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

Fusarium wilt is a damaging disease of oil palm in Ghana. Genetic diversity of Fusarium oxysporum f. sp. elaeidis (Foe) the causal organism of the disease was studied via AFLP technique using fluorescence-based automated system for Foe isolates from Ghana in comparison with other Foe isolates from different geographical locations. AFLP was conducted using thirteen MseI primers with three sets of EcoRI primers to generate individual phylogenetic trees. A concatenated phylogenetic tree was constructed from AFLP data using the three primer pairs. Individual phylogenetic trees for each of the primers could cluster Foe isolates from Ghana distinctively from Foe isolates collected in different geographical locations. Isolates from Ghana could not be clustered under one clade for all the individual phylogenetic trees, and this was further confirmed in the concatenated phylogenetic trees for the three-primer dataset that involved 4438 and 117 random markers of polymorphic bands. The use of AFLP has shown more genetic information about Foe isolates from Ghana compared with other collections from different geographical areas. AFLP markers showed all Foe isolates from Ghana are not monophyletic.