This study proposes a discrete optimal control model to obtain harvest strategies that maximize the net present value (NPV) of the timber harvested from uneven-aged Pinus nigra stands located in the ...Spanish Iberian System, between two stable positions. The model was constructed using an objective function that integrates financial data on the harvesting operations with a matrix model describing the population dynamics. The initial and final states are given by the stable diameter distribution of the stand, and the planning horizon is 70 years. The scenario analysis corresponding to the optimal solutions revealed that the stand diameter distribution does not deviate substantially from the equilibrium position over time and that the NPV for the optimal harvesting schedule was always greater than the NPV for the “sustainable/stable” harvesting strategy. The NPV increase for the different scenarios is between 5.36% and 14.43%, showing a greater increase in higher site index scenarios and higher recruitments.
: The life cycle of Tetrastichus turionum, a pupal endoparasitoid of the European pine shoot moth Rhyacionia buoliana, was studied in Spain in the field, prior to its use as a potential biological ...control agent of this pest in Chile. T. turionum showed two generations acting on the same host generation. Adults from the overwintering generation emerged and dispersed from mid‐ to late spring and gave rise to a fast developing, current year generation. Adults of this generation emerged and oviposited in early to mid‐summer, producing progeny that overwintered as fourth instar larvae inside their host. Both generations appeared highly synchronized to the presence of pupae in the host population. The role of decreasing day length in the induction of diapause is also discussed. Laboratory bioassays showed that T. turionum did not oviposit on R. buoliana larvae already parasitized by Orgilus obscurator, a major larval parasitoid, already introduced in Chile. The results reinforce the suitability of T. turionum as a promising parasitoid that would complement O. obscurator in the biological control of European pine shoot moth.
Se estudió el complejo de parasitoides de Rhyacionia buoliana Den. et Schiff. (Lepidoptera: Tortricidae) en España para su aplicación en el control biológico en Chile, mediante estudios de campo y ...laboratorio. En total se identificaron nueve especies de parasitoides en los últimos estados de desarrollo de la plaga, cinco en las orugas de últimos estadíos (Orgilus obscurator Nees, Cremastus interruptor Grav., Campoplex ramidulus Brischke, Ephialtes ruficollis Grav. y Angitia sp.) y cuatro en las crisálidas (Pimpla turionellae L., Pimpla sp., Bethylus sp. y Tetrastichus turionum Htg.). El análisis sobre las características y el comportamiento de cada uno de los parasitoides identificados condujo a seleccionar como candidato para ser estudiado con mayor profundidad al eulófido T. turionum, dado que reunió todos los atributos de un candidato prometedor: alta capacidad de localización de sus hospedantes, gran plasticidad ecológica, ausencia de cleptoparasitismo, buena sincronización con el ciclo de vida de R. buoliana, independencia de hospedantes alternativos y elevada fecundidad.
The parasitoid complex of the European pine shoot moth Rhyacionia buoliana Den. et Schiff. (Lepidoptera: Tortricidae) was studied in Spain in field and laboratory tests aimed to its use in the biological control of this pest in Chile. The species component of the complex parasitizing late developmental stages of the pest was obtained: five parasitoids larval instars (Orgilus obscurator Nees, Cremastus interruptor Grav., Campoplex ramidulus Brischke, Ephialtes ruficollis Grav. and Angitia sp.) and four parasitoids of pupae (Pimpla turionellae L., Pimpla sp., Bethylus sp. and Tetrastichus turionum Htg.). The analysis of different characteristics and behavior of each parasitoid lead to the selection of the pupal parasitoid T. turionum as the most promising candidate: good ability to locate hosts, high ecological adaptability, absence of cleptoparasitism, high synchronizing to its host, independence of alternative hosts, and high fecundity.
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