Squash Bug on Vegetables

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.

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.

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

• Row cover 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.

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