bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of narcotic potency using houseflies
Authors: BRADBURY F. R. , O'CARROLL F. M.
Published: February 2008

A method is described for the measurement of narcotic potencies of chemical compounds, using houseflies. Narcotic potency measurements give rise to statistical problems which differ from those encountered in toxicity determinations in so far as the narcotic process is reversible, and successive values of the number of affected insects in a group subjected to the test do not normally increase monotonically and in some case considerable oscillation occurs. An earlier method (Bradbury & Armstrong, 1954) used probit analysis, but it is now shown that this treatment and also regression analysis both fail to provide a valid method of dealing with variability in this type of test. A test based on the response of two flies, one male and one female per flask, is now described. The test, based on sixteen flies per compound, gave figures for:

α0, the partial saturation of the test compound giving the same average knock‐down time as chloroform at a partial saturation of 0.005; α1, the partial saturation of the test compound giving knock‐down in I hr.;

b, the slope of the straight line relating log. knock‐down time to log. partial saturation;

s, the residual standard deviation of log. knock‐down time about its regression line on log. partial saturation.

From these values the 95% confidence limits for the slope and for the values of α0 were calculated. The test also provided information on the convulsive action of compounds and a modification of it was used to determine knock‐down times of very potent narcotics at high dosages. Results are presented for fifty‐seven halogenated hydrocarbons and the hypothesis that variations in potency between narcotics are determined mainly by rates of diffusion is examined. The results do not support this hypothesis. Narcotic and convulsant potencies measured by the method described are a useful guide to the behaviour of compounds in mouse tests.
Evaluation of the activity of a number of procaine derivatives and analogous compounds against powdery mildew (Sphaerotheca fuliginea) on cucumber*
Authors: NIEMANN G. J. , DEKKER J.
Published: February 2008

About fifty derivatives and analogues of procaine have been prepared and tested in three different tests for activity against powdery mildew of cucumber. Most of the compounds were active but few equalled procaine.

The results obtained seem to afford little evidence for simple structure‐activity relationship based on physico‐chemical or electro‐chemical properties.
Colonization of cellulose membranes by species of Verticillium
Authors: GRIFFITHS D. A. , ISAAC IVOR
Published: February 2008

Verticillium dahliae Kleb. (from Brussels sprouts), non‐pathogenic to tomato, and V. tricorpus Issac, a virulent pathogen to tomato, differed in their ability to colonize samples of commercial Cellophane, their rate of colonization being dependent upon external sources of carbohydrate. Cellophane and filter paper were both utilized in culture as the sole carbon source and it appears that both fungi have identical cellulase enzyme systems. Prolonged growth of the isolates is liquid medium containing sucrose as the carbon source resulted in lysis of the mycelium, which coincided with the production of polysaccharide material in culture.
The epidemiology of tomato mosaic: Sources of TMV in commercial tomato crops under glass
Authors: BROADBENT L. , FLETCHER J. T.
Published: February 2008

Of the several possible sources of tomato mosaic virus, seeds and root debris in the soil are considered to be of greatest importance. A survey of 374,000 seedlings on ten commercial holdings found 0.05% of them infected, and although these were removed virus had been spread to other young plants which did not show infection when transplanted into the growing houses, seven of twenty‐two of which contained a few infected plants when sampled shortly after planting. Virus overwintering on clothing, and debris on structures, are thought to be of minor importance, and smoking tobacco is seldom a source of infection for the tomato crop. A further survey of seventy‐eight samples from tomato crops in Britain confirmed the 1960‐61 survey: all were infected with tomato strains of TMV, none with tobacco strains, but one of the 187 infected seedlings referred to above was carrying a tobacco strain. Petunia was not as satisfactory as a special cultivar of White Burley tobacco for distinguishing between the tobacco and tomato TMV isolates.

Observations and tests on a commercial holding showed that TMV was readily carried from plants in infected glasshouses into clean ones by workers, and once introduced, spread rapidly within the crop.
Further studies on a British form of pea early‐browning virus
Authors: HARRISON B. D.
Published: February 2008

An isolate of pea early‐browning virus from Britain (PEBV (B)) has tubular particles most of which are either about 103 or 212 mμ long with sedimentation coefficients of 210 and 286 S respectively. Both types show cross‐banding at intervals of 2.5 mμ. Virus preparations containing only the shorter particles were not infective.

PEBV (B) was transmitted to pea seedlings by both adult and juvenile Trichodorus primitivus (de Man) (Nematoda) and persisted for 32 days in T. primitivus kept without plants. In two experiments T. primitivus failed to transmit a Dutch isolate (PEBV (D)), which is distantly related serologically to PEBV (B). PEBV (B) was transmitted by nematodes to cucumber roots more readily in soil at 20d̀ than at 24d̀ C., and more readily at 24d̀ than at 29d̀ C.

When transmitted by inoculation of sap, PEBV (B) and PEBV (D) caused similar symptoms in some pea varieties but differed in virulence towards others. Thirty‐one varieties resistant to natural infection with PEBV in The Netherlands were susceptible to PEBV (B) when manually inoculated with sap or when grown in naturally infested soil from one site; twenty‐six of these varieties did not become infected in soil from a second site, in which several other varieties that are susceptible in The Netherlands were infected. Varieties should therefore be tested for resistance by growing them on many infested fields. All but one of the pea varieties resistant to PEBV in The Netherlands became infected with the English form of tomato black ring virus when grown in soil containing infective Longidorus attenuatus Hooper.
Effects of barley yellow dwarf virus on the growth and yield of single plants and simulated swards of perennial rye‐grass
Authors: CATHERALL P. L.
Published: February 2008

Irish perennial rye‐grass plants infected with barley yellow dwarf virus (BYDV) showed inconspicuous leaf symptoms but were more stunted and yielded less total herbage, but more early spring herbage, than healthy plants. During a period of 2 years, infection did not decrease plant survival; infected plants produced more tillers and gave a higher ratio of vegetative to fertile tillers than healthy plants. BYDV caused a greater loss of yield in simulated rye‐grass swards cut twice a year than in those cut four times. Swards in which half the plants were infected gave yields intermediate between those of healthy and infected swards. Infected plants tended to dominate healthy ones in swards cut four times, but in those cut twice a year the initial status quo was maintained. In swards containing rye‐grass and white clover, the clover yielded more for most of the year when with BYDV‐infected than with healthy rye‐grass, but this trend was reversed in spring.

The different effects of barley yellow dwarf virus on rye‐grass plants and of cocksfoot streak virus on cocksfoot seem reflected by the different effects of the viruses on the competition between infected grass, healthy grass and white clover plants, when these are grown in different combinations.
The activation of diazinon by ganglia of the cockroach Periplaneta americana L. and its action on nerve conduction and cholinesterase activity
Authors: BURT P. E. , GREGORY G. E. , MOLLOY FRANCES M.
Published: February 2008

When sixth abdominal ganglia of the cockroach Periplaneta americana were irrigated continuously with diazinon solution in situ, its effects on nerve conduction and cholinesterase activity closely resembled those of diazoxon; spontaneous activity and after‐discharge increased until conduction was blocked, which happened while some cholinesterase was still uninhibited. The symptoms were only slightly relieved by irrigating ganglia with saline.

Though the LD50's of diazinon and diazoxon applied topically to adult male P. americana were similar (2.5 ± 0.33 and 4.5 ± 0.38 μig. per insect), diazoxon was about 300 times more active than diazinon against nerve function and cholinesterase activity in the sixth abdominal ganglion. This is probably because in the nerve preparations contact between the insecticide and the tissues surrounding the nerve cord, which in whole insects convert diazinon, a thionophosphate, into its phosphate analogue diazoxon, a more active anticholinesterase, was minimized. Indeed, taking into account the evidence of workers who previously compared in vitro the anticholinesterase activities of several thionophosphates with those of their phosphate analogues and found the phosphates much more active, the effect of diazinon on cholinesterase activity and nerve function in our experiments was unexpectedly great. By applying diazinon to nerve cords with SKF 525‐A, a compound likely to prevent oxidation of diazinon to diazoxon, an attempt was therefore made to decide whether diazinon directly affected nerve conduction or whether the effect resulted either from its conversion to diazoxon within the nerve tissue or from impurities in the diazinon used. Results were inconclusive, for SKF 525‐A (p‐diethylaminoethyl diphenylpropylacetate hydrochloride) not only failed to prevent the inhibition of cholinesterase, but interfered with the action of both diazinon and diazoxon on nerve conduction, and itself affected nerve conduction when applied alone. The possibility that diazinon is itself a mild anticholinesterase was not excluded.

SKF 525‐A applied to sixth abdominal ganglia at 2 × 10‐4M blocked conduction from cereal nerves to giant fibres in 50–97 min. and at 4 × 10‐5M decreased the post‐synaptic response; applied to giant fibres at 2 × 10‐4M it blocked conduction in 90–208 min. The effects of the larger concentration were not completely reversible. Although SKF 525‐A has been widely used to study the metabolism of drugs, its direct effects on conduction in nerve axons seem not to have been noted previously.
Seed‐transmission in the ecology of nematode‐borne viruses
Authors: MURANT A. F. , LISTER R. M.
Published: February 2008

Virus‐free populations of vector nematodes can acquire tomato black ring (TBRV), raspberry ringspot (RRV) and arabis mosaic (AMV) viruses from weed seedlings grown from virus‐carrying seed. When soils from fields where nematode‐borne viruses occurred naturally were air‐dried to kill vector nematodes and then moistened, TBRV and RRV occurred commonly in the weed seedlings that grew, but AMV occurred only rarely. Similar tests did not detect tobacco ringspot, grapevine fanleaf or tobacco rattle viruses in weed seeds in the single soil studied in each instance, although these three viruses are also seed‐borne in some of their hosts. Many weed species, when infected experimentally, readily transmit TBRV and RRV to their seed, but the viruses were much commoner in naturally occurring seed of some of these species than of others. These discrepancies between the frequency of seed‐transmission of viruses from experimentally infected plants and the extent of natural occurrence of infected seed seem largely to reflect the host preferences of the vectors.

Infective Longidorus elongatus kept in fallow soil retained TBRV and RRV only up to 9 weeks. When weed seeds in the soil were then allowed to germinate, the nematodes reacquired virus from the infected seedlings. Some weed species were better than others as sources of virus. Persistence of these viruses in fields through periods of fallow or fasting of the vector therefore depends on a continuing supply of infected seedlings produced by virus‐containing weed seeds. This is probably less true of viruses like AMV and grapevine fanleaf, which persist for 8 months or more in their vectors (Xiphinema spp.). A few seeds containing TBRV and RRV were found in soils free of vector nematodes, suggesting that the viruses are disseminated in weed seed. This probably explains how TBRV and RRV have reached a large proportion of L. elongatus populations in eastern Scotland.
Intra‐specific mechanisms in relation to the natural regulation of numbers of Aphis fabae Scop
Authors: WAY M. J. , BANKS C. J.
Published: February 2008

Parthenogenetic virginoparous apterae of Aphis fabae Scop. on field beans (Vicia faba) reproduced faster initially in populations of eight colonizing apterae than in those with 2–4 or 16–32 per plant. The aphids were at first mutually benefited but were quickly affected by competition as numbers rose above the critical density represented by about eight apterae and their first progeny. This is because the aphids remained densely aggregated and seemingly created a local shortage despite abundant food and space elsewhere on the plant. Such self‐induced competition provides the basis for self‐regulation of numbers of A. fabae in relation to (1) food and space provided by the growing plant and (2) mortality from natural enemies and from other causes including insecticides.

As competition increased, the multiplication of A. fabae populations slowed, newly formed adult apterae emigrated and increasing numbers of alatae were formed. The mean weights of apterae decreased from about 1·8 mg. to 0·3 mg. and of alatae from 0·9 to 0·2 mg. Such decrease probably favours production of many adults that might otherwise fail to mature.

Experiments in a glasshouse and in field cages indicated the success with which an A. fabae population adapts to and exploits a growing plant. Field bean plants sown in mid‐March and infested as in the field produced an average of 15,000–17,000 A. fabae emigrants per plant of which 78–84% were adults (mostly alatae). This is equivalent to about 1600 million alate emigrants from 1 acre (0·4 hectare) of an infested field bean crop.
Studies on the fungitoxicity of captan
Authors: RICHMOND D. V. , SOMERS E. , MILLINGTON P. F.
Published: February 2008

The cytological changes in Neurospora crassa conidia following treatment with captan at the ED 50 fungicidal dose have been examined by electron microscopy. With dormant conidia the only observable effect of captan was to produce a characteristic convoluted form of the nuclear membrane. It is suggested that this effect may be due to the reaction of captan with the sulphydryl groups of the nuclear proteins leading to an inhibition of cell division. The cytoplasmic membrane was unaffected by captan, confirming that this fungicide does not destroy cell permeability barriers.

After incubation in Fries medium, captan‐treated spores showed an almost complete loss of internal fine structure. Similar results were obtained with ‘protoplasts’ of N. crassa which showed disorganization of mitochondrial structure after captan treatment.
Glasshouse experiments on apple scab
Authors: MOORE M. H.
Published: February 2008

Experiments with fungicide mixtures used protectively and curatively against apple scab showed no advantage from adding phenylmercury chloride (PMC) to certain protective fungicides. Sulphur fungicides greatly impaired the curative activity of PMC, especially in mixtures applied 24 hr. after infection, but captan showed little and dodine acetate no such effect. PMC, however, contributed appreciably to the curative effectiveness of mixtures with captan or dodine acetate. Commercially prepared mixtures of dispersible sulphur with phenylmercury dimethyldithiocarbamate and of zineb with mancozeb gave promising results, and an experimental mixture of dodine/glyodin acetates at low rates was effective protectively and especially curatively.

Dodine acetate, dichlofluanid, lime‐sulphur, and isobutyl‐o‐coumarate showed little translocated activity against scab when applied after infection, and PMC, which earlier showed strong translocated activity when applied in summer before infection, was much less effective when applied in spring 24 hr. after infection.

Uncontrolled powdery mildew early in the scab‐incubation period greatly reduced the establishment of scab infection on the test plants (clonal root‐stocks); methods of mildew control in such experiments are suggested.
Verticillium wilt of the hop: field studies on wilt in a resistant cultivar in relation to nitrogen fertilizer applications
Authors: SEWELL G. W. F. , WILSON J. F.
Published: February 2008

In two large‐scale observation trials on commercial farms inorganic nitrogen fertilizer was applied at 70 lb. N/acre (N1), 1401b. N/acre (N2) and at a normal commercial rate of 210 lb. N/acre (N3). Mean wilt incidence was 60 and 25% less with Ni and N2 respectively than with N3 during 5 years at one site and 3 years at the other. During these periods wilt declined progressively and this was tentatively attributed to the reduced intensity of host colonization, and to progressive declines in soil infectivity resulting from effects on the quantity, quality and longevity of annually produced inoculum.

Marked annual fluctuations of wilt incidence and yields occurred at one site and these were associated with weather in the spring and early summer: wilt incidence was inversely related to soil temperature, and yield was directly related to rainfall. Yields were not diminished by the low‐N treatments, but clear correlations between yields and wilt incidence were probably obscured by the differential effects of weather conditions at the three levels of N application.

The results emphasized the importance of reducing traditionally high N applications and, on farms where fluctuating wilt is severe, of applying the minimum levels of N commensurate with the maintenance of satisfactory yields.
Studies on pollination and fertilization in the field bean (Vicia faba L.)
Authors: HANNA A. S. , LAWES D. A.
Published: February 2008

The percentage of cross‐fertilization in the field bean was found to be around 45%, and to be higher on the lower nodes of the plants than on the upper. No differences in the relative pollen tube growth rates of self and foreign pollen were observed.

The different lines and genotypes investigated responded differently to open pollination, selfing with manual tripping, and selfing without tripping.

Fertilizer application and date of sowing affected the number of flowers produced and the number of seeds set, but did not affect the ratio of seeds to flowers, i.e. the index of self fertility.
Effects of shading on inflorescence size and development in temperate perennial grasses
Authors: RYLE G. J. A.
Published: February 2008

Single plants of S24 perennial ryegrass (Lolium perenne L.) and S215 meadow fescue (Festuca pratensis Huds.) were transferred between, or exposed continuously to, contrasting light intensities obtained by decreasing the natural light in a glasshouse with Tygan shades. Inflorescence development in main shoots was studied by dissections of shoot apices, and by counts of branches and florets when ears emerged. Apical growth was slower, and spikelet initiation and inflorescence development were delayed or inhibited, in decreased light intensities. The number of main branches in the ear depended on the rate of apical growth before and after spikelet initiation, and on the time of spikelet initiation. In meadow fescue these processes were influenced by light intensity. Floret numbers per inflorescence branch were generally decreased by decreased light intensity. Most of the effects of light intensity on inflorescence development were smaller in ryegrass than in meadow fescue.
Insecticidal control of cabbage root fly (Erioischia brassicae (Bouché)) in the axillary buds of Brussels sprouts
Authors: COAKER T. H.
Published: February 2008

The occurrence of dipterous larvae in the axillary buds (buttons) of Brussels sprouts was investigated at Wellesbourne in 1963–66. The most severe infestations occurred on early crops harvested in August, in which up to 10% of the buttons were damaged by cabbage root fly larvae. Most of the damaged buttons were on the lower part of the stem and were present on only a small proportion of the plants. Laboratory and field tests of insecticides showed that trichlorphon gave up to 88 % control. The principles involved in an insecticidal control method are discussed.
Laboratory and field tests of zineb and other fungicides against downy mildew of lettuce (Bremia lactucae Regel)
Authors: CHANNON A. G. , WEBB M. J. W.
Published: February 2008

In laboratory tests on young lettuce plants, the protection provided by sprays of zineb wettable powder against artificial inoculations with Bremia lactucae was less than that obtained with tank‐mix zineb, and with several other dithiocarbamates and related fungicides.

Experiments on autumn lettuce in the field also showed that tank‐mix zineb was more effective than the wettable powder. On winter lettuce in frames, however, zineb wettable powder gave control similar to or better than that given by any of the other materials tested.

Infection in most of these outdoor experiments was not heavy. None of the fungicides gave very high control or markedly increased the number of hearted or marketable plants.

When zineb wettable powder was sprayed on autumn lettuce at the rate of 2 lb./acre it gave similar disease reductions whether applied in low, medium or high volumes of water.
The effect of a post‐harvest heat‐treatment on the storage behaviour of Cox's Orange Pippin apple fruits
Authors: SHARPLES R. O.
Published: February 2008

Samples from a wide range of commercially grown Cox's Orange Pippin apple fruits were immersed in water at 45° C. for 10 min. to control rotting due to Gloeosporium spp. In two seasons the incidence of rotting following storage for 19 weeks at 3·3° C. (38° F.) was reduced to about 40% of the level in the untreated samples. However, there was a marked increase in the incidence of breakdown and core flush in the treated fruit, particularly when stored in a controlled atmosphere of 5% CO2, 3 % O2. A similar but less severe increase in the incidence of breakdown was also recorded in the second season in treated fruit stored in 2% O2 (with continuous removal of CO2). The treated fruit tended to develop a more yellow ground colour and softened more rapidly during storage in 5% CO2, 3% O2. It is concluded that the treatment advances fruit senescence and that the increased incidence of physiological disorders is likely to limit the use of this method for the control of Gloeosporium rotting in English‐grown Cox apples.
Strains of Prunus necrotic ringspot virus in hop (Humulus lupulus L.)
Authors: BOCK K. R.
Published: February 2008

Purified preparations of Prunus necrotic ringspot virus (NRSV) from hop plants formed two light‐scattering zones when centrifuged in sucrose density gradients; the upper and lower zones contained particles 25 mμ and 31 mμ in diameter respectively whose sedimentation coefficients were 79 S and 107 S.

NSRV isolates from hop were of two distinct serological types: ‘A’ strains, serologically very closely related to NRSV isolates from apple; and ‘C’ strains more nearly related to NRSV from cherry.

The variety Fuggle is tolerant to hop mosaic (not related to NRSV) and different selections of apparently healthy female plants usually contained A strains; but C strains were usually isolated from nettlehead‐diseased plants. Either A or C strains occurred in male plants grown with the hop‐mosaic tolerant varieties. In mosaic‐sensitive varieties (Goldings and Bramlings) apparently healthy female plants tested were usually infected with C strains; either A or C types occurred in mosaic‐sensitive male plants. NRSV was not detected in the seventy‐four hop seedlings obtained from virus‐infected plants.

Some varieties developed nettlehead when infected with NRSV (A) or (C) + the hop form of arabis mosaic virus, but not with NRSV (A) or (C) alone. Others developed nettlehead when infected with arabis mosaic virus + NRSV (C) but not with arabis mosaic + NRSV (A).

A and C strains can multiply together in the same hop plant. There is evidence of partial antagonism, however, and the fluctuating behaviour of the nettlehead syndrome probably reflects changes in the relative concentration of the two serotypes.
Rates of decay in wood measured by carbon dioxide production
Authors: GOOD H. M. , DARRAH JOSEPHINE A.
Published: February 2008

The applicability of two methods of respirometry to measurement of the carbon dioxide output of naturally decaying branches and wood of standing trees was studied. The Warburg respirometer was judged unsuitable for general use on decaying wood. A conductivity respirometer was found satisfactory.

Carbon dioxide production was essentially unaffected by fragmentation suggesting that the measurements obtained are likely to be a valuable indication of decay in the intact tree or branch. The carbon dioxide production of samples was fairly stable when conditions were kept constant but responded promptly to increased or decreased moisture. Wood from branches infested with Polyporus tulipiferae in which moisture was increased from approximately 20%–50% (fresh weight basis) increased its carbon dioxide output over a 4‐day period by some seven times. Comparable wood in which the moisture content was reduced from 45 to 20 % showed an almost linear reduction in rate over a similar period to about one‐sixth the original rate.

Rate of decay in stained and unstained zones of living trees showed no consistent effect of the stain. However, rates of decay in heart‐rot of poplar caused by Fomes igniarius were only one‐third those reported by Verrall (1937) for decay in culture.
Carbon dioxide evolution as a measure of attack of wood by fungi and its application to testing wood preservatives and sap stain preventives
Authors: SMITH R. S.
Published: February 2008

A method of assessing fungal attack on wood, using a conductivity respirometer to measure the CO2 evolution of the attacking fungus, is described and its application to the testing of wood preservatives and sapstain preventives is explored.

Tests made by this method established in 9–13 days that the minimum fungitoxic concentration of Timbor (disodium octaborate decahydrate) was between 0·05 and 0·1%—a value agreeing with that given by the standard wood‐block test lasting 12 weeks.

The use of the CO2‐measurement method for fungitoxicity determinations on a copper‐chrome‐arsenate wood preservative and on the sapstain preventive, Santobrite (a sodium pentachlorophenate preparation), gave unsatisfactory results.
Studies on the transmission of groundnut rosette virus by Aphis craccivora Koch
Authors: WATSON MARION A. , OKUSANYA BOLAJOKO A. M.
Published: February 2008

Four strains of groundnut rosette virus were transmitted by a race of Aphis craccivora (Koch) from groundnut in Nigeria. Two of these strains, both from East Africa, were transmitted only by A. craccivora from Kenya. A fifth isolate, from Nigeria, was not transmissible by either race. The two races of aphids have been shown elsewhere to be distinct biotypes.

Most A. craccivora needed longer than 24 h feeding on infected groundnuts to acquire virus, and many needed 2–3 days of feeding on healthy plants to cause infection, even after several days on infected plants. The delays partly reflect the slow uptake of virus and possibly a period needed for virus multiplication in aphid tissue but some is lost through resistance of the test plants to infection.

In consecutive feeding experiments Natal Common variety could be infected soon after aphids had left the source of virus, but a more resistant Nigerian variety sometimes needed several more days. The frequency of inoculation by aphids, or the concentration of virus in the inocula or both, increased with time, but the times at which aphids were able to infect plants was also dependent on variety.
The use of steam/air mixtures for partially sterilizing soils infested with cucumber root rot pathogens
Authors: DAWSON J. R. , KILBY A. A. T. , EBBEN MARION H. , LAST F. T.
Published: February 2008

An apparatus for experimentally heating glasshouse soils in situ with steam/ air mixtures is described. Covering soil with a rigid hood enabled mixtures to be introduced at ground level at pressures sufficient to give reasonable rates of heat penetration.

Heat‐treating soils (66–100° C), in which cucumbers had previously grown poorly, increased yields of subsequent crops from (1) 33 to 39/43 kg/plot of four plants and (2) 95 to 178/191 kg/plot. These increases were associated with the eradication of a dark sclerotial pathogenic fungus causing tap root rot.

Increasing partial sterilization temperatures increased concentrations of soluble and exchangeable soil Mn from 4 p.p.m. in unheated soil to 9, 43, 87 and 108 p.p.m. at 66, 77, 88 and 100° C respectively, these differences being paralleled by concentrations of Mn in leaf laminae. Cucumbers grown in soils sterilized at 88° C yielded 8 % more than those in soils treated at 100° C.
The effects of length of the growth period and of nutrition upon potato‐tuber susceptibility to dry rot (Fusarium caeruleum)
Authors: BOYD A. E. W.
Published: February 2008

Standardized inoculations of the potato varieties Catriona and Doon Star over 6 years have shown that shortening the growth period, either by deferring planting or by removing the haulm prematurely, may considerably reduce susceptibility of the tubers to dry rot (Fusarium caeruleum). Although these treatments reduce dry‐matter content of the tubers, no direct relationship between this factor and susceptibility was established.

High pre‐maturity susceptibility was confirmed at the time of flowering; as the haulm matured susceptibility decreased: when the haulm was dead tubers were resistant. Within a fortnight after any time of premature haulm removal, tubers became completely resistant and showed a decrease in sucrose content but not in content of reducing sugars. It is suggested that susceptibility in the immature tuber is closely related to the content of sucrose, which accumulates because of rapid translocation from the vigorously growing haulm.

After harvest, tuber susceptibility slowly increased during storage, with an increase mainly in reducing sugars, but these two factors were not directly related.

An application of 6 cwt/acre (753 kg/ha) of 12:12:18 NPK fertilizer to Catriona significantly reduced liability to infection. Additional nitrogen (6 cwt/acre ammonium sulphate) raised tuber susceptibility to that in a non‐fertilized plot: when sulphate of ammonia was the only treatment given, the tubers were significantly more susceptible than those receiving complete fertilizer.
Vapour action of fungicides against powdery mildews
Authors: BENT K. J.
Published: February 2008

Certain fungicides prevented the growth of powdery mildews at distances extending several millimetres beyond the edge of localized deposits on leaves. Most of the materials also acted at a distance when separated from the leaf by glass cover‐slips, indicating that the effect was due to the emission of vapour. In addition to sulphur and lime‐sulphur, whose vapour action is already known, fungicides based on drazoxolon, oxythioquinox, binap‐acryl, dinitro‐octyl phenyl crotonates and a phthalimido‐phosphonothionate were found to act in this way. Two systemic fungicides, griseofulvin and triamiphos, did not give a detectable vapour action. Tests were conducted mostly on open glasshouse benches. A draught from a fan shifted the zones of inhibition to one side of the deposits, but did not reduce their areas. Vapour effects were similar in extent on plants maintained at 18–25° C and at 27–32° C. Variation in the areas protected was studied in relation to the size and fungicide content of the deposits, to different powdery mildews, to time of incubation and to different types of formulation. Deposits applied to leaves by high‐ or low‐volume sprays at concentrations used in the field gave significant protection at a distance.

Vapour effects were demonstrated also on mildew conidia incubated on glass slides bearing a spot of fungicide, and on infected plants placed in beakers coated on the bottom with fungicide.

Movement of fungicides in the gaseous state is discussed in relation to the control of foliage diseases in the field.
Some observations on the economic importance of sugar‐beet downy mildew in England
Authors: BYFORD W. J. , HULL R.
Published: February 2008

Sugar‐beet downy mildew is most prevalent in England in the sugar‐beet and mangold seed‐growing area of South Lincolnshire and West Norfolk. The most widespread and severe recent outbreaks were in 1957, and in 1965 when 6412 acres were reported with more than 10% infected plants. The fungus usually overwinters in sugar‐beet and mangold seed crops, and in England other ways of overwintering are seldom important. Steckling beds are infected in the autumn, and the disease may increase rapidly in the seed crop in early spring. Summer‐sown stecklings get more downy mildew than stecklings sown in spring under a cereal cover crop, and direct‐drilled seed crops get more downy mildew than transplanted crops.
Resistance in maize to a third East African race of Puccinia polysora Underw
Authors: STOREY H. H. , HOWLAND AUDRIE K.
Published: February 2008

In 1961 a third race, EA. 3, of Puccinia polysora was recognized in Kenya. This was virulent to maize carrying either of the genes Rpp1 or Rpp2, previously isolated. Resistance to EA. 3 was found in many Central American maizes; in two, Andaqui (Colombia) and Zapalote Chico (Mexico), genes Rpp10 and Rpp11 were recognized. Rpp10 was fully dominant and its genotypes highly resistant to both EA. 1 and EA. 3. Rpp11 was incompletely dominant, but determined effective resistance to both races when homozygous.

Experimental crosses gave no evidence of linkage between the genes Rpp1, Rpp10 and Rpp11.
Studies on plant growth‐regulating substances XXIV. Factors influencing kinetin‐induced phosphorus mobilization in detached radish cotyledonary leaves
Authors: ATKIN R. K. , WAIN R. L.
Published: February 2008

Kinetin treatment of localized areas of detached radish cotyledonary leaves was shown: (a) to defer the dry weight and chlorophyll declines that usually occur after leaf detachment; and (b) to promote the re‐distribution of phosphorus towards treated regions. These responses, which were most pronounced in leaves taken from 12‐day‐old plants, were much reduced in the light and were not found under anaerobic conditions. Kinetin‐induced responses were also inhibited in leaves pretreated with actinomycin D and ribonuclease.
Effects of growth regulators, CCC and B9, on some potato varieties
Authors: HUMPHRIES E. C. , DYSON P. W.
Published: February 2008

The effects of CCC and B 9 on the growth habit of potato differed between varieties. CCC diminished stem lengths and dry weight more than Bo because CCC was applied early when shoots emerged from the soil, but B 9 was applied about 3 weeks later when several leaves had formed.

In some varieties lateral stem growth was increased by treatment and in others decreased. There was an inverse relation between main stem and lateral stem growth so that varieties with vigorous main stem growth had poor lateral growth and vice‐versa. Treatment with the growth‐regulators diminished leaf dry weight of main stem leaves less than leaf area, but the degree of magnitudes of the changes depended on the variety. Both regulators lessened net assimilation rate. Net assimilation rate and dry matter per unit area of leaf were inversely related, possibly because accumulation of substances in leaves decreases photosynthesis.

Stolon dry weight was positively correlated with main stem leaf area. There was a direct relation between stem length and tuber dry weight, suggesting that tuber initiation occurs at different stem lengths in different varieties. Tubering was earliest in Epicure and latest in King Edward. Epicure had the greatest tuber weight and smallest stem length.
Effects of changes in environmental schedules on the penetration of leaves and epidermal strips of wheat seedlings by Puccinia graminis tritici
Authors: SHIPTON W. A. , BROWN J. F. , WHITE N. H.
Published: February 2008

The frequency with which intact leaves and epidermal leaf strips of wheat seedlings were penetrated by Puccinia graminis tritici, strain 21 Anz 2, was observed following exposure of inoculated material to various regimes of illumination/darkness and temperature.

Epidermal strips, at 24°C, were penetrated most frequently when continuous light (540 ft‐c) was commenced at either 4 or 8,20 or 24, or 36 or 40 h after inoculation or when a 4 h period of light was applied at these times. With both treatments, the curve obtained when the length of the dark period preceding illumination was plotted against the frequency of penetration showed a series of alternate peaks and troughs and the periodicity of the curves was significant at the 1 % probability level. In the former curve the best form of regression was linear modified by a cosine function, while in the latter the linear term proved to be non‐significant. When dark periods of different lengths were applied, penetration was more variable on intact leaves than on epidermal strips. Penetration of intact leaves was influenced by the light intensity to which the seedlings were exposed after the dark treatment.

The time of day when intact leaves were inoculated influenced penetration when they were grown under controlled conditions. Greatest penetration of the variety Little Club occurred when leaves were inoculated at 1.30 a.m. The time of day when epidermal strips were inoculated did not influence penetration.

The inhibitory effect of continuous light on penetration of epidermal strips was overcome by changing the temperature from 18·5 to 24°C. Greatest penetration was obtained when the change was made 24 or 28 h after inoculation.
On cyst colour changes, bionomics and distribution of potato cyst‐eelworm (Heterodera rostochiensis Woll.) pathotypes in the East Midlands
Authors: GUILE C. T.
Published: February 2008

Pot tests and field trials in 1966 confirmed earlier observations that pathotype A potato cyst‐eelworm (Heterodera rostochiensis Woll.) showed marked colour differences from pathotypes B and C during development on the roots of susceptible potatoes. In hatching tests started in July, newly formed brown cysts of pathotype A released four times as many larvae as those of pathotypes B and C, without entering an immediate diapause; the latter produced larvae after a rest period of 18–21 days. Subsequent second‐generation cyst production in glass‐tube culture was greater from pathotype A. Field observations suggested that all pathotypes mature at about the same time and give rise to only one flush of cysts on both early and maincrop potatoes in the growing season.

Cyst colour surveys in commercial crops, and pot and field trials using resistant potato selections, confirmed that pathotypes B and C are both dominant and widespread in the East Midlands.
The effect of resistant solanaceous plants on the sex ratio of Heterodera rostochiensis and the use of the sex ratio to assess the frequency and genetic constitution of pathotypes
Authors: TRUDGILL D. L. , WEBSTER J. M. , PARROTT D. M.
Published: February 2008

The sex ratios of two Heterodera rostochiensis populations were compared on fifteen solanaceous plants. Larvae did not mature in the roots of Atropa belladona, Datura stramonium or Nicotiana tabacum but adults were produced on the other plants, on some only males and on others, males and females. With two other populations, but not with a third, the percentage of larvae that became female on a potato hybrid with a dominant gene for resistance derived from Solanum tuberosum ssp. andigena increased during successive generations on the hybrid in accordance with the hypothesis that such larvae are double recessives (aa). Fewer larvae became adult in plants with two dominant genes for resistance than in plants with one, and such plants probably exerted selection of both males and females. A population from St Brelades (Jersey) produced fewer females and more males on the susceptible variety Arran Banner than did either the Thorney (Cambs.) or Aberystwyth populations. A much greater percentage of larvae from the St Brelades population became female on an ex andigena hybrid derived from CPC 1690 than on one derived from CPC 1685.
Extraction of Xiphinema and Longidorus species from soil by a modification of Cobb's decanting and sieving technique*
Authors: FLEGG J. J. M.
Published: February 2008

A modification of Cobb's decanting and sieving technique is described which was found to combine speed of operation with efficiency when extracting Xiphinema and Longidorus species from a variety of soils. Standard times were set for sedimentation and the nematodes were collected on a bank of sieves each of 150 μ aperture (rather than of a range of apertures) before final separation from inert debris on a Baermann funnel.

Preliminary tests showed that both time and temperature could have considerable effect on yield during the final separation stage. X. diversicaudaturn and X. vuittenezi showed different temperature optima at which the yield was up to twice that at other temperatures. Yields increased markedly with time over the first 20 h, but much less thereafter.
Morphology of the male reproductive system and spermatophore of the red bollworm, Diparopsis castanea (Hmps.) and the possible effect of the chemosterilant tepa on the gross structure
Authors: OUTRAM I. , CAMPION D. G.
Published: February 2008

The structure of the male reproductive system of the red bollworm, Diparopsis castanea (Hmps.), is described: it is typical for a Noctuid.

After day‐old male moths had been injected with dosages of the chemosterilant tepa ranging from 10 to 50 μg, no impairment of the gross function of their accessory gland apparatus resulted, and spermatophores of normal size were transmitted during copulation. Microscopic examination of testicular preparations demonstrated no gross damage following treatment, and the sperm was motile. The injected males were nevertheless completely sterile.
Effects of Aphis fabae Scop, and of its attendant ants and insect predators on yields of field beans (Vicia faba L.)
Authors: BANKS C. J. , MACAULAY E. D. M.
Published: February 2008

Predators (mainly coccinellid adults and larvae and syrphid larvae), although few, were important in decreasing numbers of Aphis fabae on a small plot of field beans during the early stages of infestation in a year favourable to the aphid. At the same time, ants (Lasius niger L.), attending aphids on other plants on the same plot, effectively protected the aphids from predators for about 2 weeks, enabling the attended aphids to multiply faster than the unattended. When all aphid populations started to decline, predators became more numerous and accelerated the decline on both sets of plants.

Bean plants without aphids yielded fifty‐six seeds per plant; those with aphids but free from ants gave seventeen; and those with ant‐attended aphids, eight seeds per plant. The damage and loss of yield was caused by the large aphid populations that developed when the pods were maturing, and not by the fewer aphids present when the plants were in flower. It appears that small, temporary infestations during flowering might increase the yield of field beans.
The horizontal and vertical distribution of flying insects near artificial windbreaks
Authors: LEWIS T.
Published: February 2008

Lath fences 3 ft and 8 ft high affected the horizontal distribution of flying insects similarly: most insects accumulated at a distance equal to 2–3 times the height of each fence to leeward, where catches, measured at 14 and 38 in. (≡ to 0·4 times the height of the fence above the ground) were 30–40 % greater than in exposed positions. Behind an 8 ft fence accumulations extended vertically to 12–16 ft (≡ to 1·5‐2·0 times the height of the fence). Vertical profiles of weak‐flying insects, in winds > 3 m.p.h. differed in sheltered and exposed positions; in shelter the boundary layer was deeper and insects were more abundant nearer the ground than elsewhere. For strong flyers, and insects which flew only in winds < 2 m.p.h., vertical profiles in sheltered and exposed positions were indistinguishable.
Darkness and the activity of diquat and paraquat on tomato, broad bean and sugar beet
Authors: BRIAN R. C.
Published: February 2008

A period of darkness after treatment increased the activity of diquat and paraquat on tomato, broad bean and sugar beet. The extent of the increase was dependent on the time of day (and year) of treatment, on the light quality and intensity before spraying and on the duration of the darkness. Damage from morning treatments, unlike those in the afternoon, increased rhythmically with increasing darkness. The rhythm showed a maximum about every 24 hr and continued through several days of darkness.

The results underline not only the complexity of diquat and paraquat action but also the importance of strictly controlling experimental procedure when studying their mode of action.
Antifungal phenolic acids in apple fruits after infection with Sclerotinia fructigena
Authors: FAWCETT C. H. , SPENCER D. M.
Published: February 2008

Several compounds were separated from the antifungal materials produced in Edward VII apple fruits attacked by the brown rot organism Sclerotinia fructigena. Six phenolic compounds were isolated in the crude state by column chromatography and their fungicidal properties examined. Two of the phenolic acids present were purified and identified as 4‐hydroxybenzoic acid and 4‐hydroxy‐3‐methoxybenzoic acid. These phenolic compounds were shown to arise from the action of the pathogen on the juice of the fruit and not from the peel or the juice‐free pulp.
Competitive saprophytic colonization of wheat straw
Authors: BURGESS L. W. , GRIFFIN D. M.
Published: February 2008

Using the ‘Cambridge method’, the effect of temperature on the colonization of wheat straw by Fusarium culmorum, Gibberella zeae, Cochliobolus sativus and C. spicifer was studied. Within the range 10–30 °C, saprophytic colonization by the four fungi was favoured by lower temperatures. This could not be attributed to the effect of temperature on the growth of the fungi in pure culture, but was probably caused by increased antagonism at higher temperatures from the general soil microflora. Contrary to previous indications, C. sativus strongly colonized straw under suitable environmental conditions.