Economic Damage and Host Preference of Lepidopterous Pests of Major Warm Season Turfgrasses of Hawaii

Abstract

The four major lepidopterous pests of turfgrasses of Hawaii are the grass webworm, Herpetogramma licarisalis (Walker), (GWW); lawn armyworm, Spodoptera mauritia (Boisduval), (LAW); black cutworm, Agrostis ipsilon (Hufnagle), (BCW); and fiery skipper, Hylephila phylaeus (Drury), (FS). The effects of different densities of larvae of these four insects on development of feeding injury to 'Sunturf’ bermudagrass, Cynodon magennisii (Hurcombe), were determined in 12.7 cm diameter pots in a glasshouse. Effects of diets of different turfgrasses on larval development and survival of the GWW and FS were determined in the laboratory. Complete consumption of ‘Sunturf’ bermudagrass occurred in 6-7 days with populations of greater than 3 LAW, 4 BCW, 10 FS. and 12 GWW. All population levels of LAW and BCW caused serious injury (greater than 20% of turf consumed) 4-5 days after adding third instar larvae to pots. One FS and one or two GWW larvae per pot caused only slight feeding injury. Developmental rate and survival of the GWW were poorest on 'Tifgreen’ and common bermudagrass. FS larvae developed more slowly when fed Zoysia matrella (L.) and centipedegrass, Eremochloa ophiuroides ((Munro.) Hack). All FS larvae fed St. Augustinegrass, Stenotaphrum secundatum ((Walt.) Kuntz.), died after 7-8 days.