Revising economic injury levels for Lygus spp. in canola: The value of historical yield and insect data to improve decision making

Abstract

Canola is one of the most important cash crops in Canada, but yields can be reduced by several insect pests including Lygus spp. (Hemiptera: Miridae). Canola cultivars have been improved substantially since economic thresholds were developed for Lygus in the 1990's. Thus, the objective of this study was to integrate a large data set collected over 23 years (1999–2021) from plots and commercial fields to update economic thresholds. Regression analysis of the data from the studied years from across distinct ecoregions yielded an overall Economic Injury Level (=action threshold) around 9–23 Lygus per 10 sweeps using the current (high) canola prices. However, insecticide trials at farmer's commercial fields, showed that yield was protected from Lygus feeding by spraying a foliar insecticide at the early pod stage only when catches exceeded 30 Lygus per 10 sweeps. Further analysis of Precision Yield Data (PYD) from combine yield monitors from southern Alberta, revealed that at low abundances, under 17 Lygus per 10 sweeps, Lygus may potentially stimulate canola yield and do not require a control action, unless there are more than 30 Lygus per 10 sweeps. Developing a long term data repository for PYD across multiple sites and spatial scales in the Prairies of Canada would allow future generations of researchers to improve decision making tools such as pest action thresholds, to develop a more resilient and sustainable agriculture.