The Four Lined Plant Bug is a common garden pest found throughout much of the United States and Canada, specifically east of the Rocky Mountains. These insects, also known as Poecilocapsus lineatus, cause distinctive feeding damage on a wide range of plants, particularly those in the mint (Lamiaceae) and composite (Asteraceae) families.
Adult four-lined plant bugs are yellowish to yellowish-green in color and have four longitudinal black lines down their wing covers. Measuring about 1/2 inch long, they can sometimes be confused with striped cucumber beetles. The nymph stage of the insect is wingless and varies from bright yellow to red, with rows of black spots on its body.
These bugs feed on over 250 herbaceous plants, causing damage that initially appears as yellow stipples or spots. As the infestation worsens, the spots eventually turn brown to black, and in cases of large infestations, entire leaves may become brown. Although quick and difficult to detect, even a small number of four-lined plant bugs can cause noticeable damage to your garden plants.
Four Lined Plant Bug: Identification
The Four Lined Plant Bug (Poecilocapsus lineatus) is a small insect with a distinct appearance. The adults have:
- A greenish-yellow body, about 1/4 inch long
- Four black stripes running down the back
- Black antennae
- Yellow-green legs with black marks
Nymphs, or the younger stage of the bug, show slightly different features:
- Bright red color when they first hatch
- Black wing pads and black dots on their abdomen
- As they grow, the color changes to reddish-orange
- Wing pads become larger with a light-colored stripe on each1
Here is a comparison between adults and nymphs:
|Stage||Body Color||Stripes/Wing Pads||Legs|
|Adult||Greenish-yellow||4 black stripes||Yellow-green|
|Nymph (new)||Bright red||Black wing pads||Not applicable|
|Nymph (older)||Reddish-orange||Larger wing pads||Not applicable|
By learning to identify the Four Lined Plant Bug’s distinct physical traits and understanding their preferred habitat, gardeners and farmers can better detect and manage them, protecting their plants from potential damage.
Four Lined Plant Bug: Life Cycle
- Four Lined Plant Bug eggs hatch in late spring
- Eggs are laid in vertical slits along plant stems
Four Lined Plant Bug eggs are banana-shaped and overwinter inside the plant stems. As the leaves on plants begin to emerge, the eggs hatch in late spring. Females lay these eggs in two to three-inch vertical slits along the plant’s stem1.
- Reddish in color
- Feed on upper side of leaves
- Develop through five molts in 3-6 weeks
Nymphs are reddish and active, feeding on the upper side of leaves. In a period of three to six weeks, they undergo five molts, developing and growing more as they feed on new shoots2. Nymphs also have black spots and lack wing pads, making them easy to identify.
- Yellowish-green with four black lines
- Feed on plants and then mate
- One generation per year
Adult four lined plant bugs are around 1/2 inch long and have a yellowish-green color, with four longitudinal black lines on their wing covers. After feeding for about a month, adults mate, thus completing their life cycle3. In general, there is only one generation of four lined plant bugs per year.
Host Plants and Damage
The Fourlined Plant Bug is known to feed on numerous plant species, primarily including:
- Herbaceous plants: such as mint, basil, and other herbs
- Ornamentals: likegeranium, zinnia, and daisy
- Shrubs and trees: forsythia, viburnum, dogwood, and hydrangea
- Annuals and perennials: shasta daisy, hibiscus, dahlia, and lavender
These bugs typically affect a wide range of plants, including vegetables, herbs, and ornamentals. They can cause damage to leaves, plant stems, and overall growth, appearing as foliar spots or even wilting when left unchecked.
Signs of Damage
The Fourlined Plant Bug’s feeding damage is characterized by various symptoms:
- Translucent spots: 1/16 to 1/8 inch in diameter caused by the bug’s toxin
- Wilting: Damaged areas may become necrotic, leading to leaf wilting
Examples of damage may include discolored foliage (greenish-yellow with black dots) on mint and basil or spotted leaves and stems on ornamentals like geranium and zinnia.
|Affected Plant||Signs of Damage|
|Mint||Discolored foliage, translucent spots|
|Basil||Wilting, translucent spots|
|Geranium||Spotted leaves and stems|
|Zinnia||Spotted leaves and stems|
As the Fourlined Plant Bug is a pest that can cause significant damage to plants, it’s essential to remain vigilant in identifying and managing their presence in your garden. With proper care and attention, you can keep your plants healthy and thriving.
Feeding Mechanism and Impact on Plants
Four-lined plant bugs have piercing-sucking mouthparts. They use these mouthparts to feed on plant tissues by injecting their saliva into the plant and then sucking out the liquefied plant materials.
Due to this feeding behavior, plants lose chlorophyll, causing a distortion in their appearance. Moreover, it leads to the formation of dead plant tissue. The overall impact of Four-lined plant bugs on plants can be summarized as below:
- Loss of chlorophyll
- Distortion of plant appearance
- Formation of dead plant tissue
|Impact on Plants||Example|
|Loss of chlorophyll||Plants get a pale appearance and may lose their capacity for photosynthesis|
|Distortion||Leaves may become twisted, curled, or otherwise malformed|
|Dead plant tissue||Necrosis spots or areas of dead tissue may appear on leaves and stems|
In conclusion, the feeding mechanism of Four-lined plant bugs has a negative impact on plants, causing the loss of chlorophyll, distortion in plant appearance, and creating dead plant tissue. Educating yourself on the Four-lined plant bug can help you recognize and address any potential infestations in your garden.
Control and Management
Monitoring fourlined plant bugs is essential for timely intervention. Check your plants frequently in late spring, when these pests are most active. Their nymphs are red or reddish-orange with dark wing pads and black dots, while adults have yellowish-green bodies and black antennae, with four longitudinal black lines on their wings covers 1.
- Pros: Safe for most plants, effective on soft-bodied insects
- Cons: Alleged irritation to human skin, direct contact with insects required
- Pros: Environmentally friendly, safe for beneficial insects
- Cons: Potential for plant damage in high temperatures, may require multiple applications
- Pros: Organic solution, disrupts insect’s life cycle
- Cons: Less effective on adult insects, may cause mild stress to plants
Cultural and Mechanical Controls
Implement these cultural and mechanical control methods to manage fourlined plant bugs:
- Prune affected plants to remove damaged areas
- Use a strong spray of water to dislodge bugs from plants
- Regularly clean up garden debris to eliminate hiding places
Biological control of fourlined plant bugs relies on their natural predators, such as spiders and predatory insects like minute pirate bugs. Enhance your garden’s ability to attract these beneficial insects by:
- Planting a variety of flowering plants
- Avoiding excessive use of chemical pesticides
- Providing a suitable habitat for predators, like a pile of leaves or a small wood pile
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Four Lined Plant Bugs
Subject: Four Lined Plant Beetles, yellow & green
Location: Naperville, IL
July 1, 2013 6:21 pm
Happy July! It’s been a long time (I think) since you’ve had one of these four-lined plant beetles (Poecilocapus lineatus) depicted, and I’ve never seen them around my neck of the woods until this year. They’re munching on some hydrangea leaves, and I found this yellow one and this green one on the same leaf. They’re very pretty little pests. All the best to you!
Signature: Dori Eldridge
Thanks for the new submission, however we have a correction to make to your text. You have the scientific name correct, but your common name is not. This is a True Bug, not a Beetle. True Bugs have piercing/sucking mouthparts and they do not chew. The brown spotting on the leaves might be due to the feeding which involves sucking nutritious fluids from the plants. According to BugGuide: “nymphs and adults feed preferentially on members of the mint family (wild mint, catnip, peppermint, spearmint, hyssop, oregano) but will attack a variety of wild plants (thistle, dandelion, burdock, tansy, loosestrife, sumac) as well as cultivated flowers (carnation, geranium, chrysanthemum, snapdragon, phlox) and crops (alfalfa, ginger, currant, raspberry, cucumber, lettuce, pea, potato, radish, squash).” Hydrangeas are not mentioned as a food plant, but lists of food plants can often be incomplete. Thanks again for supplying us with excellent new images of some Four Lined Plant Bugs, Poecilocapsus lineatus.
It occurred to me after I sent these photos that these are not beetles at all, but rather, four-lined plant bugs, as in true bugs and hemipterans, not coleopterans. Sorry for the confusion; earlier today, I was watching a ladybird beetle larva molt into an adult, so I had beetles on the mind.
All the best,
Letter 2 – Four Lined Plant Bug
Subject: not sure of this bug
Location: Missouri, US
May 14, 2015 12:27 am
while pulling weeds I found this little fella
I honestly don’t even know where to begin with an identification
I cropped the first pic and the second I left the same for size comparison
This is a Four Lined Plant Bug, Poecilocapsus lineatus, and according to BugGuide: “nymphs and adults feed preferentially on members of the mint family (wild mint, catnip, peppermint, spearmint, hyssop, oregano) but will attack a variety of wild plants (thistle, dandelion, burdock, tansy, loosestrife, sumac) as well as cultivated flowers (carnation, geranium, chrysanthemum, snapdragon, phlox) and crops (alfalfa, ginger, currant, raspberry, cucumber, lettuce, pea, potato, radish, squash).”
Letter 3 – Four Lined Plant Bug: Adult and Nymph
Subject: Red bugs!
June 6, 2016 5:51 pm
Hi Bugman. Found these in my garden. June 6.. They are devouring my butterfly bush and asters. What are they?
You have both winged adults, and flightless, red nymphs of the Four Lined Plant Bug, Poecilocapsus lineatus. According to BugGuide: “nymphs and adults feed preferentially on members of the mint family (wild mint, catnip, peppermint, spearmint, hyssop, oregano) but will attack a variety of wild plants (thistle, dandelion, burdock, tansy, loosestrife, sumac) as well as cultivated flowers (carnation, geranium, chrysanthemum, snapdragon, phlox) and crops (alfalfa, ginger, currant, raspberry, cucumber, lettuce, pea, potato, radish, squash).”
Letter 4 – Immature True Bug may be Four Lined Plant Bugs
Subject: Red Beetle with black band at top of the body
Location: Minneapolis, MN
June 1, 2014 1:21 pm
Help! Can you IDENTIFY? My normally healthy rudbeckias are all shriveling up and I looked today and saw these on them and other plants which are also shriveling up – echinacea, lead plant, other daisy type plants etc. eating the leaves.. It’s springtime (June 1)
Signature: Thank You!
This is not a beetle. It is a True Bug in the suborder Heteroptera, but we have not had any luck determining a species for you. Nymphs can be very difficult to identify to the species level.