Better Early Weed Control in Field Peas: It’s the First Few Weeks that Matter

Field peas have been steadily increasing their place in many prairie crop rotations over the last several years. The crop works well in many cereal-based systems, offers rotational and market advantages and has strong demand in many regions. However, with many pulse crops, weed pressure early in the season can be a challenge in pea fields.

Peas aren’t the most competitive crop early in the season and there are not a lot of effective in-crop herbicide options. The less competitive crop allows weeds to emerge and compete for moisture, nutrients and sunlight during a critical window of crop growth. If weeds are allowed to get ahead early, it can be difficult for the crop to recover.

Crop competition at its peak

The first 2-3 weeks after emergence are often referred to as the critical weed-free period. During this time, the crop is focused on establishing its root system, putting on its first leaves and setting the foundation for future yield. Weeds that emerge during this window directly compete with the crop for soil resources. Plant vigor can be reduced with even short periods of competition and these impacts are often seen later in the season as well.

A number of broadleaf species, such as kochia, volunteer canola, wild mustard and wild buckwheat are common concerns in field pea systems in Western Canada. These broadleaf weeds can emerge very quickly once conditions are suitable and they often have vigorous spring growth.

If early pressure is not managed, these species can outcompete young pea plants and create problems that last throughout the growing season.

The importance of a clean start 

Starting with a clean field is one of the most effective tools for supporting early crop development in peas. Pre-seed burnoff applications are a common tool to remove emerging weeds ahead of planting and reduce competition during the early growth stages. Growers also often include soil-applied herbicides for field peas in their early management program. When used at the right time and under the right conditions, these products remain active in the soil and control weeds at or shortly after emergence.

Soil active herbicides can be used to maintain cleaner fields earlier in the season while the crop is still establishing. The fewer weeds that emerge, the less competition young pea plants will face and the better the opportunity for the crop to establish evenly. Choosing the appropriate herbicide for field peas is a critical component of that process. Product selection should consider the weed spectrum present, the timing of weed emergence and the overall crop rotation plan.

Broadleaf and grass weeds can both be an issue

Pea production systems often face a combination of both broadleaf and grassy weeds. Species like wild oats, foxtails, and barnyard grass can also create issues alongside broadleaf species.

This is why most weed control programs are built to include multiple tools at different points throughout the season. First-in-season control measures focus on targeting emerged weeds and controlling flushes. Subsequent herbicides will control any escapes that missed the first pass or have emerged after the crop has been established.

Rotating among different crop protection methods within the program helps control broadleaf and grassy weeds. Layering these products can also help reduce reliance on a single herbicide group over time.

Steps to improve early weed control in field peas

A few practical adjustments during the early part of the season can help reduce weed pressure and give pea crops a better start.

• Remove weeds before seeding whenever possible: Volunteer canola, winter annuals and early-emerging kochia can already be established by the time seeding begins. Controlling those weeds ahead of planting prevents them from competing with peas during their most vulnerable growth stage.
  
• Use soil active solutions to manage early flushes: When conditions allow, pairing pre-seed herbicides with a soil active herbicide for field peas that provides residual activity can help control weeds as they germinate. This is particularly helpful in fields where broadleaf weeds tend to emerge in multiple flushes.
  
• Watch for problem species that emerge quickly: Wild mustard and wild buckwheat can establish rapidly in warm spring conditions. Early scouting after crop emergence helps identify these weeds before they reach stages that are harder to manage.
  
• Plan grass control ahead of time: Grass weeds such as wild oats or foxtails are easier to manage when in-crop timing is planned early. Building programs with the right crop protection products allows grassy weeds to be targeted while they are still small and actively growing.
  

Small decisions early in the season can make a noticeable difference in how competitive a pea crop becomes later in the year. Starting with fewer weeds in the field gives the crop greater access to moisture, nutrients, and sunlight during the critical first weeks of growth.