It’s normal for lawns to turn yellow during a drought, but if your grass is turning yellow in patches in sunny areas, particularly near paved surfaces, it could be hairy chinch bugs (Blissus leucopterus hirtus) wreaking havoc. They proliferate as early as June during hot, dry weather. If the heatwave persists and no action is taken, patches of dead grass grow and can invade the whole lawn. The turf remains firmly attached to the ground, however, unlike grub damage, where the grass has lost its roots and is easily pulled up. Damage is similar to that caused by drought, but when the rain becomes abundant again at the end of summer, the grass does not green up again, as it is dead.
Hairy chinch bugs
Adult bugs are tiny (about 4 mm, 1/8” long). They are black with crossed wings on the back. Nymphs are about 1 mm long, wingless and have a reddish abdomen: they’re the most voracious! Hairy chinch bugs like dry places and hide in lawn thatch, where they bite and suck the collars of grass shoots, which turn yellow and dry out. They can be found in almost all lawns, but only cause damage when they are present in large numbers and the lawn is weakened by drought or other stress factors. Infestations generally occur on dry, sandy, acidic and over-fertilized soils.
How to Identify Their Presence?
Keep an eye on the symptoms to avoid major infestations: if you have patches of yellow grass that are getting larger, pull apart the blades of grass bordering the affected areas, close to the healthy grass, scrape the felt a little and you’ll soon see several tiny red or black insects with white cross-shaped wings appear. To find out for sure, you can use a metal can (coffee-can size) with the bottom removed: push it halfway into the lawn and fill it with soapy water. After ten minutes or so, the drowned bugs will float to the surface and be easy to count. If there are more than 10 in the can, it’s time to take action.
Control Chinch Bugs and Repair Damage
To kill bedbugs, flood infested areas and spray with a pyrethrin insecticidal soap applied two or three times every 4-5 days, keeping the area well moist. Treat infested areas from June until the end of August.
Once the bugs have been eliminated, it’s time to reseed the bald spots and cover them with a little compost or lawn soil. Get a seed mixture with endophytes: these are microscopic fungi that are present in certain grass species, notably perennial ryegrass and many fescues. Sods enriched with endophytes show greater stress tolerance and drought survival. Unfortunately, seeds do not survive for more than a year at room temperature.
- To avoid future infestations, you have two sustainable strategies. Modify the conditions that attract chinch bugs or change plants, since chinch bugs only attack grasses. Follow these recommendations as well:
- Keep the soil as moist as possible by cutting the grass high (8 cm or 3 in.).
- Use only natural fertilizers that release nitrogen slowly.
- Correct pH if too acidic (below 6.5).
- Sow grass varieties with endophytes.
- Sow other species in the lawn, such as clover, trefoil or thyme, which bugs won’t eat.
Replace turf with drought-tolerant groundcovers such as blood geranium, sedum, mouse-ears, moss phlox, Russian cypress, etc.