Avaliação do efeito da infestação pela planta parasita Erianthemum dregei (Eckl. & Zeyh.) Tiegh na disponibilidade de nitrogénio nas tangerineiras

Abstract

Inhambane province is the largest producer of tangerines in Mozambique, with around 2.3 million plants in production. Studies recently carried out in Inhambane indicate the spread of parasitic plants with devastating effects, with the parasitic plant Erianthemum dregei being the most damaging to citrus fruits. The parasitic plant Erianthemum dregei has the capacity to perform photosynthesis, depending on the host to obtain water and nutrients. One of the essential elements for the development of plants is nitrogen, which, being extracted by the parasitic plant in tangerine trees, can affect the quantity and quality of the fruit produced. This study aims to evaluate the effect of the infestation by the parasitic plant Erianthemum dregei (Eckl. & Zeyh.) Tiegh on the availability of nitrogen in mandarin trees in the district of Jangamo in Inhambane Province, in order to contribute to the design of effective strategies for its control The study was carried out in the province of Inhambane, in the district of Jangamo. Three tangerine fields were selected, two at the administrative post in Cumbane and one at the administrative post in Jangamo, locality of Ravene. In each field, 20 tangerine trees were selected. The presence or absence of the parasitic plant Erianthemum dregei was found in the selected mandarin trees and were marked as infested or non-infested, respectively. Leaves and fruits of mandarin trees, leaves of the parasitic plant and soil samples were collected for laboratory analysis of nitrogen. The level of infestation was calculated as the percentage of infested mandarin oranges. The infestation intensity was calculated as the average of the proportion of the tangerine canopy occupied by the parasitic plant. The data were analyzed using the SAEG 5.0 statistical package and the graphs produced in Excel 2007. The results indicate that the parasitic plant is present in the district of Jangamo with an infestation level of 60% and infestation intensity of 35.83%. Field one had a higher level of infestation (80%) and a higher intensity of infestation (42.5%) and field one and field two had an infestation level of 50% and infestation intensity of 32.5% and 35%, respectively. The nitrogen in the soil of the three fields showed significant differences, with field three having the highest level (0..52) followed by field two and field one with 0.043 and 0.042, respectively. The leaves of the non-infested mandarin trees had a higher nitrogen percentage (2,792) than that of the infested plants (2,456) and the juice of the tangerines of the non-infested plants showed an average nitrogen percentage of 0.057 while the juice of the plant tangerines infested animals had an average nitrogen percentage of 0.050+. The nitrogen concentration in the mandarin tree leaves decreased linearly with the increase in the infestation index (y = 0.096x + 2,697, r2 = 0.26, p <0.01) and the nitrogen concentration in the mandarin juice also followed a negative linear relationship. with the infestation index (y = 0.002x + 0.057, r2 = 0.15, p <0.01). There is a positive correlation between the concentration of nitrogen in the leaves of the mandarin trees and the concentration of nitrogen in the juice of the tangerines (y = 0.033x-0.0033, r2 = 0.72, p <0.01). There were no significant differences between the nitrogen content in the leaves of E. dregei, in the different rates of infestation. The study concludes that 60% of the mandarin trees in the district of Jangamo are infested and that 25-50% of the mandarin canopy are found. if occupied by the parasitic plant. Infested tangerine trees have lower amounts of nitrogen than non-infested plants and the amount of nitrogen in the leaves and juice of the tangerine trees decreases with the increase in the area of ​​the canopy occupied by the parasitic plant. (TRADUÇÃO NOSSA)