Management of Pea Leaf Weevil (Coleoptera: Curculionidae) and Development of a Nominal Threshold in Faba Beans

Abstract

Pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), can reduce the yield of field pea [Pisum sativum (L.) (Fabales: Fabaceae)] and faba bean [Vicia faba (L.) (Fabales: Fabaceae)]. Adults feed on the foliage and larvae feed on root nodules and nodule-associated Rhizobium Frank (Rhizobiales: Rhizobiacea) bacteria. In this study, we developed a data-based nominal threshold for pea leaf weevil in faba bean. We further tested the efficacy of insecticidal seed treatment and foliar insecticide (thiamethoxam and lambda-cyhalothrin, respectively), and nitrogen amendment for pea leaf weevil control using a multi-year field plot study at two sites in Alberta, Canada. Pea leaf weevil feeding damage significantly reduced faba bean yields. Thiamethoxam reduced adult and larval damage, and protected faba bean yield, while neither lambda-cyhalothrin nor a nitrogen amendment was effective in protecting yield. The percentage of seedlings with feeding on the terminal leaf had a negative relationship with yield and was used to estimate a nominal threshold near 15% of seedlings with terminal leaf damage. Since lambda-cyhalothrin is not effective in managing pea leaf weevil on faba bean, there is a need to research additional integrated pest management strategies to reduce prophylactic insecticidal seed treatments.

A fluorometric assay to estimate pea leaf weevil (Coleoptera: Curculionidae) larval feeding damage using leghaemoglobin in root nodules of faba bean (Fabaceae)

“…Foliar damage correlates with nodule damage in faba bean (Wijerathna et al 2021) but not in field pea (Cantot 1989;Cárcamo and Vankosky 2011). The current method for estimating larval damage is labour and time intensive, as each nodule is inspected for larval feeding holes (Cárcamo and Vankosky 2011;Wijerathna et al 2021). Because faba bean has more nodules than field pea does, assessment of nodule damage on faba bean is even more laborious (Wijerathna 2021).…”

“…Pea leaf weevil larval feeding reduces nitrogen availability for field pea plants (Cárcamo et al 2015), seed nitrogen content, soil nitrogen input (Doré and Meynard 1995;Corre-Hellou and Crozat 2005), and yield (Hunter 2001;Corre-Hellou and Crozat 2005). In faba bean, larval feeding reduces yield (Wijerathna et al 2021) and pod production (El-Dessouksi 1971).…”

“…The pea leaf weevil was first recorded in southern Alberta, Canada in 1997 (Vankosky et al 2009). Current pea leaf weevil chemical management practices in Canada's Prairie provinces rely on monitoring adult feeding damage on field pea (Philip et al 2018) and faba bean (Wijerathna et al 2021), even though larval feeding causes the economic damage. The nominal threshold is 15% and 30% of plants with adult damage on terminal leaves for faba bean and field pea, respectively (Cárcamo and Vankosky 2011;Wijerathna et al 2021).…”

“…Current pea leaf weevil chemical management practices in Canada's Prairie provinces rely on monitoring adult feeding damage on field pea (Philip et al 2018) and faba bean (Wijerathna et al 2021), even though larval feeding causes the economic damage. The nominal threshold is 15% and 30% of plants with adult damage on terminal leaves for faba bean and field pea, respectively (Cárcamo and Vankosky 2011;Wijerathna et al 2021). Foliar damage correlates with nodule damage in faba bean (Wijerathna et al 2021) but not in field pea (Cantot 1989;Cárcamo and Vankosky 2011).…”

“…The nominal threshold is 15% and 30% of plants with adult damage on terminal leaves for faba bean and field pea, respectively (Cárcamo and Vankosky 2011;Wijerathna et al 2021). Foliar damage correlates with nodule damage in faba bean (Wijerathna et al 2021) but not in field pea (Cantot 1989;Cárcamo and Vankosky 2011). The current method for estimating larval damage is labour and time intensive, as each nodule is inspected for larval feeding holes (Cárcamo and Vankosky 2011;Wijerathna et al 2021).…”