Using Guardian® Plus II to Manage Resistant Weeds and Nightshade

Weed resistance and quality-reducing weeds are two major problems that identity preserved (IP) soybean growers face. Harm Kelly, an IP producer near Dunnville, ON, is no different.

The Problem

IP soybean growers need to grow a clean crop. It’s especially important to control weeds like Eastern black nightshade. Not only do they reduce yield but they also cause serious problems at harvest. Eastern black nightshade has little berries that burst in the combine and cause staining on the soybean seeds. That staining can significantly reduce or eliminate the premium that IP soybean growers are counting on to make the extra management around IP soybeans pay.

Group-2 herbicides have been especially effective in IP soybeans. But with repeated use has come weed resistance. IP growers need to control weeds that reduce both yield and quality but they need to make sure they control the weeds with a herbicide that brings multiple modes of action to control the toughest weeds.

That’s the situation Harm Kelly faced. He wanted to protect his IP premiums but he also needed a herbicide that was a weed resistance beater. He also wanted to spread his risk by not putting all his eggs in one basket and spraying the same herbicide program across all his acres.

The Solution

“We had been doing one application of a post-emergent conventional herbicide in our IP beans but we like to spread our risk by having some fields sprayed with a pre-plant herbicide program,” says Kelly. “On those fields, Guardian® Plus II was often the only thing we needed to spray.”

Staining from Eastern black nightshade is often considered the biggest culprit for robbing IP soybeans of the chance to make grade. But another weed controlled by Guardian® Plus II, lamb’s-quarters, can also cause problems.

Lamb’s-quarters is still succulent at harvest and can cause a green cast on the soybeans. Growers can put their best foot forward to control lamb’s-quarters since the options are very limited after emergence. Even with the options that exist, most producers attack the problem too late and the population density of the weed creates problems.

If you are more concerned about Eastern black nightshade, Group 2 resistant redroot pigweed and common ragweed, then Guardian® Plus II is good option. The “Plus” refers to the addition of flumioxazin to Guardian® which adds a little heat to the mix so you’ll see faster, more visual kill on emerged weeds. It really helps take down large, tough-to-kill broadleaf weeds.

Paul Sullivan, a crop consultant in Eastern Ontario, also recommends Guardian® Plus II in no-till situations. “We were using Guardian® Plus II alone and coming back with Assure® II for grass control,” he says. “Guardian® Plus II has its place in situations where we are trying to get a different mode of action on pigweed and nightshade. We found that other products were weak on the mustard family so having the chlorimuron ethyl in Guardian® Plus II really picked up the mustard family activity. We now go with Guardian® Plus II.”

In the past, Kelly has had some fields with Group 2 resistant weeds, mostly pigweed. Guardian® Plus II brings multiple modes of action that help with Group-2 resistant weeds.

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