Seasonal distribution of Herpetogramma licarsisalis (Walker) (Lepidoptera: Pyralidae) in northern Northland

The presence of Herpetogramma licarsisalis (tropical grass webworm) larvae in pasture 40 km north of Kaitaia on the Aupouri Peninsula, Northland New Zealand was confirmed in March 1999. A survey was undertaken in late March 1999 using spade sampling and sack survey techniques. The main locus of infestation (ca.37,000 ha) was centred on Pukenui, and a secondary infestation (30-40 ha) was identified 20 km south of Cape Reinga. Infestations were restricted to kikuyu (Pennisetum clandestinum) pastures. H. licarsisalis population densities declined over the winter (June - September 1999). In March 1999 larvae were present at 64% of sites sampled but by early September 1999 were only present at 7% of sites sampled. Sites where H. licarsisalis were present in July and September 1999 were characterised by well drained north facing slopes. In Northland, H. licarsisalis is at the limits of its geographical range. The possibility that this is a shortterm establishment and sporadic event is discussed.