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How to identify it
- Adults are flat-backed and dark gray to grayish brown. UC IPM and Minnesota give 5/8 inch long (UC adds about a third as wide); UMass gives 0.5 to 0.75 inch.[1][2][5]
- The edges and underside of the abdomen have alternating orange or orange-brown stripes; turning a bug over helps confirm it.[1][2][6]
- Eggs are bronze to brick red, about 1/16 inch long, and laid in clusters on leaf undersides, often in the V between veins. Cluster sizes differ by source: about 20 (Minnesota, Illinois), 12 or more (Kentucky) and 15 to 40 (UC IPM).[1][2][3][7]
- Newly hatched nymphs have a light green body; Minnesota and Illinois describe their heads and legs as black, while Kentucky and Wisconsin describe them as red. Older nymphs turn light gray with black legs and are often dusted with a whitish or grainy gray powder.[2][7][3][6][1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Brown marmorated stink bug and other stink bugs | Stink bugs are wider and rounder; squash bugs have a more elongated body and rounded shoulders. In the garden, stink bugs aren't considered pests of cucurbits.[1][5] |
| Leaffooted bugs | Leaffooted bugs are narrower and brown, with leaf-like flaps on the hind legs, and they feed mostly on fruit and seeds of crops such as tomatoes and pomegranates.[8][1] |
Where it lives
A common garden pest from Minnesota and Kentucky to California; Minnesota usually sees one generation a year, while California can have 2 to 3.[1][2][3]
Biology and life cycle
Adults spend the winter under plant debris, rocks, boards, woodpiles and around buildings; Kentucky and UMass say it is the unmated adults that overwinter. They fly to cucurbit plants in late May and June to feed and mate.[2][3][5][1]
A single female can lay up to 250 eggs over several weeks, according to UMass. Hatch times differ by source: UMass and Minnesota give 7 to 10 days, UC IPM 5 to 10 days or 1 to 2 weeks, and Illinois and Kentucky 1 to 2 weeks.[5][2][1][7][3]
Nymphs pass through five stages. UC IPM and Minnesota give 4 to 6 weeks to reach adulthood, Kentucky 5 to 6 weeks, and Illinois about five weeks from egg to adult.[1][2][3][7]
Minnesota, Wisconsin and the Northeast usually see one generation a year, while California can have 2 to 3. Because egg laying stretches over weeks, all life stages overlap through the season.[2][6][5][1]
Adults and nymphs hide near the plant crown, under leaves and under dirt clods or fruit, and scatter quickly when disturbed. In fall, after the vines die, adults and nymphs cluster on squash fruits before adults leave for winter shelter; Minnesota says the nymphs die when temperatures drop to freezing.[1][2]
Damage and signs
- Feeding causes yellow speckles that turn brown; heavy feeding blocks water flow so runners wilt and turn black and brittle, a symptom called Anasa wilt.[1][2][5]
- Seedlings and young plants can be killed, while larger, sturdier plants tolerate more feeding. Zucchini, yellow summer squash and pumpkins are the most attractive and suffer most; UMass says watermelon, cucumber, muskmelon and butternut resist damage.[1][2][5][6]
- Squash bugs transmit the bacterium that causes cucurbit yellow vine disease, which yellows, wilts and kills watermelon, pumpkin, melon and squash. UMass says infected vines yellow within two to three days and usually collapse 10 to 14 days before the fruit matures.[3][1][5]
- Recent research renames the cause of cucurbit yellow vine disease as Serratia ureilytica and reports losses of up to 100% of a cucurbit crop. A 2025 study found that cucumber beetles can carry and transmit it too, and a New York field study found more squash bugs, and more disease, on squash and pumpkins (Cucurbita) than on melons, cucumbers or watermelon.[10][9]
- Feeding on fruit can scar it or make young fruit abort, and feeding wounds on fruit sitting on the ground can let in rot.[1][5][7]
- The wilting resembles bacterial wilt, a disease spread by cucumber beetles, but squash bug wilt comes from feeding, not infection.[1][5]
Health risk
Squash bugs injure only cucurbit plants; for people, the main annoyance is a disagreeable odor when they are crushed or disturbed.[1]
Control
Prevention
Use row covers where squash bugs have been a problem, removing them at bloom for pollination. Trellised vining types help, and tolerant varieties include butternut, Royal Acorn and Sweet Cheese.[1][5][6]
Where squash bugs are a steady problem, skip straw or hay mulch, which gives them shelter at night.[2][5][7]
Blue Hubbard squash planted around the edge can work as a trap crop that draws squash bugs away from the main planting, but the trap crop still has to be managed by crushing eggs or treating it.[2][5]
Sanitation
Remove old cucurbit vines and garden debris after harvest, and compost or till them under, to eliminate overwintering shelter.[1][2][6]
Traps and physical control
Check leaf undersides for egg masses and crush them as soon as you find them; watching for egg masses also helps time control for when nymphs hatch.[2][1][6]
Lay boards, newspaper or cardboard in the garden; bugs gather beneath overnight and can be collected and destroyed each morning.[1][2][7]
Biological control
Spiders, ground beetles, bigeyed bugs, lady beetles and a tachinid fly, Trichopoda pennipes, attack squash bugs. Wisconsin suggests leaving bugs that carry the fly's small white eggs; UMass notes the fly kills too slowly to prevent that season's damage but can reduce the next year's numbers.[1][6][5]
A tiny egg parasite wasp, Hadronotus pennsylvanicus, also attacks squash bug eggs. In Virginia, releasing it on organic farms raised egg parasitism to about 60% within two weeks.[12][11]
Pesticides
Sprays work best on freshly hatched nymphs; adults are much less susceptible. Insecticidal soap and neem oil affect only the smallest nymphs and need thorough coverage under leaves. A Virginia zucchini study found nymph numbers were the best predictor of lost yield.[1][2][6][11]
Plants are flowering when squash bugs are active, so protect pollinators: avoid more toxic products when possible and spray when bees are least active: Minnesota and UMass say late in the day when the flowers have closed, and Illinois says early morning or evening.[1][2][5][7]
Common questions
- What are the bronze eggs under my squash leaves?
- Clusters of shiny bronze to brick-red eggs on leaf undersides, often between the veins, are likely squash bug eggs; crush them.[1][2][3]
- Why are my squash plants wilting?
- Squash bug feeding can wilt runners or whole young plants; check the crown and leaf undersides for bugs. Bacterial wilt and squash vine borers cause similar symptoms; a borer leaves an entry hole in the stem with sawdust-like frass.[1][5]
- Do I need insecticide for squash bugs in a home garden?
- Usually not. Minnesota says insecticides normally aren't required, and UC IPM says more toxic products are unlikely to beat handpicking combined with softer sprays such as insecticidal soap.[2][1]
- How many egg masses mean it is time to act?
- Minnesota, UMass and Wisconsin use an average of one egg mass per plant as the treatment threshold in commercial plantings; in a home garden, Wisconsin says to deal with any egg masses and the nymphs that hatch from them.[2][5][6]
Sources
- University of California Statewide IPM Program, “Squash Bugs (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/squash-bugs/ (accessed 2026-11-11)
- University of Minnesota Extension, “Squash Bugs (reviewed 2026).” extension.umn.edu/yard-and-garden-insects/squash-bugs (accessed 2026-11-11)
- University of Kentucky Entomology, “ENTFACT-314: Squash Vine Borer and Squash Bug (revised January 2026).” entomology.ca.uky.edu/ef314 (accessed 2026-11-11)
- iNaturalist, “Anasa tristis taxon page (order and family).” www.inaturalist.org/taxa/143660 (accessed 2026-11-11)
- University of Massachusetts Amherst Extension, Center for Agriculture, Food, and the Environment, “Squash Bug (Vegetable fact sheet).” www.umass.edu/agriculture-food-environment/vegetable/fact-sheets/squash-bug (accessed 2026-11-11)
- University of Wisconsin-Madison Extension, Wisconsin Horticulture, “Squash Bug, Anasa tristis.” hort.extension.wisc.edu/articles/squash-bug-anasa-tristis/ (accessed 2026-11-11)
- University of Illinois Extension, “Squash Bug.” extension.illinois.edu/insects/squash-bug (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Leaffooted Bug, Publication 74168.” ipm.ucanr.edu/home-and-landscape/leaffooted-bug/ (accessed 2026-11-11)
- Plant Disease, via PubMed, “Rodriguez-Herrera K, Nelson EM, Day CTC, Nault B, Smart CD (2026), Squash bug host preference is associated with cucurbit yellow vine disease incidence across cucurbit species, Plant Disease.” pubmed.ncbi.nlm.nih.gov/42963872/ (accessed 2026-11-11). Cited from the PubMed abstract.
- Phytopathology, via PubMed, “Mphande K, LaSarre B, Paulsen AA, Hartung R, Badilla-Arias S, Gleason ML, Beattie GA (2025), Bacteria that cause cucurbit yellow vine disease fall within the Serratia ureilytica species of the S. marcescens complex and can be vectored by cucumber beetles, Phytopathology.” pubmed.ncbi.nlm.nih.gov/39970138/ (accessed 2026-11-11). Cited from the PubMed abstract.
- Journal of Economic Entomology, via PubMed, “Boyle SM, Weber DC, Kuhar TP (2025), Nymphal abundance is best predictor of squash bug damage to zucchini, Journal of Economic Entomology.” pubmed.ncbi.nlm.nih.gov/40824223/ (accessed 2026-11-11). Cited from the PubMed abstract.
- Environmental Entomology, via PubMed, “Boyle SM, Salom S, Schultz P, Lopez L, Weber DC, Kuhar TP (2023), Augmentative biological control for squash bug using the egg parasitoid Hadronotus pennsylvanicus, Environmental Entomology.” pubmed.ncbi.nlm.nih.gov/37579059/ (accessed 2026-11-11). Cited from the PubMed abstract.