Comparative efficacy of botanical protectants and phostoxin against Sitophilus oryzae (L.) infestation in stored rice under laboratory conditions

Rice weevil, Sitophilus oryzae (L.), is a major pest of stored grains, causing substantial qualitative and quantitative losses during storage. Chemical pesticides, including fumigants, are widely used for its control; however, concerns regarding pesticide residues and the development of insecticide resistance have increased interest in botanical alternatives. Accordingly, this study evaluated and compared the efficacy of selected botanical protectants with a synthetic fumigant for the management of rice weevil infestation in stored rice under laboratory conditions. The experiment was conducted using a completely randomized design with three replicates and eight treatments: T₀ = untreated control, T₁ = Phostoxin tablet, T₂ = chinaberry leaf (Melia azedarach) powder, T₃ = neem (Azadirachta indica) oil, T₄ = biskatali (Persicaria hydropiper) plant powder, T₅ = mahogany (Swietenia macrophylla) seed kernel powder, T₆ = akanda (Calotropis gigantea) plant powder, and T₇ = uchunti (Ageratum conyzoides) plant powder. Phostoxin resulted in 100% adult mortality, complete suppression of F₁ progeny emergence, and the highest seed germination. Among the botanical treatments, neem oil achieved high adult mortality (91.67%), markedly reduced F₁ progeny emergence (3.00; 94.65% reduction), and minimized grain damage (2.24%) and weight loss (4.49%), with performance statistically comparable to that of Phostoxin. Biskatali plant powder produced the second-highest adult mortality (71.67%), whereas chinaberry leaf, mahogany, akanda, and uchunti exhibited moderate adult mortality (41.67–55.00%). Chinaberry leaf powder and mahogany seed kernel powder also provided moderate suppression of F₁ progeny (77.23–77.71% reduction). None of the treatments adversely affected seed germination. Phostoxin recorded the highest seed germination (93.67%), followed by mahogany seed kernel powder (90.67%), while the remaining botanical treatments resulted in germination rates ranging from 82.67% to 88.00%, compared with 80.67% in the untreated control. Under controlled laboratory conditions, neem oil demonstrated considerable potential as an environmentally friendly alternative to synthetic fumigants, while biskatali and mahogany may serve as complementary components of integrated stored-grain pest management. Nevertheless, further validation under practical storage conditions is required before large-scale application.