Insect Management

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 as the plant tries to compensate for the lost biomass. Damage from grasshopper feeding is variable. Slight damage to the pods may result in shattering, seed loss, increased risk of disease, and seed staining. At harvest, grasshopper parts, specifically heads, can be a problem to clean out, resulting in grade reduction.

Economic Control threshold is two grasshoppers per square metre in lentils. If control is needed, the optimal timing is when nymphs are at the third instar, 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 per metre squared in the top 7.5 cm (3 inches) of soil. Lentil crops can often recover from cutworm damage given favourable growing conditions but maturity may be delayed. Scouting for cutworms is often more successful in the evening when they come out to feed.

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 lentils 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 for lentils 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.

Pea aphids can affect lentil yield and quality when present in sufficient numbers. Damage caused by aphids can be difficult to quantify because they rob plants of resources by piercing and sucking rather than chewing and defoliating. Adults can develop wings, but are often wingless. Populations can increase rapidly due to their ability to give birth to live young without mating, and because they can easily migrate into areas on air currents. Control threshold numbers are approximately seven to eight aphids per plant tip.