Minimizing Weed Control Costs in Field Corn

It is instinctive to want to minimize production costs, especially in years of low commodity prices. Reducing weed control costs is possible, but it requires a higher level of management to maintain weed control and crop yield. Keep in mind that herbicide costs are relatively small compared to the economic losses that can be caused by uncontrolled weeds. Simply switching to low cost herbicides will not work unless the herbicide addresses the spectrum of weeds in a field, or is combined with other weed control tools, such as timely tillage.

Before altering your weed management program, ask yourself the following:

• How well do I know the weed infestations in my fields?
  • i.e. species, time of emergence, and density
• What programs have I used in the past and have they been successful?
• Am I able to cultivate, or apply herbicides in a timely fashion?

How do I develop a long-term, low cost weed management system?

I have chosen to focus on three low-risk management options that will aid in the quest for reduced weed control costs. Obviously there are other opportunities to cut cost (i.e. reduced rates), however these strategies come with much higher risk.

1. Scout fields and identify weed species, density and time of emergence.
   
   This seems pretty basic, but it is amazing how this information can provide you with the opportunity to lower weed control costs. For example, one field at the Woodstock Research Farm has a history of heavy lamb’s-quarters and pigweed pressure, with a very low amount barnyardgrass. Given this weed spectrum, in 2003, field corn was planted and we targeted the two broadleaf weeds with an early application of Marksman and then took a wait-and-see approach with the grasses. In this particular example, this saved us the price of a post-emergent grass herbicide (about $22/ac). If grasses had come up later, we still would have had the flexibility to go in with an appropriate grass herbicide or tillage.
   
   
2. Pick the most cost-effective weed management program
   
   Let’s be honest. Comparing the cost of herbicide programs is almost impossible because manufacturers will offer numerous rebate programs based on the quantities of herbicide or seed purchased. I have attempted to provide you with lists of herbicides in different price ranges (before program rebates), and some of the pros and cons associated with each program (refer to “Low Cost Herbicide Programs For Field Corn – Strengths and Weaknesses”). Hopefully this provides you with some options that perhaps you haven’t considered before.

   Several other factors should be considered when selecting a herbicide program:
   

   • crop safety,
     
   • flexibility in application timing,
   • consistency in performance,
   • seed costs associated with herbicide (e.g. Roundup Ready Corn) and
   • rebate incentives – there not going away, so use them to your advantage.
     
     
3. Review past successes and failures.
   
   Attempting to reduce weed control costs may result in some successes and failures. It is important to learn equally from both. For example, I have been burned in the past by selecting a low cost herbicide program that provided great control of the annual weeds, but unfortunately perennials were present that I did not know of. This illustrates the importance of scouting and documentation.
   
   Alternatively, there have been fields where I applied the “Cadillac” of weed control programs, only to notice that in a small section were I didn’t have the spray boom turned on (I could call this my untreated check, but I’ll be honest - I screwed up!), the weed spectrum indicated that a lower cost program would have been as effective as the more expensive one. Bottom Line - know what you have and tailor a herbicide program accordingly.

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What about “Roundup Ready” Corn for reduced weed control costs?

From an input cost perspective, Roundup Ready corn is very competitive plus it offers exceptional weed control, crop safety and application flexibility (Table 1). However, it is important to manage this technology appropriately in terms of glyphosate resistant weeds or weed shifts. An overuse of any one herbicide program will eventually result in weed management challenges. Provided yield is comparable to conventional hybrids, Roundup Ready corn has a very nice fit in management systems that have forages or if one is growing “IP” and conventional soybeans in a rotation.

What does the above comparison tell us?

• Seed and Herbicide Costs are cheaper under the “Roundup Ready” system (before any program rebates).
• That the conventional system would need to generate 1.49 bu/ac more than the “Roundup Ready” corn system to off-set the additional seed and herbicide costs.

What doesn’t the above comparison tell us?

• Whether the above two hybrids yield the same. This is an important consideration that should be researched before deciding on a seed/herbicide system. In the above comparison, according to the 2004 Corn Hybrid Performance Trials corn yields between the two are comparable.

Related Links

• 2004 Corn Hybrid Performance Trials
• Glyphosate stewardship in Ontario

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