Insect and Arachnid Communities in the Rice Fields of Davao Oriental, Philippines

Abstract

Rice production faces significant threats from destructive pests that reduce yields. However, natural enemies play a vital role in biological regulation of pests, supporting sustainable farming practices. This study assessed the diversity and ecological roles of insect and arachnid communities in rice agroecosystems of Davao Oriental to inform biodiversity-based pest management. Field surveys and collections were conducted using sweep nets, malaise traps, pitfall traps, and opportunistic sampling. Species diversity was measured using the Shannon diversity index (Hʹ), where values below 1 indicate low diversity, 1–2 moderate, and above 2 high diversity. Results showed that organic rice fields supported greater taxonomic richness and abundance (46 insect and 8 arachnid families; 4,398 insect and 3,932 arachnid individuals) than inorganic fields (38 insect and 6 arachnid families; 3,809 insect and 3,482 arachnid individuals). Interestingly, inorganic fields had slightly higher Shannon index values (2.528 for insects; 0.9051 for arachnids), suggesting a more even species distribution. Temporal analysis across rice growth phases revealed that diversity peaked during the vegetative stage and declined toward ripening, indicating higher ecological activity early in crop development. These findings highlight the positive impact of organic farming on insect and arachnid diversity and underscore the ecological importance of insects and arachnids in rice systems. Moreover, the presence of pest-dominant taxa points to the need for enhanced biological control strategies. Monitoring arthropod diversity is essential for developing ecologically sound pest management approaches and reducing reliance on chemical inputs in rice agroecosystems.