Chinch Bugs Infestation

Chinch Bug Infestations

Chinch bugs do the most harm in lawns that bake in full sun, especially during hot, dry stretches. As they feed, they draw sap out of the grass and leave behind saliva that interferes with the plant’s ability to move water. The blades yellow, then turn reddish brown and dry out, and the runners eventually die. To the eye, the result looks a lot like a lawn that missed its watering.

Damage usually shows up first beside driveways, sidewalks and patios, where pavement holds heat, and along other sunny, exposed edges. It begins as a few uneven, off-color spots. As the bugs move outward into healthy grass, those spots join into larger dead areas, often ringed by a band of yellowing grass where feeding is still going on.

Confirming Chinch Bugs Before You Treat

Several other problems look a lot like chinch bug damage, including drought stress, lawn diseases and sod webworm caterpillars, so it pays to confirm the cause first. One clue: chinch bug patches do not green back up after a good watering, and the damage keeps creeping outward.

Two simple checks:

• Look at the edge. On a warm, sunny afternoon, kneel where yellowing grass meets healthy green grass. Spread the blades and watch the soil surface and thatch for a minute or two. Small black adults and reddish nymphs scurry when exposed. Skip the middle of a dead patch, since the bugs have usually moved on to fresh grass.
• Float test. Push a large can with both ends removed a few inches into the soil at the edge of the damage, fill it with water and keep it topped up for several minutes. Chinch bugs float to the surface.

What sets the stage: St. Augustinegrass that gets heavy doses of quick-release nitrogen, is mowed too short, or has built up a thick thatch layer tends to have more trouble. Some varieties once considered resistant, such as Floratam, are now attacked in many areas because chinch bug populations adapted to them.

When to watch: damage most often appears during hot, dry spells from spring into fall. In South Florida, chinch bugs can stay active through the winter, so a spreading yellow patch in the cooler months is still worth a look. The chinch bug species page shows what the insects look like.