Estimation of the extent of defoliation in Avicennia L. (Acanthaceae) caused by caterpillars of Hyblaea puera (Cramer, 1777) in a tropical mangrove

Abstract

The record of severe defoliation caused by lepidopteran larvae in mangrove forests has increased in recent decades and has caused concern because the mangrove is an ecosystem already threatened by several stressors. In this study, we used Sentinel-2 spatial data to quantify the extent and assess the health of the mangrove forest of the Mamanguape River estuary, Paraiba State, Brazil, in response to severe defoliation of Avicennia germinans and Avicennia schaueriana caused by caterpillars of the invasive exotic moth Hyblaea puera. The caterpillar outbreak was recorded in the period from May to July 2020 and satellite images referring to the years 2019–2021 were evaluated. Mangrove mapping was performed using supervised classification and forest health was assessed using the Normalized Difference Vegetation Index (NDVI). Supervised classification indicated that about 10% of the total mangrove area was intensely affected by defoliation caused by H. puera caterpillar infestation. Proportionally, the area of the A. schaueriana stand was more affected by defoliation than the A. germinans stand. NDVI indicated degraded health of the A. germinans and A. schaueriana stands in October 2020 while an improvement in biomass production was observed in June 2021. The results showed that the A. germinans stand is more resilient than the A. schaueriana stand. The consequences of severe defoliation, caterpillar characteristics, mangrove species details, and methodological issues are discussed.