Is pre-seed glyphosate alone enough?

It's a question growers are asking as they think of the weeds that are just waiting for spring to flourish and outcompete crops. Changes in tillage practices and tighter crop rotations, have led to an increase in both winter annuals and spring emerging annuals competing with your crop for valuable moisture and nutrients in the spring.

Margins are tight, every decision you make needs to make a return on investment.

What is your weed spectrum?

Tough winter annuals - glyphosate alone is not enough

Winter annuals emerge late fall and overwinter as rosettes or 3-4 leaved seedlings, ready to go to seed and flourish the moment spring arrives, and ahead of your crop. These tough winter annuals will out-compete your crop for valuable moisture and nutrients.

To maximize the effectiveness of your weed control, first assess the level of these winter annual populations:

Seed early into clean fields with PrePass™ XC's hard hitting, long lasting 21-days of SoilActive™ control of winter annuals and broadleaf weeds in barley, oats, durum and spring wheat. Rainfast in 30 minutes, PrePass XC also works under variable weather conditions and application timing.

Remember, a long fall with good moisture can produce bigger winter annuals in denser populations. And in all conditions, when spring hits, winter annuals will grow faster and out-compete your crop for valuable nutrients.

Weeds that flush - glyphosate alone is not enough

Also watch for these weeds that flush in the fall and spring and out-compete crops for valuable nutrients and moisture:

Glyphosate misses key weeds

Controlling weeds prior to seeding has become standard practice for many growers. While pre-seed application offers real advantages, using glyphosate alone is not the best option for many weeds, including these:

On its own, glyphosate also does not alone provide fully effective control of some winter annual weeds and spring emerging annuals. "Cleavers in winter annual stage or emerging in the spring season, dandelion, narrow-leaved hawk's-beard, which is difficult to control in crop, and flixweed are all weeds you want to control early," explains Brian Wintonyk, agronomist with Dow AgroSciences. "In areas where spring moisture levels are high, they will regrow quickly as the soil warms up. Controlling these early emerging weeds prior to seeding is very important."

Another concern with applying glyphosate alone prior to seeding is that it contains just one active ingredient and works through one mode of action. Effective herbicide resistance management programs involve the use of products with multiple modes of action that deliver overlapping activity on the same weeds.

In addition, glyphosate alone will not control Roundup® Ready volunteer canola - a growing problem. "Controlling Roundup Ready volunteer canola will continue to be an emerging issue due to the 10 million acres now grown annually in western Canada," Wintonyk says. "Glyphosate alone will only kill emerged InVigor® and Clearfield® canola volunteers. Growers are better to use PrePass XC and control both flushing InVigor and Roundup Ready volunteers for 21 days."

PrePass™ XC from Dow AgroSciences is a highly effective pre-seed application option that delivers superior control of a wide range of early emerging winter annual and broadleaf weeds. It provides better control of winter annuals than glyphosate alone and controls all varieties of volunteer canola. As a multi-mode of action product, PrePass is also an effective resistance management tool.

Control ALL volunteer canola

Volunteer canola is problematic for four main reasons:

It's important to control all volunteer canola, and of course, glyphosate alone will not control Roundup® Ready volunteer canola.

PrePass™ XC from Dow AgroSciences is a highly effective pre-seed application option that delivers superior control of a wide range of early emerging winter annual and broadleaf weeds. It provides better control of winter annuals than glyphosate alone and controls all varieties of volunteer canola. As a multi-mode of action product, PrePass is also an effective resistance management tool.

Manage glyphosate resistance

Growers are right to be concerned about glyphosate resistance as more and more acres receive repeated applications. To manage glyphosate resistance it's important to not have repeated applications of glyphosate alone, as that is the fastest way of selecting and increasing resistant plants.

"Growers are much, much better off getting superior weed control of hard to control winter annuals and spring emerging annuals, all types of volunteer canola and broadleaf weeds for 21-days with one application of PrePass, than hoping for the best with a glyphosate application, or worse multiple glyphosate applications," advises Brian Wintonyk, agronomist with Dow AgroSciences. "With PrePass you can seed into clean fields and use its multi-mode of action as an effective resistance management tool."

When to suspect herbicide resistance:

  • Weed escapes in odd shaped patches.
  • Some labelled weeds are controlled while others are not.
  • Records show repeated use of the same herbicide or group of herbicides.
  • Escapes aren't attributable to environmental conditions or emergence after application.
  • The same herbicide or group failed in the same area of the field in the previous year.

It's important to control all volunteer canola, and of course, glyphosate alone will not control Roundup® Ready volunteer canola.

PrePass™ XC from Dow AgroSciences is a highly effective pre-seed application option that delivers superior control of a wide range of early emerging winter annual and broadleaf weeds. It provides better control of winter annuals than glyphosate alone and controls all varieties of volunteer canola. As a multi-mode of action product, PrePass is also an effective resistance management tool.

Protect your yield potential

Seed early into clean fields for higher yields

According to Manitoba Agriculture, Food and Rural Development (MAFRD) the majority of seeding date research conducted in Western Canada reports increased yields with early seeding.

Early seeding mid to late April or early May, depending on the year and the location, can maximize yields due to:

  • Better crop use of available moisture.
  • Crops get a head start on weeds.
  • Earlier flowering, resulting in less heat stress.
  • Crop growth is ahead of peak disease infections and insect infestations.
  • Earlier harvest, resulting in better harvesting conditions.

Typically earlier seeded cereals have higher, heavier grain quality and higher yields, provided they were seeded into a clean field. Early weed control is essential for top yields.

"With its 21-days SoilActive™ control and 30 minute rainfastness, PrePass™ XC allows growers to seed into a clean field, that's going to stay clean while the crop emerges and gets established," explains Brian Wintonyk, agronomist with Dow AgroSciences.

"It's a production advantage and a logistics advantage. With 21 day weed control accomplished growers can focus their management, time, equipment and labour on getting all the seed in the ground as early as possible."

PrePass™ XC from Dow AgroSciences is a highly effective pre-seed herbicide that delivers superior control of a wide range of early emerging winter annual and broadleaf weeds. It provides better control of winter annuals than glyphosate alone and controls all varieties of volunteer canola.

Reduce weed competition and yield losses

Wheat yield losses due to weed competition can primarily be attributed to a decrease in tillering. The actual weed density at which wheat yield losses occur is weed species and environment dependent. Generally, the greater the weed density the greater the yield losses (Figure 1).

Review these tables from Alberta Agriculture for an overview on the effects of wild buckwheat, wild mustard, hemp-nettle, lamb's quarters and other broadleaved and perennial weeds on wheat yields.