Pest Alert: Crabgrass in St. Augustine Grass Lawns

by | Dec 18, 2020 | Pest Alert

Mainscape is committed to maintaining your property at the highest level. Part of that commitment is proactive communication when challenges present themselves. We want to make you aware of the challenge we frequently encounter with crabgrass in St. Augustine grass, and what can be done to manage it.

Crabgrass commonly invades established stands of St. Augustine grass. It can grow undetected for a period of time and seem to appear suddenly as it grows above the height of the grass blades, creating a mat-like appearance. Crabgrass infestations become much more apparent after cold weather as the leaves suddenly turn orange- brown. This often causes alarm. From a distance, this symptom resembles irrigation deficiencies. Though it may appear so, crabgrass is rarely killed completely in most parts of Florida because temperatures don’t stay below freezing long enough (if at all) and frequent warm temperatures in between cold snaps allow regrowth. As a result, small infestations can enlarge over a number of years until some degree of renovation becomes necessary to achieve acceptable turf grass quality.

Crabgrass Management

A dense, healthy, properly fertilized, mowed and watered lawn provides the strongest defense against crabgrass and other weeds. Seeds germinate readily when thinning turf allows sunlight to reach the soil surface. Any deficiencies in the irrigation system that may result in weakened grass should be identified and corrected.

Herbicides labeled for crabgrass control severely injure or kill St. Augustine grass. The only solution for removing existing areas of established crabgrass is renovation. This process entails killing the crabgrass with a non-selective herbicide and re-sodding. Additionally, the use of pre-emergent herbicides can significantly reduce the number of seeds for crabgrass and other weeds that germinate and reduce subsequent infestations. Renovation of crabgrass areas as they develop along with purchasing our premium agronomic program (which includes pre-emergent herbicides) can help keep crabgrass populations to a minimum in St. Augustine grass turf.