The main objective is to increase the knowledge on relationships between trees under stress and pests, and to build a coherent frame of conclusions leading to define indicators for pest and disease risk in forest stands, applicable in the context of enviromental changes.
Intermediate objectives are:
1. To assess, in a diversity of pine-pest and pine-disease models, the validity of the plant stress pest performance hypothesis that suggests that plant under abiotic stress become more susceptible to pests and diseases;
2. To understand how water and nutrient stress may influence tree health;
3. To identify the physiological and biochemical mechanisms of interaction between abiotic stress and susceptibility to insects and pathogens. Considering a variety of pests and diseases belonging to different guilds is thus a necessity, but a strong integration of the research work iS necessary to allow reliable results and synthetic conclusions. All experiments will be focused on pine (P. sylvestris; P. pinaster), with the same experimental approach in all pest/disease pine models. Several pests and pathogens will be considered in each experiment. The 2 above pine species have been chosen because they naturally bear a high diversity of pests and diseases, because they constitute a sample representative of conifer forestry in Europe along a North - South axis, because their secondary metabolises involved in natural resistance are generally known, and because international cooperations preexisted. Five different guilds will be considered: - Root pathogens; - Stem pathogens and stem boring insects; - Foliage pathogens and phyllophagous grazing insects; Cone, bud and shoot mining insects; - Sap-sucking insects (foliage and stem).
Experiments will concerned trees in the field (5 exp.) and trees in pots (2 exp.). In most cases (6/7), age and size will correspond to those of naturally attacked trees. Each experiment will aim at modifying the C/N ratio by manipulating photosynthesis (through water stress) and nutrients (through fertilization). In all cases, at reast 2 levels of water availability and 2 levels of nutrient availability will be experimentally combined. Water and nutrient supplies will be strictly controlled. Water and nutrient status of the trees will be followed all over the course of the experiments. Water balance and nutrient budget will be established. In all experiments, effects of treatments will be measured on tree growth, C/N ratio in tree tissues, photosynthesis, secondary metabolises (terpenes and phenols), damage and parasite performances.
Comparison between stress levels and pest performances will help to define stress thresholds. Chemical, biological and physiologa-1 parameters will be used to define risk indicators. Syntheses between partners wi llgather the information from different experiments and host-guild systems to build general conclusions both at guild and tree levels.
Five tasks have been planned: I- Establishing stress levels and monitoring host physiological parameters; 2 - Evaluating stress effects on tree growth; 3 - Evaluating stress effects on tree's resistance mechanisms; 4 - Assessing damage and pest/disease performances; 5 - Define tree health risk indicators
Funding SchemeCSC - Cost-sharing contracts
750 07 Uppsala