Insect Control for St. Augustine Grass

Keep your St. Augustine grass free of insects.

St. Augustine grass is a tropical species generally restricted to areas with a mild winter climate. Although it is tolerant of high summer temperatures, it requires supplemental irrigation in dry inland areas. Because St. Augustine grass can grow in a variety of soil types, is easily established from sod, requires only a moderate amount of maintenance and has few serious pests, it is an effective species for lawns.

Insect Problems

Several insect species can cause damage to St. Augustine grass. The most serious pest is the Southern lawn chinch bug. These bugs feed on the stems at the base of the leaves and cause irregular areas of brown grass. White grubs and ground pearls feed on the roots of St Augustine grass, resulting in patches of dead grass, especially in spring and summer. Heavy infestations of leaf-feeding sod webworms, armyworms and cutworms can result in turf defoliation.

Types of Insect Control

To control pests in St. Augustine grass, first reduce thatch, irrigate properly and use the right fertilizer. If these cultural controls do not eliminate the infestation, choose the insecticide with the least environmental impact. Control leaf-feeding insects with insecticides or biological worm control. White grubs are harder to control because they live below the soil. Drench the soil with insecticides to control these pests. Combat chinch bugs and ground pearls with insecticides.

Insecticide Time Frame

When you need to use insecticides to control pest infestations, the timing of the application is important. Bacillus thuringiensis, a microbial insecticide, kills caterpillars that feed on treated foliage. Apply this chemical in the evening during warm, dry weather. Spray thoroughly and reapply after seven to 10 days. Apply nematodes during the early part of the season to control grubs and caterpillars. Retreat after two weeks. Several insecticides are effective for up to two months. Reinfestation may require repeated applications.

Environmental Concerns

Insecticides like azadirachtin, pyrethrum and imidacloprid target specific organisms and are relatively safe for the environment. Bacillus thuringiensis and nematodes are also recommended because they have little effect on non-target organisms. Avoid broad-spectrum insecticides like carbaryl and pyrethroids because they may harm beneficial organisms. Organophosphates chlorpyrifos and diazinon have been linked to surface water pollution. Because chinch bugs can become insecticide-resistant, use chemicals only when natural enemies don't control the population.

Prevention

Proper maintenance of St. Augustine lawns may prevent an insect infestation, as a healthy lawn is more resistant to pests. Irrigate properly, reduce nitrogen fertilization and eliminate soggy areas. Mow St. Augustine grass to a height of 3 to 4 inches. Finally, remove excess thatch. This thick layer of dead roots, stems, rhizomes and stolons can prevent the insecticide from reaching the soil.

References

• Texas A&M University: St. Augustine Grass
• University of California: Lawn Insects
• University of California: How to Manage Pests
• University of Florida: Southern Chinch Bug Management on St. Augustinegrass