bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of reducing growth in winter wheat on the population dynamics of the grain aphid Sitobion avenae (F.)
Authors: Beed F. , Winder L. , Marchesi A. , Duffield S.
Published: March 2003

1 The effect of reducing the growth of winter wheat on population size and development of the grain aphid Sitobion avenae was studied.

2 Automatic, mobile, crop shading devices, which reduced radiation comparable to levels found on a cloudy day, whilst minimizing other climatic changes, were used to reduce crop growth. Shading was applied between either GS 31 and 39 (1st node detectable → flag leaf ligule just visible) or GS 39 and 55 (flag leaf just visible → 50% of inflorescence emerged).

3 Sitobion avenae populations were initiated at GS 55 and highest populations were subsequently observed on plants shaded between GS 31 and 39.

4 Individual aphids confined within clip cages were observed to measure development from birth to adult moult, adult lifespan and fecundity. Results indicated that adult lifespan was shortest on plants shaded between GS31 and 39, whilst there were no differences in development time or fecundity.

5 Possible explanations for these observations are discussed.
Rainfall and parasitic wasp (Hymenoptera: Ichneumonoidea) activity in successional forest stages at Barro Colorado Nature Monument, Panama, and La Selva Biological Station, Costa Rica
Authors: Shapiro B. A. , Pickering J.
Published: March 2003

1 In 1997, we ran two Malaise insect traps in each of four stands of wet forest in Costa Rica (two old‐growth and two 20‐year‐old stands) and four stands of moist forest in Panama (old‐growth, 20, 40 and 120‐year‐old stands).

2 Wet forest traps caught 2.32 times as many ichneumonoids as moist forest traps. The average catch per old‐growth trap was 1.89 times greater than the average catch per second‐growth trap.

3 Parasitoids of lepidopteran larvae were caught in higher proportions in the wet forest, while pupal parasitoids were relatively more active in the moist forest.

4 We hypothesize that moisture availability is of key importance in determining parasitoid activity, community composition and trophic interactions.
Geographic and parental influences on diapause by a polyphagous insect herbivore
Authors: Hunter Mark D. , McNeil Jeremy N.
Published: March 2003

1 Facultative diapause permits insects to initiate an additional generation when conditions are favourable, or to enter diapause when they are not. Although the principle environmental cues for diapause induction are often temperature and photoperiod, we demonstrated recently that the quality of host plant consumed by the larvae ofChoristoneura rosaceana(Harris) (Lepidoptera: Tortricidae) influences the proportion of larvae that enter diapause and therefore voltinism.

2 Previous work has also suggested that non‐Mendelian parental effects influence diapause byC. rosaceanalarvae, but the mechanism was not established. Here, we report further evidence for parental effects on diapause and examine whether parental diet influences diapause induction.

3 We collected larvae ofC. rosaceanafrom six sites at three latitudes in the Province of Québec. There was an increase in the proportion of larvae entering diapause with increasing latitude. Rearing larvae under identical conditions on artificial diet for two generations significantly reduced variation in diapause among populations within a given latitude, and supported the existence of parental effects that influence offspring diapause.

4 Experiments with different host plants and high‐ vs. low‐quality artificial diets provided no evidence that the parental effects on offspring diapause were based on the quality of food consumed by parents. Diapause inC. rosaceanaappears influenced by a hierarchy of cues, including temperature, photoperiod, current larval diet and parental environment.
Ecphylus silesiacus (Ratz.) (Hymenoptera, Braconidae), an important elm bark beetle parasitoid
Authors: Manojlović Bozidar , Zabel Anton , Stanković Sladjan , Kostić Miroslav
Published: March 2003

1 Ecphylus silesiacus (Ratz.) (Hym. Braconidae) parasitizes larvae of elm bark beetles (Coleoptera: Scolytidae) occurring in thin bark. Pteleobius kraatzi (Eichh.), Scolytus pygmaeus (Fab.), Scolytus multistriatus (Marsh) and Scolytus ensifer (Eichh.) are the most suitable hosts. Scolytus scolytus (Fab.) occurring in thicker bark, is not such a suitable host for E. silesiacus. Ecphylus silesiacus only parasitized this species in bark forks.

2 Under experimental conditions, P. kraatzi produced the largest number of elm bark beetle adults per maternal gallery and had the longest development period, while S. scolytus produced the smallest number of adults and had the shortest development period.

3 Ecphylus silesiacus had the lowest reproduction, the shortest development period and the least favourable sexual ratio, on S. scolytus larvae, and the highest production, the longest developmental period and the most favourable sexual ratio on P. kraatzi and S. pygmaeus larvae.

4 Ecphylus silesiacus adults fed with Parker's diet and the nectar of the melliferous plant Daucus carota L. (Umbelliferae), lived longer, parasitized a greater percentage of S. pygmaeus larvae, and had a significant offspring production compared with adults without additional diet.
Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops
Authors: Nicholls Clara I. , Parrella Michael P. , Altieri Miguel A.
Published: March 2003

1 Maintenance of floral diversity throughout the growing season in vineyards in the form of summer cover crops of buckwheat (Fagopyrum esculentum Moench) and sunflower (Helianthus annus Linnaeus), had a substantial impact on the abundance of western grape leafhoppers, Erythroneura elegantula Osborn (Homoptera: Cicadellidae), and western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and associated natural enemies.

2 During two consecutive years, vineyard systems with flowering cover crops were characterized by lower densities of leafhoppers and thrips, and larger populations and more species of general predators, including spiders.

3 Although Anagrus epos Girault (Hymenoptera: Mymaridae), the most important leafhopper parasitoid, achieved high numbers and inflicted noticeable mortality of grape leafhopper eggs, no differences in egg parasitism rates were observed between cover cropped and monoculture systems.

4 Mowing of cover crops forced movement of Anagrus and predators to adjacent vines resulting in the lowering of leafhopper densities in such vines.

5 Results indicate that habitat diversification using summer cover crops that bloom most of the growing season, supports large numbers of predators and parasitoids thereby favouring enhanced biological control of leafhoppers and thrips in vineyards.
Effects of leaf beetle damage on stem wood production in coppicing willow
Authors: Björkman Christer , Höglund Solveig , Eklund Karin , Larsson Stig
Published: March 2003

1 The effect of defoliation by larvae of the leaf beetle Phratora vulgatissima on current‐year stem wood production of resprouting Salix viminalis was investigated for two years. Adjacent subplots with varying levels of defoliation within one large willow plantation in south Sweden were studied in the two years.

2 High defoliation levels reduced stem wood production by an average of 32 and 39% in the two years, respectively.

3 Medium defoliation levels reduced stem wood production by 16% in one year. In the other year, the stem wood production of medium‐defoliated stools did not differ significantly from stools exposed to low defoliation, i.e. there was full compensatory growth.

4 The main difference between the year with compensatory growth and the one without was that overall productivity was higher in the year with compensation. This finding forms the basis for a mechanistic model by which compensation could be accomplished. We propose that the major contribution to full compensation comes from an increased growth among intermediate‐sized shoots of medium‐defoliated stools relative to the corresponding shoots in stools exposed to low defoliation.
A four‐year investigation into the efficacy of domiciles for enhancement of bumble bee populations
Authors: Barron M. C. , Wratten S. D. , Donovan B. J.
Published: March 2003

1 Eighty four‐unit domiciles for introduced bumble bees (Bombus spp.) were placed in 16 field margins at Lincoln, New Zealand in the 1995–96 southern summer. Fifty‐five were placed in the margins of intensively managed fields, with the remaining 25 being in less disturbed habitats, which had more spring/summer floral resources.

2 The number of nests founded over the four‐year study period increased from one to 27. Bombus hortorum was a much more frequent colonist than was B. terrestris, with B. ruderatus colonizing only in the fourth year.

3 In the ‘intensive’ sites, mean four‐year occupancy was only 2%, whereas in the less disturbed sites it was 13%.

4 There was a positive association between bumble bee occupancy of the domicile compartments in the previous year and occupancy in the current year. No association was found between previous occupancy by mice and subsequent occupancy by bumble bees.

5 The potential for adding Bombus nest sites to agricultural land to enhance local populations, and, potentially, pollination of seed crops, is discussed. Adding domiciles in intensively managed landscapes may not be very effective unless spring floral resources are enhanced as well.
Oviposition preference and larval survival of Diprion pini on Scots pine clones in relation to foliage characteristics
Authors: Pasquier‐Barre F. , Géri C. , Goussard F. , Auger‐Rozenberg M. A. , Grenier S.
Published: March 2003

1 When laying eggs, adult female Diprion pini discriminated between clones of Scots pine, Pinus sylvestris.

2 Larval survival was affected by Scots pine clone but was not correlated with oviposition preference.

3 Diprion pini laid most eggs on tougher needles of Scots pine.

4 There was no evidence to suggest that D. pini is responding to the monoterpene composition of the foliage.
Biology, demography and community interactions of Tarsonemus (Acarina: Tarsonemidae) mites phoretic on Dendroctonus frontalis (Coleoptera: Scolytidae)
Authors: Lombardero María J. , Klepzig Kier D. , Moser John C. , Ayres Matthew P.
Published: March 2003

1 Dendroctonus frontalis, the southern pine beetle, is associated with a diverse community of fungi and mites that are phoretic on the adult beetles. Tarsonemus ips, T. kranzti and T. fusarii (Acarina: Tarsonemidae) may interact within this community in ways that link the population dynamics of D. frontalis, the mites and three dominant species of fungi. We explored species associations by comparing the dietary suitability of different fungi for Tarsonemus spp.

2 All three mite species fed and reproduced at high rates when feeding on the bluestain fungus, Ophiostoma minus, which is an antagonist of D. frontalis larvae.

3 Mites also had positive population growth rates when feeding upon Ceratocystiopsis ranaculosus, one of the mycangial fungi, but could barely reproduce when feeding upon Entomocorticium sp. A, the mycangial fungus that is most suitable for D. frontalis.

4 During the time from colonization of a tree by D. frontalis adults until departure from the tree of their progeny (≈ 40 d at 30 °C), mite populations feeding upon O. minus can increase by factors of up to 209 (T. fusarii), 173 (T. ips) or 384 (T. krantzi). These high growth rates are allowed by rapid development (age of first reproduction = 8–9 d), high fecundity (≈ 1 egg/d) and high longevity (> 28 d).

5 Precocious mating increases the chance that females are mated prior to colonizing a new tree and arrhenotokous parthenogenesis permits reproduction by unmated females.

6 Tarsonemus mites may introduce negative feedback into D. frontalis population dynamics by generating indirect interactions between D. frontalis and O. minus.
Complex emergence patterns in a bark beetle predator
Authors: Reeve John D.
Published: March 2003

1 The emergence pattern of Thanasimus dubius (F.) (Coleoptera: Cleridae), a common predator of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), was studied under field conditions across different seasons. A simple statistical model was then developed to characterize the emergence data, using the truncated geometric distribution. Data are also presented on the mortality of T. dubius eggs at various temperatures and humidities in an effort to explain certain aspects of emergence behaviour.

2 Emergence of T. dubius from a given tree usually occurred in several discrete episodes across a two‐year period, with most individuals emerging in spring or autumn. Almost no emergence occurred in July and August, which may be an adaptation to avoid high temperature mortality. Emergence patterns appeared similar across seasons, with the time of year serving mainly to shift the pattern through time.

3 Cycles in D. frontalis abundance may be the result of delayed density dependence generated by its natural enemy complex. The predator T. dubius is likely to be an important component of this delayed density dependence, because of its lengthy development time and apparent impact on D. frontalis.
Larval performance in relation to oviposition site preference in olive kernel moth (Prays oleae Bern., Yponomeutidae, Praydina)
Authors: Petrakis Panos V.
Published: March 2003

1 The tri‐voltine moth Prays oleae Bern. spends its larval stages on the native olive tree (Olea europaea L. var. sylvestris Brot. and five cultivars, Oleaceae) mining the leaves, the flowers and the fruits in each generation; it seldom switches to other native or introduced confamilial plant species.

2 In this study the pattern of oviposition of the olive moth was examined in olive fields and natural vegetation, in relation to in situ recruitment as an outcome of processes such as density dependence or risk spreading.

3 Larval body size (width of epicranial sclerites) was also examined and compared between host substrates, years and morphological, physiological, ecological and nutritional attributes of the host.

4 The factors influencing the oviposition pattern of the olive moth such as the carbon/nitrogen ratio, number of flowers, branch length and previous leaf damage were ranked differently in different cultivars.

5 ‘Hot spots’, i.e. olive trees or parts of trees receiving a high egg load, were found to be the result of in situ recruitment.

6 Physiological mortality among first instar larvae was significantly negatively correlated with the number of oviposited upon leaves; suggesting that the adult selects for oviposition the best available substrate.

7 As adult moths selected leaves with minimal probability of abscission for oviposition, leaf abscission was not a major mortality factor, although first instar larvae reduced leaf longevity.

8 Host quality did not affect all larval stages in the same way.

9 The more nutritionally poor the substrate, the longer the duration of the larval stage feeding on it. The phenological timing of the insect life stages very closely tracks the phenological phases of its host plant, primarily focusing on the most nutritious host stage in terms of larval performance.
Inter‐tree distribution of the spruce web‐spinning sawfly,Cephalcia abietis, at endemic density
Authors: Rodeghiero M. , Battisti A.
Published: March 2003

1 The spatial distribution of forest defoliating insects at endemic density is a generally little known aspect of pest biology, which may have some importance in monitoring and prediction of outbreaks. In a natural spruce stand in Northern Italy it was possible to detect the presence of some species of web‐spinning sawflies (Cephalciaspp.) at endemic density. This was done over a 3‐year period by using trapping devices for both adults and larvae, including a trap which intercepted adult females climbing the trunk. Traps were operated on eight sample trees with signs of defoliation of the previous year (focal trees) and on 14 trees lacking signs of larval feeding (neighbour trees).

2 Trunk traps on focal trees caught a higher number of adult females than traps on neighbour trees in each of the 3 years considered. The distribution pattern of catches was not spatially autocorrelated at any of the distance bands considered. Focal trees produced more mature larvae per adult female ofC. abietisthan neighbour trees, indicating that insect performance was higher on focal trees.

3 The endemic population density ofC. abietiswas similar to that observed in other forests and the relationships between yellow trap catches and prepupal density fitted adequately with the predictive model validated forC. arvensis. The endemic density of the spruce web‐spinning sawflies seems to he higher than that of pine diprionids, and outbreak‐prone species ofCephalciaseem to be more abundant than non‐outbreak species even at very low population level.
Egg allocation by Bracon hylobii Ratz., the principal parasitoid of the large pine weevil (Hylobius abietis L.), and implications for host suppression
Authors: Henry C. J. , Day K. R.
Published: March 2003

1 The braconid parasitoid Bracon hylobii Ratz. is one of the few specialist natural enemies of the large pine weevil, Hylobius abietis L., a destructive pest of conifer transplants. An assessment of its role as an agent of biological control requires a detailed knowledge of the allocation of its reproductive effort.

2 Parasitoid females were continuously observed in laboratory culture with individually reared host larvae in bark discs. The outcome of sequential parasitoid–host encounters was recorded by subsequent examination of hosts and by rearing all parasitoids.

3 Parasitoids avoided ovipositing on host larvae < 100 mg fresh weight, even though such larvae represented sufficient biomass for complete parasitoid development. All larger larvae were vulnerable to attack, which leaves a window of vulnerability for parasitoids of about 90% of weevil larval life.

4 Parasitoids presented with a range of host sizes showed no preference above 100 mg for the size of host first attacked, but allocated more eggs and a greater total handling time to larger hosts.

5 Most eggs were deposited on the first host attacked, with progressively fewer allocated to subsequent hosts. However, oviposition experience did not affect the time spent on the next host.

6 From these results it is anticipated that when weevil larval size is reduced by less favourable feeding substrates, fewer parasitoid eggs will be allocated to each but more host larvae will ultimately be attacked.

7 Generation time, host finding, oviposition rate, clutch size, life expectancy and diapause induction are strongly affected by temperature. Life expectancy is substantially shorter for parasitoids deprived of non‐host food supplement. At 15 and 20 °C the number of hosts attacked and the number of eggs deposited decreased with female age.

8 Bracon hylobii is inevitably poorly synchronized with a variable life‐cycle host; it is egg‐limited and can enter diapause at a relatively high field temperature. None of these characteristics suggest that it could stabilize the abundance of its host below an economically acceptable threshold density. However, the reproductive potential of the parasitoid suggests that it could make a significant contribution to larval mortality and suppress adult recruitment, thus complementing other control strategies.
Effect of hunger on yellow water trap catches of hoverfly (Diptera: Syrphidae) adults
Authors: Hickman Janice M. , Wratten Stephen D. , Jepson Paul C. , Frampton Chris M.
Published: March 2003

1 An experiment was conducted in a winter wheat field using yellow water traps at crop height and at ground level, near to and distant from flowers, to test the hypothesis that such traps are seen as a source of food by flower‐feeding adult hoverflies and are therefore likely to selectively trap hungry individuals. Hoverflies caught in each trap were counted and identified and the amount of pollen in their guts was assessed. Ratios of numbers of hoverflies seen in the wheat crop to numbers caught in nearby traps were compared for the different treatments.

2 Most hoverflies were caught in crop‐high traps but they included a high proportion of individuals with empty guts. The taxa were: Episyrphus balteatus (De Geer), Metasyrphus corollae (F.) (these species together accounted for over 90% of the individuals trapped), with Sphaerophoria spp., Syrphus spp., Scaeva pyrastri (L.), Melanostomini and unidentified others making up the rest.

3 Significantly fewer hoverflies were captured in low than in high traps. The ratios of numbers trapped to numbers observed, in flower and in no flower treatments would be expected to be the same if the traps were not selective. This was supported for low traps. With high traps, however, there was a highly significant difference between the ratios (71.34 and 126 : 8, respectively).

4 Flies captured in high traps had less pollen in their gut than those captured in low ones. At each distance, more E. balteatus captured in high traps were in pollen category 1 (< 20 grains) than in any other category. The opposite state was seen in low trap catches, where most flies were in category 5 (> 5000 grains). Median pollen categories were 2 (21–200 grains) and 4 (1501–5000 grains) for flies caught in high and low traps, respectively.

5 The ecological selectivity of traps according to their height and the physiological condition of the targeted individuals is a problem likely to affect many trapping systems apart from the one described in this paper.
Preliminary experiments on the olfactory responses of Pterostichus melanarius Illiger (Coleoptera: Carabidae) to intact plants
Authors: Tréfás H. , Canning H. , McKinlay R. G. , Armstrong G. , Bujáki G.
Published: March 2003

1 In two successive years, the olfactory responses of Pterostichus melanarius Illiger (Coleoptera: Carabidae) to intact cabbage and white clover plants were studied, using a four‐arm olfactometer.

2 The first set of experiments tested the response to the odours of cabbage, white clover and the two plants grown together against potting compost; in the second and third sets of experiments, white clover and cabbage were tested, respectively.

3 The results indicate that female P. melanarius individuals are arrested by the combined odours of cabbage and white clover, spending significantly more time in the cabbage with white clover odour field than in either the cabbage, white clover or control odour fields.

4 Similar results were not found for males.

5 Cabbage plants alone did not elicit significant responses in either sex.

6 White clover alone did not elicit significant responses by females and the responses of males were not uniform in the two successive years.
The biology and management of wireworms (Agriotes spp.) on potato with particular reference to the U.K.
Authors: Parker William E. , Howard Julia J.
Published: March 2003

1 This paper reviews and interprets relevant work on the biology and management of wireworms (Agriotes spp.) within the context of potato production in Europe, with particular reference to the U.K. Although the review concentrates on Agriotes spp., the extensive world literature on other Elateridae of economic importance is also drawn upon.

2 Possible reasons for the apparent increase in the importance of wireworms on the potato crop are discussed, followed by a review of wireworm biology, risk assessment techniques (soil sampling, bait trapping and adult pheromone trapping), crop damage, and cultural, biological and chemical control methods.

3 It is clear that the process of site risk assessment followed by appropriate control measures (usually insecticide use) will remain the mainstay of wireworm management programmes. However, there is considerable scope for adopting new risk assessment techniques, such as pheromone trapping of adult beetles.

4 These control measures will need to be underpinned by a greater understanding of wireworm biology, particularly adult dispersal. Factors affecting the initiation and maintenance of wireworm populations in individual fields also require further study. The current use of insecticides could also be optimized by a better appreciation of the interactions between insecticide use, potato variety choice and harvest dates.
Population abundance and movement of Frankliniella species and Orius insidiosus in field pepper
Authors: Ramachandran Suresh , Funderburk Joe , Stavisky Julie , Olson Steve
Published: March 2003

1 A recent study revealed the capacity of the Orius insidiosus to suppress populations of Frankliniella spp. in field pepper during the spring when thrips are rapidly colonizing and reproducing. In this study, population abundance in pepper during spring, summer, and autumn was determined to understand better predator/prey dynamics under local conditions. Local movement between pepper flowers also was quantified to examine how population attributes of the predator allow suppression of rapidly moving populations of prey.

2 Randomized complete block experiments established in the autumn of 1998 and the spring of 1999 included treatments of biological and synthetic insecticides, which altered the population densities of predator and prey. Numbers of O. insidiosus in relation to prey were sufficient in 1998 to prevent build‐up of thrips populations. In 1999, populations of thrips were unable to recover from near extinction owing to persistence of the predator. The predator rapidly recolonized plots treated with insecticide.

3 Greenhouse plants of the same age as field plants were used to monitor movement by predators and prey. Movement by F. occidentalis was limited, whereas F. tritici and F. bispinosa moved rapidly to the greenhouse plants. The males of each thrips species moved more rapidly than the females. There was evidence that rapid movement assisted F. tritici and F. bispinosa in avoiding predation, but O. insidiosus also moved very rapidly to the greenhouse plants. This attribute explains the predator's ability to suppress thrips rapidly even when populations are rapidly colonizing and reproducing in the flowers.
Within‐tree and seasonal distribution of the pine woolly aphidPineus boernerionPinus kesiyatrees
Authors: Chilima C. Z. , Leather S. R.
Published: March 2003

1 The spatial and temporal distribution of pine woolly aphids,Pineus boerneri(Homoptera: Adelgidae) a pest of exotic pine trees in Malawi, was investigated in 5‐year‐oldPinus kesiyatrees.

2 Pineus boerneriwas generally found to settle and reproduce on the outer shoot‐end sections of youngP. kesiyatrees. There was no evidence of preference for any particular levels of the tree canopy.

3 The study suggests that the biological performance and, by implication, the pest status ofP. boerneriin youngP. kesiyatrees can be influenced by external factors, particularly by the within‐tree and seasonal fluctuations in the level of nitrogen in the host trees, total rainfall and canopy structure.

4 These findings are discussed in relation to possible management and control ofP. boerneriin Malawi.
Effects of host plant species on the interaction between the parasitic wasp Diospilus capito and pollen beetles (Meligethes spp.)
Authors: Billqvist Andreas , Ekbom Barbara
Published: March 2003

1 Field studies were conducted in central Sweden to establish whether two host plants with high and low suitability for pollen beetles (Meligethes aeneus Fabr. [Coleoptera: Nitidulidae] and Meligethes viridescens Fabr.) affected the parasitoid Diospilus capito Nees [Hymenoptera: Braconidae].

2 Samples of larvae were taken from fields with plots of white mustard, Sinapis alba L. and spring rape, Brassica napus L. in 1997 and 1998. Levels of parasitism and the survival and size of D. capito were measured to determine any influence of the host plant species. Survival and weights of pollen beetles from S. alba and B. napus were also measured.

3 Levels of parasitism between 8% and 29% were recorded. There was a significantly higher likelihood of being parasitized by D. capito for beetle larvae developing on S. alba than on B. napus. We argue that semiochemical or morphological properties of plant species could be responsible for differential parasitism by D. capito.

4 Neither survival of D. capito nor parasitoid size differed from hosts developing on S. alba or B. napus. Pollen beetle emergence was the same for both plant species, but beetles that developed on S. alba weighed less than those from B. napus. Results suggest that the partial resistance of S. alba to the pollen beetle will have no negative effects on the parasitoid D. capito.
Effect of plant patch shape on the distribution and abundance of three lepidopteran species associated with Brassica oleracea
Authors: Muriel Sandra B. , Grez Audrey A.
Published: March 2003

Plant patch shape may affect the abundance of herbivorous insects. Patches of the same size but longer or irregular have a higher perimeter/area relationship (P/A) than square or regular ones, which may determine the immigration, emigration and abundance of individuals in the patch.

 Only specialist species should be affected by plant patch shape. Those species that are more abundant in smaller patches should be more abundant in patches with higher P/A, whereas those that are more abundant in larger patches should be more abundant in patches with lower P/A.

 We studied the density of eggs, larvae and pupae of Pieris brassicae, Plutella xylostella and Trichoplusia ni in square (low P/A) and I‐shaped (high P/A) patches of 144 plants of Brassica oleracea. We also estimated their immigration to these patches, and the final plant weight.

 Plant patch shape affected the abundance, but not the distribution, of the two specialist species. Whereas P. brassicae was denser in I‐shaped patches, P. xylostella was more abundant in square patches. The generalist T. ni was not affected by patch shape. Immigration of P. brassicae was higher in I‐shaped patches, but immigration of P. xylostella and T. ni was not affected by patch shape. Plants were heavier in the centre of square patches.

 Our results suggest that plant patch shape affects the density of herbivorous insects and should be considered independently from other plant patch variables when studying the population dynamics of these organisms.
Soybean seed damage by different species of stink bugs
Authors: Corrêa‐Ferreira Beatriz S. , De Azevedo Joacir
Published: March 2003

Abstract

 Damage caused by the three main species of stink bugs occurring on soybean Nezara viridula (Linnaeus), Piezodorus guildinii (Westwood) and Euschistus heros (Fabricius) was compared in field cages and in greenhouses. Infestation levels of 4 stink bugs/m row of plants (field cages) and 2 stink bug/plant (greenhouse) for 15 days during the pod filling stage are reported. At harvest, the yield and seed quality were evaluated.

 In the field, there was no difference in yield between infested and insect‐free plants, but damage to seed quality varied with stink bug species. Plants damaged by P. guildinii had the lowest quality seeds. From 50 g seed samples harvested in the field, the mean weight of seeds classified as ‘good’ was 37.3 g in plants infested with P. guildinii, compared to 41.8, 44.2 and 46.6 g in plants infested with E. heros, N. viridula and the control, respectively.

 Plants infested with P. guildinii showed the highest number of seeds damaged by stink bugs, whereas those infested with E. heros showed the lowest damage.

 Plants infested with P. guildinii had 18.5% damaged seeds, higher than the 3.6% and 3.4% damaged seeds from plants infested with the two other species and 0.1% in control plants. The percentage of non‐viable seeds due to stink bug damage was 5.7% for P. guildinii but lower for the other two species.
Experimental field studies on predation and egg parasitism of rice brown planthopper in Indonesia
Authors: Claridge M. F. , Morgan J. C. , Steenkiste A. E. , Iman M. , Damyanti D.
Published: March 2003

Egg parasitism and general predation are known to be important mortality factors in the population dynamics of rice brown planthopper (BPH)Nilaparvata lugensin tropical Asia, but previous studies have not attempted to quantify and compare them.

 Field experiments in Java, Indonesia, are reported for 1993 and 1994. Plants previously infested with BPH eggs were put out in field cage‐enclosures, which, by means of different size mesh gauze covering, allowed either: (1) free access to all natural enemies, (2) access only to egg parasitoids, or (3) no access to any natural enemies.

 After one BPH generation (30 days), numbers of adults and gravid females were counted for each treatment. In addition, plants were dissected to determine the numbers of eggs laid.

 An additional treatment in which all natural enemies were excluded, but lycosid spiders were added, was used in 1994 experiments in an attempt to assess the effects of predators in the absence of egg parasitoids.

 Numbers of BPH adults and eggs laid were highest when natural enemies were excluded and lowest when they had free access. Mortality due to egg parasitoids in the absence of predators was intermediate and significantly different to the two other treatments.

 The effects of added predators in the absence of egg parasitoids gave variable results, but again clearly demonstrated the significance of egg parasitism in overall BPH mortality.

 The conservation of BPH egg parasitoids should form an important element of any rice pest management programme in tropical Asia.
Essential oil composition in leaves of carrot varieties and preference of specialist and generalist sucking insect herbivores
Authors: Kainulainen Pirjo , Nissinen Anne , Piirainen Anne , Tiilikkala Kari , Holopainen Jarmo K.
Published: March 2003

The carrot psyllid Trioza apicalis and Lygus rugulipennis can cause serious damage to cultivated carrots, especially at the seedling stage. The essential oil composition in leaves of several carrot varieties was studied in relation to oviposition acceptance by sucking insect herbivores that have different feeding strategies. Of the insect species studied, T. apicalis is a carrot specialist, T. anthrisci is an Apiaceae specialist, and L. rugulipennis is a generalist.

 The oil composition differed significantly between leaves from different carrot varieties (Flakkeer 2, Nantura, Parano, Napoli, Panther, Splendid, Nantes 3 Express).

 There were no differences in the mean numbers of eggs laid by T. apicalis or T. anthrisci on different varieties, but L. rugulipennis laid fewer eggs on the Panther variety than on Nantes 3 Express.

 There was a negative linear correlation between limonene concentration and number of eggs laid by T. apicalis, confirming that limonene is a repellent to the carrot psyllid. Results suggest that only particular compounds influence the preference of the carrot psyllid, and these compounds may not be the main components in the essential oil of carrots.

 A positive correlation was found between myrcene concentration and number of eggs laid by T. anthrisci. Essential oil composition did not explain egg‐laying preference of L. rugulipennis.

 The results indicate that essential oil composition of carrot varieties affects host preference of Apiaceae specialists more than that of generalists.
Effects of artificial shade on attack by the mahogany shoot borer, Hypsipyla robusta (Moore)
Authors: Mahroof R. M. , Hauxwell C. , Edirisinghe J. P. , Watt A. D. , Newton A. C.
Published: March 2003

Abstract

Swietenia macrophylla King (Meliaceae: Swietenioideae) provides one of the premier timbers of the world. The mahogany shoot borer Hypsipyla robusta Moore (Lepidoptera: Pyralidae) is an economically important pest of S. macrophylla throughout Asia, Africa and the Pacific. No viable method of controlling this pest is known. Previous observations have suggested that the presence of overhead shade may reduce attack by H. robusta, but this has not been investigated experimentally. This research was therefore designed to assess the influence of light availability on shoot‐borer attack on S. macrophylla, by establishing seedlings under three different artificial shade regimes, then using these seedlings to test oviposition preference of adult moths, neonate larval survival and growth and development of shoot borer larvae.

Oviposition preference of shoot borer moths was tested on leaves from seedlings grown under artificial shade for 63 weeks. A significant difference in choice was recorded between treatments, with 27.4 ± 1.5 eggs laid under high shade and 87.1 ± 1.8 under low shade.

Neonate larval survival on early flushing leaflets of S. macrophylla did not differ significantly between shade treatments. Larval growth rate, estimated by measuring daily frass width, was significantly higher for those larvae fed on seedlings from the high and medium shade treatments (0.1 mm/day), than the low shade treatment (0.06 mm/day). In laboratory‐reared larvae, the total mass of frass produced was significantly higher in the high shade treatment (0.4 g) than under the low shade treatment (0.2 g).

Longer tunnel lengths were bored by larvae in plants grown under high shade (12.0 ± 2.4 cm) than under low shade (7.07 ± 1.9 cm). However, pupal mass under low shade was 48% higher than that under the high shade treatment, suggesting that plants grown under high shade were of lower nutritional quality for shoot borer larvae.

These results indicate that shading of mahogany seedlings may reduce the incidence of shoot borer attack, by influencing both oviposition and larval development. The establishment of mahogany under suitable shade regimes may therefore provide a basis for controlling shoot borer attack using silvicultural approaches.
Calcium silicate enhances resistance of sugarcane to the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae)
Authors: Keeping M. G. , Meyer J. H.
Published: March 2003

Abstract

The stalk borer Eldana saccharina is the most destructive pest in sugarcane in South Africa. This study investigated: (1) the potential of applied silicon in enhancing plant resistance of sugarcane to E. saccharina, using calcium silicate as a carrier; (2) whether there was any interaction between cane variety (and stalk borer resistance) and silicon treatment.

Six commercial varieties of sugarcane were treated in a pot‐plant trial with two levels (5000 and 10 000 kg/ha) of calcium silicate. After artificial infestation with E. saccharina, response to the treatments was assessed in terms of borer numbers and mass, and stalk damage.

Calcium silicate significantly enhanced resistance at the higher rate compared with the control. Borer mass was reduced by 19.8% and stalk length bored by 24.4%. Lower treatment values were intermediate between those of the higher treatment and the control.

The interaction between variety and Si treatment was not significant when varieties were examined individually in the analysis. However, the interaction was significant for borer mass when varieties were grouped according to their resistance characteristics. Susceptible varieties might benefit more from treatment with silicon than resistant ones, as resistant varieties showed no significant effect of silicon.

All varieties had increased silicon content due to the treatments, but differed appreciably in stalk silicon content at the different treatment levels. Similarly, within varieties, stalk silicon content did not correspond consistently with borer response patterns and silicate application rates.
Behavioural responses of larvae of Colorado potato beetle,Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), to host plant volatile blends attractive to adults
Authors: Dickens Joseph C.
Published: March 2003

Abstract

Orientation of second‐ and fourth‐instar Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), to volatiles emitted from a solanaceous host, potato, and seven synthetic blends or three individual chemicals emitted by potato plants were investigated in laboratory bioassays.

Both second‐ and fourth‐instar CPB were attracted to intact and mechanically damaged (MD) potato foliage. When offered a choice between intact and MD foliage, no preference was observed.

Among seven synthetic blends tested (of which six are attractive to adult CPB), second‐ and fourth‐instar CPB were attracted only to a single three‐component blend comprising (±)‐linalool, methyl salicylate, and (Z)‐3‐hexenyl acetate. Individual compounds and two‐component blends were inactive. No significant difference was noted between larval responses to the attractive synthetic blend vs. MD potato foliage.

Second‐and fourth‐instar larvae had similar thresholds for behaviour for the three‐component blend (50 µg source load). Female CPB were attracted to source loads 10× below the larval threshold (5 µg). Male CPB were the most sensitive life form tested with a behavioural threshold at 0.5 µg source load which was 10× and 100× below female and larval thresholds, respectively

This is the first report of a synthetic chemical attractant for CPB larvae. As both larval and adult CPB are attracted to a single chemical blend, the usefulness of the attractant as a component of an attracticide or ‘push‐pull’ strategies for management of pestiferous populations is enhanced.
Colonization of vineyards by Kampimodromus aberrans (Oudemans) (Acari: Phytoseiidae): dispersal from surrounding plants as indicated by random amplified polymorphism DNA typing
Authors: Tixier Marie‐Stéphane , Kreiter Serge , Croft Brian A. , Auger Philippe
Published: March 2003

Abstract

Kampimodromus aberrans (Oudemans) is the most important predatory mite found in vineyards of southern France. This mite also occurs in surrounding uncultivated areas from where it disperses to colonize adjacent vineyards

To determine accurately origins of immigrant mites and to study their establishment in vineyards, a study using RAPD markers (Random Amplified Polymorphism DNA) was performed. Females of K. aberrans were sampled on leaves collected in an experimental vineyard, and from several adjacent areas including neighbouring vine plots and natural plants, both of which harboured high densities of the mite. Samples were taken in May and July before and after major dispersal of K. aberrans into the experimental plot occurred.

For both dates, genetic distances within population were lower than between populations and three groupings of mites were observed. Strong relationships were observed between (1) females from different parts of the same experimental vineyard (variety Cabernet‐Sauvignon), (2) females from several plants in the woody margin neighbouring this experimental plot, and (3) females from two neighbouring vineyards (variety Carignan). Populations seemed to be structured and no correlation between genetic and geographical distances was observed. Hence, definitive conclusions about origins of migrants were not possible.

Once in a vineyard, mites are probably exposed to selection pressures (i.e. pesticide applications or vine variety characteristics) that largely determine differentiation of populations. Thus, despite many immigrants moving into vineyards, our study indicated that there was limited survival or reproduction of immigrants. Further studies of within vineyard selection factors and impacts on immigrant mites are needed to determine the influence of natural colonization on grape pest management.
Impact of cocoon predation and parasitism on endemic populations of the common pine sawfly, Diprion pini (L.) (Hymenoptera, Diprionidae) in different forest types
Authors: Herz Annette , Heitland Werner
Published: March 2003

1 Predation and parasitism on litter‐buried cocoons of the common pine sawfly Diprion pini (L.) were compared in different forest types with endemic sawfly populations by field exposure of laboratory‐reared cocoons during three consecutive years (1993–1995).

2 The impact of cocoon predation was dependent on season and forest type. The highest predation (up to 95%) was found during autumn in forest stands with a dense understory vegetation.

3 Cocoon parasitism varied between year, season and forest type. The highest parasitoid attack was observed in pure pine forests with more or less barren soils, but did not exceed 24% of exposed cocoons.

4 Cocoons were exposed in small patches. Predators tended to exploit all cocoons of a patch, whereas parasitoids only attacked a few cocoons of a patch. Predation was similar on cocoons placed in the litter and those buried more deeply in the soil, whereas parasitism of soil‐buried cocoons was rare.

5 These results indicate that predators can have a remarkable potential for limiting endemic sawfly densities, if habitat conditions in a forest maintain their population and support their foraging behaviour. A notable effect of parasitoids on sawfly cocoons deposited in the litter is obviously restricted to typical pure and barren pine forests, but may play there a similar role as predation.
Diversity and abundance of the coleopteran fauna from organic and conventional management systems in southern England
Authors: Shah P. A. , Brooks D. R. , Ashby J. E. , Perry J. N. , Woiwod I. P.
Published: March 2003

1 Studies of the epigeal coleopteran fauna on five pairs of organic and conventional farms were carried out between May and July 1994 in southern England using pitfall trapping. A total of 27 749 individuals and 140 species were identified. Overall, abundance of Coleoptera was greatest on organically managed farms.

2 Ground beetles (Coleoptera: Carabidae) and staphylinid beetles (Col. Staphylinidae) formed 79.7% and 16.7%, respectively, of the total catch. Pterostichus melanarius was the dominant carabid among the 45 species captured and significantly higher numbers were found in organic farms. Tachinus signatus was the most common of 44 staphylinid species, and was significantly more abundant on conventional farms.

3 For carabids, the log‐series α diversity index was higher on conventional farms but was not statistically different from that calculated for organic farms. The α index was identical for staphylinid species from organic and conventional farms. Diversity was significantly higher from conventional farms when data were combined for all of the recorded coleopteran species.

4 From this study, it appears that the main effect of farming practice is to influence the overall abundance and dominance of particular species, and the lower diversity of organic farms is a consequence of the large increase in dominance of a single species, namely P. melanarius.
Meeting needs of disadvantaged families: parents’ views
Authors: Anderson E.S. , Lennox A. , Petersen S. , Wailoo M.P.
Published: March 2003

Parents from a deprived estate describe realizable solutions based upon a parent‐led service that would support mothers, and place their children within a safe caring environment. Parents emphasize the need for educative play in age‐appropriate mixed groups, to stimulate normal child development. Services established with parental consent and involvement provide the best opportunity for meeting the needs of deprived families.