Insect of the Week (June 10, 2019) – Doppelgangers: Bertha armyworm and clover cutworm

The case of the bertha armyworm and the clover cutworm (and other cutworm species)

Clover cutworm larva

cc-by 3.0 Lo Troisfontaine

Bertha armyworm – caterpillar 

Mike Dolinski, MikeDolinski@hotmail.com

Are those bertha armyworms (Mamestra configurata) eating your canola, mustard or alfalfa (also found on lamb’s-quarters, peas, flax, potato)? Or is it maybe a clover cutworm (Discestra trifolii)? [Note: not all cutworm species spend their larval stage underground.] The larvae of the two species are doppelgangers as they are similar in appearance, have a large overlap in host crops, and have similar timing (June-September). Telling them apart can be a challenge but here are few tips to focus on to help distinguish:

-         Colour: there are generally fewer velvety black clover cutworm caterpillars, with most of the clover cutworm larvae being green or pale brown

-          Lateral stripe:

o   On the clover cutworm it is yellowish-pink

o   On the bertha armyworm it is yellowish-orange

Climbing cutworm larva - from Cutworm Field Guide

Climbing cutworm adults - from Cutworm Field Guide

In terms of scouting, economic thresholds and control options, treat both species as you would bertha armyworms.

Bertha armyworm – adult

Alberta Agriculture and Rural Development

Clover cutworm adult

cc-by-nc-sa 2.0 Ilona Loser

To learn more about bertha armyworms and clover cutworms, go to the Insect of theWeek page or download copies of the Field Crop and Forage Pests andtheir Natural Enemies in Western Canada and Cutworm Pests of Crops onthe Canadian Prairies identification field guides.