Plant Spacing and Stand Density Effects on Aphid–Braconid Wasp Dynamics in Okra (Abelmoschus esculentus) in Benin City, Edo State

Abstract

Aphid infestations represent a major constraint in okra production, yet their population dynamics are strongly influenced by crop configuration, growth stage, and prevailing weather conditions. Field experiment using a Randomized Complete Block Design (RCBD) was conducted to assess the effects of plant spacing and stand density on aphid abundance and associated parasitoid. Results indicated that plant spacing and stand density did not significantly (p ˃ 0.05) affect aphid populations, although numerically higher infestations were observed under closer spacing (40 × 25 cm). In contrast, aphid abundance varied significantly across weeks after sowing (WAS), with populations remaining low at 2–3 WAS, rising sharply from 4–6 WAS, and peaking between 7–10 WAS. Pooled aphid populations across treatments reached maximum density (1202.00 individuals/five plants) at the 43rd meteorological week (8 WAS) while parasitoid populations peaked (14.50 individuals/five plants) earlier at the 39th week (4 WAS). Correlation analysis showed that aphid abundance was positively associated with temperature (r = 0.86) and parasitoid density (r = 0.71), but negatively correlated with humidity (r = –0.75) and rainfall (r = –0.79). Parasitoid abundance was significantly linked to aphid density but not to weather parameters, indicating a density‑dependent response. These results underscore the importance of integrating crop growth stage, planting configuration, and climatic monitoring into pest management strategies for sustainable okra production.