University of Maryland Extension

Squash Bug - Vegetables

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Gray insects on squash

Squash bug with eggs
Squash bug adult and eggs - Anasa tristis


Appearance

  • Eggs: Shiny, elliptical, rubbery, bronze colored; in clusters of about 20 eggs.
  • Nymphs:  Newly hatched nymphs are pale green with black legs, and very gregarious. Five instars (growth stages) occur over about a month. Older nymphs are shades of gray in color and also have black legs.


Squash bug nymph
Video:  Dr. M. Raupp

  • Adults: Moderately large true bugs (have a triangular shaped thorax behind head) about 5/8" long, dark brownish gray in color. These gregarious bugs have piercing-sucking mouthparts and flattened bodies, with alternate light and dark markings around the edge of the abdomen.


Squash bug adult
Video: Dr. M. Raupp

squash bug eggs and nymphs
Squash bug eggs and newly hatched nymphs

Life Cycle/Habits

  • Squash bugs overwinter as adults under plant debris, soil clods, rocks, log piles, and buildings.
  • Adults become active around June and are secretive, hiding on plants or in mulch.
  • Numerous egg clusters are laid usually on leaf undersides, but occasionally on top of leaves, petioles, stems, flowers or fruit.
  • Nymphs are very gregarious and usually feed on shaded undersides of plants.
  • Adults are less gregarious but can be found congregating on plant stems at soil level.
  • Both nymphs and adults suck plant sap while secreting highly toxic saliva into the leaves, stems, or fruit.
  • Adults emit a foul odor when crushed. 
  • Two generations may occur in Maryland. 

Host Plants

  • All cucurbits, especially squash and pumpkin.  Also cantaloupe, cucumber, gourds, watermelon.

Signs/Symptoms

  • Squash bug feeding occurs primarily on leaves and stems, but may also occur on fruit.
  • Feeding on leaves produces small white dots, or stipples, and leaves will eventually appear tattered.
  • Large numbers of squash bugs will cause leaves to yellow and die.
  • Plant growth and yield can be significantly reduced. 
  • Feeding on fruit can produce localized wounds, which may introduce rot. 
  • Adult bugs may not be readily visible because they are highly secretive.
  • In mid-summer it is common to see eggs, nymphs, and adults all at the same time.

squash bug damaged leaf
Adults and nymphs suck leaf sap
leaving numerous small white dots,
known as stipples

Monitoring

  • Regularly turn over leaves to find egg clusters.
  • Young nymphs in dense clusters will be easily visible because of vivid red legs.
  • Watch for white stippling on leaves, followed by yellowing and browning foliage, and reduced plant vigor. 
  • Check base of stem and mulch for secretive, congregating adults.
  • Place boards nearby and check underneath periodically for hiding adults.

Prevention/Control

  • Floating row covers will prevent egg-laying on plants.
  • Egg clusters are difficult to hand crush, so tear out that portion of leaf and destroy. Nymphs can be hand-crushed or drowned in soapy water.
  • Neem, horticultural oil, and insecticidal soap are effective when sprayed directly on nymphs. Adults are very difficult to kill with the insecticides available to home gardeners.
  • Trap adults and nymphs by placing boards near host plants under which they will hide. Lift boards and destroy bugs in the morning.
  • Bugs also hide under mulch. When numbers are high, mulch may need to be removed.
  • Removing all plant debris at the end of the growing season is essential.
  • Check seed catalogs for cultivars of summer and winter squash that are resistant to squash bugs.


Video" Squash bug control

Additional Resources

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