Some of the most formidable enemies in the garden are herbivorous omnivores as they don't rely on a single host. The tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois), is one such pest that is bothersome in gardens and can cause significant economic losses to commercial farmers and horticulturalists.
Plant bugs are a large, diverse order of insects that fall into either the Lygaeidae or Miridae families. The Miridae family, which includes the tarnished plant bug, comprises over 10,000 species, of which 2,000 are found in North America. TPBs feed on their distinctive, piercing, sucking mouthparts that insert themselves into plant tissues and inject their toxic saliva. The toxin kills plant cells near the feeding place and causes browning and scarring of the plants.
Tarnished plant bugs prefer to feed on parts of plants that have a high rate of cell division, such as buds or flowers. Their damage can lead to reduced vegetative growth, termination or deformation of young fruits and flowers and an overall inhibited development of the plant.
The geographic distribution of the tarnished plant bug is astounding because of its ability to fly long distances and its host flexibility. They have been found as far as Alaska and Newfoundland in the north and as far as Central and South America in the south.
Overview of tarnished plants
The tarnished plant bug infects a large number of plants. Source: Dendroica cerulea
Adult tarnished plant bugs are 1/4 inch long with flattened dark brown bodies and white or yellow markings along their backs and wings. Adults in summer are lighter in color than overwintered adults. Adult beetles have a distinct yellow V-shaped mark behind their head and yellow triangles on their wing tips. Tarnished eggs from plant bugs are cream-colored and curved with a flat edge, on which new nymphs emerge. Tarnished plant bugs go through five nymph stages starting with pale green nymphs that gradually develop to their adult size and color. Nymphs in the early stages of their five nymph stages can be mistaken for aphids, but they move much faster and have no corneas or backward-facing parts protruding from the aphid's abdomen.
Lygus bug life cycle
Plant bug nymphs are easy to recognize by their shape and color. Source: kengi2000
TPBs have three stages of development: eggs, nymphs, and adults. Depending on the climatic conditions, the tarnished plant bugs can have two to three generations per year. Their life cycle begins with the overwintered adults laying eggs in early spring. Tarnished nymphs from plant bugs hatch in five to seven days and when temperatures reach over 50 degrees Fahrenheit. Both adult bedbugs and nymphs feed on plant tissue, but those in the immature stage are particularly voracious and cause more extensive damage. Depending on temperature, humidity and daylight, their development can take as little as 12.5 days to 40 days to reach full adulthood. Adults begin laying eggs a few days after reaching maturity. Females can lay over 90 eggs on average, some even 140 in their lifetime.
Common living spaces
TPBs overwinter between leaf litter, clover, rubble, bark and wooded areas. In spring, these overwintered adults lay eggs in the plant tissue of stems or leaf veins, so that only a small part of the egg protrudes from the plant. During their main growing season in summer, they can be found on the tips of plants where they usually feed in an upright position. Adult beetles also have the ability to fly.
What do tarnished plant bugs eat?
An astounding 700 plant species have been identified as host plants for tarnished plant bugs, 130 of which are economically important species for agriculture and forestry. Vegetables and fruits affected include cotton, strawberries, asparagus, potatoes, beans, stone fruits, and carrots, to name a few. Cut flowers and nursery plants are also susceptible. Even conifer seedlings, such as loblolly pines, cannot escape the appetite of these pests. In addition to domesticated host plants, there are also many native plants, especially those with aster-like flowers, hosts. Tarnished plant bugs are early colonizers of meadows and weeds that have reached their prime.
How to fight tarnished plant bugs
Lygus lineolaris on a flower. Source: jwinfred
Tarnished plant bugs are mobile and general feeders that have developed resistance to many conventional pesticides. Continuous population monitoring and the use of integrated pest control techniques are required to keep the population under control.
Organic or chemical control
In the past, the tarnished plant bug was considered a secondary pest and treated with broad spectrum pesticides on large agricultural areas. In recent years, however, researchers have found that some TPB populations have developed resistance to commonly used pesticides such as pyrethroids, carbamates, and organophosphates. Unfortunately, many home-approved pesticides on the market are not effective against TPBs.
TPBs have many natural predators such as parasitic wasps and many other native and introduced predators. These biological control agents have been used in commercial operations and the USDA is researching new microbial biopesticides, such as entomopathogenic fungi, in response to the growing problem of pesticide resistance. Novel chemical control agents that act as insect growth regulators also hold promise for the future. More research is needed now to find effective and integrated use of chemical and biological control agents. However, minimizing the use of pesticides can promote the natural predation of TPBs.
Weed control is an essential component in controlling the population of tarnished plant bugs, especially since many weeds are hosts. Remove or mow weed areas near vulnerable fruit trees, strawberry plants, nurseries, etc. Also, avoid planting catch crops such as clover and alfalfa near these plants. The restriction of the winter habitat of TPBs can have a significant impact on their population in the following years.
Preventing tarnished plant bugs
Prevent plant bug population from growing by monitoring their numbers frequently. You can install white glue traps around your plants or tap plants over a tarp or plate to count the number of bugs to get an idea of their infestation density. Floating row covers can be an effective way to create a physical barrier and keep adult beetles from landing on plants to lay eggs. Be sure to remove the floating row covers when the flowers are in bloom to allow pollination. Early flowering and early maturing varieties also tend to be more successful in the presence of this pest.
frequently asked Questions
The Lygus beetle is a common sucking pest. Source: Gailhampshire
Q: Are tarnished plant bugs harmful?
A: Yes, tarnished plant bugs are harmful to over seven hundred species of plants, over a hundred of which have significant economic value as crops.
Q: What does the tarnished plant beetle do?
A: Tarnished plant bugs have stinging-sucking mouthparts that damage and feed on plant tissues. They are particularly attracted to young stem tissue and flower buds of plants, which leads to deformed vegetative growth.
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