Tropical Sod Webworm (Lepidoptera: Crambidae): a Pest of Warm Season Turfgrasses Nastaran Tofangsazi,1,2 Ron
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Tropical Sod Webworm (Lepidoptera: Crambidae): a Pest of Warm Season Turfgrasses Nastaran Tofangsazi,1,2 Ron. H. Cherry,3 Robert L. Meagher,4 and Steven P. Arthurs1 1Mid-Florida Research and Education Center, University of Florida, 2725 Binion Rd, Apopka, FL 32703. 2Corresponding author, e-mail: [email protected]. 3Everglades Research and Education Center, University of Florida, Belle Glade, FL 33430. 4Center for Medical, Agricultural and Veterinary Entomology, USDA–ARS, Gainesville, FL 32608. J. Integ. Pest Mngmt. 5(4): 2014; DOI: http://dx.doi.org/10.1603/IPM14014 ABSTRACT. Larvae of Herpetogramma species (commonly called webworms, sod webworms, or grass webworms) are widely distributed throughout North America, Eurasia, Australia, New Zealand, Central and South America. Tropical sod webworm, Herpetogramma pha- eopteralis (Guenée), larvae are among the most destructive pests of warm-season turfgrasses in the southeastern United States, Carib- bean, and central America, especially on sod farms and newly established sod, lawns, athletic fields, and golf courses. Larval feeding affects the esthetics, vigour, photosynthesis, and density of turfgrass. Symptoms of infestation appear as notched and ragged grass blades with damaged areas in lawn appearing as small brown patches of closely mowed grass. Heavy infestations allow the ingress of weeds. Current control recommendations against tropical sod webworm include several cultural methods (including dethatching and cultivar selection) and the foliar application of chemical insecticides against larval stages. We summarize the seasonal biology, taxonomy, and IPM options of this important pest. Key Words: Herpetogramma phaeopteralis, St. Augustinegrass, Crambus sp., lawn pest Various species of native sod-feeding webworms in the family Cram- for this species in warm-season turfgrass. This report collates bidae (crambid snout-nosed moths) occur in North America. Species existing fragmented literature and our experiences working with commonly found on cool-season turfgrasses include the bluegrass this insect in Florida. webworm, Parapediasia teterrellus (Zincken), which is distributed over the eastern United States from Massachusetts and Connecticut Tropical Sod Webworm west into Colorado and through mid-Texas and eastward but most Taxonomy. Nine species of Herpetogramma occur in North Amer- abundant in the limestone districts of Kentucky and Tennessee where ica. These small, brownish moths are frequently collected at light Kentucky bluegrass (Poa pratensis) is dominant; the western lawn traps. However, some species are highly variable in wing pattern moth, Tehama bonifatella (Hults), which is found west of the Rocky shading, and possess conservative genital structures in both sexes. Mountains and along the Pacific Coast, western Canada into Alaska; This led to many species being independently described multiple times the striped sod webworm or changeable grass-veneer, Fissicrambus (Solis 2010). Tropical sod webworm was formerly classified in the mutabilis (Clemens), which is found from New York to Florida, west family Pyralidae along with other sod webworms in the genus, Cram- bus. According to a recent systematic revision, this species was moved to Illinois to Texas and north to Ontario; and the larger sod webworm, to the subfamily, Spilomelinae, and family, Crambidae (Solis 2010). Pediasia trisecta (Walker), which ranges from southern Canada south Synonymies associated with H. phaeopteralis in the literature include into North Carolina and west into Tennessee, Texas, New Mexico, Botys phaeopteralis (Guenée), Botys vecordalis (Guenée), Botys ves- Colorado, and north to Washington State (Global Biodiversity Infor- talis (Walker), Botys additalis (Walker), Botys plebejalis (Lederer), mation Facility database; North American Moth Photographers Botys cellatalis (Walker), Botys communalis (Snellen), Botys intri- Group; Heppner 2003, Brandenburg and Freeman 2012). catalis (Möschler); Acharana descripta (Warren) is designated as a The tropical sod webworm, Herpetogramma phaeopteralis new synonym of H. phaeopteralis. (Guenée), occurs exclusively in warm-season turfgrasses. This species Pest Status. The tropical sod webworm is among the most common occurs from South Carolina to Florida and the Caribbean, and west to caterpillar species causing economic impact to turf through direct Texas, and south through central America (Fig. 1). A related species, damage and control costs in the southeastern United States. It nor- the grass webworm, Herpetogramma licarsisalis (Walker), occurs as mally occurs in a pest complex that includes the fall armyworm, an important pest of turf and some other grass crops in Hawaii, Spodoptera frugiperda (J. E. Smith), striped grass looper, Mocis spp., Australasia, and Southeast Asia (Tashiro 1976, Grant 1982, Barrion and fiery skipper, Hylephila phyleus (Drury) (Fig. 3; Brandenburg and and Litsinger 1987). As an easy diagnostic characteristic, these Her- Freeman 2012). Tropical sod webworm is most damaging in newly petogramma webworms hold their wings out flat when at rest, established turf with higher fertility levels (Trenholm and Unruh whereas all other North American webworms partially fold their 2004). Stakeholders impacted by this pest in the southeastern United wings around their body, giving them a tube-like appearance (Fig. 2). States include sod producers, lawn care professionals, golf course Eggs of tropical sod webworm are flattened and laid in small clusters superintendents, and athletic field managers. These industries are well on leaf surfaces, whereas other webworms drop ridged, barrel-shaped represented with economic impacts of over US$3 billion in Florida eggs at random as they fly over the grass; larvae may generally be alone (Haydu et al. 2006). However, to our knowledge, the specific distinguished by the different patterns of plates (panicula) on their economic impact of tropical sod webworm has not been calculated. thoracic segments (Kerr 1955). Life History. Adult tropical sod webworm communicate via sex Currently, relatively little published information exists for pheromones with virgin females lacking an obvious calling posture many of these webworm species, although they collectively com- and mating occurs 3–4 h before sunrise (Meagher et al. 2007). We prise an important pest complex of turf. Here we present an have observed tympanic and associated chordotonal organs in moths, overview of the tropical sod webworm ecology and field identifi- which suggest ultrasonic courtship behavior. However, we have not cation and discuss integrated pest management (IPM) approaches confirmed the release of acoustic signals from males of this species as 2 JOURNAL OF INTEGRATED PEST MANAGEMENT VOL. 5, NO. 4 Fig. 1. Distribution and seasonal occurrence of tropical sod webworm, Herpetogramma phaeopteralis, based on reports of adult specimens. Source: North American Moth Photographers Group (NAMPG; mothphotographersgroup.msstate.edu) and the Global Biodiversity Information Facility database (gbif.org). has been noted among other Crambidae (Nakano et al. 2008, Taka- through November; Cherry and Wilson 2005). Populations decline nashi et al. 2010). Adults live for 10–14 d when provided 5% vol:vol over the winter and increase slightly March through May. In central honey water in greenhouse cages and likely nectar-feed on flowering Florida, the authors have observed adults from May through Novem- plants. Sourakov (2008) noted this species feeding on extra floral ber. In more northern regions of Florida (Gainesville), the peak of nectaries of passion vines, Passiflora incarnate (L.). The presence of flight activity was reported in October and November (Kerr 1955) and both flowers and extra floral nectaries on plants with such structures, August through October (John Capinera, personal communication). such as Ipomoea (Convolvulaceae), will support the flight ability, Indications are that this species does not survive the winter in the longevity, and fecundity of the adult moth as well as some of its northern part of the state (Kerr 1955). Based on the observed patterns natural enemies (Rudgers 2004, Wäckers et al. 2007). of abundance, we speculate that some gradual seasonal migration of We have observed that adults have a high preference to reside in this species may occur from southern into northern Florida during the tall grass (Cherry and Wilson 2005) and shrubs during the day and are late spring and early summer. most active at dusk. Females deposit eggs on grass blades in the evening and eggs hatch in4dat25°C. Tropical sod webworms develop through six larval instars and the pupal stage lasts from 21 to Description of Life Stages 47 d, depending on temperature. The lower, upper, and optimum Eggs. Adult females deposit clusters of 10–35 creamy-white eggs thermal thresholds for egg–pupae were 15, 35, and 30°C, respectively on the upper surface of grass blades (Fig. 4). Eggs are flattened, (Tofangsazi et al. 2012). overlapping, slightly oval, and measure 0.7 mm (length), 0.5 mm Multiple generations of this species may occur in a year; the (width), and 0.1 mm (height). Eggs are pale white when laid and authors have observed four or more generations per year in southern become brownish-red as they mature. The duration of the egg stage is Florida. In southern Florida, tropical sod webworm adults are present variable with temperature, ranging from 29.6 d at 15°C to 3.2 d at year round, with significantly higher numbers in the fall (September 30°C (Tofangsazi et al.