Estimation of extent of the mangrove defoliation caused by insect Hyblaea puera (Cramer, 1777) around Dharamtar creek, India using Sentinel 2 images

Abstract

Mangroves have been continuously affected due to human-induced and natural stresses. Therefore, reliable, accurate, and timely mangrove information is essential for conservation, protection, and sustainable management. Recent advances in remote sensing technology have provided an opportunity to observe and monitor mangroves spatially and temporally. Remote sensing technology could detect and acquire information like mangrove extent, cover change, species composition, canopy density, mangrove biomass, and carbon sequestration. In this study, European satellite Sentinel-2 data was used to map the defoliation of mangroves of Dharamtar creek, India, caused by the insect ‘teak defoliator’ (Hyblaea puera). Defoliation from the study area was recorded from August 2019 to October 2019. Mangrove plant Avicennia marina is the most dominant species distributed across the forest, and it was the only species observed to be infested. The total area of mangroves of Dharamtar creek was estimated to be 8175.5 ha. Out of the total mangrove area, high defoliated, moderately defoliated, low defoliated and very low defoliated and un-defoliated mangrove areas were estimated as 6.6%, 9.9%, 8.3%, 50.17% and 25.0%, respectively. The infestation was affected more than 6,000 hectares of mangroves. Unhealthy and stressed mangroves due to defoliation caused by the infestation of H. puera were detected using NDVI in the study area. The details regarding the moth, infestation of mangroves, its causes, impacts and other related information was discussed. We recommend further studies to investigate the causes of outbreaks, preference of this insect to this particular species of mangroves over other species and other implications of defoliation.