Generalist Predators for Pest Control in Macadamia Orchards

The Australian macadamia industry is countering its major challenge of insect pest pressure by considering Integrated Pest Management (IPM) to control pests. The aim of my project is to develop a key IPM tool, Conservation Biological Control, by identifying predator-prey interactions in Macadamia orchards. In this project we focused on 1) documenting the macadamia invertebrate community early and late season using surveys and cameras; 2) identifying which predators attack which prey by using genetic techniques; and 3) testing the effect of Intraguild predation on pest control.

This study reveals that spiders, lacewings, ants, coccinellid beetles, hoverflies, assassin bugs, damsel bugs, mantises and katydids could be potential predators to control the pests of macadamia. The camera survey revealed that spiders, brown lacewings, ants, and hoverflies were associated with lace bugs and therefore were potential predators. The current survey revealed that the farm with a low spray regime showed a higher diversity of predators compared with farms with high spray regimes.

Single nucleotide sequencing confirmed the identification of predators that were used in the metagenomic analysis. However, genomic information revealed that of the one field collected predators, the green lacewing, was a different species (Mallada yangae) from that expected and supplied by pest management specialists (Mallada signatus). Metabarcoding results showed that field collected predators (spiders and lacewings) both consumed Fall Armyworm and aphids in maccadamia orchards, and therefore have the potential to reduce the abundance of these pests.

Predator species usually reduced pest numbers when tested on their own or in combination with other predators in the predator-prey interaction experiments. However, exotic green lacewings (M. signatus) were unparalleled in their ability to reduce survival of aphids, FAW, and lace bug nymphs. Green lacewing larvae supplied by BioResources reduced the lace bug nymph survival significantly. Multiple predators were as effective as single predators in pest control but not significantly different from individuals. Intraguild predation between predators (spiders and green lacewing, and among green lacewings) was not detrimental to pest control. My results highlighted that the predators within macadamia could have potential for controlling pests, but they may need support from augmentation with exotic predators.