Stop Squash Bugs — Starting With Where They Sleep

How to know it’s squash bug

The eggs are the most useful stage to learn, because they are laid in a pattern you can find deliberately rather than stumble on.

Adult:

Large and flattened, five-eighths of an inch long, usually dark gray to dark brown, with alternating orange and brown stripes along the edge of the abdomen.

Egg:

Oval, a sixteenth of an inch, yellowish to bronze, laid in small clusters of about 20 on the undersides of leaves — characteristically in the V where two veins meet, and sometimes on the stems.

Young nymph:

A light green abdomen with black head and legs, starting around a tenth of an inch.

Older nymph:

Progressively light gray then brownish-gray with black legs and antennae, up to about half an inch across five growth stages.

Behavior:

Both adults and nymphs hide under the leaves when disturbed and move quickly, which is why hand-picking alone rarely clears them.

The year it runs on

Generations: One generation a year, though some summers produce a partial second.

Where it spends the winter: As unmated adults tucked into sheltered places — under plant debris, around buildings, under rocks.

1. Spring: Overwintered adults come out and fly to growing cucurbit plants to feed and mate.
2. Early June onward: Females begin appearing in gardens and lay egg clusters through mid-summer.
3. About 10 days: Eggs hatch. On farms, where the timing is scouted deliberately, UMN puts hatch at seven to 10 days after laying.
4. Four to six weeks: Nymphs mature. Because the stages overlap, every life stage can be present at once through the season.
5. Fall: Adults and nymphs group together on the squash fruits once the vines die back. The adults move to shelter for winter; the nymphs die at freezing.

These are University of Minnesota Extension’s Minnesota dates. The instruction that travels is the scouting one: start looking for egg masses in July, and treat the freshly hatched nymphs, because both UMN’s garden and farm guidance agree that control works on nymphs and not on adults.

What the damage actually costs you

Squash bugs pierce and suck sap, so the damage reads as a plant losing its water supply rather than as chewed tissue.

• •Yellow spots on the leaves that eventually turn brown.
• •Wilting where feeding is heavy, because the flow of water and nutrients is disrupted.
• •Young seedlings and flowering plants failing outright — these are the two most vulnerable moments.

How much the plant can take: It depends entirely on plant size. UMN notes larger, sturdier plants are more tolerant of feeding damage while young plants may die of it, which is why the same number of bugs is an emergency in June and an annoyance in August. One thing does not scale away: the squash bug transmits yellow vine decline, a disease UMN describes as new to the region.

The move

Habitat first, then the egg stage. All from University of Minnesota Extension:

1. 1

   Crush the eggs — this is the whole game

   Females lay small clusters of about 20 oval, yellowish-to-bronze eggs on leaf undersides, especially in the V where veins meet, from early June through mid-summer. They hatch in about 10 days. Scouting the undersides and crushing what you find is the single habit that outperforms everything else, because treatment of any kind works best on freshly hatched nymphs.

2. 2

   Rethink the straw

   Where squash bugs are a consistent and severe problem, avoid straw mulches — they supply the extra night shelter the bugs seek. Remove plant debris during the growing season too, to cut down the places they hide during the day.

3. 3

   Trap them under a board overnight

   Lay boards or pieces of newspaper beside the plants. Squash bugs group underneath at night; collect and destroy them in the morning. Dropping adults and nymphs into a pail of soapy water works too, but only where a few plants are affected — they hide under the leaves and move quickly when disturbed.

4. 4

   Clean the bed out in fall

   Adults overwinter under plant debris, around buildings and under rocks. Cleaning up cucurbits and other plant matter in fall reduces the number of overwintering sites. This is the move that lowers next year’s population rather than this year’s — which is exactly why it gets skipped.

5. 5

   Where pressure is high, grow the tolerant types — and keep plants sturdy

   Studies have shown butternut and buttercup squash and sweet cheese pumpkins tolerate squash bug feeding better than other varieties. Note that is tolerance, not immunity: the bugs still arrive, the plant just carries the damage. Proper fertilization and watering do the same work, since larger, sturdier plants take feeding that kills young ones.

Source: University of Minnesota Extension. Squash bugs

The plants in this playbook