Chinch bugs
Blissus leucopterus & B. insularis
Tiny black-and-white bugs that drain a lawn dry in the hottest, sunniest part of it. The patch looks like drought and does not respond to water — that is the test.
How to know it
An adult is 4 mm long, black with white wings folded over the back and a black triangular mark on each. The nymphs are bright red to orange with a white band across the back, turning black as they grow. Part the grass at the edge of a dying patch on a hot afternoon and you will see them running on the soil surface.
What you'll see
- Irregular yellowing patches in the sunniest, driest part of the lawn — along a driveway, a south wall, a slope.
- Patches turning straw-brown and expanding outward through the hottest weeks.
- Grass that does not green up after watering, which is the key difference from drought.
- Insects visible at the boundary between green and dying grass, running when disturbed.
- A soapy-water flush or a coffee-can float bringing dozens of them to the surface.
Where it comes from
Adults overwinter in thatch and at the lawn edges, and lay in spring on grass crowns and stems. Two to three generations a year in most of the range, with damage peaking in July and August when the second generation is feeding. They insert a needle into the stem and take sap while injecting a toxin that blocks the plant water transport.
Hot, dry summers and sunny, thatchy, over-fertilized lawns. St. Augustine grass in the south and fine fescue and perennial ryegrass in the north suffer most. Shaded and irrigated lawns are largely passed over.
Dealing with it
- Confirm before treating: push a bottomless can into the soil at the patch edge, fill with water, and count what floats up in five minutes.
- Water the lawn deeply and regularly; damp turf both discourages them and helps the fungus that kills them.
- Dethatch, which removes their winter quarters and their daytime shelter.
- Apply an insecticidal soap drench or beneficial nematodes to the patch margins in midsummer while nymphs are small.
- Reseed dead areas in autumn with an endophyte-enhanced ryegrass or fescue.
Keeping it out
- Overseed with endophyte-enhanced turfgrass, which chinch bugs will not feed on — the single most effective measure.
- Keep thatch under a centimeter.
- Water deeply and infrequently rather than letting the sunny edge of the lawn bake.
- Feed moderately; a heavily nitrogen-fed lawn supports far more of them.
- Encourage big-eyed bugs and ground beetles, which are effective predators when not sprayed out.
What it goes for
Lawn grasses — St. Augustine, zoysia, fine fescue, perennial ryegrass and Kentucky bluegrass; also sweetcorn and other grasses.
Who hunts it for you
- Beneficial nematodesSteinernema & Heterorhabditis spp. Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
- Big-eyed bugGeocoris spp. A stubby 3 mm bug with enormous wrap-around eyes, working the soil surface and the low foliage for aphids, mites, thrips and insect eggs. It is the main natural check on chinch bugs in a lawn and it is killed outright by insecticide. Grow to recruit it: Calendula,Clover,Cosmos,Goldenrod,Sweet alyssum
See also
The Cottage Garden Companion — the gardener's bestiary at cottagegardencompanion.com