A decade of biological studies of insects attacking strawberry guava (Psidium cattleianum) in its native Brazil have identified several potential biological control agents that are highly specific and damaging to their host plant, one of Hawaii’s worst invasive weeds. The most promising of these agents is Tectococcus ovatus, a leaf-galling scale insect capable of severely restricting plant growth and reproduction.

Studies completed to date indicate that T. ovatus poses no threat to related plants such as common guava (Psidium guajava) and ohia lehua (Metrosideros polymorpha). Plants growing in association with P. cattleianum were examined at field sites in southern Brazil, and only P. cattleianum and its close relative, P. spathulatum, were found attacked by T. ovatus. Members of the family Myrtaceae in Brazil not attacked by T. ovatus include P. guajava, Eugenia spp., Callistemon salignus, Eucalyptus grandis, and Pimenta acuminatus. Hawaiian plants exposed to T. ovatus in the laboratory include the natives M. polymorpha and Wikstroemia sp., and the non-natives P. guajava, Eucalyptus citriodora, Eucalyptus globulus, Melaleuca quinquenervia, Syzygium jambos, Syzygium malaccense, Lythrum maritimum, Cuphea ignea, and Cuphea hyssopifolia. None of these species were damaged by T. ovatus or permitted gall development.

Ongoing research is designed to quantify the impact of T. ovatus on varieties of strawberry guava targeted in Hawaii. Although this impact is expected to be substantial, additional efforts are needed to integrate biocontrol with other strategies for controlling strawberry guava and restoring invaded forests.