Population management of cone and seed insects in spruce seed orchards

摘要

Seed orchards have been established in order to produce high quality seeds for reforestation and forestation. However, seed production in spruce (Picea abies (L.) Karst.) seed orchards is severely hampered by cone- and seed-feeding insects. Therefore it is of great importance to find methods to reduce damages from insects. This thesis summarizes and discusses results presented in four papers concerning various methods and chemicals (insecticides and a pheromone) for damage reductions in spruce seed orchards.Area-wide application of the biological insecticide Turex 50 WP was shown to reduce damage by two of the four most serious pest species. Concerns were then raised that feeding by insects that are not affected by this insecticide may increase following its application, in response to the consequent increases in the availability of food and space, resulting in little no or difference in overall damage.A follow up study indicated that there would probably not be any problem with increased feeding by the larvae survived and that spraying of an insecticide not affecting all species would probably be cost effective. However, various species-related and abiotic factors (e.g. rain and temperature) affect the efficacy of insecticide treatments, both among and within years, and thus should be taken into account.A system that would be less sensitive to weather and also may affect all pest species and at the same time avoid affecting the surrounding environment is injectable systemic insecticides. In order to increase the cost efficiency a study was performed where insecticide was combined with the flower stimulating hormone gibberellin and successfully reduced damages and increased number of flowers.In order to know if and when an insecticide application should be carried out, pheromone for trapping insects is a useful tool. But in order to do so there must be a pheromone available. During the spring of 2009 a pheromone for C. strobilella was identified and synthesized. The study showed that the amount of pheromone released from the female was extremely low, 1 pg, so the male antenna is supersensitive in order to find females. This implies also that this species can be a good candidate for mating disruption.