Susceptibility of different forage grasses to feeding damage by <i>Prosapia bicincta</i> (Hemiptera: Cercopidae) adults in Hawaiʻi

The twolined spittlebug, Prosapia bicincta (Say), is a pest of forage and turfgrasses causing economic and ecological damage to rangelands in Hawai'i. First detected in 2016, this pest now infests >143,000 ha on Hawai'i Island. Host plant resistance is a key strategy for management of grass-feeding spittlebugs in pastures. The susceptibility of 12 different grass species and cultivars to adult P. bicincta feeding was evaluated in greenhouse trials. Grasses were arranged in a randomized complete block design and after 12 d of adult feeding, damage to the foliage was quantified and above- and below-ground dry biomass were measured. Three species/cultivars were moderately susceptible (foliar damage 28 to 41%) and 2 were extremely susceptible (foliar damage ≥80%). Kikuyu (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone), a key pasture grass used for livestock forage in Hawai'i, exhibited the highest level of susceptibility (≥85% mean foliar damage) and significant reductions in above- (38 to 50%) and below-ground (51 to 71%) biomass compared to non-infested control plants. Seven grasses demonstrated resistance, with ≤15% mean foliar damage. Among the resistant grasses, 5 were Urochloa (P. Beauv.) cultivars (Cayana, Cayman, Marandú, Mulato II, Sabiá) and the remaining 2 were Bahia T9 (Paspalum notatum (Flugge) var. saurae (Parodi) cv. 'Tifton-9') and fountain grass (Cenchrus setaceus (Forssk.) Morrone). This study is the first to identify resistance in these grasses to P. bicincta. The underlying mechanisms of resistance were not identified and necessitates further research. Hawai'i's existing Kikuyu grass pastures are severely threatened, but the incorporation of resistant grasses is a promising management strategy.