Effects of new cultivars of ninebark on feeding and ovipositional behavior of the specialist ninebark beetle, Calligrapha spiraeae (Coleoptera: Chrysomelidae)

Two newly developed cultivars of ninebark [Physocarpus opulifolius (L.) Maxim.], a yellow-leaved cultivar called 'Dart's Gold' and a purple-leaved cultivar called 'Monlo', were compared with the native for resistance to feeding and oviposition by the specialist ninebark beetle [Calligrapha spiraeae (Say)]. When offered the choice between two types of ninebark, beetles statistically preferred native (P < 0.0001) and 'Dart's Gold' (P < 0.0001) over 'Monlo', but showed no preference between native and 'Dart's Gold' (P = 0.0743). Long-term performance bioassays showed significantly more eggs on 'Dart's Gold' than 'Monlo' (P = 0.0468). 'Monlo' contained the most anthoeyanins (P < 0.0001) and chlorophyll B (P < 0.0001) and the least total nitrogen (P = 0.0283) and Kjeldahl nitrogen (P = 0.0014). Anthoeyanins are known to act as feeding deterrents and bind with nitrogen, which may explain why beetles avoided feeding on 'Monlo' in preference tests.