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Western conifer seed bug (Leptoglossus occidentalis) challenging stone pine cropping in the Southern Hemisphere
Stone pine edible seeds are highly appreciated and increasingly demanded. However, kernel yield (percentage of total weight corresponding to kernel) has halved in European producing countries largely due to the attack of the invasive seed-feeding insect Leptoglossus occidentalis. In the Southern Hemisphere, where new stone pine plantations have shown positive results in terms of growth, cone production and health, the exotic seed pest L. occidentalis was first detected in 2017 in Chile, with observed changes and damages having been subsequently reported. The objective of this study was to assess cone and seed traits, and kernel-per-cone yield in P. pinea in Chile before and after the detection of the regional presence of L. occidentalis in 2017. Cone, seed and kernel traits were assessed in seven plantations from central Chile from 2010 to 2015 (before L. occidentalis arrival) and from 2018 to 2019 (after the pest arrival). For the kernels, three types of insect damage were quantified: type I (endosperm/embryo damage), type II (endosperm elimination) and type III (empty seeds). Results showed an average kernel yield of 4.0 ± 0.1%, with no differences between periods. However, in Mulchén, a significant decrease was recorded in cone weight, seed weight and kernels per cone. Regarding kernel analysis, significant increases in damage types I and II were found in all plantations after 2017. Cone assignment to weight categories showed that type I (partially damaged kernel) was the most frequent (58.6%) damage in heavy cones (>550 g), and damage type II was frequent in cones of <350 g in weight (51.4%). Thus, it is necessary to monitor the advance of the insect and its effects on stone pine cropping in non-native habitats. Given that in the southern area of Latin America stone pine is grown in managed plantations, biological and/or chemical control might be applied to limit the negative impact of L. occidentalis.
Loewe Muñoz, Verónica-Delard R., Claudia-Del Río, Rodrigo-Balzarini, Mónica
2021
Irrigation and fertilization as tools to boost growth stability of stone pine (Pinus pinea L.) plantations
Pinus pinea es una especie mediterránea que crece y se desarrolla vigorosamente en Chile. Esta especie es resistente a la sequía; sin embargo, se ha encontrado que es sensible al aumento de la aridez. Pocos estudios han reportado efectos del riego y de la fertilización en el crecimiento, pero no hay estudios detallados que consideren los efectos de ambas técnicas de manejo para mejorar la estabilidad del crecimiento. En este trabajo, las variaciones diarias del diámetro del tronco (SDV) en Pinus pinea se monitorearon durante todo un año de crecimiento utilizando dendrómetros digitales en una plantación de 31 años en Chile. Se evaluaron cuatro prácticas de manejo como herramientas para estimular el crecimiento: fertilización, riego, su combinación y control. Las series de crecimiento diario mostraron una marcada sincronía entre árboles de diferentes esquemas de manejo. El tratamiento combinado (fertilización y riego) resultó en un período de crecimiento un 25% más largo y un mayor crecimiento que el control. Durante el período de crecimiento más rápido del tronco, los incrementos diarios de diámetro fueron, en promedio, 0.06 mm para árboles fertilizados y regados, y 0.02 mm para árboles del control. Se encontraron correlaciones significativas entre los SDV estandarizados y series de variables climáticas, evidenciando que los árboles no tratados tenían la mayor sensibilidad a temperaturas extremas, lluvia y evapotranspiración potencial. La variabilidad en el crecimiento diario del diámetro del tronco de los árboles fertilizados y regados se correlacionó solo con la temperatura mínima. Los resultados resaltan la importancia de la fertilización y del riego en plantaciones de Pinus pinea para mejorar el crecimiento del diámetro y reducir la variabilidad causada por la sensibilidad a las condiciones ambientales.
Loewe Muñoz, Verónica-Del Río, Rodrigo-Delard R., Claudia-Balzarini, Mónica
2020
Effect of thinning on growth and shape of Castanea sativa adult tree plantations for timber production in Chile
Chestnut (Castanea sativa Mill.) is an interesting species for high-quality timber production. It is well known that the species responds to early thinning, but there is no information on the impact of late interventions. The objective of this study was to assess the effect of a late thinning on the performance of unmanaged adult chestnut plantations in Chile. Future-tree selective thinning and control were compared in adult plantations using a randomized complete block design with three replicates at three sites, Minas, Pillo-Pillo and Pumillahue. Tree growth was evaluated periodically during the first 7 years after thinning in all plantations. Additionally, almost 20 years after the intervention, the Pumillahue plantation was measured for growth and tree shape variables. In this case study, the effect of thinning on tree growth decreased considerably after 5 years, with a maximum DBH increment in the third year after the intervention (45.8 %, 68.6 %, and 42.2 % in Minas, Pillo-Pillo and Pumillahue, respectively). In all plantations, basal area was smaller in the thinned plots in the first years after the intervention, but in Pumillahue, 19 years after thinning, no differences were found among treatments. Height was statistically greater under thinning seven years after the intervention; this effect was also found in Pumillahue plantation 19 years after thinning. Most trees showed high vigor, and were straight and healthy, even in control plots. Late effect of thinning was observed 19 years after thinning on tree shape, with a reduction in the proportion of bifurcated trees from 16 % to 8 %. The results suggest that late thinning is an effective silvicultural intervention to produce high-quality chestnut timber in unmanaged adult plantations. Progressive and frequent thinning should be used to increase growth and improve timber production in chestnut.
Benedetti Ruiz, Susana-Loewe Muñoz, Verónica-Del Río, Rodrigo-Delard R., Claudia-Barrales M., Luis-Balzarini, Mónica
2023
Mixed Castanea sativa plantations including arboreal companion species enhance chestnut growth and high-quality timber production
Chestnut (Castanea sativa Mill.) is an important tree species for its timber, which is widely used for multiple purposes, including the veneer industry. The species has an interesting productive potential in Chile and requires specific management strategies to produce valuable, high-quality logs. Although mixed plantations including companion species usually enhance timber quality of several trees, the performance of chestnut under different associations is not well known. The objective of this study was to assess growth, survival, health, and timber quality of chestnut trees in several plantation types, including monoculture and mixtures with other companion trees and/or shrub.
Loewe Muñoz, Verónica-Delard R., Claudia-Del Río, Rodrigo-Barrales M., Luis
2023
Effect of fertilization on Pinus pinea cone to seed and kernel yields
Stone pine (Pinus pinea L.) is a species of economic interest mainly due to its pine nuts, the most expensive nut in the world. Despite the high value of pine nuts, cones are mainly harvested from unmanaged forests. Therefore, research and its applications are needed to develop nutritional management techniques among other cultivation practices intened to boost production. This study evaluated the effect of fertilization on cone production and quality (cone weight and size, number of seeds and kernels, and health status), which in turn may affect cone to seed and cone to kernel yields. Fertilization consisted of two applications of macro and micronutrients in two adult plantations twice in the growing season (in spring and fall). Morphometric variables, cone production per tree and cone health were evaluated during two years after fertilization. Fertilization effect on cone production was positive and significant in both years, with variations between years. Most of the morphometric variables were positively impacted by fertilization, including cone diameter (3.5% increase), kernel weight and length (7.7% and 2.7% increase, respectively), and total seed and kernel weight per cone (20.9% and 18.6% increase, respectively). Fertilized stone pine trees increased production and quality of cones, seeds and kernels, but did not increase cone to seed or kernel yields. However, fertilization increased type II seed damage by 45.4% and 18.9% in 2020 and 2021, respectively. The results obtained in this research may help producers adopt cultural practices to boost pine nut production.
Loewe Muñoz, Verónica-Del Río, Rodrigo-Delard R., Claudia-Balzarini, Mónica
2023

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