Whiteflies in the Lawn?

When you walk across the garden, do whiteflies fly out of the grass? What are the whiteflies on my lawn?

Whiteflies in the Lawn

Whiteflies suffer from an identity crisis – they are probably not even flies – they are more likely to be the tiny, white/creamy/brown moths of the sod webworms. And it’s the webworms that are damaging your grass. However, other “real” whiteflies are known as leafhoppers, just to be massively confusing… They also attack grass, although not usually in large numbers. So we will look at each in turn.

There are different webworm species, but these underground caterpillars all feed on the grass – leaving you with a dry, brown dead looking area of lawn. In contrast, the real whiteflies suck the juices from the grass, and their larva eats from beneath. Look closely, and you may be able to see or small yellow dots on the blades of grass where they have been feeding.

Do Whiteflies Live in Grass?

Yes, whiteflies do live in grass, but it is not their favorite habitat. They prefer plants with succulent leaves and yellow flowers.

Whiteflies are white! They are easily confused with moths since their shape is similar. If you do find whiteflies in your grass, look around at your other plants since they have probably traveled from them – check especially the undersides of the leaves for the greyish/white eggs. They will likely damage your other plants more than your lawn. 

In addition, they secrete honeydew – a sooty mold – not damaging in itself, but it does prevent the sun from reaching the chlorophyll in the leaves and slows down their growth. It doesn’t look too great either!

Whiteflies develop rapidly in warm weather, and populations can build up quickly when natural enemies are ineffective and when weather and host plants favor outbreaks. One example you can see is reported here from April 2019. Check out the short video below which gives a good description of whiteflies.

St Augustine Grass Whiteflies

St Augustine grass forms a dense, low-growing lawn, green to bluish in color and reasonably resistant to pests – except for the sod webworm. The adult females lay their eggs on the blades of grass, and after about a week, the cream-colored larvae emerge and start to eat… and eat!

The caterpillars have black spots down their backs and grow to about ¾ inch long. They rest during the day on top of the soil – and become active at night, leaving irregularly shaped areas of brown grass or even bare ground. Sometimes you may see tiny silken webs that they spin. Fortunately, they do not feed on the roots, so the damage is not irreparable.

How Do You Get Rid of Whiteflies in Your Lawn?

Catch Them Early

When a cloud of whitish “flies” greets you when you walk on your lawn, it may be time to assess the state of things. You can make a drench yourself to flush out the caterpillars. Use 2-4 tablespoons of liquid soap mixed with one gallon of water and spray one square yard of grass evenly. Count how many caterpillars you see in 10 minutes, and if there are more than 15, think about treating your lawn.

Biological Pest Control

There are many natural whitefly predators, so it is important not to kill them off as well! Since the damage sod webworms do is usually not severe, be wary of overtreating. Even for leafhoppers, chemical treatment is not usually the best way forward since chemicals tend to kill off the whitefly predators. 

Bacillus thuringiensis

Bacillus thuringiensis is a bacterium that kills the moth larvae but does not harm beneficial insects, earthworms, pets, or people. When the caterpillar eats the treated grass, the bacteria poisons its digestive tract, and the pest stops eating. It dies within two or three days. Take care to follow the instructions – they vary! Even though it is safe, it can still irritate the eyes and skin, so wear long sleeves and long pants. 

Monterey B.t. - Biological Insecticide for Organic Gardening - 1 Pint Concentrate - Apply Using a Sprayer Following Mix Instructions has good reviews, is safe and works on lawns. You may find it best to repeat the application after a few days to mop any remaining caterpillars. Try to avoid spraying when rain is forecast – dry skies for a couple of days is best, and don’t water the grass for 48 hours. Once you dilute the spray, it will lose its effectiveness after 12 hours.

Outdoor Sticky Trap for Bugs

Sticky traps

The whiteflies like the color yellow, so yellow sticky traps will attract the true whiteflies, and you can place them around your lawn to trap flying insects. Check out 48 Pcs Fruit Fly Trap, Sticky Gnat Traps for Indoor and Outdoor, Insect Killer for Flying Plant Insect Such as Mosquitos, Aphids, Leafminers, Fungus Gnats.

Insecticidal soaps

Insecticidal soaps are effective and more environmentally friendly than insecticides. Safer 5118-6 Insect Killing Soap Concentrate - Insecticidal Soap for Plants - Kills Aphids, Whiteflies, Thrips, Spider Mites, and More - OMRI Listed for Organic Use makes a concentrate that uses potassium salts of fatty acids. The waxy coating on the body of soft-bodied insects gets weaker, the soapy product penetrates the bug’s flesh, and they die. You may need more than one application if the infestation is severe.

The bonus is that you can use this spray not only on your lawn but also on edible plants up to the day of harvest – but make sure you spray the undersides of the leaves, as here is where the true whitefly lays its eggs. 

Insecticides

Neem oil

Neem oil is a popular method of control for many species of insect. Environmentally friendly and safe for pets and children, it kills all stages of insect development – eggs, larvae, and adults. One easy-to-use example is this Bonide (BND022 - Ready to Use Neem Oil, Insect Pesticide for Organic Gardening (32 oz.) - 2 Pack.

The real whiteflies lay their eggs on the underside of the blades of grass. A good soak may dislodge many of them, but if the infestation is severe, then products that contain carbaryl are effective. There are granules such as the The Andersons DuoCide Professional-Grade Lawn Insect Control - Covers up to 9,000 sq ft (18 lb), which includes carbaryl plus bifenthrin, and once watered in kills many insects above and below the soil’s surface, or you might prefer a ready-made spray such as Bayer 4031982B Suspend SC 16oz, White. Both are long-lasting, effective insecticides to use when you need them.

Conclusion

Do you have whitefly infestation on your lawn or the much more common sod web worm? The webworm caterpillars live just below the surface and eat the grass at night – resulting in a rough, yellow, dry area of your lawn. The whiteflies are more likely to come from nearby plants.

There are various treatments – if you feel you need them. A good drenching with a hosepipe may be all that is required but remember that the true whitefly lays its eggs on the undersides of leaves and can be difficult to access.

Insecticidal soaps and neem oil are effective and safe treatments, and traps will catch the flying insects. If the infestation is severe, insecticides containing carbaryl work well, but you need to read and follow the instructions for safe use.

Q&A

Will dish soap kill whiteflies?

Dish soap will work but could be challenging to use on a lawn since you will need to make up a lot, but it is heavily diluted. Just 1-2% soap added to water may be sufficient, especially if your water is soft. 

At what temperature do whiteflies die?

An interesting question with our weather so changeable now! At 21 degrees Fahrenheit, it takes about 3 hours to kill 90% of whitefly adults, but 51 hours to kill 90% of whitefly nymphs (and even longer for eggs).

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