The attack was observed in 2020 and became massive in 2022 in the Betsiboka estuary. The culprit is a defoliator caterpillar Hyblaea puera (Cramer, 1777) that specifically attacks the mangrove tree Avicennia marina that constitutes the monospecific stand of mangroves downstream of the Betsiboka delta.
The DiDEM/Deltas-Madagascar team was mobilised by the Boeny region to assess the situation. A mission by two entomologists from CNRE and a survey of the damage in the delta (IRD-CNRE), from 16 to 22 May 2022, provided some diagnostic elements (see DIDEM/Deltas-Madagascar report No. 10 in french). Monitoring by the SENTINEL2 satellite has also made it possible to reconstruct the dynamics of defoliation since the first attacks in 2020, on the basis of negative anomalies in the NDVI indicator (loss of chlorophyll activity).