Population dynamics of insect pests across phenological growth stages of rice in the forest belt of Ghana

Résumé fourni par la source

Rice agroecosystems harbor diverse insect pest communities whose composition and dynamics vary across space, season, and crop growth stages. This study assessed pest species occurrence, dominance, diversity, and indicator species across three rice-growing districts. A total of 35 insect pest species belonging to 17 families and 6 orders were identified from 1,441 specimens collected through sweep net sampling. Juaben exhibited the highest species richness (28 species), followed by Offinso (22) and Atwima Mponua (17), with several species unique to specific locations and 15 species shared across all districts. Diopsis thoracica was the most dominant species (16.5-17.5%), followed by Aspavia armigera, Leptocorisa spp., Cofana spectra, and Cofana unimaculata, representing key feeding guilds including stem borers, grain suckers, and sap suckers. Guild composition varied spatially, with stem borers dominating in Offinso, while grain and sap suckers were more prominent in Atwima Mponua. Pest abundance was consistently higher in the major season. Diversity indices, including the Shannon–Wiener index, were highest in Juaben, and Bray-Curtis and PERMANOVA analyses revealed significant spatial (p = 0.001) and seasonal differences in pest composition, despite high similarity between seasons (88%). Pest dynamics also varied across crop growth stages, with grasshoppers dominating early stages and grain suckers increasing toward maturity. Indicator species analysis identified eight key species, with Leptocorisa spp. strongly associated with later growth stages. In conclusion, spatial heterogeneity, seasonal variation, and crop phenology significantly influence pest community structure, emphasizing the need for location- and stage-specific integrated pest management strategies.

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