Observations on the biology of the Flores weevil, Floresianus sordidus Hustache in northern New Zealand

Abstract

ABSTRACT Flores weevil (Floresianus sordidus Hustache, 1939 (Coleoptera, Curculionidae)) is now common in northern areas of the North Island of New Zealand. Historic records and new field data were investigated to learn more of the biology, seasonality, and likely pest status of the weevil. Laboratory studies were undertaken on its feeding preferences and the impact of host plant on oviposition and survival. Flores weevil adults were found to be absent in pastures from November to February and started emerging in early autumn (March), with peak emergence in April and May. Adults preferred feeding on broad-leaved plants and did not feed on perennial ryegrass (Lolium perenne L.). Mean longevity of field-collected adults in the laboratory ranged from 20 days, when provided ryegrass, to 62 days on plantain (Plantago lanceolata L.). Eggs were laid in batches of up to 20 eggs. Most eggs were laid by weevils feeding on red clover (Trifolium pratense L.) and the least by those provided ryegrass. Dissections showed ryegrass-fed weevils retained mature eggs in their ovaries. First instar larvae were found to feed on soil organic matter, whereas second and third instar larvae fed on roots. Host plant had no significant effect on larval survival or development of these stages.