PARENT SESSION
1C Ecologically relevant and cost-effective toxicity test designs
9:00 AM to 7:00 PM, Monday, 07 May 2001

(M/EH016) Toxicity of Hexaconazole, Fenpropidin and Thiabendazole to Armillaria sp.

Valentim, Helena¹, Santos, Susana¹, Tenreiro, Rogério², Santos, Conceição¹, ^{1 2}

ABSTRACT- One of the actual methods to eradicate Armillaria sp. is the removal of all plants in a defined infected area and/or fumigation with the highly toxic methyl bromide. These methodologies are not only impossible to apply efficiently to forest eccossystems, but they have high costs for both producers and environment in agriculture, justifying the urgency of studying the application of systemic fungicides to fight this fungi. Testing active compounds in vitro may help to choose better substances to be applied in the field. The toxicity of three active compounds was tested by exposing Portuguese isolates of Armillaria sp. (A. mellea, A. gallica and A. tabescens) to three concentrations of those substances. Fenepropidin (used as active substance) and hexaconazole (used integrated in the commercial pesticide Anvil), reported in literature as effective on reducing Armillaria sp. growth, were compared with thiabendazole (used as a pure substance). The isolates were grown on Malt Extract Agar (MEA) supplemented with 0%; 0,04%; 0,004% and 0,0004% of each of the active compounds referred above. Hexaconazole proved to be the most effective substance, inhibiting growth even at the lowest concentration tested. Thiabendazole was the less effective as the isolates showing no effect on growth, or a small stimulation for lower concentrations, only reducing growth at the highest concentration tested. With fenpropidin the growth presented an approximately linear reduction with increasing concentrations. The most effective substances in this work will be tested in the future in in vitro plants infected with Armillaria sp.. The authors wish to thank to FCT for supporting the project Praxis XXI/P/Agr/1237/98; to Prof Natercia Santos from EFN, Oeiras for supplying the isolates and to Novartis for supplying fenpropidin.

Key words: Armillaria, hexaconazole, fenpropidin, thiabendazole