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Ministry of Agriculture, Food and Rural Affairs

Tarnished plant bug (TPB)

Tarnished plant bug nymph (NYS Agric. Expt. Station, Geneva, NY) Tarnished plant bug adult (Agriculture and Agri-Food Canada, Saskatoon Research Centre) Tarnished plant bug injury
Click to enlarge.

Beginner

Scientific Name
Lygus lineolaris

Identification
Nymphs:

  • Greenish with black spots,
  • Wing pads are present on older nymphs,
  • Move rapidly when disturbed. 
  • 4 mm long

Adults:

  • Oval,
  • 5-6 mm long,
  • Brown-yellow mottled appearance,
  • Buff or yellow Y on the triangular area between the wings (scutellum),
  • Adults from the overwintering generation tend to be much darker than the summer generation

Damage:

  • Damaged buds exude clear, and later amber, liquid ooze,
  • Affected buds do not set and subsequently abort,
  • Flowers are attacked prior to petal fall abort,
  • Fruitlets stung after calyx may fall off the tree during June drop, those that remain on tree have a dimple or a deeply sunken conical area at harvest,
  • In general, early season damage occurs near the calyx end; later season damage may be anywhere on the apple,
  • Longitudinal sections cut through the depressions or dimples show a narrow tube extending to the core (but not into the core) or calyx.

Often Confused With

  • Apple red bug damage- Apple red bug feeding injury appears as areas of smooth russetting on the fruit surface, with or without a depression.
  • Green apple bug damage- Green apple bug scars appears as raised russetted bumps on the fruit.
  • Stink bug damage- Stink bug damage appears as is sunken and often dark green spots on fruit.  Cutting below the skin reveals spongy cells, often with brown discoloration (similar to bitter pit, but is typically present at the top of the fruit –not the bottom.)
  • Apple seed chalcid damage- Injury from apple seed chalcid appears as a depression on the fruit surface; cutting the apple open shows a brown, narrow tunnel running through the flesh to the core.
  • Aphid nymphs- Tarnished plant bugs are distinguished from aphids by their lack of cornicles and rapid movement when disturbed. 
  • Mullein bug adults- Mullein bug adults are similar to adult tarnished plant bugs, but are more gray green in colour, and lack the cream coloured triangular plant on their back.

Period of Activity
Adult tarnished plant bugs begin feeding on apple buds on warm days in early April. Adults continue to feed on developing flowers from pink through the petal fall period, when most abandon the crop in search of alternative flowering hosts.

Scouting Notes
There are no set monitoring protocols for these insects. Adult insects are wary and quick to take flight. Walking through the orchard every few days in early spring and looking for ooze near or on flower buds gives an indication of adult feeding activity. Alfalfa is a favoured host and when it is harvested, adults will move to adjacent crops in large numbers.

Thresholds
None established.

Advanced

Scientific Name
Lygus lineolaris

Identification
Tarnished plant bug nymphs are greenish with black spots. Wing pads are present on older nymphs. They are distinguished from aphids by their lack of cornicles and rapid movement when disturbed. Adult tarnished plant bugs are oval, 5-6 mm long, with a brown-yellow mottled appearance. A diagnostic feature is the buff or yellow Y on the triangular area between the wings (scutellum). Adults from the overwintering generation tend to be much darker than the summer generation

Adults feed on developing flowers. Damaged buds exude clear liquid ooze, which becomes amber after several hours. Affected buds do not set and subsequently abort. Flowers attacked prior to petal fall abort. Fruitlets stung after calyx fall off the tree during June drop, but those that hang on until harvest have a dimple or a deeply sunken conical area caused by the injection of a toxin during feeding. In general, early season tarnished plant bug damage occurs near the calyx end. Later season damage may be anywhere on the apple. Longitudinal sections cut through the depressions or dimples show that tarnished plant bug feeding causes a narrow tube extending to the core (but not into the core) or calyx.

Often Confused With

  • Apple red bug damage- Apple red bug feeding injury appears as areas of smooth russetting on the fruit surface, with or without a depression.
  • Green apple bug damage- Green apple bug scars appears as raised russetted bumps on the fruit.
  • Stink bug damage- Stink bug damage appears as is sunken and often dark green spots on fruit.  Cutting below the skin reveals spongy cells, often with brown discoloration (similar to bitter pit, but is typically present at the top of the fruit –not the bottom.)
  • Apple seed chalcid damage- Injury from apple seed chalcid appears as a depression on the fruit surface; cutting the apple open shows a brown, narrow tunnel running through the flesh to the core.
  • Aphid nymphs- Tarnished plant bugs are distinguished from aphids by their lack of cornicles and rapid movement when disturbed. 
  • Mullein bug adults- Mullein bug adults are similar to adult tarnished plant bugs, but are more gray green in colour, and lack the cream coloured triangular plant on their back.

Biology
Adult tarnished plant bugs overwinter under leaf debris, bark, logs and under broadleaf weed litter. They become active on warm days in early spring and attack apple buds before green tissue is even present. In late spring (late May and early June), the insects migrate to herbaceous weeds, flowers and vegetables where they insert eggs into stems and stalks. Nymphs progress through five instars before molting to adults. The final three instars have wing pads. There are two generations per year.

The tarnished plant bug has a very broad host range, feeding on more than 300 plant species including weeds, vegetables, fruit, flowers, shrubs and trees. They prefer feeding on floral buds and immature fruit. Adults are mobile and move from one crop to another as the season progresses, in search of alternate hosts.

Period of Activity
Adult tarnished plant bugs begin feeding on apple buds on warm days in early April. Adults continue to feed on developing flowers from pink through the petal fall period, when most abandon the crop in search of alternative flowering hosts.

The amount of injury depends on numbers of adults successfully overwintering and on spring temperatures. Warm weather in early April, prior to broadleaf weed emergence often results in adult migration into trees. Cool springs usually result in less damage. Some studies indicate tarnished plant bug injury is heaviest on lower branches. While damage to bearing orchards is minimal after June, nurseries and newly planted blocks are susceptible throughout the summer. 

Scouting Notes
There are no set monitoring protocols for these insects. Adult insects are wary and quick to take flight. Walking through the orchard every few days in early spring and looking for ooze near or on flower buds gives an indication of adult feeding activity. Alfalfa is a favoured host and when it is harvested, adults will move to adjacent crops in large numbers.

Thresholds
None established.

Management Notes

  • Injury from tarnished plant bug at harvest normally ranges from 0.25% to 1.00%, however damage occasionally can reach 2% or more. Pesticide applications targeted at the pest are not economical, unless tarnished plant bug is a perennial problem in an orchard.
  • Pre-bloom and petal fall insecticide applications – targeted at other early season pests – may suppress tarnished plant bugs. See OMAFRA Publication 360, Guide to Fruit Production - Chapter 3 Apples (PDF) or Apple Calendar only (PDF) :
  • Many newer narrow-spectrum insecticides have no activity on plant bugs.
  • Cultural management techniques are important in reducing risk of tarnished plant bug injury.
  • The following practices are recommended:
    • practice good sod management by reducing or eliminating alternate weed hosts, particularly chickweed, dandelion, clovers, pigweed and lamb’s-quarters
    • avoid mowing of sod from bloom through petal fall period to prevent adult plant bugs from flying into trees
    • maintain clean herbicide strip
    • control weeds at headlands, these act as alternative hosts and resting sites
    • avoid situations where orchards are adjacent to hay (alfalfa) fields, strawberry patches or other susceptible crops.