Eco-friendly management of storage pests in wheat using plant-based protectants

Abstract:

Like a silent tax on food security, storage pests destroy an estimated 10 to 30 percent of harvested wheat in warm climates before the grain ever reaches a mill or a consumer's table. Synthetic insecticides—aluminium phosphide, malathion, deltamethrin remain the default control method, but growing concerns about chemical residues in food, occupational safety, and insect resistance have revived interest in plant-based alternatives. This research evaluated three plant protectants—neem leaf powder (Azadirachta indica, 2% w/w), eucalyptus essential oil (Eucalyptus globulus, 0.5% v/w), and turmeric rhizome powder (Curcuma longa, 3% w/w) against the major wheat storage pests Sitophilus oryzae (rice weevil) and Rhyzopertha dominica (lesser grain borer) under laboratory and warehouse conditions at the Instituto de Ciencias Agrícolas de Andalucía, Córdoba, Spain, during 2022-23. In laboratory bioassays, neem leaf powder caused 78.4 percent adult mortality of S. oryzae at 14 days and 84.2 percent repellency, significantly outperforming eucalyptus oil (62.7% mortality) and turmeric (51.3%). Grain weight loss was reduced from 18.7 percent in the untreated control to 5.3 percent under neem treatment after 90 days of storage. In warehouse trials, neem-treated grain maintained 92.1 percent germination versus 74.3 percent in untreated grain. Eucalyptus oil showed strong initial repellency but its volatile nature limited residual protection beyond 6 weeks. These results support the use of neem leaf powder as the primary plant-based protectant for on-farm wheat storage in Mediterranean climates, with eucalyptus oil as a supplementary fumigant.