Modelling the Geographical Range of a Species with Variable Life-History

New pest modelling paper published in PLoS ONE.

Let me know what you think by adding comments to the PLoS ONE comments page of the article:

Macfadyen S, Kriticos DJ (2012) Modelling the Geographical Range of a Species with Variable Life-History. PLoS ONE 7(7): e40313. doi:10.1371/journal.pone.0040313

In this paper Darren and I show how a climatic niche model can be used to describe the potential geographic distribution of a pest species with variable life-history, and illustrate how to estimate biogeographic pest threats that vary across space. The models were used to explore factors that affect pest risk (irrigation and presences of host plant).

A combination of current distribution records and published experimental data were used to construct separate models for the asexual and sexual lineages of Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) (bird cherry–oat aphid).  Rhopalosiphum padi is a pest of cereals in many countries around the world. Farmers rely heavily on the use of insecticides to control this pest, particularly in winter wheat and barley crops across Europe, as it is a vector of crop diseases. The two models were combined with knowledge of host plant presence to classify the global pest risk posed by R. padi.

Map of the world, showing risk categories for Rhopalosiphum padi invasion.


Two scenarios are shown that represent; (a), natural rainfall conditions; and (b), an irrigation scenario. Results are based on the output from sexual and asexual CLIMEX models and the presence or absence of the primary woody host plant. Invasion risk categories are based on the International Standard for Phytosanitary Measures (ISPM) (FAO 2006). ‘Endangered’ indicates areas that are at risk of R. padi populations establishing and persisting year-round, ‘Transient’ indicates areas that are at risk of seasonal reinvasion but conditions are not suitable for persistence year-round, and ‘Potentially endangered’ indicates areas at risk of persistent populations year-round if a suitable Prunus host plant were introduced. doi:10.1371/journal.pone.0040313.g004

The enemy within: Wolbachia increases the susceptibility of armyworm to viral disease

Interesting paper: Robert I. Graham, David Grzywacz, Wilfred L. Mushobozi and Kenneth Wilson Wolbachia in a major African crop pest increases susceptibility to viral disease rather than protects Ecology Letters 15
DOI: 10.1111/j.1461-0248.2012.01820.x

I just read an exciting paper that shows that field populations of the African armyworm (Spodoptera exempta) that are infected with an endosymbiont bacteria Wolbachia are more susceptible to mortality due to a nucleopolydrovirus (SpexNPV). Wolbachia are common intra-cellular bacteria found in many insect species, and can protect their hosts from viruses. Researchers are trying to use Wolbachia to reduce the ability of mosquito’s to transmit dengue viruses to people. What Graham et al. have shown is that in the future it may be possible to use the wide-spread infection of armywom by Wolbachia to enhance our efforts to kill this pest using a biopesticide.

New paper out: Parasitoid diversity reduces the variability in pest control services

My latest paper from the organic farms study in the UK has just come out. You can download from here or contact me for a copy.

Macfadyen, S., Craze, P., Polaszek, A., van Achterberg, K. & Memmott, J. (2011) Parasitoid diversity reduces the variability in pest control services across time on farms. Proceedings of the Royal Society B, 278: 3387-3394.


Recent declines in biodiversity have increased interest in the link between biodiversity and the provision and sustainability of ecosystem services across space and time. We mapped the complex network of interactions between herbivores and parasitoids to examine the relationship between parasitoid species richness, functional group diversity and the provision of natural pest control services. Quantitative food webs were constructed for 10 organic and 10 conventional farms. Parasitoid species richness varied from 26 to 58 species and we found a significant positive relationship between parasitoid species richness and temporal stability in parasitism rates. Higher species richness was associated with lower variation in parasitism rate. A functional group analysis showed significantly greater parasitoid species complementarity on organic farms, with on average more species in each functional group. We simulated parasitoid removal to predict whether organic farms experienced greater robustness of parasitism in the face of local extinctions. This analysis showed no consistent differences between the organic and conventional farm pairs in terms of loss of pest control service. Finally, it was found that the different habitats that make up each farm do not contribute equally to parasitoid species diversity, and that hedgerows produced more parasitoid species, significantly more so on organic farms.

Insect Identification and Integrated Pest Management Workshop

We held our first IPM and insect identification pest management workshop in Wagga Wagga on the 19th August. We had about 18 participants including growers and consultants. Everyone was very pleased with the I-SPY manual which should provide a valuable resource for those wishing to identify the pests and beneficials in broad acre grains crops. We plan to hold a few more of these workshops throughout the course of the project.

Jo Holloway (I&I NSW) demonstrating the use of the suction sampler

Jo Holloway (I&I NSW) demonstrating the use of the suction sampler

Phil Bowden (I&I NSW) showing participants the catch

Phil Bowden (I&I NSW) showing participants the catch