Description
The tarnished plant bug is one of the most damaging of the true bugs. Over half of the cultivated plant species in the United States are host plants for Lygus, which is found across the continental United States. This 5mm long bug is brown to tan to green with darker markings on the wings and back. Nymphs are bright green. Both adults and nymphs feed on plant tissue with piercing sucking mouthparts, usually new growth and newly formed fruits. During feeding they secrete a toxic substance which kills plant cells, resulting in brown spots or misshapen fruit. Terminal shoots and flowers may be killed.
Target Crops
Lygus feeds on a variety of herbaceous plants, vegetable crops, flowers, fruit trees and nursery stock. Soft fruits, berries and orchard fruit are also susceptible. Organic crops grown for seed are particularly challenged by this pest. Lygus also feeds on conifer seedlings.
Life Cycle
During the winter adults find shelter in dead weeds, leaf litter, under tree bark and in rock piles. In early spring they emerge to feed on developing buds and fruit. This can kill buds or exhibit as scabs, dimples or misshapen fruit. Leaves can be ragged or discolored.
The females lay eggs in leaf petioles or leaf blades and the eggs hatch after 7-10 days and yellow-green nymphs emerge. There are 5 nymphal stages over 3-4 weeks. The tarnished plant bug can have 2-3 generations per year.
Beneficial Insect Control
Orius insidiosus, the minute pirate bug, is a generalist feeder and will prey on nymphs. Release .05 to .1/square foot, weekly as needed.
Green lacewing larvae are also generalist feeders for nymphal stages. Release 1-5 larvae/square foot on hot spots and 1/square foot elsewhere, weekly as needed.
Another natural enemy of Lygus is a parasitic wasp (Peristenus digoneutis ) which is not commercially available. It was released for control of Lygus in alfalfa in New Jersey and has spread throughout the Northeast. It can cause up to 50% mortality, but it currently does not reduce the numbers sufficiently to prevent damage in key crops. Common predators, such as ladybeetles, spined soldier bugs and insidious flower bugs also prey on nymphs. (UMass Extension)
Insecticide Options
Use in rotation for best results.
Azadiractin or neem oils act as insect growth regulators, antifeedants and ovipositional deterrents. These include Azaguard and Molt-X.
Mycoinsecticides containing entomopathogenic fungal spores. These include Botanigard, Mycotrol, NoFly, Bioceres and PFR 97.
Oils and soaps can be effective. Circadian Sunrise is a corn/peppermint oil that suffocates insects. M-Pede insecticidal soap and Suffoil-X are more options
Grandevo is a broad spectrum bioinsecticide containing Chromobacterium labeled to target Lygus.
For a quick knockdown, use Pyganic with Pyrethrin for an organic adulticide. Surround WP is another option. This contains kaolin clay which acts as a mechanical barrier, irritant and disrupts the beetle’s ability to find host plants.
Cultural Control Tips
- Remove weeds around fields that can be host plants (wild carrots and other umbelliferous crops, redroot pigweed, lambsquarter, mustards, shepardspurse, rocket, goldenrod and mullein). Alfalfa is also a favored host along with vetch, lupine and fava beans.
- Remove plant debris in and around gardens and orchards to reduce overwintering adult populations.
- Use floating row covers over low-growing plants to provide a physical barrier.
- Monitor plants in early spring for wounds, discoloration, and malformations. Look for adults on fruits, flowers and foliage of susceptible crops.
- Use sticky traps to monitor for adults in spring.
- Avoid planting susceptible crops, such as strawberries, close to clover or alfalfa.
- Early seeding may help plants get past the vulnerable stage by the time Lygus numbers have increased.
References
Tarnished Plant Bug, UMass Amherst
Tarnished Plant Bug, University of Florida
Tarnished Plant Bug, University of New Hampshire
Find us at Sound Horticulture for specific regional recommendations.