Controlling and predicting the spread of Heterobasidion annosum in even-aged Pinus pinaster stands in South-West France

Over the past 30 years, Heterobasidion root disease has increased its distribution and impact across in South-West France. This study describes a model for simulating the infection, spread and protective treatment impacts of Heterobasidion spp. in stands of Pinus pinaster (L.). The model includes two submodels; one for stand dynamics with a distance dependant tree growth model and one for disease dynamics: (i) level of air-borne spores and spore infection, (ii) stump and root colonization, (iii) vegetative transfer to tree roots, (iv) spread of disease in tree roots of healthy tree, and (vi) disease effect on tree growth and survival. Two specific processes were studied. First of all, the prediction of high risk season is based on air-borne survey in order to investigate climate impact. Another key point concerns growth losses in trees. For accurate impact assessment, diameter growth loss was investigated by analyzing annual growth increment of pairs of healthy trees vs. trees infected by H. annosum using dendrochronological techniques To illustrate the model, simulations were carried out with different levels of infected stumps as initial disease centers, use of stump treatment and impacts of site fertility on the rate of transfer of the disease. The model provides a means of incorporating the impact of root disease into forest planning

Controlling and predicting the spread of Heterobasidion annosum in even-aged Pinus pinaster stands in South-West France

National audienceOver the past 30 years, Heterobasidion root disease has increased its distribution and impact across in South-West France. This study describes a model for simulating the infection, spread and protective treatment impacts of Heterobasidion spp. in stands of Pinus pinaster (L.). The model includes two submodels; one for stand dynamics with a distance dependant tree growth model and one for disease dynamics: (i) level of air-borne spores and spore infection, (ii) stump and root colonization, (iii) vegetative transfer to tree roots, (iv) spread of disease in tree roots of healthy tree, and (vi) disease effect on tree growth and survival. Two specific processes were studied. First of all, the prediction of high risk season is based on air-borne survey in order to investigate climate impact. Another key point concerns growth losses in trees. For accurate impact assessment, diameter growth loss was investigated by analyzing annual growth increment of pairs of healthy trees vs. trees infected by H. annosum using dendrochronological techniques To illustrate the model, simulations were carried out with different levels of infected stumps as initial disease centers, use of stump treatment and impacts of site fertility on the rate of transfer of the disease. The model provides a means of incorporating the impact of root disease into forest planning

Mean infection index, by site, year and provenance.

<p>The black lines and dots are for the B1 site, the blue lines and squares are for the P8 site. The continuous and dotted lines are for 2001 and 2002, respectively.</p

Statistics for two sites and two years of powdery mildew infection.

<p>Regression coefficients (intercept and slope of regression lines in figures), slope probability (<i>p</i>), adjusted r², 95% confidence intervals, standardised slope coefficient (SSC, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155344#pone.0155344.e006" target="_blank">Eq 3</a>), 95% confidence interval of SSC assessed with Delta method [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155344#pone.0155344.ref037" target="_blank">37</a>], and Pearson correlation coefficient (r). Note: r and the slope have equal probabilities.</p

Infection severity in 2002, as a function of severity in 2001, at the two sites.

<p>Infection severity in 2002, as a function of severity in 2001, at the two sites.</p

Number of trees, mean infection index and standard deviation, by site, provenance and year.

<p>The means in bold differed significantly (<i>p</i><0.05) for the year concerned.</p

Growth index as a function of mean infection index in 2001–2002 and regression lines for two sites.

<p>Growth index as a function of mean infection index in 2001–2002 and regression lines for two sites.</p

At the P8 site: the green line indicates phenology (median score, from 0 = dormant bud to 6 = fully developed leaves), and the red line indicates powdery mildew severity (mean % of the leaf surface infected).

<p>The blue arrow indicates the date of the late frost.</p

Growth index in 2003 as a function of mean infection index in 2001–2002 for two sites.

<p>Growth index in 2003 as a function of mean infection index in 2001–2002 for two sites.</p

Final infection severity and basal area increment (BAI), by year and site.

<p>The boxplot shows the median in black, the mean in red, the first and third quartile, and the outliers. <i>n</i> = 67 oaks at B1 (grey) and <i>n</i> = 61 oaks at P8 (white).</p