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Tarnished Plant Bug

CROPS IMPACTED: Cotton, alfalfa, brambles, soybeans, strawberries



Family: Miridae

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About Tarnished Plant Bug

Reproduction and Life Cycle

The tarnished plant bug can have up to 5 different generations per year, depending on the climate they live in. This pest will overwinter in their adult form beneath leaf debris, tree bark, and stones. The adults will begin to surface near the end of April when temperatures start to warm up. They immediately begin to lay eggs in and among plant hosts, usually at the base of the leaf, in buds or in the petiole. Typically, the eggs are laid individually and take between 7 to 10 days to hatch. An adult will lay 1 to 3 eggs each day, varying anywhere from 30 to 120 eggs in total throughout an adults lifetime. When the nymph hatches it will go through 5 instars before they become a fully grown adult. Nymph development will occur when temperatures are above 50 degrees Fahrenheit, but will slow when temperatures reach 94 degrees or higher. Development of the tarnished plant bug from egg to adult can take as few as 25 days, or as many as 40. The adult population tends to be the worst in the beginning of May, and thus causes the greatest amount of damage. When there is more than one generation, peak population will also occur in the beginning of July, August, and September.

Tarnished Plant Bug Identification and Habitat


An adult is typically 6mm long with a flattened, oval appearance. They are a green-brown colour and have red-brown wing markings. An effective way to identify a tarnished plant bug is to look for a small triangle on their back directly below their head that has a yellow tip. This pest can be yellow with black spots, or they can be mostly black with small yellow marks. They also have long antennae that have 4 to 5 segments. The adults who overwinter will be a much darker colour then the adults born during the summer.

Their eggs take on a cream colour and are a tiny 1mm lengthwise, shaped as a flask. The flattened part of the egg faces the plants tissue surface and has a hole that the nymph will come through when it hatches. In the first stage, the nymph is typically yellow-green and the same size as the egg. Later on they become greener in colour, with either green, black, or yellow spots and they remain wingless. During the last 2 stages, they will develop a green head with one black spot on the abdomen and 4 on the chest. When they become a fully developed nymph, their length will be around 4mm and they will have wing pads.


The tarnished plant bug is a common pest throughout North America. It has been recorded eating almost 400 different plant varieties, including dozens that are economically important such as vegetable crops, flowers, fruit, young nursery plants, and herbs. They are especially found in places where there are a lot of weeds that go to seed, including meadows. Their population will tend to increase in areas where plants go to flower. The damage they cause is from sucking the plants sap with their piercing-sucking mouthparts, often from flowers, fruits, and buds. The beak of the tarnished plant bug has 3 or 4 segments and rises from the front of the head when needed, but is held under their body in-between their legs when they are not feeding. They are thought to have a digestive enzyme that they inject into the host plant in order to break down the plant tissues. To identify whether tarnished plant bugs have infested your crops, look for dead buds, damaged cells near where the pest would feed, scabbed or deformed fruit and vegetables, and seed damage. In weeds, you can use a sweep net to see if they are present. For crops where the sweep net would damage the plants, use a direct visual examination of the plants.

Tarnished Plant Bug Management and Control Methods

Cultural Control

To effectively control tarnished plant bug populations in your crops, use proper weed management practices. Plant bugs are attracted to flowers and buds, so make sure to pick or mow weeds before they enter this stage. Once this pest has entered your crop, management practices will depend on what growth stage the plant is in. It is advised to look for adults from April to early May; the adults will fly when disturbed. You can hang white sticky traps in your trees to catch them while in flight. Also, plan to destroy overwintering sites such as removing leaf debris so that fewer plant bugs will come back the next year. This pest also has several natural enemies, such as geocorids, navids, spiders, ladybird beetles, and parasitic wasps. However, it is important to note that while these other insects will help with the control of the tarnished plant bug population, they will not be completely effective in eradicating this pest.

Chemical Control

Chemical control can be tricky with this pest as no insecticides will affect the eggs while they rest inside the plant, and it cannot be applied to fruit trees for a long period of the growing season since pesticides should not be sprayed while the trees are blooming, which is when the tarnished plant bug would be the most attracted to the plant. Insecticidal soap can be used; however, since there is often more than 1 generation per year, the soap can damage the plant if used several times throughout the season. Chemical insecticides for the tarnished plant bug include malathion and carbaryl. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy. After applying insecticides, it is important to irrigate sprayed areas to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the insecticides concentration.

Latin / Alternative Tarnished Plant Bug Names

  • • Lygus lineolaris