Insect of the Week (Jul
29) – Monarch vs. Painted Lady
The case of the Monarch butterfly vs. Painted Lady butterfly (also
An orange butterfly fluttered by. Was it a Monarch butterfly (Danaus
plexippus)? Or a Painted Lady butterfly (Vanessa cardui)? If it’s a
Monarch, it is species of Special Concern listed under the Species at Risk Act
and is not a crop pest. Instead, it’s larvae feed solely on milkweed (Asclepias
spp.), typically found in wetland areas. Painted Lady larvae, on the other
hand, feed on a wider range of plants including sunflower, canola, mustard,
borage, soybean, Canada thistle, burdock, knapweed, wormwood and many other
plant species. While neither species overwinter in Canada, Monarchs have regular
migratory routes into Canada from Mexico
through the USA; Painted Ladies are accidental tourists that are on occasion
blown up from the US.
One important distinguishing characteristic is the distinct black
band with white dots that outline the wings of Monarchs. Painted Ladies do not
have this band; instead they have thin white markings along the scalloped wing
Viceroy butterflies (Limenitis archippus) are even more difficult to tell from
Monarchs. Viceroys are smaller than Monarchs and sport a black line running
through the middle (side-to-side) of the hindwing. Like the Monarch, Viceroys
are not crop pests as their larvae feed exclusively on trees of the willow
family (willow, poplar, cottonwood).
For more information about Painted Lady butterflies, see the
Insect of the Week page and our posts on the annual Monarch
The case of the innocuous versus the evil
twin: When making pest management decisions, be
sure that the suspect is actually a pest. This can be challenge since insects
often mimic each other or look very similar. An insect that looks, moves and
acts like a pest may in fact be a look-alike or doppelganger.
Doppelgangers may be related (e.g. same
genus) or may not be related, as in the case of monarch butterflies (Danaus
plexippus) and viceroys (Limenitis achrippus). Doppelgangers
are usually relatively harmless but sometimes the doppelganger is a pest yet
their behaviour, lifecycle or hosts may be different.
Correctly identifying a pest enables selection of the most accurate scouting or
monitoring protocol. Identification and monitoring enables the application of
economic thresholds. It also enables a producer to select and apply the most
effective control option(s) including method and timing of application.
For the rest of the growing season, the Insect of the Week will feature insect
crop pests and their doppelgangers.
Review previously featured insects by
visiting the Insect of the Week page.
Created August 12, 2019 | Category: News Articles