Target herbicide is a selective, post-emergence tool for managing broadleaf weeds in maize. Its application is part of an integrated weed management program, often used with other herbicides and cultural practices, to protect corn yield potential. By controlling emerged weeds, it reduces competition for water, nutrients, and sunlight during the crop’s early growth stages.
Active Ingredients and Mode of Action
This herbicide’s activity comes from two active ingredients: pyridate and clopyralid. Each compound uses a different biological pathway to affect weeds. This combined approach helps control a wider range of weeds and manage the development of herbicide resistance.
Pyridate is a photosystem II (PSII) inhibitor, classified under WSSA Group 6. It works by interrupting the electron transport chain within the chloroplasts of susceptible plants. By blocking a specific site, it prevents the plant from converting light energy into chemical energy. This leads to a rapid buildup of toxic molecules and eventual cell death.
Clopyralid operates as a synthetic auxin and is classified in WSSA Group 4. It mimics the natural growth hormones in broadleaf plants, causing uncontrolled and disorganized growth. This hormonal imbalance disrupts the plant’s vascular tissues, leading to twisted stems and cupped leaves. Because it targets a different biological process than pyridate, it effectively controls weeds that may be less susceptible to PSII inhibitors.
Spectrum of Weeds Controlled
The combination of pyridate and clopyralid provides reliable control over many broadleaf weeds, including some that are difficult to manage with other herbicides. Pyridate is effective on weeds like nightshade and orache, while clopyralid controls thistles and mayweeds. Other controlled species include:
- Common lambsquarters
- Velvetleaf
- Pigweed species
- Common ragweed
- Giant ragweed
- Cocklebur
It is important to recognize the product’s limitations. This herbicide does not control grass weeds. Some broadleaf weeds may only be suppressed if they are too large at the time of application. Weeds like pale persicaria and redshank have shown moderate resistance and may require a tank-mix partner for complete control.
Application Rates and Timing
Proper timing is determined by both the maize growth stage and the size of the target weeds. Applying the product outside the recommended window can reduce weed control and increase the risk of crop injury.
The optimal application window is when maize is between the V2 and V6 growth stages. For the most effective results, weeds should be actively growing and less than four inches tall. Delaying application allows weeds to compete with the crop for a longer period, which can reduce efficacy and potentially lower yield.
Application rates vary by product label, which should always be followed for specific recommendations. Apply the herbicide in 10 to 20 gallons of water per acre to ensure thorough foliage coverage. An approved adjuvant, like a crop oil concentrate (COC) or nonionic surfactant (NIS), is often required to improve absorption. The product label also provides guidance on tank-mixing compatibility with other pesticides.
Crop Rotational and Safety Guidelines
Careful planning for future crops is required due to the soil residual activity of clopyralid. This ingredient can persist in the soil and harm sensitive crops planted later. Mandatory rotational restrictions, or plant-back intervals, must be followed to prevent crop injury. These intervals vary depending on the next crop, soil type, and weather conditions.
Specific waiting periods exist before planting sensitive broadleaf crops like soybeans, alfalfa, or potatoes. The plant-back interval for some species can be 12 months or longer. A field bioassay, which involves planting a small test strip of the intended crop, may be recommended to confirm the herbicide has degraded to a safe level. Not following these guidelines can result in significant yield loss in the subsequent crop.
Applicators must follow safety protocols. Personal Protective Equipment (PPE), including chemical-resistant gloves, long-sleeved shirts, long pants, and protective eyewear, should be worn when handling the product. To protect the environment, avoid spray drift onto non-target areas like sensitive plants and water bodies. Thoroughly clean all spray equipment after use to prevent contamination of other crops.