Lygus Numbers Variable – Scout Thoroughly

Lygus populations continue to be monitored in the Peace Region of Alberta and BC and in southern Alberta. Populations are variable as many fields are exceeding economic thresholds (as much as three to four times higher) and still many others remain below threshold levels. Each field must be assessed for lygus on an individual basis. Scout all fields to determine the population levels in each individual field. Scout thoroughly as well, as high populations requiring control have been present only on field edges (not throughout the field) in some instances. When scouting for lygus, it is important to note the stage of the crop and insect. Young nymphs will do very little damage compared to later instars and adults. Later maturing fields may still be at significant risk but fields nearing maturity may escape the damage.  That’s because they will be less vulnerable, since pod texture becomes rubbery and tougher for lygus bugs to pierce. For more information on lygus monitoring refer to the following interview with Erin Brock, Peace region agronomy specialist on the ACPC website:http://www.canola.ab.ca/agronomic/grow_with_canola.html

Young lygus nymphs are pale green and resemble aphids but have five small black dots and no cornicles. Adult lygus bugs are pale green to reddish brown/black with a “V” mark one third of the way down their backs. Lygus cause damage by feeding on leaves, stems, flowers, and pods, resulting in flower blasting and shriveled seeds. There is a range for the economic threshold depending on crop stage and price.  More information is available at the following link: http://www.gov.mb.ca/agriculture/crops/insects/fad12s00.html.