Porina moth

Systematic position: Oxycanus cervinatus belongs to the order Lepidoptera, family Hepialidae. Commonly known as the Porina moth, this species is a significant pest primarily restricted to New Zealand pastures, where its larvae cause substantial economic damage.

Host crops: The larvae primarily feed on various pasture grasses, with a strong preference for ryegrass. They can also affect other turf grasses and clovers, leading to the rapid depletion of pasture quality and loss of forage biomass during high infestation years.

Biology and life cycle: The insect typically completes one generation per year. Adults emerge in autumn and lay eggs across the pasture surface. Upon hatching, the larvae create tunnels in the soil. They are nocturnal feeders, emerging from their burrows under the cover of darkness to graze on the foliage surrounding their tunnel entrance.

Damage and impact: The caterpillars shear off grasses at the soil surface, causing patches of dead or thinning vegetation. Over time, these patches enlarge and merge, often leaving the soil surface bare. This damage makes the pasture susceptible to weed invasion and reduces the total grazing capacity for livestock.

Management strategies: Controlling Porina moth involves a combination of grazing management and biological or chemical intervention. Maintaining a dense sward helps mask the insects' feeding sites. When populations reach economic thresholds, application of specific insecticides or bio-control agents like nematodes (Heterorhabditis spp.) is recommended.

• Monitoring larval populations using soil samples in early spring.
• Managing grazing pressure to ensure the sward is kept at an appropriate height.
• Encouraging natural bird predators to feed on exposed larvae.