Development of a cost-effective, pesticide-free approach to managing African black beetle (Heteronychus arator) in Australian eucalyptus plantations

Screening trials were established to test the efficacy of a range of physical barriers in preventing damage to stems of Eucalyptus globulus seedlings growing in Australian commercial eucalypt plantations by African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae). Seedlings treated with two types of barrier covering the lower section of stem were significantly less likely to be damaged than untreated controls. In contrast, chlorpyrifos treatments conducted within the same plantations as part of operational control programs did not appreciably reduce damage incidence, although pitfall trap captures in chlorpyrifos treated areas were consistently below those for untreated controls. One barrier, a flexible plastic mesh sleeve, was further tested in large trials as part of an operational planting program. In this less controlled commercial production setting, this barrier proved both practical and effective, with severe damage and mortality reduced by over 75%. No negative treatment effects on root formation, or tree growth, were observed. There was a statistically significant correlation between pitfall trap captures in the 2 months prior to planting and the level of damage sustained in the six months following planting. However, there was considerable variation around this trend suggesting pitfall captures alone cannot be used as a reliable indicator of risk. Barrier treatment has proven highly cost-effective and is now the operational standard. It is conservatively estimated that, in just 3 years of wider use, over 5500 ha of ‘high-risk’ land has been planted to barrier treated seedlings.