Cryptic scale infestations on Cycas revoluta facilitate scale invasions

Abstract

The cycad aulacaspis scale (Aulacaspis yasumatsui Takagi) has invaded numerous geographic regions in the past 15 years. The sequential invasions have decimated many Cycas nursery and landscape industries and threatened C. micronesica K.D. Hill and C. taitungensis C.F. Shen, K.D. Hill, C.H. Tsou and C.J. Chen within their native habitats. The majority of the international cycad trade is dominated by Cycas revoluta Thunberg. We removed dense tomentum that characterizes C. revolute cataphylls and excised intact leaf bases from stems of landscape C. revoluta plants to expose hidden surfaces. Additionally, we removed the root system from containers on nursery plants to reveal enclosed roots. All three organs were infested with cycad aulacaspis scale on tissue surfaces that cannot be detected during thorough visual inspection of intact plants. These unique concealed infestations allow this species to vector scale insects in a cryptic manner on cataphyll, stem, and root surfaces. This information lends support for a policy of strict prohibition of imported C. revoluta plants from countries known to have cycad aulacaspis scale infestations.