Genistein and Naringenin as Defense Molecules

Genistein and naringenin, plant phenolic compounds, are recognized for their health benefits and role in plant defense against herbivores. However, little research exists on how these compounds affect aphid feeding, particularly that of the black bean aphid (<i>Aphis fabae</i> Scopoli) (Hemiptera: Aphididae), a major pest. This study aimed to evaluate the effects of genistein and naringenin, applied in vitro at different concentrations, on the feeding behavior of <i>A. fabae</i>. Statistical analysis indicated that both the type and concentration of flavonoids significantly influenced aphid stylet activity, salivation, and ingestion. Higher concentrations of both compounds hindered feeding behavior. A longer initial probe was observed on gels containing the studied flavonoids. Genistein at 0.1% completely inhibited salivation while at 0.01%, it reduced the duration of salivation activities. Both compounds also delayed the start and lengthened the duration of active ingestion, though <i>A. fabae</i> tolerated genistein better than naringenin. Naringenin's effects on feeding behavior were more pronounced at higher concentrations. These findings suggest that genistein and naringenin could be valuable chemicals to protect plants from aphids in a sustainable and environmentally friendly way.