RESUMENSe determinó el potencial y la eficiencia de producción de semilla de Pinus engelmannii Carr. en tres rodales semilleros: El Encinal y Las Cumbres, municipio de Durango, Dgo. y La Florida, municipio de San Dimas, Dgo. En cada rodal se seleccionaron 10 árboles, con una separación mínima de 50 m; de cada árbol se colectaron 10 conos, éstos fueron secados al aire libre para desprender las escamas y cuantificar potencial productivo, semillas desarrolladas, óvulos abortados en el primero y segundo año de desarrollo, y escamas infértiles superiores e inferiores. De cada rodal se escogieron al azar 400 semillas, a las cuales se les hicieron pruebas de rayos X para cuantificar: semilla llena, vana y dañada por insectos; además, se determinó su germinación. Se encontró que en el rodal El Encinal existió el más alto potencial productivo con 171,9 semillas por cono, así como de semilla desarrollada con 143,7 semillas por cono. En Las Cumbres se registraron los mejores valores de semilla llena (77,2%) y de germinación (98,1%). El mayor aborto de óvulos en el primer año ocurrió en La Florida con 38,2 semillas por cono, lo que refleja autopolinización o daño por Leptoglossus occidentalis Heidemann en las primeras fases de desarrollo de la semilla. El daño por insectos más intenso se observó en El Encinal con 7,0% de la semilla afectada. La mayor eficiencia de producción de semilla se encontró en Las Cumbres con 66,9%, mientras que en El Encinal y La Florida el porcentaje fue menor a 41,0%.PALABRAS CLAVE: Germinación, insectos de conos y semillas, potencial productivo, rayos X, semillas desarrolladas. ABSTRACTThe potential and efficiency of seed production of Pinus engelmannii Carr. it was determined in three seed stands in the state of Durango (El Encinal and Las Cumbres, municipality of Durango, and La Florida, municipality of San Dimas). In each stand, 10 trees were selected, separated by a minimum distance of 50 m; from each tree 10 cones were collected, they were air-dried to loosen the scales and then quantify: productive potential, developed seeds, ovule abortion in the first and second year of development and, infertile upper and lower scales. In each stand, 400 seeds were randomly chosen and then X-ray tested, to measure: full seed, vain and damaged by insects. Moreover, through germination tests, speed and capacity of germination were determined. It was found that at the stand El Encinal existed the highest potential production with 171.9 seeds per cone and also the best seed developed with 143.7 seeds per cone. At Las Cumbres, the best values of filled seed (77,2%) and germination (98,1%) were found. The largest ovule abortion in the first year occurred in La Florida with 38,2 seeds per cone, reflecting autopollination or damage by Leptoglossus occidentalis Heidemann in the early stages of seed development. The most intense insect damage was observed at El Encinal with 7,0% of affected seed. The largest seed production efficiency was found at Las Cumbres with 66,9%, while in El Encinal and La Florida the perc...

Mexican dwarf mistletoe (Arceuthobium vaginatum subsp. vaginatum, Viscaceae) is the most widespread and damaging parasitic plant in Mexico. It parasitizes 10 species of pines (Pinus spp., Pinaceae) as principal hosts, including Pinus cooperi, one of the economically most important pines in the state of Durango. As a case study, we used stem analysis to estimate the effects of Mexican dwarf mistletoe on volume and height growth of dwarf mistletoe‐infected P. cooperi in western Durango (Ejido El Brillante, Municipality Pueblo Nuevo). This case study sampled a total of 48 trees, 12 in each of four infection classes estimated using the 6‐class dwarf mistletoe rating system (DMR): uninfected (DMR 0), lightly infected (DMR 1–2), moderately infected (DMR 3–4) and severely infected (DMR 5–6). Significant reductions in both volume and height growth were found for moderately and severely infected trees when compared to uninfected trees. On average, reductions in volume growth and height growth were as high as 50% and 17%, respectively. The largest growth reductions were for moderately infected trees, but large growth reductions also occurred for severely infected trees. Because of the reduced growth associated with moderate to severe infection, Mexican dwarf mistletoe‐infested pine forests in Durango, where timber production is a high priority, should be managed using harvesting practices that reduce dwarf mistletoe infection, and thereby, increase forest productivity.

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The subtribe Diabroticina is a large group of New World Chrysomelidae that includes corn rootworms, cucumber beetles and other pests. Recent introductions of Diabrotica virgifera virgifera LeConte into Europe, and the development of resistances to current management practices of rootworms in the USA have increased interest in new sustainable options for managing those pests. The only parasitoids that have been shown to consistently target and develop inside the beetle adults are Centistes gasseni Shaw, Centistes diabroticae Gahan (both Hym.: Braconidae), and Celatoria diabroticae Shimer, Celatoria compressa (Wulp), Celatoria bosqi Blanchard, and Celatoria setosa Coquillett (all Diptera: Tachinidae). This review improves our understanding of the realised and potential host range of these known parasitoids by rectifying erroneous references in light of new host records and from laboratory host range tests. Based on this critical review, all tachinid and braconid species studied are considered to be specific at least to the level of subtribe, i.e. Diabroticina. Celatoria setosa, Celatoria diabroticae and C. bosqi, have a narrow realised and potential host range; the former is restricted to the genus Acalymma and the last two to the fucata and virgifera groups of the genus Diabrotica. The braconids Centistes gasseni and C. diabroticae are also specific. The realised host range of C. gasseni includes species in the Diabrotica fucata and virgifera groups; while its potential host range also includes Acalymma species. The realised and potential host range of Centistes diabroticae includes Acalymma species as well as species in the fucata and virgifera groups of Diabrotica. Celatoria compressa has the broadest realised range compared to the other species studied, since it was obtained from species in several genera of Diabroticina; and its potential host range may also include Old World Aulacophora species.

El presente estudio consistió en la elaboración de una guía para el manejo de la densidad de Pinus cooperi var ornelasi en el estado de Durango, México. S e utilizó una metodología basada en la evaluación de la densidad en que se encontraron árboles de diferentes clases de copa. La línea de cierre de copas se alcanzó a un índice de densidad de Reineke, con un diámetro de referencia de 25 cm, de 310.31, la línea de árboles dominantes a un IDRR de 658.62, los intermedios a 720.18 y los suprimidos a un IDRR de 1,007.05. Estas líneas determinan posibles rangos de densidad en los cuales un rodal de Pinus cooperi de igual edad puede ser manejado. La metodología utilizada en el presente estudio ofreció resultados similares a los encontrados para otras especies de pinos en México.