Developing economic thresholds and sequential sampling plans for lesser clover leaf weevil in red clover

Red Clover (Trifolium pratense) is a short-lived perennial crop grown for seed production. The production of red clover seed is a highly important commodity in the Canadian Prairies. The seed is exported into warmer regions where it is used as plough down green manure, which provides nutrients, primarily nitrogen and organic matter, to the soil. However, the production of red clover seed is greatly affected by the lesser clover leaf weevil (LCLW) due to their ability to cause extreme damage to developing crops. Yield losses of up to 50% have been recorded with high infestations of LCLW. LCLW larvae feed on the developing shoots, flower heads and seeds of red clover plants, which cause the most damage. LCLW are traditionally controlled using insecticides which are damaging to non-target insect species, notably bees which are important pollinators for red clover seed production. However, there are currently no established economic thresholds for control of LCLW in red clover fields. Redundant insecticide applications create a multi-faceted problem. Principally, the producer will have an income reduction due to added costs associated with applying an insecticide. Additionally, pollinator populations present during insecticide applications will be significantly diminished. Lastly, there is a high risk of developing insecticide resistance because there is only one registered insecticide material. This study aims to generate economic thresholds and sequential sampling plans so that producers can access management tools for the LCLW that will reduce input costs and environmental damage.