Infestations of Aulacaspis yasumatsui Reduce Asexual Propagation and Transplantation Success of Cycas revoluta Plants

Abstract

Cycad transplantation and asexual propagation by stem cuttings are highly successful horticultural procedures because the manoxylic stems contain copious nonstructural carbohydrates. The success of these horticultural procedures may be impaired by antecedent abiotic or biotic stress that decreases stem nonstructural carbohydrate content. The armored scale Aulacaspis yasumatsui Takagi has emerged as a global threat to cycad conservation, and the direct influence of A. yasumatsui herbivory on cycad transplantation or asexual propagation outcomes has not been adequately determined. Cycas revoluta Thunb. plants were infested with A. yasumatsui for 0, 20, or 40 weeks to determine the influence of infestation duration on transplantation or asexual propagation success. Following 20 weeks of infestation in one study, 100% of the undisturbed replications but only 60% of the transplanted replications survived. Following 40 weeks, 80% of the undisturbed replications but only 40% of the transplanted replications survived. Following 20 weeks of infestation in a second study, 100% of the intact replications but only 43% of the cuttings survived. Following 40 weeks, 86% of the intact replications and none of the cuttings survived. Leaf number and root, stem, and leaf dry weights followed similar trends, with declines in these metrics occurring with longer infestation durations. These outcomes indicated that adding the stress of asexual propagation or transplantation to C. revoluta plants that were damaged by A. yasumatsui herbivory decreased subsequent plant health and increased mortality.