Fall pests in Delaware, 2026: what’s active right now

What to do about each one

Stink bugs: vacuum, don’t crush

They’ve been piling onto sunny south- and west-facing walls since September, and now they’re slipping in around windows and siding. Vacuum them up instead of crushing them.

• Vacuum them up; don’t crush them.
• Already seeing them? Seal gaps around windows, siding, vents and utility lines now to keep more out. Late summer, before they arrive, is the best time to do it.
• Repair torn window screens.

Read the stink bugs guide →

Boxelder bugs on sunny walls

Black-and-red bugs gather on sunny walls, porches and window frames in October, looking for cracks to spend the winter. They don’t bite, but squashed ones can stain fabric.

• Caulk around windows and add weather stripping around doors before fall.
• Vacuum bugs that get inside, then empty the vacuum bag.
• Hose clusters off walls with a strong spray of water; they’ll return if the spot stays warm.
• Clear piles of lumber, rocks and trash near the house.

Read the boxelder bugs guide →

Asian lady beetles: vacuum, don’t crush

Orange, spotted beetles cluster on sunny walls and windows in October and crawl into gaps to overwinter. Vacuum them instead of crushing them: crushed beetles stain and smell.

• Vacuum them up. For a bagless vacuum, rubber-band a knee-high nylon stocking inside the hose so the beetles collect in it, then remove the stocking right away and tie it off. For a bagged vacuum, take the bag out after each use and tape and discard it or freeze it so the beetles can’t crawl back out.
• Don’t crush or swat them. They release a foul-smelling, yellowish fluid that can stain walls, drapes and carpet. Penn State notes that people who are allergic to these beetles may not be able to vacuum them, because the vacuum exhaust spreads the odor.
• Seal gaps with good silicone or silicone-latex caulk around windows, doors, siding and utility pipes, and fix torn screens. Cover attic vents and exhaust fans with fine screen (20-mesh or smaller) and add door sweeps. Start in the rooms where the beetles show up most.

Read the Asian lady beetles guide →

Cluster flies at sunny windows

These slow, dark-gray flies moved into attics and walls in late summer. They wake on warm days and gather at sunny windows. They don’t breed indoors, so vacuum them and seal the gaps they come out of.

• Vacuum flies off windowsills and floors, then empty the canister into a sealed bag or an outdoor trash can so the dead flies don’t draw carpet beetles (Virginia Tech). Swatting works too, but a swatted fly can leave a greasy spot.
• Find where they come out inside, which is typically gaps around ceiling lights and exhaust fans, cracks behind baseboards, around window and door trim, and poorly fitting attic doors, and caulk those openings.
• Seal outside gaps now so next fall goes better: caulk cracks around windows, doors, siding, utility pipes and soffits, repair screens, and put fine screen over vents. Colorado State says sealing should be done by mid-August and certainly before Labor Day, so it is too late to keep this year’s flies out.

Read the cluster flies guide →

Mice and rats moving in

Cold nights push mice from the fields and woods into houses, garages and outbuildings, and a mouse can fit through a hole the size of a dime. Scratching in the walls, droppings and gnawed packaging are the first signs.

• Seal gaps around pipes and doors; a mouse fits through a hole the size of a dime.
• Store food, birdseed and pet food in sealed containers.
• Snap traps along walls work better than poison inside the home.

Read the mice & rats guide →

Deer ticks are still a risk

Adult deer (blacklegged) ticks are most active in late fall and winter, so ticks are still a risk after time in leaf litter and along wooded edges. Check yourself, kids and pets after time outdoors, and remove an attached tick with fine tweezers close to the skin.

• Keep grass short and clear leaf litter along wooded edges.
• Check yourself, kids and pets after time outdoors.
• Remove an attached tick with fine tweezers close to the skin; save it in a sealed bag.

Read the ticks guide →

Spotted lanternfly egg masses

Spotted lanternfly has been in Delaware since the late 2010s and favors tree-of-heaven, maples and grapevines. The Delaware Department of Agriculture asks residents to report and destroy them and to check vehicles before traveling.

• Squash nymphs and adults; scrape egg masses into alcohol.
• Check cars, trailers and firewood before leaving an infested area.
• Report sightings to the Delaware Department of Agriculture.

Read the spotted lanternfly guide →

Already seeing stink bugs? Vacuum them up, seal gaps now to keep more out, and call a pro for an exterior visit. Doing the sealing in late summer, before they arrive, is the best defense next year.