Assessment of Pest Pressure and the Severity of Attacks by Rice (Oryza sativa L.) Insect Pests in the Maniema Production Basins, Democratic Republic of the Congo

Abstract

Rice (Oryza sativa L.) production in the Democratic Republic of the Congo faces significant biotic constraints, particularly attacks by insect pests that hinder yield stability. Aims: To evaluate the spatial variability of agro-morphological traits, pest pressure, and the severity of damage caused by insect pests to rainfed rice (Oryza sativa L.) across major production basins in Maniema Province, Democratic Republic of the Congo, to inform targeted integrated pest management strategies. Study Design: A multi-site comparative field evaluation combining agro-morphological measurements with a quantitative phytosanitary diagnosis. Place and Duration of Study: Agricultural fields across the production basins of Kailo, Kasongo, and Kibombo, Maniema Province, Democratic Republic of the Congo, during the crop maturity phase. Methodology: A two-stage stratified sampling scheme was implemented across 384 rice fields (128 per basin), with 10 randomly selected plants evaluated per field (N = 3,840 plants). Recorded agronomic parameters included plant height, collar diameter, tiller count, and panicle grain load. In situ visual counts were used to assess pest abundance, infestation rate, and attack incidence. Qualitative canopy sweep sampling (n = 176) was used to identify pest taxonomic structure. Foliar and panicle attack severity were scored on a 0–9 scale to compute McKinney’s severity index (Is). Data were analysed using ANOVA, Tukey’s HSD test, Pearson’s chi-square (χ2) test, and ecological diversity indices in R. Results: Plant height was homogeneous across basins (1.25 to 1.31 m; p = 0.0351), whereas collar diameter, tiller count, and grain load showed significant spatial variation (p < 0.001). Orthoptera dominated the entomofauna (60.80%), led by Oxya hyla (31.25%), followed by Hemiptera (15.34%). Kailo achieved the highest grain load (139.13 ± 23.92 grains/panicle) but had high grain damage (3.66 ± 1.72 grains/sample). Kibombo emerged as the primary epidemic hotspot, exhibiting the lowest Pielou evenness (J’= 0.68), the highest mean pest abundance (1.16 ± 1.46 ind./plant; p = 8.37 times 10-13), a 57.97% infestation rate, 88.05% attack incidence, and an alarming McKinney index of 53.03% (compared to 18.05% in Kailo and 20.56% in Kasongo). Conclusion: Entomological pressure and damage severity in rainfed rice are highly spatially dependent in Maniema. Kibombo requires urgent, localised intervention focusing on cultural controls and targeted biopesticides during tillering, whereas Kailo requires monitoring against sucking pests during grain filling.