Prosapia bicincta (Hemiptera: Cercopidae) abundance, host plant associations, and impacts on ground cover in Hawai'i Island rangelands

Authors: WILSON, SHANNON - University Of Hawaii; THORNE, MARK - University Of Hawaii; Johnson, Melissa; PECK, DANIEL - Vestaron Corporation; WRIGHT, MARK - University Of Hawaii

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: This is the first study to quantify abundance and host plant associations for Prosapia bicincta in Hawai'i, and estimate its impacts on vegetative cover in Kona pastures. Five years of field surveys revealed wet season months (April-October) consistently had significantly higher TLSB abundance relative to dry season months (November-March) and most activity was detected at mid-elevation pastures located between 1,000-1,300 m a.s.l. We also observed a steady increase in abundance during the first three years of surveys, followed by a decline in populations perhaps associated with host feeding, local variability in climate conditions, and/or dispersal behavior. Grasses accounted for 72% of the plants P. bicincta nymphs were detected on. Pastures located between 1,000-1,300 m a.s.l. in elevation, where P. bicincta activity was highest, had the biggest decrease in mean grass cover and greatest increase in forb and shrub cover. These results show areas with high P. bicincta infestations experienced severe grass dieback of key pasture grasses for livestock forage, suggesting damage caused by this pest may provide entry for the establishment of weedy forbs and shrubs and decrease the likelihood of grass recovery. This information will provide a basis for estimating P. bicincta developmental rates to properly time management practices and target vulnerable stages of the lifecycle.

Technical Abstract: The twolined spittlebug (TLSB, Prosapia bicincta Say) is native to the southeastern U.S. and considered a major economic pest of forage grass and turfgrass. TLSB was first detected in rangelands on Hawai'i Island in 2016 and has since spread to an estimated 72,000 hectares in the Kona district. This study aimed to quantify TLSB abundance, host plant associations, and impacts on ground cover over time. Monthly surveys were conducted from February 2018-September 2022 along 17 established 100 m transects at four ranches located in the Kona district of Hawai'i Island, spanning an elevation gradient from 519 to 1,874 m a.s.l. Monitoring revealed that TLSB occurs from 519 to 1,679 m in elevation, primarily in Kikuyu grass (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone) pastures. Peaks in TLSB abundance coincided with the wet season, with most activity occurring from April-October and little to no activity between November-March. Mid-elevation transects had significantly higher mean TLSB abundance (126 nymphs/m2) relative to low- (64 nymphs/m2) and high-elevations (20 nymphs/m2). Sites with the highest abundance of TLSB were also observed to show the greatest decrease in mean grass cover (30%). Grasses accounted for 72% of the total TLSB detections, with the remaining host plants comprised of legumes (16%), sedges (6%), and forbs (6%). Twenty of the plant species were new host records for TLSB. Information on TLSB host plant associations and seasonality under local conditions will help to improve the effectiveness of integrated pest management (IPM) to suppress populations below economic thresholds and sustain livestock production.