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Ministry of Agriculture, Food and Rural Affairs

Alfalfa Plant Bug

Alfalfa Plant Bug Nymph Alfalfa Plant Bug Adult Alfalfa Plant Bug Nymph
Click to enlarge.

Beginner

Scientific Names
Adelphocoris lineolatus

Identification

  • Alfalfa plant bug adults are approximately 8 mm long. They have an elongated, green body with cream-coloured markings.
  • Nymphs are pear-shaped and bright green with darker legs. Later instar nymphs have obvious wing buds on their backs.
  • Nymphs move quickly and are difficult to catch.
  • Both nymphs and adults feed on asparagus. As they feed they inject toxic saliva into the plant tissue. This causes the spear to wrinkle and become distorted.

Often Confused With
Tarnished Plant Bug
Phytophthora

Period of Activity
Mid-April to late-May

Scouting Notes
During harvest, monitor fields for activity at least once a week. Instruct pickers to report any unusual pest activity in the field. Plant bugs often assemble in one particular area of the field, often adjacent to woodlots or other sheltered areas.

Thresholds
None established.

Advanced

Scientific Names
Adelphocoris lineolatus

Identification
Alfalfa plant bug adults are approximately 8 mm long. They have an elongated, green body with cream-coloured markings. The nymphs are pear-shaped and bright green with darker legs. Later in-star nymphs have obvious wing buds on their backs.

The alfalfa plant bug has piercing and sucking mouthparts. As it feeds, it injects toxic saliva into the plant tissue. This causes the spear to wrinkle and become distorted. Under severe feeding, the spear will fail to elongate, dry up and die.

Often Confused With
Tarnished Plant Bug
Phytophthora

Biology
Plant bug adults overwinter in hedgerows and plant debris. They emerge and feed in mid-April to late-May. Eggs are laid on the stems/petioles of host plants, including many weed species. Ten days later the nymphs emerge. Populations in asparagus move into the field from adjacent host crops or weed species.

A new generation of adults emerges in July with second generation nymphs present in late-July to August. Mature ferns are less susceptible to injury at this stage.

Period of Activity
Mid-April to late-May

Scouting Notes
During harvest, monitor fields for activity at least once a week. Instruct pickers to report any unusual pest activity in the field. Plant bugs often assemble in one particular area of the field, often adjacent to woodlots or other sheltered areas.

Thresholds
None established.

Management Notes

  • Reduce nearby weedy patches and other sources of habitat.
  • Take note of any other host crops, such as alfalfa, beans or strawberries, in the area.
  • Feeding by the alfalfa plant bug may cause the plant to be susceptible Fusarium or Phytophthora infections. Control developing populations to help prevent the spread of these two serious diseases.