Fourlined plant bugs
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- In most cases, fourlined plant bug feeding only affects the appearance of plants.
- Moderate to large populations of fourlined plant bugs can be destructive to plants, especially herbs.
- Ignore fourlined plant bugs when possible, especially if you have not seen much damage in recent years.
- You can use a pesticide if you wish to preserve the plants' appearance or protect edible plants.
Fourlined plant bugs can feed on about 250 species of plants and are most commonly seen on:
- Herbaceous perennials - chrysanthemum, Chinese lantern, liatris and shasta daisy
- Herbs - mint and basil
- Woody ornamentals - azalea, dogwood, forsythia, viburnum, amur maple and sumac
- Flowering annuals - zinnia and marigold
- Berries - currant and gooseberry
- Vegetables - peppers
How to identify fourlined bugs
Four-lined plant bug nymphs are bright red to orange in color.
- When they first hatch, they have black wing pads and dots on their abdomen.
- Later stages of the nymph have black wing pads with a yellow stripe on each.
- Eggs are usually laid in groups of six or more.
- The eggs live through the winter and hatch in late May or early June when new leaves on plants are also beginning to emerge.
- There is only one generation per year.
Adults are greenish-yellow with four black stripes running along the wings.
- The head is orange-brown and the legs are yellow-green.
Both nymphs and adults have piercing-sucking mouthparts.
Life cycle of fourlined plant bugs
Fourlined plant bug eggs hatch in late spring and nymphs begin feeding on the upper side of leaves. After feeding for about four weeks, the nymphs molt into adults.
Adults keep feeding and then mate. They lay banana shaped eggs in a two to three inch vertical slit (created by the adult bugs) along the plant’s stem.
Damage caused by fourlined plant bugs
Both adults and nymphs can injure plants. They feed by inserting their needle-like mouthparts into leaves and removing chlorophyll (green pigment that helps with food production).
- This feeding produces dark, round, sunken spots, about 1/16 to 1/8 inch wide.
- The spots may become clear and after several weeks, the damaged tissue drops out, leaving small holes.
- If feeding occurs on new growth, wilting may result.
- Feeding damage may be confused with damage from leaf spot diseases.
- Feeding leaves spots that are similar in size and shape.
- Fungal and bacterial diseases cause spots that are of different sizes, and have discolored outer margins.
How to protect your plants
Check for bugs in May and June
Look for insects or damage caused by them in late May and early June. Look carefully as four-lined plant bugs may drop to the ground or hide when disturbed.
Small to moderate numbers of four-lined plant bugs do not seriously harm plants. Usually, treatment is not necessary to protect the plants' health.
Remove damaged plants in the fall
Cut down host plants in the fall to remove eggs that may have been inserted into them. Be sure to bury or compost removed plant material or remove residues from the landscape area.
You can minimize plant injury, if you detect fourlined plant bug activity early.
Insecticidal soap can be effective against the immature nymphs. The product has to come in contact with insects and repeat treatments may be needed.
A variety of longer lasting pesticides are available:
Use them with caution as they are broad spectrum and can kill a variety of insects, including natural enemies.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Be sure that the vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.
Reviewed in 2018