Grasshoppers: generally do not favour lentil foliage. They pose the greatest threat from the bud stage through to early pod development because they eat flower buds, open flowers, and developing pods. Feeding on early developing pods can result in yield loss and cause delay in maturity. This delay in maturity is due to delayed pod set as the plant tries to compensate for early season pod loss. Damage from grasshopper feeding is variable. Slight damage to the pods may result in shattering and seed loss. When the edge of the pod is chewed, the seeds are more susceptible to disease and staining. At harvest, grasshopper parts, specifically heads, can be a problem to clean out of lentil crops as they are in the same size range as the lens-shaped lentil seed. This results in a lower grade.
Threshold number is two grasshopper per square metre in lentil. This low number will cause enough yield and quality loss to warrant an insecticide application. If control is needed, the optimal timing is when nymphs are at the third stage, which is usually about mid-June. At this stage the grasshoppers become mobile, consume more, and most of the hatch should be complete. Often, grasshopper numbers will be higher in field margins and a thick lentil crop will deter the insects from moving further into the field as they prefer more open and bare areas. If grasshopper populations only exceed the economic threshold in the field margins, an edge treatment with an appropriate insecticide can save time and reduce costs, while providing adequate control.
Cutworms: can cause damage to newly emerged lentil seedlings, and at times may require insecticide application. Below-ground feeding cutworms (pale western and red-backed cutworms) cut plants off at or near the soil surface. Foliar feeding cutworms (dingy and army cutworms) feed above ground, consuming the plant foliage. The economic threshold for cutworms in lentil is 2 to 3/m2 (0.2 to 0.3/ft2) in the top 7.5 cm (3 inches) of soil. Lentil crops can often recover from cutworm damage if cool, moist growing conditions occur. However, plants are set back four days, and may not be competitive.
Wireworms: are the immature stage or larvae of click beetles. Wireworms tend to be more abundant in moist soils and in lower, damper areas of a field. Wireworms tend to shred the plant tissue below the soil surface. Initially, symptoms may show up as wilting in the central leaves of the main stem, but can eventually cause death of the plant. Damage may not be noticed early enough in the season to reseed. There is no established economic threshold for wireworm in lentil and there is no in-crop insecticide available to control wireworm. Controlling wireworm requires the use of an insecticidal seed treatment.
Lygus bug: can be a pest of lentil in the United States, but has not been a problem in lentil in Saskatchewan to date. The economic threshold for lygus bugs in lentil is seven to 10 adults per 25 sweeps during blooming and podding. To monitor with a sweep net make 25° to 180° sweeps (with a 38 cm (15 inch) net) in at least five randomly selected places in the field.