2023 Canola Survey: Lygus

As we draw closer to the end of June, lygus bugs (Fig. 1) will be emerging and laying eggs in the Peace River region. Canola is especially susceptible to lygus damage, in addition to alfalfa, potatoes, and other plants. Typically, lygus migrate from alfalfa to canola when buds and flowers are developing in June through early July. Crops can be severely damaged by the feeding of adult and nymph lygus, resulting in loss of yield and a decrease in quality.

In the Peace River region, adult lygus lay eggs during mid-June in the stems and leaves of plants. Egg laying occurs over three to seven weeks.

Figure 1: Fifth instar lygus nymph (left) and adult lygus (right). Photo credit: Jennifer Otani-AAFC Beaverlodge

Early instar lygus nymphs are light green and wingless. As they mature, black dots develop on the top of the thorax and abdomen and wing buds begin to develop (Fig. 3). Adult lygus range from pale green to reddish brown and have a distinctive triangle or “V’ shape marking on their back (Fig. 2). Both adult and nymph lygus bugs have piercing-sucking mouthparts that physically damage plants.

Figure 2: Adult lygus. Photo credit: Jennifer Otani-AAFC Beaverlodge.

Figure 3: Fifth instar lygus nymph. Photo credit: Jennifer Otani-AAFC Beaverlodge.

When feeding, these mouthparts pierce seedpods and puncture plant cells, leaving visible abrasions on plant surfaces. Lygus insects also inject toxic saliva while feeding, that perniciously effect host plants. Feeding damage collectively results in leaf disfiguration, drooping of buds and blossoms, and shriveling of seeds.

Hot, dry conditions encourage lygus development and population growth. The economic threshold for lygus in canola encompasses the flowering and early pod ripening stages. Economic thresholds and plant stage should be carefully considered when choosing to apply insecticide. Application costs may exceed resulting benefits if seeds have already ripened to yellow or brown. Information about economic thresholds and lygus monitoring can be found here. 

Author: Jadeyn Lunn