Evaluating the efficacy of potential fungicide-adjuvant combinations for control of myrtle rust in New Zealand

Abstract Myrtle rust is a serious fungal disease caused by Austropuccinia psidii affecting number of Myrtaceae species in New Zealand and elsewhere. Control with fungicides or biologicals provides mechanism to reduce the build-up inoculum short-term while other strategies are being developed deployed for long-term management. This study evaluated efficacy control myrtle under controlled conditions identified adjuvants that would promote spreading fungicidal active ingredients across leaf surface. The spread fungicide on detached M. excelsa leaves was assessed applying three different combination seven fungicides. Subsequently, plants were treated fungicides/mixes, (azoxystrobin + epoxiconazole, triademinol natural tea-extract) at single rate followed inoculation A. urediniospores day 0, 7, 14 21 days after spraying. response infection based timings 7 significantly differed among treatments. azoxystrobin epoxiconazole most effective infections lower adaxial surface than abaxial, despite good coverage achieved both surfaces. There significant differences proportion infected plants. Day post-spray indicated interaction between time ratings. However, this not case either 28 35 post-inoculation. research contributes options Zealand.