Showing papers in "Agricultural and Forest Entomology in 2011"

Insect attraction to synthetic herbivore-induced plant volatile-treated field crops

Abstract: 1 Plants produce natural enemy-attracting semiochemicals known as herbivore-induced plant volatiles (HIPV) in response to herbivore damage. Deployment of synthetic HIPV in crops could enhance the biological control of pests. To test this, six HIPV [methyl salicylate (MeSA), methyl anthranilate (MeA), methyl jasmonate (MeJA), benzaldehyde (Be), cis-3-hexenyl acetate (HA), cis-hexen-1-ol (He)] in three concentrations (0.5%, 1.0% and 2.0% v/v) mixed with a vegetable oil adjuvant, Synertrol® (Organic Crop Protectants Pty Ltd, Australia), were sprayed onto winegrape, broccoli and sweet corn plants. 2 The relative abundance of insects within treated plots was assessed with non-attracting, transparent sticky traps at varying time intervals up to 22 days after spraying. 3 In the vineyard experiment, Trichogrammatidae responded to Be and MeA (0.5%) and Be (1.0%); Encyrtidae and Bethylidae responded to MeA (1.0%); Scelionidae responded to all compounds at 1.0% and 2.0%; and predatory insects responded to MeA. In sweet corn, parasitoids as a group and Encyrtidae responded to MeA (0.5%); Braconidae responded to all compounds at 0.5% and Synertrol-only; thrips responded to all compounds at 0.5% and 1.0%; while all parasitoids responded to all compounds at 0.5% and 1.0% and Synertrol-only. In broccoli, parasitoids as a group and Scelionidae responded to Be, HA, He and Synertrol-only; Trichogrammatidae responded to Be (0.5%), He (0.5% and 1.0%), MeJA (1.0%) and MeSA (0.5%); and thrips responded to all compounds at to 0.5% and 1.0%. 4 Significant attraction of insects occurred up to 6 days after the HIPV application, suggesting that plants may have been induced to produce endogenous volatiles that attracted insects over an extended period. 5 The results obtained are discussed in relation to the potential utility of synthetic HIPV to enhance the biological control of pests.

Spatio‐temporal patterns and interactions with honeydew‐producing Hemiptera of ants in a Mediterranean citrus orchard

Abstract: We are very grateful to N. J. Gotelli for providing statistical help and to Xim Cerda for his critical review and helpful comments. This work was supported by the project AGL2005-07155-C03-03 from the Ministerio de Educacion y Ciencia of Spain.

Local and landscape effects on bee communities of Hungarian winter cereal fields

Abstract: 1 Pollination is a key ecosystem service. Although bees are the most important pollinators, they are endangered by intensive agricultural practices. The present study investigated the effects of farmland management and environmental factors at local and landscape scales on bees in Central Hungary. 2 Bees were sampled in winter cereal fields that varied in the amount of applied fertilizer and insecticide use. Measurements included total, small and large bee species richness and abundance; stability of total species richness and abundance (coefficient of variation, CV); the nitrogen content of fertilizers; the number of insecticide applications; within-field location; species richness and abundance of insect-pollinated plants; and the percentage of semi-natural areas in a 500-m radius circle around the fields under study. 3 Increasing the amount of fertilizer decreased total and small bee abundance and increased the CV of total bee abundance. Insecticide use had a significant negative effect on total and small bee species richness and on large bee abundance. The percentage of semi-natural habitats in a 500-m radius did not influence bee species richness and abundance. 4 The results obtained confirms that the intensification of farmland management poses a threat to bee diversity, and thus may reduce pollination services. Recently-introduced agri-environment schemes are one potential approach for managing agricultural land use: reduced amounts of fertilizer and a cessation of insecticide application might lead to high bee species richness and abundance and ensure the pollination of wild plants and flowering crops.

Chemically mediated multitrophic interactions in a plant-insect vector-phytoplasma system compared with a partially nonvector species

Abstract: We elucidated the life cycles of two jumping plant lice species (Hemiptera: Psyllidae): Cacopsylla picta, a vector of the apple proliferation phytoplasma (Candidatus Phytoplasma mali), and Cacopsylla melanoneura, a nonvectoring species in Germany and some neighbouring countries, which may transmit the phytoplasma in one region in Italy. 2 The adults of C. picta reproduce exclusively on apple and migrate soon after emergence (emigrants) to conifers in mountainous regions, and return to apple plants in early spring (remigrants). Cacopsylla melanoneura also uses conifers as overwintering host plants but prefers to reproduce on hawthorn, despite its ability to reproduce on apple. 3 Both psyllid species used chemical cues for the identification of their alternate host plants during migration. Remigrants of C. melanoneura preferred the odour of their main reproduction host plant hawthorn to apple but preferred the odour of apple when experienced by feeding and oviposition. Although emigrants of C. picta report- edly prefer the odour of apple trees infected by Ca. P. mali, the remigrants of both species did not distinguish between the odours of infected or uninfected apple plants. 4 Investigating the distribution of Ca. P. mali in plant species involved in psyllid life cycle revealed that the phytoplasma is specialized on apple. 5 Infection of apple by Ca. P. mali increased mortality and resulted in decreased body size of C. picta offspring. 6 Gravid females of C. picta preferred to oviposit on non-infected plants. 7 It is concluded that Ca. P. mali indirectly promotes its acquisition from infected plants and transmission to non-infected plants by behavioural manipulation of its vector C. picta.

Facilitation in bark beetles: endemic mountain pine beetle gets a helping hand

Abstract: 1 Endemic populations of the bark beetle Dendroctonus ponderosae attack weakened lodgepole pine (Pinus contorta var. latifolia) trees that are often previously infested by other bark beetle species, such as Pseudips mexicanus. 2 The effect of interactions on D. ponderosae was assessed by examining host selection and productivity of D. ponderosae in trees containing P. mexicanus and trees infested solely by D. ponderosae. 3 The findings obtained show that D. ponderosae attacked hosts previously occupied by P. mexicanus at greater densities, and offspring emerged earlier compared with hosts infested by D. ponderosae alone. Additionally, D. ponderosae larvae in P. mexicanus-infested trees were found to require a significantly lower amount of resource to complete development with no loss in size. 4 The presence of P. mexicanus may affect host condition, improving the subcortical environment for endemic D. ponderosae, ultimately aiding in population maintenance at low levels. Hosts in this state should be preferentially attacked by D. ponderosae.

Potential negative effects of exotic honey bees on the diversity of native pollinators and yield of highland coffee plantations

Abstract: 1The honey bee Apis mellifera is native to Eurasia and Africa, although it is commonly introduced into crop fields of different parts of the world because of the assumption that it improves yield. This bee is, however, a poor pollinator of several crops compared with native insects. Indeed, honey bees can displace native pollinators and reduce their diversity. The present study evaluated the potential impacts of A. mellifera on the diversity of native pollinators of highland coffee (Coffea arabica) and its putative consequences for coffee production at the state of Veracruz, Mexico. 2The abundance of A. mellifera and diversity of native pollinators were assessed during blooming at 12 shade coffee plantations and pollination experiments were conducted to determine the impacts of pollinators on coffee fruit production. Regression analyses were used to assess whether the abundance of honey bees was related to native pollinator diversity, and whether fruit production was influenced by both the diversity of pollinators and the abundance of A. mellifera. 3Native pollinator diversity decreased as the number of honey bees increased. Furthermore, although coffee fruit production was positively related to the diversity of native pollinators, an increasing abundance of A. mellifera was correlated with a decrease in fruit production. 4Highland shade coffee plantations are considered as reservoirs of the Mexican insect fauna. Thus, native pollinator diversity could be better preserved if beekeepers reduced the number of managed hives that they brought into plantations. This may also help to increase coffee yield by decreasing the putative negative effects of A. mellifera on native pollinators.

Assessment of the range of attraction of pheromone traps to Agriotes lineatus and Agriotes obscurus

Abstract: 1 The range of attraction of YATLOR pheromone traps was studied to gain information on the number of traps needed for mass trapping of males of two Agriotes species. 2 Male click beetles of the species Agriotes lineatus (L.) and Agriotes obscurus (L.) (25–30 individuals per release point) were marked and released at a distance of 2, 5, 10, 15, 20 and 60 m from a pheromone trap both along and opposite to the known prevailing wind direction. Traps were regularly inspected over approximately 1 month. The percentage of recaptured beetles was calculated and analyzed using analysis of variance. Maximum sampling ranges and effective sampling areas were calculated. 3 Averaged over all five trials and distances, approximately 40% of the released beetles (A. lineatus and A. obscurus) were recaptured. The percentage recapture of male adults was significantly affected by release distance, whereas no differences were found for species and release direction. 4 Males were recaptured from all release points and the percentage recapture decreased (in part significantly) with increasing distance from 76% (2 m) to 35% (15 m) and 9% (60 m), respectively. Most of the beetles were recaptured within the first 3 days after release, independent of the distance, except 60 m. The effective sampling area for A. lineatus was 1089 m2 after 12 days and increased to 1735 m2 after 30 days. Corresponding values for A. obscurus were considerably higher: 1518 m2 for 12 days and 2633 m2 for 30 days. 5 We conclude that the range of attraction of the pheromone traps for A. lineatus and A. obscurus is comparatively low, providing high percentage recapture only for release distances up to 10 m. Accordingly, any approach targeted on preventing mating by male mass trapping would require a dense network of pheromone traps.

Parasitoids aid dispersal of a nonpersistently transmitted plant virus by disturbing the aphid vector

Abstract: 1 Aphids are the major group of insects that vector plant viruses, and they often display a preference for foliage showing disease symptoms. Although this behaviour will increase the numbers of vectors acquiring the pathogen, it will not in itself result in a greater spread of the disease. 2 The present study examined how infection of Vicia faba by the nonpersistently transmitted virus bean yellow mosaic virus (BYMV) affected colonization by pea aphids Acyrthosiphon pisum. We then examined how foraging by the hymenopterous parasitoid Aphidius ervi affected aphid settling/movement behaviour and the consequences for dissemination of the virus. 3 In Petri dish arenas, aphids colonized discs from BYMV-infected leaves more rapidly than discs from uninfected plants. Reflectance from infected foliage was approximately 20% higher than from uninfected leaves in the green–yellow wavelengths, indicating that aphids might be responding to visual cues from the brighter foliage. Settling was reduced by A. ervi, with the foraging wasps preventing the aphids reaching and/or remaining on the leaf tissue. 4 In multiple plant arenas, A. ervi caused a reduction in aphid numbers but also a nine-fold increase in BYMV infection. It is hypothesized that disturbance by the parasitoids resulted in more aphid movement as well as more cases of aphids probing on a BYMV-infected plant and then a new host within the critical time period for successful inoculation to occur. This effect of parasitoids on virus dispersal should be considered in epidemiological models of insect-vectored plant diseases, and also when evaluating the use of natural enemies in biocontrol strategies of insect herbivore/vector pests.

Edge effects on ground beetles at the woodlot–field interface are short-range and asymmetrical

Abstract: Boundaries between woodlots and agricultural habitats are numerous in temperate agricultural landscapes and influence ecological processes in both woodlots and agricultural habitats. 2 We aimed to determine how far the species assemblage of ground beetles in woodlot and open habitats was influenced by the presence of the woodlot-field boundary. 3 We studied the distribution of ground beetles on both sides of the boundaries of four woodlots along transects of pitfall traps (n = 140). The depth of edge influence (i.e. the distance from the boundary at which the presence of the boundary has no more significant influence) on the species assemblage of ground beetles in each woodlot and in each agricultural habitat was determined with nonlinear canonical analysis of principal coordinates, an ordination method that is followed by nonlinear regression of the principal coordinates on distance from the boundary. 4 The depth of edge influence on the species assemblages of ground beetles was asymmetrical relative to the boundary: it was generally higher and had higher variability in open habitats (14.4 ± 12.3 m) than in woodlots (4.9 ± 2.3 m). Species assemblages of ground beetles in edges were a mix between both adjacent species assemblages. Edge effects in woodlots were deeper in the woodlots exhibiting a deeper penetration of open habitat species. Symmetrically, edge effects in open habitat were deeper in the open habitats with a deeper diffusion of forest species into the open habitat. 5 Forest ground beetles were not threatened by edge effects. Rather, edge effects are likely to benefit agriculture, mostly through the dispersal of predatory forest species into agricultural fields.

Arthropod food webs in organic and conventional wheat farming systems of an agricultural long-term experiment: a stable isotope approach

Abstract: 1 Agricultural intensification not only alters the structure of arthropod communities, but also may affect biotic interactions by altering the availability of basal resources. We analyzed variations in stable isotope ratios (15N/14N and 13C/12C) of fertilizers, plants, prey and generalist predators in organic and conventional farming systems in a long-term agricultural experiment [DOK trial (bioDynamic, bioOrganic, Konventionell)]. Two basal resources with pronounced differences in carbon isotope signatures, wheat litter (C3 plant) and maize litter (C4 plant), were used to uncover differences in food web properties between the two farming systems (conventional versus organic). 2 Predators incorporated significantly higher proportions of carbon from wheat sources in organically managed fields, suggesting that they were more closely linked to wheat-consuming prey in this system. The δ15N values of three predaceous species were more than 2‰ greater in summer than in spring. 3 The results obtained suggest that generalist predators consumed higher proportions of herbivore prey in the organic system and that starvation and intraguild predation rates increased in some predator species with time. 4 Because the effects of farming system and sampling date on predators were species-specific, conserving a diverse natural enemy community including species with different phenologies and sensitivities to management practices may, in the long term, be a good strategy for maintaining high pest suppression throughout the growing season.

High temperature tolerance and thermal plasticity in emerald ash borer Agrilus planipennis.

Abstract: The emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) (EAB), an invasive wood-boring beetle, has recently caused significant losses of native ash (Fraxinus spp.) trees in North America. Movement of wood products has facilitated EAB spread, and heat sanitation of wooden materials according to International Standards for Phytosanitary Measures No. 15 (ISPM 15) is used to prevent this. 2 In the present study, we assessed the thermal conditions experienced during a typical heat-treatment at a facility using protocols for pallet wood treatment under policy PI-07, as implemented in Canada. The basal high temperature tolerance of EAB larvae and pupae was determined, and the observed heating rates were used to investigate whether the heat shock response and expression of heat shock proteins occurred in fourth-instar larvae. 3 The temperature regime during heat treatment greatly exceeded the ISPM 15 requirements of 56 ◦ C for 30 min. Emerald ash borer larvae were highly tolerant of elevated temperatures, with some instars surviving exposure to 53 ◦ C without any heat pre-treatments. High temperature survival was increased by either slow warming or pre-exposure to elevated temperatures and a recovery regime that was accompanied by up-regulated hsp70 expression under some of these conditions. 4 Because EAB is highly heat tolerant and exhibits a fully functional heat shock response, we conclude that greater survival than measured in vitro is possible under industry treatment conditions (with the larvae still embedded in the wood). We propose that the phenotypic plasticity of EAB may lead to high temperature tolerance very close to conditions experienced in an ISPM 15 standard treatment.

Arthropod pests of currant and gooseberry crops in the U.K.: their biology, management and future prospects

Abstract: Approximately 10-12 species of Ribes plants are cultivated for fruit production, mainly blackcurrants, red- and whitecurrants and gooseberries. These crops are increasingly recognized as rich sources of vitamin C and anthocyanins, with production rising by 24% in Europe subsequent to 1998. To date, research into insect pests of Ribes has been fragmented, with little appreciation of how changes in climate and agronomic practices affect biology. 2 We review 12 key pests of currant and gooseberry crops in Northern Europe, with specific emphasis on their biology and current management options. These are blackcurrant leaf curling midge Dasineura tetensi, blackcurrant sawfly Nematus olfaciens, common gooseberry sawfly Nematus ribesii, European permanent currant aphid Aphis schneideri, redcurrant blister aphid Cryptomyzus ribis, currant-sowthistle aphid Hyperomyzus lactucae, European gooseberry aphid Aphis grossulariae, woolly vine scale Pulvinaria vitis, common green capsid Lygocoris pabulinus, winter moth Operophtera brumata, clear wing moth Synanthedon tipuliformis and blackcurrant gall mite Cecidophyopsis ribis. 3 It is anticipated that global climate change could lead to increases in the incidence of some aphids through increased overwintering survival and longer seasonal activity. Moreover, changes in management practices such as increased cropping densities (from 5400 ha −1 to 8700 ha −1 ) and machine harvesting could lead to pest outbreaks

Enhancing rape pollen beetle parasitism within sown flower fields along a landscape complexity gradient

Abstract: 1 Sown flower habitats not only are employed in agri-environment schemes in the European Union to enhance pollinators and birds, such as partridges, but also are hypothesized to contribute to the biological control of pests such as the rape pollen beetle Meligethes aeneus Fabr. by improving habitat and resource availability for its specialized parasitoids. 2 In the present study, we selected 20 sown flower fields that included one of the pollen beetles' host plants Sinapis alba L., each centred in a landscape of varying complexity, to test the influence of the surrounding landscape structure on parasitism rate and herbivory by M. aeneus. Additionally, plant cover of S. alba plants within the sown flower fields and numbers of S. alba flowers were also included in the analyses. 3 Landscapes with high proportions of semi-natural habitats supported higher parasitism rates, and sown flower fields with dense S. alba plant cover hosted more parasitoids and suffered from less herbivory. 4 We conclude that sown flower fields are not only important for pollinators and birds, but also are long-term undisturbed, unploughed, insecticide-free habitats with rich food (nectar/pollen) and host resources for parasitoids, contributing to the build-up and maintenance of large parasitoid populations, which are important biocontrol agents of rape pollen beetles.

Optimizing biocontrol using phenological day degree models: the European earwig in pipfruit orchards

Abstract: 1 Phenological day degree models are often used as warning systems for the emergence of arthropod pests in agricultural crops or the occurrence of natural enemies of the pest species. In the present study, we report on a case study of the European earwig Forficula auricularia L., which is an important natural enemy in pipfruit orchards, and describe how such a day degree model can be used to avoid negative effects of crucial orchard management, such as spray applications and soil tillage. A precise timing of these interventions in relation to the phenology of natural enemies will enhance biocontrol. 2 Earwig population dynamics are characterized by single- and double-brood populations, each with specific biological characteristics. 3 A day degree model capable of predicting the phenology of local earwig populations of both population types was developed. The model was checked for accuracy by comparing the first field observation dates of various life stages with predicted values using temperature data from the nearest weather station. In addition, variation in development time was assessed using field data. 4 The model was able to make predictions on a global scale. Although single- and double-brood populations differ in phenology, the predictions of first appearance dates were similar. Variation in development time showed that single-brood populations were more synchronized. 5 Our phenological model provides an accurate tool for predicting and simulating earwig population dynamics, as well as for enhancing the biocontrol of pests in pipfruit orchards.

The constraints of selecting for insect resistance in plantation trees

Abstract: High productivity in plantations of exotic tree species is achieved by management for fast growth in the absence of the full complex of co-evolved insect herbivores. In the case of Eucalyptus, silvicultural selection for desirable wood traits is concomitant with a trade-off against defence and a reduction of chemical and genetic diversity. These factors, combined with accidental introductions, rapid insect evolution and the emergence of new pests, increase the likelihood that future plantations will need insect pest management to maintain productivity. 2 Forestry researchers have suggested that selecting for resistant genotypes may be beneficial in insect control. There are, however, significant differences between long-lived trees and annual crops that make this approach unlikely to be successful. This is illustrated using several examples of research into resistance to insect herbivores in trees. 3 Selection for resistance to insects in trees requires an assessment of trial plantations for heritable variation in insect damage and then a determination of the effect of variation in resistance on insect population parameters. Identifying rare resistant genotypes using markers is difficult because many factors interact to produce a resistant phenotype, and phytophagous insects have less intimate relationships with their host than pathogens, resulting in weak associations with genetic loci. 4 If resistant genotypes are identified, their widespread deployment in plantations might not provide satisfactory management of insect pests when the use of extensive monocultures is continued. In this paper, experiments are suggested that would explore the effectiveness of polycultures or chemotype mixtures with respect to ameliorating the damage of insects on plantation productivity. In addition, mitigating the effects of some insects on plantation productivity by maintaining vigour of fast-growing eucalypts should be considered.

Impact of climatic variation on populations of pine processionary moth Thaumetopoea pityocampa in a core area of its distribution

Abstract: There is growing appreciation of climatic effects on insect population dynamics at the margins of distribution limits. Climatic effects might be less important and/or involve different drivers and processes near the centre of distributions. 2 We evaluated the effects of interannual variation in temperatures, radiation and precipitation on populations of pine processionary moth Thaumetopoea pityocampa in Central-South Portugal, a low altitude area with a relatively mild Mediterranean climate near the centre of the north-south range of the species. 3 We tested for effects of climate on mortality of young larvae, growth rates, final larval mass and fecundity. 4 Results indicated high mortality of early instars associated with low minimum and maximum daily temperatures and low precipitation. Low minimum temperatures were further associated with high parasitism by the larval parasitoid Phryxe caudata (Rondani) (Diptera, Tachinidae). Furthermore, larval growth rates were higher with high solar radiation during December and January, which was itself negatively related to precipitation and air temperature. Slow larval growth rates led to lower final mass at pupation in the spring, and smaller egg masses and smaller initial colony sizes during the next autumn. 5 Thus climatic factors, and temperature in particular, apparently contributed to population dynamics of T. pityocampa in the core of its distribution, as well as at its northern limits. The most specific climatic parameters of importance, however, and the connections between climate, physiology and insect demographics in the core area were clearly different from northern areas.

The effect of weaver ants Oecophylla smaragdina on the shoot borer Hypsipyla robusta on African mahoganies in Australia

Abstract: 1 African mahogany Khaya senegalensis is a high-value timber tree species widely grown in central Africa, south-east Asia and northern Australia. Pilot plantings show that the tree grows well in the wet-dry tropical areas of northern Australia, and the shoot borer Hypsipyla robusta (Lepidoptera: Pyralidae) is a potential pest of the tree. The weaver ant Oecophylla smaragdina is an efficient biocontrol agent in some horticulture crops. To investigate whether the ants control shoot borers, field experiments were conducted at two sites near Darwin, Australia from April 2006 to January 2009. 2 In the weaver ant treatments, the overall percentage of trees damaged by shoot borers was 0–2.7% at Berrimah Farm and 0–4.2% at Howard Springs, and the damaged trees were attacked once only. In the treatments without weaver ants, however, 9.9–52.1% trees were damaged at Berrimah Farm, and 6.3–64.6% at Howard Springs, and the damaged trees were generally attacked more than once. 3 At both sites, significantly fewer trees on each monitoring occasion were damaged in weaver ant treatments than in treatments without weaver ants. 4 The mean percentage of overall flushing shoots damaged by the pest at both sites was significantly lower in weaver ant treatments compared with treatments without weaver ants. 5 Fewer shoots were damaged per damaged tree in weaver ant treatments compared with treatments without weaver ants. 6 The data obtained suggest that weaver ants were effective biological control agents of the shoot borer, and that the ants can be used to manage the pest on African mahogany trees.

Effects of tree age and stand thinning related variations in balsam fir secondary compounds on spruce budworm Choristoneura fumiferana development, growth and food utilization

Abstract: 1 The effect of tannins and monoterpenes on the development, mortality and food utilization of spruce budworm Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae) was investigated under laboratory conditions using an artificial diet. Tannins were extracted from balsam fir foliage of thinned and unthinned stands to reproduce stand thinning related variations in tannins. A mixture of synthetic monoterpenes was utilized to simulate the concentration found in young and old balsam fir trees. 2 Longer development time and lower pupal weight were observed for insects fed on diets with a lower nitrogen concentration and a higher tannin concentration (unthinned treatment). Tannins induced higher insect mortality at a low nitrogen concentration compared with the diet with a higher nitrogen concentration. 3 Approximate digestibility was higher for larvae fed on diets with high concentrations of nitrogen at both low and high concentrations of tannins. Efficiency of conversion of digested food (ECD) decreased with an increase in tannin concentration. Tannins reduced both the relative consumption and growth rate (RCR and RGR). 4 Monoterpenes increased spruce budworm mortality and this mortality reached almost 50% under concentrations of monoterpene typical of the young trees compared with 20% under monoterpene concentrations found in old trees. 5 A higher digestibility was observed for larvae fed on diet with a higher concentration of monoterpenes, whereas efficiency of conversion of ingested food (ECI), ECD, RCR, and RGR decreased with an increase in monoterpenes in the diet. 6 The results obtained in the present study are consistent with the defensive role of secondary compounds such as tannins and monoterpenes in the spruce budworm–balsam fir system.

Arthropod diversity and community composition on wild and cultivated rice

Abstract: 1 Most crop plants are grown far from their region of origin and have been significantly altered by human selection. Given the importance of biodiversity in ecosystem function, surprisingly little is known about the effect of domestication on arthropod diversity and community composition. 2 Arthropod diversity and species abundance were compared with three genotypes of cultivated rice Oryza sativa L. and two genotypes of wild rice O. rufipogon Griff. in southern Luzon, the Philippines. 3 Domestication had a small but positive effect on total arthropod diversity. Arthropod species richness was highest on the cultivar IR64 and lowest on one of the O. rufipogon genotypes, although arthropod community composition was similar across rice genotypes. 4 Total arthropod abundance and the relative abundance of guilds did not differ between wild and cultivated rice. All common herbivores, however, responded to rice domestication. Stem-boring moths and several sap-sucking herbivores benefited from domestication, although domestication reduced densities of the wolf spider Pardosa pseudoannulata Boesenberg et Strand. 5 By contrast to previous assumptions, crop domestication may not always decrease arthropod diversity. We did not detect any changes in biodiversity or community composition suggesting that rice domestication has altered the capacity of the arthropod community to regulate herbivores.

Wood-boring insect abundance in fire-injured ponderosa pine

Abstract: Wood-boring larvae in the families Cerambycidae and Buprestidae are often found in high densities in burned trees after wildland fires. They play an important role in tree decomposition, often reducing the value of salvageable timber, and represent an important avian food source.

Variation in the ability of larvae of phytophagous insects to develop on evolutionarily unfamiliar plants: a study with gypsy moth Lymantria dispar and Eucalyptus

Abstract: 1 By examining variation in the abilities of polyphagous insects to develop on host plants with secondary metabolites that they have never encountered previously, we may be able to gain some insights into the nature of evolution of biochemical mechanisms to process plant secondary metabolites by phytophagous insects. 2 The present study aimed to examine variation in the ability of gypsy moth larvae Lymantria dispar (Lymantriidae) to complete development on different species of the plant genus Eucalyptus (Myrtaceae). Leaves of at least some Eucalyptus species contain formylated phloroglucinol derivatives. These are secondary metabolites that are evolutionarily unfamiliar to the gypsy moth. 3 Larvae of gypsy moth showed extremely variable responses in larval performance between Eucalyptus species, between individual trees within host plant species, between moth populations, and between individuals within moth populations. 4 Larval survivorship was in the range 0–94%, depending on the host. Failure of at least some larvae to complete development on some Eucalyptus species indicates that gypsy moth larvae have a limited ability to process secondary metabolites in eucalypt leaves. 5 At least some individuals, however, appear to already possess biochemical mechanisms that process the secondary metabolites in leaves of Eucalyptus species, and therefore the abilities of larvae to complete development on phylogenetically and chemically unfamiliar hosts are already present before the gypsy moth encounters these potential hosts.

Pine weevil damage to Norway spruce seedlings: effects of nutrient‐loading, soil inversion and physical protection during seedling establishment

Abstract: 1 The pine weevil Hylobius abietis (L.) feeds on the bark of young conifer seedlings and is one of the most economically important forest pests in Europe. 2 In a field experiment, we examined the combined effects of the treatments: nutrient-loading of seedlings, planting in scarified plots and protection of seedlings against pine weevil damage for either half a season or a full season. 3 Nutrient loading had no significant effect on the amount of pine weevil feeding. 4 Seedling mortality was significantly reduced when seedlings were protected from pine weevil feeding during establishment. This occurred even though the debarked area of protected seedlings 5 weeks after the shields had been removed was similar to that of the unprotected seedlings. This indicates that initial protection rendered the seedlings more tolerant to later wounding by pine weevil. 5 Planting in soil inversion significantly reduced feeding compared with planting in humus. 6 We conclude that nutrient-loading of seedlings in the autumn before planting would not increase pine weevil feeding after planting. Mortality could be reduced by treatments that postpone the start of pine weevil feeding on seedlings. Such treatments, combined with planting in soil inversion, would result in increased seedling growth, vitality and tolerance to pine weevil attack.

Autumnal emergence of Anagrus wasps, egg parasitoids of Empoasca vitis, from grapevine leaves and their migration towards brambles

Abstract: 1 The Anagrus‘atomus’ parasitoid group (Hymenoptera: Mymaridae), associated with Empoasca vitis (Gothe) (Homoptera: Cicadellidae), overwinters on vegetation surrounding vineyards. The emergence of parasitoid adults from grapevine leaves in autumn was studied in north-eastern Italy, both in relation to the E. vitis egg-laying period and to the presence of leafhoppers overwintering as eggs on Rubus bushes. 2 Autumnal peaks of Anagrus captured using yellow sticky traps were observed first on grapevines and then on brambles. Parasitoid captures in vineyards were observed for more than 1 month after the last first-instar nymphs of the grape leafhoppers were noticed. Two species belonging to the A. ‘atomus’ group, Anagrus atomus and Anagrus ustulatus, were captured both on grapevines and brambles. 3 Parasitoids of the A.‘atomus’ group can emerge from third-generation grape leafhopper eggs in accordance with two different development time patterns (i.e. normal or delayed). Individuals with delayed emergence required up to 2.2-fold more time to develop from an egg to adult than individuals with normal emergence. This meant that some parasitoid adults emerged in autumn from eggs of grape leafhopper laid in August. 4 A delayed emergence as a result of a slower development ensures that the A.‘atomus’ parasitoid group is synchronized with the egg-laying of leafhoppers that overwinter as eggs on Rubus spp. 5 Consequently, leafhoppers overwintering as eggs on brambles play a key role in the ecology of the relationship between grape leafhoppers and the A.‘atomus’ parasitoid group.

Testing the suitability of insect orders as indicators for olive farming systems

Abstract: 8 paginas, 2 figuras, 3 tablas.-- El documento en word es la version pre-print del articulo.

Possible use of synthetic aggregation pheromones to control stinkbug Plautia stali in kaki persimmon orchards

Abstract: 1 The brown-winged green stinkbug Plautia stali Scott (Hemiptera: Pentatomidae) is the most serious pest of all noxious stinkbugs in various orchards in Japan. An area-wide integrated pest management programme using the species-specific aggregation pheromone is desirable to control P. stali because nonspecific insecticides may kill arthropod natural enemies and induce the resurgence of other endemic pests. 2 The traditional mass-trapping method is not expected to be effective as a result of huge migrations from cypress forests. Therefore, we chose an ‘attract-and-kill’ strategy of intensively installing poisonous eggplants with a synthetic aggregation pheromone lure as enclosures for the target orchards. 3 We found no overall control effect of the installation of poisonous eggplants, although regional differences were observed, which might originate from topological configurations or the distance from the source population in cypress forests. 4 The poisonous eggplants with an aggregation-pheromone lure, however, changed the spatial distribution of fruit damage, appearing to induce the majority of the damage within a 100-m range of the poisonous eggplants. Some damage, although at a low level, was found in regions 100–200 m away from the poisonous eggplants. 5 We postulate that such low-damage regions were created because the majority of the bugs dispersed from the centre of the orchards to the areas with poisonous eggplants. The present study, in which the spatial scale of the damage spillover was estimated at approximately 150 m, has important implications for future strategies of attract-and-kill and possibly push–pull.

Potential impact of the leaf‐cutting ant Acromyrmex lobicornis on conifer plantations in northern Patagonia, Argentina

Abstract: 1 The economic losses associated with crop damage by invasive pests can be minimized by recognizing their potential impact before they spread into new areas or crops. 2 We experimentally evaluated the preferences of the leaf-cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae) for the most common conifer species commercially planted in northern Patagonia, Argentina. The areas of potential forest interest in this region and the geographical range of this ant overlap. We performed field preference tests and monitored the level of ant herbivory on planted conifer seedlings next to nests. 3 Acromyrmex lobicornis preferred some conifer species and avoided foraging on others. Pseudotsuga menziesii and Austrocedrus chilensis were the less preferred species, Pinus ponderosa and Pinus contorta were the most preferred by A. lobicornis. 4 The item mostly selected by ants was young needles from P. contorta. This species was also the pine mostly defoliated. Seedlings without ant-exclusion showed a mean±SE of 60±5% defoliation during the sampling period. Pinus ponderosa was less defoliated; control seedlings showed a mean±SE of 8.5±1% of leaf damage in the sampling period. 5 The present study shows how the use of simple field tests of leaf-cutting ant preferences could allow an improved selection of appropriate conifer species for future plantations in areas where leaf-cutting ants are present.

Sources of variation in the incidence of ant–aphid mutualism in boreal forests

Abstract: 1 The mutualism between wood ants of the Formica rufa group and aphids living in the canopy of trees is a widespread phenomenon in boreal forests, and it can affect tree growth. However, not all trees in the forest are involved in this interaction. 2 To assess the incidence of host trees involved in this ant–aphid mutualism and its spatial distribution in boreal forests, we inventoried sample plots with a radius of 10–15 m around wood ant mounds in 12 forest stands of two age classes (5–12-year-old sapling stands and 30–45-year-old pole stands) and two dominant tree species (Scots pine and silver birch) in Eastern Finland from 2007 to 2009. 3 The proportion of trees visited by ants out of all trees on the individual study plots were in the range 4–62%, and 1.5–39% of the trees on the plots were consistently visited by ants during all 3 years. The percentage of host trees increased with the ant mound base area on the plots. Trees visited by ants were larger and closer to the mound than trees not visited by ants. Within the group of visited trees, more ants were found on bigger trees and on trees close to the ant mounds. 4 Extrapolated from plot to stand level, we estimated that 0.5–6.6% of the trees were host trees in at least one of the three study years, and that only 0.01–2.3% of all the trees were consistently visited by ants during all 3 years. It is concluded that ant–aphid mutualism is a minor occurrence at the stand level.

Factors that affect compartmentalization and wound closure of Quercus rubra infested with Enaphalodes rufulus

Abstract: The mechanisms by which hardwood trees resist invasion by native wood borers are still poorly understood. 2 We examined the importance of several host, herbivore and environmental variables in relation to Quercus rubra L., northern red oak, resistance to a native cerambycid, Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae), the red oak borer. 3 We employed tree-ring techniques to date and measure two indicators of host tree physical resistance, vertical lesion size and wound closure of scars left by larval galleries, within 107 Q. rubra hosts from eight sites within the Ozark and Ouachita National Forests of Arkansas. 4H ostQ. rubra decline status proved a valuable predictor of resistance, wherein healthy trees exhibited better compartmentalization capacity, as indicated by shorter lesions and faster wound closure, than declining trees and those that died during a recent E. rufulus outbreak. 5 Only healthy Q. rubra exhibited a significant declining lesion length trend from 1988 to 2006 and were likely able to re-allocate resources in favour of maintaining resistance as the feeding pressure from borers increased and then relaxed post- outbreak. 6 Variables related to borer feeding pressure consistently explained more variation in lesion length than host or environmental variables. Hosts were better able to compartmentalize injury from small, unsuccessful E. rufulus galleries than large, successful galleries from which larvae survived to adulthood. 7 Healthy Q. rubra, as survivors of the recent outbreak, were able to effectively tolerate feeding pressure from borers at the same time as sustaining growth and maintenance. Tolerance may be an important resistance mechanism for hardwood hosts against the native wood borers that attack them.

Ingestion and excretion of nitrogen by larvae of a cabbage armyworm: the effects of fertilizer application

Abstract: Insect frass has significant impacts on decomposition and soil nitrogen dynamics. Although the frass contains various forms of nitrogen that may differently influence nitrogen dynamics in the decomposition process, how the nitrogen form in the insect frass is influenced by host plant quality remains poorly understood. 2 The present study examined the effects of application of fertilizer on leaf quality of Brassica rapa L. var. perviridis Bailey (Brassicaceae), and on the consumption, frass excretion and frass quality of its insect pest Mamestra brassicae (L.) (Lepidoptera: Noctuidae), with a particular focus on the dynamics of inorganic nitrogen. 3 Brassica rapa increased total nitrogen concentration, and accumulated inorganic nitrogen (i.e. leaf nitrate-nitrogen (NO3 − -N) and ammonium-nitrogen (NH4 + -N)) in the leaves in response to the application of fertilizer. 4 Although leaf consumption and frass excreted by M. brassicae was not affected by fertilizer treatment, frass quality was influenced by host plant quality as altered by fertilizer applications. Frass contained high concentrations of total nitrogen, NO3 − -N, and NH4 + -N under high fertilizer treatment. In particular, the larvae excreted much more NH4 + -N than ingested. The relationship between host plant quality and insect frass quality, as well as the potential implications for decomposition and nutrient dynamics, are discussed.

Delayed mating and reproduction in the autumn gum moth Mnesampela privata

Abstract: 1 The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delaying mating in the target insect. Using the geometrid pest of Eucalyptus plantations, Mnesampela privata (Guen´ee), we determined the effect of delaying mating when imposed on males only, females only or on both sexes simultaneously, for 1, 3, 5 and 7 days. 2 Delayed mating had a significant negative impact on reproduction, with a 0.89-fold decrease in the likelihood of mating and a 0.67-fold decrease in the likelihood of that mating resulting in fertile eggs for every day that mating is delayed. A mating delay of 7 days reduced the mean number of viable eggs laid to 4–13% of that laid by moths paired immediately after emergence. 3 Male only imposed mating delays had a significantly lower effect on reducing the likelihood of pairs mating than when both sexes were delayed. A delay imposed on one sex only or on both sexes simultaneously, however, had a similar negative impact on the proportion of fertile matings as well as on the total number of fertile eggs laid. 4 Longevity of mated female and male M. privata was significantly different between mating delay treatments, with a significant decline in female longevity when they mated with older males. 5 The underlying mechanisms causing a decline in female reproductive output when a mating delay was imposed on males versus females are discussed in relation to the reproductive biology of M. privata and the potential of using mating disruption strategies to control populations in Eucalyptus plantations.