Trichogramma spp. as potential augmentative biocontrol agents of Poinciana looper, Pericyma cruegeri (Butler) (Lepidoptera: Noctuidae)

Abstract

Poinciana looper, Pericyma cruegeri (Butler) (Lepidoptera: Noctuidae) is an endemic Australasian defoliator of iconic Poinciana (Delonix regia) trees. Poincianas, despite being exotic, are of significant urban value in subtropical and tropical Australia for their attractive form, flamboyant blooms and popular utility as shade and amenity trees. Poinciana looper larvae can cause extensive defoliation, reduced flowering, and become a nuisance to residents as caterpillars drop from trees, while in an urban setting, chemical control options are limited. The suitability of P. cruegeri eggs as a host for the commercially-available egg parasitoids Trichogramma carverae, Trichogramma pretiosum and Trichogramma nr. finiculatum was evaluated to determine their potential as augmentative biological control agents. One female of each of these Trichogramma species was exposed to ten P. cruegeri eggs and left for one hour to oviposit. The suitability of looper eggs as a host for each wasp species was measured by time for initial host acceptance, subsequent development time, emergence rates, egg mortality and sex ratios. All three Trichogramma species successfully utilised P. cruegeri eggs as hosts, causing an average 58 % reduction in P. cruegeri larval emergence. Female wasps generally accepted P. cruegeri eggs within one minute of introduction, and this did not differ between parasitoid species. Development time differed significantly between all three species, with T. pretiosum emerging after 14 days, and T. carverae requiring 18 days for development. Significantly more T. nr. finiculatum emerged compared with the other two species, partially due to multiple wasps emerging per host egg. P. cruegeri is a suitable host for all three Trichogramma species, but further research is required prior to embarking on a biocontrol program using these species.