Showing papers in "Agricultural and Forest Entomology in 2009"

Ecology and management of exotic and endemic Asian longhorned beetle Anoplophora glabripennis

Abstract: 1 The Asian longhorned beetle is native to China and Korea, and was found for the first time outside its native habitat in the U.S.A. in 1996, with subsequent detections being made in Canada and several European countries. 2 We review the taxonomy, distribution, basic biology, behaviour, ecology and management of endemic and exotic Anoplophora glabripennis, including information that is available in the extensive Chinese literature. 3 This species has caused massive mortality of Populus species in China and models have demonstrated that it could become established in many locations worldwide. 4 Anoplophora glabripennis is polyphagous but prefers Acer, Salix and Populus, section Aigeiros. 5 Although A. glabripennis adults do not disperse far when surrounded by host trees, they have the potential to fly more than 2000 m in a season. 6 Volatile organic compounds from preferred host trees are attractive to A. glabripennis and this attraction is heightened by drought stress. Males and females orientate to a volatile released by female A. glabripennis and males attempt to copulate after contacting a sex pheromone on the female cuticle. 7 At present, A. glabripennis is being (or has been) eradicated from areas where it has been introduced. After detection, extensive surveys are conducted and, if breeding populations are detected, at the very least, infested trees are removed and destroyed. Close attention is paid to imported solid wood packaging material to prevent new introductions. 8 Standard practice to control A. glabripennis in China is to spray insecticides in tree canopies. In North America, largely as a preventative measure, systemic insecticides are injected into trees. Entomopathogenic fungi have been developed for the control of A. glabripennis, and entomopathogenic nematodes, coleopteran and hymenopteran parasitoids and predatory woodpeckers have been investigated as biocontrol agents. 9 Ecological control of A. glabripennis in China involves planting mixtures of preferred and nonpreferred tree species, and this practice can successfully prevent outbreaks.

Western corn rootworm (Diabrotica virgifera virgifera LeConte) population dynamics

Abstract: The western corn rootworm Diabrotica virgifera virgifera LeConte is a major insect pest of field maize, Zea mays L. Larvae can cause substantial injury by feeding on maize roots. Larval feeding may destroy individual roots or root nodes, and reduce plant growth, stability, and yield. Costs associated with man- aging corn rootworms in continuous maize are annually one of the largest expen- ditures for insect management in the United States Corn Belt. 2 Even though D. virgifera virgifera has been studied intensively for over 50 years, there is renewed interest in the biology, ecology, and genetics of this species because of its ability to rapidly adapt to management tactics, and its aggressive invasive nature. 3 This article provides a comprehensive review of D. virgifera virgifera population dynamics, specifically: diapause, larval and adult development, seasonality, spa- tial and temporal dynamics at local and landscape scales, invasiveness in North America and Europe, and non-trophic interactions with other arthropods. 4 Gaps in current knowledge are identified and discussed especially within the context of challenges that scientists in North America and Europe are currently facing regarding pest dynamics and the need to develop appropriate management strategies for each geographic area.

Behaviour and ecology of the western corn rootworm (Diabrotica virgifera virgifera LeConte)

Abstract: The western corn rootworm (WCR) is a historic pest with a legacy of resistance and behavioural plasticity. Its behaviour and nutritional ecology are important to rootworm management. The success of the most effective and environmentally benign rootworm management method, annual crop rotation, was based on an understanding of rootworm behaviour and host - plant relationships. Enthusiastic adoption of crop rotation, provided excellent rootworm management, but also selected for behavioural resistance to this cultural control. 2 Though well-studied, significant gaps in WCR biology remain. Understanding the topics reviewed here (mating behaviour, nutritional ecology, larval and adult movement, oviposition, alternate host use, and chemical ecology) is a starting point for adapting integrated pest management and insect resistance management (IRM) to an expanding WCR threat. A presentation of significant questions and areas in need of further study follow each topic. 3 The expansion of WCR populations into Europe exposes this pest to new environ- mental and regulatory conditions that may influence its behaviour and ecology. Reviewing the state of current knowledge provides a starting point of reference for researchers and pest management decision-makers in North America and Europe. 4 The trend toward increasing adoption of transgenic maize will place an increasing pre- mium on understanding WCR behaviour. IRM plans designed to promote sustainable deployment of transgenic hybrids are grounded on assumptions about WCR movement, mating and ovipositional behaviour. Preserving the utility of new and old management options will continue to depend on a thorough understanding of WCR biology, even as the ecological circumstances and geography of WCR problems become more complex.

Dispersal of the emerald ash borer, Agrilus planipennis, in newly‐colonized sites

Abstract: Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive forest insect pest threatening more than 8 billion ash (Fraxinus spp.) trees in North America. Development of effective survey methods and strategies to slow the spread of A. planipennis requires an understanding of dispersal, particularly in recently established satellite populations. 2 We assessed the dispersal of A. planipennis beetles over a single generation at two sites by intensively sampling ash trees at known distances from infested ash logs, the point source of the infestations. Larval density was recorded from more than 100 trees at each site. 3 Density of A. planipennis larvae by distance for one site was fit to the Ricker function, inverse power function, and the negative exponential function using a maximum likelihood approach. The prediction of the best model, a negative exponential function, was compared with the results from both sites. 4 The present study demonstrates that larval densities rapidly declined with distance, and that most larvae (88.9 and 90.3%) were on trees within 100 m of the emergence point of the adults at each site. The larval distribution pattern observed at both sites was adequately described by the negative exponential function.

Mycorrhizal fungi as mediators of defence against insect pests in agricultural systems

Abstract: Below-ground organisms influence above-ground interactions in both natural and agricultural ecosystems. Among the most important below-ground organisms are mycorrhizal fungi, comprising ubiquitous and ancient plant mutualists that have significant effects on plant growth and fitness mediated by resource exchange with plants. In the present study, we focus on the effects of arbuscular mycorrhizal fungi (AMF) on crop defence against insect pests. 2 AMF alter the availability of resources used by crop plants to manufacture defences against pests and to compensate for pest damage. However, AMF also provide plants with nutrients that are known to increase insect performance. Through potentially opposing effects on plant nutritional quality and defence, mycorrhizal fungi can positively or negatively affect pest performance. 3 Additionally, AMF may directly affect gene expression and plant defence signalling pathways involved in the construction and induction of plant defences, and these effects are apparently independent of those caused by nutrient availability. In this way, AMF may still influence plant defences in the fertilized and highly managed systems typical of agribusiness. 4 Because AMF can affect plant tolerance to pest damage, they may have a significant impact on the shape of damage-yield relationships in crops. Potential mechanisms for this effect are suggested. 5 We highlight the need for continuing research on the effects of AMF identity and the abundance on crop defences and tolerance to pest attack. Much work is needed on the potential effects of mycorrhizal colonization on plant signalling and the induction of direct and indirect defences that may protect against pest damage.

Genes, gene flow and adaptation of Diabrotica virgifera virgifera

Abstract: Diabrotica virgifera virgifera has emerged as a major pest of cultivated maize, due to a combination of its high capacity to inflict economic damage, adaptability to pest management techniques and invasiveness. 2 This review presents a survey of the current state of knowledge about the genetics of D. v. virgifera . In addition, the tools and resources currently available to Diabrotica geneticists are identified, as are areas where knowledge is lacking and research should be prioritized. 3 A substantial amount of information has been published concerning the molecular phylogenetic relationships of D. v. virgifera to other chrysomelids. 4 There is a growing literature focused on the population genetics and evolution of the species. Several adaptations to anthropogenic selection pressure have been studied, with resistance to synthetic insecticides providing some particularly well-characterized examples. 5 A notable deficiency is a lack of studies directed toward the formal genetics of D. v. virgifera .

Influence of plant silicon and sugarcane cultivar on mandibular wear in the stalk borer Eldana saccharina

Abstract: Silicon can increase the resistance of plants to attack by herbivorous insects. The present study aimed to determine the effect of silicon and cultivar on man- dibular wear in larvae of the sugarcane stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae). 2 Four sugarcane cultivars, resistant (N21, N33) and susceptible (N11, N26) to E. saccharina were grown in a pot trial in silicon deficient river sand, with (Si + ) and without (Si - ) calcium silicate. Individual third-instar larvae were confined on the sugarcane stalk at three known feeding sites (leaf bud, root band and inter- node) and left to feed for 21 days. 3 Eldana saccharina larval heads were mounted on stubs, with the mandibles ori- ented horizontally and photographed under a scanning electron microscope. Mandibular wear was measured from the digital images using a quantitative method. 4 Although there was a trend for increased wear in larvae that developed on Si + cane, no significant effect of silicon, cultivar or site on mandibular wear of E. saccharina was shown. 5 This is the first study to accurately and quantitatively measure the mandibular wear of an insect fed on Si + plants.

Diversity of canopy and understorey spiders in north‐temperate hardwood forests

Abstract: We characterized and compared diversity patterns of canopy and understorey spiders (Arachnida: Araneae) on sugar maple ( Acer saccharum Marsh.) and American beech ( Fagus grandifolia Ehrh.) in hardwood forests of southern Quebec, Canada. 2 We sampled canopies of 45 sugar maple and 45 American beech trees and associated understorey saplings in mature protected forests near Montreal. Samples were obtained by beating the crown foliage at various heights and by beating saplings around each tree. 3 Eighty-two species were identified from 13 669 individuals. Forty-eight species and 3860 individuals and 72 species and 9809 individuals were collected from the canopy and the understorey, respectively. 4 Multivariate analyses (NMDS ordination and NPMANOVA) showed the compo- sition of canopy and understorey assemblages differed significantly, and canopy assemblages differed between tree species. Rank-abundance distribution models fitted to the canopy and understorey data indicated that different mechanisms structure the assemblages in both habitats. Three abundant spider species were significantly more common in the canopy; ten species were collected significantly more often in the understorey. 5 The forest canopy was shown to be an important reservoir for spider diversity in north-temperate forests.

A flexible sand coating (Conniflex) for the protection of conifer seedlings against damage by the pine weevil Hylobius abietis

Abstract: 1 A new method for the physical protection of conifer seedlings against feeding damage by Hylobius abietis (L.), is described and evaluated in field trials in Swedish forest plantations. 2 The lower 60% of the stem of the seedling is protected by the Conniflex coating, consisting of fine sand (grain size = 0.2 mm) embedded in an acrylate dispersion that remains flexible after drying. 3 Seedlings are treated in the nursery by a large-scale application procedure involving four steps: (i) spraying the seedlings with water; (ii) application of fixative to the lower sections of the stems, (iii) application of fine sand to the fixative; and (iv) drying of the fixative. 4 A field experiment over three seasons demonstrated a significant increase in survival for coated seedlings compared with untreated seedlings. The survival rate increased from 29% to 97% for Scots pine and from 26% to 86% for Norway spruce. Coating the lower 30% of the stem (instead of 60%) provided inferior protection, resulting in only 64% survival in spruce. 5 Field trials in 11 commercial plantation areas indicated that the Conniflex sand coating was as effective in protecting seedlings as treatment with the insecticide imidacloprid. 6 The new method of coating conifer seedlings with fine sand provides an effective and environmentally sound alternative to insecticide treatment.

Organic versus conventional management in an apple orchard: effects of fertilization and tree‐row management on ground‐dwelling predaceous arthropods

Abstract: Organic and conventional management of apple orchards may have a different effect on arthropod communities. 2 We conducted a 3-year study to assess the effect of two strategies of fertilizer treatment (organic versus chemical) and three tree-row management systems (straw mulching, tillage and herbicide) on activity-density and biodiversity of epigeic predators. Ground beetles (Carabidae), rove beetles (Staphylinidae), ants (Formicidae) and spiders (Araneae) were sampled monthly with pitfall traps in the same apple orchard during 2003, 2004 and 2005. 3 A total of 4978 individuals were collected. Carabids (56.8% of the total catches) were the most abundant taxonomic group, followed by spiders (20.7%), ants (14.8%) and rove beetles (7.7%). Tree-row management had a greater influence on predator catches than fertilizer treatment. Total predator catches were lower under the mulch. Mulching also reduced carabid abundance, but increased staphylinid catches. 4 Tree row management also had a significant effect on biodiversity parameters. Species richness did not significantly differ among treatments for ants, spiders or the total catches, but was higher on herbicide-treated plots for carabids and on mulched plots for staphylinids. Shannon - Wiener's diversity index was signifi- cantly greater in the mulched and herbicide treated plots for total predators and carabids. For staphylinids, this index was significantly greater on the mulched plots. Fertilizer application strategy only influenced the species richness of rove beetles, which was greater in the chemically-treated plots. 5 The results showed that a change from conventional to organic fertilizer treatment of apple trees may be performed without differential effects on predator activity- density or biodiversity. However, a change from herbicide treatment to mulching or mechanical weed control may be significant, depending on the taxonomic group.

Dispersal abilities of adult click beetles in arable land revealed by analysis of carbon stable isotopes.

Abstract: 1 The dispersal abilities of agrioted beetles, serious pests on a variety of crops, are poorly known under natural conditions. This hampers their control. We used, for the first time, a stable isotope approach to assess dispersal of adult Agriotes obscurus in arable land. 2 After a diet switch from a C3- to a C4-plant, carbon isotope ratios of A. obscurus larvae significantly changed towards the isotopic signature of the new diet. Moreover, the larval δ13C signatures were transferred to the wing covers of the adult beetles with little distortion. 3 To assess the dispersal abilities under natural conditions, pheromone traps, lured for Agriotes sp., were installed at two study sites in Western Austria. Each site comprised a maize field (= C4-plant) and adjacent C3-grasslands with traps established along a transect of increasing distance to the maize. 4 δ13C signatures of wing covers revealed that adult male A. obscurus were able to migrate at least 80 m, which was the maximum distance that dispersal could be traced in the present study. The dispersal behaviour might have been influenced by site-specific factors. 5 The results obtained demonstrate a higher potential of adult male Agriotes to disperse than previously assumed. Moreover, the combination of pheromone trapping and stable isotope analysis proved to be an effective approach to study insect movement and dispersal in arable systems harbouring C3- and C4-crops.

Evaluation of window flight traps for effectiveness at monitoring dead wood associated beetles: the effect of ethanol lure under contrasting environmental conditions

Abstract: 1. Since the biodiversity of saproxylic beetles has been proposed to be used as a management tool in forestry, more explicit knowledge about the efficiency and selective properties of beetle sampling methods is needed. 2. We compared saproxylic beetle assemblages caught by alcohol-baited or unbaited window traps in different forest contexts. Considering that trap attractiveness depends on kairomone concentrations, we appraised whether the trap efficiency was influenced by trap environment (openness and local supply of fresh dead wood). 3. Saproxylic beetles were sampled using 48 cross-vane window flight traps, arranged in paired designs (alcohol-baited/unbaited), in 8 ancient and 8 recent gaps (open stands), and 8 closed-canopy control stands in an upland beech forest in the French Pyrenees. 4. Baited traps were more efficient than unbaited traps in terms of abundance and richness in our deciduous forests. The ethanol lure did not have any repellent effect on the individual response of saproxylic taxa. 5. The influence of local environmental conditions on trap attractiveness was observed. The effects of variations in openness were actually moderate but significant on species richness. Besides trap attractiveness appeared to be slightly reduced in the alcohol-saturated environment of recent gaps due to a disruption by local fresh dead-wood concentrations of the kairomonal response of saproxylic beetles to baited traps (alcohol disruption'). 6. Since the ethanol lure globally enhances species detection probability (no repellent effect, many individual attractive effects), it may be extensively used in programs of early-warning surveillance, monitoring and control of wood borers. We recommend to account for the slight influences of local conditions on baited trap efficiency while using them for beetle biodiversity monitoring.

Survival at low temperature of larvae of the pine processionary moth Thaumetopoea pityocampa from an area of range expansion.

Abstract: 1 Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy. 2 The supercooling point of individually analysed larvae averaged at −7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to −17 °C for 1 h after gradual temperature decrease, survival was 70.4%. 3 Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field. 4 In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night. 5 We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect’s development.

Trophic promiscuity, intraguild predation and the problem of omnivores

Abstract: Does anybody else miss the good old days of trophic levels? When predators, herbivores and plants knew their place and interacted in appropriate linear chains ( Hairston et al. , 1960; Oksanen, 1981 )? We released biological control agents under the optimistic assumption that they would attack their designated prey, more or less, and at least leave organisms at other trophic levels well alone. We built management programmes and mathematical models based on this assumption (Berryman, 1992). We lived in simpler times. No longer. Omnivores, apparently, are everywhere, practicing their trophic promiscuity in complex and dynamic fashion ( Rosenheim, 2007 ). Predators eat predators, herbivores and, incorrigibly, sometimes plants ( Coll & Guershon, 2002 ). Food chains have become passé, replaced by reticulate webs that defy our simple notions of stability as well as all sense of propriety ( Polis et al. , 1989; Holt & Polis, 1997 ). We are face to face with the uncomfortable reality that our agents of control often eat more broadly than we would like them to. We live in the days of the omnivores. Ecologists who work in unmanaged systems have long been acquainted with the vexing issue of omnivory. Random food webs built on Lotka – Volterra predator – prey equations become less stable with omnivory ( Pimm, 1982 ), unless the omnivorous compartments (or loops) within the webs are characterized by weak links ( Neutel et al. , 2007 ) or nonlinearities ( McCann & Hastings, 1997 ). In other words, omnivory should be either rare or weak for systems to persist. Yet omnivory is apparently ubiquitous ( Denno & Fagan, 2003; Arim & Marquet, 2004 ) and, judging by a casual glance at the ants alone, the links are hardly trivial ( Davidson et al. , 2003; Helms & Vinson, 2008; Ottonetti et al. , 2008 ). For entomologists who work in managed systems, questions of omnivory are taking centre stage in research on agents of biological control. The compatibility of multiple control agents, interactions between native and introduced predators, damage to crops and the spread of crop pathogens are all influenced by the degree to which insects practice omnivory. We have always worried, to some degree, about nontarget effects of biological control agents, but concerns most often were for species at the same trophic level as the target of our control efforts ( Simberloff & Stiling, 1996; Hawkins & Marino, 1997; Louda & Stiling, 2004; Stiling, 2004 ). More and more, we recognize that nontarget effects of biological control agents can emerge at multiple trophic levels ( Rosenheim et al. , 1995; Rosenheim, 1998 ) with the potential to compromise control efforts and influence associated ecosystems. High rates of omnivory may be responsible in part for the spread of exotic invasive predators and the decline of their native counterparts ( Snyder et al. , 2004b ), with successful invaders being those species with adaptations to counter the ravages of omnivorous predators ( Sato & Dixon, 2004 ). I have been thinking about this recently, in part because of the loss of our friend, colleague, and champion of omnivory research, Robert F. (Bob) Denno, who died last year. Others are more qualified to describe the profound and lasting influence that Bob had on the field of entomology. One of his interests in recent years was the study of omnivory, and his group helped to stimulate cutting-edge research on omnivores in natural and managed systems. This paper is not a tribute to Bob’s research. Rather, his passing prompted me to think about the advances in omnivore research made during the last 5 years or so (I cheat with reference to a few important papers of finer vintage), and I present some highlights here with particular reference to managed systems.

Population dynamics of cereal aphids: influence of a shared predator and weather.

Abstract: 1 Aphid populations may show strong year-to-year fluctuations, but questions remain regarding the dominance of factors that cause this variation, especially the role of natural enemies. To better understand the dynamics of aphid species that occur as pests in cereals, we investigated the relative influence of top-down control by a predator and weather (temperature and precipitation) on population fluctuations of three cereal aphid species. 2 From 1987 to 2005, populations of Metopolophium dirhodum, Sitobion avenae and Rhopalosiphum padi in insecticide-free stands of winter wheat were monitored in the Praha-Ruzyne region of the Czech Republic. Densities of an aphidophagous predator, the ladybeetle Coccinella septempunctata, were recorded from an overwintering site in the landscape. Weather was quantified using historical records. 3 A significant bottom-up effect of densities of aphids on those of C. septempunctata was found, but evidence of direct top-down regulation of aphids by C. septempunctata was only significant in the case of R. padi. There was no significant periodicity in the dynamics of the aphid or C. septempunctata, suggesting that there was no clear predator-prey cycle. Combinations of C. septempunctata and weather variables could be used to explain M. dirhodum and R. padi per capita rate of change. There were also indications that weather directly affected peak density of M. dirhodum. 4 We conclude that regional estimates of C. septempunctata densities are not sufficient to determine whether aphid population dynamics are driven by predator?prey interactions. Feasibility of time series analysis as an investigative tool in aphid population dynamics studies is discussed.

Biology of the European large raspberry aphid (Amphorophora idaei): its role in virus transmission and resistance breakdown in red raspberry.

Abstract: 1 The European large raspberry aphid Amphorophora idaei Borner is the most important vector of viral diseases afflicting commercially grown red raspberry (Rubus idaeus L.) in Northern Europe, with European raspberry production amounting to 416 000 tonnes per annum. This review synthesizes existing knowledge on its biology and interactions with other organisms, including its host plant and the viral pathogens it vectors. 2 Information about trophic interactions with other insect herbivores and natural enemies is reviewed. Vine weevils Otiorhynchus sulcatus compromise aphid resistance in some raspberry cultivars, increasing A. idaei abundance by 80%. Parasitoids show mixed success in parasitizing A. idaei, although Aphidius ervi attack rates more than doubled when A. idaei fed on a partially susceptible raspberry cultivar, compared with a resistant variety. These findings are discussed in the context of potential biological control as part of an integrated pest and disease management framework. 3 Amphorophora idaei transmits four known viruses: Black raspberry necrosis virus, Raspberry leaf mottle virus, Raspberry leaf spot virus and Rubus yellow net virus, with A. idaei taking as little as 2 min to transmit some viruses. 4 Existing control strategies, including resistant cultivars, insecticides and eradication of disease from parent plants, are described. In particular, strong selection pressures have resulted in A. idaei overcoming genetic resistance in many raspberry cultivars and most insecticides are now ineffective. 5 Future directions for the sustained control of A. idaei are suggested, taking into consideration the possible effects of climate change and also changes in agronomic practices in U.K. agriculture.

The control of sirex wood wasp using biological control agents in Victoria, Australia

Abstract: 1 The sirex woodwasp, Sirex noctilio has been a significant pest of radiata pine plantations in Victoria since 1961. Outbreaks are usually associated with susceptible trees being under some form of stress including the effects of drought and overcrowding. 2 This paper reviews the spread of sirex and the history and efficacy of biological control programmes implemented against sirex in Victoria from 1970 to 2006. 3 Of the numerous biological control agents released, the most effective in managing sirex have been the nematode Beddingia siricidicola and the parasitic wasp Ibalia leucospoides. Several other parasitic wasps such as Schlettererius cinctipes and Megarhyssa nortoni nortoni have also established but provide only minimal control. 4 While rates of I. leucospoides parasitism have improved over time, it is unlikely that this improvement will continue substantially past current levels. 5 In recent years, issues have arisen regarding a decline in the infectivity of B. siricidicola necessitating a re-evaluation of strategies and development of techniques to overcome this problem. 6 Ongoing research using Random Amplification of Polymorphic DNA (RAPD) testing is underway to accurately determine nematode strains and associated infectivity present in plantations in the field in order to develop management strategies to re-introduce more effective strains.

Long‐term effects of imidacloprid on the abundance of surface‐ and soil‐active nontarget fauna in turf

Abstract: 1 Outbreaks of root-feeding scarab larvae in turfgrass are widely managed through preventive applications of imidacloprid. Long-residual activity and application before feasible scouting probably lead to its overuse and overexposure. 2 Recent investigations revealed a selective impact of imidacloprid (not trichlorfon or halofenozide) on certain nontarget turf arthropods, motivating the present study on the persistence of abundance effects over 6 years of annual applications. 3 Arthropods were sampled monthly (July to October) in replicated plots using soil core heat extraction and pitfall traps to quantify soil- and surface-active arthropods. Captures were identified to class, order or family. The most represented taxa were analysed to test for cumulative effects and their change over season and year. 4 Imidacloprid had no impact on pitfall captures, although the abundance of Hemiptera, Thysanoptera, Coleoptera and Collembola was suppressed in soil core captures. Among beetles, impact was expressed in adults (not larvae), and in Carabidae and Staphylinidae (not Chrysomelidae or Curculionidae). Among springtails, impact was expressed in Entomobryomorpha (not Poduromorpha or Symphypleona). Impact did not diminish with year but there was variable recovery between applications. 5 There may therefore be a diverging response of soil- and surface-active fauna to the nontarget impacts of imidacloprid. The suppression of predaceous (not phytophagous) beetles indicates an indirect effect mediated through declines in prey populations. 6 The magnitude of abundance effects confirms that the balance between target and nontarget impact should be explicitly examined. Implications are discussed with respect to functional relevance for nutrient cycling and the natural regulation of pests.

Agroforestry management affects coffee pests contingent on season and developmental stage

Abstract: Management of vegetational diversity in agroecosystems is a potentially regulat- ing factor of pest population dynamics and may affect developmental stages in different ways. 2 We investigated the population dynamics of red spider mites, coffee leaf miners, and coffee berry borers in three management types of coffee agroforests: increas- ing plant diversity from a few shade tree species (simple-shade agroforests), inter- mediate-shade tree species (complex-shade agroforests) to high-shade tree species (abandoned coffee agroforests) in Ecuador. Furthermore, we studied how changes in agroforestry management affect population stage structure of each coffee pest. 3 Our results show that agroforestry management affected seasonal patterns of cof- fee pests in that higher densities of red spider mites were observed from August to December, coffee leaf miners from December to February, and coffee berry borers from May to July. Moreover, specific developmental stages of red spider mites, coffee leaf miners, and coffee berry borers differed in their responses to agroforestry management. During all stages, red spider mite reached higher den- sities in simple-shade agroforests compared with complex-shade and abandoned agroforests. Meanwhile, coffee leaf miner densities decreased from simple-shade to complex-shade and abandoned agroforests, but only for larvae, not pupae. Similarly, only coffee berry borer adults (but not eggs, larvae and pupae) demon- strated a response to agroforestry management. Environmental variables charac- terizing each agroforestry type proved to be important drivers of pest population densities in the field. 4 We emphasize the importance of considering seasonal differences and population structure while investigating arthropod responses to different habitat types because responses change with time and developmental stages.

Preference–performance relationship and influence of plant relatedness on host use by Pityogenes chalcographus L.

Abstract: Pityogenes chalcographus L. (Coleoptera: Scolytinae) causes damage in European coniferous forests, primarily on Picea abies L. Karst., but is also recorded on other native and exotic Pinaceae species. Estimating the adequacy between adult preference and larval performance of this beetle among its host-range, as well as the influence of plant taxonomic relatedness on these parameters, would provide useful information on the beetle's ability to shift onto novel hosts. 2C hoice and no-choice assays were conducted under laboratory conditions. Adult preference and larval performance parameters among two native (Pinus sylvestris L. and Picea abies )a nd three exotic north American (Pinus contorta Dougl., Picea sitchensis (Bong.) Carr. and Pseudotsuga menziesii Mirbel (Franco)) conifer species were measured. 3 Pityogenes chalcographus exhibited a significant positive relationship between pref- erence and performance. Picea abies was both the preferred and the most suitable host species for larval development. The closest relative, P. sitchensis ,w as the sec- ond best choice in terms of preference and performance. Pseudotsuga menziesii occupied an intermediate position for both beetle preference and performance, and Pinus spp. were the least suitable hosts for beetle development. 4A dult preference and larval performance ranking among hosts provides little support to the plant taxonomic relatedness hypothesis. Taxonomic relatedness could play a role on the diet breadth, although only at a limited scale, within the genus Picea. At higher taxonomic levels, other factors such as bark thickness might be decisive.

Snowdrop lectin (Galanthus nivalis agglutinin) in aphid honeydew negatively affects survival of a honeydew‐ consuming parasitoid

Abstract: 1 Insecticidal proteins can be excreted in the honeydew when sap-sucking insects feed on insect-resistant transgenic plants. Honeydew can be an important source of carbohydrates, thus potentially exposing a broad range of honeydew-feeding insects to transgene products. 2 Snowdrop lectin (Galanthus nivalis agglutinin; GNA) dissolved in a 2 m sucrose solution had no antifeedant effect on female aphid parasitoids (Aphidius ervi) but had a direct negative effect on their longevity. 3 When feeding on honeydew from Rhopalosiphum padi feeding on a GNA-containing artificial diet, Aphidius ervi suffered a longevity reduction that was more pronounced than was to be expected based on the detected GNA concentration in the honeydew. 4 Analysis of carbohydrate and amino acid composition revealed that a change in honeydew composition caused by a GNA-effect on the aphids could be a possible explanation for the additional reduction in parasitoid longevity. 5 When comparing the effect of honeydew from Sitobion avenae and R. padi feeding on GNA-expressing or nontransformed wheat plants on A. ervi longevity, aphid species was found to have a significant effect, whereas the wheat variety had no effect. The latter result was probably due to low GNA expression levels in the plants. Differences in nutritional suitability between honeydew from R. padi and S. avenae could be explained by differences in carbohydrate and amino acid composition. 6 This is the first study to demonstrate that GNA ingested by aphids and transported into the honeydew can negatively affect the parasitoids consuming this honeydew. 7 We recommend that honeydew should be considered as a route of exposure to transgene products in future risk assessment studies.

Successful colonization, reproduction, and new generation emergence in live interior hybrid spruce Picea engelmannii × glauca by mountain pine beetle Dendroctonus ponderosae

Abstract: Although mountain pine beetle Dendroctonus ponderosae Hopkins are able to utilize most available Pinus spp. as hosts, successful colonization and reproduc- tion in other hosts within the Pinaceae is rare. 2 We observed successful reproduction of mountain pine beetle and emergence of new generation adults from interior hybrid spruce Picea engelmannii × glauca and compared a number of parameters related to colonization and reproductive success in spruce with nearby lodgepole pine Pinus contorta infested by moun- tain pine beetle. 3 The results obtained indicate that reduced competition in spruce allowed moun- tain pine beetle parents that survived the colonization process to produce more offspring per pair than in more heavily-infested nearby pine. 4 We also conducted an experiment in which 20 spruce and 20 lodgepole pines were baited with the aggregation pheromone of mountain pine beetle. Nineteen pines (95%) and eight spruce (40%) were attacked by mountain pine beetle, with eight (40%) and three (15%) mass-attacked, respectively. 5 Successful attacks on nonhost trees during extreme epidemics may be one mech- anism by which host shifts and subsequent speciation events have occurred in Dendroctonus spp. bark beetles.

Fertilizer affects the behaviour and performance of Plutella xylostella on brassicas

Abstract: 1 Foliar nitrogen concentration, which can be manipulated in crop plants by fertilizer supply, has long been recognized as a major factor in phytophagous insect abundance and performance. More recently, the type of fertilizer supplied has been shown to influence the abundance of some herbivore species. The diamondback moth Plutella xylostella is a global pest of Brassica crops. Although it has been the subject of numerous studies on host-plant resistance and pest control, few studies have addressed the effect of abiotic factors, such as nutrient supply, on its performance and behaviour. 2 We assessed oviposition preference, larval feeding preference and larval performance of P. xylostella on two cultivars of Brassica oleracea. Plants were grown using two fertilizer types, John Innes fertilizer and an organic animal manure, at high and low concentrations. 3 Plutella xylostella laid more eggs on cultivar Derby Day than Drago. Derby Day was also the cultivar on which larval performance was maximized. However, differences in larval performance between cultivars were only found when plants were grown in compost with John Innes fertilizer, and not when fertilized with animal manure. 4 Foliar nitrogen concentration was greater in plants grown in high fertilizer treatments but did not differ between cultivars. The concentrations of three glucosinolate compounds (glucoiberin, sinigrin and glucobrassicin) were greater in the high fertilizer treatments. Glucosinolate concentrations were higher in the Drago than the Derby Day cultivar. 5 These results are discussed in relation to the preference-performance hypothesis, and the assessment of plant resistance differences between cultivars using different types of fertilizer.

Environment and host-plant genotype effects on the seasonal dynamics of a predatory mite on cassava in sub-humid tropical Africa.

Abstract: In tropical dry seasons, survival of small arthropods such as predatory mites is often negatively affected by low relative humidity (RH). For species that do not diapause or migrate to refuges, the ability of the habitat to mitigate climatic conditions becomes crucial. 2 The relative effect of macro-habitat (dry grassland hill, humid multiple cropping area, humid riparian forest) and microhabitat (host-plant genotypes with hairy, semi-hairy and glabrous apices) on the seasonal dynamics of the phytoseiid mite Typhlodromalus aripo , a predator of Mononychellus tanajoa on cassava, was examined in a field experiment during a dry season. The effect of RH and plant genotype on T. aripo egg survival was determined in an environment control chamber. 3 Predator abundance was higher in humid multiple cropping areas and on hairy cassava compared with the other habitat types and cassava genotypes. 4 Discriminant and regression analyses showed that the predator's dry season per- sistence was related to high RH, high plant vigour and hairy apices, but not to prey abundance. 5 In the controlled climate experiment, the effect of host-plant morphology was evident only at the intermediate RH level of 55%. An effect of apex hairiness was not found. 6 It is concluded that the effect of genotype on T. aripo persistence diminishes un- der low RH conditions, and that supportive effects of apex hairs become effective only in the field, probably through protection from wind and/or intraguild preda- tion. Humid multiple cropping areas planted with hairy and vigorous cassava genotypes are suitable dry season reservoirs for T. aripo .

Genetic identification of morphologically cryptic agricultural pests

Abstract: 1 Wireworms are the polyphagous larvae of click beetles and are well known as agricultural pests. Larvae of the genus Agriotes are internationally recognized as economically important pests of potato. Historically associated with crop damage after conversion of grassland, they are an increasing problem even in all-arable rotations. 2 Current studies of Agriotes ecology and behaviour, and consequently control and management, are seriously hampered by the lack of a means of reliably identifying larvae owing to morphological crypsis during this life-stage. 3 Here, sequence data at the mitochondrial 16SrRNA gene are presented for three species of wireworm: Agriotes obscurus, A. lineatus, and A. sputator. A novel terminal restriction fragment length polymorphism (T-RFLP) technique is described that identifies larvae of these species. This technique is shown to be both efficient and reliable. Interestingly, thus far the samples tested have yielded no A. lineatus. Implications for future study of wireworm ecology and control are discussed.

Risk of Dispersal in Western Spruce Budworm

Abstract: 1 Western spruce budworm Choristoneura occidentalis Free. larvae emerge in the spring before buds have expanded and spend a variable period of time foraging on branches and mining needles. 2 Losses of dispersing budworms during this needle-mining period are related directly to the severity of defoliation in previous years and inversely related to foliage biomass in the study plot and to temperature and rainfall during the needle-mining period. 3 Losses can be interpreted in terms of risk of dispersal, which is the product of the propensity of early-stage budworms to disperse in search of resources and the consequences of this behaviour for survival under variable ecological conditions. 4 A comparison of the species-specific nature of risk of dispersal in three conifer-feeding budworm systems of North America may elucidate the common nature but variable features of their respective population dynamics.

Influence of plot characteristics and surrounding vegetation on the intra-plot spatial distribution of Empoasca vitis

Abstract: 1 Spatial distributions of adults and nymphs of Empoasca vitis were assessed during 3 years inside two adjacent vine plots having considerable intra-plot variability, diversified natural ground cover and surrounding vegetation, and no insecticide application. 2 Geostatistical analysis confirmed that, in spite of repeated adult migrations, spatial distributions of summer populations were highly aggregated, similar every year and similar between adults and nymphs. Comparison of insect distribution with intra-plot characteristics, such as vine plant vigour (leaf density and leaf chlorophyll concentration) and phenology, plot topography and surrounding vegetation, revealed that E. vitis clearly aggregates in areas with the most vigorous vine plants. 3 Even though the presence of natural enemies in the surrounding vegetation was confirmed by specific observations, we did not observe significant population decrease at the contiguous plot edges. Natural ground cover, together with the absence of insecticide, might allow the spreading and perennial conservation of E. vitis natural enemies inside the plots. 4 Clear adult aggregations observed along downwind woodlands suggest that this vegetation acts as a barrier and intercepts the adults flying passively across the plot. However, this surrounding vegetation could also serve as an alternative refuge when vine water deficit and vine foliage temperature increase.

Performance of the potentially invasive Siberian moth Dendrolimus superans sibiricus on coniferous species in Europe.

Abstract: 1 The native range of the Siberian moth extends from the Pacific Ocean (Russian Far East, Japan and Northern Korea) across Siberia, Northern China and Mongolia to the Ural Mountains. At the beginning of the 21st Century, this species was documented west of the Ural Mountains in the Republic of Mari El, indicating range extension toward the west. 2 The Siberian moth has recently been suggested for regulation as a quarantine pest for European and Mediterranean Plant Protection Organization member countries. However, no specific report on European host plants for this pest has been published so far. 3 In the present study, larval host plant choice and performance was tested for the first time on coniferous tree species that are widely distributed and of commercial value in Europe. 4 Based on dual-choice tests on neonates and mortality, developmental duration and relative growth rates of the first- to sixth-instar larvae, we found European larch Larix decidua to be the most suitable host for the moth larvae, whereas European black pine Pinus nigra and Scots pine Pinus sylvestris were the poorest hosts. The remaining conifer species tested, European silver fir Abies alba, Nordmann fir Abies nordmanniana, and Norway spruce Picea abies, were intermediate host plants. Douglas-fir Pseudotsuga menziesii, originating from North America, was chosen by the larvae to the same extend as European larch, and was also highly suitable for larval development. 5 If the moth is introduced to European countries, it will become damaging in stands of European larch and Douglas-fir, mixed stands of fir and spruce; however, it will be less damaging in forests dominated by two-needle pines. 6 We predict that Dendrolimus superans sibiricus will be able to survive and develop on the main European coniferous tree species, including non-native coniferous tree species, resulting in severe damage to large areas of forests.

A review of resistance breeding options targeting western corn rootworm (Diabrotica virgifera virgifera LeConte).

Abstract: This review presents the latest research regarding maize resistance breeding against western corn rootworm (WCR) in the U.S.A. and Europe. Investigations in Europe on the development of maize cultivars possessing resistant mechanisms against WCR are just beginning. In 2003, the European Commission implemented measures aimed at slowing down the spread of the WCR in Europe. Nevertheless, this pest has already been found in 20 countries of the European region. To establish a sustainable production system, the evaluation of native (nontransgenic) resistance in maize cultivars is essential.This review emphasizes the future challenges involved in the research of native resistance breeding in maize against the insect.

Intrinsic and extrinsic determinants of mountain pine beetle population growth

Abstract: 1 Mountain pine beetle Dendroctonus ponderosae populations have large, economically significant outbreaks. Density dependence and environmental variability are expected to have important effects on their dynamics. We analysed time series data from an outbreak in the 1930s to determine the relative importance of population density and environmental variability on local population growth rates. 2 Resource depletion occurred rapidly at the scale of 0.4 ha and population growth rates were strongly density dependent. Annual environmental changes did not have detectable effects on population growth rates, leading to the conclusion that intrinsic processes influenced local population density more than extrinsic factors during this outbreak. 3 Our calculated value of rmax (1.16) does not suggest intrinsically cyclic population dynamics. Our estimate of rmax and density dependence will be useful in developing applied models of mountain pine beetle outbreaks, and the subsequent evaluation of management strategies.