Using Systemically Applied Insecticides for Management of Ponderosa Pine Cone Beetle and Dioryctria Coneworms in Seed Orchards

Conifer seed orchards are used to produce high-quality seed from selected genotypes of important tree species. Two of the primary insect pests in pine seed orchards in Idaho are the ponderosa pine cone beetle, Conophthorus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), and coneworms in the genus Dioryctria (Lepidoptera: Pyralidae). We evaluated the use of two bole-injected systemic insecticides (emamectin benzoate applied at a rate of 0.07 ml active ingredient [AI]/cm dbh and imidacloprid applied at a rate of 0.1 ml AI/cm dbh) applied at two different times of the year (fall versus spring) for management of the insects in a ponderosa pine, Pinus ponderosa (Laws), orchard in northern Idaho. Bole injection of emamectin benzoate significantly reduced the percentage of cones on trees that were killed by the beetle or infested with coneworm. Both fall and spring injection periods were equally effective. There was also a lower percentage of the emamectin benzoate-treated trees that produced brood beetles. There were no differences among treatments in the percentage of brood from successfully attacked cones that survived a 7-month cold period (3-4 degrees C) or that survived for 10 days after removal from cones after the cold period. Therefore, although trees treated with a bole injection of emamectin benzoate produced a significantly higher percentage of healthy cones and fewer brood beetles, brood survival in emamectin benzoate-treated cones that were successfully attacked did not differ from brood survival in cones from trees that were not treated. Further, in a laboratory test, there was no discrimination among treatments in their acceptability to attacking beetles the spring after the fall treatment period.