Small sips, big losses: measuring the feeding threshold of <i>Lygus</i> (Hemiptera: Miridae) on faba bean ( <i>Vicia faba</i> ) seeds

Faba bean (Vicia faba L.) is an increasingly important pulse crop in Western Canada, but its production is threatened by Lygus spp. (Hemiptera: Miridae), which cause pod and seed damage through piercing-sucking feeding. This study examined the relationship between Lygus feeding duration, insect density, and the extent of scarring damage in faba bean seeds using complementary no-choice and electrical penetration graph (EPG) experiments. In no-choice assays, single adults of L. lineolaris and L. elisus confined to plants for 1, 3, 24, or 48 h produced significantly increasing damage over time (F = 6.24; P < 0.001), reaching the Canadian Grain Commission's 1% downgrading threshold after only 3 h of feeding. Species did not differ in damage potential. EPG recordings of L. lineolaris feeding revealed 3 main probing waveforms: cell rupture (CR), transition (T), and ingestion (I), with nymphs spending longer in CR and I phases than adults, although waveform type, not life stage, significantly affected feeding duration. McBryde staining detected salivary deposits in a limited number of pods and seeds, primarily from males, suggesting differences in salivation behavior among life stages. Collectively, these findings demonstrate that brief feeding periods by Lygus can cause economically significant damage to faba bean seeds, highlighting the importance of monitoring pest activity and minimizing feeding duration to reduce quality losses. The integration of EPG behavioral data with seed damage assessments provides a basis for establishing feeding-time thresholds to guide faba bean pest management.