Pest Control
Drive XLR8 Herbicide Crabgrass Killer: Spot-Treatment Guide
The Quinclorac Advantage: Why Drive XLR8 Works
When targeting large and smooth crabgrass (Digitaria sanguinalis and Digitaria ischaemum) in established turf, post-emergent control requires a herbicide that disrupts plant growth hormones while remaining safe for desirable grass species. Drive XLR8, manufactured by PBI-Gordon, utilizes a 73.0% concentration of quinclorac, a synthetic auxin herbicide. Unlike contact herbicides that only burn off foliage, quinclorac is systemic. It translocates through the phloem to the root zone, causing epinasty (uncontrolled twisting), stunting, and eventual necrosis of the crabgrass plant.
According to the University of Minnesota Extension, quinclorac remains one of the most effective post-emergent active ingredients for crabgrass control in cool-season lawns, particularly because it also suppresses broadleaf weeds like white clover and dandelion simultaneously.
Turfgrass Safety Matrix: Know Your Grass Before Spraying
Drive XLR8 is highly selective, but it is not universally safe for all turfgrasses. Applying quinclorac to sensitive warm-season grasses will result in severe chlorosis (yellowing) and stunting that can last for months. Review the safety matrix below before mixing your spot-treatment solution.
| Turfgrass Species | Safety Rating | Application Notes |
|---|---|---|
| Kentucky Bluegrass | Excellent | Fully tolerant at standard 0.75 fl oz/1,000 sq ft rates. |
| Tall Fescue | Excellent | Fully tolerant. May cause temporary tip burn in extreme heat. |
| Perennial Ryegrass | Good | Avoid applications during spring seedling establishment. |
| Bermudagrass | Good | Apply only when fully greened out. Avoid during spring green-up transition. |
| Zoysiagrass | Fair | May cause temporary yellowing. Test a small area first. |
| St. Augustinegrass | DO NOT USE | Severe injury, necrosis, and long-term stunting will occur. |
| Centipedegrass | DO NOT USE | Highly sensitive to quinclorac; will kill or severely damage turf. |
| Bahiagrass | DO NOT USE | Causes severe chlorosis and growth inhibition. |
Step-by-Step Spot Treatment Protocol
CRITICAL REQUIREMENT: Drive XLR8 must be mixed with a high-quality adjuvant. Without a non-ionic surfactant (NIS) or methylated seed oil (MSO), the waxy cuticle of mature crabgrass will repel the water droplets, reducing efficacy by up to 60%. Use a premium surfactant like Prime Source DuoStick or a standard crop oil concentrate at 0.25% v/v (approx. 1 teaspoon per gallon of water).
Mixing Math for 1-Gallon Spot Sprayers
The broadcast label rate for Drive XLR8 is 0.75 fluid ounces per 1,000 square feet. When spot-treating with a standard 1-gallon pump sprayer, you are typically covering 250 to 300 square feet at a comfortable walking pace. Here is the exact mixing ratio for a 1-gallon tank targeting 250 sq ft:
- Calculate Herbicide Volume: 0.75 fl oz ÷ 4 = 0.1875 fl oz (approximately 5.5 mL or 1.1 teaspoons) of Drive XLR8.
- Add Surfactant: Add 1 teaspoon (5 mL) of non-ionic surfactant to the tank.
- Fill and Agitate: Fill the sprayer halfway with water, add the herbicide and surfactant, then fill to the 1-gallon line. Shake vigorously for 10 seconds to ensure a uniform emulsion.
- Calibrate Output: Spray a 10x10 ft test area (100 sq ft) on a concrete driveway to measure how many pump strokes or seconds it takes to empty the tank, ensuring you aren't over-applying.
At current market pricing (approximately $75 per 1-liter bottle), a 1-gallon spot treatment mixture costs roughly $0.47 in chemical costs, making it highly economical for localized infestations compared to granular weed-and-feed products.
The 2-Tiller Problem: Managing Mature Crabgrass
Timing is the most common point of failure for DIY herbicide applications. Crabgrass susceptibility to quinclorac drops significantly as the plant matures. Penn State Extension notes that crabgrass is most vulnerable when it has 1 to 2 tillers (side shoots).
"Once crabgrass reaches the 3- to 5-tiller stage or begins producing seedheads in late summer, a single application of quinclorac will rarely provide complete control. The plant's vascular system becomes too complex, and the herbicide fails to translocate fully to the crown and root mass."
The Sequential Application Strategy
If you are treating mature, multi-tiller crabgrass in July or August, you must plan for a sequential application:
- Application 1: Apply the standard 0.75 fl oz/1,000 sq ft rate with surfactant.
- Observation Period: Wait 14 to 21 days. You should see severe twisting, purpling, and stunting of the weed.
- Application 2: Apply a second identical dose to any surviving crabgrass clumps. This secondary dose pushes the systemic herbicide into the deep root crown, ensuring total necrosis before fall frost.
Troubleshooting Edge Cases and Application Failures
Even with perfect mixing, environmental factors can compromise Drive XLR8. Monitor these variables to avoid wasted product and turf damage:
- Temperature Restrictions: Do not apply when ambient temperatures exceed 85°F. High heat increases the vapor pressure of the herbicide, leading to volatility and drift that can damage nearby ornamental plants. It also induces phytotoxicity (leaf burn) in desirable cool-season turf.
- Mowing Windows: Do not mow for 2 days before and 2 days after application. Leaving maximum leaf tissue on the crabgrass ensures maximum herbicide absorption and translocation time.
- Rainfast Period: Drive XLR8 requires 1 hour to become rainfast. If a sudden thunderstorm washes the application off before the 60-minute mark, you must re-treat the area once the foliage dries.
- Drought Stress: If the lawn is experiencing severe drought, crabgrass closes its stomata to conserve water. Herbicide uptake halts. Irrigate the lawn deeply 24 hours before spraying to ensure the weeds are actively growing and translocating nutrients (and herbicide) to their roots.
Frequently Asked Questions
Can I mix Drive XLR8 with liquid fertilizer?
Yes, but with caution. Tank-mixing with liquid nitrogen (like 28% UAN) can act as a secondary adjuvant and speed up herbicide uptake. However, mixing with high-salt granular fertilizers dissolved in water can cause antagonistic effects, reducing the efficacy of the quinclorac. For spot treatments, stick to a dedicated non-ionic surfactant.
How long until I can reseed my lawn after using Drive XLR8?
Quinclorac has a relatively long soil residual. You must wait a minimum of 14 days before seeding or overseeding with most cool-season grasses. However, if you are planting fine fescues, it is highly recommended to wait 28 days to prevent seedling germination failure and root stunting.
