Blue-stain fungi from pine plantations in Patagonia and their control through management

DE ERRASTI A.; RAJCHENBERG M.; PILDAIN M.B.

Punta del Este

Congreso; 1st IUFRO Working Party 7.02.13 Improving Forest Health on Commercial Plantations; 2018

Universidad de la República

Pine plantations in Argentinian Patagonia cover ca. 95,000 ha in Chubut, Río Negro and Neuquén provinces. Blue-stain fungi are the main post-harvest sanitary problem, hampering and restricting their use in international trade. We surveyed the species responsible of blue-stain and evaluated the optimal felling season and maximum storage period in order to set management control of the disease. Sawing mills and pine plantations were surveyed three consecutive years. Fungal isolates from stained logs, processed wood and insect galleries were identified based on morphological and DNA sequence comparisons of ITS and β-tubulin gene regions. Trees were felled in five representative afforested sites in winter, spring, summer and autumn, and left in the plantation; each 3 months a set of trunks were evaluated in order to measure blue-stain development, the causing agents and the associated bark beetles, if present. Fourteen species were recovered from isolations, the more frequent ones being Ophiostoma piliferum, Ophiostoma peregrinum sp. nov., Diplodia pinea and a Graphilbum sp. The exotic bark beetles Orthotomicus laricis, Hylastes ater and Hylurgus ligniperda and the weevil Pissodes castaneus were commonly associated to the different fungal taxa, the three first ones being associated to freshly cut logs, stumps and slash. At every site logs were stain-free for 3 months, no matter the season when they were harvested. After this period, harvest in spring (and sometimes autumn) was highly susceptible to ?ophiostomatoid? stain, coinciding with the beetle flying season. Summer harvest resulted critical if the stand was infected with Diplodia, because this endophytic fungus grows vigorously at high temperatures. Field trials indicated winter as the most favorable season to harvest. Ophiostoma peregrinum is possibly exotic and shows the case of a fungus that behaves aggressively in new areas, having also been recorded on logs of the native Nothofagus dombeyi.