Successful weed management is a science and skill. To properly steward herbicides and avoid the negative repercussions of herbicide shortcuts or mismanagement, below are five herbicide best practices.
- Make the proper identification
The first step to weed management is correctly identifying weeds, including those visible and those that you anticipate seeing throughout the year. For example, correctly distinguishing between broadleaf and grassy weeds directly correlates to the type of herbicide class needed. As an example, phenoxy herbicides control broadleaves but have little to no effect on grasses, while a pre-emergent herbicide, such as pendimethalin, can be used to control grassy weeds and many broadleaf weeds at the same time with one product application.
Once you establish your target list of weeds, research each weed's lifecycle to determine which herbicide active ingredients will work best and whether a pre-emergent or post-emergent strategy is the correct approach.
Take the time to read and understand the herbicide product label. Applicators often overlook the label, which provides a wealth of information that will help achieve better weed control and avoid potentially harmful effects to non-targeted plants.
- Match your management and weed problem
LCOs should consider cultural techniques and management practices that support the health and growth of desirable turfgrass and alleviate weed competition and encroachment. When selecting an approach, weigh these basic herbicide considerations:
Pre-emergent weed control: Annual grasses and broadleaf weeds are best controlled with preemergent applications in early spring prior to weed seed germination. When the turf is well established, a number of preemergent herbicides can provide broad-spectrum seasonal weed control. The preventative approach to weed control is one of the most effective and least costly means of long-term weed management.
Post-emergent weed control: This strategy is generally more costly than preemergent programs. Many post-emergent herbicides can only be used on specific cool- or warm-season grasses. Do not assume your turfgrass is safe until you check the label. Applications should be made when weeds are small.
- Search for new solutions
Some LCOs mistakenly assume older herbicide chemistries are more affordable. New products often provide more control, more efficiently and at a comparable cost. Waiting a couple of years to search for new solutions and continuing to - go with what you know' is a strategy that can result in herbicide resistance and poor weed control.
LCOs can stay abreast of new products by routinely connecting with their local distributor representatives, manufacturer sales specialists and weed scientists, such as a university extension agent.
New herbicide chemistries offer professionals tools to improve weed activity and mode of action, as well as have enhanced formulations to address common application challenges. Technologies include slow-release granules and micro-encapsulated liquids, and quick absorption and rainfast liquids.
- Optimize your equipment
Before any application, make sure your application equipment - sprayers and spreaders - is in good working condition and properly calibrated. Proper droplet size and spreader reach are critical to achieving accurate coverage.
Spray equipment must maintain constant pressure and flow to allow an even distribution of chemicals throughout the entire application. Verify that the equipment is properly calibrated to distribute herbicide product at the labeled rate. Before conducting a calibration test, carefully check the spray tank and lines for leaks, the pressure regulator and flow meter for proper operation and spray tips for clogs or excessive wear.
If handheld and backpack sprayers are not functioning properly, check for corroded metal parts, clogged nozzles or damaged seals. Chemical solutions left in sprayers can cause corrosion that inhibits a product's effectiveness.
While generally simple machines, spreaders can trap-up and deliver poor product application. Applicators should check to ensure that the hopper is opening and closing properly, and that the product spreader is rotating freely. Then conduct a calibration test to ensure the spreader settings match labeled application rates.
- Mix products correctly
Tank mixing products is a great way to save application time and is generally a safe practice - if the applicator knows in advance that the products are compatible and can be mixed together without negating efficacy. The product label is the best place to determine product compatibility, and specific details about products that can and should not be mixed.
The most common tank mixing error is improper ordering of product types in the tank. The quick reference below is a proven sequence that helps prevent a congealed mess from forming in the bottom of your spray tank:
- Fill your tank at least half-full of water, then begin agitation before adding products.
- Add soluble products.
Add product types in this order:
- WP, DG, LF or DF formulations.
- S or L formulations.
- EC formulations.
- NIS, COC or MSO.
- Liquid fertilizers.
- Fill the tank full with water.
Weed control success relies primarily on the knowledge of the turfgrass professional. By investing time to plan and prepare upfront, professionals can achieve better weed control while maximizing the return on their herbicide investment.
