Myrtle rust, caused by the pathogen Austropuccinia psidii, affects species of the Myrtaceae, many of which are endemic to Australia and New Zealand. Originating from South America, A. psidii is now present in both countries, necessitating effective chemical control for disease management. Using an artificial inoculation protocol, the efficacy of eight fungicides (tebuconazole/trifloxystrobin, cyproconazole/azoxystrobin, fosetyl aluminum, triforine, triadimenol, oxycarboxin, copper, and tebuconazole) applied as curative or protectant treatments was tested on two native New Zealand species (Lophomyrtus × ralphii and Metrosideros excelsa). The impacts of rate (×2), frequency (single or double), and timing (pre- or postinfection) of fungicide application were investigated. Overall, the most effective fungicides tested across both species were those that included a demethylation inhibitor and strobilurin mix, notably tebuconazole/trifloxystrobin (Scorpio) and cyproconazole/azoxystrobin (Amistar Xtra). These fungicides significantly reduced infection of host plants relative to the water control. Timing of application significantly affected bioefficacy, with applications made 7 days before inoculation or 7 days after inoculation being generally the most effective. The rate of fungicide application was not significant for both host species, with few interaction terms showing overall significance. Key findings from this study will set the foundation for further fungicide bioefficacy research conducted to evaluate formulations and adjuvant mixtures, determine suitable application methods for enhanced retention and coverage, and derive optimum application time for effective protection of native and exotic Myrtaceae species in New Zealand.

Summary: We developed a Loop-Mediated Isothermal Amplification (LAMP) to detect Fusarium oxysporum f. sp. elaeidis (FOE) causal agent of fusarium wilt in oil palm. The assay was designed based on partial sequences of effector protein Secreted In Xylem (SIX8, SIX10 and SIX13) and P450 cytochrome-oxidase. The isolates used were classified as FOE, presumed-FOE and non-FOE/other Fusarium spp. based on previously published pathogenicity assay studies. The LAMP assay detected FOE DNA isolated from root tissues of oil palm seedlings. The SIX8 primers detected all FOE isolates, including other presumed-FOE and non-FOE isolates. The SIX10 and SIX13 could not detect FOE and presumed-FOE isolates. The P450 cytochrome-oxidase primer detected all isolates of FOE, presumed-FOE and non-FOE. Without isolating FOE DNA from soil, the LAMP assay could not detect FOE directly in inoculated soil. Detection time for all primers was below 30 min. Annealing derivative curves were used for assessing the level of specificity for both SIX8 and P450 cytochrome-oxidase, but none of the LAMP primers could distinguish between FOE, presumed-FOE and non-FOE isolates. This assay could be suitable for FOE detection of oil palm in nurseries and serve as an important biosecurity tool to screen oil palm germplasm exchanged between oil palm growing countries.

The most damaging disease of oil palm is Fusarium wilt caused by a soilborne fungal pathogen, Fusarium oxysporum f. sp. elaeidis (Foe). The disease is endemic to Africa and affects oil palm production there. Limited Fusarium wilt outbreaks have occurred in South America, but the disease has not yet been reported in South‐East Asia. An earlier review of Foe in 2006 provided updates on symptoms, spread and the difficulty in managing the disease. This paper updates our knowledge of oil palm, socio‐economic and environmental impacts of cultivation, Fusarium wilt disease epidemiology, Foe detection techniques, disease management strategies and biosecurity perspectives. Breeding for tolerant plant materials has significantly advanced in Africa, but financial constraints in several countries have limited the production of tolerant oil palm seed materials. Other emerging technologies for Foe control are also presented here, acknowledging the specific challenges to help inform the oil palm industry. We highlight the need to strengthen biosecurity plans in disease‐free regions. In these countries/regions that are currently free from the pathogen but cultivating susceptible plant materials, biosecurity protocols are essential to reduce threat of disease introduction and spread. Climatic change is another challenge for oil palm‐producing countries, both those currently free from the disease and those where Foe is endemic, and should be taken into consideration when planning and implementing biosecurity measures.