Managing outbreaks of invasive species: eradication vs. suppression

A framework is developed to evaluate eradication as one of three alternative management responses to an outbreak of an invasive species: eradication, suppression or no action. This framework can be used to establish under what conditions an eradication option could provide an expected net economic benefit, and whether this net benefit exceeds that of the other two options. The eradication option is more likely to be preferred in situations where there is an immediate export benefit that is derived from eradication of the outbreak, and also the uncertainty associated with the likely success of eradication is low.

The importance of temperature and moisture to the egg-laying behaviour of a pest slug, Deroceras reticulatum

Oviposition behaviour is important when modelling the population dynamics of many invertebrates. The numbers of eggs laid are frequently used to describe fecundity, but this measure may differ significantly from realised fecundity. Oviposition has been shown to be important when describing the dynamics of slug populations, which are important agricultural pests. The numbers of eggs laid by Deroceras reticulatum and their viability were measured across a range of 16 temperature (4, 10, 15 and 23 degrees C) by moisture (33%, 42%, 53% and 58% by dry soil weight) experimental combinations. A fitted quadratic response surface model was used to estimate how D. reticulatum adjusted its egg laying to the surrounding temperature and moisture conditions, with most eggs being laid at a combination of 53% soil moisture and 18 degrees C. The number and proportion of viable eggs also covaried with temperature and moisture, suggesting that D. reticulatum may alter their investment in reproduction to maximise their fitness. We have shown that the number of viable eggs differs from the total number of eggs laid by D. reticulatum. Changes in egg viability with temperature and moisture may also be seen in other species and should be considered when modelling populations of egg-laying invertebrates.

Effects of a sex-ratio distorting endosymbiont on mtDNA variation in a global insect pest

Background: Patterns of mtDNA variation within a species reflect long-term population structure, but may also be influenced by maternally inherited endosymbionts, such as Wolbachia. These bacteria often alter host reproductive biology and can drive particular mtDNA haplotypes through populations. We investigated the impacts of Wolbachia infection and geography on mtDNA variation in the diamondback moth, a major global pest whose geographic distribution reflects both natural processes and transport via human agricultural activities. Results: The mtDNA phylogeny of 95 individuals sampled from 10 countries on four continents revealed two major clades. One contained only Wolbachia-infected individuals from Malaysia and Kenya, while the other contained only uninfected individuals, from all countries including Malaysia and Kenya. Within the uninfected group was a further clade containing all individuals from Australasia and displaying very limited sequence variation. In contrast, a biparental nuclear gene phylogeny did not have infected and uninfected clades, supporting the notion that maternally-inherited Wolbachia are responsible for the mtDNA pattern. Only about 5% (15/306) of our global sample of individuals was infected with the plutWBI isolate and even within infected local populations, many insects were uninfected. Comparisons of infected and uninfected isofemale lines revealed that plutWBI is associated with sex ratio distortion. Uninfected lines have a 1:1 sex ratio, while infected ones show a 2:1 female bias. Conclusion: The main correlate of mtDNA variation in P. xylostella is presence or absence of the plutWBI infection. This is associated with substantial sex ratio distortion and the underlying mechanisms deserve further study. In contrast, geographic origin is a poor predictor of moth mtDNA sequences, reflecting human activity in moving the insects around the globe. The exception is a clade of Australasian individuals, which may reflect a bottleneck during their recent introduction to this region.

A novel method for assessing risks to pollinators from plant protection products using honeybees as a model species

Pollination is one of the most important ecosystem services in agroecosystems and supports food production. Pollinators are potentially at risk being exposed to pesticides and the main route of exposure is direct contact, in some cases ingestion, of contaminated materials such as pollen, nectar, flowers and foliage. To date there are no suitable methods for predicting pesticide exposure for pollinators, therefore official procedures to assess pesticide risk are based on a Hazard Quotient. Here we develop a procedure to assess exposure and risk for pollinators based on the foraging behaviour of honeybees (Apis mellifera) and using this species as indicator representative of pollinating insects. The method was applied in 13 European field sites with different climatic, landscape and land use characteristics. The level of risk during the crop growing season was evaluated as a function of the active ingredients used and application regime. Risk levels were primarily determined by the agronomic practices employed (i.e. crop type, pest control method, pesticide use), and there was a clear temporal partitioning of risks through time. Generally the risk was higher in sites cultivated with permanent crops, such as vineyard and olive, than in annual crops, such as cereals and oil seed rape. The greatest level of risk is generally found at the beginning of the growing season for annual crops and later in June–July for permanent crops.

Investigating the phytotoxicity of the graminicide fluazifop-P-butyl against native UK wildflower species

BACKGROUND: The selective graminicide fluazifop-P-butyl is used for the control of grass weeds in dicotyledonous crops, and commonly applied in amenity areas to reduce grass productivity and promote wildflower establishment. However, evidence suggests that fluazifop-P-butylmight also have phytotoxic effects on somenon-target plants. This study investigates the effects of fluazifop-P-butyl on the emergence, phytotoxicity and above-ground biomass of nine perennial wildflower species and two grass species, following pre- and post-emergent applications at half, full and double label rates in a series of glasshouse experiments. RESULTS: While pre- and post-emergent applications of fluazifop-P-butyl caused reductions in seedling emergence and increased phytotoxicity on native wildflower and grass species, these effects were temporary for the majority of wildflower species tested, and generally only occurred at the double application rate. No differences in biomass were observed at any of the rates, suggesting good selectivity and no long-term effects of fluazifop-P-butyl application on the wildflower species from either pre-emergent or post-emergent applications. CONCLUSION: These results have direct relevance to the management of amenity areas for biodiversity, as they confirm the suitability of these wildflower species for inclusion in seed mixtures where fluazifop-P-butyl is to be applied to control grass productivity.

Variation in the sensitivity of Callosobruchus (Coleoptera: Bruchidae) acetylcholinesterase to the organophosphate insecticide malaoxon: effect of species, geographical strain and food type

BACKGROUND: Bruchid beetles, Callosobruchus species, are serious pests of economically important grain legumes; their activity in stores is often controlled by use of synthetic insecticides. Esterases are known to be involved in insecticide resistance in insects. However, there is dearth of information on esterase activity in the genus Callosobruchus. In this study we investigated the effect of species, geographical strain and food type on the variation of acetylcholinesterase (AChE) activity and its inhibition by malaoxon (malathion metabolite) using an in vitro spectrophotometric method. RESULT: AChE activity varied significantly among species and strains and also among legume type used for rearing them. Generally irrespective of species, strain or food type, the higher the AChE activity of a population, the higher its inhibition by malaoxon. C. chinensis had the highest AChE activity of the species studied and in the presence of malaoxon it had the lowest remaining AChE activity, while C. rhodesianus retained the highest activity. CONCLUSION: A firsthand knowledge of AChE activity in regional Callosobruchus in line with the prevailing food types should be of utmost importance to grain legume breeders, researchers on plant materials for bruchid control and pesticide manufacturer/applicators for a robust integrated management of these bruchids.

Organic soils promote the efficacy of entomopathogenic nematodes, with different foraging strategies, in the control of a major forest pest: a meta-analysis of field trial data

The large pine weevil, Hylobius abietis, is a serious pest of reforestation in northern Europe. However, weevils developing in stumps of felled trees can be killed by entomopathogenic nematodes applied to soil around the stumps and this method of control has been used at an operational level in the UK and Ireland. We investigated the factors affecting the efficacy of entomopathogenic nematodes in the control of the large pine weevil spanning 10 years of field experiments, by means of a meta-analysis of published studies and previously unpublished data. We investigated two species with different foraging strategies, the ‘ambusher’ Steinernema carpocapsae, the species most often used at an operational level, and the ‘cruiser’ Heterorhabditis downesi. Efficacy was measured both by percentage reduction in numbers of adults emerging relative to untreated controls and by percentage parasitism of developing weevils in the stump. Both measures were significantly higher with H. downesi compared to S. carpocapsae. General linear models were constructed for each nematode species separately, using substrate type (peat versus mineral soil) and tree species (pine versus spruce) as fixed factors, weevil abundance (from the mean of untreated stumps) as a covariate and percentage reduction or percentage parasitism as the response variable. For both nematode species, the most significant and parsimonious models showed that substrate type was consistently, but not always, the most significant variable, whether replicates were at a site or stump level, and that peaty soils significantly promote the efficacy of both species. Efficacy, in terms of percentage parasitism, was not density dependent.

Can a native rodent species limit the invasive potential of a non-native rodent species in tropical agroforest habitats?

BACKGROUND Little is known about native and non-native rodent species interactions in complex tropical agro-ecosystems. We hypothesised that the native non-pest rodent Rattus everetti may be competitively dominant over the invasive pest rodent Rattus tanezumi within agroforests. We tested this experimentally by using pulse removal for three consecutive months to reduce populations of R. everetti in agroforest habitat and assessed over 6-months the response of R. tanezumi and other rodent species. RESULTS Following removal, R. everetti individuals rapidly immigrated into removal sites. At the end of the study period, R. tanezumi were larger and there was a significant shift in their microhabitat use with respect to the use of ground vegetation cover following the perturbation of R. everetti. Irrespective of treatment, R. tanezumi selected microhabitat with less tree canopy cover, indicative of severely disturbed habitat, whereas, R. everetti selected microhabitat with a dense canopy. CONCLUSION Our results suggest that sustained habitat disturbance in agroforests favours R. tanezumi, whilst the regeneration of agroforests towards a more natural state would favour native species and may reduce pest pressure in adjacent crops. In addition, the rapid recolonisation of R. everetti suggests this species would be able to recover from non-target impacts of short-term rodent pest control.

Species Diversity of Myrmecofauna and Araneofauna Associated with Agroecosystem and Forest Fragments and their Interaction with Carabidae and Staphylinidae (Coleoptera)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biology of Thaumastocoris peregrinus in different eucalyptus species and hybrids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Attractiveness of different sweet and fatty substances to three neotropical tramp ant species (Hymenoptera : Formicidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nutrients affecting food choice by the pest subterranean termite Coptotermes gestroi (Isoptera: Rhinotermitidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Insecticide selectivity to two species of Trichogramma in three different hosts, as determined by IOBC/WPRS methodology

BACKGROUND: The use of Trichogramma species is a potential key strategy in integrated pest management. However, its effectiveness depends on the use of chemicals that do not interfere with parasitism and parasite population growth. Here, a study was made of the effects of synthetic insecticides on Trichogramma pretiosum and Trichogramma exiguum in different hosts (Ephestia kuehniella, Plutella xylostella and Spodoptera frugiperda) and the influence of International Organisation for Biological Control (IOBC/WPRS) methodology in selectivity studies using different Trichogramma species. The insecticides used were commercial formulations (triflumuron at a concentration of 0.2 mL L-1 water, etofenprox at a concentration of 0.47 mL L-1 water and endosulfan at a concentration of 7.5 mL L-1 water); the control treatment consisted of distilled water. Eggs attached to cardboard cards were offered to parasitoids inside glass cages. Parasitised eggs, parasitism and adult emergence rates and parasitism reduction were evaluated.RESULTS: Endosulfan and etofenprox, classified as class-4 toxic products, were extremely toxic to the parasitoids. Triflumuron, classified as a non-toxic product, was selective to the parasitoids in eggs of all hosts.CONCLUSIONS: The methodology recommended by IOBC/WPRS influenced results regarding the use of different species of parasitoids, and the use of a single parasitoid species in their experiment is questionable. (C) 2011 Society of Chemical Industry

Expressed sequence tags from Atta laevigata and identification of candidate genes for the control of pest leaf-cutting ants.

Leafcutters are the highest evolved within Neotropical ants in the tribe Attini and model systems for studying caste formation, labor division and symbiosis with microorganisms. Some species of leafcutters are agricultural pests controlled by chemicals which affect other animals and accumulate in the environment. Aiming to provide genetic basis for the study of leafcutters and for the development of more specific and environmentally friendly methods for the control of pest leafcutters, we generated expressed sequence tag data from Atta laevigata, one of the pest ants with broad geographic distribution in South America. Results: The analysis of the expressed sequence tags allowed us to characterize 2,006 unique sequences in Atta laevigata. Sixteen of these genes had a high number of transcripts and are likely positively selected for high level of gene expression, being responsible for three basic biological functions: energy conservation through redox reactions in mitochondria; cytoskeleton and muscle structuring; regulation of gene expression and metabolism. Based on leafcutters lifestyle and reports of genes involved in key processes of other social insects, we identified 146 sequences potential targets for controlling pest leafcutters. The targets are responsible for antixenobiosis, development and longevity, immunity, resistance to pathogens, pheromone function, cell signaling, behavior, polysaccharide metabolism and arginine kynase activity. Conclusion: The generation and analysis of expressed sequence tags from Atta laevigata have provided important genetic basis for future studies on the biology of leaf-cutting ants and may contribute to the development of a more specific and environmentally friendly method for the control of agricultural pest leafcutters.

Notes on Eucryptotermes with a new species from central Amazonia (Isoptera: Kalotermitidae)

Eucryptotermes breviceps, new species, is described from central Amazonia. Both imagoes and soldiers of this new species have only two apical spurs on the foretibia, a condition previously unknown for Kalotermitidae. The soldier of E. breviceps has a peculiar and extremely phragmotic head. The geographical distribution of E. wheeleri is expanded with new records, and measurements of soldiers and imagoes of this species are presented for the first time. E. wheeleri is a native of the Atlantic forest of southeastern Brazil, from Santa Catarina to Rio de Janeiro, but it has been recorded in urban areas and may be an occasional minor pest.