Use of Expert Elicitation to Quantify Pasture Losses and Economic Costs of Invertebrate Pests in South‐Eastern Australian Dairy Farms

ABSTRACT Invertebrate pests cause considerable damage to pasture‐based production systems each year. However, their economic cost in industries such as Australian dairy has seldom been quantified due to the prohibitive cost and logistical challenges of measuring damage at regional scales. We developed a structured expert elicitation (EE) process to identify major invertebrate pests in four key dairy regions of south‐eastern Australia (northern Victoria, south‐west Victoria, Gippsland and Tasmania), quantify their impact on pasture dry matter (DM) production, and estimate associated economic costs using the agricultural economics acquisition value technique. Across the regions, 11 invertebrate groups were identified as economically important. Redlegged earth mites, lucerne flea, blackheaded pasture cockchafer and other cockchafer species were consistently among the most costly pests, while other pests were more region specific, such as blue oat mites in northern Victoria and the winter corbie and slugs in Tasmania. Estimated pasture losses under high pest abundance ranged from 1.0–6.9 t DM/ha. When considering the most damaging pest (or group) in each region, costs ranged from $115–210/ha in northern Victoria, $200–360/ha in south‐west Victoria, $235–495/ha in Gippsland and $375–745/ha in Tasmania. Our analyses highlight the importance of pest abundance, timing of losses (e.g., autumn versus spring) and the value placed on pasture in determining economic impact. These findings, which are broadly analogous with earlier research, provide the first region‐specific estimates of pasture losses and costs from invertebrate pests in the Australian dairy industry, offering a foundation to guide future research, extension and management priorities.