Weed Free Period - Parrish and Heimbecker, Limited

Understanding the Critical Weed Free Period

In weed control, timing — is everything

Like so many aspects of agriculture, the difference between good results and great results for in-crop weed control often comes down to timing. “The critical weed free period” is a specific window in crop development when plants are most susceptible to weed competition for light, water and nutrients. Keeping crops free of weeds during this period can be crucial to maximizing yield potential at harvest.

Critical weed free periods

Each crop varies in its respective critical weed free timing:

  • Spring Cereals: 1 to 3 leaf stage
  • Winter Cereals: 500 to 1000 growing degree days with a base of 0°C
  • Canola and Oilseeds: emergence to 6 leaf
  • Corn: V3 to V8 (3 to 8 leaf stage)
  • Soybeans: v1 to v3 (1st to 3rd trifoliate)
  • Forages: 4 to 6 weeks after planting
  • Pulses: 2 to 6 leaf stage


Protecting your yield

To understand the risk, peas make an ideal example, as the crop is very sensitive to weed competition. The threat can start as early as a week after the crop emerges, which is earlier than many post-emergent herbicide applications. If early emerging weeds are not controlled, there is an increased risk of yield loss. The use of a pre-emergent or pre-seed herbicide can control competitive weeds and protect the crop during this vulnerable stage.

Plus, with higher commodity prices, the impact of poor weed management has an even bigger impact on your bottom line.  Protect your valuable crop out of the gates and capitalize on current market conditions.


Choosing the right pre-emergent herbicide

There are a number of herbicide choices that can be used to maintain the critical weed free period for each crop, including options that also offer residual control. Integrated weed management is an important part of maximizing your crop’s success, but with the right strategy, the right herbicide program and the right timing, effective control can be achieved and maintained.

Pre-emergent Herbicide Information

Visit your local retailer and talk to your P&H Representative for more information on the critical weed free period.

P&H is your top choice for effective herbicide strategies, and our team of experts is always ready to help you develop a customized approach that is right for your crop plan and growing conditions.