Pest activity and natural enemy diversity in stored dry date (Phoenix dactylifera L. (Arecales: Arecaceae)) in the Northern Guinea Savannah Agroecological Zone

The diversity, abundance and ecological distribution of dry date (Phoenix dactylifera L. (Arecales: Arecaceae)) pests and associated natural enemies were investigated along with date infestation rates, fruit damage levels and existing correlations in Zaria, northern Guinea Savannah Agroecological Zone (nGSAZ), Nigeria. Dry dates (three cultivars: Dan-Agadez, Dan-Hausa and Deglet) were sampled in eight locations, over eight months in 2018, for laboratory observations. Eight pest species (6 coleopterans and 2 lepidopterans) and 14 natural enemies (10 parasitoid and four predator species) were recovered. Pest richness (S, 4–7), diversity (H′, 0.62–1.55), evenness (J’, 0.38–0.79) and dominance (1/d, 1.20–2.82) per month/cultivar were low to moderate, while natural enemy richness (S, 5–12), diversity (H', 1.15–1.90), evenness (J’, 0.59–0.82) and dominance (1/d, 1.60–3.48) per month/cultivar were moderate to slightly high. Total date infestation rates (19%-30%) and fruit damage levels (11%-15%) did not vary significantly with location, month or cultivar. Abundance of most natural enemies (11 species) correlate positively with abundance of at least one of four pest species (Cadra cautella (Walker), 9 species; Oryzaephilus mercator (Fauvel), 8 species; Carpophilus dimidiatus (Fabricius), 6 species; and Tenebroides mauritanicus (L.), 1 species). Further, abundance of a few species (i.e., Brachymeria sp. and Phanerotoma sp. nr. philippinensis) correlate either positively or negatively with date fruit moisture content and relative humidity. In conclusion, predominant dry date pests and related natural enemies in the nGSAZ are respectively O. mercator > C. cautella/Lasioderma serricorne (F.) and Cephalonomia sp. > Pheidole sp. Collectively, recovered pests were responsible for moderate infestation rates and low fruit damage levels. Correlation results emphasize the need to further comprehend the functional response/efficiency of all natural enemies of dry date pests, as influenced by both abiotic and biotic factors.