Long-term decline in the parasitism rate of passionvine hopper eggs (Scolypopa australis)

Abstract

Passionvine hopper, Scolypopa australis (Walker) (Hemiptera: Ricaniidae), (PVH) is an introduced pest of kiwifruit grown in New Zealand. Two aphelinid egg parasitoids, Centrodora scolypopae Valentine and Ablerus sp., are thought to be its most important natural enemies. Rates of egg parasitism measured during 2010–2015 in the Bay of Plenty region and in a wider survey of the North Island of New Zealand in 2015 were ≤ 10% compared with medians of about 30–50% for historical estimates. PVH eggs laid in bracken, a favored host plant, in 2015 and 2019 were parasitized at about half the rate or less than indicated by measurements made 20, 35–38 and 57 years ago. The apparent decline may have been the result of asynchrony between one or both egg parasitoids and PVH associated with warmer summer and autumn temperatures. Further work is needed to clarify the role of each parasitoid in PVH population dynamics.