Investigating organic control methods for bronze beetle (Eucolaspis sp.) in New Zealand organic apple production : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Horticultural Science at Massey University, Palmerston North, New Zealand

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Massey University
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Bronze beetle (Eucolaspis sp.), an insect native to New Zealand (NZ), is one of the most prevalent threats to the NZ organic apple industry. In organic orchards, bronze beetle can potentially damage or destroy 40-50% of the crop. At Bostock New Zealand, a large organic company that produces approximately 90% of NZ’s organic apples, the beetle causes losses of approximately ‡6 million per year. The lack of effective control methods available for use in organic production systems exacerbates the population numbers and severity of this pest. Two separate experiments were carried out to help alleviate this problematic pest. The first was a laboratory bioassay trial comparing the efficacy of three conventional insecticides with three organic insecticides containing the active ingredients spinosad (Entrust™ SC Naturalyte™ 240), pyrethrin (PYNZ28 EC), and azadirachtin (NeemAzal-T/S™ 40 EC). The objective of this experiment was to determine if any of the organic insecticides had the potential to provide an acceptable level of control in controlled conditions. If so, they should be investigated commercially. The organic insecticide Entrust SC Naturalyte (commonly called Entrust) provided over 90% control five days after application to leaves, a level of control similar to all three conventional insecticides trialled (Vayego® 200 SC, Calypso® 480 SC, and Avaunt® 300 WDG). NeemAzal-T/S, the organic insecticide containing azadirachtin, also showed some potential but at a lower level compared to Entrust, as the control achieved was over 80% seven days after direct application to leaves. The second experiment investigated the host plant attraction of bronze beetle, as it is known that they use plant volatiles to locate host plants. Based on this, apple, plum, and blackberry leaves were compared (with a clean air control) to identify which of these crops was the most attractive to bronze beetle. The purpose of this was to investigate the possibility of using these crops as attractants in a potential organic control programme. However, there were few responses to treatments, and all four treatment options appeared equally attractive to bronze beetle during this experiment, with any differences attributed to random variability.
bronze beetle, organic insecticides, efficacy, New Zealand (NZ), apple production, laboratory, host plant(s)