Northern Australia is a high-risk zone for plant biosecurity due to its vulnerability to exotic pest incursions. Plant-parasitic nematodes (PPNs) are a major constraint to crop production, yet their distribution and economic impact in this region remain poorly characterized. This study presents findings from a nematode survey conducted across key agricultural regions in Northern Australia, aiming to assess the presence, distribution, and population densities of PPNs to inform biosecurity and management strategies.
From January to November 2024, a total of 159 soil and root samples were collected from 72 sites in the Northern Territory, northern Western Australia, and northern Queensland. Sites included farming areas, community gardens, and bushland. Nematodes were extracted using the Whitehead tray method and identified to the genus level based on morphological features. A total of sixteen PPN genera, spanning 14 nematode groups, were recorded. Among these, key genera such as Meloidogyne (root-knot), Rotylenchulus (reniform), Pratylenchus (root-lesion), and Radopholus (burrowing) were identified. Further species identification is ongoing through molecular diagnostics, with particular attention to economically important PPNs such as Meloidogyne spp.
Root-knot nematodes (Meloidogyne spp.) were the most prevalent, found in 48% of samples, with approximately one-third exceeding 100 nematodes per 200 mL of soil—well above hazard thresholds for crops such as cucurbits, grapes, and pineapples. The second most frequent genus, Helicotylenchus (45% frequency), included species like the banana spiral nematode (Helicotylenchus multicinctus), a major pest of banana crops in northern WA and QLD. Reniform nematodes (Rotylenchulus spp.) were present in 34% of samples, with high densities observed when pineapple crops occur. Root-lesion nematodes (Pratylenchus spp.), recorded as the fourth most frequent, pose significant risks to sugarcane, grain, and horticultural crops. Other less frequent but important genera, such as burrowing nematodes (Radopholus spp.) and citrus nematodes (Tylenchulus semipenetrans), affect grain and horticultural crops, including banana and citrus. Ectoparasitic genera like Xiphinema (dagger) and Paralongidorus (needle) were less common, but their potential for severe damage to grapevines and other sensitive crops warrants further investigation.
These findings underscore the widespread distribution of economically significant PPNs in Northern Australia, with sedentary endoparasites (e.g., Meloidogyne, Rotylenchulus) and migratory endoparasites (e.g., Pratylenchus, Radopholus) posing the greatest threats to crop productivity. The study provides crucial baseline data to support the development of region-specific biosecurity strategies and sustainable nematode management practices, including enhanced on-farm biosecurity, crop rotation, and research into biological and chemical control measures.
Keywords: Plant-parasitic nematodes, Northern Australia, Biosecurity, Crop management