Porina flight activity and larval distribution in pastures on the West Coast of the South Island
Porina (Wiseana spp. Viette (Lepidoptera: Hepialidae)), regularly damage pastures on the South Island’s West Coast but local information useful for mitigation strategies is lacking. Flight activity of porina moths was monitored on 11 farms in the region using light traps over three summers from 2014–2017. Pastures on the same farms were sampled during winter (2015–17) to collect porina larvae. Porina moth flights typically began in October and continued through into March with peak flight activity from early December to mid-January. Wiseana copularis comprised >85% of moths captured. Wiseana umbraculata was caught regularly, representing about 10% of total catch. Observed flight patterns indicated that diflubenzuron for larval control should be applied from late February to early or mid-March for maximum impact on porina populations but exact timing should be driven by local not regional flights. Wiseana copularis was the most common species collected in pastures (265 of 267 larvae collected). One W. jocosa larva was found in 2015 and one W. umbraculata larva in 2016. No W. cervinata adults or larvae were identified. This suggests the species primarily responsible for damaging these pastures is W. copularis.