Mangrove Dieback and Leaf Disease in Sonneratia apetala and Sonneratia caseolaris in Vietnam

Abstract

Even though survival rates for mangrove restoration in Vietnam have often been low, there is no information on fungal pathogens associated with mangrove decline in Vietnam. Therefore, this research was undertaken to assess the overall health of mangrove afforestation in Thanh Hoa Province and fungal pathogens associated with tree decline. From a survey of 4800 Sonneratia trees, the incidence of disorders was in the order of pink leaf spot > shoot dieback > black leaf spot for S. caseolaris and black leaf spot > shoot dieback > pink leaf spot for S. apetala. Approximately 12% of S. caseolaris trees had both pink leaf spot and shoot dieback, while only 2% of S. apetala trees had black leaf spot and shoot dieback. Stem and leaf samples were taken from symptomatic trees and fungi were cultured in vitro. From ITS4 and ITS5 analysis, four main fungal genera causing leaf spots and shoot dieback on the two Sonneratia species were identified. The most frequently isolated fungal taxa were Curvularia aff. tsudae (from black leaf spot),Neopestalotiopsis sp.1 (from stem dieback), Pestalotiopsis sp.1 (from pink leaf spot), and Pestalotiopsis sp.4a (from black leaf spot). The pathogenicity of the four isolates was assessed by under-bark inoculation of S. apetala and S. caseolaris seedlings in a nursery in Thai Binh Province. All isolates caused stem lesions, and Neopestalotiopsis sp.1 was the most pathogenic. Thus, investigation of fungal pathogens and their impact on mangrove health should be extended to other afforestation projects in the region, and options for disease management need to be developed for mangrove nurseries.

Phenomenon and Mechanisms of Sonneratia apetala Introduction and Spread Promoting Excessive Growth of Derris trifoliata

“…For example, in areas lacking rivers, certain dynamics may not be as apparent [28]. Additionally, owing to the limited duration of this study, we may not have captured changes in long-term ecological processes, such as mudflat elevation [29], soil nutrient accumulation [30][31][32][33], allelopathy [34], light impact [35,36], adaptability to salinity [37][38][39], natural enemy factors [40,41], gene differentiation [42], etc. Hence, further research should encompass a broader geographical scope and longer time scales to obtain a more comprehensive understanding.…”

New and Emerging Insect Pest and Disease Threats to Forest Plantations in Vietnam

“…The remaining 1,158,000 ha includes mangroves, other bamboo species, small monocultures of other native species, and some mixed forests. At present, there is no national strategy to investigate the health of these forests even though tree mortality has been observed [102,103]. These planted forests in Vietnam have potential pests and diseases, some of which may become invasive and damage new production forests in the future.…”

Pemetaan kondisi hutan mangrove di kawasan pesisir Selat Madura dengan pendekatan Mangrove Health Index memanfaatkan citra satelit Sentinel-2

“…Kondisi tersebut diperkirakan akibat fenomena dieback. Fenomena ini adalah kematian massal vegetasi mangrove secara gradual yang ditandai dengan menurunnya prosentase tutupan kanopi akibat gugurnya daun mangrove dalam jumlah yang besar (Nguyen et al, 2021;Sugiana et al, 2022). Tingginya sedimentasi akibat reklamasi pantai menjadi penyebab utama fenomena tersebut.…”