Tarnished Plant Bug (Lygus lineolaris)
Identification: The tarnished plant bug (TPB) is a small (1/4”) bronze-colored insect with a triangular marking on its back. The adult form has long legs and long antennae and piercing and sucking mouthparts (like a mosquito). The immature stage, or nymph, is smaller and bright green, resembling an aphid, but much more active.
Damage: Both adults and nymphs feed on the developing flowers and fruit, sucking out plant juices with straw-like mouth-parts. Feeding releases digestive enzymes that causes cell death, distorted growth, and seed damage all of which result in misshapen fruit. This deformed fruit: typically “cat-faced” berries, also called nubbins or button berries is generally unmarketable. While both adults and immatures (nymphs) can be present during strawberry bloom, nymphs cause more damage since they are present in larger numbers.
Life Cycle: Overwintered tarnished plant bug (TPB) 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 daytime temperatures average in the mid 60°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 46°F to start the life cycle over again.
Scouting Notes: White sticky traps are available for monitoring tarnished plant bug adults. These traps are used as a indication of when plant bugs begin their activity in the spring and a relative indication of their abundance, not as an indication of when to control this insect as no thresholds have been established for this trap. Immature TPB (nymphs) are sampled by shaking flower trusses over a flat white surface. Thirty flower clusters should be sampled evenly from across the field (typically 6 clusters at 5 locations or 5 clusters at 6 locations). If 4 or more flower clusters are infested with nymphs (regardless of how many) a spray is recommended. A follow-up spray application may be made after bloom if TPB are still present in high numbers (check harvest interval before selecting material).
Table 1. Sequential sampling for tarnished plant bug in strawberry.
|NUMBER OF FLOWER CLUSTERS INFESTED|
|Number of Clusters Examined||Control Not Required||Keep Sampling||Control Required|
|Low threshold||High threshold*|
= 2% damage
= 4% damage
|15||0||0-3; check 5 more||3 or more||5 or more|
|20||0||0-4; check 5 more||4 or more||5 or more|
|25||1 or less||1-4; check 5 more||4 or more||6 or more|
|30||2 or less||2-4; check 5 more||4 or more||7 or more|
|35||3 or less||3-5; check 5 more||5 or more||7 or more|
|40||3 or less||3-5; check 5 more||5 or more||8 or more|
|45||4 or less||4-6; check 5 more||6 or more||9 or more|
|50||5 or less||5-6; check 5 more||6 or more||9 or more|
|*Primarily for processing fruit.|
Sequential Sampling: a time-saver. To save time, a sequential sampling plan may used to determine how many clusters should be sampled. By using Table 1 above, you can make a spray/no spray/keep looking decision by first examining a minimum of 15 clusters. If you find 0 TPB nymphs, you can stop and make a “no spray” decision. If you find more than 0 but less than 3, (or, between 1 and 5 if you are using a high threshold) you must continue sampling. If you find 3 or more TPB nymphs, control is required in order to avoid economic damage to your crop. If the maximum of 50 flower clusters are sampled and no decision is indicated, the grower should sample again in 1 or 2 days. This method allows scouts to spend less time monitoring in fields where populations are very low, or very high. More time is spent sampling fields where TPB populations are close to the threshold.
Management: Controlling weeds in and around the planting may reduce populations of this insect, but insecticide sprays may be necessary. If mowing around fields, do so after insecticides have been applied (to control migrating insects). See the New England Small Fruit Management Guide for recommended materials and timing. Do not apply insecticides during bloom.
This work was supported by the Crop Protection and Pest Management Extension Implementation Program, Grant No. 2014-70006-22579 from the USDA-National Institute of Food and Agriculture.