Stink Bugs: How to Identify and Control them on Tomatoes

Stink bugs (sometimes called “shield bugs”) are pests that infest tomato plants and destroy fruit. There are more than 200 species in North America, all members of the pentatomidae insect family.

When threatened, these pests expel a repellent odor from their thoracic gland for which they are named. In short, they stink.

What does the stink bug look like?

Shape: shield-like
Color: most are variations of brown or green
Markings: different species can have yellow, red, or pink markings
Size: about ½ inch long

What do they do to plants?

  • These pests insert their snouts underneath tomato skin. The enzyme they leave at the sting point turns that area of the tomato into liquid. The bug then drinks the liquid.
  • Sting points produce dark pinprick marks on the tomato.
  • Discolored areas appear on tomatoes where fluid is removed. They’re often white, yellowish or light green. Damage can appear knot-like.

When do they do their work?

Stink bugs are in their adult stage when they attack tomatoes.

How can you control stink bugs?

The best control measure is prevention (see below). Take other steps to keep these pests away from your tomatoes.

  • Control weeds. Excess foliage in the garden and adjacent areas provide perfect breeding habitats for the bugs. Keep your garden plot well-weeded beginning early in the season before the population matures. You'll to prevent them from taking up residence on your tomatoes. Continue to control weeds until harvest to keep bugs at bay.
  • Wash plants. When bugs first make an appearance in your tomato patch, spray tomato plants daily with water. The stream will force them off plants. You can also treat tomatoes with a 1-1 solution of water and vegetable oil, olive oil, or lavender oil applied with a garden sprayer to repel the insects. (See a good selection of garden sprayers here.)
  • Hand pick bugs. Remove them and drop them into a bucket of soapy water. You can place a tray beneath plant and shake it to collect bugs. Or use a hand vacuum to capture them.
  • Plant “trap crops” in an area around the tomato garden but set apart from the tomato plants. Trap crops are natural deterrents that draw stink bugs away from tomato plants and provide them with a thriving habitat. By planting abundant areas of small-flowered plants, you also encourage parasitic wasps, birds, and other predators that feed on the bugs. Stink bugs are known to be attracted to the color yellow. Mustard, millet, buckwheat, sorghum, sunflowers, marigolds, garlic, lavender, and chrysanthemums are good trap crops for these pests.
  • Use green treatment. Kaolin is a soft, white, silicate clay mineral combined with water and applied with a garden sprayer.After application, water evaporates leaving a protective powdery film. The coating acts as a physical barrier to insects, preventing pests from reaching tissue. Kaolin is natural and non-toxic. Treat tomato plants for two weeks before taking more drastic measures to control these insects.
  • Treat with insecticide.If the bugs continue to attack tomatoes after kaolin treatments, you may need to resort to insecticides like Sevin or Eight (Permethrin). But keep in mind that by doing so, you may kill helpful insects. Follow product instructions. 
  • What is the stink bug's life cycle?

    Our insect friend follows a typical three-stage metamorphosis: egg, nymph, and adult.

    • Adults lay eggs in early spring (March and April) on plant stems and undersides of leaves.
    • When hatched, nymphs move through 5 developmental stages over the course of 4-5 weeks.
    • Adults overwinter in garden debris and leaves, then lay eggs for the next cycle.

    How can you prevent them from infesting your tomato patch next season?

    • Keep weeds down. Stink bugs hide in dense foliage. By removing as many weeds and unnecessary garden foliage as possible during the growing season, you can take away places for them to live and hide.
    • Remove debris. After your last harvest, destroy weeds that could become an overwintering habitat for adult bugs. Remove and destroy affected plants at the end of the season.
    • Space plants. When setting out seedlings in the garden next spring, allow extra space in between tomato plants. Space gives extra circulation and provides fewer places for bugs to hide and grow.

    What else is important to know about these pests?

    • Stink bugs dislike heat and migrate from south to north when temperatures rise.
    • However, longer growing seasons in the south allow them to reproduce more frequently. That means infestations are longer in warmer regions. If winter is mild, adult bugs will continue to be active.
    • Bugs are attracted to light. They will hover around outdoor lights and even more indoors during summer evenings.

    Get more tips on our Tomato Pests Pinterest board.

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