m2) over cereal crops from mid‐June to the end of July, 1964 to 1971, always revealed colonies of cereal aphids within the crop.

Four species, Sitobion avenae, S. fragariae, Metopolophium dirhodum and Rhopalosiphum padi occurred every year in different proportions. Alate aphids from winter wheat were most numerous in 1968 and fewest in 1967. Alatae developed slightly earlier in cages than in the field and peak catches were a few days earlier than in a nearby 12‐2 m suction trap.

Cereal aphid colonies were adversely affected by bad weather in May, e.g. in 1969, and by predators. Coccinellidae (chiefly Propylea 14‐punctata) were the dominant predators in 1971 and 1968, Syrphidae in 1966, 1971 and 1968 and Chrysopidae in 1970. Parasites belonging mainly to the genus Aphidius were numerous every year. When hyperparasites such as Asaphes vulgaris, Lygocerus sp., Conostigmus sp. and Phaenoglyphis sp. were abundant as in 1967, they affected numbers of aphids in the current year and increased them in the following year (1968), possibly by hindering early, heavy parasitism. Hyperparasites could have an important influence in fluctuations of cereal aphid populations from year to year. Aphids of one species or another are always present in cereal crops in sufficient numbers during the summer months to provide copious quantities of honey dew, and this is unlikely to be a limiting factor in the biology of the wheat bulb fly, Leptohylemyia coarctata.
Effect of numbers of fungicidal sprays and dates of application on control of celery leaf spot (Septoria apiicola) and on chemical residues
Authors: RYAN E. W. , GORMLEY T. R. , KAVANAGH T.
Published: February 2008

Experiments at two sites in each of three seasons showed that successful control of celery leaf spot depended more on the choice of fungicide than on the number of sprays and the dates of application. Organotin fungicides gave best control of celery leaf spot and with one exception residues were not detected even when the last application was given 4 weeks before harvest rather than 6 weeks.
Assessing the age of field female wheat bulb flies (Leptohylemyia coarctata)
Authors: JONES MARGARET G. , BARDNER R. , FLETCHER K. E.
Published: February 2008

From 1967 to 1971, wheat bulb fly females caught by sweeping from a number of localities contained mature eggs from the third week of July to the end of August.

In 1971 when female wheat bulb flies were caught by sweeping, by white water traps, by suction traps as well as by light traps, the first flies containing mature eggs were caught 29 days after the first detected emergence while the first batch was laid 29–58 days after first emergence. The peak period of egg laying occurred in the fourth week of July, 24–38 days after the peak emergence. The second batch of eggs was laid when the flies were 8 weeks old, 29 days after the first; the peak for this batch was 35 days after the first. A few females laid a third batch of eggs 28 days after the first record of the laying of the second batch. A female that lives sufficiently long to lay the third batch of eggs is at least 12 weeks old. In 1970, when emergence started earlier in June, ripening and laying of eggs of the three batches was also earlier.

After the harvest of cereal crops more females were caught by white water traps placed on the fallow than by other methods.

The most important pathogen affecting adult wheat bulb flies was a fungus, probably Entomophthora muscae. When infection occurred early in July, fewer eggs from the first batch were laid than when infection developed later. Fewer flies were infected in 1971 than in 1970.

To be effective against wheat bulb fly in the early spring, control measures‐should be applied against adults before their eggs mature in early July of the preceding year.
Induction of sporulation of fungi isolated from Dactylis glomerata seed by exposure to near‐ultraviolet radiation*
Authors: LEACH C. M. , TULLOCH MARGARET
Published: February 2008

Pure cultures of fifty‐two species of plant pathogenic and saprophytic fungi isolated from orchard (cock's‐foot) grass seed (Dactylis glomerata L.) were incubated either in total darkness or exposed to a diurnal cycle of near‐ultraviolet (NUV) radiation (12 h NUV/12 h darkness). Twenty‐four species sporulated only after exposure to NUV including seven species of Drechslera, five species of Fusarium, as well as species olAscochyta, Photna, Septoria, Pyrenochaeta, Rhynchophoma and Stagonospora; six species sporulated moderately in darkness but more profusely following exposure to NUV; twenty species sporulated whether they were irradiated or not; and only two species failed to sporulate. To assess the pathogenic fungal microflora of orchard grass seed accurately, seeds should be incubated under a daily regime that includes NUV to induce sporulation.
Effect of Ophiobolus graminis infection on the assimilation and distribution of 14C in wheat
Authors: ASHER M. J. C.
Published: February 2008

The uptake of 14C and movement of 14C‐labelled assimilates in wheat plants inoculated with Ophiobolus graminis was examined following exposure of the second youngest leaf to 14CO2. Autoradiographs of plants with infected seminal roots showed that assimilates were not translocated past the sites of root infection but accumulated in the undamaged portions of infected root systems, in particular the developing crown roots. There was no evidence that assimilates accumulated in the vicinity of O. graminis lesions.

The net assimilation of 14CO2 by wheat plants over a 5 h feeding period was not significantly affected by O. graminis infection. However, infection reduced the amount of 14C lost through respiration. Infection delayed the transfer of labelled assimilates from the fed leaf to the remainder of the plant but increased the proportion translocated to the roots. The latter effect was not apparent when infected plants were continuously irrigated during, and for 20 h following, the feeding period.
Relationships between a parsley virus, nasturtium ringspot virus and broad bean wilt virus*
Authors: FROWD J. A. , TOMLINSON J. A.
Published: February 2008

A non‐persistent, aphid‐transmitted virus (PV3) found in parsley in Britain was cultured in Chenopodium quinoa. It was mechanically transmissible, relatively stable in vitro and had polyhedral particles approximately 30 nm in diameter.

Virus particles occurred within the cells as crystals, scrolls and tubular structures. In purified preparations, virus particles were mostly aggregated, especially in the presence of salts.

PV3, nasturtium ringspot virus and broad bean wilt virus were found to be closely related serologically.
The translocation of herbicide from bean (Viciafaba) to broomrape (Orobanche crenata)
Authors: WHITNEY P. J.
Published: February 2008

Application of 14C‐labelled 2,4‐D to bean plants parasitized by broomrape led to a concentration of the herbicide in the immature parasite that was up to fourteen times that in the bean root. Not all substances are translocated in this way. 22Na in sodium chloride was not moved in significant amounts away from the site of application, but sucrose was found to be translocated to the parasite.

Application of 2,4‐D,2,4,5‐T, N.A.A. and D.N.P. to mature Orobanche under field conditions had little effect.

2,4‐D is not considered a suitable herbicide for the control of Orobanche in bean crops because of the high sensitivity of the host of this compound. It is thought, however, that the application to the host of a systemic herbicide which becomes concentrated in the parasite to a toxic level could well be an efficient way of controlling this type of parasite.
An assessment of some new treatments for the control of rotting of stored apples
Authors: BURCHILL R. T. , EDNEY K. L.
Published: February 2008

Benomyl (0.025% a.i.) and thiabendazole (0.05 % a.i.) applied in July, August and September to apple trees cvs. Sunset and Cox's Orange Pippin gave slightly better control of Gloeosporium spp. rots in stored fruit than captan (0.1% a.i.) applied at similar intervals. On Cox's Orange Pippin, treatment with captan at 0.1 % a.i. in July and at 0.2% a.i. in August was as effective as three sprays at 0.1 % a.i. in July, August and September in controlling both Gloeosporium spp. and Nectria galligena rots. Benomyl applied in the spring and early summer to control apple scab on orchard trees reduced the incidence of Gloeosporium spp. and Monilia fructigena in stored fruit. Pre‐harvest sprays of benomyl and captan gave good control of rotting caused by N. galligena but thiabendazole was ineffective. Post‐harvest dips of thiabendazole controlled rotting by Gloeosporium spp. butnot byN. galligena.
Specificity and host specialization of Puccinia chondrillina
Authors: HASAN S.
Published: February 2008

Various strains of Puccinia chondrillina, the Chondrilla rust, were collected during surveys in the Mediterranean, undertaken to discover biological control agents suitable for use in Australia against skeleton weed, Chondrilla juncea. Only the strain collected at Vieste (S.E. Italy) was highly virulent against the common Australian form of C. juncea. The specificity of this strain of the rust was tested by inoculation of many unrelated cultivated plants, related cultivated plants and closely related wild plants; all were immune to the rust. These tests satisfied the Australian plant quarantine authorities and this strain of the rust has now been introduced into Australia as a biological control agent for C. juncea.
Resistance to Rhynchosporium secalis in the winter barley cultivar Vulcan
Authors: HABGOOD R. M.
Published: February 2008

The six‐rowed winter barley cultivar Vulcan was found to be highly resistant to Rhynchosporium secalis in the field, although this resistance was not apparent in routine screening tests of barley genotypes carried out at the seedling stage. More precise seedling tests, using graded inoculum levels to derive dose‐response curves, showed that cv. Vulcan had an ED50 which was 4.8 times that of the susceptible, two‐rowed cv. Maris Otter, and 4.1 times that of cv. Maris Puma.

The inheritance of resistance was investigated at the adult plant stage in a cross with cv. Maris Otter. Although a clear‐cut segregation of the F3 progeny into resistant, segregating and susceptible phenotypes was not observed, the genetic variance of the F3 family means was compatible with the hypothesis of monogenic control of resistance. Resistance was inherited independently of the factor for six‐rowed head type.
Secondary leaf fall of Hevea brasiliensis: meteorological and other factors affecting infection by Colletotrichum gloeosporioides
Authors: WASTIE R. L.
Published: February 2008

The lower leaf surface of Hevea brasiliensis was more susceptible to infection by Colletotrichum gloeosporioides than the upper. Few lesions were produced if spore drops on susceptible leaves were allowed to dry. Lesion development after 72 h was quickest at 21 oC, slower at 26.5 oC and was stopped at 32 oC, probably because of bacteria in the inoculation drop. On leaflets aged 7 days from bud‐burst, the effective spore dose for 50% of leaflets infected (ED50) after 16 h incubation, was 260 spores and after 46 h, 120 spores/infection droplet; the minimum ED50 for the upper leaf surface was about 4 spores/mm2. Leaflets 15 days old, which are normally resistant, were rendered susceptible by abrading the surface with carborundum powder.

Spores caught in a Hirst spore trap reached a daily maximum at 23 h, at rates of up to 440 spores/m3 air/h, but fell to low concentrations as the humidity dropped during the daytime, and also during rain. There was some correlation between disease severity and duration of 97–100% relative humidity, and moderate to severe defoliation of clone PB 86 occurred when this reached 13.5 h/day. Rainfall increases infection by prolonging the period of atmospheric saturation and leaf wetness.
The effect of pH and composition of test solutions on the inhibitory activity of wyerone acid towards germination of fungal spores
Authors: DEVERALL B. J. , ROGERS PAMELA M.
Published: February 2008

Wyerone acid at 100μg/ml prevented germination of conidia of Botrytis cinerea Fr. in aqueous extracts of leaves of Vicia faba L., but it was inactive in water and some synthetic nutrient solutions though antifungal activity appeared when the pH of these media was adjusted to 4.0 or 4.5. In pollen diffusates (V.faba or Nicotiana glutinosd) wyerone acid had little activity even at pH 4.0. In malt extract at pH 4.5 wyerone acid was active against several other plant pathogenic fungi but not against B. cinerea. It was concluded that both pH and unknown components of natural media affected the fungitoxicity of wyerone acid.
Control of potato cyst‐nematode, Heterodera rostochiensis, in peaty loam soil by D‐D, aldicarb and a resistant variety of potato
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

In peaty loam soil in Cambridgeshire, 5.2 or 10.3 kg aldicarb/ha incorporated in the top‐soil before potatoes were planted controlled potato cystnematode (Heterodera rostochiensis Woll.) better than 384, 769 or 1153 kg D‐D/ha injected 15 cm deep into the top‐soil in the preceding autumn. 10.3 kg aldicarb/ha applied in 1968 and 1969 permitted King Edward potatoes (susceptible to H. rostochiensis) to grow well in infested soil and prevented multiplication of pathotypes of H. rostochiensis on Maris Piper potatoes (resistant to H. rostochiensis pathotype A). Although large amounts of D‐D applied in 1968 and 1969 increased the yield of King Edward potatoes in both years they did not control potato cyst‐nematode in the second year.
Changes in growth‐substance contents during growth of wheat grains
Authors: WHEELER A. W.
Published: February 2008

Samples of developing wheat grains were extracted at weekly intervals from ear emergence until maturity and the growth substances estimated by bioassay. Immature grains contained two cytokinins; one was similar to zeatin and another, with more cytokinin activity, had different properties. Ovules contained only small amounts of growth substances but at the end of anthesis the grains had a maximum content of cytokinin. The gibberellin content increased until 3 wk after anthesis then decreased; their auxin content increased until 4 wk after anthesis but decreased as the grains ripened and lost fresh weight. The husks contained smaller amounts of growth substances than the grains they surrounded. Exudates from young stems contained cytokinins and these may originate in the roots and move to the ears through the stems. The auxin in the grains was identified as indole‐3yl‐acetic acid and may be derived from the phenols present reacting with tryptophan.
Some effects of crowding on the biology of Megoura viciae
Authors: BONNER A. B. , FORD J. B.
Published: February 2008

CrowdingMegour a viciae(Buckton) on bean plants affects both the nymphs and adults. Crowded nymphs show a low mortality, develop more rapidly to produce light adults after a series of synchronized moults: isolated nymphs show a high initial mortality, develop more slowly to heavier adults, the duration of nymphal stages being extremely variable, with no synchronization of moulting. Development is discussed in terms of both weight gain and linear growth rate.

Crowding does not affect adult mortality but it does reduce the rate at which nymphs are produced. The significance of these findings in relation to the formation and maintenance of the aphid colony is considered, and possible controlling factors are discussed.
The extent and survival of contamination of potato stocks in Scotland by Erwinia carotovora var. carotovora and E. carotovora var.atroseptica*
Authors: PÉROMBELON M. C. M.
Published: February 2008

The following results were obtained when fifty‐seven bulk and crate‐stored commercial seed potato stocks from the East of Scotland were examined in 1966‐8 for contamination by pectolytic Erwinia spp. (1) Most tubers of all the cultivars and stocks examined, irrespective of whether they were obtained from blackleg‐infected or blackleg‐free crops, were contaminated with E. carotovora; (2) some 80% of the Erwinia isolates obtained were identified as var. atroseptica, the rest being var. carotovora; (3) the organisms survived in and on tubers for 6–7 months of bulk storage over the winter and up to planting time the following spring; (4) contrary to what is generally thought, the high incidence of contamination of all stocks, while suggesting that the seed itself is the major source of E. carotovora for the growing crop, emphasizes that other factors affect manifestation of blackleg in the field and soft rot in store.
Studies on broccoli necrotic yellows virus
Authors: TOMLINSON J. A. , WEBB M. J. W. , FAITHFULL ELIZABETH M.
Published: February 2008

Electron microscopy of infected D. stramonium cells showed that the virus particles occurred in the cytoplasm. Particles were mostly bacilliform and measured 297 ± 18 times 64 ± 4 nm. In negatively stained leaf homogenates, particles were mostly disrupted; intact particles measured 267 ± 20 times 69 ± 6 nm. In brussels‐sprout cells containing BNYV and CIMV, BNYV particles were rarely found compared with those of CIMV, and they occurred within and near CIMV inclusion bodies. BNYV particles were also found in extracts of virus‐carrying Brevicoryne brassicae.

Broccoli necrotic yellows (BNYV) and cauliflower mosaic (CIMV) viruses occurred together in naturally infected Brussels sprout plants, which showed conspicuous symptoms, and in cauliflower. BNYV was transmitted to and maintained in Datura stramonium and Hyoscyamus niger. It was partially purified from D. stramonium. Using these preparations, from which inhibitor had been removed, BNYV was manually transmitted to cauliflower, causing mild symptoms, and to Brussels sprout, causing a symptomless infection. BNYV also infected Sinapis alba but not cabbage, lettuce, Sonchus oleraceus or Plantago major. BNYV was transmitted by Brevicoryne brassicae but not by Myzus persicae, Hyperomyzus lactucae or Aleyrodes proletella.
Deposition of spores and other particles on vegetation and soil
Authors: CHAMBERLAIN A. C. , CHADWICK R. C.
Published: February 2008

The rate of deposition of 20–30 μm diameter particles, including spores and pollen grains, on plant and other surfaces, is determined, first, by the frequency at which particles strike the surfaces and, secondly, by the proportion retained on the surface rather than rebounding into the airstream.

Spores and pollen grains tagged with a radioactive marker were used to show that the impaction efficiency on leaves and stems depends very much on whether or not the surfaces are sticky or moist. If they are, the rate of deposition may approach that predicted aerodynamically. If the plant surfaces are dry, there is saltation of some spores and the effective rate of deposition is greatly reduced.
The effect of Tarsonemus fragariae Zimmermann (Acarina: Tarsonemidae) on strawberry yields
Authors: ALFORD D. V.
Published: February 2008

Experimental plots, arranged within commercial strawberry fields, were used to study the effect of Tarsonemus fragariae infestations on strawberry yields. Yields and the mean weight of individual fruits were inversely related to mite infestation levels. Yield reductions of over 50% were attributable to this pest.
Some effects of darkness and partial defoliation on the resistance of sugar beet to downy mildew
Authors: RUSSELL G. E. , EVANS GWENLLIAN M.
Published: February 2008

Seedlings of two susceptible sugar‐beet stocks were grown either in daylight or in darkness for 24 h before or after inoculation with Peronospora farinosa f.sp. betae. Post‐inoculation darkness did not significantly affect the percentage of inoculated plants that became infected but increased the percentage of plants on which the fungus sporulated in both stocks. The effects on sporulation of darkness before inoculation were more variable than those of post‐inoculation darkness.

In the same stocks removal of all leaves, except those in the bud, before inoculation increased the percentage both of plants which became infected and of those on which P. farinosa sporulated. Infection and sporulation were not significantly affected by defoliation in a more resistant stock.

Defoliation or darkness may have affected the concentration of certain sugars or amino acids in the bud leaves thereby changing the expression of polygenically‐controlled resistance to downy mildew.
Influence of organic soil amendments on Verticillium dahliae and on the microbial composition of the strawberry rhizosphere
Authors: JORDAN V. W. L. , SNEH B. , EDDY B. P.
Published: February 2008

A technique was developed for assessing the saprophytic activity of Verticillium dahliae, using a strawberry root extract medium. The germination of conidia and microsclerotia, and mycelial growth in soil, was inhibited by the addition of chitin, laminarin, wheat straw and oven‐dried green clover as soil amendments. A significant decrease in the number of viable propagules of the pathogen counted from soil, and in disease severity, was obtained with chitin and laminarin. More bacteria and actinomycetes were recorded from the rhizosphere of plants grown in chitin‐amended soil than from those in natural soil.
Field studies on halo‐blight of beans (Pseudomonas phaseolicola) and its control by foliar sprays
Authors: TAYLOR J. D.
Published: February 2008

In 1968 when conditions were favourable for the spread of infection (rainfall 243 mm June‐August), halo‐blight of beans initiated from 0.38% primary infection produced 33.8% infected pods but in 1969 (rainfall 112 mm June ‐August+38 mm irrigation water), a similar level of primary infection resulted in only 3.2% infected pods. In both years plant and pod infection were reduced by approximately 90% by sprays of streptomycin sulphate or copper oxychloride (0.1% a.i. 60 gal/acre (675 l/ha)) applied every 10 days from seedling emergence to flowering time.
Effects of ammonium and nitrate nutrition or take‐all disease of wheat in pots
Authors: HORNBY D. , GORING C. A. I.
Published: February 2008

Plant debris, naturaiiy infested with the take‐all fungus (Ophiobolus graminis), was washed from soil and added to a leached sandy loam, deficient in nitrate nitrogen (NO3‐N) and magnesium. Nutrient solutions containing potassium and phosphorus, with and without magnesium, were added to the amended soil unsupplemented, or with either NO3‐N, ammonium nitrogen (NH4+‐N), or both. Nitrification of NH4+‐N was inhibited by 2–chloro‐6–(trichloromethy1)‐pyridine (N‐Serve). After 38 days at 19°C, fewer plants had take‐all with N (75 or 100 mg/kg soil) than without and root systems were most discoloured and had most diseased axes when nutrients were not added. Plants given NH4+‐N developed less take‐all when magnesium was present. A comparison of forms of N in the presence of added magnesium showed that take‐all was least with a mixture of both forms of N, intermediate with NO3‐N alone and worst with NH4+‐N alone. The most extensive lesions on individual root axes occurred on plants given NH4+‐N. It is suggested that take‐all will be least when the amounts and ratio of NH4+‐N and NO3‐N are optimum for the growth of the host.
Similar effects of suspensions of copper oxychloride and kaolin on sprayed leaves*
Authors: EVELING D. W.
Published: February 2008

When dried on leaves, aqueous suspensions of copper oxychloride and of kaolin damaged the leaves similarly. With both, the damage was correlated with the rate the leaves lost water, which increased as the size of the suspended particles of copper oxychloride decreased. The damage seemed to arise mainly from a physical effect of the particles and not from copper reacting chemically.
Laboratory studies on the life‐histories of four enchytraeid worms (Oligochaeta) which inhabit sewage percolating filters
Authors: LEARNER M. A.
Published: February 2008

The life‐histories of four enchytraeid worms, Lumbricillus rivalis, Enchy‐traeus coronatus, E. buchholzi, and E. albidus which occur in sewage percolating filters, were studied under laboratory conditions at 8, 15 and 20°C.

The number of ova per cocoon varied from 0 to 50 (L. rivalis), 0 to 33 (E. coronatus), 1 to 9 (E. buchholzi) and 0 to 22 (E. albidus). The mean number of ova per cocoon was highest at 15°C for all species except E. coronatus which had a highest mean value at 8°C. The number of ova in cocoons was correlated with cocoon length (P < 0.001) for all species.

Cocoon production usually increased with temperature ranging from 0.8 cocoons per adult per week at 8°C to 2.0 at 20°C for L. rivalis, and from 1–4 to about 2.6 for E. coronatus and E. buchholzi.

The total number of ova produced by each E. coronatus (350 at 8°C to 550 at 20°C) was similar to that produced by each L. rivalis (600 at 8°C to 350 at 20°C) and was about five times greater than the total numbers produced by the other two species. Cocoon and ova production and the number of ova per cocoon varied with the age of the adult, usually reaching a peak soon after maturity.

Hatching success was low and generally 40–50 % of ova failed to develop; subsequent mortality among immature worms was about 10–20%.

Growth was more rapid at the higher temperatures; L. rivalis matured in about 26 days at 20°C, the clitellum forming when the worm was 13–14 mm long; data for the other species are 13 days and 5–6 mm (E. coronatus); 16 days and 3–4 mm (E. buchholzi); 28 days and 13–14 mm (E. albidus). The maturation period at 8°C was at least twice that at 20°C.

The generation period (cocoon to cocoon) was about a month at 20°C for all species except E. albidus (2 months), but as some species had longer reproductive periods than others the actual number of generations per year was highest in E. buchholzi, 7.0 per year, and lowest in E. albidus, about 3.3 per year, At 8°C all four species had between 1.4 and 2.8 generations a year.

A comparison of expected and observed population densities of L. rivalis and E. coronatus in a sewage percolating filter showed that neither achieved values approaching their potential summer densities although ample food was apparently available.

Of the four species studied only E. buchholzi produced viable ova without pairing.
The biology of Peronospora viciae on pea: the development of local and systemic infections and their effect on vining yield
Authors: PEGG G. F. , MENCE M. J.
Published: February 2008

The development of infection by Peronospora viciae (Berk.) Casp. was studied in field and plot experiments during 1967, 1968 and 1969. Numbers of primary systemically infected plants appeared shortly after emergence and reached a maximum by the end of May. Such plants acted as primary infectors and did not survive more than 3 weeks.

Maximal sporangial release occurred between 06.00 and 08.00 h BST with a peak at 07.00 h, after 1–2 h insolation. Inoculation of leaves at 10.30 h resulted in greater infection than inoculation at 20.00 h. The result suggested a possible maturation requirement of sporangia following release from the sporangiophore.

Initially the spread of foliar (local lesion) infection in the crop was sporadic and localized in cvs. Jade, Gregory, Dark Skinned Perfection (D.S.P.) and Frühe Kleine Pfälzerin (F.K.P.) during the 3 years. The number of plants of all cvs. with foliar infection reached 100% by mid‐June. Lesions rarely exceeded 15% of the leaf and stipular area of the mature plant. No effect of foliar lesions, at the highest level of infection, in haulm or seed fresh weight could be detected in cvs. F.K.P., Jade and D.S.P.

Secondary systemic infection occurred sporadically in field crops usually with dense haulm growth. Plants of Jade with systemic infection were rated according to the number of nodes affected. There was a small but significant increase in haulm and seed fresh weight in plants with up to two nodes affected. But plants with three to five nodes showed a progressive reduction in the yield of green seed (resulting from a reduction in the number of podding nodes) and in pod size and haulm fresh weight. Total losses in Jade during 1968 and 1969 with all grades of infection did not exceed 4 % of the green seed crop. Systemic infection in some plants resulted in the death of the apex and the production of healthy, normally podding tillers. Such plants had no commercial value due to delayed maturation. Pod infection in Jade occurred largely independently of systemic symptoms: the overall level during 1969 did not exceed 16 % and only 2 % were severely infected.

Total losses (from both systemic and pod infection) in Jade during 1968 and 1969 represented only a negligible part of the crop.
The effect of soil fumigation with D‐D on the yields of sugar beet and other crops
Authors: COOKE D. A. , HULL R.
Published: February 2008

An experiment in a field where sugar beet in 1965 had suffered from Docking disorder caused by Longidorus attenuatus tested the effect of fumigating the soil with 3741/ha D‐D and two amounts of nitrogen fertilizer on different crop sequences between 1966 and 1969. Although severe Docking disorder did not recur in sugar beet, fumigation increased yield in each of the three following years. Yield of barley was increased for 4 yr and of wheat, potatoes and ryegrass for 1 or 2 yr after treatment. All plant parasitic nematodes were controlled by the first fumigation and the numbers of those in unfumigated plots 3 yr after treatment. Fumigation also largely prevented infection of sugar beet by the fungus Helicobasidium purpureum.