Sciences marines : recherche et développement

Abstrait

A Case Study of Insect Pests and Disease-Causing Microorganisms In Mangrove Saplings in Davao Occidental, Philippines

Michelle M. Elemino, Pedro M. Avenido, Lynette A. Bontia, Irvin C. Generalao, Augie E. Fuentes

The study was conducted to determine the incidence and characterize insect pests and disease-causing microorganisms associated with planted mangrove Rhizophora sp. saplings in the two PNAP selected sites of Davao Occidental. The study was focused on the Rhizophora species as this mangrove species showed high dispersal patterns and exhibit a high percentage of planted mangroves covered during the implementation of the project.

There were eight species identified in terms of the level of infestation based on insect-pest occurrence under Phylum Arthropoda (1 Class Malacostraca: Aratus pisonii (Mangrove Tree Crab), 1 Bivalvia: Ostrea lurida (Olympia oyster), 2 Arachnida: Tetragnatha josephi (Mangrove big-jawed spider) and Ligurra latidens (Mangrove jumper) and 4 Insecta: Camponotus gigas (Giant Forest Ant), Polistes versicolor (Polistine Paper Wasp), Hyblaea puera (Teak defoliator) and Archips spp. (Tortrix). Among the recorded insects, four species were considered harmful to the mangrove ecosystem. They were Aratus pisonii (Mangrove Tree Crab), Ostrea lurida (Olympia oyster), Archips spp (Tortrix), and Hyblaea puera (Teak defoliator). Other four species were classified harmless namely Tetragnatha josephi (Mangrove big-jawed spider), Ligurra latidens (Mangrove jumper), Camponotus gigas (Giant Forest Ant), and Polistes versicolor (Polistine Paper Wasp).

Moreover, three-leaf diseases were noted in the samples i.e., leaf spot, leaf blight, and leaf chlorosis. For leaf spot, three species of fungi were identified Cercoscopra sp, Acrenomium sp, and Cladosporium sp., whereas, for leaf blight, two fungal species were observed Rhizoctonia sp and Phytophthora sp. Upon further verification, leaf spot and leaf blight were caused by fungi, whereas leaf chlorosis was affected by bacteria. Relationship on the level of infestation and extent of incidence in mangrove Rhizophora sp. saplings showed a high positive correlation degree of relationship with a value of ±745. This implies that when the level of infestation increases, the disease incidence correspondingly increases.