July 20, 2016

Lygus: 3 main species

Three main lygus species are pests of canola in Canada. Colour and shape are somewhat different, but each should be counted equally when sweep netting and making spray decisions.

Lygus lineolaris is the most common in most regions, especially in the Parkland.
Lygus lineolaris is the most common in most regions, especially in the Parkland. Thanks to Hector Carcamo, AAFC, for the photos.

L. lineolaris
L. lineolaris

L. keltoni is dominant in southern Alberta, probably closer to the foothills.
L. keltoni is dominant in southern Alberta, probably closer to the foothills.

L. elsisus is more common farther east.
L. elsisus is more common farther east.

Also include late-instar nymphs in the counts. Nymphs are young lygus, and only the larger nymphs do enough damage to be included in sweep net counts. A key feature is the black dots on the back. Count nymphs with developing windpads or dark shoulderblade. Don’t count them if they’re small and don’t have the any sign of a dark growth where wings will be developing soon.

These small nymphs don’t feed very aggressively, and they are vulnerable to heavy rains and wind that push them down in the canopy or to the ground where they drown or get eaten by other insects.

Count these lygus nymphs, which have telltale black dots, when doing sweep net counts for lygus. Source: Roy Ellis
Count these lygus nymphs, which have telltale black dots, when doing sweep net counts for lygus. Source: Roy Ellis
Don't count these tiny ones without the black dots. This photo was taken on a lined notepad to show the size. Source: Justine Cornelsen
Don’t count these tiny ones without the black dots or signs of growth where wings would be. This photo was taken on a lined notepad to show the size. Source: Justine Cornelsen
Here's a close up view of this early instar lygus. Don't count these. Credit: Dan Johnson
Here’s a close up view of this early instar lygus. Don’t count these. Source: Dan Johnson
Count this one. It is developing wingpads and has the black dots. Credit: Keith Gabert
Count this one. It is developing wingpads and has the black dots. Source: Keith Gabert
This close up of a third instar shows the wingpads developing on the back. Count these. Credit: Dan Johnson
This close up of a third instar shows the wingpads developing on the back. Count these. Source: Dan Johnson

Click here for more on lygus thresholds and when it pays to spray.

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