Tarnished Plant Bug (a.k.a. Lygus Bug)

Causal Organism: Lygus lineolaris (and other species)

Crops Affected: Wide host range – many fruit, vegetable, field and forage crops and weed species

Life Cycle:

• One of the most serious & widespread of strawberry pests, but also affects many other crops
• Sucking insects that pierce flower buds, blossoms, and developing fruits and plant parts
• Adult has distinctive triangle or “V” mark on back
  • Adults are strong fliers
• Overwinter as adults in leaf litter or under debris and migrate into fields in spring or fall to feed on weeds and crops
• Lay eggs in spring in plant tissues
• Young/immature stages (a.ka. nymphs) resemble aphids without cornicles (tail pipes) and move more quickly
  • Nymphs hatch and feed on developing blossoms & fruit
  • Nymphs feed through May and June, maturing in late June to early July
  • Most of damage results from feeding by nymphs
• Adults feed on developing fruit
  • Leave with fruiting complete in June or July (strawberries)
  • May have 2-3 generations per year (depending on season length)
• Day neutral strawberries are flowering when TPB numbers are high, therefore damage potential is higher

Symptoms / Damage:

• Presence of insect life stages
• Range of damage to vegetables
  • Reduced fruit set in bean, pepper & eggplant
  • Blemishes on tomato fruit
  • Necrotic spots on florets & curd of broccoli, cauliflower and heads of lettuce
  • Dead leaves on potatoes
  • Foliar injury on cucumbers
  • Gummosis on zucchini

• Raspberries (most damage occurs after petal fall)
  • Feeding on flower blossoms & developing fruit = crumbly berry
  • Reduced plant vigour
• Saskatoon berries
  • Yellow, aborting flower buds; droplets of brownish liquid may exude from newly pierced buds
  • Fruit deformation
• Strawberries
  • Feeding by nymphs – Nubbins or deformed fruit / Apical seediness
  • Adult feeding – CATFACING
    NOTE: Catfacing can be caused by other factors, producing identical symptoms
• Feeding also reduces plant vigour due to removal of plant nutrients

Monitoring:

• Be aware of neighbouring crops that might be a host or that might release a large number of adults when cut (e.g. alfalfa or canola)

• Crop should be monitored for the number of nymphs in flower blossoms. Sweep nets can determine adult numbers
  • Scout the field perimeter in new fields or entire established fields
  • Start monitoring in overwintered fields from when they are uncovered onward
• Strawberry blossoms may be sampled from across the field, counting the number of nymphs and adults present
  • • Tap plants or shake fruit clusters over a non-metallic pie plate
    • Count the number of nymphs per 100 clusters
    • Strawberry Economic threshold = 1 nymph or adult per 8 blossoms
    • Survey the field from pre-bloom until green fruit stage (strawberries)

Management:

• Careful monitoring of TPB populations
• Remove weeds (especially leguminous species)
• Ensure alternate host crops are not planted too close (e.g. alfalfa)
• Make careful and timely chemical control applications
  • Controls are available with application timing restrictions
  • Chemical control is challenging due to continuous flowering and fruiting of day neutral strawberries
  • Only products with short Pre-Harvest Intervals (PHI) may be used
  • Do not apply products when bees are actively working

Tarnished Plant Bug – A Major Pest of Strawberry – OMAFRA article