Whether you just laid new sod or you're working hard to keep your grass installed years ago green, pests are never a welcome site. Given their small stature, they themselves are rarely seen, but the damage they leave behind is noticeable and similar between each pest. Brown splotches, overall yard discoloration and chewed grass blades indicate an insect problem that insecticides will put an end to.
Identification of Common Pests
Armyworms and cutworms take on a wormlike appearance, typically brown or green, with an occasional stripe. Adult billbugs look like black weevils. White grubs and the larvae of black turfgrass ataenius have a curved appearance, with a white body and reddish-orange head. Only size and legs separate billbug larvae, white grubs and black turfgrass ataenius larvae. Billbug larvae are nearly 1/2 inch long without legs, while white grubs grow up to 1 1/2 inches with legs and black turfgrass ataenius larvae are only 1/3 inch long with legs. An adult black turfgrass ataenius looks like a black beetle, only about 1/5 inch long. Southern chinch bugs have blackish-purple or sometimes medium to dark-red bodies with wings, up to 1/2 inch long. Whitish-gray larvae nearly an inch in length indicate lawn moth larvae, while the adults look like a simple gray moth of the same size. True to their name, fiery skippers in the adult form are fire-orange butterflies, while their larvae take on a fattened appearance with a green or slightly pink body and reddish-black head.
Armyworms, cutworms, lawn moth larvae, southern chinch bugs and fiery skipper larvae aren't keen on moving, and soaking the soil they call home is the only way to persuade the bugs to reveal themselves. Add 2 tablespoons of a liquid dishwashing soap into a gallon of water and apply the mixture over 1 square foot of grass with a watering can. The aforementioned pests will rise to the top of the soil. For whitegrubs, billbugs and black turfgrass ataenius, dig up a small section of grass -- no larger than the size of your spade -- and inspect the roots for the pests.
A Number's Game
Pesticides are often harsh on your grass and environmentally unfriendly, so restricting the use of them unless your grass desperately needs their help is the best strategy. The University of California's Integrated Pest Management program suggests only using pesticides if you encounter the following number of pests within a given area: five armyworms or cutworms per square yard, one billbug or its larvae per square foot, 40 black turfgrass ataenius or their larvae per square foot, six white grubs per square foot, 15 lawn moths or their larvae per square yard and 135 southern chinch bugs per square yard. Unless the presence of firefly skippers exceeds 15 per square yard, and they're damaging your yard -- via chewing the grass and creating small splotches of browning grass -- there's no need to implement control methods to counter them. One square yard is nine square feet, so check your yard in multiple locations for the pests.
Bacillus thuringiensis, imidacloprid, azadirachtin and pyrethrin serve as the four primary insecticides effective against sod pests. Bacillus thuringiensis is by far the least harmful, but only works against armyworms and cutworms. When applied to the soil, the pests eat the bacterium and die within days. It's very effective against young armyworms and cutworms, but less so against mature ones. Azadirachtin is the second safest and kills armyworms, cutworms and lawn moth larvae. It's somewhat toxic to bees and harmful to aquatic life if washed into waterways. It serves as a growth disruptor, killing affected pests within a week. Pyrethrin is the second most harmful insecticide on the list, but kills southern chinch bugs, armyworms, cutworms, fiery skippers and lawn moths. It's somewhat toxic to honeybees and highly toxic to aquatic life. Imidacloprid takes the crown as the most toxic insecticide on the list, as it's extremely dangerous to both bees and natural predators of various insects. It slowly kills pests by first paralyzing them. White grubs, black turfgrass ataenius larvae and billbugs all fall victim to the insecticide. In addition to insecticides, parasitic nematodes also take care of many harmful pests.
- University of California Integrated Pest Management: Lawn Insects
- University of California Integrated Pest Management: Western Yellowstriped Armyworm Larva
- University of California Integrated Pest Management: Adult and Larval Hunting Billbugs
- University of California Integrated Pest Management: Two Northern Masked Chafer Larvae
- University of Minnesota Department of Entomology: Black Turfgrass Ataenius
- University of California Integrated Pest Management: Adult Southern Chinch Bugs
- University of California Integrated Pest Management: Larva of Lawn Moth, Tehama Bonifatella
- University of California Integrated Pest Management: Skipper Larva
- University of California Integrated Pest Management: Compare Risks of Pesticide Active Ingredients