Hunting Billbug (Coleoptera: Curculionidae) Resistance Among Zoysiagrass (Zoysiaspp.) Cultivars

Abstract

Hunting billbugs (Sphenophorus venatus vestitus Chittenden) cause damage to zoysiagrass (Zoysia spp.) and bermudagrass (Cynodon spp), which is often misdiagnosed as the effects of drought, disease, or another soil insect. Populations have increased over the past several decades and are causing extensive damage on grasses in lawns, golf courses and other land-scapes. Nine cultivars of Zoysia were evaluated for resistance to S. venatus vestitus in a field cage choice test in a paired cage split-plot experiment. Leaf-firing of plant canopy was considered an above ground expression of root feeding damage by billbug larvae. ‘Diamond’ and ‘Zorro’ exhibited significantly less leaf firing damage (a reduction of 6.1 and 9.8%, respectively). In contrast, ‘Palisades’, ‘Meyer’, and ‘Crowne’ showed >40% canopy damage. When root, shoot, and total plant dry weights were compared, ‘Diamond’, 'Zorro’, ‘Cavalier’, and ‘Royal’ [all Z. matrella (L.) Merr.] sustained less dry weight reduction (<53%) than ‘Palisades’, ‘Meyer’, and ‘El Toro’ (all Z. japonica Steud.) with 76, 74, and 70% total dry weight reductions, respectively. Cultivars of Z. matrella appear to be more resistant as a group than the Z. japonica cultivars.