Metapopulation modelling and area-wide pest management strategies evaluation. An application to the Pine processionary moth

Abstract

a b s t r a c tForecasting pest population abundance is a time and resource consuming task, and in particular for areawide pest management is complicated by demographic and environmental stochasticity. These factors make difficult the development of quantitative tools to design and evaluate different management strategies performances by taking into account various form of variability and uncertainty. Pest management could benefit from methods supporting decision making based on models ease of development under scarce data and high uncertainty. Host plants for many agricultural and forest pests are often patchily distributed, therefore population dynamics can be suitably described in terms of metapopulations. Despite the fact that metapopulation models were originally proposed for pests, they remain a widely used tool in conservation biology but receive little attention in large scale pest management.The aim of this paper is to propose a framework allowing the ranking of the efficacy of area-wide pest control strategies, taking into account population spatial distribution in discrete patches. The Kullback-Leibler divergence, well known in Information Theory, Probability and Statistics, is used to measure how far the state of the metapopulation as predicted by a spatially explicit metapopulation model is from a suitable reference state.The method is applied to compare the efficacy of different types of predefined control strategies of the Pine processionary moth (Traumatocampa pityocampa (Den. and Schiff)). The analysis of a dataset on metapopulation dynamics of this moth from a fragmented Mediterranean pine forest allows to derive some rules of thumb for the rational allocation of control effort, in terms of spatial and temporal distribution of the interventions.

Periodicity and synchrony of pine processionary moth outbreaks in France

“…A combination of remote sensing information on PPM abundance at large scales (Bories et al, 2012) with estimates of spatial autocorrelation (Gilioli et al, 2013), could help to define this grain, i.e. the size of the smallest homogeneous landscape unit at which the predictive model should be developed.…”

Seed loss before seed predation: experimental evidence of the negative effects of leaf feeding insects on acorn production

“…Summer drought, with its extreme temperatures and water deficit, constitutes the main cause of premature acorn abortion (Espelta et al 2008 Caterpillars start feeding from early budburst in early April and continue throughout the spring until early June, when the sclerified leaves become too tough to be eaten (Elkinton et al 1996). This phenology is, however, subjected to variability due to the stochasticity of the Mediterranean climate (Gilioli et al 2013). The species composition of caterpillar guilds also changes during the spring, with the family Tortricidae the first to feed on the incipient new shots and the Geometridae species the last (Soria 1987).…”

Spatial patterns at host and forest stand scale and population regulation of the pine processionary mothThaumetopoea pityocampa

“…The spatial population structure of any species will depend on both habitat structure and its own dispersal capabilities (Gripenberg et al , ). Thaumetopoea pityocampa was found to form independent metapopulations in a heterogeneous landscape with a patchy distribution of hosts (Gilioli et al , ), whereas, in a homogeneous landscape, with a continuous distribution of hosts, it exhibits spatial autocorrelation, particularly notable at high population densities, which remain constant in space during at least a few years (Samalens & Rossi, ). In both cases, the poor dispersion capacities of T. pityocampa females (Demolin, ) help to explain these patterns: dispersal of adults from fragmented patches of pine forests is limited, and populations tend to build up around outbreaking spots in a homogeneous landscape.…”

“…The pine processionary moth Thaumetopoea pityocampa (Denis & Schiffermüller) is a forest defoliator with a wide geographical distribution, and is found throughout the Mediterranean Basin and parts of Temperate Europe (OEPP/EPPO, ; Pimentel et al , ), where severe outbreaks occur (Samalens & Rossi, ; Hodar et al , ; Gilioli et al , ; Tamburini et al , ). Females are poor dispersers, which leads to geographically structured populations (Kerdelhué et al , ).…”

“…Spatial patterns of T. pityocampa populations have been the subject of a large number of studies. Analysis of spatial distribution at the macro geographical scale has resulted in a number of different conclusions in accordance with different landscape structures: a homogeneous forest landscape leads to spatial autocorrelation (Samalens & Rossi, ), whereas high forest fragmentation and diversity produces the opposite result (Gilioli et al , ). At the host level, egg batches have been found to present an aggregated distribution on host trees (Arnaldo & Torres, ).…”