Click to enlarge.

Beginner

Scientific Name: Lygus lineolaris (Order: Heteroptera; Family: Miridae)

Identification

• Adults and nymphs can feed on the buds, blossoms and green fruit.
• Adults damage the skin of the fruit, giving drupelets a white and desiccated appearance.
• Adults measure about 6 mm in length and 2.5 mm in width, are grey- brown in colour, have a flattened appearance and a yellowish triangle on their back.
• Nymphs are smaller than the adults, oval or shield-shaped, bright green in colour and resemble aphids.
• Nymphs progress through five instars. The third to fifth instars have one to five dark spots on their back.

Often Confused With
Aphids
Potato Leafhopper
White Drupelet Disorder
Poor Pollination
Virus

Period of Activity
Adult bugs are active from late April and early May until the first heavy frost in fall. Nymphs begin to hatch in May and are present throughout the summer. Raspberry damage is most obvious once fruits begin to mature.

Scouting Notes
To determine if this bug is present, examine blossoms and fruit clusters across the field. Tap or shake at least 20 flowers or fruit clusters from different plants into a white tray or dish and record the number of nymphs after each tap. Adults are capable of flying off when disturbed, so this technique will only track nymphs. Use a sweep net to scout for adults in adjacent weedy areas or in the lower crop canopy. Different raspberry varieties should be sampled separately.

Thresholds
None established. If plant bug nymphs are abundant in the blossom-green fruit stage of raspberries, consider control options.

 

Advanced

Scientific Name: Lygus lineolaris (Order: Heteroptera; Family: Miridae)

Identification
The tarnished plant bug is a pest of many crops. Damage to raspberries is sometimes reported but not well documented. On raspberries, both adults and nymphs can feed on the buds, blossoms and green fruit by using their piercing-and-sucking mouthparts. As a result, drupelets fail to fully form and berries are deformed or crumbly. Damage by adults to ripe fruit is more common in the fall, on primocane fruiting varieties. In this case adults damage the skin of the fruit, giving drupelets a pale, white and desiccated appearance.

The adult bugs are grey- brown in colour and have a flattened appearance. They measure about 6 mm in length and 2.5 mm in width and can be identified by a characteristic yellowish triangle on their back.

The nymphs are smaller than the adults, oval or shield-shaped, bright green in colour and resemble aphids. Nymphs progress through five instars. The third to fifth instars have one to five dark spots on their back.

Often Confused With

Aphids
Tarnished plant bug nymphs and aphids can be similar in size and appearance. However, aphids have two tube-like projections, known as cornicles, projecting from their last abdominal segment. Aphids move slowly while tarnished plant bug nymphs are very active.

Potato Leafhopper
Potato leafhoppers are slender and wedge-shaped, while plant bug nymphs are oval or shield-shaped. Leafhopper nymphs are the only insect nymph that can scuttle sideways when provoked.

White Drupelet Disorder
White drupelet disorder occurs when excessive heat or bright sunlight leads to drupelets which are fully formed but remain white instead of turning red.  

Tarnished plant bug feeding can also cause drupelets to turn white on mature fruit. However, the fruit will have an overall crumbly appearance, while a fruit with white drupelet disorder is still succulent and unspoilt.

Poor Pollination
Although raspberry bloom is very attractive to bees and other pollinators, some circumstances can lead to poor pollination and poorly formed fruit. Poorly pollinated fruit will not develop sufficient drupelets and the fruit will be crumbly and misshapen. Tarnished plant bugs sometimes feed on drupelets giving fruit a similarly crumbly appearance, but the drupelets appear more desiccated, while poor pollination results in drupelets not forming in the first place.

Virus
Tarnished plant bug infestations and virus infections can be distinguished by looking at the pattern of injury in the field. Virus infection will occur on the same plants year after year, and all fruit on the plant is crumbly. Plant bug injury will be most severe near the edges of the field or in weedy areas. It should correlate to scouting records for plant bug in the bloom-green fruit stage and will vary in severity from year to year. Diagnostic kits at a diagnostic lab can be used to verify virus injury.

Biology
Tarnished plant bug adults overwinter in old plant debris and other organic matter that protects them from the cold temperatures. They re-emerge between April and May. The insect is active until the first heavy frost in fall. The adults seek actively growing plants, feeding and laying eggs on the growing points. Once the nymphs have hatched, they feed on the plant tissues through May and June. They moult into adults in June and July. This life cycle is repeated several times within one year, depending on the temperature. Both adults and nymphs are active in the summer, but by fall, only adults will be present.

Period of Activity
Adult bugs are active from late April and early May until the first heavy frost in fall. Nymphs begin to hatch in May and are present throughout the summer. Raspberry damage is most obvious once fruits begin to mature.

Scouting Notes
To determine if this bug is present, examine blossoms and fruit clusters across the field. Tap or shake at least 20 flowers or fruit clusters from different plants into a white tray or dish and record the number of nymphs after each tap. Adults are capable of flying off when disturbed, so this technique will only track nymphs. Use a sweep net to scout for adults in adjacent weedy areas or in the lower crop canopy. Different raspberry varieties should be sampled separately.

Thresholds
None established. If plant bug nymphs are abundant in the blossom-green fruit stage of raspberries, consider control options.

Management Notes

• Manage weeds in and around the plantings but do not mow or burn down weeds when raspberries are in the susceptible stage (bloom-green fruit).
• Tarnished plant bugs are attracted to fast growing weeds and cover crops. Raspberry fields near alfalfa and hay crops are at greater risk for plant bugs when these crops are mowed.
• Do not apply insecticides during bloom.