Porina

Caterpillars feed autumn to winter; moths fly in spring

Porina is the caterpillar of native New Zealand moths (Wiseana species). The caterpillars live in vertical tunnels in the soil and come out at night to feed on lawns, pasture and seedlings, mostly through autumn and winter in cooler districts.

How to identify

• Greyish-green caterpillars up to 5cm, living in silk-lined tunnels in the soil
• Bare or thinning patches in lawns, worst in autumn and winter
• Seedlings and young plants grazed off at night near ground level
• Small piles of soil and frass at tunnel entrances in the morning
• Drab brown moths flying in spring and early summer, often at lights

How to prevent

• Keep lawns dense and healthy, as vigorous turf tolerates porina better
• Encourage birds and keep an eye out for the tunnels so you catch outbreaks early
• Roll or firm new lawns, which makes tunnelling harder
• Avoid sowing tender seedlings straight into porina-prone lawn edges in autumn

How to control organically

• Water the area in the evening then check tunnels with a torch and hand-pick caterpillars
• Apply beneficial nematodes to the soil to attack the caterpillars
• Protect seedlings with collars until established
• Worst in the South Island and cooler North Island districts, so time controls to autumn