Biology, host preferences and fitness of Oulema melanopus (Coleoptera: Chrysomelidae), a recent invasive pest in Western Canada

The developmental parameters and fitness of a recent invasive insect pest of cereals in western Canada, the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), were compared on live plants and excised leaves of commercial cultivars of potential cereal hosts including wheat (winter and spring), oats, barley, corn, rye and triticale. Host preference and utilization within the fundamental host range of O. melanopus differed. The biological parameters differed significantly when the larvae were reared on excised tissues versus on live host plants. In both studies, wheat (winter and spring), oat (cv. Morgan) and barley were the most preferred hosts in terms of development, survivorship, adult weights and fecundity. Prolonged development with low fitness gains was noted on corn. Although the development on hosts such as rye and triticale was prolonged and adult fitness was low, the survivorship was high on these hosts. Hence, these crops can act as secondary hosts for the beetle in its new eco-region. Larvae fed foliage of Waldern, a local oat cultivar, had increased developmental time and lower survivorship compared with other cereal hosts. Despite differences in fitness gains among hosts, similar numbers of eggs were laid on all hosts. Hence, the oviposition choice of O. melanopus may not be driven by fitness gains alone and it may indicate adaptive strategy to hosts in newer environments.