Scarab infestations have been an ongoing concern for growers,...

Scarab infestations have been an ongoing concern for growers, particularly in the Lakes and Kondinin regions, where root and crown feeding has led to significant crop damage and failures. Though sporadic, outbreaks have resulted in substantial yield losses. More recently, barley crops in the Great Southern Agricultural Region have also been affected, with some paddocks experiencing 5-6% plant loss due to persistent larval feeding.
Effective management of scarabs is complicated by the diversity of species, each with distinct life cycles, behaviours, and responses to control measures. Accurate species identification is critical, as some larvae remain below the soil surface-rendering contact insecticides ineffective-while others are beneficial and should not be targeted. Additionally, growers face increasing restrictions on chemical control options, including the loss of chlorpyrifos. Overuse of broad-spectrum insecticides contributes to resistance development and harms beneficial insect populations through off-target effects.
Preliminary analysis by DPIRD on scarabs collected from Lake Grace found no genetic matches in GenBank or Bold databases, suggesting the presence of previously undescribed species. This discovery led to a variation within the NGDSI (DPIRD) project to:
1 Develop molecular characterisation techniques for identifying cockchafers across all life stages.
2 Map the potential distribution of key species across WA.
3 Focus management strategies on species that are complex ground occupiers.
This project will build on and complement the NGDSI variation by bridging species identification with practical pest management solutions. While the NGDSI work focuses on refining molecular tools and mapping species distribution, this project will develop targeted management strategies-including chemical and agronomic approaches-tailored to the specific scarab species present in key hotspots such as Lake Grace and Kondinin. By linking species-level insights with actionable control measures, these efforts will provide growers with integrated, evidence-based tools to mitigate scarab damage, enhance crop protection, and reduce reliance on ineffective chemical treatments, ultimately supporting more sustainable and effective pest management across WA's agricultural regions.