Laboratory efficacy of low-risk insecticides on the oriental flower beetle larvae, Protaetia orientalis

The oriental flower beetle (OFB), Protaetia orientalis, is one of the established scarab beetles in Hawaii. It was first discovered on Oahu in 2002, and since then spread to neighbor islands. The adult beetles cause damages to various landscape plants and crops, such as coconut, papaya, mango, corn, etc. This pest has become more of a concern in recent years. In this research, we investigated OFB larval mortality caused by multiple low-risk insecticides on a 7-day timescale: abamectin benzoate, acephate, azadirectin, cyclaniliprole, dinotefuran, emamectin, flupyradifurone, imidacloprid, malathion and Red Palm Weevil Killer (a.i.s clove oil, thyme oil, and sodium lauryl sulfate). Third instar larvae were used in treatments with acephate, abamectin, and dinotefuran. Second instar larvae were used for the rest treatments. A total of 384 beetles were used in this research. High (500 ppm) and low (100 ppm) rates of each chemical were tested in the experiments. There were 4 replications under each treatment, and 4 OFB larvae per replication. Among all treatments, high rate of acephate resulted in significantly high mortality at 25% on day 1, 93.8% on day 3, and 100% on day 7 post-treatment. Among the low rates, acephate was also the most effective, resulting in mortality of 12.5% on day 3, and 81.3% on day 5 post-treatment. This research is a part of our overall project in which we are also exploring biological control methods to manage OFB using entomopathogenic fungi and nematodes.