Suppression of Spruce Beetle Attacks by MCH Released from Bubble Caps
Abstract The attack density of the spruce beetle, Dendroctonus rufipennis (Kirby), was reduced to 10-25% of that on untreated felled Engelmann spruce (Picea engelmannii) trees, when the trees were treated with 9-15 bubble cap release devices, each releasing the aggregation inhibitor MCH at 1-3 mg/24 h at 20°C. In the first experiment, deterioration of many release devices reduced the suppression effect. In the second experiment, MCH reduced attacks by 85%, and total brood production by 79-88%. The attacks on the MCH treated trees occurred late, as evidenced by the early stage of development of galleries and brood on these trees. Semiochemical-baited traps at untreated, or MCH-treated, felled trees caught few beetles, and had no effect on the attack density. The results show that manually applied MCH can be used operationally to reduce attacks by the spruce beetle on small groups of wind thrown trees. Mass trapping of spruce beetles is not feasible with currently known semiochemicals. West. J. Appl. For. 4(2):49-52, April 1989.