Temporal Variations in Leaf Miner, Butterfly, and Stem Borer Infestations of Cycas micronesica in Relation to Aulacaspis yasumatsui Incidence

Abstract

Four phytophagous insects are among the major threats to Cycas micronesica K.D. Hill on Guam, and the temporal comparisons of infestation levels may inform horticultural and conservation decisions. Incidence of Aulacaspis yasumatsui Takagi, Erechthias Meyrick sp., Chilades pandava Horsfield, and Dihammus marianarum Aurivillius infestations on Cycas micronesica plants were recorded every 6 months from 2004 to 2013 to determine if the incidence of A. yasumatsui was related to patterns of the other three insects. Dihammus marianarum infestations reached ephemeral maximum and minimum levels ≈2 years after A. yasumatsui infestations reached maximum and minimum levels. Erechthias sp. infestations disappeared in early 2006 when Cycas micronesica leaves were being killed by acute A. yasumatsui infestations. Erechthias sp. infestations increased thereafter as A. yasumatsui incidence declined in response to biological control. Chilades pandava infestations appeared to increase and decrease inversely with A. yasumatsui infestations throughout the years. Aulacaspis yasumatsui may be indirectly affecting D. marianarum damage by direct control of changes in overall tree health. Aulacaspis yasumatsui may be indirectly influencing Erechthias sp. through direct control over leaf longevity. The C. pandava and A. yasumatsui populations appear to exhibit direct competition with inverse patterns of incidence.