Diagnosing Brown Patches in Florida St. Augustine: Fungus, Grubs, or Chinch Bugs?

Identifying and Treating Irregular Dead Patches in St. Augustine Grass

Spreading, irregular brown areas in St. Augustine during hot, dry weather could be fungal disease, grub worms, or chinch bugs. Chemical treatments often worsen the problem by killing beneficial organisms.

Field Diagnosis

• Grubs: Dig a spade-depth sample. 6+ grubs per square foot indicates infestation. Milky Spore disease (organic) provides long-term control.
• Chinch bugs: Use a can with both ends removed, push into soil at patch edge, fill with water. Bugs float to surface.
• Fungus: Look for matted, "laid down" blades. Often follows prolonged leaf wetness from night watering.

Organic Treatment Protocol

1. Baking soda spray: ¼ cup per gallon water, saturate affected soil and foliage. Repeat as needed.
2. Corn gluten meal: Natural fungicide and pre-emergent weed control.
3. Sugar application: 1 lb per 250 sq ft feeds microbes that outcompete pathogens.
4. Deep, infrequent watering: Only when top 1–2 inches dry. Never water at night.
5. Plug planting: Fill bare spots with St. Augustine plugs once soil health improves.

Why Chemicals Fail

Insecticides and fungicides kill predators (toads, lizards, beneficial insects) that naturally control pests. They also destroy soil microbes that suppress disease. An organic program builds a resilient ecosystem where problems self-correct.

Transition to organics now—stop chemicals, apply sugar and compost tea, and monitor. The lawn will recover as soil biology rebounds.