| The Japanese beetle (Popillia japonica Newman), a polyphagous herbivore, seemingly prefers flowers to foliage of certain plant species. The nature of flower feeding and the consequences of consuming flowers were investigated. Field studies with selected hosts generally confirmed more landings on flowers than on foliage, and a preference for flowers in laboratory choice tests. Experiments with colored rose models and flowering rose bushes showed that height of blooms in the canopy, visual cues (i.e., yellow or white petals; flower size) and odor may interact to affect landing rates. Flowers and foliage of particular hosts have comparable water content, whereas foliage is higher in nitrogen content. Flowers, however, were higher in sugars, a feeding stimulant. Flowers of rose, hibiscus, and red clover areas palatable and suitable for P. japonica as linden, one of the beetle's most suitable hosts. Japanese beetles benefit from incorporating flowers into a diet of relatively poor foliage, but not when mixed with foliage of higher quality hosts.; Claims of toxic plants, and aromatic non-hosts, reported to protect roses from Japanese beetles were tested. In field experiments, odors from certain non-hosts and purported companion plants did not reduce, and sometimes increased, the number of beetles on associated roses. Toxins specific to flowers of geranium, Pelargonium spp., result in temporary paralysis of beetles that consume petals. Paralysis often results in death in the field. Although the active compounds have not been identified, my results suggest that light-activated flavonoids or anacardic acids probably are not responsible for geranium-induced paralysis. |
