Mode of overwintering of invasive Harmonia axyridis in the Netherlands
Raak-van den Berg, C.L. ; Hemerik, L. ; Jong, P.W. de; Lenteren, J.C. van - \ 2012
BioControl 57 (2012)1. - ISSN 1386-6141 - p. 71 - 84.
coccinella-septempunctata coleoptera - temperature-dependent development - hippodamia-convergens coleoptera - adalia-bipunctata coleoptera - lady beetle coleoptera - thermal requirements - pallas coleoptera - life-history - photoperiodic response - reproductive di
After establishment of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Europe, population densities of native ladybird species have decreased. The post-hibernation onset of female reproduction, a key characteristic influencing population dynamics and competition with related species, was studied. Hibernating individuals were collected and transferred to outdoor cages to continue overwintering. Every two weeks a sample of individuals was transferred to long-day, warm conditions. Intensity of dormancy was studied by determining the pre-oviposition period and ovarian development. Pre-oviposition periods were short throughout our observations, indicating that Harmonia axyridis was not in diapause but in a quiescent state. H. axyridis becomes active rapidly when temperature rises in spring but is not active earlier in the year than native species. Neither the mode of overwintering, nor the onset of spring activity can explain the invasion success of H. axyridis
Predicting the time to colonization of the parasitoid Diadegma semiclausum: the importance of the shape of spatial dispersal kernels for biological control
Bianchi, F.J.J.A. ; Schellhorn, N.A. ; Werf, W. van der - \ 2009
Biological Control 50 (2009)3. - ISSN 1049-9644 - p. 267 - 274.
coccinella-septempunctata coleoptera - agricultural landscapes - pest-control - field conditions - populations - habitats - movement - systems - spread - biodiversity
The time at which natural enemies colonize crop fields is an important determinant of their ability to suppress pest populations. This timing depends on the distance between source and sink habitats in the landscape. Here we estimate the time to colonization of sink habitats from a distant source habitat, using empirical mark-capture data of Diadegma semiclausum in Broccoli. The data originated from experiments conducted at two locations and dispersal was quantified by suction sampling before and after a major disturbance. Three dispersal kernels were fitted to the dispersal data: a normal, a negative exponential, and a square root negative exponential kernel. These kernels are characterized by a thin, intermediate and a fat tail, respectively. The dispersal kernels were included in an integro-difference equation model for parasitoid population redistribution to generate estimates of time to colonization of D. semiclausum in sink habitats at distances between 100 and 2000 m from a source. We show that the three dispersal kernels receive similar support from the data, but can produce a wide range of outcomes. The estimated arrival time of 1% of the D. semiclausum population at a distance 2000 m from the source ranges from 12 days to a length of time greatly exceeding the life span of the parasitoid. The square root negative exponential function, having the thickest tail among the tested functions, gave the fastest spread and colonization in three of the four data sets, but it gave the slowest redistribution in the fourth. In all four data sets, the rate of accumulation at the target increased with the mean dispersal distance of the fitted kernel model, irrespective of the fatness of the tail. This study underscores the importance of selecting a proper dispersal kernel for modelling spread and colonization time of organisms, and of the collection of pertinent data that enable kernel estimation and that can discriminate between different kernel shapes
Changes in agricultural land use can explain population decline in a ladybeetle species in the Czech Republic : evidence from a process-based spatially explicit model
Bianchi, F.J.J.A. ; Hon¿k, A. ; Werf, W. van der - \ 2007
Landscape Ecology 22 (2007)10. - ISSN 0921-2973 - p. 1541 - 1554.
coccinella-septempunctata coleoptera - metopolophium-dirhodum - linyphiid spiders - natural enemies - landscape - aphids - biodiversity - abundance - movement - dynamics
Changes in land use affect species interactions and population dynamics by modifying the spatial template of trophic interaction and the availability of resources in time and space. We developed a process-based spatially explicit model for evaluating the effects of land use on species viability by modelling foraging performance and energy sequestration in a stage structured, three-trophic population model. The model is parameterized with realistic parameters for a ladybeetle¿aphid¿host plant interaction, and is run in four realistic landscapes in the Czech Republic. We analysed whether changes in crop selection and fertilizer input could explain the dramatic and unexplained decline in abundance of the ladybeetle Coccinella septempunctata in the Czech Republic from 1978 to 2005. The results indicate that a major reduction in fertilizer input after the transition to a market economy, resulting in lower aphid population densities in cereal crops and negatively affecting energy sequestration, survival and reproduction of ladybeetles, provides a sufficient explanation for the observed population decline. Simulations further indicated that the population viability of C. septempunctata is highly dependent on availability of aphid prey in crops, in particular cereal, which serves as their major reproduction habitat. The results demonstrate how the abundance of naturally occurring predators, which are instrumental for biological pest control, depends upon the spatial resource template that are provided at the landscape scale.
Model evaluation of the function of prey in non-crop habitats for biological control by ladybeetles in agricultural landscapes
Bianchi, F.J.J.A. ; Werf, W. van der - \ 2004
Ecological Modelling 171 (2004)1-2. - ISSN 0304-3800 - p. 177 - 193.
coccinella-septempunctata coleoptera - russian wheat aphid - spatiotemporal model - beneficial insects - natural enemies - intrinsic rate - field - abundance - homoptera - temperature
The availability of alternative prey is considered to be an important factor for the conservation of predators in agro-ecosystems. However, only a limited number of studies have investigated the effect of prey availability in non-crop habitats on predator impact. We studied the potential of the generalist predator Coccinella septempunctata to control pest aphids in wheat fields in landscapes with varying levels of prey in non-crop habitats using a spatially explicit simulation model. Simulations indicate that C. septempunctata reproduction and the associated control of pest aphids is affected by both the availability of non-pest aphids in non-crop habitats and the infestation date of pest aphids in wheat fields. When the infestation of wheat by pest aphids takes place early in the season, prey availability of pest aphids alone is sufficient to allow C. septempunctata to attain its maximal reproduction. However, when the infestation by pest aphids is somewhat delayed, C. septempunctata becomes increasingly dependent on aphids in non-crop habitats. Scarcity of prey may prevent C. septempunctata from reproducing or initiate long distance migration. Therefore, prey availability in non-crop habitats may play a significant part in the conservation of ladybeetles and the related biological control in agro-ecosystems. (C) 2003 Elsevier B.V. All rights reserved.