Biology and phenology ofCecidophyopsis psilaspis(Acari: Eriophyidae) on Pacific yew (Taxaceae)

Abstract

AbstractThe biology and phenology of the yew big bud mite,Cecidophyopsis psilaspis(Nalepa, 1893), were studied on Pacific yew,Taxus brevifoliaNutt., in British Columbia, Canada. The mite showed the typical life cycle of eriophyoids on evergreen hosts, with all stases being present throughout the year. The numbers ofC. psilaspis, which colonized both vegetative and reproductive buds, peaked in May to August, with the lowest numbers in March and October and the highest numbers in June. Mite numbers differed among bud types, with averages following the sequence terminal buds = lateral buds > male reproductive buds > axillary buds > female reproductive buds > latent buds. Very few mites were found in latent buds except during bud formation, when other vegetative buds were unavailable. Reproductive buds were colonized mostly from May to July. There was no evidence of arrhenotoky inC. psilaspis, as the proportion of mites that were females ranged from 54% to 100%. Temperature and predation were considered the likely factors that determine population fluctuations. It was hypothesized thatC. psilaspisabundance increased following favorable spring temperatures and new food resources, whereas predation by other mite species and lower temperatures, which prolonged development, were responsible for the low numbers in March and October.