Insect update: leaf rollers, wireworms, bertha, flea beetles

Leaf roller. Leaf rollers were found in some canola fields in northeast Saskatchewan in the past week. The little green worm that dances around when you touch it can be confused with diamondback moth larvae. They are typically a pest of leaves on trees, so their potential for causing economic damage to canola at this stage is uncertain, but is probably low unless defoliation is extensive.


Wireworms and their adult form, click beetles. Source: Scott Hartley, SMA

Wireworm. Surveys by AAFC found that two species are most prevalent and likely cause most of the wireworm damage to Prairie crops. They are Hypnoides bicolor and Ctenicera destructor. C. destructor grows to an inch long, and can live 4 years in the larval stage. H. bicolor grows to about half an inch, but are more numerous than destructor. Their lifecycle is about two years. In late spring and early summer, the adults — click beetles — move into cereal fields or pasture, and lay eggs throughout the field. Three weeks later eggs hatch. These first instars will feed on cereal roots, overwinter and continue feeding in following years. Wireworms feed on a variety of plants, but their preferred food is cereal and grass roots. In the absence of these, wireworms will feed on canola plants, but the volume of root tissue in the soil might satisfy them without taking out a large proportion of the crop. Feeding tends to look like holes in the roots. Wireworms spit out an enzyme that will break down root tissue, then they slurp it up, leaving a hole.

Nothing is registered to control wireworms in canola. Scouting is still important to distinguish wireworm feeding from cutworm feeding, which can be stopped with insecticide. If wireworms are the cause, growers can manage the threat with wireworm seed treatments on cereals. Bob Vernon and Wim Van Herk with AAFC continues their survey of Prairie wireworms. Collected wireworms can be put into sealed containers with soil and shipped to his address.  When submitting worms, in addition to precise location and grower information, please add additional information on the crop involved during the collection, and whether wireworms were suspected or confirmed alongside any damage, and the severity (% loss) of damage in the field. Click Bob’s name above to contact him for more information. This is very important in determining the damage potential of these species in canola to guide the need for future research.

Bertha armyworm. Bertha armyworm monitoring programs are underway and counts are coming in. The first maps of the season will soon be available. Bertha armyworm trap cooperators please remember to forward your land locations and weekly counts. In Saskatchewan, contact Sean Miller at 1-888-323-7842 or In Manitoba, contact John Gavloski at (204) 745-5668 or

Flea beetles. Canola at the cotyledon stage is still at risk. Although flea beetle populations have been dropping significantly over the last couple of  weeks, adults will feed from April to July. After the 4-leaf stage, canola is growing fast enough that flea beetle feeding is no longer a threat — even though the insects may still be present in the field.