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Pest Outbreaks (pest + outbreak)
Selected AbstractsFallowing did not disrupt invertebrate fauna in Philippine low-pesticide irrigated rice fieldsJOURNAL OF APPLIED ECOLOGY, Issue 3 2010Kenneth G. Schoenly Summary 1.,Fallowing, a type of rotation where no crop is grown, deprives insect pests of food. In tropical irrigated rice, it is not known whether fallow periods deplete natural enemy populations and reduce their pest control effectiveness in post-fallow crops. We tested the null hypothesis that small-scale synchronous cropping (embedded in asynchronously planted rice landscapes) does not significantly increase pest densities during post-fallow periods in the presence of a large, diverse natural enemy complex undisrupted by insecticides. We tested this null hypothesis by comparing the invertebrate fauna before and after fallowing. 2.,In six molluscicide-only fields at the International Rice Research Institute (IRRI) in southern Luzon and at Zaragoza in central Luzon, Philippines, canopy and floodwater invertebrates were vacuum-sampled over two cropping seasons, dry and wet. 3.,Thirty-three of the ubiquitous common taxa dominated the samples in both seasons at each site. Most species were natural enemies of rice pests and recyclers of organic matter in the floodwater and waterlogged sediments; some were rice pests. 4.,Fallowing depleted populations of more ubiquitous taxa at Zaragoza (four natural enemies, one detritivore) than at IRRI (one herbivore, one natural enemy). At both sites, only green leafhoppers, Nephotettix virescens and Nephotettix nigropictus, had consistently higher post-fallow densities than pre-fallow densities. 5.,At both sites, fallowing did not affect rice-invertebrate faunas differently between seasons with regard to community structure, trajectories and accumulation rates of guild members. 6.,Synthesis and applications.,In tropical irrigated rice fields, small-scale synchronous fallowing combined with low-pesticide inputs and pest-resistant rice varieties did not induce pest outbreaks or notably diminish populations of natural enemies when embedded in asynchronous cropping on larger, regional scales. Our results suggest that small-scale synchronous fallowing, when embedded in asynchronously planted landscapes, does little harm to biological regulation of the invertebrate faunal community and may be adopted as part of integrated pest management when it serves other purposes. [source] Spatio-temporal analysis of plant pests in a greenhouse using a Bayesian approachAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Christine Poncet 1The present study aimed to propose a method that can improve our understanding of pest outbreaks and spatio-temporal development in greenhouse crops. 2The experiment was carried out in a greenhouse rose crop grown under integrated pest management (IPM) for 21 months. The main pests observed were powdery mildew, two-spotted spider mites and western flower thrips. A quick visual sampling method was established to provide continuous monitoring of overall crop health. 3A Bayesian inferential approach was then used to analyse temporal and spatial heterogeneity in the occurrence of pests. Interactions between pest dynamics and properties of spatial evolutions were exhibited revealing the influence of biotic and abiotic factors on crop health. 4In the context of IPM, this information could be used to improve monitoring strategies by identifying periods or locations at risk. It could also facilitate the implementation of the whole IPM procedure through the identification of key factors that have a negative impact on overall crop health. [source] MODELING IMPACTS OF BIOENERGY MARKETS ON NONINDUSTRIAL PRIVATE FOREST MANAGEMENT IN THE SOUTHEASTERN UNITED STATESNATURAL RESOURCE MODELING, Issue 3 2009ANDRES SUSAETA Abstract The potential impacts of bioenergy markets on slash pine plantation management on nonindustrial private forestlands in the southeastern United States were analyzed. We developed an integrated Black,Scholes and modified Hartman model to achieve this task. The risk of damage from catastrophic natural disturbances such as wildfires and pest outbreaks associated with the exclusion/incorporation of thinnings and variation in timber salvage rates was also included. Three scenario sets were considered:,status quo,or,no thinning scenario, thinning scenario for pulpwood,,and,thinning scenario for bioenergy,at differing levels of risk and salvage. The results indicated that the incorporation of thinnings either for pulpwood or bioenergy increases the forestland value regardless of the risk when the salvage value of the stand is 0.8. When the two thinning scenarios were compared, the land expectation value for the,thinning scenario for bioenergy,was greater at any level of risk compared with the,thinning scenario for pulpwood, averaging a difference of 11.5% and 11.7% for salvageable portions of 0.8 and 0, respectively. [source] Grape powdery mildew as a food source for generalist predatory mites occurring in vineyards: effects on life-history traitsANNALS OF APPLIED BIOLOGY, Issue 1 2009A. Pozzebon Abstract In several perennial cropping systems, generalist or omnivorous species represent important biocontrol agents. They can persist on plants by feeding on alternative foods when prey is scarce and potentially limit pest outbreaks. Among beneficials characterised by a wide food range, those belonging to the acarine family Phytoseiidae represent important biocontrol agents. Generalist predatory mites can develop and reproduce using various food sources as alternatives to their tetranychid prey. The presence of alternative food sources can also induce switching feeding behaviour of generalist predators from prey to alternative foods. We evaluated in the laboratory the role of the grape powdery mildew (GPM) for the survival, development and reproduction of Amblyseius andersoni and Typhlodromus pyri, two important beneficial phytoseiid mites, in European and North-American vineyards. We also compared life-history parameters obtained when feeding on GPM with those obtained feeding on tetranychids mite prey or cattail pollen. Results indicated that GPM is an adequate food source for generalist mite survival and development. Results suggest that GPM can sustain mite populations in the absence of higher quality food sources. Based on optimal foraging theory, comparison of life-history parameters on GPM and mite prey suggests that the disruption of phytophagous mite control by these predatory mites in the presence of GPM appears unlikely. Implications for biological control in vineyards are discussed. [source] Generalist predators in organically and conventionally managed grass-clover fields: implications for conservation biological controlANNALS OF APPLIED BIOLOGY, Issue 2 2008K Birkhofer Abstract Organically managed agroecosystems rely in part on biological control to prevent pest outbreaks. Generalist predators (Araneae, Carabidae and Staphylinidae) are a major component of the natural enemy community in agroecosystems. We assessed the seasonal dynamics of major generalist predator groups in conventionally and organically managed grass,clover fields that primarily differed by fertilisation strategy. We further established an experiment, manipulating the abundant wolf spider genus Pardosa, to identify the importance of these predators for herbivore suppression in the same system and growth period. Organic management significantly enhanced ground-active spider numbers early and late in the growing season, with potentially positive effects of plant cover and non-pest decomposer prey. However, enhancing spider numbers in the field experiment did not improve biological control in organically managed grass,clover fields. Similar to the survey results, reduced densities of Pardosa had no short-term effect on any prey taxa; however, spider guild structure changed in response to Pardosa manipulation. In the presence of fewer Pardosa, other ground-running spiders were more abundant; therefore, their impact on herbivore numbers may have been elevated, possibly cancelling increases in herbivore numbers because of reduced predation by Pardosa. Our results indicate positive effects of organic farming on spider activity density; however, our survey data and the predator manipulation experiment failed to find evidence that ground-running spiders reduced herbivore numbers. We therefore suggest that a positive impact of organic fertilisers on wolf spiders in grass,clover agroecosystems may not necessarily improve biological control when compared with conventional farming. [source] Species richness and abundance of defoliating Lepidoptera associated with Eucalyptus grandis in Brazil and their response to plant ageAUSTRAL ECOLOGY, Issue 6 2001J. C. Zanuncio Abstract The present paper documents patterns of species richness and abundance in Lepidoptera associated with a Eucalyptus grandis plantation, and how these patterns relate to plant age. The large number of species collected (1385), the lack of dominant species and the absence of pest outbreaks during the survey may be related to the high level of plant diversity of the native forest reserves in the area. There was no clear pattern of seasonal variation in species richness, but there were seasonal fluctuations in abundance, with minor defoliator species prevailing in October at the start of the rainy season. Species richness and abundance of Lepidoptera were positively correlated, with both variables decreasing in older plantations. However, the greatest numbers of major outbreak species and minor eucalypt defoliators were observed in plants after the mid-point (6 years old) of their cutting cycle (7,10 years). This may be because of a larger amount of better-quality plant leaves after this mid-point or the reduction in silvicultural management interventions at this period of the Eucalyptus cutting cycle. The abundance of the main outbreak species observed in the survey, Stenalcidia grosica Schaus (Geometridae), was negatively correlated with plant age. Nonetheless, the effect was weak (r = , 0.21, P = 0.03) and we were not able to find further significant correlations between plant age and abundance of the other most frequent and constant species that were collected. [source] | ||||||||||