Abstract

Tobacco hornworms (Manduca sexta) are among the most destructive insect pests of Solanaceae crops. The larval stage causes the greatest damage by feeding on leaves and fruits, and infestation by as few as one to three larvae can result in complete crop loss. In addition, feeding wounds on stems create entry points for pathogens, often leading to whole-plant mortality. Although synthetic pesticides are effective for pest control, their continued use poses serious risks to human health and the environment. Consequently, plant-based biopesticides that are biodegradable, affordable, and environmentally friendly represent a sustainable alternative.

The increasing demand for safe pest control strategies highlights the need to expand the range of plant-derived insecticidal sources. Industrial hemp contains diverse phytochemicals with potential insect-deterrent properties; however, its antifeedant activity against tobacco hornworms remains poorly understood. This study evaluated the antifeeding effects of industrial hemp ethanol extracts against tobacco hornworm larvae under controlled in vitro conditions. Extract concentrations of 50, 25, 12.5, 6.25, 3.125, and 1.56 mg/mL were incorporated into an artificial diet, and fourth-instar larvae were reared for four days at 27 ± 2 °C, 60 ± 10% relative humidity, and a 12L:12D photoperiod. Larval relative growth rate differed significantly among treatments (P = 0.005). Growth was completely inhibited at 50 mg/mL, with larvae exhibiting body shrinkage (−0.05 g/g/day), comparable to the malathion positive control. Growth inhibition reached 71% at 25 mg/mL and exceeded 50% at lower concentrations. Antifeedant indices of 68% and 62% were observed at 50 and 25 mg/mL, respectively. These findings demonstrate that industrial hemp extract is a strong antifeedant against tobacco hornworms and represents a promising biopesticide for sustainable agriculture.