Flower/Herb Garden: Leaves

Plant Bugs

Plant bugs are small sucking insects (2-9mm) that feed on the leaves of many herbaceous plants. The plant bugs feed by piercing the leaves with their tube-shaped mouthparts, injecting an enzyme into the leaf tissue and sucking up the partially digested fluid. Damage to leaves may appear as stipples (tiny white spots), small round holes and distorted leaves.

The four-lined plant bug is a pest in the garden in May and June (one generation per year). The adults are 3/16 of an inch long and yellowish green with 4 black stripes down the back. The nymphs (immature bugs) are red with the yellow and black wing pads partially covering the body. This bug feeds on over 250 herbaceous plants. Damage from this plant bug begins as yellow stipples or spots, eventually becoming brown to black necrotic spots. In large infestations, these spots coalesce and cause leaves to turn brown. Four-lined plant bugs are quick and difficult to detect, and only a few can cause noticeable damage. Because they move so quickly, they are difficult to control with a contact insecticide such as insecticidal soap or horticultural oil. Many plants will outgrow the damage by mid-summer. Inexpensive annuals that have sustained heavy damage can be replaced when the bugs have finished feeding.

Tarnished plant bug is another bug that is commonly found feeding on plants in the garden. They feed on many fruits, vegetables and flowers. They inject a toxin into the plant tissue while feeding. Resulting damage includes deformed leaves, and damaged buds and flowers. The adult is ¼ inch long, flattened, oval, and irregularly mottled with white, yellow and black blotches. The blotches give it a generally tarnished appearance. There is a clear yellow triangle with a black dot on the lower third of each side of the insect. The nymphs (immature bugs) are very small, greenish yellow with 4 black dots on the thorax (mid section) and 1 on the abdomen. There are 3-5 generations per year, with feeding throughout the growing season. To help control these insects, remove unwanted weeds and garden trash which provide overwintering.

The harlequin bug is another pest of flowers and vegetables. The feeding damage appears as white stippling or spots on foliage of infested plants. They are particularly fond of crucifers such as ornamental kale and cabbage. They also feed on cleome and sunflower. The bugs are black with bright red markings, flat and about 3/8 of an inch long. The bugs lay their very distinctive eggs on the underside of leaves early garden crops. The eggs are tiny, white and barrel-shaped. When eggs are found, destroy them to prevent their hatching. To control the bugs, handpick or use insecticidal soap sprays.

Yucca plant bug is a pest of Yucca wherever it is grown. The leaves are stippled, have black fecal spots and eventually turn yellow. The adult bug is 1/8th inch long, stout, and blue-black with a reddish head and thorax. The nymphs (young plant bugs) are red and may be found in large numbers feeding on the leaves.

Occasionally boxelder bugs may damage herbaceous plants. They may feed on a variety of plants in years when populations are very high. Damage appears as spots on leaves and flowers. Milkweed bug is similar in appearance to boxelder bug, but feeds on Asclepias (milkweed).

Keywords: boxelder bug, milkweed bug, harlequin bug, tarnished plant bug, four-lined plant bug, plant bug

Back to top

Photo Gallery

Four-lined plant bugs and damage.

Adult tarnished plant bug.

Harlequin bug and damage.

Yucca plant bugs and damage.

Milkweed bug on asclepias (milkweed).

Boxelder bugs on hosta.

Back to top