Bioassays on selection and feeding responses of Holotrichia oblita adults to different plant species

Bioassays on selection and feeding responses of Holotrichia oblita adults to different plant species were conducted both in laboratory and under field conditions. The selection response bioassay showed that the adults were significantly attracted to Ricinus communis. In paired tests of the field cages, more than 60% adults were attracted to R. communis plants, while only 35.55%, 34.45%, 33.35%, and 26.65% were attracted to plants of Glycine max, Arachis hypogaea, Ipomoea batatas, and Gossypium hirsutum, respectively. In the laboratory, the selection response percentage of the adults to R. communis leaves reached up to 93% in the presence of other host plant leaves and still arrived at 70% in the absence of other host plant leaves. Feeding deterrence bioassay showed that the adults preferred to I. batatas leaves with 229.90 ± 4.25 mg leaf consumption and 41.30 ± 5.19 mg faeces excretion after 12 h, followed by the leaves of G. hirsutum and A. hypogaea. The adult did not prefer leaves of R. communi with only 7.10 ± 0.23 mg leaf consumption and corresponding 4.00 ± 0.84 mg fecal excretion. In summary, all experimental results suggested that the attraction of H. oblita adults to R. communi is not triggered for feeding.