Inter‐specific difference in budburst time and its consequences on egg hatch time and survival of the gall‐making adelgid Adelges japonicus (Monzen) (Hom., Adelgidae)

Abstract

Abstract: Temporal variation in budburst time of a host plant is important in determining the performance of gall formers. To elucidate whether synchrony of budburst and egg hatch affects the performance of gall‐forming adelgids, the phenology of gallicola egg hatch and its survival were examined in Adelges japonicus (Monzen) on three plants (Picea jezoensis var. jezoensis (Sieb. et Zucc.) Carr., Picea jezoensis var. hondoensis (Mayr) Rehder and Picea sitchensis (Bongard) Carr.) that differed in budburst time. Picea j. jezoensis is native, while P. j. hondoensis and P. sitchensis are introduced plants. Although the date of budburst differed significantly among these plants, neither the date of oviposition nor the date of egg hatch differed significantly among them; most of the eggs hatched after budburst in P. j. jezoensis, while a large portion of eggs hatched before budburst and larval gallicolae waited for the buds to open in P. sitchensis and P. j. hondoensis. To examine the effect of this asynchrony on gallicola survival, the delay of egg mass disappearance with respect to budburst was correlated with the number of gallicolae that colonized each gall. The correlation was significantly positive in P. sitchensis but not significant in P. j. jezoensis. This indicates that in P. sitchensis, gallicola survival decreases with the increasing number of eggs that hatch before budburst, while budburst phenology does not affect gallicola survival in P. j. jezoensis, which is their native host. However, when the number of gallicolae that colonized each gall was compared among the three plants, it did not differ significantly among them. This suggests that lower gallicola survival caused by a greater asynchrony of budburst and egg hatch might be compensated for by other factors (e.g. higher fecundity) that increase the number of gallicolae in the galls.