Dicamba is a polarizing topic in the world of lawn and garden care, often praised for its effectiveness on tough weeds but scrutinized for its potential to damage desirable plants. When it comes to grass, the answer is not a simple yes or no; it depends entirely on the formulation, the timing, the rate of application, and the specific species of grass you are trying to protect. Understanding the science behind this herbicide and the conditions under which it becomes dangerous is essential for any land manager or homeowner.
Understanding Dicamba’s Mechanism of Action
To determine whether dicamba kills grass, you first have to understand how it works. This herbicide is a synthetic auxin, which means it mimics a natural plant hormone responsible for growth regulation. When applied correctly, it targets broadleaf weeds by causing them to grow too quickly, leading to distorted growth and death. However, grass plants process this hormone differently, which is why many common lawn grasses are naturally resistant to standard dicamba applications. The key variable is the "selectivity" of the product, which is engineered to favor grass cells over broadleaf cells.
Situations Where Dicamba Will Kill Grass
Despite the inherent resistance of grasses, dicamba can be indiscriminate if misused. The most common way dicamba kills grass is through physical damage or volatility drift. Volatility occurs when the herbicide turns into a gas and moves through the air, particularly in warm temperatures after application. This drift can land on nearby grass blades or young seedlings, disrupting their growth cycles. Additionally, using a product labeled only for ornamental shrubs on a lawn, or applying a lawn fertilizer containing dicamba to a stressed lawn during extreme heat or drought, will likely result in burned, yellowed, or dead grass.
Susceptibility in Young Grass
Not all grass life stages are created equal when it comes to chemical tolerance. Young grass seedlings have underdeveloped cellular structures and defense mechanisms compared to mature turf. If dicamba is applied to a newly seeded lawn or a lawn that has just been sodded, the chemical can easily overwhelm the fragile plants. This often results in stunted growth, patchy thinning, or complete loss of the new grass. Always ensure the lawn has fully matured and established before considering any application of products containing this chemical near the root zone.
The Role of Formulation and Grass Type
Not all products are created equal, and the specific dicamba formulation dictates its interaction with your lawn. For example, products like Banvel or Diablo are often used in agricultural settings for pastures and rangeland, where the target is broadleaf invaders growing among established grasses. In these scenarios, the grass is the intended backdrop, not the target. Conversely, lawn-specific products, such as Trimec, are designed to coexist with grass while killing dandelions and clover. Using a high-concentration agricultural product on a residential lawn is a surefire way to kill desirable turfgrass.
| Grass Type | Sensitivity Level |
|---|---|
| Bermuda (Established) | Low (Usually Resistant) |
| Kentucky Bluegrass | Moderate |
| St. Augustine | Moderate to High |
| Centipede | High (Use Extreme Caution) |
Symptoms of Dicamba Damage
If you suspect that dicamba has affected your lawn, the symptoms are usually visible within a few days to a week. The most common sign is twisted or cupped leaf growth, where the grass blades curl inward or contort unnaturally. You might also observe yellowing or chlorosis, particularly between the veins of the leaf, followed by browning and necrosis at the tips. Unlike fungal diseases that appear in circular patterns, damage from drift often appears in irregular shapes near the edges of treated areas or downwind.
Prevention and Recovery Strategies
Preventing the death of your grass requires vigilance and strict adherence to application guidelines. Always check the product label for turfgrass safety and note the specific grass types listed. Apply the chemical on cool, calm days to minimize vapor drift, and never apply if wind speeds are above 10 mph. If you are using dicamba for weed control in landscaping beds adjacent to grass, install a physical barrier or use a shield to protect the green tissue. If your grass does sustain damage, recovery is possible if the crown of the plant remains alive. Focus on deep watering, avoiding further stress, and allowing the grass to resprout naturally rather than applying a second chemical shock.
