bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage to oilseed rape seedlings by the field slug Deroceras reticulatum in relation to glucosinolate concentration
Authors: GLEN D. M. , JONES H. , FIELDSEND J. K.
Published: February 2008

Seedlings of nine commercial cultivars of oilseed rape were exposed to the field slug Deroceras reticulatum immediately after sowing in compost in trays. There was a small reduction in seedling numbers in the presence of slugs which was not related to glucosinolate concentration in seeds or seedlings. However, the number and leaf‐area of seedlings with damage symptoms were strongly and inversely related to the total concentration of glucosinolates in seeds and one wk‐old seedlings. The presence of barley seedlings as alternative food did not significantly affect this relationship. The glucosinolate concentration of seeds was closely correlated with that of wk‐old seedlings. Analysis of individual glucosinolates in four cultivars spanning the range of concentrations found, showed that the concentration of most components declined as total glucosinolate concentration decreased. However, 2‐phenyl ethyl‐glucosinolate (gluconasturtiin) concentration tended to increase in seeds and 3‐indolyl methyl‐glucosinolate (glucobrassicin) increased in seedlings as total glucosinolate concentration decreased. Damage by slugs was inversely related to the concentration of those glucosinolates which decreased and was positively correlated with the two compounds which increased as total glucosinolate concentration decreased. The results support the hypothesis that glucosinolates in brassicas protect them from polyphagous herbivores, and, in particular, that an important function of glucosinolates in rape seeds is to protect seedlings from slugs. As glucosinolate concentrations of oilseed rape cultivars continue to decline, so the risk of slug damage to seedlings may well increase.
Resistance in groundnut (Arachis hypogaea L.) to Aphis craccivora (Koch).
Authors: PADGHAM D. E. , KIMMINS F. M. , RAO G. V. RANGA
Published: February 2008

The behaviour, development and reproductive capacity of Aphis craccivora, vector of a number of groundnut viruses, are compared on a range of susceptible and resistant genotypes. Field trials demonstrated no significant difference between genotypes in the rate of arrival of alates, but population development was slower, and subsequent population decline faster, on the genotype EC 36892 (ICG 5240). Behavioural studies in the screenhouse, likewise showed no inhibition to alighting onto EC 36892 though choice tests demonstrated a significant redistribution of the population in favour of the susceptible genotype TMV 2 (ICG 221) over the following 10 h. In clip cage experiments, development was faster and nymphal numbers were higher on the genotype TMV 2 compared to EC 36892.
Induction of edible sclerotia of Pleurotus tuber‐regium (FR) Sing, in the laboratory
Authors: OKHUOYA J. A. , OKOGBO F. O.
Published: February 2008

In the field, sclerotia of Pleurotus tuber‐regium were found in dead trees and fallen logs of Daniella oliveri. Sclerotia of P. tuber‐regium were produced in the laboratory when the fungus was cultured in moist drill dusts of D oliveri and Elaeis guineensis. The resulting sclerotia were viable and had features similar to those found in the natural habitat.
Mycological studies on the equine intestinal tract with particular reference to equine dysautonomia (grass sickness)
Authors: DOXEY D. L. , ROBB JEAN , MILNE E. M. , GILMOUR J. S.
Published: February 2008

A wide variety of non‐endophytic fungi was isolated from the stomach, colon and rectum of healthy horses, horses suffering from equine dysautonomia and horses suffering from other disorders clinically resembling dysautonomia. Of the isolates with toxin‐producing potential, species of Aspergillus and Penicillium predominated. Absidia spp. occurred in virtually all horses and Rhizopus was very common, but neither is known to produce toxins. The survey did not associate any particular fungal species with equine dysautonomia.
Some effects of hop latent viroid on two cultivars of hop (Humulus lupulus) in the UK
Authors: BARBARA D. J. , MORTON A. , ADAMS A. N. , P.GREEN C.
Published: February 2008

Some effects of infection by hop latent viroid (HLVd) on two commercial plantings of hop, one each of two high alpha‐acid cultivars, are described. The cultivar Omega was severely affected: yield of cones and individual cone weights from infected plants were both lower than from uninfected plants by c. 35% and the alpha‐acids content (as assessed by HPLC) of the cones c. 30% lower. Wye Northdown was less severely affected: cone weight was 8% less (though this was not statistically significant) and alpha‐acids content lower by c. 15%. In both cultivars beta‐acids were higher in infected plants which, together with differences in other chemical components, suggested that cones on infected plants had matured, or were maturing, earlier than those on uninfected plants.

These effects, together with the previous finding that HLVd occurs frequently in some cultivars (Barbara, Morton & Adams, 1990), suggest that HLVd is a potentially important constraint on hop production in the UK and should be eliminated if possible.
Variations in the “cross protection” effect between two strains of citrus exocortis viroid
Authors: DURAN‐VILA N. , SEMANCIK J. S.
Published: February 2008

In a survey conducted to evaluate the biological properties of several field sources that induced a severe exocortis reaction on citron (Citrus medica L.), a viroid isolate which induced mild symptoms on Gynura aurantiaca was detected. This isolate was characterised as a strain of the citrus exocortis viroid (CEV) by size and homology, and was designated as CEV‐129. Cross protection assays using CEV‐129 as a “protecting” strain against the severe type strain of CEV demonstrated that a mild strain of CEV could provide apparent ‘protection’ against challenge inoculations with the severe strain. The protection effect, however, displayed a variability which ranged from only a brief delay to almost total impairment of symptom expression. The level of protection was dependent upon the length of the interval between the inoculations with the mild and the severe strains. In all cases the effect was temporary since the symptoms and viroid concentration which ultimately prevailed reflected the predominance of the severe strain in the mixed infection. The interpretation of these results and their relationship with previous reports of ‘cross protection’ reactions are discussed along with the consideration of the efficacy and limitations of this term with viroid infection.
The nature of the resistance in groundnut to rosette disease
Authors: BOCK K. R. , MURANT A. F. , RAJESHWARI R.
Published: February 2008

Groundnut rosette disease is caused by a complex of three agents, groundnut rosette virus (GRV) and its satellite RNA, and groundnut rosette assistor virus (GRAV); the satellite RNA is mainly responsible for the disease symptoms. Groundnut genotypes possessing resistance to rosette disease were shown to be highly resistant (though not immune) to GRV and therefore to its satellite RNA, but were fully susceptible to GRAV.
The identification and fitness of virulent potato cystnematode populations (Globodera pallida) selected on resistant Solarium vernei hybrids for up to eleven generations
Authors: TURNER SUSAN J.
Published: February 2008

Selection of Globodera pallida populations on resistant Solanum vernei‐hybrids resulted in distinct virulent strains after eleven generations.

Some of these virulent populations were assessed on their environmental fitness under field‐type conditions. All reproduced less well in unsterilised soil, but virulent populations were less affected by environmental variation than their avirulent counterparts. Evaluation of their reproductive ability could not equate virulence to overall enhanced or reduced genotypic fitness compared with their avirulent counterparts.

These populations were shown to be genetically distinct from their unselected counterparts using isoelectric focusing and specific enzyme staining. The control and management of virulent G. pallida populations is discussed.
Seed vigour and water relations in wheat
Authors: NAYLOR ROBERT E. L. , GURMU MULUGETA
Published: February 2008

The laboratory germination (criterion radicle emergence) of seven seed lots of winter wheat cv. Slejpner was similar. However, they differed in vigour as demonstrated by differences in germination after controlled deterioration carried out at a range of seed moisture contents, at two temperatures and for different times. A vigour assessment for each lot was quantified by calculating a value for the seed lot constant Ki, of the viability equation.

Germination in lower water potentials reduced the uptake of water, radicle and coleoptile emergence and radicle and coleoptile extension. There was no difference in the water uptake of seed lots differing in vigour. However, seed lots of lower vigour showed less radicle emergence, less coleoptile emergence and shorter radicles than higher vigour seed lots in low water potentials. Similarly, controlled deterioration resulted in reduced radicle and coleoptile emergence and growth compared to unaged seed, and also to a greater sensitivity to low water potentials.

The implications for field establishment are discussed.
Evaluation of defined‐area trapping for estimating the density of the field slug Deroceras reticulatum (Müller)
Authors: FERGUSON C. M. , HANKS C. B.
Published: February 2008

A novel quantitative method (defined‐area trapping) devised in New Zealand for sampling slugs was tested in pastures in the UK and compared with cold water extraction processes and surface searching. Despite the different soils and conditions compared with New Zealand, the technique gave results for the UK comparable with accepted methods of estimating slug density with savings in time and labour and provided a non‐destructive means of sampling for slugs.
The effects of sowing date and planting method on stem borer damage in dauro millet
Authors: AJAYI OLUPOMI , LABE D. A.
Published: February 2008

In field trials conducted at Samaru, Nigeria in 1983, 1984 and 1985, damage to dauro millet by the millet stem borer, Coniesta ignefusalis Hampson (Lepidoptera: Pyralidae), varied between years and dates of planting. The crop was almost completely destroyed by the stem borer during 1984. Based on 1983 and 1985 data, the period between 10 July and 2 August appears to be best for planting dauro millet at Samaru for least stem borer damage while planting between 11 and 30 July appears to be optimum for grain yields.

The direct sown crop suffered more damage than the transplanted crops in all years but only in 1985 was the difference significant. There was no significant difference between slant and upright transplanting in terms of stem borer damage and grain yield. It is concluded, therefore, that the choice of planting method would depend on its convenience to the farmer.
Phytophthora cryptogea root rot of tomato in rock woo] nutrient culture. II. Effect of root zone temperature on infection, sporulation and symptom development
Authors: KENNEDY R. , PEGG G. F.
Published: February 2008

The effect of root‐zone temperature on Phytophthora cryptogea root rot was studied in tomato cv. Counter grown under winter and summer conditions in rockwool culture. A nutrient temperature of 25°C resulted in increased root initiation and growth, higher in winter‐grown than in summer‐grown plants. Rhizosphere zoospore populations were greatly reduced at 25°C and above.

Growth of P. cryptogea in vitro was optimal between 20°C and 25°C and completely suppressed at 30°C. Encystment was enhanced by increased temperatures above 20°C. Zoospore release in vitro occurred in cultures maintained at constant temperatures in the absence of the normal chilling stimulus. Optimal release was at 10°C; no zoospores were released at 30°C.

Inoculated, winter‐grown tomato plants maintained at 15°C developed acute aerial symptoms and died after 21 days. Comparable plants grown at a root‐zone temperature of 25°C remained symptomless for the 3‐months duration of the experiment. Summer‐grown infected plants at the higher root temperature wilted but did not die. Enhanced temperature was ineffective as a curative treatment in summer‐grown plants with established infection.

Aerial symptoms of Phytophthora infection are seen as a function of the net amount of available healthy root. With high root zone temperatures this is determined by new root production and decreased inoculum and infection.
Distinction of strains of bean common mosaic virus and blackeye cowpea mosaic virus using antibodies to N‐ and C‐ or N‐terminal peptide domains of coat proteins
Authors: KHAN JAWAID A. , LOHUIS H. , GOLDBACH R. W. , DIJKSTRA JEANNE
Published: February 2008

Earlier attempts to discriminate serologically strains NL1, NL3 and NY15 of bean common mosaic virus (BCMV) and strain W of blackeye cowpea mosaic virus (B1CMV) had been unsuccessful. Antibodies directed towards N‐ and C‐, or N‐terminal peptide regions of the coat proteins of the above strains enabled the distinction between B1CMV‐W, BCMV‐NY15 and BCMV‐NL3 in electroblot immunoassay and in ELISA. The distinction was better with antibodies directed towards N‐termini than with those to N‐ and C‐termini. Strain NL1 of BCMV cross‐reacted with both B1CMV‐W and BCMV‐NY15, but not with BCMV‐NL3. Taxonomic implications of these findings are discussed.
The competitive effects of volunteer barley (Hordeum vulgare) on the growth of oilseed rape (Brassica napus)
Authors: LUTMAN P. J. W. , DIXON F. L.
Published: February 2008

The effects of competition from volunteer barley (Hordeum vulgare) on the growth and yield of oilseed rape (Brassica napus) were investigated in four experiments over three seasons. The growth of rape in the autumn was reduced by 50 ‐ 91 % by competition from 400 barley plants m‐2. A lower barley density of 200 plants m‐2 had less effect but still reduced growth of rape by 65 ‐ 81% in two of the experiments and 25 ‐ 40% in the other two. During winter and spring the barley decreased in vigour and in the spring the rape started to recover, especially on the early drilled (23 ‐ 30 August) plots. The rape sown in mid‐September recovered less quickly. In Experiment 3, herbicides applied in November to control barley did not result in increased growth of rape in winter but led to greater recovery in spring. The barley died during the winter in Experiments 2 and 4, even in the absence of herbicides. Despite the marked effects of barley on the growth of rape in the autumn, yields on plots that had previously contained 200 barley plants m‐2 were reduced by a maximum of only 16% in three of the experiments. In Experiment 3, where the barley was most competitive, this density and 400 plants m‐2 lowered yields by 39% and 78%, respectively. Where a herbicide was used in November to control the barley these yield losses were reduced to 5%. In many rape crops the cost of herbicide treatment would be greater than the financial returns from the expected increase in yield resulting from the control of weeds. Possible reasons for the small loss in yield of rape from barley densities that had substantial effects on the growth of rape in the autumn are discussed.
Effects of treating seed potatoes with trace elements on sprouting and microbial spoilage during storage under tropical conditions
Authors: SHASHIREKHA M. N. , NARASIMHAM P.
Published: February 2008

Attempts were made to extend the storage life of seed potatoes by treating them with trace elements as antimicrobial and antisprouting agents. In tests to measure the growth of Fusarium oxysporum, and Erwinia carotovora pv. carotovora it was found to be decreased more by iron, copper and zinc than by boron, manganese and molybdenum. Dipping seed tubers in aqueous solutions of trace element salts decreased both sprouting and microbial spoilage during storage at ambient conditions. Field testing at the end of storage proved that treating seed potatoes with ferrous sulphate did not decrease the yield of tubers or increase their iron content. It is suggested that trace elements may be used to extend the storage life of seed potato tubers, in tropical conditions.
Effect of soil compaction on growth, yield and light interception of selected crops
Authors: ASSAEED A. M. , McGOWAN M. , HEBBLETHWAITE P. D. , BRERETON J. C.
Published: February 2008

The response of spring barley (Hordeum vulgare, cvs Carnival and Atem), faba beans (Vicia faba, cv. Maris Bead), sugar beet (Beta vulgaris, cv. Monoire), forage maize (Zea mays, cv. Leader), forage peas (Pisum sativum, cv. Poneka) and white turnip (Brassica campestris, cv. Barkant) to topsoil compaction was investigated in a three year trial. Soil compaction was induced by tractor wheeling after crop sowing.

Compaction reduced leaf area and dry matter accumulation in all crops in every season. Yield of barley was reduced by 29%, 27% and 40% in 1984, 1986 and 1987 respectively. Yield of maize, peas and turnip decreased by 33%, 14% and 13% in 1986 and 25%, 16% and 19% in 1987. Yields of beans and sugar beet were decreased by 34% and 35% respectively in 1984.

Light interception was decreased in all crops in all three years of study but, with the exception of maize in 1987, the efficiency of conversion of radiant energy to dry matter was not significantly affected by soil compaction. It is concluded that reduced dry matter production and yield due to soil compaction was more a consequence of reduced light interception because of restricted leaf area development rather than as a result of an impaired ability of crops to utilise intercepted radiant energy.
The use of chlorophyll fluorescence in assessment of low temperature hardiness in blackcurrant (Ribes nigrum L.)
Authors: BRENNAN R. M. , JEFFERIES R. A.
Published: February 2008

The effect of freezing stress on chlorophyll fluorescence was examined in leaves of five genotypes of blackcurrant (Ribes nigrum L.). Minimum fluorescence (Fo), variable fluorescence (Fv) and the time for Fv to decay to half its maximum value (q1/2) all varied between genotypes. Freezing stress significantly reduced Fo in all genotypes, but the effect of freezing stress on Fv was non‐significant. Freezing stress significantly increased q1/2, but the effect varied significantly between genotypes. The increase in q1/2 induced by freezing stress was greatest in the cultivar Baldwin and least in the accession Ri‐74020‐6. The effects of freezing on chlorophyll fluorescence, particularly q1/2, corresponded to the susceptibility of the genotypes to spring frosts. It is concluded that chlorophyll fluorescence can provide a rapid screening technique for assessing frost hardiness in blackcurrant.
Low‐ethylene storage of apples cv. ‘Cox's Orange Pippin’: effects of ‘Rapid CA’ and ultra‐low oxygen
Authors: STOW J. , GENGE P.
Published: February 2008

Three methods of reducing ethylene accumulation in the flesh of apple fruits cv. ‘Cox's Orange Pippin’ during controlled atmosphere storage were compared with one another and with a control. They were: (a) rapid establishment of storage conditions, (b) treatment with 5% CO2 for 15 days prior to long‐term storage, and (c) lowering storage O2 from 1.25% to 0.75%. In all cases ethylene was either allowed to accumulate or maintained below 1 μl litre‐1. When ethylene was removed from the storage atmosphere all three methods reduced internal ethylene concentrations.

Although the firmness of fruits from two orchards was affected differently by ethylene removal, the effects on the retention of flesh firmness by ethylene removal and storage in 0.75% O2 were generally additive.

No adverse effects of storage in 0.75% O2 were observed.
The effect of introducing the aphid‐pathogenic fungus Erynia neoaphidis into populations of cereal aphids
Authors: WILDING N. , MARDELL SUSAN K. , BROBYN PATRICIA J. , WRATTEN S. D. , LOMAS JANET
Published: February 2008

The aphid‐pathogenic fungus Erynia neoaphidis, as dried fungus‐infected aphids, was applied to caged plots of winter wheat infested with cereal aphids at two sites, one in Hertfordshire and the other in Hampshire, in 1983. In each trial, the fungus became established in the aphid populations in the treated plots even though conditions were drier than average and therefore sub‐optimal for fungus spread. Treatment applied in the third week of June increased the proportion of infected aphids more than that applied two weeks later at one site, and the early application was the only treatment to have an obvious effect at the other. In spite of the observed effect of treatments on the proportion of infected aphids, the fungus failed to reduce the numbers of aphids relative to those in untreated plots, chiefly because in these plots many aphids were killed by fungi of the same species as that introduced and other related species from natural sources. Artificial introduction of E. neoaphidis acts too slowly and unpredictably to be likely to form a practical alternative to conventional insecticides for cereal aphid control.
Studies on the toxicity of insecticidal drift to the first instar larvae of the Large White butterfly Pieris brassicae (Lepidoptera: Pieridae)
Authors: SINHA S. N. , LAKHANI K. H. , DAVIS B. N. K.
Published: February 2008

The toxicity (LD,) of eight insecticides to 2–day‐old first instar larvae of Pieris brassicue was determined by topical application. On this basis, the insecticides could be ranked in ascending order viz. dimethoate > pirimicarb > phosalone > endosulfan > fenitrothion > pirimiphos‐methyl > fenvalerate > diflubenzuron. Relative to endosulfan, dimethoate and pirimicarb were 30–25 times less toxic while at the other extreme, fenvalerate (x 12) and diflubenzuron (x 26) were much more toxic to the larvae of P. brassicae.

A methodology was developed for examining the effects of spray drift through bioassay using these 2–day‐old larvae. Six field trials with commercial formulations were carried out in which variables other than the insecticide and wind speed were held constant as far as possible. Phosalone (700 g active ingredient ha) produced no effect beyond 1 m downwind at low wind speed (2 m s); at high wind speed (4 m s‐1). larval mortality (5.3%) was recorded up to 2m. Fenitrothion (1050 g a.i. ha‐1) at moderate wind speed (3 m s‐l) caused mortality up to 4 m while fenvalerate (30 g a.i. ha‐l) at the same wind speed affected larvae up to a distance of 8 m. Diflubenzuron at a very low dosage (6.5 g a.i. ha‐1) also produced effects up to 8 m. At the maximum approved dosage (100 g a.i. ha‐1), and at high wind speed (4.25 m s‐l), diflubenzuron killed 8.4% of the larvae at 16 m distance.

At wind speeds of 2 ‐ 3.5 m s‐1, spray deposits on the upper surfaces of water sensitive papers were high at 0 m and declined exponentially with distance. At higher wind speeds (4 ‐ 4.25 m s‐I) turbulence produced irregular deposits. Deposition on lower surfaces was much lower than on upper surfaces but the trends with distance and wind speed were the same.

The exponential relationships between mortality and distance, and drift deposition and distance, were examined. The results are discussed with respect to laboratory toxicities, application rates, wind speeds and ecological factors.
A comparison of inoculation techniques for assessment of germplasm susceptibility to Karnal bunt (Tilletia indica) disease of wheat
Authors: WARHAM ELIZABETH J.
Published: February 2008

Three inoculation techniques for Karnal bunt (Tilletia indica) disease of wheat were compared: 1) boot inoculation ‐ injection of inoculum with a hypodermic syringe into the boot; 2) spray inoculation ‐ inoculum sprayed at growth stages between heading and anthesis, and 3) cotton wool inoculation ‐ small pieces of cotton wool saturated in inoculum placed either inside the floret or between the spikelet and rachis. Each inoculation technique was assessed using susceptible cultivars to determine the optimum inoculum concentration, the ideal plant growth stage and the humidity requirements for successful infection.

Boot inoculation did not require high humidity and gave reliable infection with low secondary sporidia concentrations (1000–10 000/ml). The ideal plant growth stages for inoculation were early‐boot and mid‐boot. Spray inoculation required high secondary sporidia concentrations (50 000/ml) and 48 h of high humidity, but infection was initiated over a range of growth stages throughout heading and anthesis. Cotton wool inoculation gave low levels of infection at growth stages throughout heading and anthesis, even with high secondary sporidia concentrations (100 000/ml).
Effects of fungicides applied to seed potato tubers at harvest or after grading on fungal storage diseases and plant development
Authors: CARNEGIE S. F. , RUTHVEN A. D. , LINDSAY D. A. , HALL T. D.
Published: February 2008

An assessment was made over 3 years of the efficacy of thiabendazole, 2–aminobutane and a formulation of a mixture of thiabendazole and 2–aminobutane in controlling gangrene, skin spot and dry rot when applied either at harvest or after grading at different dates during the storage season.

After harvest applications, the incidence of gangrene was least on tubers treated with the mixture and generally greatest with thiabendazole. When applied after grading the efficacy of the fungicides was not affected by date of grading. Although 2–aminobutane applications at harvest or after grading were equally effective in controlling gangrene, thiabendazole and the mixture were less effective after grading where gangrene was prevalent in a stock. Thiabendazole and the mixture gave good control of dry rot when applied at harvest but were less effective when applied after grading, particularly late in the storage season. Dry rot was sometimes more prevalent on tubers fumigated with 2–aminobutane, especially those treated after grading. Skin spot was more effectively controlled by the mixture and 2–aminobutane than by thiabendazole but, with applications after grading, the efficacy of all fungicides declined the later the date of grading.

Plants grown from tubers treated with the mixture or its 2–aminobutane glycollate constituent exhibited characteristics associated with genetic variation.
Virus content of seed potato stocks produced in a unique seed potato production scheme
Authors: WILSON C. R. , JONES R. A. C.
Published: February 2008

Western Australia has a unique seed potato production scheme which has remained virtually unchanged for more than 60 years, consisting of summer plantings of predominantly one cultivar in wind‐exposed coastal swamplands. No rotation is used and the scheme relies on natural winter flooding and ‘grazing’ by sheep to eliminate unharvested tubers. Stocks are recycled every year with only limited inputs of pathogen‐tested seed tubers in recent times. Virus spread in the crop is controlled by selecting large tubers for planting, roguing, aphicide application and growing season inspections. Potato viruses X and S were commonly detected in old seed stocks produced by this scheme attaining 100% infection in some. Both viruses were less frequently found in newly introduced seed stocks. By contrast, potato virus Y was never detected and potato leaf roll virus rarely found.
Resistance to potato virus Y and potato virus X in Solanurn brevidens
Authors: GIBSON R. W. , PEHU E. , WOODS R. D. , JONES M. G. K.
Published: February 2008

Although Solanum brevidens could be infected with potato virus X (PVX), potato virus Y0 (PVY0) and PVYN, no symptoms of infection were apparent and tests by double antibody sandwich ELISA, electron microscopy and sap transmission to local lesion test plants indicated that the titres of PVX were less than a tenth of those of PVY0 and PVYN were less than a hundredth of those in infected plants of PDH40, a susceptible dihaploid clone of S. tuberosum cv. Pentland Crown. Furthermore, PVY0‐ and PVYN‐ infected leaves of S. brevidens were a poor source of inoculum in aphid transmission tests. The possibility of a common mechanism and genetic basis of resistance to PVY, PVX and potato leaf roll virus in S. brevidens is discussed.
Studies on Artioposthia triangulata (Dendy) (Tricladida: Terricola), a predator of earthworms
Authors: BLACKSHAW R. P.
Published: February 2008

Observations had linked the disappearance of earthworms from a grass field to the presence of Artioposthia triangulata. An experiment demonstrated that this land planarian could severely and quickly reduce numbers of four earthworm species. Two different approaches to sampling A. triangulata were investigated on a grassland site. The first used four different trap types (wood, ceramic tile, ‘corriboard’ plastic and 5 mm polystyrene beneath a ceramic tile) measuring 15 cm x 15 cm which were compared over a period of 18 wk. The second used one, or two, applications of dilute formalin solution to quadrats followed by counting the residual planarians by hand‐sorting the soil beneath the quadrat to a depth of 30 cm. The polystyrene traps were the most effective for detecting the presence of A. triangulata. No planarians were ever found by hand‐sorting after two formalin applications and it was concluded that formalin sampling provided a good estimate of the population density. Counts under traps were not related to absolute estimates of population densities so polystyrene type traps should only be used for detection of the planarians. A multiple regression relationship of A. triangulata weight over time in 5% formalin is presented and allows the original liveweight to be calculated from the weight in preservative. Planarian and earthworm population densities in eight fields were sampled and the planarians were found to be randomly distributed. Counts of planarians in 0.25 m2 quadrats were not related to numbers of earthworms but overall field population densities were. It is concluded that A. triangulata is a severe threat to the earthworm populations of Northern Ireland.
Responses of Schizaphis graminum (Homoptera: Aphididae) to leaf excision in resistant and susceptible sorghum
Authors: MONTLLOR C. B. , CAMPBELL B. C. , MITTLER T. E.
Published: February 2008

Greenbugs, Schizaphis graminum (Rondani), were reared on intact and excised leaves of varieties of sorghum which differed in their suitability as hosts for this aphid. Aphids grew poorly on intact leaves of three resistant varieties, but grew well on excised leaves of the same varieties. Leaf excision did not affect aphid growth on three susceptible varieties. By electronically monitoring the feeding behaviour of aphids on two resistant and one susceptible variety, significant differences were found in many parameters between aphids assayed on excised vs. intact leaves of only the resistant varieties. Aphids on excised leaves of the resistant varieties, and on excised or intact leaves of the susceptible variety, made fewer probes to the phloem, spending more time ingesting from phloem during each probe, compared to aphids on intact resistant plants. There was a higher level of free amino acids in excised leaves of all varieties, but aphid growth and feeding behaviour improved as a result of excision only on resistant varieties. This observation, coupled with the fact that intact plants of all varieties have similar amino acid levels, indicates that these nutrients are not of primary importance in sorghum suitability to the greenbug. Other explanations for the aphids' responses to excised leaves are discussed.
Ingestion of Pythium spp. by larvae of the fungus gnat Bradysia impatiens (Diptera:Sciaridae)
Authors: GARDINER R. B. , JARVIS W. R. , SHIPP J. L.
Published: February 2008

Mycelium, oospores and zoospore cysts of Pythium spp. were fed to larvae of the fungus gnat Bradysia impatiens. The fungal structures were all ingested and provided a complete nutritional source for the insect's development from egg to adult. Mycelium seemed the major source of food as only empty fragments were found either in the digestive tract or in larval faeces. Oospores appeared intact and were viable both during passage through the tract and when expelled. Germination of oospores was normal. Most encysted zoospores also survived passage through the gut, although some appeared damaged. After transferring recently‐fed larvae to a new food source, oospores were still detected in the digestive tract 48 h later. These results show that the larval stage of B. impatiens may serve as an important vector for Pythium spp.
Effect of moisture stress, plant population density and pathogen inoculation on charcoal stalk rot of sorghum
Authors: PANDE S. , MUGHOGHO L. K. , KARUNAKAR R. I.
Published: February 2008

The effects of moisture deficit stress, plant population density and pathogen inoculation technique on charcoal stalk rot in the sorghum hybrid CSH 6 were studied in the 1980–81 and 1981–82 post‐rainy seasons at three locations in India. Incidence and severity of charcoal rot caused by Macrophomina phaseolina were compared in three plant population densities, subjected to different moisture stress regimes created by withholding irrigation at various plant growth stages. Natural infections were compared to artificial inoculation with M. phaseolina. Combinations of moisture stress, plant population and inoculation treatments were compared to identify the combination most likely to develop maximum disease. Lodging, the first external symptom of charcoal rot, was significantly correlated with other disease symptoms used to measure charcoal rot, such as soft stalk, number of nodes crossed by M. phaseolina infection, root damage and plant senescence. In both seasons the highest incidence of lodging occurred when moisture stress was induced at the ‘flag leaf visible in the whorl’ growth stage. The greatest incidence of the disease was recorded in the highest plant population (266 700 plant ha‐) at all three locations. No significant differences were found between artificially and naturally inoculated treatments. The maximum number of lodged plants was found at a density of 266 700 plants ha‐1 when moisture stress was induced at the ‘flag leaf visible in the whorl’ growth stage.
Interaction of post harvest disease control treatments and gamma irradiation on mangoes
Authors: JOHNSON G. I. , BOAG T. S. , COOKE A. W. , IZARD M. , PANITZ M. , SANGCHOTE S.
Published: February 2008

The effects of gamma irradiation and disease control treatments on disease severity and post harvest quality of several mango cultivars were investigated.

In mangoes cv. Kensington Pride, irradiation doses ranging from 300–1200 Gy reduced disease, but the level of control was not commercially acceptable. Hot benomyl immediately followed by irradiation provided effective control of anthracnose (Colletotrichum gloeosporioides) and stem end rot (Dothiorella dominicana) during short‐term storage (15 days at 20°C). The effects of the two treatments were additive.

Satisfactory disease control was achieved during long term controlled atmosphere storage when mangoes were treated with hot benomyl followed by prochloraz and then irradiated. Effects of fungicide treatment and irradiation were additive. Fungicide, or irradiation treatments alone, were unsatisfactory.

Irradiation of cv. Kensington Pride at doses in excess of 600 Gy caused unacceptable surface damage (i.e. lenticel spotting, surface discolouration and retardation of degreening) which was particularly severe after long‐term controlled atmosphere storage.

In a separate short‐term storage trial, several other mango cultivars were assessed. Hot benomyl followed by prochloraz controlled anthracnose on all cultivars and stem end rot on some. Irradiation at 600 Gy contributed only minor improvements to disease control. The severity of surface damage that developed following irradiation and fungicide treatment varied with cultivars.
Assessment of UK hops for the occurrence of hop latent and hop stunt viroids
Authors: BARBARA D. J. , MORTON A. , ADAMS A. N.
Published: February 2008

The occurrences and distributions of hop stunt (HSVd) and hop latent (HLVd) viroids were assessed by a nucleic acid hybridisation assay, using samples from 476 commercial hop plantings in the UK. These samples represented about half of the UK production.

HLVd was detected in c. 17% of the samples, with infection in different cultivars ranging from 0% to 89%. This viroid was found in all cultivars sensitive to Verticillium wilt except cv. Sunshine, an old cultivar grown on only one farm in the UK. Two minor wilt‐tolerant cultivars were also found to be infected at low frequencies, but the main commercially‐important wilt‐tolerant cultivars were all uninfected. A high proportion of the nuclear stock mother plants in the “A +” house at the Institute of Horticultural Research Dept of Hops Research, Wye College were infected. Circumstantial evidence, based on the planting dates of infected gardens, suggests that infection became established in the hop propagation system during the late 1970s and that there was a major increase in the prevalence of HLVd as a result. Whether this contamination of propagating material arose because of spread from long‐standing infections or because the viroid was newly introduced into the UK, is not known.

All samples were also tested for HSVd but this viroid was not detected in any UK hop material.
Control of slugs with contact‐action molluscicides
Authors: HENDERSON I. F. , MARTIN A. P.
Published: February 2008

A number of iron and aluminium compounds were compared as contact‐acting poisons against the slug Deroceras reticulatum, by confining slugs on treated surfaces of glass and wet soil in laboratory tests. Simple metal salts were effective poisons when applied to a glass surface, but were rapidly inactivated when applied to wet soil. Chelation of both metals with organic ligands retarded the rate of attenuation on wet soil. In a field trial D. reticulatum and Arion spp. slugs were killed by a broadcast application of the chelate iron (III) 2,4‐pentanedionate applied at 40 kg a.i. ha‐1.
The effects of lodging and a paclobutrazol — chlormequat chloride mixture on the yield and quality of oilseed rape
Authors: BAYLIS A. D. , WRIGHT I. T. J.
Published: February 2008

The effects of lodging and a plant growth regulator mixture on oilseed rape cv. Ariana were studied in three field experiments. Natural and artificially induced lodging treatments varying in time of imposition and severity were compared to a supported control. A mixture of paclobutrazol and chlormequat chloride was applied either as a spray or as paclobutrazol granules followed immediately by a chlormequat chloride spray.

In 1987, severe lodging treatments reduced yield by up to 52%. Yield penalties varied with the time at which lodging was imposed. Yield was inversely correlated with the ground cover of volunteers growing from shed seed under lodged crops.

In 1988, two experiments showed increased incidence of disease and decreases in seed yield and quality in lodged crops. Yield reductions were related to the severity of lodging. Lodging decreased oil contents and increased glucosinolate levels. PGR treatments reduced lodging and maintained yield at a level not significantly different to a supported control treatment. Oil contents were also similar in seed from PGR treated and control plots. Glucosinolate levels in PGR treated seed were similar to control levels in one experiment and intermediate to those from control and artificially lodged plots in another experiment.

The results are discussed in relation to the use of PGRs to prevent lodging in ‘double zero’ varieties of oilseed rape, and the potential losses from using ground vehicles to apply pesticides after flowering.
Measurement and classification of genetic diversity in okra (Abelmoschus esculentus)
Authors: ARIYO O. J.
Published: February 2008

Eighteen accessions of okra of diverse ecological background were evaluated for genetic variability through the techniques of coefficient of racial likeness (CRL) and principal coordinate analysis (PCO). The variation patterns among the accessions were classified by using the techniques of metroglyph analysis and single‐linkage cluster analysis. CRL and PCO produced similar results on the diversity of the accessions but the grouping of the accessions by metroglyph analysis and SLCA produced different results. The usefulness of metroglyph analysis depends on the amount of variation accounted for by the two principal characters on which the two co‐ordinate axes are constructed. The techniques are compared.
Influence of drought and flowering on growth and water relations of perennial ryegrass populations
Authors: THOMAS H. , EVANS C.
Published: February 2008

Spring‐sown (vegetative) and autumn‐sown (flowering) swards of Lolium perenne cvs Melle, Aurora and their hybrid growing in 0.9 m deep bins of soil in the glasshouse were compared, a) as drought progressed from June to August 1986, and b) after cutting, fertilising and re‐watering.

During drought, vegetative plants produced more herbage, had initially higher leaf extension rates, had longer and wider leaves, maintained more tillers, had lower mortality, adjusted osmotic potential more effectively and had stomata less sensitive to stress than did flowering plants. On re‐watering, previously stressed flowering plants regrew more slowly than the irrigated controls, whereas previously stressed vegetative plants regrew more rapidly than the controls.

Aurora was the most drought‐resistant population, mainly because of low tiller death rates. The hybrid tended to have the lowest leaf water potentials and conductances and grew poorly during drought. Possible underlying physiological mechanisms are discussed.
Uptake of 14C‐gibberellic acid by mature grapefruit (Citrus paradisi Macf.) as affected by relative humidity and method of application
Authors: GREENBERG J. , GOLDSCHMIDT E. E.
Published: February 2008

Effects of the method of application and relative humidity on the uptake of 14C‐gibberellic acid (14C‐GA3) by mature grapefruit (Citrus paradisi Macf.) were examined. Uptake was higher when 14C‐GA3 was applied as a ‘drying‐out’ solution than as a ‘non‐drying’ solution. When 14C‐GA, was applied by the ‘drying‐out’ method, which closely imitates field conditions, rates of uptake were very high while the solution was drying out and during the first few hours after drying. Uptake from the dry residue continued in decreasing rates till the end of the experiment (72 h). Uptake from the dry residue was higher when fruits were incubated at 100% than at 50% relative humidity (RH). Transfer of fruits from 50% to 100% RH as late as 48 h after drying still increased the rate of uptake. Drying‐out treatment solutions produced higher uptake rates with neutral (pH 7) as well as acid (pH 4) treatment solutions, and in the presence of triton B‐1956, Triton X‐100 or L‐77 surfactants.
Free amino acid content of phloem sap from Brassica plants in relation to performance of Lipaphis erysimi (Hemiptera: Aphididae)
Authors: WEIBULL J. , MELIN G.
Published: February 2008

Cultivars of Brassica juncea, B. napus and B. campestris, differing in host‐suitability to the mustard aphid (Lipaphis erysimi pseudobrassicae Kalt.), were analysed for their phloem sap content of free amino acids. Sap was collected from excised mustard aphid stylets and analysed by means of high performance liquid chromatography. Aspartic and glutamic acid were, together with glutamine, the dominating amino acids. All plants had very little glycine, γ‐aminobutyric acid (GABA), methionine and tryptophan in their sap. This amino acid pattern closely resembled that of cereals. The total concentration and the individual composition of amino acids were not found to be related to the level of aphid resistance previously found in the investigated Brassica species. However, one B. campestris cultivar, yellow sarson YSB‐9, on which the aphids were shown to grow more slowly, had less amino acid content than other B. campestris varieties. The slow population growth of aphids on B. juncea, compared to that on B. campestris, is probably due to other than nutritional factors.
Reproductive rate of the Indian mustard aphid (Lipaphis erysimi pseudobrassicae) on different Brassica oilseeds: colmparisons with Swedish strains of mustard (Lipaphis erysimi erysimf) and cabbage aphid (Brevicoryne brassicae)
Authors: RONQUIST F. , AHMAN INGER
Published: February 2008

The reproductive rate of the Indian mustard aphid (Lipaphis erysimi pseudobrassicae), a serious pest on Brassica oilseeds in India, was compared with that of Swedish strains of mustard aphid (L. e. erysimi) and cabbage aphid (Brevicoryne brassicae) on six common Indian and Swedish Brassica oilseed cultivars. There were clear differences between L. e. erysimi and L. e. pseudobrassicae in the relative suitability of the cultivars, emphasisipg the biological differences between these aphids. B. brassicae had similar reproductive rates on all cultivars.

In addition, the reproductive rate of L. e. pseudobrassicae was measured on both young and old plants of the six Brassica oilseed cultivars and 14 Indian rai (B. juncea) cultivars. Among the six Brassica cultivars, the reproductive rates were highest on turnip rape and toria (B. campestris), and lowest on yellow sarson (B. campestris) and rai (B. juncea). The ranking of the cultivars was similar for young and old plants. There were no significant differences between the rai (B. juncea) cultivars tested, neither among young nor among old plants. These results from laboratory studies are compared with field data from India on the relative susceptibility of different Brassica oilseed cultivars to L. e. pseudobrassicae.
Factors influencing oviposition behaviour of the sorghum midge, Contarinia sorghicola Coq.
Authors: SHARMA H. C. , LEUSCHNER K. , VIDYASAGAR P.
Published: February 2008

Visual stimuli influence the orientation behaviour of the sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae). Yellow, red and white colours are attractive to the midge while blue and black are least attractive. Sorghum panicles covered with blue‐ or black‐coloured bags in a headcage showed maximum midge damage, while the reverse was true for panicles covered with yellow, red, and white coloured bags.

Panicles at half‐anthesis with viable pollen and receptive stigmata suffered higher damage than those at the pre‐ and post‐anthesis. Physical removal of anthers and stigmata significantly reduced the oviposition by the sorghum midge. Reduced oviposition/adult emergence was also recorded in male sterile sorghum lines (2219A and 296A) or through chemically‐ (Ethrel) (2‐Chloro ethyl‐phosphonic acid) induced male sterility in panicles of the sorghum cultivar, Swarna. Chemical stimuli from viable pollen and receptive stigmata and to a limited extent physical stimuli, govern the oviposition behaviour of the sorghum midge.

Sorghum cultivars IS 12573C, S‐GIRL‐MR1 and IS 2816C showed antixenosis to adult midges. However, these cultivars became susceptible under no‐choice conditions in the headcage. DJ 6514 and IS 12666C were attractive to the adult midges, but showed antixenosis to oviposition under natural and no‐choice conditions. Genotypes with short florets showed antixenosis for oviposition. Ovary and anther breadth and tannin content of grain showed negative associations with oviposition. Cultivar antixenosis to adult midges and oviposition is an important component of resistance to the sorghum midge.