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Abundance and Population Dynamics of Adult Sphenophorus inaequalis (Coleoptera: Curculionidae) in Florida
Abstract
Abundance and population dynamics of adult Sphenophorus inaequalis were monitored at 4 bermudagrass golf courses in Florida. Sphenophorus inaequalis was present at 3 of the courses, but was the dominant billbug species at one public golf course in Gainesville, FL. Peak activity occurred from Jun to Aug in both 2006 and 2007 in Gainesville. Sphenophorus inaequalis appears to be univoltine and populations are localized within Florida.
... However, billbug species composition varies regionally, resulting in a nationwide collage of billbug species assemblages (Johnson-Cicalese 1990, Dupuy and Ramirez 2016). In recent decades, regional variation in adult species composition and seasonal phenology has been documented in Arkansas (Young 2002), Florida (Huang andBuss 2009, Huang andBuss 2013), New Jersey (Johnson-Cicalese et al. 1990), North Carolina (Doskocil and Brandenburg 2012), South Carolina (Chong 2015), Virginia (Kuhn et al. 2013), and Mexico (Ordaz-González et al 2014). However, despite high damage potential, larval populations are more difficult to characterize. ...
... Johnson-Cicalese et al. (1990) observed nearly equal abundances of these four species in cool-season turfgrasses in New Jersey, whereas in the present study, S. venatus dominated warm-season turfgrasses and S. parvulus was most abundant in cool-season Kentucky bluegrass. Such dissimilarities in billbug species composition and abundances between trapping sites within a region has also been documented in South Carolina (Chong 2015), North Carolina (Doskocil and Brandenburg 2012), and Florida (Huang and Buss 2013), and may be related to the host species present, variation in management regimes, or a combination of these factors. ...
... This is the first study investigating hunting billbug S. venatus seasonal biology in the Midwest. As in the present study, malebiased trap captures for S. venatus across the growing season has been reported in New Jersey (Johnson-Cicalese et al. 1990), Florida (Huang and Buss 2013), and South Carolina (Chong 2015). The apparently male-biased sex ratio observed in the present study (67-69% male) was most similar to findings of Johnson-Cicalese et al. (1990) in New Jersey, where 65% of the S. venatus adult population were male. ...
Eleven species of billbugs (Coleoptera: Dryophthoridae: Sphenophorus spp. Schönherr) infest managed turfgrass in North America. However, the regional variation in species composition remains unresolved and the seasonal phenology of several species has not been well documented. The latter gap is largely due to the inability to identify the larval stage to species-a confounding problem with several sympatric insect species. We used field trapping (adults) and soil sampling (larvae and pupae) surveys along with a DNA-based life-stage association to characterize the biology of billbugs associated with turfgrass in the Midwestern United States. Pitfall trapping at four locations in Indiana revealed four billbug species: S. venatus Say, S. parvulus Gyllenhaal, S. minimus Hart, and S. inaequalis Say. Sphenophorus venatus was the most abundant species on warm-season turfgrass while S. parvulus was most abundant on cool-season turfgrass. Investigation of S. venatus seasonal biology revealed two overwintered life stages-larva and adult-which resulted in two overlapping cohorts and two larval generations. Degree-day models describing S. venatus activity were more accurate for first-generation adults and larvae than for overwintering life stages. Maximum-likelihood analyses provided the first molecular species identification of billbug larvae and direct evidence that S. venatus larvae are capable of overwintering above 40°N latitude. Findings clarify the utility of molecular markers (CO1, 18S, and ITS2) for describing billbug larval population dynamics and seasonal phenology in regions where several sympatric billbug species occur. These results support the development of sustainable management strategies based on billbug seasonal phenology in different regions of North America.
... The pronotum contains an elongated diamond-shaped, nonpunctate medial area and is covered with unevenly spaced punctures that are not uniformly sized. The lesser billbug is generally lighter in color and smaller (6-7 mm in length) with the pronotum covered in larger, non-uniform, sparse punctures (Vaurie 1951, Richmond 2016 Bermudagrass in Florida (Huang and Buss 2013a). These two species, similar to the bluegrass billbug, are thought to be univoltine throughout their range (Richmond 2016, Huang and Buss 2013a). ...
... The lesser billbug is generally lighter in color and smaller (6-7 mm in length) with the pronotum covered in larger, non-uniform, sparse punctures (Vaurie 1951, Richmond 2016 Bermudagrass in Florida (Huang and Buss 2013a). These two species, similar to the bluegrass billbug, are thought to be univoltine throughout their range (Richmond 2016, Huang and Buss 2013a). ...
Species richness and seasonal abundance of billbugs (Coleoptera: Curculionidae) were determined for four golf courses in South Carolina. In 2009 and 2010, 3970 adult billbugs representing six species were collected with unbaited pitfall traps. Sphenophorus inaequalis (Say) and S. venatus vestitus Chittenden represented 95% of the billbugs collected, whereas S. coesifrons Gyllenhal, S. parvulus Gyllenhal, S. cariosus (Olivier), and S. minimus Hart composed the remainder of the billbugs captured. Adult billbugs were collected from March to December, with a sex ratio of roughly 1:1. More individuals of S. venatus vestitus and S. inaequalis were collected from March to July and August to November, suggesting two overlapping generations annually. Given the extended activity period, at least two insecticide applications may be needed to reduce the abundance of larvae and adults.
In the southeastern United States, hunting billbug, Sphenophorus venatus vestitus Chittenden, adults are often observed in turfgrass, but our knowledge of their biology and ecology is limited. Field surveys and experiments were conducted to determine the species composition, life cycle, damaging life stage, and distribution of billbugs within the soil profile in turfgrass in North Carolina. Linear pitfall trapping revealed six species of billbug, with the hunting billbug making up 99.7% of all beetles collected. Data collected from turf plus soil sampling suggest that hunting billbugs have two overlapping generations per year in North Carolina and that they overwinter as both adults and larvae. Field experiments provided evidence that adult hunting billbugs are capable of damaging warm season turfgrasses.
Billbugs (Coleoptera: Curculionidae: Sphenophorus spp.) are common pests whose damage is often misdiagnosed on turfgrass in the United States. Consequently, Florida turfgrass managers have been struggling to satisfactorily control billbug outbreaks. Thus, we sought to determine the species complex, abundance, seasonality, and fecundity of key Sphenophorus spp. from field collections, and quantify duration of developmental and daily activity periods through greenhouse rearing tests. From January 2006 to December 2007, > 18,000 adults of 10 different Sphenophorus spp. were collected from four linear pitfall traps on each of two golf courses in north central and two courses in southern Florida. Sphenophorus venatus vestitus Chittenden was the most abundant species, making up > 94% of all specimens collected from three of the four golf courses (80.9% of all specimens collected). Adults were active and mature eggs were present in female ovaries nearly every week of the year. Adults were nocturnal. S. v. vestitus development from egg to adult can occur in 8-9 wk on 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers.] or 'Empire' zoysiagrass (Zoysia japonica Steud.), with up to six overlapping generations per year, depending on environmental conditions. Thus, any time of year could be suitable to target either adults or larvae, and a repeated application may be needed to manage subsequently emerged larvae or eclosed adults.
Studies were conducted on the host plants of four billbug species (Coleoptera:Curculionidae: Sphenophorus parvulus Gyllenhal, S. venatus Chitt., S. inaequalis Say, and S. minimus Hart) found on New Jersey turfgrasses. A collection of 4803 adults from pure stands of various turfgrasses revealed all four billbugs on Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb.), and perennial ryegrass (Lolium perenne L.), and S. parvulus, S. venatus, and S. minimus on Chewings fescue (F. rubra L. ssp. commutata Gaud.). Since the presence of larvae, pupae, or teneral adults more accurately indicates the host status of a grass species, immature billbugs were collected from plugs of the various grass species and reared to adults for identification. All four species were reared from immature billbugs found in Kentucky bluegrass turf; immatures of S. venatus, S. inaequalis, and S. minimus were found in tall fescue; S. venatus and S. minimus in perennial ryegrass; and S. inaequalis in strong creeping red fescue (F. rubra L. ssp. rubra). A laboratory experiment was also conducted in which billbug adults were confined in petri dishes with either Kentucky bluegrass, perennial ryegrass, tall fescue, or bermudagrass (Cynodon dactylon Pers.). Only minor differences were found between the four grasses in billbug survival, number of eggs laid, and amount of feeding. In general, bermudagrass was the least favored host and the other grasses were equally adequate hosts. The results of this study indicate a need for updating host-plant lists of these four billbug species.
The preparation of a table or “key for determining the several species of beetles of the rhynchophorus genus Calendra in the pupa stage has been necessary in order to facilitate the study of the species involved in economic outbreaks.
The seasonal distributions and biology of four species of billbug on New Jersey turfs during 1986 and 1987 were examined; Sphenophorus parvulus Gyllenhal, a common pest of turfgrass, and three additional species, S. venatus s.l. (Say), S. minimus Hart, and S. inaequalis (Say), that had previously been overlooked as pests of cool-season turfgrasses in New Jersey. Linear pitfall trap collections of adults indicated: (1) a nearly equal overall abundance of the four species, (2) greater activity of S. inaequalis in the early spring and autumn, and (3) continued activity of S. venatus through the summer. The abundance of S. venatus adults throughout the summer, and continuous egg laying of all four species through August suggested a partial second generation. Larvae of all four species were found damaging cool-season turfgrasses during July. Laboratory-rearing work found little difference in the number of days for egg hatching and pupation, but a longer larval period for S. venatus. To facilitate identification and study by turfgrass specialists, an illustrated key to eight known billbug turf pests is provided and their geographic distributions in the United States are reviewed.
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- Sas Software
SAS SOFTWARE. 2008. Version 9.1.2. SAS Institute,
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