Phytosanitary monitoring of woody species from the banks of watercourses in Wallonia

  • Abras, S. , Chandelier, A. , Fassotte, C. , Lissarrague, J. , Debruxelles, N. , Dufays, E. & Cavelier, M. (2005). Phytosanitary monitoring of woody species from the banks of watercourses in Wallonia. Parasitica, 61: (2-4), 69-80.
Type Journal Article
Year 2005
Title Phytosanitary monitoring of woody species from the banks of watercourses in Wallonia
Journal Parasitica
Recnumber 611
Volume 61
Issue 2-4
Pages 69-80
Type of article PSR
Abstract The alder disease caused by Phytophthora alni has affected more than 25% of the alder trees along Walloon riverbanks. This epidemic has highlighted the fragility of the riparian ecosystem and the need to conduct phytosanitary monitoring (insect pests, mites, pathogenic fungi, bacteria and viruses) of the main woody species frequently found along the rivers and streams of Wallonia. The survey was undertaken in 2004 and 2005 on 17 species, the most dominant ones being alders, ashes, willows and maples. The objective was to provide an overview of the diseases and arthropod pests currently occurring in riverbank environments and to detect any new 'threat' to woody riverside plants. A network of more than 100 sampling units covering the southern part of the country was constituted from a database compiled by the Forestry Resources and Natural Environments Management Unit (FUSAGx). The sampling units were selected according to different criteria, notably the representativeness of each woody species, the representativeness of catchments, the watercourse categories and the geographic distribution. The survey rate reached 0.2 0/00. In each sampling unit, observations were made from the upstream side to the downstream side over a distance of 50 m around the centre of the plot, over a width of 2 m starting from the ridge of the riverbank. The plots were visited twice a year in April-June and July-October. Symptomatic plant tissues were collected and the causal pathogenic agents and insect pests were identified in the laboratory. In 2005, more than 1450 trees were examined. Many observations were related to pathogenic fungi (N=1010) and arthropods (N=4779). Generally, the phytosanitary state was found to be 'balanced'. The problems occurring in spring and summer were due mainly to larvae defoliating trees, sometimes to a significant extent (Agelastica alni). Later on, towards the end of the summer and in the autumn, some foliar and wood-destroying fungi appeared. Some diseases that can cause rapid tree decay were noted, namely the alder disease caused by Phytophthora alni, along with some types of rot (Armillaria sp.) and other wood-rotting fungi. These results were compiled in a database with information that could be relevant for epidemiological studies (weather data, environmental observations, frequency of diseases and insect pests). A provisional version of a visual guide with 51 illustrative leaflets to help identify insect and mite pests and diseases found on woody species along riverbanks was also produced as a source of information for watercourse managers.
Notes Paper presented at the symposium of AERZAP/VOFyToZ "Bilan phytosanitaire de l?année culturale 2004?2005. Fytosanitaire balans van het teeltjaar 2004?2005", 14.12.2005
Author address Rue de Liroux 4, BE-5030 Gembloux, Belgium; Passage des Déportés 2, BE-5030 Gembloux, Belgium
Authors Abras, S., Chandelier, A., Fassotte, C., Lissarrague, J., Debruxelles, N., Dufays, E., Cavelier, M.