Relative Resistance of Ulmaceae for Host Susceptibility, Feeding Preference, and Suitability for the Adult Japanese Beetle (Coleoptera: Scarabaeidae)

Abstract

Laboratory feeding and fecundity bioassays, and field defoliation surveys were conducted on 73 Ulmus and eight Zelkova taxa to determine their relative susceptibility, preference, and suitability for the adult Japanese beetle (Popillia japonica Newman). Ulmus alata Michx., U. crassifolia Nutt., U. davidiana Planch., U. elliptica K. Koch,, U. glabra Hudson, U. laevis Pall., U. microcarpa, L.K. Fu, U. multinervis (syn. U. castaneifolia) Hemsl., U. parvifolia Jacq., U. propinqua Koidz., U. prunifolia Cheug and L.K. Fu,, U. rubra Muhlenb., U. suberosa Henry, U. sukaczevii Andr., U. .szechuanica Fang., U. taihangshensis S.Y. Wang, U. thomasii Sarg, U. wilsoniana Schneid., ‘Frontier’, ‘Homestead’, ‘New Horizon’, ‘Pioneer’, ‘Patriot’, U. ‘Morton’ Accolade, and U. ‘Morton’ Triumph, and Zelkova serrata (Thunb.) Mak. cultivars ‘Green Valley’ and ‘Village Green’, and Z. schneideriana Hand.-Mazz were the least susceptible to feeding and/or the least suitable for reproduction. Percent leaf tissue removed was highly correlated with field defoliation ratings, but was not a good predictor of fecundity. Asian and European elm leaves were thicker compared with North American elms, and Asian elm leaves were tougher compared with European and North American elm leaves. Host susceptibility and suitability were not related to leaf thickness or toughness. Adult female beetles laid significantly more eggs when feeding on Asian elm taxa compared with European, Eurasian, and North American elm taxa. Hybridization appears to affect host susceptibility. Results reported here provide new insight for the use of Ulmaceae taxa for future reforestation and tree breeding programs.