Efficacy of the Botanical Extracts, Azadirachta indica (Sapindales: Meliaceae) and Tagetes minuta (Asterales: Asteraceae) in the Control of Cabbage Insect Pests in Iringa District, Tanzania

Abstract

Although botanical extracts have been widely studied globally, the efficacy of neem and Mexican marigold against cabbage insect pests is scanty. Field experiments were conducted at Kalenga and Mgera in 2022 using a randomized complete block design. Four treatments (neem, Mexican marigold, a mixture of the two extracts and untreated) were replicated three times. In Kalenga, damage levels for treated plots varied significantly from 3.33 to 9.20% and 5.0 to 18.33%, while for untreated plots varied from 37.70 to 45.85% during the rainy and dry seasons, respectively (F_{(3, 499)} = 111.71, p < 0.05). A similar trend was recorded in Mgera, the damage levels varied significantly between treated (4.44–15.83%) and untreated plots (34.40–46.60%) (F_{(3, 449)} = 94.23, p < 0.05). Treated plots had higher marketable cabbage yields (30.6–43.10 t/ha) than untreated plots (4.78–11.20 t/ha), which differed significantly in Kalenga (F _{(3, 67)} = 141.79, p < 0.05) and Mgera (F _{(3, 67)} = 53.36, p < 0.05). These extracts have shown insecticidal properties, can serve as promising candidates for further studies aimed at isolating active compounds for scaling up ecologically friendly strategies of controlling pests and improve the quality of cabbage products.

Keywords: Cabbage; Mexican marigold; Neem; Kalenga; Mgera