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Ministry of Agriculture, Food and Rural Affairs

Tarnished Plant Bug

Tarnished plant bug damage Tarnished plant bug nymphs Tarnished plant bug damage Tarnished plant bug adult Tapping tray Click to enlarge.

Beginner

Scientific Name
Lygus lineolaris

Identification

  • Adults:
    • Oval in shape
    • 4- 6 mm (1/6- ¼ in.) long
    • Green to brown in colour with triangular markings in the middle of the back
    • Fly quickly when disturbed
  • Nymphs:
    • Small in size, ranging from 1 to 5 mm (1/25- 1/5 in.) in length, depending on the instar
    • They are green in colour and darken as they mature
    • Typically the third instar stage has five black dorsal spots and is beginning to develop wing pads
  • Plant bugs have mouth parts that pierce and suck on plant juices
  • They feed on strawberry fruit and bloom, which causes misshapen fruit described as “catfacing” or “button berry”

Often Confused With
Frost
Poor pollination
Potato leafhoppers
Aphids

Period of Activity
Overwintering plant bug adults move into strawberry plantings in early spring (April).  Nymphs appear during strawberry bloom and are active through to the first harvest.  There are several generations per year and all stages can be present throughout the summer.

Scouting Notes
Monitoring to identify nymphs is critical to reduce damage, but nymphs can be difficult to find due to their size, colour and speed.  The only key symptoms of tarnished plant bug infestation are damaged fruit.

Look for tarnished plant bugs at first bloom (late May) through to the green fruit stage.  Walk in a “W” pattern across a block.  Tap the blossom clusters into a white tray or dish.  Count the number of nymphs per 100 clusters.

A faster method that can be used when populations are very low or very high is sequential sampling.  For sequential sampling count the number of infested clusters, not the number of nymphs per cluster.

Thresholds
The threshold for control is approximately one nymph in four flower clusters in June bearing varieties.  Thresholds might be different for day neutral varieties.

If using sequential sampling, refer to the table below for thresholds.

Number of clusters examined Number of flower clusters infested with TPB
Control not required Control required
2% Low threshold 4% Low threshold
15 0 3 or more 5 or more
20 0 4 or more 5 or more
25 1 or less 4 or more 6 or more
30 2 or less 4 or more 7 or more
35 3 or less 5 or more 7 or more
40 3 or less 5 or more 8 or more
45 4 or less 6 or more 9 or more
50 5 or less 6 or more 9 or more

 

Advanced

Scientific Name
Lygus lineolaris

Tarnished plant bugs are a major pest of strawberries, and are found worldwide in a variety of crops. Their ability to feed on a wide range of hosts and have multiple generations per year make them an extraordinary and resilient pest. Tarnished plant bugs can quickly migrate into a strawberry field from another crop such as alfalfa.

Identification
Adults are oval in shape, 4- 6 mm (1/6- ¼ in.) long and green to brown in colour with triangular markings in the middle of the back. They fly quickly when disturbed. Nymphs are small, ranging from 1 to 5 mm (1/25- 1/5 in.) in length, depending on the instar. They are green in colour and darken as they mature. Typically the third instar stage has five black dorsal spots and is beginning to develop wing pads. Plant bugs have mouth parts that pierce and suck on plant juices. They feed on strawberry fruit and bloom. The injury is described as “catfacing” or “button berry”.

Often Confused With
Frost
Poor pollination (Plant bug injury can be distinguished by the size of the seeds. The seeds on fruit damaged by plant bugs are usually fully developed. Due to poor pollination, seeds are variable in size, smaller on the injured area of the fruit but fully developed on the undamaged tissue.)
Potato leafhoppers
Aphids

Biology
Tarnished plant bug adults emerge in the spring, feeding on new buds and shoots of rapidly growing plants including weeds and strawberries. They lay eggs on plant material once the temperature becomes 20°C (68°F) or higher. Depending on the temperature the nymphs will hatch in 7- 10 days. Nymphs generally emerge in mid May, feeding on the developing bloom and fruit. Adults and nymphs can both be present in a crop at the same time as a result of overlapping generations, having between three to five generations per year. From fall to winter only adults are present as they prepare to overwinter in dead weeds, leaf litter and under tree bark. Adults emerge in the spring when the temperature reaches 8°C (46°F) to start the life cycle over again.

These pests feed on the reproductive organs of the plants, probing the tissue repeatedly causing mechanical damage. Nymphs take a test bite to determine whether the plant is a good food source, if it is suitable it will continue puncturing and release digestive enzymes into the tissue. Feeding causes a number of problems including; fruit malformation, abnormal growth, cell death, abscission of fruiting structures and damage to seeds. As the fruit develops the seeds remain clustered together preventing normal development called apical seediness or cat facing. Generally berries are susceptible to apical seediness before seed separation.

Period of Activity
Overwintering plant bug adults move into strawberry plantings in early spring (April). Nymphs appear during strawberry bloom and are active through to the first harvest. There are several generations per year and all stages can be present throughout the summer.

Scouting Notes
Monitoring to identify nymphs is critical to reduce damage. The key symptoms of tarnished plant bug infestation are damaged fruit. It is important to control tarnished plant bugs before injury appears.

Look for tarnished plant bugs at first bloom (late May) through to the green fruit stage. Walk in a “W” pattern across a block. Tap the blossom clusters into a white tray or dish. Count the number of nymphs per 100 clusters.

A faster method that can be used when population are very low or very high is sequential sampling. For sequential sampling count the number of infested clusters, not the number of nymphs per cluster. The number of cluster samples depends on the population present. For very high or very low populations, fewer clusters can be examined before a decision can be made. For example, examine 20 clusters and note the number of clusters infested. If no clusters are infested, or 4- 5 clusters are infested, the population is below or above threshold, respectively, and sampling can be discontinued. If there are 1, 2 or 3 clusters infested, continue sampling and use the table below. Reassess after 25 clusters have been examined.

Thresholds
The threshold for control is approximately one nymph in four flower clusters in June bearing varieties. Thresholds might be different for day neutral varieties.

If using sequential sampling, refer to the table below for thresholds.

Number of clusters examined Number of flower clusters infested with TPB
Control not required Control required
2% Low threshold 4% Low threshold
15 0 3 or more 5 or more
20 0 4 or more 5 or more
25 1 or less 4 or more 6 or more
30 2 or less 4 or more 7 or more
35 3 or less 5 or more 7 or more
40 3 or less 5 or more 8 or more
45 4 or less 6 or more 9 or more
50 5 or less 6 or more 9 or more

Management Notes

  • Manage weeds in and around the plantings but do not mow or burn down weeds when strawberries are in the susceptible stage (bloom- green fruit).
  • Tarnished plant bugs are attracted to fast growing weeds and cover crops.
  • Strawberry fields near alfalfa and hay crops are at greater risk for plant bugs when these crops are mowed.
  • Both adults and nymphs feed on strawberry structures, but the nymphal stage causes the most economic damage, feeding on the achenes (seeds) and tissue of the strawberry fruit.
  • Generally:
    • 0.95 nymphs/ cluster = 13% injury
    • 0.25 nymphs/ cluster = 3.6% fruit injury
    • 0.15 nymphs/ cluster = 2% fruit injury