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. revoluta 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.
Thomas E. Marler and Aubrey Moore
Thomas E. Marler, Ross Miller and Aubrey Moore
Container-grown Cycas micronesica seedlings were purposefully infested with Aulacaspis yasumatsui and then installed at 0, 75, or 150 cm above the ground to investigate effects of infestation height on predation by Rhyzobius lophanthae. Significantly more scales on elevated seedlings were attacked by the predator. Our results indicate that lower predation at ground level by R. lophanthae may partly explain why the predator is not effectively controlling this armored scale epidemic on Guam. Ephemeral outbreaks of A. yasumatsui documented in quarterly surveys from Sept. 2006 until Aug. 2012 confirm the inadequate biological control. Our results illuminate the importance of fully evaluating the reliance on an alien predator as a solo biological control agent for an alien pest.