Implementing sanitation practices against the hibiscus bud weevil Anthonomus testaceosquamosus (Coleoptera: Curculionidae)

Abstract

The hibiscus bud weevil, Anthonomus testaceosquamosus Linell (Coleoptera: Curculionidae), is an invasive pest of tropical hibiscus, Hibiscus rosa-sinensis L. (Malvaceae). While chemical and biological control alternatives have been identified, the viability of cultural control through sanitation (collecting and destroying dropped buds where larvae complete development) remains to be explored. The impact of adult hibiscus bud weevil infestation on flower bud abortion was studied in a greenhouse. Plants were infested with one mating pair of adult weevils, with non-infested plants as controls. Actively growing buds and dropped buds were counted weekly for four weeks. A subsequent shade house experiment evaluated the effect of sanitation on plant productivity. Groups of ten plants in a tunnel tent were infested with ten hibiscus bud weevil adult mating pairs per tent. Treatments included sanitation (weekly collection of dropped buds for eight weeks) and a no sanitation control. Five actively growing buds per tent were collected in search of eggs and larvae, while counts of actively growing buds and open flowers were recorded per plant. To identify efficient sanitation methods, the time required to remove fallen buds using three methods (manual, vacuum, and blower) was estimated. Hibiscus bud weevil infestation, using two adult weevils per plant, led to a 16-fold increase in bud abortion compared to non-infested plants. Sanitation reduced the proportion of dropped buds by 22 %, while no sanitation plants showed more actively growing buds, suggesting overcompensation in response to abortion. The vacuum method was the most efficient bud removal method tested. Sanitation can be an effective, practical, and complementary measure to reduce hibiscus bud weevil infestation in commercial nurseries.