ABSTRACT Bud rot (BR) caused by Phytophthora palmivora and lethal wilt (LW) whose causal agent is unknown, are two diseases currently posing a threat to the oil palm ( Elaeis guineensis . Jacq) industry. BR, first reported in 1964, has destroyed more than 85,000 ha. LW, first reported in 1994 in the Llanos Orientales in Colombia, has destroyed more than 5,000 ha. Chlorophyll a fluorescence is useful as a provider of information about the efficiency of the photosynthetic process when plants are subjected to biotic or abiotic stresses. Oil palms affected by BR and LW showed anomalies in the photosynthetic system, manifested by reductions in Fv / F M and ΦPSII. Changes in ΦPSII, variable fluorescence yield ( Fv ) and maximum fluorescence in light-adapted leaves ( F M ’ ) were observed from the start of BR infection. The most sensitive and early indicators of LW disease were leaf temperature and basal fluorescence ( F 0 ). Fv/F 0 significantly changed in diseased palms, indicating problems with movement of electrons through the electron transport chain. Leaf temperature changed in response to both diseases, but variation was greater in LW. We concluded that damage to the photochemical system caused by the diseases affected the processes by which the plant captures and transports energy, causing a physiological imbalance in the plant reflected in the observed variations in chlorophyll a fluorescence and leaf temperature. The two parameters began to change early in the onset of BR and before visual symptoms appeared in LW, which is very important to the management of both diseases, the foundation of which is early detection.

La palmicultura colombiana comenzó una fase a gran escala de renovación de cultivo; diversos aspectos influyen en esta situación, dentro de los más relevantes está la disposición de la biomasa y su impacto en el área fitosanitaria, y la condición agroecológica debido al disturbio generado. En este documento se abordó la respiración del suelo (flujo de CO2) como variable respuesta a la renovacion del cultivo. El trabajo se llevó a cabo en el municipio de Tumaco, entre agosto de 2009 y junio de 2011, en 7 métodos de renovación y en 4 fases de desarrollo del cultivo se midió el flujo de CO2 en 12 puntos de cada parcela. Dentro de los métodos no se evidenciaron diferencias de emisión de CO2. El valor promedio fue de 929 mg CO2 m-2 h-1 (± 270,3), sin embargo a través del tiempo se encontraron diferencias significativas, esta respuesta no está relacionada con las fluctuaciones de temperatura y humedad del suelo, por lo tanto debe existir una respuesta asociada a factores bióticos (microbiota) no establecida en este trabajo. Los valores sugieren que desde el suelo de lotes en proceso de renovación se emiten cantidades considerables de carbono hacia la atmósfera, pero que van disminuyendo a través del tiempo y a su vez son ampliamente niveladas con la fotosíntesis del nuevo cultivo (14 my CO2 m-2s-1 ± 1,4 datos no mostrados), generando un balance positivo en estado global del carbono.

Colombian oil palm plantations have started a large-scale replanting phase. The replanting process has an effect on the disposal of biomass, plant health management, and agro-ecological conditions due to the disturbance that is generated. This document addresses soil respiration (CO2 flux) as a response variable of crop replanting. Seven renovation methods used in Colombia were tested. The measurements were taken over time after the disturbance and planting of the new crop. This study was carried out in the municipality of Tumaco between August of 2009 and June of 2011 using 7 methods of renovation and 4 stages of crop development. The CO2 flow was measured at 12 points in each plot. There were no significant differences for the CO2 emission among the replanting methods. The average value for respiration was 929 mg CO2 m-2 h-1 (± 270.3); however, significant differences were found over time. This response was not related to fluctuations of soil temperature and moisture; therefore, there should be an associated response to biotic factors (microbial organisms) not established in this study. The values suggested that the soil of the plots under a replanting process emitted considerable quantities of carbon into the atmosphere, but the emissions declined over time and, in turn, were offset by the photosynthesis of the new crop (14 mu CO2 m-2s-1 ± 1.4, data not shown), creating an overall positive carbon balance.