Grow It Eat It: Maryland's Food Gardening Network

Top Vegetable Pests - Squash Bug

Squash bug - Anasa tristis

(click on an image to enlarge)

How do you know?

Do you have squash bug or stink bug? Click here to tell the difference.

Adult with eggs

Eggs and nymphs

Video: Adult by Mike Raupp

Video: Nymph

Video: Control

Appearance Eggs: Shiny, elliptical, rubbery, bronze colored; in clusters of about 20 eggs.
Nymphs: Newly hatched nymphs are pale green with red legs, and very gregarious. Five instars (growth stages) occur over about a month. Older nymphs turn gray with black legs.
Adults: Moderately large true bugs (have a triangular shaped thorax behind head) about 5/8" long, dark brownish gray in color. These gregarious stink 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

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.

ShareThis

For more information, contact Jon Traunfeld

Last updated: 01/27/2012

		How do you know? Do you have squash bug or stink bug? Click here to tell the difference.
Adult with eggs	Eggs and nymphs

Video: Adult by Mike Raupp	Video: Nymph	Video: Control

Appearance	Eggs: Shiny, elliptical, rubbery, bronze colored; in clusters of about 20 eggs. Nymphs: Newly hatched nymphs are pale green with red legs, and very gregarious. Five instars (growth stages) occur over about a month. Older nymphs turn gray with black legs. Adults: Moderately large true bugs (have a triangular shaped thorax behind head) about 5/8" long, dark brownish gray in color. These gregarious stink 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	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.